Solar charging the chassis batter while unplugged

[LondonLion]

RV -Solar charging the CHASSIS battery for a Sprinter ERA RV 70M while in storage/idle. i do not have access to shore power.

1. I have a solar panel on the roof om my 2018 sprinter era rv. It is a zamp solar charger model zs-30a.
Input: dc 12v max 25 volt
Output dc 12v 30 a

2. It charges the house (coach) battery when in storage.

3. It does not charge the main (chassis battery).

4. How do i use solar to keep the house/chassis battery from discharging when idle/in storage.

thank you!

alan collenette
[phone number removed]

[DavidM]

I am just beginning to deal with this on a new Thor Axis 24.1 with 150 watts of solar. It has a Precision Circuits BIM 160 that manages the connection between the coach and chassis batteries.

So far I haven't seen the BIM connect the two when the solar panels are putting out about 5 amps, their maximum this time of year. It could be that this BIM doesn't connect until the chassis battery is down to about 80% SOC. Or it could be that when it tries to connect with the coach batteries charging on float at 13.5 volts, the chassis battery puts too much of a load on that small 5 amps, the voltage drops and the BIM disconnects.

It would take a separate solar panel and controller dedicated to the chassis battery or a Trik L Charge would also do it. I am not too worried because my chassis battery is an AGM and they have very low monthly losses so I don't believe the chassis battery will discharge significantly. I also will go over to the storage yard and start up the chassis engine (which I just did) and let it warm up to circulate oil and recharge the batteries a bit.

David

[RVwithDogs]

I may be wrong but I don't know of any Sprinters that can charge the chassis battery from the house batteries without some modification. DavidM's suggestion about TRIK-L-START may be the way to do it.
Mega TRIK-L-START Starting Battery Charger/Maintainer

[imnprsd]

If you store your RV outside and have solar, your solar controller will take care of your batteries very well, but your water levels may need to be checked after 3-4 months. (Just a guess.)

I did this with 400W of solar, but that really does not matter. Your solar controller will only pass amps of current based on what your house batteries will accept.

So here's a general question, if my 400W of solar are capable of producing 20A of current, but my house battery will only accept 1A, where does all that extra energy go on clear sunny days?

...Is this why my MPPT solar controller has cooling fins? ...To dissipate the heat? ...If so what do the PWM solar controller do with the heat since they don't typically have cooling fins?

As to your question on how to get your solar system working to charge your chassis batteries? ...Easy. What I did is install a Keyline Voltage Sensitive Relay (VSR) which works like a battery isolator that connects ONLY the positive post of my house batteries to the positive post on my chassis-engine battery bank.

Keyline held the first patent and sells their products on Amazon in the $80-$100 range and my Keylike 140A VSR has worked flawlessly for 5 years now. And when I'm driving my engine alternator charges my house batteries so that when I arrive at my camp spot my house batteries are 100% SOC and that's great!

The Keyline VSR was one of my first and best upgrades I every did. I highly recommend it.

[BobC]

I've had good experience with the Amp-L-Start, which is Trik-L-Start's big brother.

[LondonLion]

Originally Posted by DavidM

I am just beginning to deal with this on a new Thor Axis 24.1 with 150 watts of solar. It has a Precision Circuits BIM 160 that manages the connection between the coach and chassis batteries.

So far I haven't seen the BIM connect the two when the solar panels are putting out about 5 amps, their maximum this time of year. It could be that this BIM doesn't connect until the chassis battery is down to about 80% SOC. Or it could be that when it tries to connect with the coach batteries charging on float at 13.5 volts, the chassis battery puts too much of a load on that small 5 amps, the voltage drops and the BIM disconnects.

It would take a separate solar panel and controller dedicated to the chassis battery or a Trik L Charge would also do it. I am not too worried because my chassis battery is an AGM and they have very low monthly losses so I don't believe the chassis battery will discharge significantly. I also will go over to the storage yard and start up the chassis engine (which I just did) and let it warm up to circulate oil and recharge the batteries a bit.

David

Thank you David!

I was looking at the Precision Circuits 00-10021-100 BIM with 225 amps (Chassis Battery) and 160 Amps (Coach aka House Battery)

As an amateur I am not clear on how to hook it up to my Zamp rooftop solar system, but it appears that is intended to caherge BOTH the chassis battery and the Coach aka House battery when the RV is idle for extended periods of time?

Any advice on hooking it up would be enormously appreciated.

Alan

[DavidM]

Alan:

Solar panels should always be wired directly to the coach batteries, not through a use/start relay for example. Then wire your BIM between the coach and chassis batteries using wire gauge capable of handling 225 amps. The BIM will connect the two or disconnect the two batteries based on its design.
I am a bit puzzled by your description of the PC BIM as being 225 amps to/from the chassis battery/alternator and 160 amps to/from the coach battery. There is a 160 amp model and a 225 amp model. You use one or the other.

David

[BobC]

Originally Posted by LondonLion

Thank you David!

I was looking at the Precision Circuits 00-10021-100 BIM with 225 amps (Chassis Battery) and 160 Amps (Coach aka House Battery)

As an amateur I am not clear on how to hook it up to my Zamp rooftop solar system, but it appears that is intended to caherge BOTH the chassis battery and the Coach aka House battery when the RV is idle for extended periods of time?

Any advice on hooking it up would be enormously appreciated.

Alan

The Precision site lists this as being discontinued. Do you need a 2-way BIM? If your MH is already set up to charge the house batteries while driving, you don't and the Amp-L-Start or Trik-L-Start is all that you need. Installation for either is very simple.