High amp power supply - Page 1
Forum section: electronics / general

author: mrphil
author_rank: Contributor
timestamp: June 07, 2016, 09:31:18 pm
content: Hi guys,I need some advices.I am looking to buy something but I'm not really sure exactly what I need so let me start by leeting you guys know the context.I am a mechanic and I do on site computer programming (pcm,bcm, etc... ).Some car are really specific on what voltage the computer needs to be when doing such a jobLet takes for example BMW. When programming those, the voltage need to stay between 13-15volts.A normal programming job on these can take more than an hour and during programming, its normal for accessories to get activated by the computer so amperage draw is varying from 5 to 70amp depending on what computer you are programming and what accessory is turned on momentarily.So to get an image , the amp draw can go from 5 to 10 to 30 to 10 to 40 then to 5amp in a few minutes and voltage need to stay between 13-15volts all this time.My normal battery charger can push 70amp without any problems but voltage will rise above 15 volts and if I lower amps , voltage can get lower than 13v when accessories are turned on.BMW are recommending Schumacher inc-700a chargers which will vary amperage to maintain a constant voltage.These cost around 700$.So I am looking for a power supply that could do the same job..Any idea where I should look?

author: grumpydoc
author_rank: Super Contributor
timestamp: June 07, 2016, 09:46:59 pm
content: Given that you want a PSU capable of delivering a regulated 13-15V at up to 1kW anything you would want to use is likely to be expensive.Does shopping around help? - eghttps://www.eevblog.com/forum/beginners/z80-single-board-memory-bank-switching/msg268402/#msg268402seems to be $200 cheaper than you thought.

author: nctnico
author_rank: Super Contributor
timestamp: June 07, 2016, 09:49:48 pm
content: How about using a charger but keep the car's battery connected? The battery will serve as a buffer and help to keep the voltage within range.A normal PSU will be of little use because it is not designed for use with a battery connected so I don't recommend going that route!

author: Monkeh
author_rank: Super Contributor
timestamp: June 07, 2016, 09:51:49 pm
content: As you're working on a system with a battery, the ability to supply the full load is not required, merely enough capacity to keep the voltage from drooping excessively.Perhaps something along these lines would suffice:https://www.circuitspecialists.com/csi1560sw.htmlThese sorts of supplies shouldn't mind being used across a lead-acid battery so long as your output voltage is definitely above the battery voltage.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 07, 2016, 10:03:52 pm
content: Quote from: Monkeh on June 07, 2016, 09:51:49 pmIt's not just about not damaging the charger though is it? - it's also about not damaging the battery (or car).The OP is obviously offering to do the programming for a fee, would you want someone working on your new BMW who didn't want to get the correct kit?Especially as it's only another $241 to get the recommended charger.

author: Monkeh
author_rank: Super Contributor
timestamp: June 07, 2016, 10:16:54 pm
content: Quote from: grumpydoc on June 07, 2016, 10:03:52 pmIt would be quite hard to damage the car by applying 15V! And the battery wouldn't mind for a short duration, either.. Those Schumacher units are really no different to a common CV/CC bench supply, far as I can tell.As the price difference narrows it does get rather less compelling to 'cheap out' (refuse to be bent over would be more accurate..).

author: mrphil
author_rank: Contributor
timestamp: June 07, 2016, 10:48:41 pm
content: Quote from: nctnico on June 07, 2016, 09:49:48 pmThe battery buffer is at best 12.6v and the software is throwing me a warning as soon as I get to 12.99v. Even if 13v is the minimum recommended, 14v is the ideal voltage so 12.6 is far from acceptable.Quote from: Monkeh on June 07, 2016, 10:16:54 pmGetting 15v on a car won't damage anything. There are normal chargers that runs at 14.7 or 14.9vI know I can't afford to damage a car only to save 200$ on the battery maintaining unit . I'm not looking for a "cheap - almost the same " unit . what I was asking is like user Monkeh has refered an "equal" alternative. I don't think Schumacher invented something new with this charger . my guess is that probably they are selling an existing technology for a niche market with an overpriced tag due to the fact that it is for that niche.... Maybe I'm wrong .This csi1560 p/s look like what I am looking for but I don't know enough about p/s to tell. Thats why I'm asking "electronic" gurusAsk me about cars... I will tell

author: nctnico
author_rank: Super Contributor
timestamp: June 07, 2016, 11:12:38 pm
content: Quote from: mrphil on June 07, 2016, 10:48:41 pmA warning isn't an error so I'd just ignore that. Pushing too much current into a battery and/or overcharging it isn't healthy for it. I know some cars are charging to 15V but this is only for short periods to top the battery up quickly after starting the engine. I'd put it this way: if a car's battery isn't capable of dealing with short loads of 70A then it is a good idea to replace it anyway.

author: mrphil
author_rank: Contributor
timestamp: June 08, 2016, 12:28:21 am
content: Quote from: nctnico on June 07, 2016, 11:12:38 pmThe software I am referring to is ISTA-P , the software provided by BMW, so i don't see why I should ignore a warning that tells me to get the battery over 13v if for example the cooling fans are turned on during programming and the battery drops to 12.2v. There must be a reason they ask to maintain over 13v.Second, if BMW recommend he Schumacher 700a which push 70a @ 14v WHEN NEEDED, then using a 14v power supply which could push the same amperage if needed (if the fan or fuel pump are turned on) , I don't see where is the problem.I've found a midtronic psc550s which is essentially the same kind of device but with 55amp for around 350$. I think I'll go with it. The 70 amp request is the maximum theorical request for E90 models (335 serie I think).But I've done some E90 and I never went over 50amps.I guess he car must be equipped with EVERY options to get to 70amp in some extreme circumstances.

author: uncle_bob
author_rank: Unknown
timestamp: June 08, 2016, 12:33:59 am
content: HiYou don't just need a power supply. You need a device that is set up to work with a battery as a load. That makes it a bit unusual compared to a normal supply. Shop around and get the real thing for $300.Bob

author: Monkeh
author_rank: Super Contributor
timestamp: June 08, 2016, 12:39:52 am
content: Quote from: uncle_bob on June 08, 2016, 12:33:59 amIn what way is a CV/CC supply unsuitable? Other than the potential problems of starting the engine with it hooked up.

author: uncle_bob
author_rank: Unknown
timestamp: June 08, 2016, 12:53:18 am
content: Quote from: Monkeh on June 08, 2016, 12:39:52 amHiIn no particular order, and certainly not an exhaustive list:If the supply is set at 13.5 and the battery happens to be at 14 ... may not be not good at all.The control loop in the supply may not be very happy at all with a load that can both sink and source power.The supply may or may not be set up to act properly when the line voltage goes down and the battery is still hooked up to it ...If you have nice big inductive loads, the supply may or may not be happy with spikes.Yes, it all depends on the supply, how it was designed, and how lucky you get.Bob

author: mrphil
author_rank: Contributor
timestamp: June 08, 2016, 01:59:59 am
content: I guess all these kind replies are comforting me in getting the midtronic which is designed for automobile uses.+ at 350$ its a good deal.Thanks all for your help!

author: mtdoc
author_rank: Super Contributor
timestamp: June 08, 2016, 05:53:57 am
content: You should have a look at theIota battery chargers. They have a very good reputation.

author: m4f1050
author_rank: Newbie
timestamp: August 25, 2020, 07:38:33 pm
content: Sorry to revive old thread, but since I was searching for this particular solution I wanted to share mine....CbRadiosProntosells these and in a variety of flavors, like 50amp, 75amp, and even the popular 100amp model.I bought this model, 100 amp for $199.99100 AMP CONTINUOUS POWER SUPPLY-CONVERTER-BATTERY Charger 12 volt 13.8 vdcAnd a 2gauge 20ft jumper cables for $20.99 which I cut in half and can use other half for a 2nd unit.Booster Cables 2 Gauge Jumper Leads 20 FT Heavy Duty Car Van Clamps Start USMaking it the cheapest solution, just a little over $200Hope this helps.

author: duckduck
author_rank: Frequent Contributor
timestamp: August 27, 2020, 08:22:46 am
content: If you really wanted to go cheap, how about a server power supply? You can find them on ebay for US$20. You can dial them up to nearly 14 volts and if you give them 240 V input they will output 100 A. I bought one of these and I thought, hey, this thing could replace my car battery charger / starting assist unit!https://www.ebay.com/itm/HP-1200W-Power-Supply-DPS-1200FB-1-A-HSTNS-PD19-570451-101-579229-001-570451-001/383682847988?hash=item595547a4f4:g:qJMAAOSw2WBfPEYH

author: uncle_bob
author_rank: Unknown
timestamp: August 27, 2020, 01:03:16 pm
content: HiA proper battery charger will tolerate voltage "back feeding" into the output. Think of what happens if line power fails while you are charging the battery ...Unless you are going to do a lot of manual intervention, a proper charger detects "full charged" voltage (or current drop off) and then cuts back it's output voltage. This is a really good idea if you want your batteries to live a long and happy life. It also reduces the number of times you have to add water to the cells.Bigger is not always better on a charger. If you have a 25AH battery, a 100A charger is generally *not* considered to be a good idea. Since battery capacity drops as batteries age, who knows what the capacity of this or that battery is right now ...Yes the above is targeted at lead acid. Lithium has it's own issues. They aren't identical, but indeed you have the same set of problems.Bob

author: m4f1050
author_rank: Newbie
timestamp: August 27, 2020, 07:58:05 pm
content: I guess I forgot to mention, this unit has 3-stage (charging) or fixed (programming) output. All you have to do while programming is have it set to FIXED OUTPUT which doesn't serve as a "charger" and you just set your desired voltage, in my case I like to use 14.2v that way if fuel pump or other electric item activates while programming it will not lower the voltage below 13v ever, not even 13.5v which is what the idea is.

author: uncle_bob
author_rank: Unknown
timestamp: August 27, 2020, 08:39:07 pm
content: Quote from: m4f1050 on August 27, 2020, 07:58:05 pmHiWhich doesn't help when you buy the $20 server power supply .....Bob