Keeping 12V starter battery topped off with 24V RV battery

[RV10flyer]

All DROK products have held up well for me. This has 35mA idle current. 92% eff. Run 24V system voltage in, set your Amps and Volts output. It is not isolated like some of the Victron equipment, which is why I’m using a Victron isolated 24-12V 9A charger. Otherwise if you use common ground, then DROK will work. I would also install a 15A shotky diode on output positive.

 

[RV10flyer]

Another cheap option for $40!

 

[eXodus]

I replaced the factory 10watt solar panel they installed to 'maintain' the house battery - what a joke - with a 100w panel and a cheapo pwm SCC to maintain the chassis/starting battery. It's always fully charged.

100W panels are about a hundred bucks, and a decent pwm SCC about $35, and some wire and a breaker.

This is the only renogy item I have and it's been fine. A 10A 'waterproof' solar controller. LOL



If I were to do it again I would use a Trikl-start or similar, but they need a 12V source.

same here - I got a dedicated 12V trickle charge system with a 100W panel. It keeps the house and chassis batteries fully charged.
Pretty basic, not having much 12V draws.

Everything else runs over the 24V LFP system. - Inverter to 120V, and should the need arise I can boost the 12V with a 120V converter/charger which is just turned of these days.

 

[eXodus]

(I use a 12/24 to charge my house battery via my alternator)

which Orion 12/24 are you using? 10A 15A? I'm just thinking about adding one to my setup.

Currently the only ways of charging my 24V batteries:
1. Solar
2. 120V (Generator or Grid)

I'd like to add engine alternator - even if it's just topping of. Another layer of redundancy.

 

[RV10flyer]

which Orion 12/24 are you using? 10A 15A? I'm just thinking about adding one to my setup.

Currently the only ways of charging my 24V batteries:
1. Solar
2. 120V (Generator or Grid)

I'd like to add engine alternator - even if it's just topping of. Another layer of redundancy.

I have the 10A non smart and the smart 15A. It works great. Keeps my house battery at 27.0V. I installed a thermistor with conductive epoxy to rear housing of alternator and a 100A hall sensor. I try to keep under 75% of my alternator’s 110A capacity on my Express and under 90°C.

 

[eXodus]

So that you are running 25A @ 24V = that means 50A+ @ 12V

Yeah I can see that this would be getting close to capacity of the alternator when you also got the regular draws of the Van.
I got a Chevy Express drivetrain in my RV. Pretty familiar with the setup.

My 24V system has 900w Solar + 10 kWh - so I'm usually good pretty good with power - but would be great to add some charge while driving.

I've ordered a Orion 12/24 10A Smart those are significant cheaper then the 15A - I mean like less then half the price.
Going to test that.
Thanks!

 

[RV10flyer]

So that you are running 25A @ 24V = that means 50A+ @ 12V

Yeah I can see that this would be getting close to capacity of the alternator when you also got the regular draws of the Van.
I got a Chevy Express drivetrain in my RV. Pretty familiar with the setup.

My 24V system has 900w Solar + 10 kWh - so I'm usually good pretty good with power - but would be great to add some charge while driving.

I've ordered a Orion 12/24 10A Smart those are significant cheaper then the 15A - I mean like less then half the price.
Going to test that.
Thanks!

I did not like the 10A non smart because of the touchy voltage adjustment pot and over current. It would put out 15A at 27V or about 37A input. I replaced it with the 15A smart version. 6ga cable with 50A maxi fuse from fuse panel b+ under driver seat. Same here 1000Wp and 10kWh LFP. I installed a hall sensor on charger output with meter in overhead, a switch to turn off/on from drivers seat. I set it up to only charge to my 27V float. I also have a 24-12/9A to keep chassis battery at 12.9-13 after engine shutdown.

 

[eXodus]

I did not like the 10A non smart

apparently there are at least 4 different 12 - > 24V Orions

12/24 10A non smart
12/24 10A Smart
12/24 15A Smart
12/24 20A non smart

I also have a 24-12/9A to keep chassis battery at 12.9-13 after engine shutdown.

I don't do that, my chassis only charges from the 12V house batteries (Diode battery tender) - which are charged by a separate 100W panel or a 120V battery charger when plugged in.

I wanted to avoid a loop (12V - 24V - 12V - 24V and round it goes) in case some shutoff doesn't work and drains everything.

 

[mtts]

A 60amp Sure Power battery equalizer. Model 52206. Military surplus.

 

[GSXR1000]

Hi there, I’m wondering how I can keep my 12v flooded starter battery charged. I have a 24v lithium system for my camper van, and I’d like to top off the starter when I have capacity (or am charging, such as via shore power or solar). My first thought was to use a Victron Orion 24/12 charger (I use a 12/24 to charge my house battery via my alternator), but I’m imagining there has to be a cheaper way. I’ve seen small MPPT solar panel maintainers for around $80 and I’ve used my AC battery maintainer (which was around that much), so something about dropping $200 on the Victron makes me think I might be overthinking it. Does anyone have a recommendation for how to approach this problem?

On another note… if I were to splurge for the Victron, I’d love to power my 12V appliances as well (I currently have a cheap UXCELL converter), but in my mind it’s one or the other— charging the starter or powering my 12v appliances. That said, am I overthinking that as well?

Thread 'Using a MPPT as a battery charger?' https://diysolarforum.com/threads/using-a-mppt-as-a-battery-charger.41303/