Using a lifepo4 to charge or jump starter motor battery

[solaar]

Is there any potential issue with wiring up a lifepo4 to a lead acid starter battery in parallel:

1. To give a top up charge to the starter in the case of the vehicle sitting for a while;

2. To charge up a starter battery too flat to turn the engine over;

and 3. To jump directly off the lifepo4?

I have a little portable 60 ah lifepo4 I use for various things, and would be great to just hook up the jumper leads every now and then to give the starter battery a top up. In the case of flat battery too, obviously this would be helpful.

Thanks.

[SunEagle]

Is there any potential issue with wiring up a lifepo4 to a lead acid starter battery in parallel:

1. To give a top up charge to the starter in the case of the vehicle sitting for a while;

2. To charge up a starter battery too flat to turn the engine over;

and 3. To jump directly off the lifepo4?

I have a little portable 60 ah lifepo4 I use for various things, and would be great to just hook up the jumper leads every now and then to give the starter battery a top up. In the case of flat battery too, obviously this would be helpful.

Thanks.

You may be correct. I have a "jump start" portable battery. While I believe it is AGM type I have used it to jump my car when it's own battery was too low to start it. So it may be possible to use different chemistry batteries to "jump" a vehicle's battery. But I do not think just using a parallel wired set up to keep an FLA battery "up to charge" is a good idea because both batteries will eventually discharge just sitting there.

[solaar]

Thanks Sunking, discharging won’t be a problem, the lifepo4 has a solar regulator attached, so I can keep it topped up with the panel on my trailer. I was more concerned with the FLA somehow damaging the lifepo4, but if that’s not a real concern then it should be ok. It’s not going to be an ideal voltage for the FLA, but it should at least be able to get a float level charge and figure that’s better than nothing. I live in the camper, so it all gets monitored very regularly.

[SunEagle]

Thanks Sunking, discharging won’t be a problem, the lifepo4 has a solar regulator attached, so I can keep it topped up with the panel on my trailer. I was more concerned with the FLA somehow damaging the lifepo4, but if that’s not a real concern then it should be ok. It’s not going to be an ideal voltage for the FLA, but it should at least be able to get a float level charge and figure that’s better than nothing. I live in the camper, so it all gets monitored very regularly.

Just remember that solar is never 24/7/365 so there will be some days the Lifepo4 will not be charged by the sun.

IMO if you really want to keep the FLA batteries charged then use a solar charging trickle system for them instead of the Lifepo4 batteries charging the FLA.

[Ampster]

I have a little portable 60 ah lifepo4 I use for various things, and would be great to just hook up the jumper leads every now and then to give the starter battery a top up. In the case of flat battery too, obviously this would be helpful.

I don't see an issue doing that temporarily. I agree with @SunEagle that the best arrangement would be to trickle charge the starting battery with solar. That way it stays topped up all the time.

[solaar]

Just had another idea: forget about the lifepo4 - I have a double cigarette lighter outlet near the front of my van coming from an AGM battery charged by solar at the rear.

Is there any reason I couldn’t just wire up:

Cig lighter male connector
to a length of 15 amp wire
to alligator clips

When I want to charge the starter battery I could just plug the cig connector in and clip to the battery, effectively making a parallel connection between the two batteries. Just not 100% sure about going through the load output on the cc.

I was avoiding using the AGM because I didn’t want to route more cable, but in the case of the cig lighter outlet, that job is already done.

[Mike90250]

If your car battery is low, it can suck a lot of juice from any jumper type battery. Most lighter sockets have a fuse in the vehicle fuse panel, often 20A. be ready to replace it,

[NewBostonConst]

Just had another idea: forget about the lifepo4 - I have a double cigarette lighter outlet near the front of my van coming from an AGM battery charged by solar at the rear.

Is there any reason I couldn’t just wire up:

Cig lighter male connector
to a length of 15 amp wire
to alligator clips

When I want to charge the starter battery I could just plug the cig connector in and clip to the battery, effectively making a parallel connection between the two batteries. Just not 100% sure about going through the load output on the cc.

I was avoiding using the AGM because I didn’t want to route more cable, but in the case of the cig lighter outlet, that job is already done.

I have used two of these small solar panels to keep two of my batteries topped of in a backhoe and truck for the last year. I got them off amazon.