Mix matched batteries discharge problems

[@rodneyslinger6316]

Just in the nick of time. I am intending to go pick up a second battery tomorrow. I was intending to get a different battery. Not the same as my first battery. However you have stopped me from making that mistake. I also intend to order a second 100 watt solar panel identical to the one I have now. Thanks for this video.

[@wr2956]

Great little setup you got going on. I got a 1kw inverter powered by 6x 110ah gel batteries connected in parallel. The charge controller and inverter + cables connected at one end of the bank and all the - cables connected to the other end of the bank. This is supposed to help for a more level discharge/charge across the batteries. You need cables big enough to handle the current from controller to batteries, my 40a epever triron is running the max size cables at 16mm and these need to be as short as possible to avoid charging voltage drop and at the battery end, up to 4 foot absolute max is recommended in the manual. One thing I have learnt is that to get best use of the sun and power, I need more panel watts than what I want to invert and use. If I want to run 1kw in the daytime and charge the battery bank too I’m gonna need at least 1500w of panel power to cope with that. My controller running 12v can handle 520w of panels and the manual says I can go up to 50% more, so 6x 130w panels 3 in series and the other 3 in series paralleled to get 780w. Now if I change to 24v I can double up the panel power with another 780w to get a potential of 1560w to get 40a at 24v. But then I need to double the batteries to keep up the same ah rating. Don’t get me started on the amount of batteries needed to avoid deep cycling them and seriously shortening their lifespan, that’s a can of worms for another day! All the best in your solar journey mate, it gets expensive!

[@Checkitfirst]

Thank you for the info. I only have 5x100 watt panels, 2 deep cycle marine batteries in series, 1500 watt 24v inverter. I have all my garage lights and a small fridge running on it right now. Debating on these new lithium batteries but they are expensive. I want to get away from that acid or at least marine batteries but they seem to work. I do have to replace them every two years though. They are $119 each which doesn’t break the bank like a lithium does. Overtime I do know it’s cheaper it’s just the initial cost that sucks😊

[@wr2956]

@@Checkitfirst just one pair of the lithium batteries will be not much better than a pair of your marine batteries, problem is you just don’t have enough batteries for your inverter. I read somewhere that at 12v you need 100ah of battery to cope with 150w of inverter, so 1000ah (or 500ah at 24v) to cope with 1500w of inverter, hence my 6x 110ah to cope with 1kw. (I plan on another pair soon to further reduce the load). This currently keeps my fridge and freezer running day and night and doesn’t go less than 12.2v. I can run a crockpot all day when the sun is shining so I can get a free hot meal at the end of the day too! The stats on my battery is that it can give 1.1amps for 100hrs (C100) making it 110ah. It can give 5a for 20hrs (C20) making it 100ah. It gives 8.9a for 10hrs (C10) making it 89ah. Then 15.4a for 5hrs (C5) dropping it to 77ah. Pulling 30a it will last for 2hrs making it 60ah. At 49a it will last one hour so 49ah. At 76.4a it will live for half an hour giving only 38ah so the more amps you draw the less ah capacity they are able to give. AGM are a good choice as they can cope a bit better with higher current draw, but you still need a good bank to share the load and not draw them down too low a voltage. Ever considered a good used electric forklift battery? Big deep steel tub of 2v cells, weigh around a ton, usually 48 or 60v, you can easily reconfigure them to 24v for a generous ah capacity. Good enough for a 24v 3kw all in one inverter charger with built in mppt to easily add more panels to the system, and you can easily hook up a backup generator to it for extra help if needed. Your inverter would just sip power gently from that bank and it should serve many years if kept well charged. If a 2v cell goes bad, you can change one instead of a whole bunch of 6 as in a 12v battery. Edit: if going for lithium just bite the bullet and go straight for 24 or 48v server rack batteries, one of those 48v ones (around 5kw/hrs) gives as much power as 16, yes you read it correctly, 16 of my batteries! I’m gonna shut up now and take a breath sir!

[@Checkitfirst]

@@wr2956 My understanding of led acid marine batteries is a 100 amp hour battery is really only a 50 amp hour battery. Can only use 50 % of it. Lithium 100 amp hour battery you can get a full 100 amp hours. That’s if I’m understanding this correctly. Been watching will Prouse videos. Not sure if I spelled that correctly or not🙄. He test a lot of those lithium batteries. But again I’m not sure if I’m understanding it correctly.

[@wr2956]

@@Checkitfirst hi bud, yes you are understanding correctly, that Will Prowse talks a lot of sense, done well for himself, I like his videos. If a 100ah battery is good to give 50ah to not deeply discharge it, so then it will be half of the capacities available from what my battery discharge info stated before. Many suggest to go no lower than 12.2v because any lower than that is considered damaging and reducing lifespan. Overnight if my fridge is pulling 0.3a at 243v that’s 72.9 watts, divided by 12.8v bank voltage = 5.69a so that brings one battery below the 20hr rating, divided that by my 6 batteries = 0.94a per battery which takes me over the 100hr capacity rating. In theory this should run for 50hrs to half depth of discharge. If my fridge and freezer run together it’s 0.7a x 240v = 168w, divide by 12v = 16.33a. On one battery that’s below the 5hr rating (2.5hrs to 50%) so won’t last long, divide 16.33a across 6 batteries = 2.72a per battery which is in the 24hr rate or 12hrs to use only 50%. A heater at 500w divided by 240v = 2.08a, 500w divided by 12v = 41.6a so for one of my batteries it’s the 1hr rating to flat so only up to half an hour to discharge to 50%. 41.6a divided across 6 batteries = 6.94a per battery, which then takes us within the 10hr rating so again 5hrs down to 50%. If you wanted to run 1500w from your setup, divide 1500w by 24v = 62.5a so with 2 of my batteries in series to make 24v it’s nearly at the 30min rate so 15mins to run 1500w to 50%. With my 6 batteries it would equal 3 strings at 24v, 62.5a divided by the 3 = 20.8a which is below the 3hr rating so up to 1.5hrs to 50% flat. If I had 12 batteries (6 strings of 24v) the current demand would be halved to 10.4a per battery which is in the 8hr rate so 4hrs to use 50%. So a quick refresh, my battery can give 1.1a over 100hrs (110ah) but if I wanted all the 110a (1200w load at 12v) it can only give it for 15mins, 110a x 0.25 (15mins) = 27.5ah and to use 50% is a measly 13.75ah capacity, so to demand big amps seriously reduces capacity, runtime and lifetime of batteries. Not enough batteries to share the load just kills them off quickly. My bank of 6 only dipped to 12.4v last night supporting the fridge and freezer and I have seen it down to 12.2v when there hasn’t been quite enough sunshine the day before. I’m no expert at this, but I’m getting there figuring it out!

[@Checkitfirst]

@@wr2956 You need to write a book 😂

[@DinoPasic]

I have same problem, im glad that i saw your video. I have same batteries 180ah, first four i got for free and preowner said that probably two are dead. I tryed it and it gets voltage so i used it all together but i don't have capacity, so i thought ok maybe its because of winter or mppt is not working properly. Before weeks i have bought another four used batteries, same type, and preowner used that without problems (he said). So i connected them with my old batteries but still i dont get any impressive capacity. So i think bad batteries are constantly discharging the good one's, so i need to check every each of them and then make good combination.

[@Checkitfirst]

That sounds like a good idea. You can try the desulfation, not sure if I spelled that right LOL. Charge each battery separately at 15.7 V for a couple of hours and they should start to fizz and it cleans off the plates give you a little bit more capacity from old batteries

[@DinoPasic]

I wanted also to add water if they are dry because i can open and inspect every cell. That are gel batteries. Ok, thanks for advice...

[@Checkitfirst]

@@DinoPasic Flooded only. I don’t think it will work with gel batteries

[@oscarapple1365]

Thanks for showing this.

[@williamwiese9963]

Great info!! I have a 660 CCA and 600cca and a 575 CCA batteries will the drain like yours did if I run them all parallel? I know they very a little bit but wasn't sure

[@texdoms]

The problem might come from the second battery which is maybe too old, and your first battery just empties it self into the second one. What you gotta do is equalizing them

[@SigmaWorksSW3D]

yes you got thing right... dont mix bateries unless they have the same original capacity like gc2-145 and Trojan-t145... they can be mixed if remaining capacity and resistance is almost the same

[@blackz06]

With zero voltage difference between the two batteries, internal resistance doesnt matter. I've ran a multitude of mix matched batteries without a problem. Current flow between the two is voltage difference times internal resistance. 0 voltage difference = 0 current flow. Make sure they're both fully charged and your problem should go away.

[@james10739]

Did you say $50 core or $15 I think it's usually like $12 or something