Add Lithium to Lead Acid Battery Bank

[Cuemaker]

A friend uses lead acid batteries for his solar system & wants to add lithium batteries to it.
I know it's a bad idea & I have tried to talk him out of it to no avail.
Just curious what will happen!
He has a 48v system with 3 banks of lead acid, 24 batteries total, 8 in each bank.
Going to add 48v 300ah lithium battery bank, all connected to the same buss bar.
Has anyone tried this?

 

[sunshine_eggo]

The LFP will do almost all the work. 80% of the working voltage of LFP is above the resting voltage of FLA.

The lead will be sitting there doing very little; however, due to their inefficiency in absorption, you'll need to recover about 10-15% more energy than the cap of of the FLA bank due to full charge.

 

[seneysolar]

Dont forget to disable any equalization charge feature or temp compensation that may be programmed into the CC for the lead acids. There will be very specific voltage settings for the LFP, the lead acids are just along for the ride now.

 

[bfitzgerald]

I have 16 L-16 batteries (4s2p) for 48v. Last year I added a 280 a/h LifePo4 diy battery to the common bus bars. I installed a Victron shunt on the lead acid bank so i could see, as mentioned here, the lithium does 99% of the work. It works so well that I added a 305 a/h lithium battery this year. I turned off the lead battery bank this year but maintain it as a backup to use before turning on the generator. I haven't used the generator since last fall.

The best part of this is the efficiency gain. The lithium batteries take all the amps that the panels and charge controller can generate. No current tapering until the batteries are virtually fully charged. Overall, my estimate is that I harvest 20% more power with the same solat array.

Brian

 

[sunshine_eggo]

I have 16 L-16 batteries (4s2p) for 48v. Last year I added a 280 a/h LifePo4 diy battery to the common bus bars. I installed a Victron shunt on the lead acid bank so i could see, as mentioned here, the lithium does 99% of the work. It works so well that I added a 305 a/h lithium battery this year. I turned off the lead battery bank this year but maintain it as a backup to use before turning on the generator. I haven't used the generator since last fall.

The best part of this is the efficiency gain. The lithium batteries take all the amps that the panels and charge controller can generate. No current tapering until the batteries are virtually fully charged. Overall, my estimate is that I harvest 20% more power with the same solat array.

Brian

Yep. Lead acid require about 15% more input to replace what was used, i.e., 100Ah used, 115Ah needed to replenish.