Question: Is it possible to use a manual transfer switch or relay to swap the input & output of a DC - DC charger, in order to charge a starter battery from a house battery? sketch attached that I hope shows what I mean
This could be accomplished with:
- a switch like this (most are AC rated...would this be ok for 50A 12V?)
- a couple automotive relays
- a single DPDT relay like this (though I don't love the idea of always charging through some no-name amazon relay)
And a way to manually switch the charger on (in normal operating config it will automatically sense engine running). This can be done with an L-H jumper, H pin > 3V, or L switched to ground.
Any obvious reasons this will not work? Better suggestions of hardware to accomplish this?
Why:
I'm switching my van's house battery to lifepo4. The current setup has lead acid house batteries:
- charged directly from the alternator via a Blue Sea Automatic Charge Relay (parallels starter and house banks when either > 13V)
- and manual battery switch that directly parallels the house and starter batteries, allowing me to jump start from the house batteries if needed
I plan to use a Victron Orion 12-12 30A non-isolated DC-DC charger to charge the new LFP battery from the alternator. I would love to retain some way of starting/charging the starter battery from the house bank if I accidentally kill the starter.
An alternative is to use a battery switch to parallel the house and starter banks (bypassing the DC DC charger) and have a less controlled charge. The OCD part of me likes the idea of using the existing charger...I don't mind waiting a little while for the starting batt to charge.
This could be accomplished with:
- a switch like this (most are AC rated...would this be ok for 50A 12V?)
- a couple automotive relays
- a single DPDT relay like this (though I don't love the idea of always charging through some no-name amazon relay)
And a way to manually switch the charger on (in normal operating config it will automatically sense engine running). This can be done with an L-H jumper, H pin > 3V, or L switched to ground.
Any obvious reasons this will not work? Better suggestions of hardware to accomplish this?
Why:
I'm switching my van's house battery to lifepo4. The current setup has lead acid house batteries:
- charged directly from the alternator via a Blue Sea Automatic Charge Relay (parallels starter and house banks when either > 13V)
- and manual battery switch that directly parallels the house and starter batteries, allowing me to jump start from the house batteries if needed
I plan to use a Victron Orion 12-12 30A non-isolated DC-DC charger to charge the new LFP battery from the alternator. I would love to retain some way of starting/charging the starter battery from the house bank if I accidentally kill the starter.
An alternative is to use a battery switch to parallel the house and starter banks (bypassing the DC DC charger) and have a less controlled charge. The OCD part of me likes the idea of using the existing charger...I don't mind waiting a little while for the starting batt to charge.