Can't match some used batteries, BUT

[solaarone]

Can I not just use the two new batteries for six months while keeping the old ones topped up unused? Won't that match the old and new together fairly close? The load has been, and will be, the same throughout. I've just been charging them with house current.

I bought two of the trojan 6v to make a 12v, soon to be a 24v. But I couldn't afford the 2nd set of batteries til next month. I've been using the 1st set for the last six months. I don't need the 24v right away, but I can wait the six months.

[Ampster]

FLA batteries are finicky and your mileage may vary. Others may have better advice but I gave up on FLA 12 years ago and have not experienced those kind of issues using Lithium batteries. This may be a good time to do some research to decide what is the lowest cost way to change to a 24 volt system. Most of the people I talk with are convinced that Lithium batteries are the best long term value. But the initial price is a stumbling block for some.

[littleharbor2]

FLA batteries are finicky and your mileage may vary. Others may have better advice but I gave up on FLA 12 years ago and have not experienced those kind of issues using Lithium batteries. This may be a good time to do some research to decide what is the lowest cost way to change to 24 volt system. Most of the people I talk with are convinced that Lithium batteries are the best long term value. But the initial price is a stumbling block for some.

Building your own LiFePo4 battery bank with individual cells and BMS Can be actually cheaper than FLA based on USABLE capacity. I have recently built a 460 ah @24 volt bank for under $2,000.This gives you more than 400 usable amp hours. It would take 8 high end L-16 batteries to get that much power. Do the math. Also given the expected cycle life and lack of maintenance requirements it really is a no brainer.