LifePo4 charging question (12V Actually!)

soram · 05-02-2026 07:26PM #1

A bit of a convoluted issue….not really house renewable but battery question anyway. (Edit - if more suitable to another forum please move as appropriate!)

I have a DIY 280Ah 12V Lifepo4 in my camper the last few years. It functions brilliantly and with the Victron inverter runs the toaster and kettle and sometimes the induction hob for a few days off grid. I have a solar panel but roof space is limited and I typically have a kayak shading it anyway so generation is typically limited.

I can manage longer trips off grid by not using the big consumers but then I use gas.

I have to buy a small generator for other purposes (thinking of a Honda EU 10) and was thinking of taking this with me on longer trips in the van. I would only use this to top up the battery but my inbuilt charger is limited to 20Amps (30Amps from the alternator)

So I'd have to run the generator all night to charge the battery which would be a PITA.

BUT ….. I also have a Hewlett Packard server power supply hacked to 14.4V output for BMW ECU programming. This can do 100Amps ish so 2 hours would be a big benefit.

The web suggests I can just connect this on to the battery in parallel with my inbuilt charger and let rip. The 280Ah cells should take 0.5C so good there too and 14.4V is a good voltage.

Am I missing something or does that sound feasible? I suppose I could buy and build in a separate charger but I don't really have space and it would only be for very exceptional circumstances. Any thoughts and recommendataions appreciated.

10-10-20 · 05-02-2026 09:45PM

In my opinion, flat charging like that with no current and voltage control, will result in a lower cycle life of the Lifepo4, which prefers no float charge and won't like sitting at 3.62v/c for any duration after it has fully adsorbed the charge.

https://www.batteryuniversity.com/article/bu-405-charging-with-a-power-supply/

https://www.batteryuniversity.com/article/bu-409b-charging-lithium-iron-phosphate/

I'd look at a LifePO4 4c BMS of some type to manage the cell and feed it with a slightly higher voltage and let it work it out safely.

soram · 05-02-2026 10:12PM

I wasn't planning on leaving it connected. Just boosting to maybe 75-80% under supervision and then disconnecting. Life cycle is not a huge consideration as we might be talking 20-30 cycles per year so I'd hope it would 'see me out'!!!

The battery is controlled by a JK BMS with balancer anyway. I just want to minimise the time the generator is running and utilise it most efficiently.

A bit of research after I posted first suggets a Victron Multiplus Inverter/Charger might be the job but it is expensive considering I already have the power supply and it is only for exceptions.

soram · 05-02-2026 10:26PM

Thinking a bit more however. Sometimes after a few days we arrive at a friend’s for a while. If we could get a good charge in an hour it would be great rather than having to ask to string a cable through their window all night. I might need it more than I first thought! I might need a bigger ‘boat’ (charger)!

10-10-20 · 05-02-2026 11:07PM

https://www.boards.ie/discussion/comment/124209781#Comment_124209781

Yeah, I get you. Let's see if others have experiences with LifePO4 and this charging method.

LifePo4 charging question (12V Actually!)

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