Should I buy golf cart lead acid batteries or Lithium iron ?

[englishman31]

Hi I have a small off-grid solar back-up system with 4 x 100W panels, MTTP,and 2 x 125AH 5yr old 12V deep cycle lead acid batteries. Batteries are still"good" under load test but don't hold up for even a day for home office if it's a cloudy day. Was thinking of buying new higher capacity batteries install a 2 way high current switch and put the old ones on trickle charge from the mains as a back - up. My question am I better off buying say a bunch of 12V100Ah Lithium iron at $300 ea from Amazon, or a bunch of 6V 270Ah golf cart batteries from my local store for $170 each ? I hear lithium iron are lighter and last a lot longer so wondered if anyone had any comments or tips regarding which would give me the best amp hours for my buck assuming I don't want to be replacing batteries eery few years.

 

[crossy]

If you have the $$$ and your charge controller can handle them (or budget a new SCC) it's LiFePO4 every time.

Longer lived and zero maintenance.

EDIT One thought, how cold does it get where your cells will live? Lithium do not like charging at low temperatures.

 

[Zwy]

Hi I have a small off-grid solar back-up system with 4 x 100W panels, MTTP,and 2 x 125AH 5yr old 12V deep cycle lead acid batteries. Batteries are still"good" under load test but don't hold up for even a day for home office if it's a cloudy day.

Have you performed equalization charge to equalize cells and desulfate? If these are true deep cycle batteries (not marine deep cycle/starting) then EQ will extend the life. If you cycle the batteries below 50% depth of discharge, you will kill the batteries over time.

Was thinking of buying new higher capacity batteries install a 2 way high current switch and put the old ones on trickle charge from the mains as a back - up.

You need to perform EQ and cycle the batteries several time with EQ to improve the health of the lead acid before using a trickle charger.

My question am I better off buying say a bunch of 12V100Ah Lithium iron at $300 ea from Amazon, or a bunch of 6V 270Ah golf cart batteries from my local store for $170 each ? I hear lithium iron are lighter and last a lot longer so wondered if anyone had any comments or tips regarding which would give me the best amp hours for my buck assuming I don't want to be replacing batteries eery few years.

It would depend on where the batteries are located. LFP will be damaged if charged below freezing so it may not be a good choice. LFP is great, no acid to deal with, no cleaning terminal corrosion, no water to add. Depth of discharge is much higher. Over time LFP is cheaper if cared for correctly.