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Help with 352AH Li-Po battery case

You are a little off on the math. You only have 26 cells in parallel. 4.4 amp hour x 26 = 109 Amp Hour. Then you have 3 in series to get 11.1 volts nominal. 109 x 11.1 = about 1,200 watt hours. The 1C rate would be 109 amps. If these are the cells from Battery Hookup, I think they tested them to nearly 1C without a problem. So 100 amps is fine, I would not push much further for any long term, but a start surge to double might hold. Since you are only a 12 volt system, you could add one of those huge capacitors they put on car stereo systems to help feed the power amps. As long as your constant current stays under 100 amps, you should be fine. 1,000 watts is a lot of power. With the capacitor, you could pull a huge surge for starting a motor like the compressor in a refrigerator or air conditioner.

Perfect, thanks for the clarification! I will need to study up a bit more. I added the Daly 3s 100a smart bms to my cart, going to purchase it, since I am guessing it can peak to 150a-200a. It looks like you can adjust voltage cut offs, found some screen captures on one of their videos, so we will give it a try. And yep, these are Battery Hookup cells.

My plan was to use this as a backup generator for my house. On its first (and only use) I had it power multiple circuits and was maxing out the 1000w inverter. Thats of course until the voltage went too low and tripped all the bms's lol.

Here are the screenshots from the video. For anyone else reading this interested in the bms, it looks like amazon charges $27 shipping plus $78 for the bms itself. Found it on aliexpress on the daly store for $76 with free shipping and an accessory gift.

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I just realized Im missing a 3S balance connector.

Can i plug the 4s connector into this B6 and charge it as a 3s? I would hate to trip a bms after all this work :)

I would like to charge it up a little bit since all the cells are sitting at 3.05v - 3.06v currently. I dont know how long before my next parts will arrive and I am worried it will lose voltage and trip a bms

:EDIT:
I think the answer to the above question is no i cant. I tried plugging the 4s balance cable into the BatteryGO and it split one of the PCG voltages in 2! I am assuming the charger would be confused also. I assumed when I plugged the 4s cable into the BatteryGO it would just recognize it as a 3s. Since the 4th wire is just taped off. Confusing.

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You should be able to run it at 3S, just use the first 4 wires, and don't connect the 5th wire to anything. The 4th wire is not the pack total plus. Wire one is pack -, wire 2 is the plus of the first cell group, and wire 3 in the plus of the second cell group. Hope that makes sense.
 
Got it mostly back together. Waiting on the new charger, bms, and mppt solar controller to show up in the mail. Will update again after i (try to) fit all that in. Got it up to 11.5 volts currently, balancing right now.

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I am having an issue balancing the pack, not sure where to start troubleshooting.

Parallel cell group #2 is out of balance compared to 1 and 3 that always stay balanced together.

My top ideas:
Charger issue (new one in the mail)
Too much solder used (added resistance?)
Length of wire to bms or type of wire used causing incorrect readings

Here are some pics, been trying to balance it for 3 days.

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The high cell group is creeping down. What are you using to balance it? Is it just the BMS balance current? DO you know how much balance current the BMS is rated for? You could try connecting a light bulb to that high cell group. But if you do that, make sure to monitor it so you can get an idea how fast it is pulling it down. That is 109 amp hours of battery. If it has a 30 ma balance current, it would take something like 36 hours to burn off 1% of the state of charge. If you use a light bulb that pulls 1 amps, that would pull off 1% in just over an hour. Big difference. BMS says you are at 66% SOC, so you could pull an amp for 20 hours without danger.
 
@RyanAK - please tell me that's not the only multimeter you own!

Without sounding like a multimeter snob, for doing stuff like this, especially with Lipo (where unlike LFP, small errors in voltage setups can mean success or total disaster)

How do you know ANY of your voltage readings are close, in the ballpark, or totally off? You need a reference before you start tweaking voltages and settings all over the place. Especially using meters that may be totally off from each other.

Maybe that cheap multimeter is ok, but how do you KNOW?

All I'm saying is that your spending bucks on gear, but with DIY, spend just a little on tools. Like a Fluke multimeter. Doesn't have to be top-of-the-line, but not a gray-market import version either.

There are many GREAT low-cost multimeters out there. Pick one to make it your reference. My choice of Fluke is personal, mainly because I don't have to worry about "did I get a lemon?".

Like some others, I'm a bit freaked out by your setup. It would be a total shame if an overall system error of only 0.2v meant the difference between a succesful build, and a house fire.
 
This is a great thread for info on Lipo. I am also using Battery Hookup Lipo packs at 3.75 volts 5ah per pack. I want to be more conservative and build smaller individual batteries with 12vdc and 5vdc hookups to run small lights and charge technology.

I am looking at 4s4p or 4s5p with a decent BMS, pwm charge controller and AC power supply. These would be used in the house for emergencies. These could also be charged off my shops' solar system since I went all solar with it this year.

For now, Lithium is an experiment to find a good and manageable method of producing a battery that can then be used in the house in a parallel setup to handle the "need to be on" items when main power goes out. I have read a lot of info and searched for the necessary parts. Peoples horror stories resonate about how you can get in trouble real fast.

For example, Battery Hookup recommends that you don't solder these packs. Instead, use connectors to go pack to pack of make a buss bar that will take the bullet connector as a customer did on there projects page. That will be my route. Also considering splitting the pack and removing the BMS. Jury is out on that at the moment.

My parallel experiment will be 18650 batteries and the very familiar s/p packs everyone creates. That should be fun to do. My son is buying Prismatic cells as he has spare change. Fun times.

Rippersoftware
 
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