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LFP in use. Old Lead acid bank switch ?

WoodsieLord

New Member
Joined
Oct 4, 2019
Messages
145
Location
Buenos Aires, Argentina (230V monophasic, 50Hz)
I finally got an LFP battery ( pylontech 100Ah ). I was using a lead acid bank (LOTS of small SLAs and a pair of GEL) heavily degraded ( around 480 Ah total from which I was able to pull 90~110 Ah ).
I would like to purchase more pylontechs but I don't think that will be possible for a year or two . Meanwhile, I would really like to attach the old lead bank to my system to take advantage of some extra Amp hours.

I've read a lot of threads about people that parallel their LFP with LA successfully and another bunch of people that say that's not a good idea. I'm really puzzled and I feel this like gambling.
LFP is EXTREMELY expensive here, meanwhile my Lead acid bank was almost free (mostly decommissioned UPS batteries). If paralleling is not a safe bet I'd rather keep from doing it.

I have a few fortek "100A" solid state DC-DC relays (which many say they're cheap garbage) which I could use to enable/disable banks so that they won't coexist while charging and discharging....

Does that make sense ?
What would you do in my place?
My ultimate goal is to have three pylontechs paralleled (300Ah LFP) at some point in the future. When that happens I would probably discard lead acid.

Thanks in advance!
 
I'm generally pretty flexible making compromises vs. best-practices if I know the outcome and am willing to accept the risk/consequences.

You already have an extreme case of battery bank absurdity, and you want to parallel a single LFP with a likely ludicrous number of deteriorated and varying capacity SLA/GEL.

If I've ever seen a worst-case scenario for paralleling lead with LFP, this is it. The only way it could be worse is if it's NOT 12V. If it's not 12V, setting your head on fire and putting it out with hammer is likely a more productive experience.

Most would likely indicate your SLA/GEL bank is a terribad idea by itself.
 
Get another 100A lifepo and start there. Junk the rest.
Figure out your charging profiles/processes. They just go and go and go. But if you don't you'll hose them quick.
Walmart took my old lead-acid batteries as a core charge. Gee, saved me $12. :)
 
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