2 Panels, 1 Alternator & 1 MPPT. How To?

[Trimglafix]

I need to wire up my solar panels to my motorhome leisure batteries.
I have a 160W permanently mounted panel that will be hard wired to my MPPT controller.
I will occasionally wish to add a portable 100W panel to the setup.

Can I connect this portable panel directly into the MPPT as well when required? I am unsure if this would cause problems with the MPPT as it will be receiving different voltages from each panel. Will problems possibly be caused by one panel feeding into the other? The manual doesn't specify how to wire up more than one panel.

The vehicle alternator will also be charging my leisure battery when the engine is running. Is that likely to cause a problem for the MPPT?

Any advice much appreciated.

 

[solarfred]

No you cannot connect different panels into the MPPT hence why there is no instruction. Either connect parallel or series panels of the same spec.
The charge from the alternator should not have any detrimental effect.

 

[Trimglafix]

Thank you solarfred. Timely reply; I was just getting itchy feet & readying to start wiring it in!
As alternator should have no detrimental effect I will just use my other panel as before. (i.e. directly to battery through its own controller).
Thanks again.

 

[solarfred]

It may be that when the alternator is charging the MPPT stops if it detects higher voltage across the batts. Once the engine is off the MPPT will measure battery voltage and charge accordingly if required. Having two different solar chargers may have an effect as each controller will pick up the charging current of the other via the battery so it may conflict. Not something I have tried/checked. My gut feeling is it will cause the controllers to get false information and may not charge accurately. AGM's need exact voltage measurement so best to monitor closely what is going on to see if the charging regime is correct.

 

[Trimglafix]

Thanks again solarfred. That all sounds logical. As long as the alternator charge regulator is not too quick to drop off the charging (which I assume they do when the battery voltage is high) then it makes sense that it will just take over & shut the MPPT off as you describe. I was worried they may "see-saw" between each other if that makes sense.
With regards the portable panels it sounds like I would be wise to leave them behind if they are likely to conflict. I will try experimenting before I go away but both time & sun are short!

 

[solarfred]

If you monitor battery voltage and it gets to target float then I would be happy the batteries are being fully charged between the two controllers. I don't think there is any danger of overcharging as the controllers would prevent that.