Best ways to charge house and chassis (engine) batteries in an RV

[WorldwideDave]

Diesel RV (motorhome). 170 Amp alternator. Also has large (8kW I think) Onan diesel generator on board.
I am adding solar to it. I have several Victron MPPTs and solar panels to use/choose from, and there is already a 2000 W inverter on the vehicle that works that I will likely replace. I will also add Cerbo GX and a Smart Shunt 500A as well.
Before I decide what equipment to put onboard, and before I decide if I am keeping the house system 12V or upgrading it to 48V, I need to know the options I have to charge the house batteries & the chassis battery.
I don't believe the A/C will run (roof mounted) without the 50A shore power. I may change this by going big battery and a quattro inverter. I might not. Unsure.
But I do need to know what the best way to charge the batteries will be.
For example, I know that using the sun to charge the house batteries is the most quiet and efficient, but not the fastest way.
I believe the large diesel generator will also charge the batteries, but not sure if that is smart vs. starting the RV's engine and using the alternator.
Some have said to buy a small portable generator that are quieter and use less fuel.
To be honest I was a bit surprised the generator used diesel and not propane, which the RV has for heat and hot water and I think the refridgerator too.
I was considering getting an Orion DC to DC charger, but won't decide on that until I know if I am going to go with 12V or do 24V or 48V. Sounds like the Orion product released in November 2024 (the XS?) does 50A but only works in a 12v/12v configuration so far. People seem to like that device, but warn it could fry my alternator if the vehicle is not moving or going up a hill or something.
Open to thoughts/suggestions. Thanks!

 

[kbeefy]

The chassis batteries already charge off the engine alternator. Don't mess with that.

Your house battery charge options will depend upon your choice of house batteries.
Bear in mind that if you upgrade your house batteries, you might not need to charge them as much, depending upon your length of stay.
I went a bit overkill in my campervan and can stay 5-10 days without any supplementary charging. I haven't stayed longer than 4 days yet.

I doubt a 50A DC-DC will damage your alternator, and can't see how a hill would have anything to do with it.
You would only need a DC-DC Charger if you decide to go with LiPo or higher voltage house batteries.

Your diesel powered generator is ideal, if maybe a little noisier than a smaller unit. Diesel has far more power than propane or gasoline, and you have a much larger amount of it stored on board. Using it or any other generator would be better than starting the coach to charge off the alternator.

 

[WorldwideDave]

I think some have added multiplus II or quattro devices so they can run at least one A/C device at a time, then turn OFF the factory/OEM installed inverter the RV comes with. Saw that in a video last night.
I also see where some people use the cerbo GX to turn on and off the Orion device while driving down the road. others use a solenoid that supports high current to kill the flow. Something about idling the engine and just having the alternator pump out 50 A is not good for the alternator.

Of course the batteries would be LiFePO4 and not any other chemistry.

 

[kbeefy]

I also see where some people use the cerbo GX to turn on and off the Orion device while driving down the road. others use a solenoid that supports high current to kill the flow. Something about idling the engine and just having the alternator pump out 50 A is not good for the alternator.

Is that to stop the 50A draw from the DC-DC charger?

If so, then there is a trigger wire on my DC-DC charger for that purpose. No need for any additional components. There is also the option to run it at 1/2 capacity. In my van I have it hard wired to come on at 1/2c (20A) after my glow plug circuit shuts off and the battery voltage rises above 13.8v, then I have a switch on the dash to enable full charge (40A, in my case) if I want.

 

[WorldwideDave]

Is that an Orion?

 

[kbeefy]

Nope, El cheapo renogy

 

[S Davis]

You can adjust input and output on the Orion 12/12/50.

 

[WorldwideDave]

You can adjust input and output on the Orion 12/12/50.

View attachment 273716

What does the voltage lockout function do? Is that when the alternator is out putting a voltage that is too low the charger will not function?

I have been looking at the various Orion products and it seems everybody likes the form factor and the lower heat of the one they released late last year. I don’t know if they are going to do a 12 to 24 or any of those other types of buck boosters.

 

[WorldwideDave]

The chassis batteries already charge off the engine alternator. Don't mess with that.

Your house battery charge options will depend upon your choice of house batteries.
Bear in mind that if you upgrade your house batteries, you might not need to charge them as much, depending upon your length of stay.
I went a bit overkill in my campervan and can stay 5-10 days without any supplementary charging. I haven't stayed longer than 4 days yet.

I doubt a 50A DC-DC will damage your alternator, and can't see how a hill would have anything to do with it.
You would only need a DC-DC Charger if you decide to go with LiPo or higher voltage house batteries.

Your diesel powered generator is ideal, if maybe a little noisier than a smaller unit. Diesel has far more power than propane or gasoline, and you have a much larger amount of it stored on board. Using it or any other generator would be better than starting the coach to charge off the alternator.

Thank you I am looking at the DC to DC charger for that purpose. It will most likely be Victron Orion 50 A model.

One of the problems I have right now is that my chassis battery is dead. You’re saying not to mess with that because the alternator is supposed to keep that charged. Well, they are lead acid, and they are dead at 11V. Open to suggestions.

 

[kbeefy]

Thank you I am looking at the DC to DC charger for that purpose. It will most likely be Victron Orion 50 A model.

One of the problems I have right now is that my chassis battery is dead. You’re saying not to mess with that because the alternator is supposed to keep that charged. Well, they are lead acid, and they are dead at 11V. Open to suggestions.

Is it dead from age and neglect, or did something kill it?
If it's dead from a drain fix that first. Then consider disconnecting it before long periods of storage.

If price is not an issue I'd replace them with the AGM equivalent.

 

[Aussieguy]

get rid of the alternator charging of the house... just disable however they put the batteries in parallel
BIM or some other solenoid switch ... disconnect control wires

If you camp for many days ... when you add solar .... use ONE panel with it's own controller to keep the chassis battery charged
on driving days the alternator will still charge the chassis

solar... fill the roof and get as much solar as possible
whether you go 24v or 48 v is dependent on size of the solar
if you go more than 1600w of panels than increasing the voltage makes sense

otherwise 2 strings 100/50amp controllers also makes sense as you put one sting at front the other at rear, helps in limiting any shading

1 x 200w panel + small controller for chassis
1000w panels (or more) for house

If your motorhome has HIGH skirting to hide the roof obstructions
have seen people use this to add rails for panels so they can go ABOVE a lot of the smaller stuff , like vents

use residential panels if you can ... On my trailer I fit 2 x 370w (37v x 10a) string ONE
can add string 2 ... if I ever need it 4 x 200w panels tetris style around the skylights and vents


If you camp in poor solar spot... use generator at end of the day to top off the batteries
YOU DO NOT have to top off the batteries EVERY DAY

If you don't want to add a solar panel for chassis... you can use a small battery tender to the chassis

IF your chassis/starter battery does go flat...
simple matter to use jumper cables or reconnect the BIM
5 minute job to re-attach the BIM wires ..... most of the time is spent looking for the tools!
just let the house send power to the chassis for a few minutes , then try starting

or buy the dc-dc charger for the alternator charging
Just like boats ... you always busting out another wad of cash for RV stuff

 

[WorldwideDave]

Is it dead from age and neglect, or did something kill it?
If it's dead from a drain fix that first. Then consider disconnecting it before long periods of storage.

If price is not an issue I'd replace them with the AGM equivalent.

Sitting 3 months. No kill switch. Will add one. Considered 100/20 SCC to keep it charged up.

 

[WorldwideDave]

get rid of the alternator charging of the house... just disable however they put the batteries in parallel
BIM or some other solenoid switch ... disconnect control wires

If you camp for many days ... when you add solar .... use ONE panel with it's own controller to keep the chassis battery charged
on driving days the alternator will still charge the chassis

solar... fill the roof and get as much solar as possible
whether you go 24v or 48 v is dependent on size of the solar
if you go more than 1600w of panels than increasing the voltage makes sense

otherwise 2 strings 100/50amp controllers also makes sense as you put one sting at front the other at rear, helps in limiting any shading

1 x 200w panel + small controller for chassis
1000w panels (or more) for house

If your motorhome has HIGH skirting to hide the roof obstructions
have seen people use this to add rails for panels so they can go ABOVE a lot of the smaller stuff , like vents

use residential panels if you can ... On my trailer I fit 2 x 370w (37v x 10a) string ONE
can add string 2 ... if I ever need it 4 x 200w panels tetris style around the skylights and vents


If you camp in poor solar spot... use generator at end of the day to top off the batteries
YOU DO NOT have to top off the batteries EVERY DAY

If you don't want to add a solar panel for chassis... you can use a small battery tender to the chassis

IF your chassis/starter battery does go flat...
simple matter to use jumper cables or reconnect the BIM
5 minute job to re-attach the BIM wires ..... most of the time is spent looking for the tools!
just let the house send power to the chassis for a few minutes , then try starting

or buy the dc-dc charger for the alternator charging
Just like boats ... you always busting out another wad of cash for RV stuff

Great reply thanks. I have many 200w panels available and a lot of space on flat roof. Shouldn’t need rails. Was thinking 150/80 MPPT with 2 series 3 parallel for 6 house plus one 200 for chassis and a 50 amp dc to dc.

 

[WorldwideDave]

Also I will find drain on chassis battery first. Hopefully small. I’ve recently had to do this on my classic cars. Similar process.

 

[HRTKD]

My Multiplus 12/3000 would run my Coleman Mach 15 air conditioner off of my LiFePO4 battery. How long depends on how many Ah you have in the battery bank and how much solar is available.

I have an on-board generator. Once I get my system dialed in, the generator doesn't get used much.

My new trailer has a 48 volt battery because I put 1700 watts of PV on the roof, with plans for 850 more watts. If I had put on less PV I would have stuck with 12 volt or maybe 24 volt. If the RV is already 12 volt, it's a lot easier to stick with 12 volt.

 

[WorldwideDave]

. If the RV is already 12 volt, it's a lot easier to stick with 12 volt.

I am finding this to be true. and cheaper.