Parallel connecting mismatched batteries?

[zerzuri]

Hi!

I am a newbie here and have 8 260amp LifePo4 cells (WB-LYP260AH) Series connected them to make a 24v battery and have been using with my All-in-one MPP Solar 2424LV-MSD. Works great.

Recently I purchased 4 280amp EVE cells and intend to buy 4 more. My question is:
Once bought 4 more 280amp EVE cells, can I series connect them to make a 24v and then parallel connect them with my 260amp 24v battery to use with my PIP?

What would you do if you were in my shoes?
Thanks

 

[Supervstech]

If the new ones have their own bms, yes that should work fine.

 

[zerzuri]

Thank you for your prompt response.
Yes, I have a 80 amp BMS that I am planning to use once I purchased the next four cells.
Which brings me to the next question. Prior to parallel connect the two battery packs Do I have to parallel connect all 16 cells to balance or parallel connecting 8 similar cells with the same amperage separately?

 

[Supervstech]

I'm not following?
Why would you parallel the 16 cells? Are you top balancing prior to building the battery?

 

[zerzuri]

Yes I was thinking to top balance the cells but I am not sure how to do this whether I should connect ALL 16 cells in parallel or put together the same 8 EVE cells top balance them and similarly put together the other 8 group of cells and top balance them.

 

[Supervstech]

I would keep the capacity cells separate.
Do two 8packs

 

[zerzuri]

Sounds good. Thank you again. You are a great help.

 

[Steve_S]

Top Balance your 260AH cells and build them into a pack with BMS & Fused and do the same for the EVE-280's. Make sure that when you wire them in parallel you use the same lengths of Battery Cables to the busbar from each battery pack. The AH difference between the 260 & 280 won't present any problems when charging or discharging.

BMS Note:
Each battery pack should have it's own 8S BMS and be fused as well.
Each pack should be able to handle the full Discharge & Charge potential of your system, so the BMS' should be sized accordingly for Amperage Handling.
When choosing a BMS, it is highly recommended to ensure it has the capacity + room to spare. For FET Based BMS, generally 25% above your max load is suggested. So if you are going to pull 100A go for 125 or better 150A. Also typically FET based BMS only take 50% for Charge Input handling. BMS' which use Relays/Contactors rely on those for the rating capacity handling most often in systems that use 250A and higher.

Hope it helps, Good Luck.
Steve

 

[zerzuri]

It does. Thank you so much again.