RV-Additional Lithium Batteries?

[LarryD]

I have 1120 Watts of Solar and 300 AH of Lithium batteries at (2 each 150) that I installed last summer. Battery AH was limited by the space of the existing batteries. I am thinking now that maybe I could put a couple more batteries somewhere else. Conventional wisdom says that you should not add different age, size, mfg of batteries to a system but I see WIll does not think it is a problem. Does anyone have an experience with this? Thanks

 

[Rocketman]

From what I have read and seen on this site… (yea - so no real experience)…

For lithium it is fine as long as the batteries have the same charging profiles (don’t mix different chemistry- and don’t mix a 15s with a 16s battery).

A year or two in age won’t matter much at all. This biggest concern (which probably can’t be helped), is mixing short battery cables (your current set) with much longer battery cables (the new set). You may/will lose a little with that- it will probably work the old battery a little harder… but I would still do it.

You may want to think about fusing each battery- if the long battery cable runs through and shorts without fuses - that would be very bad.

Good Luck

 

[Reed Cole]

I would consider either lengthening the cables of the existing batteries to match what new ones would be so the batteries are charging/discharging the same amount or, if the distance is significant, using a combiner switch and operating two separate battery banks.

 

[Rbertalotto]

"combiner switch"....Can you explain or lead me to an explanation of what this does and who makes one?

 

[0truck0]

Another option, that is more complicated, is to separate into two electrical systems.
Separate the solar also, so you would need another charge controller....
Put one system on the big load, and the other on the rest. For example, I have one battery on the DC compressor fridge, and one battery on the coach (everything else).
I also was unsure of mixing batteries having bought the same one a year later. I like this as there is no way to deplete the battery the fridge runs on by running lights, fans, tv etc.
Also, like you, my second battery is at the opposite end of the trailer. I can put them together but this adds tongue weight and would take up prime real estate in the cabinet.
Interesting thing for me is that the everything-else battery gets run down faster than the fridge battery.

I added a breaker switch so I can electrically connect the two positives if needed. The fridge battery is connected to the alternator also, so when driving I do have option to charge both batteries together. I have never needed to yet. I have never charged off the alternator since the solar is always enough.

 

[eXodus]

Conventional wisdom says that you should not add different age, size, mfg of batteries to a system

Most of that only applies to LEAD batteries.

LFP can be from different manufacturers and age. But their size should be similar - otherwise they charge at different rates.

So in your case - add another 150A or two. You can connect them with a substantial wire and could be further away if you charge rate is low enough (less then 0.5C)

 

[Vigo]

I have 1x80ah, 1x100ah, and 2x140ah lfp all paralleled hideously in my rv and it is fine. As far as i can tell, the only time it really matters that your path resistances be similar (path being battery + cabling) is if you charge or discharge at high C rate. If you dont do that the paralleled batteries will ‘self level’ adequately. Thats been my experience.