Depleted Lithium leisure battery, could I part charge it from van's alternator

[Merc814]

I'm trying to gain some insight and discuss this in a practical sense rather than moving to the theoretical. I live full time in my RV with a solar set up. Through my own lax attitude I've run my leisure battery down to the low voltage cut off. Could I put my leisure battery (280Ah Eve cells, self built) in parallel with my starter to provide a functional charge for my battery without catastrophic damage?

We aren't talking about a permanent set up here or the fact that there would obviously be more efficient ways to charge. We are talking about a cold, dark environment that could be allievated by getting a bucket of amps into a battery! It wouldn't involve trying to get battery to 100%, but merely functional.

From reading around the two issues that regularly crop seems to be alternator overheating due to the low internal resistance of lithium batteries and voltage spikes due to a BMS shut down. In other places I've read paralleling with lead acid starter batteries can mitigate that.

Opinions? Real world tests?

 

[Merc814]

Forgot to add it is winter here and so solar is only a trickle at the moment.

 

[Merc814]

I also should have added my BMS Smart daly is limited to 75A charging. Another concern I am pondering.

 

[mikefitz]

Idealy you need a battery to battery charger to restrict the charge current to protect the alternator and BMS, fitted with suitable fuses and cable.

Since the lithium battery is discharged there may be a significant inrush if you connect to the vehicle battery. As an emergency measure use as long a length of connecting cable as possible to joint the batteries, poor quality jump start cables are a possibility. The idea is to add series resistance . Do this with care as there is a danger of overheating the cable.
With the engine running the alternator will limit at a current that may be in excess of the BMS 75 amp.
Again a long length or poor quality cable may reduce the current to acceptable values.

Of course all this is at your risk, and needs constant monitoring.

Mike

 

[Merc814]

Thanks for the reply. Yes have a clamp meter and can and will monitor that. Think I read somewhere else that using the van chassis would also help add further resistance.