2 4S LIFEP04 packs in parallel, 2 BMS's
- Thread starter wntrhwk
- Start date
sunshine_eggo
Happy Breffast!
You have heard wrong unless it was specific to the initial act of connecting the two batteries together. You want the voltage within 0.2V to prevent a surge that will potentially activate short circuit protection on one or both BMS. "take out" a BMS would be exceedingly abnormal. Once in parallel PROPERLY (see link #6 in my signature), should be no issues.
Good info Sunshine, thx. I had a BMS on one pack fail after discharging 30amps., guess I need to pay attention to my initial setup. Still kinda new to all the subtleties with proper battery configs.
Rednecktek
Solar Wizard
What Eggo said. Having batteries in parallel gives you two advantages. First it spreads the draw across dual BMS and battery sets so each one isn't having to work as hard, and second (as you've seen) if one dies you're not in the dark while you're trying to fix the system.
When you say the pack failed after 30a, like it smoked and died or just acted like it was dead? What happens if you try to charge it alone and run a load off it?
Always best practice to have both batteries charged to the same voltage before you connect them together or the higher charge battery will try to charge the lower battery all at once and can pop your BMS. Usually you can just throw them on a charger and it'll wake up the tripped battery and balance the batteries as they charge.
Rednecktek
Solar Wizard
Just out of morbid curiosity, when you unplug the balance lead jack from the BMS, what voltage do you get on the cell pack itself? Plugging the balance leads back in with more than 10v on the pack should reset/reawaken it. If that doesn't happen, hopefully a BMS swap is fairly easy.
Rednecktek
Solar Wizard
Huh, and not taking a charge? Hopefully the BMS can be swapped easily enough.
Azycray
New Member
I currently have 4 x 230Ah batteries in series. I'm planning on another 4 in series connected through a bus bar. Do I need to stick with 230Ah or could I jump up to 280Ah? Does it matter? Second question, where is the best place to connect my chargers? I have a plug in AC charger (that will only be plugged in when needed) and will be adding a charge controller with 1280w of panels to add charging to my bank that is connected to a Growatt 5000 ES. I currently have a 150a breaker on the first bank. Once there are two, I could drop down to 100a on each since the batteries can only handle 200a continuous but drawing from two groups of 4 in series would draw evenly so should be no more than 100a. Then a class T fuse for the total around 175a. For the charger connections location I'm thinking the negative goes between the inverter and the bus bar and same for the positive. Anything I said here sound like a bad idea? PS: I have an active balancer on the first bank and will put one on the second bank as well.
Rednecktek
Solar Wizard
You could parallel with 304's if you wanted to, you'll just lose capacity when the 230's run empty. Connect the charger to the bus bars where you connect everything else (batteries, SCC, inverter, etc) and you'll be fine.
Azycray
New Member
304's ? Are you saying when the 230's run out, that the 280's, even if they still have capacity left, will not deliver it?
Rednecktek
Solar Wizard
No, they will but by the time your 230's are empty, your 280's will only have 50ah of power left and can only output the amps for that BMS.
Think of it like this, you have a 230 pack and a 280 pack. When you've drained 460a of power it's like unplugging all your batteries and installing a 50ah single battery.
Think of it like this, you have a 230 pack and a 280 pack. When you've drained 460a of power it's like unplugging all your batteries and installing a 50ah single battery.
Azycray
New Member
Ok, not worth the extra cost to go with the 280's