LiPo Current limit for welding? - Page 1
Forum section: electronics / projects

author: Amper
author_rank: Frequent Contributor
timestamp: June 07, 2018, 07:30:28 pm
content: Hi!I have another high power question and hope some of you know more.I´m involved in rebuilding a "small" hydro power station that burned down about one year ago. Its supplied by a large pipeline of about 1km length and 140m height. The pipe is about 800mm in diameter and after 40 years of erosion, rusting and falling rocks the wall thickness will be around 5-10mm. Sadly from time to time there is rocks falling that are thick enough to puncture it and at the pressures of up to 14 atmospheres that´s not really acceptable. Not only for safety reasons, but it actually affects power output as 1l/s will equal very roughly 1kW of continuous power.The crux is, that its in the middle of the mountains and the path running aside the pipe is almost impossible to climb even by off road motorcycle or quad. Carrying equipment is very very tedious, walking up there without stuff is usually annoying enough even for modestly fit people. A company doing these things professionally will charge around 4000€ per spot that needs to be fixed, so that´s out of the question anyways since we are pretty good at welding ourselves.There is two options:Number one is a portable welder using an RC two stroke boxer around 8hp and a modified truck alternator. This can actually be bought, though for the material you get, 3000$ is a bit seep as well, someone did a reverse engineering/teardown video before and its more primitive than it sounds. Electronics involve a 555 and a bunsh of fets to just set the excitation of the alternators winding. I´m actually in favor of the alternator method, since its bulletproof, can sit without being cared for and carries enough juice in a few liters of fuel for a lot of welding. The downside however is that even though i have a quite decent machine shop at hand building ant testing will take weeks in the best case working next to studying and i really don´t have the time right now.Number two and the one i actually wanted to ask about would be to take two or more turnigy multistar batteries, (2pcs. 6s 12Ah 20C are laying around anyways) and make some sort of current limiting for them.The obvious way to go would be a buck, but considering i will have to draw about 250-300A fairly continuously at a voltage drop of around 5-10V will make this bulky and heavy, also a large engineering effort.My thoughts now were to just go for simple pwm. Aside a resistor its probably the most brute force way i could imagine, but will it work? I´m experienced with switching high loads in this magnitude, but what will the welding arc do? usually this sort of thing has a negative resistance to current correlation. I´m not sure what the battery will answer when i demand double its C rating at 50% duty. Is there capacitors that can buffer this kind of current while being light weight enough (500g-1kg)?What do you guys think of the idea? Is there any better way of doing it without the risk of a lipo burning in the forest??cheersA.

author: texaspyro
author_rank: Super Contributor
timestamp: June 08, 2018, 04:06:05 am
content: The old farmer's hack for welding is a car battery and coat hanger wire electrodes...Maxwell makes some super-capactor modules that do high currents. I have some 58F ones rated at 15V 1000 amps. They came out of a wind generator and were used in large banks to supply power to the blade orientation motors.I know a guy that welds with Turnigy Nanotech LIPOs rated for 90C...

author: Dubbie
author_rank: Unknown
timestamp: June 08, 2018, 05:21:49 am
content: Just pay a heli $500 to drop of a genny/welder combo.Thats going to much easier in the long run I can promise you.AND your welds will be decent.

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2018, 05:27:15 am
content: Yeah I wouldn't try to hack something together for welding a pipe like that, it seems like the sort of thing where you'd be required to have certified welders using proper equipment. Certainly a liquid fuel powered generator is going to give you a lot more run time than batteries.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 07:26:49 am
content: Sadly helicopters dont work like that in europe ; ) They are much much much more rare and expensive, also regulations to fly over natural reserves and these altitudes in the mountains are prohibiting.The welds will not be structural, its not about fixing it against bursting, so no certified welding is needed. Its purely for leak stopping. Trust me, we know what we do, this is not just hobby stuff. By experience having it done by "professionals" is even more risky, the last time they welded the steel pipe with stainless filler material. Just so you understand me better, the reason why it burned down is, that the 3 year old reactance compensation cabinet for the 700kVA generator was complete trash, built in France by legrand in france, because we were told by authorities that it had to be mad in the country. The large contactors stuck multiple times, the service company didn´t inform us, then at 500kW power it got into resonance and the too small and not ventilated capacitors exploded and set 1m³ transformer oil on fire.We are seriously sick of the work in that country, so "diy" is the only option from now on.Back to topic: One of my batteries will deliver about 250Wh, at 3kW that is 10 minutes for 2 of them. Not much, but it will be ok to buy some more batteries. I guess, i will not know it without trying...EDIT:I just found out, that lorch sells welders and battery packs. They deliver 700Wh and its supposed to be enough energy to use 12 3,2mm electrodes. The system is a bit pricy at 3000€ combined, but i think im not so far away with what i was planning.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 08, 2018, 08:58:56 am
content: You should think the C rating as what it actually is:It's the (reciprocal) of the shortest allowed discharge time from full to empty! 60C contintinuous rating means you are going to weld for one minute.(Of course, apply derating to poorly specified cell first, e.g., a "60C Turnigy" might actually be safe at 20C, but the principle is this):It's most likely that once you are out there in the wild and need to repair some pipes, it will take more than just a minute or two of active welding time. Hence, I guess that any "power" type of cell, 10C or 20C or 60C or 100C rated, is enough for the job. You need to think about the energy content to do the required job.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 09:12:43 am
content: Yes, the 60C was not my suggestionI have 6S 12Ah 20C, two in parallel will be loaded at 12.5C if the 300A will actually be at 22.2V, thats not even close to critical and since the welding voltage will be even lower the battery current will be more like 200-250A. It will give me about 10 minutes per set of batteries. Assuming i invest 150€ more i will have 20 minutes of welding at 3kW, that should be enough.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: June 08, 2018, 09:52:27 am
content: a limiter like this 1 ?https://www.eevblog.com/forum/projects/guesses-on-what-i-am-attempting-here/

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 10:07:39 am
content: This one is on my list as well, but for this application a spot welder is not quite the right choiceIm looking for a limited current of 200-300A continuously for minutes, not milliseconds ^^

author: langwadt
author_rank: Super Contributor
timestamp: June 08, 2018, 10:46:50 am
content: use more batteries in series so you can get a few hundred volts to feed an inverter welder?

author: 3roomlab
author_rank: Frequent Contributor
timestamp: June 08, 2018, 10:47:47 am
content: Quote from: Amper on June 08, 2018, 10:07:39 amah yes my bad, not spoti saw a fronius on youtube, 150A machine. 11kg. 10min weld 45min charge @ 90A. the vid seem to suggest lugging along a genset lol

author: Ian.M
author_rank: Super Contributor
timestamp: June 08, 2018, 11:25:12 am
content: It probably makes more sense to get three pack frames, and attach a suitcase generator and an inverter welder to two of them, and use the third to carry consumables, tools, a fire extinguisher and a 50m extension lead so the generator doesn't have to be moved frequently. Schlep it all up to the highest point that needs repair then work downwards, only relocating the generator when you run out of extension lead.If possible leave the equipment out overnight under a tarp so it only has to be carried up ONCE in any repair season. If security is an issue, chain heavy items to a tree or the penstock and only remove small items.It may be worth contacting any nearby army units for personnel that might be interested in taking on the initial equipment move to the top as a mountain ruck march.

author: Dubbie
author_rank: Unknown
timestamp: June 08, 2018, 12:01:46 pm
content: To be honest this whole scheme sounds like amateur hour. You need to reconnoiter the pipe first to decide exactly what needs doing. You then need angle grinders to prep for the repairs, replacement pipe sections for the parts that are damaged beyond repair. You need to make good welds, clean and prep the HAZ, and finish with a couple of coats of paint. This is work a professional can handle piece of cake with the correct tools. Just rent a professional pipe welder who will have all the appropriate gear for remote site work, drop him off with a heli and pick him up end of day. Sure it might cost you $3-4K, but it will be done once and done properly. I find it hard to believe that there isn’t budget for this, plant like that costs a lot to maintain. This should be small beans.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 12:30:04 pm
content: Well, its not about replacing sections. We are talking about a small puncture every year or two. Cutting if necessary will be done by torch and grinding is easily done by battery.Just to give you some perspective i attached photos of after the fire and of the state that the machinery is in at the moment. The pipe weld shown is what you get for 3000€ by a french company. Horrible weld done with the wrong filler material. I know my question and proposition doesn´t sound like i know what i´m doing, but consider that we as two people are doing the complete rebuild on our own, there is a lot of experience behind it, we do everything starting from planning, control programming over making the cabinets up to replacing the 7t generator and mounting it to the 1/100mm adjusted to the turbine. This is family business, we are not some contractor doing crappy work for someone else.Sadly helicopters and army are out of the question, for now. I know that that´s a different mentality in other countries, but in europe that´s "a little more" difficult

author: Dubbie
author_rank: Unknown
timestamp: June 08, 2018, 12:46:00 pm
content: Fair enough explanation Amper.

author: CopperCone
author_rank: Super Contributor
timestamp: June 08, 2018, 01:51:41 pm
content: Based on the condition of the pipe dont you think its time to replace infrastructure?Why risk doing steep elevation repairs of some erroded ass shit that will be connected to brand new equipment?Yousaid its unacceptable for saftey reasons, but fixing holes on already erroded pipe with thin sections has nothing to do with saftey, you are just moving heavy equipment into the mountains topatch holes.If youpatch a bunch of holes how does the integrity of the whole pipe improve??I am baffledI mean im imagining special forces guys doing welding hanging off ropes to try to maintain decrepit rotten pipe... Why??why not replace the pipe and build a easy to traverse pass near the pipe so emergency repairs can be performed without helicopters and acrobats lolUtilities are supposed to be reliable the whole situation sounds like a unfunded jokePutting a road or ramps would actually increase saftey. Replacing the pipe would improve reliability of the system and increase saftey.If a piece of the pipe busts off it can kill someone right? It should probobly be burried in gravel but w/eThat pipe you posted looks like scrap someone dropped in the woods not hydroelectric infrastructure lol my garden hose is maintained betterThen you can do something advanced like do a yearly inspection with a camera robot to find weak points

author: 3roomlab
author_rank: Frequent Contributor
timestamp: June 08, 2018, 02:07:35 pm
content: Quote from: Amper on June 07, 2018, 07:30:28 pmmaybe a couple of these? assuming it could allow sustained short circuiting?

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 02:07:40 pm
content: Because its not eroded. We do periodic checks on the thickness ultrasonically and as i said the thin spots are down to 5-10mm were large rocks have fallen on it. Thats to be considered normal maintaining on this kind of thing. Replacing will be due in some 10 years or so, but im not sure if you are aware of the cost/payoff on this kind of thing. Full pipe replacement will be not under a million bucks, which is a little steep for something that will run like this without problems.The "not only for safety reasons" in my initial post was not referring to rupturing and drowning a village. 14 Bars is not much for such a pipe, it cant rupture, it will just have more and more leaks if its not taken care of. Its a much more likely scenario that some day there will be a landslide taking a section with it, in that case the water will just run into the stream right next to it and we will have a loss in production.Rusty on the outside doesnt mean its a tin can.EDIT:@3roomlab: Yes, a switcher designed exactly for this would be the perfect solution, no doubt... Sadly i dont have the time for such a project atm...

author: dcarr
author_rank: Regular Contributor
timestamp: June 08, 2018, 03:49:06 pm
content: Is a gas weld out of the question? With small tanks it might not be too heavy and you could split up the load into multiple parts.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 03:55:39 pm
content: Actually that is my backup plan! The thing keeping me away from doing it like that right away is my lack of experience with it. We have the equipment, but i have never done it before.

author: CopperCone
author_rank: Super Contributor
timestamp: June 08, 2018, 04:11:10 pm
content: Idk from my knowledge of metals and paint its not great to have a buncha lychens, moss, plants etc growing on it, it will hide defects like cracks and damage that occurs priorbto plant growth.I noticed if i have such growths on metal it tends to rust more under them. Dont know what the chemical enviroment under moss and lichens is doing for the paint thoAnd i said erroded because you said the spread on pipe wall thickness is 5 mm between 5 to 10mm, thats pretty wavy. I would guess the original thickness was even greater. I dont know if i would tollerate a 50 percent change in thickness of pipe wall as reliableAlsodo not know how it effects turbulance

author: Nauris
author_rank: Regular Contributor
timestamp: June 08, 2018, 04:16:24 pm
content: Quote from: Amper on June 08, 2018, 12:30:04 pmOh, so you have a torch! Then you can forget all batteries and rc-alternators and whatnot and just weld with the torch! Just take some practice if you haven't before.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 04:28:36 pm
content: Yes of cause its not good for the metal, i agree 100%. The thing just is, its laying there for over four decades now, we operate it for the last 25 years. It was originally around 12mm, the thin spots are where there is debris falling on it, the reason is not rust. Punctures only happen by falling debris with pointy corners, a half ton boulder rolling down the mountainside from time to time will not crush the pipe, but it will cause leaks. Turbulence is a bit of a problem, but the pipe is around 800mm diameter and its running about 500l/s at full power, that means the water goes down at 1m/s. Flow resistance is annoying, but acceptable. An actual problem would be if there was large debris inside, that could block the nozzles instantly and cause a pretty substantial water hammer.@ NaurisDo you think it will be so easy? I mean cutting yes, but doing nice welds on that thickness? i wouldn´t really feel comfortable stick welding it if i only had a few tries as training. hmm...

author: saike
author_rank: Regular Contributor
timestamp: June 08, 2018, 04:57:24 pm
content: Is it possible to haul a lead acid car battery up to the site, maybe on a small sack barrow?If it is, then try a test weld in your workshop to see how it goes.I have used these for welding many times and with practice, no current limiting is needed, you can just do the welds in small bursts to keep the metal temperature as needed.I do a lot of on site repairs and I always remember what Carl Von Clausewitz said “The enemy of a good plan is the dream of a perfect plan.” so go for it.If that pipe is full of water there is almost no chance that you will burn through it, the water takes the heat away from the weld as fast as you can put it in.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 05:24:26 pm
content: Car batteries might be possible, but it will be a hell of a work to do. I walked up there two weeks ago when i took the pictures and it took me around one hour to get up and down with no luggage at all. There is a narrow trail, but its littered with head sized rocks and small trees, so it wont be fun. We are not there often, so time is valuable. But i think i will try lead acid welding at home as well, even if its just to see what happens.Keep in mind there is not just water, its under pressure, i cant work on it anyways when its filled

author: langwadt
author_rank: Super Contributor
timestamp: June 08, 2018, 05:51:09 pm
content: Quote from: Amper on June 08, 2018, 05:24:26 pmyeh if you have the batteries lead-acid or lipo, 20-40V and maybe a beefy series inductor might be all you need

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2018, 05:54:35 pm
content: Could you get up there with a small offroad motorcycle? Having a way to haul equipment would make things tremendously easier.

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 06:01:51 pm
content: I tried last time with my 650gs but i think its a bit to heavy, at least at my skill level. It might be possible when its completely dry, last time the tire (tkc80) would just dig in at some point and slip.

author: james_s
author_rank: Super Contributor
timestamp: June 08, 2018, 06:50:30 pm
content: Maybe try the old fashioned way and use a pack mule? It would be great if there was a maintenance track or tram running along the pipeline to haul equipment and materials.

author: anishkgt
author_rank: Frequent Contributor
timestamp: June 08, 2018, 08:51:22 pm
content: Or why not use a MOT. Has its own power supply as well. You can built it yourself.I had built one.https://georgehobby.wordpress.com/2018/01/27/maxweldv2/Www.Georgehobby.wordpress.comEquipments: DSO104z, Hakko FX888D, Brymen BM869s

author: mtdoc
author_rank: Super Contributor
timestamp: June 08, 2018, 09:00:14 pm
content: Quote from: anishkgt on June 08, 2018, 08:51:22 pmI don't think a small spot welder is going to be useful repairing an 800mm diameter steel penstock....OP - what kind of power is this generating? 140m is quite a bit of head - but with a 1km long penstock you must have very good flow - as your 800mm diam pipe suggests.What kind of turbine? Electronics? Rectified and feeding a battery bank/inverter system? Would love to see more pics!

author: Amper
author_rank: Frequent Contributor
timestamp: June 08, 2018, 09:22:17 pm
content: Yeop, sorry, spotwelders with MOTs are a bit out of the questionIts currently power limited to 500kW to get into a different category, so we get more money for less output (thats how retarded this world is...) Max power without limiting would be 1MW, though its very seasonal, in the end it turns out to be roughly 2GWh annually. Though dont just multiply by the electricity cost and assume thats what it throws off financially, the financial losses are enormous.Its two peltons, the large one is working at 500kW at the moment into a 400V synchronous generator and feeding into the 20kV grid.Id love to show more pics, but i need to be careful, i dont want to show anything here that can identify where we are, we had copper thieves ripping out everything in the first night after it burned down. The attached ones are probably all the interesting ones i can share.@James_S: Thats actually a very cool idea, though its probably difficult to find someone with a trained one. Thats the problem when you are in such a half civilized area, no mules, and no roads where you need them

author: jmelson
author_rank: Super Contributor
timestamp: June 08, 2018, 09:34:48 pm
content: Quote from: Amper on June 08, 2018, 07:26:49 amI did some welding many years ago with 4 series-connected car batteries and an inductor made out of an old transformer, with a half dozen turns of wire through it. It would occasionally stick, and you had to quickly break the electrode free of either the work or the torch handle. Otherwise, it worked pretty well for some quick repairs.Jon

author: a59d1
author_rank: Regular Contributor
timestamp: June 08, 2018, 11:42:16 pm
content: Have you considered using something like a structural epoxy or composite patch?Obviously, the lifetime's going to be shorter, but it'll most likely be a fraction of the cost of hauling a welder up there.Could something like these also work?http://infrastructure.milliken.com/pipe-repair-systems/http://www.3xeng.com/

author: Yansi
author_rank: Super Contributor
timestamp: June 09, 2018, 12:14:29 am
content: Subscribed to this thread.Love the small family-maintained water power plants. We do get a bunch of here too. Just a bit sad I can't visit yours.

author: CopperCone
author_rank: Super Contributor
timestamp: June 09, 2018, 12:16:12 am
content: if you wanted to build something like this, how much extra cost would adding the nearby asphalt covered road/steps and burying or some how armoring the pipe in some kind of trench/gravel/something be?

author: mtdoc
author_rank: Super Contributor
timestamp: June 09, 2018, 12:49:29 am
content: Very cool Amper. Whoa, 500kW! That is far beyond the realm of micro hydro that I am familiar with.I’ e got a small stream on my property that I’m slowly developing a plan for a 100 -300 W micro hydro installation for.

author: tautech
author_rank: Super Contributor
timestamp: June 09, 2018, 08:07:35 am
content: Quote from: Amper on June 08, 2018, 12:30:04 pmI wouldn't be so fast as to condemn them as poor welds.You've said stainless but by the slag it looks like an RSP rod.If I was turning up to work on an unknown steel type, nickel bearing RSP rods would definitely be one of my choices to use.It's the nickel that makes it look like stainless.They work very well on a large selection of steels and are best applied at lower amperage than most other rods.More expensive they are, but in this case of needing to lug heavy gear onto site the lower current needed could be advantageous.What thickness are the steel patches used on the damaged areas ?Are you aware of any design thickening in the penstocks nearer to the power station as the pressure head increases ?

author: Amper
author_rank: Frequent Contributor
timestamp: June 09, 2018, 09:07:15 am
content: Epoxy is something i have considered as well, one injector of the turbine it self actually has a hair crack that i reinforced with 5mm of unidirectional carbon fiber laminate. The reason why i want to avoid it on the pipe is, i would have to make a relatively large patch or also a band around the broken place. In this case i have no way of checking under it, if there will be a water pocket forming and its delaminating over a larger area it could start to rust under the fiberglass. In this case there is a risk of a larger piece falling off and eventually blocking a nozzle. Thats the absolute horror scenario, as the water hammer can very well make the pipe burst if we are unlucky. Even worse, it could happen inside of the machine house, which would mean about 500m³ at 14 atmospheres flooding the house. UUURGH!The pipes inside needs to be free from anything that could fall off.Im not entirely sure, how much it would cost, but the cost of a complete replacement will be close to a million. The Ground is made from rock, only a thin layer of dirt on top, no way of digging this sadly. Covering it would take incredible amounts of material, i dont think its possible. Making the pathway more accessable is possible and will have to be done when replacing in the future, but for now we are actually happy when no one will notice that there is something interesting up there. What i thougt about for moving tools and material was a 5mm cable, so it would be possible to pull a small cart like a cablecar, but there the limit in time comes to play again.I made a small 600W pelton turbine last summer for emergency 24V power and to run hydraulics for opening the large one. Since the asynchronous generator is now replaced with a synch. we can actually run it off grid like this even when the emergency batteries are dead. That was a problem in the past, when for some reason the power company shut down our 20kV switches we didnt have any electricity at all. Having close to 1MW of water and a direct grid connection but running around with flashlights and a little honda generator...I assumed the weld was not good because its very inconsistent mostly. Th section i have shown is shiny, but the other 4 sides of the patch are completely brown like the surrounding material, definetly a different electrode used. Nice tip though, lower amp electrodes are very welcome here ^^ The patches are also around 12mm in thickness, they are cut from a left over pipe section. Luckily no, they are all exactly the same. The pressure is not so great that more thickness in the bottom is needed.

author: JS
author_rank: Frequent Contributor
timestamp: June 09, 2018, 09:40:48 am
content: I love the plan and I'm familiar with the situation, not power plants but industrial family business, I belong to one and I've worked as independent for others as well. This means I understand your situation and I'm not proposing to contract an external welder, if you can do it yourself you should, even if it's not he absolute best choice this time, next time you have some welding to do it will be a breeze, and it will happen.Water hammer at those scales sounds pretty scary, I'm not used to deal with that kind of failure scenarios, more like early erosion (2 or 3 days instead of expected few month) or some steel pile of scrap. Dead times are expensive but terminal failure with extra consequences are to be avoided.Couldn't you modify an inexpensive inverter welder to run from batteries? I don't know what voltage their DC bar is but it should be doable. If you don't have one of those (you probably do) the price for one shouldn't be a stopper just to see, it wouldn't be a destructive test and I'm sure it will find some use on your toolkit. If you find lower current electrodes to use even cheaper, while getting that pipe up to temp doesn't sound easy. I'm not so fine in my welding, I wouldn't dear more than a bench or table, just ask me to build the welder, not the weld. Maybe preheating the pipe with a torch would be more efficient than starting with a cold material with the batteries.You know better than anyone what you need, how much it cost to stop the plant and how much time you have to do the repair. It might be better to expend the time in researching and having the right tools than having to stop the thing twice or you might be able to start testing in the lower side of the pipes with little expense, like using your existing battery pack and then decide for a larger battery pack or a completely different plan.JS

author: tautech
author_rank: Super Contributor
timestamp: June 09, 2018, 09:56:32 am
content: Quote from: Amper on June 09, 2018, 09:07:15 amJust because the weld fillet is not perfect never assume the weld itself is substandard.Good hobbyist welders like myself can make tidy welds on occasion when all factors are perfect and the stars are aligned, however a competent welder knows their fillet IS structurally sound even when it doesn't look pretty. Fillets don't need to look like prize winners to be effective and good.12mm calls for multiple passes, probably 3 with a 3.2mm rod and maybe 5 with 2.5mm so probably a good 5 minutes welding for each repair patch. A larger 4mm rod could maybe limit passes to just 1 but the power needed is beyond what would be called easily portable and in the 140+ amps region. LA batteries might seem the best option with DC specific rods operating at their recommended voltages. Some research could find DC rods best suited to lower voltages as that could require less batteries to be lugged onto site. You're still going to need 2, maybe 3 12V LA batteries preferably with good CCA and deep cycle specs.

author: Amper
author_rank: Frequent Contributor
timestamp: June 09, 2018, 10:23:29 am
content: Modifying is definetly an idea! As someone else already pointed out, if i need 4 batteries anyways i will have 88V DC, thats not that faar from a 110V capeable welder anyways! I wanted to by a small welder anyways, maybe i will give it a try. The ones we have are all large, either stationary for mag and tig or "mobile" powcon 300A ones. They are 3 Phase 400V, so not really something i will try to just feed DC into. Maybe ill get a chinsy one for playing. Also i have a bunsh of 2kW server PSU laying around, though they are also 230V and will probably not even start up with DC.The welding technically doesnt look that bad at all, it just looks like wo ever did it switched between filler materials inbetween. It will certainly not just pop open, im not worried about failure, just thats an example of what they will sell you for this amount of money. They bring all their stuff up there and then do dodgy stuff. Not something i feel comfortable with. Maybe i will just do some test welds at home and see how long it takes and how much material needs to be put in. Bringing the battery down for charging would be ok though, if its not lead acid. Just bulky heavy stuff will be difficult. Patch size is not clear yet either, i could not find the faulty spot since the pipe is not under pressure right now. When its running again someone will have to walk up there and clearly mark it and in summer when there is no water to run we will repair.EDIT: Something i didnt mention until now is the general attitude of workers there. We have very bad experience in terms of reliability. At the moment we cant fill the pipe because we gave away the hydraulic cylinder parts of the injectors for overhaul. The company promised service in one week. We are at the two month mark soon. Not a very large problem right now since we are not done anyways, but it could have it us badly. Getting the telco to reconnect the phone service took 3 months of "we may do it next week", some of the power cabinets were left outside in the rain and had water inside from the shipping company screwing up and so on and so on.... In July and August almost literally the entire country is on vacation anyways, when something needs work in that time we have to bring it home to germany if possible by any means. Have a hole in the pipe in end of july? Ok, we will be there in september if the weather will be good and the stars allign.Sorry, i got a bit angry there

author: tautech
author_rank: Super Contributor
timestamp: June 09, 2018, 10:50:09 am
content: Quote from: Amper on June 09, 2018, 10:23:29 amDo some more homework, typical AC welders are only ~60V or less.

author: Amper
author_rank: Frequent Contributor
timestamp: June 09, 2018, 10:55:01 am
content: Input, not output

author: langwadt
author_rank: Super Contributor
timestamp: June 09, 2018, 03:15:17 pm
content: Quote from: Amper on June 09, 2018, 10:23:29 amsomething like this is cheap enough that it's worth trying if it'll work on DC, thought 88V is probably a bit lowhttps://youtu.be/TkRv0rabatMcould you screw the patches on? 5-10mm is plenty of meat to drill and tap

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 09, 2018, 03:30:46 pm
content: James_s beat me to the mule suggestion. Horses, donkeys and asses are other possibilities. Perhaps there is even a hobby owner nearby who would consider taking on the transport in return for access to your location, or dinner or something else cheap. In the case that you have to pay full commercial rates it is likely to be far less expensive than a helicopter. This would open up your equipment options dramatically and also save your back and legs.

author: station240
author_rank: Unknown
timestamp: June 09, 2018, 04:47:08 pm
content: It's a shame you can't use the pipeline itself as a trail to move your equipment, make a cart of some sort that rides on the outside of the pipe.I do agree, gas welding sounds a lot easier to move around.Have you considered covering the pipe in something to protect it from impacts ?I know burying it is one way, but then you have the problem of rust/gaining access to inspect.Covering the most likely to get hit by rocks sections with say styrofoam (weighs nothing) or scrap timber might help.

author: Yansi
author_rank: Super Contributor
timestamp: June 09, 2018, 05:00:38 pm
content: No, not even try to work the welder on the low DC. Even if it will work, you will fry the input diode bridge and probably more things, if it does not have under voltage protection.Supplying directly DC to the DC bus inside is pretty possible, however 85V or 115V is too low. You need more like 140-150V, as that's what it gets after rectifying the mains. (supposed there is no active PFC circuit).

author: CopperCone
author_rank: Super Contributor
timestamp: June 09, 2018, 05:48:08 pm
content: you should make it a training ground for the french army corp of engineers

author: Amper
author_rank: Frequent Contributor
timestamp: June 09, 2018, 05:50:10 pm
content: Of cause i would feed it in after the rectifier, not before. Yes, 88V would be to little, though depending on how the machine is constructed.I actually have just remembered something that could throw over the entire plan. We have a sensor line running next to the pipe and even though its used only for 4-20mA signal, it looks very beefy, i will have to check what kind of crossection it has. If im lucky and its appropriately oversized it may just be enough to get power up there. 3 Phase 400V i dont need many amps.Covering it with treestems would probably be a possibility, i will have to think about that! Styrofoam will not live long enough though and when it rots it will fly all over the natural reservate. People will not like that ^^Hence no training ground either sadly, its about 40km from civilisation inside of a protected forest.

author: Yansi
author_rank: Super Contributor
timestamp: June 09, 2018, 06:01:51 pm
content: Maybe time to ADD a power cable near that pipeline, with a multiple power outlets along the way. Would probably save this hassle next time. How long is the pipeline?

author: Amper
author_rank: Frequent Contributor
timestamp: June 09, 2018, 06:12:39 pm
content: 1000m, yes, a power cable would be cool, but even a normal not outdoor and rock hardened cable 4mm² will be 500kg at that length. Yes, we have some upgrade potential here as well, but for now i will rather drag equipment by hand than half a ton of wire

author: JS
author_rank: Frequent Contributor
timestamp: June 09, 2018, 11:16:20 pm
content: Quote from: Amper on June 09, 2018, 06:12:39 pmNot to consider the voltage drop across the cable, but I guess you can ask the guy on the bottom to open the faucet a bit moreJS

author: nctnico
author_rank: Super Contributor
timestamp: June 09, 2018, 11:42:59 pm
content: If you already bring a torch anyway then use that to weld. Perhaps send someone up there who can do torch welding (ask to demonstrate skills before commisioning the job).

author: mzzj
author_rank: Super Contributor
timestamp: June 11, 2018, 07:30:17 pm
content: If you don't want to invent completely your own most inverter stick welders would work happily if you provide ~280vdc to input.110VAC input stick welder would work with ~140vdc inputOr buy ready made unit from Fronius:http://www.fronius.com/en/welding-technology/products/manual-welding/mma/accupocket

author: mzzj
author_rank: Super Contributor
timestamp: June 11, 2018, 07:50:43 pm
content: Quote from: CopperCone on June 09, 2018, 05:48:08 pmsmall sponsorship for local mountain climbing club or some other crazy-ass atheletes?

author: Amper
author_rank: Frequent Contributor
timestamp: June 12, 2018, 05:54:59 am
content: I just found some pics related to the 24V emergency turbine i built last summer, not much, but maybe interesting to some. In the videos its running off 6 bars from a centrifugal pump, so it only makes roughly 1/4 of the power it will have later. It will be mounted on a rubber reducing piece, so no splashing water and the electronics are tidied and boxed up watertight, this was just the first test to see if performance was as calculated.speed at max power is 5000 min⁻¹, active diameter 100mm, bldc generator originally with buck converter, now with shunt regulator for increased lifetime/ reliability. It will start up as soon, as the 24V systems backup battery is close to depleted, so there will still be lighting, network/phone connection, remote monitoring and the possibility to do a complete dark start.https://youtu.be/LSOzFsmXQIUHappy to answer questions/suggestions!

author: 3roomlab
author_rank: Frequent Contributor
timestamp: June 13, 2018, 02:17:00 am
content: how many days of cycling does the battery last before it needs to be replaced?

author: dcarr
author_rank: Regular Contributor
timestamp: June 13, 2018, 03:31:39 am
content: Looks very interesting, tell us about the casting process!

author: vk6zgo
author_rank: Super Contributor
timestamp: June 13, 2018, 04:50:04 am
content: Quote from: nctnico link=topic=116170.msg1598446#msg1598446e date=1528587779Exactly, oxy-acetylene welding was the method of choice for many years for welding water pipes, before the common availability of electric welding equipment.You can probably get away with braze welding using bronze welding rods.Using gas welding equipment is not rocket science-----I learnt by doing with a home kit.Also, asStation240suggests, use some kind of protective material to prevent pipe damage.

author: mtdoc
author_rank: Super Contributor
timestamp: June 13, 2018, 06:32:10 am
content: Quote from: dcarr on June 13, 2018, 03:31:39 amYes, casting your own turbine - very cool.I've seen pics of a homemade pelton turbine that was built up using welded metal spoons(!) but never a home casted one.

author: Amper
author_rank: Frequent Contributor
timestamp: June 13, 2018, 06:49:17 am
content: We have 8 x 6V 165Ah dryfit batteries, they are made for this kind of application. Also they will not cycle often hopefully, only in case the main power fails and in this case it will take roughly 4 days to empty them. The reason is, that the 20kV switches can be remotely triggered, but not be rewound automatically so someone has to physically get to them and reconnect. We have someone there to do this for us, but when hes not available we still want remote control and camera access. The small one will make that possible indefinetly, so in summer no one has to be in a hurry when there is no power generation anyways. The batteries will do one cycle, the turbine will be turned on and run until someone resets the system.The casting was a fun experience as you might imagine, it was the first aluminium part i made. It was printed in pla (NEVER use ABS, it stinks so much worse when firing!!) and then cast in a lost plaster/ silica sand mold. It had to be done on a centrifuge, the risers didnt work well enough. Also its important here to consider how much force the spinning even at moderate speeds puts on the plaster, the first try developed cracks while casting and i had .3l of liquid aluminium in a nice radial pattern all over the place.The bubbles visible are only on the surface, in the shaft hole there is absolutely no fault visible and the buckets didnt show any faults after grinding.Id really like to redo it some time in aluminium bronze, the stuff is as tough as steel and does not corrode even in seawater, no connection to normal bronze (550N/mm²!). Propellers for large ships are made from this.The entire machine is made to be completely heads free, only the rotor is moving, no adjustable nozzle, no deflector, no regulation. its made to just run freely and the power drawn will limit the speed. Though it is of cause possible to run it without any load, it will keep running at 10krpm. All materials used are stainless or aluminium, so no corrosion problems. Startup will most likely just be a weight and a selenoid, so when power runs out it will drop and start. I just love crowbars and brute force approaches in these kind of applications.

author: Dubbie
author_rank: Unknown
timestamp: June 13, 2018, 10:42:00 pm
content: how did you balance the casting?10K rpm is a lot!

author: Amper
author_rank: Frequent Contributor
timestamp: June 14, 2018, 07:08:45 am
content: yes, 10k is substantial, actually first i was a bit afraid that it might loose buckets at some pointI have a bit of experience from building model jet engines and turbomolecular pumps, those things need to be balanced extremely well, though in my experience the best way is to do it with your fingers. for light rotors just hold the closest bearing in your fingers and blow on the rotor with compressed air. With this one it was much easier since the generator is actually a bldc motor, so i just hooked it up to an inverter. Then add a small weight of tape to one random spot and see what it does, rotate it until you find the right place, then remove some weight on the opposite side and check if it worked.It seems very crude, but balancing like this will bring better results than turbocharger balancing machines if you have some patience!

author: Dubbie
author_rank: Unknown
timestamp: June 14, 2018, 11:21:20 am
content: I don’t know much about pelton wheels, is the entire housing flooded or is there some air in there? Is there any balance issues with the cups being slightly different capacities? Or does that not matter?Very interesting little project.

author: tautech
author_rank: Super Contributor
timestamp: June 14, 2018, 11:48:09 am
content: Quote from: Dubbie on June 14, 2018, 11:21:20 amThey're in an air filled housing, not flooded and rely on high heads that provide high velocity water jets.A little here Dubbie:https://en.wikipedia.org/wiki/Pelton_wheelYou could use plain flat paddles but the efficiency would be low. Unlike the big commercial turbines that run fairly quiet and at relatively slow speed these things whizz along and generate a characteristic howl as each paddle cuts the water jet.Interesting example of one still operating in the Golden Bay area of South Island NZ. (been there ~30yrs back)https://www.trustpower.co.nz/Our-Assets-And-Capability/Power-Generation/Cobb600 meters of head !Bit more here:https://photonews.org.nz/nelson/issue/NPN79_19670527/t1-body-d12.html