Checking 12v Batteries in Parallel - 12v Solar Shed

[@ChrisDIYerOklahoma]

👍 Nice test. Those UNI-T clamp meters are awesome. Question: What are your thoughts about battery string balancing? I have 12 six-volt batteries wired for 24v, three strings of 24v and then paralleled via bussbars. Haven't had any issues, but is it possible the more batteries one has...the more propensity for problems? Parallel will def add up current, but with series-parallel strings, one is increasing voltages + currents. Thanks!

[@AdamWelchUK]

Cheers Chris - I think you're more experienced in that configuration than me! The strings of 6v batteries should act like mine and I want to say that each string should provide an equal amount of the overall current assuming they all have the same length cables to the bussbars. Increasing the number of batteries increases the potential for one to go bad - same with anything I guess.

[@MrBrymstond]

You could always hook a warning buzzer up to each battery if worried.

[@AdamWelchUK]

Based on voltage? It wouldn't work I don't think as they are all connected in parallel they'd all show the same voltage.

[@MrBrymstond]

Based on voltage. If a short occurs the voltage will change quickly.

[@AdamWelchUK]

Ah I see what you mean now. I'm not too worried about an overall short - the battery box should prevent any wires from moving and they are tightened up quite well. In the video I was referring to an internal short of one cell - the most likely failure. If one of the six internal cells goes bad, one battery will become a '10 volt' battery. As a result it will drag down the voltage of the others a bit. It would be interesting to see by how much - and if I could create some kind of monitor. If there is a sudden drop of 10% or more or something - you've given me an idea... but I'd need to find a damaged battery to be able to test properly...

[@ShaunDobbie]

I am wanting to make a 15kwh plus lifepo4 battery bank for my solar shed but can't find lifepo4 anywhere in the UK.

[@AdamWelchUK]

+Shaun Dobbie Good luck in you hunt - I've no tips I'm afraid, not something I've looked into.

[@ShaunDobbie]

I find lead acid inefficient and generally crap so I am trying to go to lithium as soon as possible.

[@AdamWelchUK]

That's understandable. I think if I was starting again (or didn't have a supply of lightly used lead acid) I'd have to seriously consider alternative chemistry.

[@ShaunDobbie]

***** Lead acid has the main advantage that it can be used in very low temperatures -10 and less whereas lithium can't charge below 0 degrees C. One other thing I don't like about lead acid is that it takes a huge amount of energy to manufacture, you will get twice as much energy out of the battery over its lifetime than was used to create it. With lithium it is 10 times more.

[@lm8012]

I have lots of lead acid batteries and i have had no issues with mine. I have Li ios and there is no way i would change from my lead to lithum. Everyone has there own requiements so i hope for can find a good source of lifepo4 cells. Mine are sealed not flooded like your Trojan batteries which requires more maintance.

[@trickyriky1]

arduino discharger, huge resistors, through a voltage splitter, could make for some nice graphs that would show their life cycle if you did it once a month or something :)

[@xanataph]

If a battery develops a shorted cell, the main issue will not be from the good batteries "dumping" into it, rather it will be when the charging is happening. It will gobble up most of the charge current and get rather warm, if the charging source is reasonably grunty. If you suspect a battery in this state: Check through the batteries with the clamp meter like you did but with NO charging or discharging taking place. You will find the duff battery when current is pouring in from the interconnects either side of it! (unless it's an end one, then all current will be moving towards it) Interestingly in this situation there is actually very little wattage moving around even though the current can be fairly high. That's because the voltage differentials are extremely low. As I might have said in the previous video of these batteries, no matter how you carefully manage things the batteries towards of the outlets of the pack will always take more of a hit than the ones in the middle. Many people believe that parallel=bad / series=good. Not necessarily so! An undetected shorted-cell battery in a series string is in many ways worse as it will cause the others to be overcharged, rather than undercharged in the case of the parallel pack. By the way Adam, thanx for your well-wishes. This will be the last comment I make for now. See you on the other side of these days! :)

[@AdamWelchUK]

Thanks for the insight Xan. Glad my video passed a few minutes for you in this odd waiting period (I remember it well - although we had ours booked in for a particular day)! I wanted to offer some suggestions on how to test everything live - but perhaps charging might have been a better option as you suggest. The issue is that we're having such an overcast, rainy few weeks I'm getting little significant current going in! I'm thinking about re-configuring my bank at some point - comments like your are always useful to make me think. Cheers and good luck once more.

[@Luke-san]

Nice wiring. Just a question, don't you need to place a fuse or even a switch as close as possible to the battery? Not sure how long the leads are or where they are heading to.

[@AdamWelchUK]

Thanks - I have a midnite solar rebranded CBI DC breaker on the main battery bank positive - and then my charge controller and inverter are also independently connected to DC breakers. All other small loads are individually fused. The main battery cables are less than a meter in length. Probably not much more than 2 foot before the +ve hits that breaker. I have all my fuses and breakers outside of the battery box - it shouldn't be necessary with the AGMs, but my previous 'sealed' VRSLA batteries could give off gasses if they needed to.

[@snakeplisken4278]

interesting! thanks for sharing. I am working on a solar installation for my boat. I want to keep the battery bank 12 V. There are 4 x 125ah agm batteries in my plan. is parallel connecting them the only option? each battery is 12 v.

[@ilsonbob]

Yes but you could balance them better than he has. Google 12v batteries in parallel

[@dtgoodwin]

Would testing them for current without a load indicate issues. They seem well balanced when delivering a load, but after charging or loading plus some time to settle, wouldn't any current flowing between batteries tell you more readily if one is unhealthy? I honestly don't know, but I have wondered that

[@AdamWelchUK]

Yes this is another good idea for a test - however again it requires taking the battery bank down to ensure no current would be flowing normally. Cheers

[@paulsengupta971]

2:05 milliamps not milliamp-hours... :-)

[@AdamWelchUK]

+Paul Sengupta Whoops - did I? Sorry.

[@John-gm8ty]

I had one of mine go back in a bank, didn't notice for a loooong time, pretty sure I did damage, and the rest of them have varied stable voltages ranging from 12.6v down to 12.5v. they all used to sit at 12.8v just a year ago. it pays to to monthly checks :/ luckily I got mine stupidly cheap and am only running led strips on a PWM controller, so it's not noticeable. but still, was a disappointing lesson. on the plus side, I have a new EPSOLAR LS1024B coming in the mail (eventually ha) which I can finally set up my 45 AGM 5ah batteries with (got them stupidly cheap in a UPS buy, the UPS was too massive to run at home ha)

[@AdamWelchUK]

Yes battery maintenance will save you money in the long run. I probably should have added that doing the same test whilst the batteries are charging will give you a good idea of their internal resistance. The issue here is getting a consistent charge long enough to test with a solar setup! Cheers

[@John-gm8ty]

the constant charge is easy here in Queensland Australia lol. with it's lovely 34-38c days, there is a LOT of sunlight to spare.

[@Shane-zh6tx]

So cool!

[@jeffmerlin2580]

Great video! Thanks! A big thumb up from me. :)

[@gmichaeld7963]

I like your instruments. But you can make your life much easier if you have a 'star' wiring instead of your 'ladder' or busbar wiring. One side is sufficient (+ or -) and the wires can be much thinner like 2.5mm2 . Now you can measure the same value in each wire and detect even the smallest difference.

[@AdamWelchUK]

Are you suggesting each battery connects independently to a central buss bar or something of that arrangement? Thinner wire required yes, but possibly a lot more of it! If I've got the wrong end of the stick could you perhaps find/make a diagram? Cheers for the suggestion.

[@gmichaeld7963]

Not that much to rewire.... _lh3.googleusercontent.com/aOIbSYYNSOidWgskBMTm1b_faBUzHLXEVTZvAPym4y9_qaD3jphL5ID3FpuL1RB5UCk5Q-qlFw_

[@AdamWelchUK]

Thanks for that. Yeah a couple of people have suggested wiring each battery individually back to a bus bar - I'm worried however that it is going to create a fair bit of extra cable in a relatively small space. It does give the advantage that I can wire individual fuses however and test as you suggest. I'll give it some thought again. Cheers

[@John-gm8ty]

it has it's own problems though, if one battery has a higher internal resistance and another lower, you won't get even charging. at least, from what I understand from BU discussion and articles.

[@alexandreesquenet3736]

I also use the star configuration on my battery bank, with a fuse on each + line. That way the cable resistance is about the same for all batteries (except the main one, i do not use a bus bar). I raise a little bit the voltage on float charge juste to make sure they all get charged well with the epever tracer A MPPT solar charger

[@MauroSedrani]

+Adam Welch Thanks for your video! I just made the same test on my battery bank :) It might be a good idea to design a circuit (maybe based on Arduino or ESP8266) which manages measurements with multiple non-invasive DC sensors. Why not! :)

[@AdamWelchUK]

Why not indeed! Sounds like an interesting idea.