Field fix to charge lithium battery

[solaar]

I have a small solar powered 60Ah LIFEPO4 battery I’m using as a portable system. I’m on the road at the moment and my panel has failed (it’s been playing up and there hasn’t been a solution for it, now it’s just unusable).

I’m wondering if as a temporary solution for a few days, it is possible to connect my starter battery to the charge controller (Victron 75/15). The alternator brings the battery up to 14.4 when charging and then drops to about 14.2. I have the charge controller set to 14.2V for the lithium. The problem I can see is that the CC will only take 15A and the alternator is going to be putting out a lot more than that, but will that current be passed onto the CC or will the CC just take what it needs?

Sorry if the question seems idiotic, there are significant gaps in my knowledge.

I have a few bits and pieces: wires, fuses, tools, jumper leads, electrical tape, connectors etc with me and can stir up a few other things from the local stores. I don’t really want to buy another panel right now though, it’s not the end of the world if I can’t charge the battery for this trip.

I’m curious anyway to know what would happen and what I’d need to make it work.

Thanks.

[Mike90250]

A MPPT controller "might" be OK. A PWM controller will pop it's internal fuse

[solaar]

Thanks Mike. So worst case scenario would be popping the fuse in the Victron mppt? Is it worth the experiment or could I damage my gear?

[Mike90250]

No. I said MPPT "Might" be ok. Morningstar MPPT would work, since they have a white paper about that.

Generally, MPPT seeks the max power point of the panels to charge with. If it doesn't need all that power, it "de-tunes" itself to a lower point on the power curve. But a battery or alternator is not a Current Source like a PV panel is, and so the controller will be unable to de-tune the power going to the battery,
Often, they fall back to a PWM mode and pop- there goes the fuse.

[Mike90250]

If it was critical to charge the battery, select a automotive headlamp, and use that in series from the vehicle to the battery. The light bulb will limit the CURRENT (amps) and allow the battery under charge to slowly come up to voltage. Expect 4-7 amps of current.
(only works with incandescent bulbs, not LED or Ion)

[Sunking]

PB and LFP use the exact same charger and voltages. Your LFP 60 AH battery is larger than your vehicle battery and can easily take its place.