Is there a need for separate engine generator?

[Boxster1971]

Originally Posted by avanti

On the narrow issue of solar charging the chassis battery in the case of a second alternator:
It seems to me that a Trik-L-Start or equivalent can be used in this (or, really, any other) configuration. It bridges from the coach to the chassis systems and appears capable of stealing current from the coach to maintain the chassis battery under any scenario I can think of. Cheap and easy solution to many problems.

I run a Trik-L-Charge along with a "dumb" (alternator-controlled) isolator. Seems ideal, except perhaps for the "disconnect when fully-charged" scenario, and I'm working on that.

From what I saw at the Advanced RV Fest - they are using a Trik-L-Charge unit to keep the Sprinter battery charged from their large lithium house batteries.

[gerrym51]

Booster- i do not know if roadtrek uses Balmar or another supplier. just that it works like this-i have no expertise

[Davydd]

Originally Posted by Boxster1971

From what I saw at the Advanced RV Fest - they are using a Trik-L-Charge unit to keep the Sprinter battery charged from their large lithium house batteries.

True, and I didn't know it. I found it on one under construction. It is in the passenger seat base as is a ton of speaker amplifiers.

[bikerbill]

From what I learned about Mercedes Sprinter electrical alternator and "brain" is the main ECU will change the output of the alternator based upon what the engine battery and engine systems need. Once you mix in the RV batteries you can and may "confuse" what the MB ECU is supposed to do. Keep them separate for charging and utilize one of several different ways to use the RV batteries to keep the engine battery topped off when the engine is not running.

[markopolo]

The most common practice with RV's is the single stock alternator charging both the engine battery and house batteries. Probably greater than 99% of Class C's and B's and a lot of Class A's.

I spec'd 100AH to 400AH house battery banks as part of the question but maybe it better applies up to 200AH or so battery banks.

I hadn't considered someone really running a 400AH battery bank down to 20% SOC and the subsequent charging requirement. You'd at least need a better than stock alternator for that.

[avanti]

Originally Posted by bikerbill

Once you mix in the RV batteries you can and may "confuse" what the MB ECU is supposed to do.

I don't believe this claim to be true. It's all amps and volts--that's all the alternator and its associated controls can see when it looks at a battery. When your isolator closes, it puts the coach battery in parallel with the chassis battery--making it in effect one bigger battery. The voltages will average and the amps will add. Even if the resulting "big" battery is much bigger than the system expects, the alternator will only output up to its maximum design current. As far as I can see, the "confuse the system" thing is a myth.

[gerrym51]

Originally Posted by bikerbill

From what I learned about Mercedes Sprinter electrical alternator and "brain" is the main ECU will change the output of the alternator based upon what the engine battery and engine systems need. Once you mix in the RV batteries you can and may "confuse" what the MB ECU is supposed to do. Keep them separate for charging and utilize one of several different ways to use the RV batteries to keep the engine battery topped off when the engine is not running.

Bikerbill-doesn't your CS e-trek combine both together. i was under the impression only the zion with engine generator kept separate. all other Roadtreks were combined-at least i thought