DC to DC Chargers to charge starter battery after the house battery with the alternator off?

[icyroads]

Are there any DC to DC Chargers that will charge the starter battery once the house battery is charged while the alternator is off?

 

[time2roll]

Is everything 12 volts? Probably just need a combiner.

http://www.lslproducts.net/UTLS_FAQs.html

 

[icyroads]

Is everything 12 volts? Probably just need a combiner.

http://www.lslproducts.net/UTLS_FAQs.html

Thanks. It says that it tries to keep the starting battery 0.2 volts below the house battery.
There’s no mention of low voltage protection, so I’d be a big concerned about running down the house batteries to the point of having nothing usable if a load was left on (I’m not worried about damaging the batteries, just not having enough left to rescue from the situation).

 

[time2roll]

Yes the low voltage protection is probably too low. Disconnect is 12.8 and reconnect is 13.0 as it is designed for FLA.

 

[12VoltInstalls]

says that it tries to keep the starting battery 0.2 volts below the house battery.

In boats, we just keep the starting battery(batteries) holy and sanctified. For offshore/great lakes often there are two starting batteries- one as backup due to the redundancy for life safety purposes. Then all systems/lights/vhf/radio are run on a separate house battery system. Because a dead starting system can be life threatening on big water.

That’s how you should set up.
The starting battery should never get depleted because you don’t use it parked.
A 30A 120V charger is “inefficient” but could be carried if house batteries are not the same voltage as the starting system where jumper cables could be used.

You can still have door switches run courtesy lights- just power them from the house batteries not the starting batteries.

Are there any DC to DC Chargers that will charge the starter battery once the house battery is charged while the alternator is off?

Yes, you could use one but I would not. I’d rewire to sanctify the starting battery.

 

[time2roll]

Ok here is another option...

Renogy DC-DC charger has a signal wire for the ignition. This signal could be controlled by a voltage controlled relay board.

https://renogy.com/12v-20a-dc-to-dc-on-board-battery-charger/

https://www.ebay.com/itm/383760514786

Forget the wire diagram. Battery to the battery terminals, signal wire through the relay. Voltage is adjustable.
And yes I have this relay board for something else and it works. I assume any DC-DC charger would work if it has a signal wire control.

 

[dirt diggler]

To do this i have in the past just used a VSR and wired it up backwards then as the house battery is charged via solar it switches on and charges the starter battery, IF that is they are the same chemistry ?
Although now i use DCC50s which does it all (solar controller and BtoB and reverse BtoB) the prev VSR worked fine though.

 

[icyroads]

To do this i have in the past just used a VSR and wired it up backwards then as the house battery is charged via solar it switches on and charges the starter battery, IF that is they are the same chemistry ?
Although now i use DCC50s which does it all (solar controller and BtoB and reverse BtoB) the prev VSR worked fine though.

Thank you, that is reassuring. I found the DCC50S as well, and I’ll give that a try first. If for some reason I find that I that I need a boost to start the van on anything other than an extreme and unusual scenario, then I’ve probably done something wrong. For the extreme and unusual scenario, I might install a manual “get the van started no matter what” switch, or maybe a high amp relay with a hold-to-engage push button remote trigger.
First though, I’ll just see if I need it — even without it, it is bound to be better than what I have now (ie no house battery system at all).

 

[dirt diggler]

My ambulance has a jump button, it just manually engauges a solenoid, the same one the conversion builders used for the ambys split charge system, but in my case i have a seperate ambulance systems battery for this and it's the same chemistry as the starter battery, no good if your 2nd (house) battery is a lithium, which mine is hense the DCC50s (i have 3 battery systems, total overkill but it came with the amby)

 

[icyroads]

My ambulance has a jump button, it just manually engauges a solenoid, the same one the conversion builders used for the ambys split charge system, but in my case i have a seperate ambulance systems battery for this and it's the same chemistry as the starter battery, no good if your 2nd (house) battery is a lithium, which mine is hense the DCC50s (i have 3 battery systems, total overkill but it came with the amby)

Probably fine with lithium for me: turn on the glow plugs, push the button to join both battery systems, engage the starter once the glow plugs are hot enough, let go of the button once the engine is started — there’s no “high” voltage going to either system for long enough, if at all.

Still, I’m going to wait and see if I really need it.

 

[meetyg]

The Victron Orion Tr Smart can be configured with a cutoff voltage for input.
So let's say the starter battery is at 13.6v when alternator is off, you could configure it to continue charging your house battery untill let's say 13.2v