Mixing batteries

[Borneoboy]

Can I mix 90 Ahr and 100 Ahr cells in my 24volt pack ?
Or will this just give me balancing problems ?
Alternatively, parallel 90Ahr pack with 100 Ahr pack ?

 

[timselectric]

Don't mix different cells into one battery. But different battery capacities in parallel is fine.

 

[Borneoboy]

Thanks for advice !

 

[Steve_S]

From one of my other responses.

A picture is worth a thousand words eh. I drew this up to make it a bit easier. Obviously, this is for a component system and not an AIO (All-In-One).

• Busbars used @ Battery should be rated for Maximum Current Potential. Avoid the cheapo deals on Amazon/E-Bay.
• Keep battery to busbar wire lengths identical, the Fuse is part of the length.
• If a Battery is capable of 100A but can do 200A surge output, fuse accordingly.
• Class T Fuses are preferred within their own holders. Alternatively, MRBF Fuses are quite acceptable
• Generally, a Smartshunt is used to monitor Power In/Out and the State of Charge of the battery bank.
• A Disconnect from the battery bank is prudent for maintenance work +.
• Solar Controller output should be fused to its maximum Amp Output (Too many forget this detail, req for inspection pass)
• A Separate Battery Charger if so equipped should also be fused for its Max Amperage output.
• Inverter/Charger also to be fused IE: a 4000W Inverter @ 48V would require 80A Fuse/Breaker. (#### Watts ÷ 51.2V = Amps) BUT remember that an HF Inverter can do 2X surge handling and an LF model can do 3X surge handling. (HF = High-Frequency, LF = Low Frequency)

* Fuses or DC Breakers will accomplish the same thing and allows some flexibility. Stick to Known Good quality components ONLY, this is one area where saving a few pennies buying cheapo offshore stuff can bite you really hard !

 

[rdhood]

Good post! I've been looking at different "system" drawings and deriving these rules, but uts good to see them written down

 

[Steve_S]

This is another simpler diagram from Midnite Solar. Note how the breakers are setup and it's done this way for safety & inspection compliance. There is a PDF Attachment, again from Midnite Solar with a lot more detail & explanations of things. Of course this applies to ANY Component Based system.