Lithium battery & alternator discussion

[Leonandlisa]

So I added the Renogy dc to dc charger, now how does my inverter/charger charge the coach batteries when not running?

I came out and the batteries are dead, inverter doesn’t feed them anymore. Any input would be appreciated.

[gpounder]

Originally Posted by Leonandlisa

So I added the Renogy dc to dc charger, now how does my inverter/charger charge the coach batteries when not running?

I came out and the batteries are dead, inverter doesn’t feed them anymore. Any input would be appreciated.

I am going to make some assumptions since I don't have all the information about your system.

A DC to DC charger is to take power from one battery to push it to the other regardless of the voltages of the supply battery.

But to actually make this work there must be an external power source such as solar or an alternator or being plugged in with the main charger/inverter being the supply.

I have and you may also have 2 DC to DC chargers now. The original one being the house battery to chassis battery unit, often the brand is a Xantrex Echo charger. So when you plug in the main charger spill into the chassis battery.

The second one which I think your speaking of should now take the chassis battery and charge the house battery. The power source should be the alternator. This charger should only be activated when the engine is running and there should be some way to make the charger turn on and off when your engine is running. If you leave it on without running the motor then you will drain the battery because there is no external power source.

Why do you have a dead battery, that is hard to say in a message. Your welcome to send be a private message and we can talk. Regards

[gpounder]

Here is a rough diagram.

[gpounder]

Lithium battery diagram

[Leonandlisa]

So this is a 2004 coachmen with caterpillar 3126 diesel,upgraded to lithium and then read the need to limit amount of charge to them from alternator, so added the DC to DC CHARGER to limit draw to 40 amps. Not thinking it through it since the starting batteries were no longer connected directly to each other, it allowed the starting batteries to drain down with accessories plugged into the dash. Need to allow a charge back to them which now I understand.

I also have a switch on my dash to turn on the dc to dc charger so I can control when it is on or off.

Thank you for the diagrams, I see where I can get this going now.

[evofxdwg]

Here is what I installed:
LI-BIM225

Pro:
1)Specs claim to properly limit current/charge time to Li battery bank and thus protect alternator.
2) Probably substantially cheaper than a DC-DC charger + install.

Con:
1) Requires some electrical knowledge to install, especially with more modern RV battery management devices. Replaces the chassis/house interconnect relay and requires proper interconnect of the emergency start switch.
2) No display or indicator to know it is actually working or what state it is currently in. (I added a Victron BMV-712 for this reason and state of charge monitoring).

Note: I currently only have a single 100AH Battleborne LiFePO4 battery. So I may not be truly stressing the alternator output.

[IdahoBen]

Originally Posted by evofxdwg

Here is what I installed:
LI-BIM225

Pro:
1)Specs claim to properly limit current/charge time to Li battery bank and thus protect alternator.
2) Probably substantially cheaper than a DC-DC charger + install.

Con:
1) Requires some electrical knowledge to install, especially with more modern RV battery management devices. Replaces the chassis/house interconnect relay and requires proper interconnect of the emergency start switch.
2) No display or indicator to know it is actually working or what state it is currently in. (I added a Victron BMV-712 for this reason and state of charge monitoring).

Note: I currently only have a single 100AH Battleborne LiFePO4 battery. So I may not be truly stressing the alternator output.

Thanks for the review. This is what I'm looking to go with... but a battery monitor has a higher priority on the budget list currently.

In the meantime I replaced the 200amp fuse near the coach battery with a 200amp breaker. So for now I disconnect the coach from the chassis battery with that breaker before hitting the road or plugging in/running the generator. I still need the coach battery connected to operate my slide (w/ the engine running) as well as my retractable step.