How to trickle charge starter battery from house battery set up?

[jdubbayew]

Add a Victron Inverter, some models have a dedicated trickle charge for starter batteries

 

[dstock]

I found this DC-DC Charger w/MPPT that functions the same as the Renogy 50a DC-DC w/MPPT that I already have except that it can handle up to 50 volts solar input, which would solve my issue with the 25 volt limited Renogy and my 32 volt panel.
https://www.donrowe.com/KISAE-DMT1250-Abso-50A-DC-DC-Battery-Charger-p/dmt1250.htm

However, it got me thinking, couldn't I just use my Victron 75/15 solar charge controller to limit the output of the panel and then feed it through the Renogy 50A DC-DC w/MPPT to keep both house and starter battery topped off? Would the Victron and Renogy fight each other? I know this seems convoluted but since I have all the bits already, just a thought.

 

[fratermus]

I found this DC-DC Charger w/MPPT that functions the same as the Renogy 50a DC-DC w/MPPT that I already have except that it can handle up to 50 volts solar input, which would solve my issue with the 25 volt limited Renogy and my 32 volt panel.
https://www.donrowe.com/KISAE-DMT1250-Abso-50A-DC-DC-Battery-Charger-p/dmt1250.htm

AFAIK the Kisae doesn't do the "trickle charge starter battery from house battery" thing.

It also doesn't do low temp charge cutoff natively, but can be tricked into it.

ouldn't I just use my Victron 75/15 solar charge controller to limit the output of the panel and then feed it through the Renogy 50A DC-DC w/MPPT to keep both house and starter battery topped off?

The manual says the DCC50S maintains "the starter battery via solar panels if the service battery is fully charged". It's possible that this is sloppy writing that assumes the service battery could only be charged to full with the engine off using the built-in MPPT.

If you test it please report back if full charge is sufficient to trigger starter batt maint, or if it requires PV input on the DCC50S itself to get the party started.

 

[dstock]

AFAIK the Kisae doesn't do the "trickle charge starter battery from house battery" thing.

It also doesn't do low temp charge cutoff natively, but can be tricked into it.



The manual says the DCC50S maintains "the starter battery via solar panels if the service battery is fully charged". It's possible that this is sloppy writing that assumes the service battery could only be charged to full with the engine off using the built-in MPPT.

If you test it please report back if full charge is sufficient to trigger starter batt maint, or if it requires PV input on the DCC50S itself to get the party started.

Bummer - my reply from yesterday didn't go through.

Well, there goes main reason for switching it out, I got so obsessed with solar input voltage I missed that glaring detail. Thanks for pointing it out!

I may give the Renogy DCDC a test if I can figure out how to test it easily without tearing my system completely apart. I am betting it needs the solar input to start the party. Agreed, their wording doesn't make it clear, nor does the website.

Honestly, the Victron DC-DC and MPPT controller are working great minus the trickle charge feature, it's probably not worth the over thinking at this point and I have a NOCO jump starter if for some reason things go horribly wrong with the starter battery.