factory RV solar panels from 2000

[breezie]

Hello.
So I finally got my dream RV which is an Alpine coach 36 from the year 2000.
It came from the factory with a pair of 50W solar panels (in parallel) and a simple charge controller.

Here is my question/confusion.

As far as I can tell, the solar panels are connected to all the batteries together (house and chassis) which in turn use a battery isolator relay.

So when the vehicle is driving down the road, the solar charge controller is sending power to all the batteries.
How can that make sense when the two different types of batteries will have different charge characteristics?

What am I getting wrong here?

Did they wire them differently back then?

I want to upgrade the system a bit and I was thinking of getting a dual bank charge controller from Zamp.....but what do I do about the isolator relay?

 

[Gary RV_Wizard]

It makes as much sense as the engine alternator charging both battery banks, which is what the isolator is designed to do.  Or the house converter/charger doing both, which is also how many systems are designed (I don't know about Alpines).  While it can be shown in the lab that strictly following charge profiles can extend battery life, in real practice it's simply not a big deal. There are so many sub-optimal factors affecting RV use that it's all but impossible to assess how much (or little) any one thing affects it.

If you want to disconnect the house battery bank connection to the isolator relay (or just deactivate the relay), go ahead. You merely lose the capability for alternator charging of the house bank and rely on solar only while underway. That's mostly a consideration only when coming home from a off-grid campout.  You could insert a manual switch in the isolator relay activation circuit if you want to keep it available.

 

[Back2PA]

100 watts equals about 7 amps on a clear day at high noon. Most of the time you'll probably be under 5 amps; at that level, feeding two battery banks, you don't even need a regulator. To be honest, if you are considering upgrading your solar, I'd start from scratch - in my opinion it would be money better spent.

 

[breezie]

Thanks for the great responses.

Because I live in sub arctic Wisconsin, and won't be free to follow the weather for another couple of years (when spouse can retire and get medicare) I need to store this coach through the winter.
So, I was looking at solar as a multi-phase project.

Right now I just want to keep the batteries alive during winter storage with a solar trickle.

If I understand it correctly, while parked with the engine off, the solar trickle from the 2 x 50W existing panels (which need new wiring anyway because it's been toasted in AZ for 20 years) will ONLY be charging the house batteries. Is that correct?

So, maybe, for a short term winter solution, I should get a pair of those little inexpensive portable panels and put them on the roof. One clamped to the starting batteries, and the other clamped to the house batteries??just for a trickle charge.

Then, for phase 2, when I do the actual 800-1200W system on the roof, it sounds like I will need to reconfigure the isolator and get a dual bank charge controller and better batteries.

Thoughts?

 

[Gary RV_Wizard]

I have no knowledge of how the isolation and solar systems in your coach were designed, so cannot answer your question as to what gets charged when parked, solar or otherwise.

Many of the more upscale DPs have an "smart"  battery charge controller, aka BCC.  It monitors the voltage of both house and chassis batteries and closes the isolator relay if one bank is well-charged while the other is low.  Others have no automatic monitoring and leave it to the owner.

You don't need a fancy dual-battery solution for winter storage. A jumper cable will do (only the positives need be connected - they already share a chassis ground). Even the jumper can be simple, a short length of 10 gauge wire with alligator clips is enough for the low current involved. 

I'm dubious that you will get much solar charging during the Wisconsin winter months, even if you manage to keep ice and snow off the panels. Winter sun in the northern latitudes is weak at best and many days are overcast.