Off grid workshop - first steps. - Page 1
Forum section: electronics / projects

author: Kibi
author_rank: Unknown
timestamp: November 25, 2012, 10:01:11 pm
content: I am miles away from taking my workshop completely off grid, but you have to start somewhere and take small steps with some things.A few weeks ago I did a teardown of my newly acquired inverter / charger. Since then I got to work on preparing the battery to make it go.Several years ago I discovered an old APC 7.5KVA UPS in the dustbin. It was too unwieldy to transport besides it smelled of burning MOSFET, but it's batteries were modular and easier to transport. I have kept the batteries maintained, waiting for the opportunity to find a good inverter cheap, that's when I found the Victron out of an old ambulance.The APC had four battery trays in it each tray comprised of eight 12V batteries wired in series for 96V. Two of these trays were then wired in series for 192V system voltage for the inverter. My guess is that at 7.5KVA, a 192V system voltage reduces the current to a more manageable 60A. The APC that I found had another battery pack alongside it which contained another eight trays in a similar configuration.So, I have a total of twelve 96V battery trays.Here is one of the trays showing the original wiring.APC went for two 30A fuses in parallel to protect each tray. I made use of one these fuses per tray in my configuration.Most of the batteries in the trays still read above 12.5V despite having a top off charge about two years ago. I'm just not so sure of the brand of batteries used. I guess if APC were happy, then they can't be that bad.So now, I need 12V for my system, so I needed to wire all the batteries in each tray in parallel, fuse it and put some terminals on the end of the tray.I made some terminals out of threaded brass rod.I made a jig to assemble the new wiring inside the tray....and made up the wiring with a fuse included.My little JBC iron didn't seem to bothered about soldering an M6 brass nut onto a length of threaded rod, it just sort of got on with it.Next, the 12V batteries were re-orientated as required and wired up.Then the tray is closed up again.Wash, rinse, repeat twelve times. I must tell you, I don't cope too well with repetitive tasks, but luckily I was well behind on my Amphour episodes, so that helped the time tick away somewhat.Now I needed to make up the leads to connect all the trays together. I went for 25mm² cable for this task as it's what I had to hand.I cut short lengths and soldered terminals onto the ends. The JBC was not quite up to this task though, so I had to use a torch.I just heated and fed the solder in through the hole in the top until solder came out the bottomThen, bolt all the wiring in including the shunt for the Victron battery monitor.It's ready. The whole lot weighs in at about 220KG, so although you can't see, it's on wheels for manoeuvrability.That's it for now. Hopefully by next weekend, I'll have the inverter installed and running.

author: Lightages
author_rank: Unknown
timestamp: November 26, 2012, 02:57:19 am
content: You should be aware, that many batteries in parallel are not going to share very nicely. Usually you don't want to parallel more than 4 times. If one battery becomes shorted, without each battery having a fuse, you will dump all the available current into that battery and have quite violent fire. Even if they are fused, the lowest internal resistance battery can still get quite of current dumped into it causing to outgas and fail. Please be careful.

author: Wartex
author_rank: Frequent Contributor
timestamp: November 26, 2012, 05:19:16 am
content: you connected your batteries wrong. Connections should be on opposite ends of the bus bar for + and -. Drain your pack at 20A, then measure voltages on each battery you will see what I mean.

author: Lightages
author_rank: Unknown
timestamp: November 26, 2012, 05:53:33 am
content: Actually, look gain. He did connect opposite ends

author: Kibi
author_rank: Unknown
timestamp: November 26, 2012, 12:23:37 pm
content: Quote from: Wartex on November 26, 2012, 05:19:16 amYes, I did make connections from opposite ends of the bus bar. I did this both in the trays and the larger connections outside.Quote from: Lightages on November 26, 2012, 02:57:19 amYes, I realise that this is not ideal, however, all 96 batteries measured 12.45V within 10mV of each other.They are not even the correct batteries to use for this application. Over the next year, I'll be able to save up for some proper deep discharge batteries better suited to this application.What I need to do next it put a good load on the battery arrangement and then measure the current out of each tray at least to ensure that the current is equal out of each one. Although it's not fully charged, I could still do a load test. It's currently charging at 600mA, so it should be fully charged within the next couple of weeks. If anything is out of order, the pack will not be used and I'll have to wait for Santa.Small steps.

author: SeanB
author_rank: Super Contributor
timestamp: November 26, 2012, 04:21:55 pm
content: Nice modification there, and at least the current per unit battery will be nice and low. You just need to have the whole lot as a table, with a nice top on it to sit in the centre of the workshed. I have a roll of the 0 gauge cable that I use as a footstool.

author: Kibi
author_rank: Unknown
timestamp: December 03, 2012, 08:38:57 pm
content: Unfortunately, this plan did not workThe batteries are too tired. I charged them at five amps for several days until they floated. I then requested about 100A out of them and the voltage plummeted rapidly and steadily. Approximately 37 seconds then the inverter shut down at 11.5V. Fail.Oh well, I still think it was worth trying to get some use out of the batteries that I had to hand.Now I'll have to do some hardcore saving and get some decent batteries.

author: kripton2035
author_rank: Super Contributor
timestamp: December 03, 2012, 09:07:24 pm
content: perhaps could you try to desulphate some batteries and make another test ?

author: Lightages
author_rank: Unknown
timestamp: December 03, 2012, 09:35:46 pm
content: As I said, you might have problems with so many batteries in parallel. Try recharging again and then disconnect and let them sit for 3 hours. Then measure each individual battery, not one assembled pack, and see which of them are not up to around 12.7volts. Mabe you will find a weak bunch and maybe can get things up and running with less batteries.

author: ptricks
author_rank: Frequent Contributor
timestamp: December 03, 2012, 10:03:02 pm
content: 12.5V is too low for these type of batteries, you should measure 13.1-13.8V no load , they are 5AH batteries which means max sustained current is about 2A for about 1.5 hours. If you put a 5A load on one it will only last about 30 minutes even though it should last 60 because of the type of cell. They only way you get 5AH out of these batteries is to draw no more than 1A per hour for 5 hours. So out of each rack of batteries to get the full stored power you would need to only use 9A on each one or 108A.See if you can get the datasheet for the batteries and there should be a discharge curve .I personally like the panasonic batteries for use in UPS, the other brands haven't lasted long.

author: ptricks
author_rank: Frequent Contributor
timestamp: December 03, 2012, 10:10:49 pm
content: Quote from: Kibi on November 26, 2012, 12:23:37 pm600ma per battery or across many batteries. Anything less than 100ma per battery and you are not going to effectively charge them because the self discharge rate on SLA batteries will consume whatever you put in . If the battery is any good you should be able to put 1A on it for 4 hours and have it over the 13 volt range.

author: Kibi
author_rank: Unknown
timestamp: December 03, 2012, 10:15:17 pm
content: Quote from: Lightages on December 03, 2012, 09:35:46 pmThis may be well worth doing, they are actually on charge again - charger is now set to 3A charge for safety concerns. I'll see how long they take to fully charge. Then yes, take them apart and see which ones are which. If only half of them are good, then it won't be enough for the project, but plenty for a backup supply or even a 12V appliance supply. Who knows, experiments will only reveal, but I'm not holding my breath.

author: Kibi
author_rank: Unknown
timestamp: December 03, 2012, 10:21:57 pm
content: Quote from: ptricks on December 03, 2012, 10:10:49 pmIt was 600mA for the lot until I got the Victron installed. Then I set the charge rate at 5A. I didn't want to go for the 80A charge for safety reasons.The voltage did actually increase by about 100mV per day with the 600mA charger though.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 05, 2012, 01:02:06 pm
content: An off-grid workshop is something I'm aiming for too. Only it needs three phase.Sad but true story: Not so long ago I had to watch four Chloride EDP90 industrial 3-phase UPS units get bulldozed. Each one was about 120KVA, complete with battery banks. Except the building they were in had been 'walked away from' leaving the UPS's online, supporting lights, etc. So the thousands of dollars worth of batteries had been run down to completely flat, then left that way for months. All ruined. The UPS units were quite new, I think only a few years old, and in perfect working condition apart from the wrecked batteries. Until they were smashed during the building demolition. Not just accidentally, but deliberately.The UPS units could easily have been extracted before the demolition, so it was purely a matter of official bloody-mindedness, not the weight. Though they weighed around 1200Kg each, that could have been managed.Really tragic. One of the worst instances of deliberate, criminal destruction I've ever seen. And I've seen many.This is how it goes in Australia.Oh and there were three 1MW diesel backup generators complete with their entire control system, also destroyed. I looked through the maintenance log books, and they'd been scrupulously maintained and regularly started.This was the old Channel 7 site in Sydney, for those that know it.Someday I'd really like to find out _why_ it was felt necessary to destroy all that stuff.Don't believe me? I have photos.Edit..Ah, I also meant to say, that I don't think it's really advisable to wire a bunch of lead-acid batteries in parallel as you have. Reasons:* Each battery will have slightly different characteristics, and the charge/discharge won't share so well.* You can't diagnose the state of individual batteries.* If any of those batteries develops an internal short in one cell, the rest of the bank will discharge violently through the bad one.The reason large UPS systems run their batteries in series is not just to achieve a high voltage and low current suitable for the switchmode drivers, but also as it makes it possible to measure the state of individual batteries. And then do battery management and leveling - topping up individual batteries in-circuit that are a getting out of balance with the rest.

author: Kibi
author_rank: Unknown
timestamp: December 05, 2012, 11:07:46 pm
content: Quote from: TerraHertz on December 05, 2012, 01:02:06 pmThis is a shocking story, it happens all to often I'm afraid.As for this battery bank, I doubt I'm going to put a great deal more effort into it for many reasons including your's and other's concerns about have 96 batteries in parallel.The performance is still not acceptable. It ran a 30A load for about two hours. I reckon it'd have died (12V) after another hour. It should be four hours to 25% DoD.So, this evening I finished connecting up my BMV600 battery monitor.I have also wired up the battery monitor to a computer. This was rather challenging.First I had to find a computer with "Windows" on it, apparently made by some company that call themselves "Microsoft". OK, I have one knocking about, but it also needed a serial port on it, another unfortunate rarity these days.Once this was done, one is supposed to shell out £100 for a cable that connects the BMV600 to the serial port. I guess Victron's idea is that this is pocket change to people who own a yacht and they'll just buy one, but not I.After a bit of scouring through Victron's own publicly available documents I found out the pinouts of the BMV600, the protocol and the signal levels.So, I knocked up my own cable using a MAX3232. The BMV600 powers the cable via it's own 3.3V line.....and it works well with their software which allows you to log to a CSV if you wish. Leaving a computer (with "Windows" on it) switched on the whole time is silly, so I'll have to figure out how to port this data to my Thingspeak channel.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 07, 2012, 06:50:46 am
content: That's a nice unit there. And yeah, I hate it when manufacturers do their best to gouge you for some accessory that *should* be included originally. I have a couple of 8-channel thermocouple scanning monitors (TP488-RT-240) by an Australian company (Amalgamated Instrument) that need a tiny serial interface rider board so I can interface to a system. They want $250 each for them. A maybe 4 square cm pcb, that will have just an RS232 or 485 driver IC and nothing else. I think I'll see if I can derive the required circuit from the pinout of the rider header, and just make my own.Incidentally, if you're setting up a battery bank and inverter, with probably also eventually a solar cell array, then you should look at battery charge management units (aka PV charge controller), not just monitoring. They have nice things like battery disconnect to prevent over-discharge, protection against over-charge etc, as well as logging of battery state.I got one MP3129 by Powertech, via Soanar. Seems to work fine.

author: Kibi
author_rank: Unknown
timestamp: December 07, 2012, 10:57:53 am
content: I will be looking into getting an MPPT charge controller for the PV's. Morningstar do a nice one, not as expensive as the Outback ones, but with loads of cool features including logging and web admin. They do 45A and 60A controllers.http://www.morningstarcorp.com/en/tristar%20mpptUntil I get PV's, the inverter will take care of the charging on a tariff shifting basis (electricity is very cheap between 00:00 and 07:00). The inverter has a very good charger in it which is highly configurable. It can charge up to 80A which on my planned 675Ah bank is below C/5 but high enough charge rate to complete a full charge on a 20% discharged bank within 7 hours and even carry out an equalisation charge on a weekly basis. At 80A, it'd probably even manage the odd 50% DoD cycle.My initial PV setup will not be able to complete a charge with a DoD of those quoted above, but they'll help

author: Kibi
author_rank: Unknown
timestamp: December 08, 2012, 02:08:25 pm
content: Actually, I forgot that I already have a basic MPPT controller. It's one that I made earlier, it just needs a bit more work on the code. It's only 10A, but it'd do for a start.http://mjlorton.com/forum/index.php?topic=68.0

author: Unknown
author_rank: Unknown
timestamp: December 10, 2012, 12:32:01 am
content: Quote from: TerraHertz on December 05, 2012, 01:02:06 pmYou know this how exactly?QuoteLights? Oh really?QuoteYou sure?QuoteEasily? If so easy then why didn't you extract them?QuoteBetter than you may imagine. Perhaps you can comment on the multi year logistics effort to migrate the facility, dispose of redundant equipment et?QuoteDid you avail your self of any of the opportunities to purchase/obtain redundant equipment? No? Neither did anyone else including salvage operators.Grand ideals and economic realities do not always coincide. I'd love to see everything re-purposed or recycled too. In a tunnel vision view it is easy to point blame at owners and contractors. The reality is however that none of that stuff was ever going to fit/be welcome in yours or anyone else's shed.

author: TerraHertz
author_rank: Super Contributor
timestamp: December 10, 2012, 02:25:58 am
content: Quote from: Uncle Vernon on December 10, 2012, 12:32:01 amPersonal hands-on examination of the setup, multiple times, during the period when the buildings were empty.The UPS output breakers were all still on, and the batteries all had that 'swollen sides' effect they get when they've been completely flattened and left that way for months, and sulfation makes the plates swell. Also the building had been left with internal power & lights on for months, then at some point the external mains power was switched off. It's true, I'm _assuming_ at that point the UPSs got loaded until dead.QuoteYep. You know, those things in the ceiling that let you see where you're going, even at night. For a long time they were mains powered, then mains was cut off, but there were still some lights. Maybe those were running from some other battery backup system, and the big UPSs were only supporting something else. Nonetheless, the UPSs were run down till dead.QuoteThe manual with them said 1995; building demolished in 2010. OK, so the oldest they could be is 15 years. They still looked like new, having been housed in a nice clean place. And 15 years counts as a 'few years' for things like that. What did they cost new anyway? Since it seems you know of them.QuoteYou're assuming I didn't try, in multiple ways. It wasn't possible, and not for reasons of physical logistics.QuoteOK, lets talk about that.* Big old fully gimballed steerable dish on top of the tower. Said by a suit onsite when I enquired: "has been sold for $100K" (just by the absurd amount I knew he was lying.) It was still on top of the tower when the tower was collapsed. (Judging by observing the crushed weather shield in the rubble, though the dish and mount itself seemed to have been sent off for scrap.)* Three 1 MW diesel generators and complete grid handover system - destroyed.* Four 120KW UPSs (according to the docs, though I only found 3 of them.) all bulldozed. Could have been extracted by a couple of people in a day's work and some lifting gear, easily.* Countless 19" racks, all destroyed.* Piles of tech docs and manuals, including the entire doco on the station's infrastructure. You think the National Library wouldn't have liked to get the complete doc set from a historic TV station? But no, bulldozed.* At least it seems most if not all of the technical equipment was removed before the demolition. Judging by notes left about the place, a lot of it was given away to friends. Which is good to hear.So, you were involved in this. Tell me, did you ever advertise any of the above, on public forums, for reasonable 'take it away' prices?QuoteActually I _did_ and the demolition operators were flatly opposed to the idea. There was a long period when the site's ownership was indeterminate, and I had no luck even finding someone responsible. Later when Meriton was the owner, every contact effort was completely futile. I got the impression they wanted to see it all destroyed.QuoteSpeak for yourself. The UPSs would have made a *huge* difference to my primary project. For which, lacking them, I actually have to obtain/built something like one (though not that high a power.) They absolutely would have fit in my 'shed', and having three would be fantastic. One to dismantle to reverse engineer it, one to modify for my purpose, and one as a backup. Undertaking a major hacking project on a single unit is pointless, because your effort is wasted if you break something.The diesel generators - are you seriously claiming that no one in Australia would have wanted them, for just the retrieval and transport costs? Including the room full of manuals and spare parts? I doubt it. You sure you're not trying to justify the incompetence of the people responsible for this wanton destruction, so you/they don't feel bad?Seriously, where was the ebay.com.au listing, for "120KW UPS, works, starting bid $1, onsite pick up only, weighs 1000Kg. Four available."There wasn't one, was there?

author: Kibi
author_rank: Unknown
timestamp: December 16, 2012, 03:44:38 pm
content: Right, so I've got everything installed and running now.I had to wait for a time delay (S) RCD switch to come around a sensible price. They are quite expensive understandably. I eventually found a good 100mA time delay RCD for a price I was willing to pay. This switch is needed to replace the original 100A incomer and is wired upstream of the inverter. 100mA protection is acceptable for non-contact circuits.The time delay aspect is to provide discrimination for the downstream RCBO's. This is not just for convenience it's absolutely essential for my application. It prevents you from waking up and finding yourself with two or more arses, which apparently, is never an ideal situation.So, imagine that the inverter is not running and it has switched the incoming mains through to the loads. If there were to be a fault current to earth (via a human for example) and there was a 30mA fast acting RCD ahead of the inverter that responded first, the mains to the inverter would fail and the inverter would then switch on thus fault current would continue to flow through the person. There would be an extended delay whilst the earth relay in the inverter closes (the relay that connects neutral to earth to facilitate the operation of downstream RCD's) and then the downstream RCBO on the circuit to which the person is connected to would finally have a chance to disconnect. By this time the person (luck being on their side) would be feeling like they'd been hit by a train, a steam one to be more precise.Now it's all be wired up correctly and the disconnect times need to be measured.The 100mA time delay switch operates in 250mS at 100mA fault current up to 80mS at 500mA fault current. Good.I then tested all the downstream RCBO's beyond the inverter with the inverter off (grid passthrough). They all disconnected within 20mS regardless of the fault current between 30mA and 500mA. The upstream time delay RCD never responded at all in this test. Good.I then repeated the test on the downstream RCBO's this time with the inverter running (grid disconnected) and again, around 20mS disconnect times. Good, the gods are pleased.This installation of the inverter is now complete and I can run some experiments using my existing batteries until I get hold of some good ones.