battery banks with different capacities

[terrango]

I have a 100ah 48v battery at my cabin and i am looking to expand.
I was planning on adding 16 230ah 48v battery bank in parallel.
Is there any cons to using 2 very different sized banks together?

I have a friend who is interested in buying my 100 ah cells.
My other option is to buy 304ah cells and just have one bank.

 

[MisterSandals]

Combining different LiFePO4 batteries with smaller capacity differences, in parallel in not uncommon but 100Ah with 230Ah may introduce more challenges that necessary. Consider the BMS current limits; are they similar? Consider charging the 230Ah battery at .2C; this would be nearly .5C for the 100Ah battery (what are your battery/cell limits?).

Since it sounds like you have a reasonable option to just go to 304Ah, I'd recommend that route.

 

[Brett V]

I'd opt for two more 100ah batteries and put all three in parallel

 

[cs1234]

Friends don't sell friends used batteries, especially custom built ones, unless they like providing free help all the time and/or losing friends.

 

[MisterSandals]

I have a 100ah 48v battery

Just out of curiosity, what battery do you have? Link?

 

[terrango]

I have just some cells bought from alibaba. They are EVE cells or so they say.
In my cabin i have 2 3000w growatt units working in parallel.

If i was to build a second 100ah battery bank, is it worth it to connect 1 battery bank to each inverter or just have them goto a main bus bar?
Right now i have a cheap busbar for the pos and negatives running to each inverter.
But i think i would need to upgrade it if i add a second battery or a bigger battery.
Just curious how well it works wired that way.

 

[cs1234]

Would you be increasing the load out of the inverters with these new batteries, or just lengthening the runtime? If you are just increasing the runtime, you just need to make sure to fuse / protect each battery before it enters the bus bar. Nothing else would need to change.

More batteries by themselves don't increase the amount of amperage used by your inverters. Only increased demand from the inverters would increase the amperage sent by the batteries.

 

[terrango]

I would just be increasing the runtime.

 

[timselectric]

Go for it.

 

[bdbugbee]

I have an 8S 24V 280Ah DIY battery in parallel with 3 x 24V 200AH LIFEPOER4 batteries from Signature Solar (22 kWh total capacity) and I have had no issues operating them in parallel for my home backup solar project. Just understand that the SOCs of the batteries will vary over the full SOC cycle by up to 10% in the middle of the SOC range. But by the time you get to the top/bottom ends of the SOC cycle, the batteries will migrate back to similar SOCs. Just make sure that all the batteries are attached and properly torqued to a common bus and not daisy chained. See my 6 slot rack mounted build in the attached picture. The three bottom slots are used by the 3 LIFEPOWER4 batteries. The two slots above that are used by my 280AH DIY battery and I use the top slot to mount a large DC circuit breaker (2x200A) on the output of the positive bus, a shunt on the output of the negative bus for the entire battery bank, a Victron BMV-712 display and a 12V output (thru a 24V-12V step down DC-DC converter) for charging devices. I use 2x1/0 AWG cables for both the positive and negative leads coming out of the cabinet with two 175A Anderson Connectors (350A capability with two cables in each connector) feeding a Victron Power In busbar on the wall. It's working well for my use case.

 

[jeantrot]

Friends don't sell friends used batteries, especially custom built ones, unless they like providing free help all the time and/or losing friends.

That is very wise advice indeed!