100W Standard Panel Use?

[Moto GBR]

I have installed a 300w solar panel along with a Victron MPPT controller plus 280ah lithium Fogstar to my Bessacarr. I disconnected the factory fitted 100w panel along with the standard controller.

My question is what could I do / use them for? Can I link the 100w panel to the Victron unit so it gives me the extra 100w or do I use them to power elsewhere? Seems a waste for them to be installed and not getting used.

Sorry for the brief out line but I am a little confused on this subject after reading through various posts.

TA Steve

 

[rich432]

Congrats on the new solar setup! You can use the 100W panel in two ways:

1. Connect the 100W panel to your Victron MPPT controller if the voltages match. Wire them in parallel (positive to positive, negative to negative) to add an extra 100W.
2. Set up a small, separate system with a basic charge controller. Use it for small devices or to trickle charge another battery.

Don't let it go to waste!

 

[Jabstatt]

Or use the 100wto maintain your van battery and have the new system charge the leisure side.

Tony

 

[Wh05apk]

Can the existing panel not be connected direct to the battery using the existing controller? Thereby having 2 separate systems?

 

[Moto GBR]

Can the existing panel not be connected direct to the battery using the existing controller? Thereby having 2 separate systems?

I am not sure on that?

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[Phill D]

Can the existing panel not be connected direct to the battery using the existing controller? Thereby having 2 separate systems?

Only if the controller has an appropriate setting for the new lithium batteries

 

[RogerIvy]

In the vast majority of cases a solar controller will not damage a lithium (LiFePO4) battery.
They simply don’t have those charge phases that can damage a lithium/gel/AGM battery, such as desulphation and auto-repair. Even if they do the FogStar BMS (which is a JBD) is pretty good at protecting the cells.
The worse case scenario is that the old solar controller may not bring the lithium battery to a full Soc if its output voltage is too low.

The problem with mixing your new panels with your old one is that invariably you have to connect them in parallel. The problem with that is that the amps are increased perhaps to a point where your wires get quite hot. If the new panels are identical to the old, then it’s ok to connect them in series and the wires are then fine as only the voltage increases.

In the majority of cases we leave the old system as-is and when adding new (often bigger) panels we run new wires down to a new controller. In that way you get the max out of your panels.

Changing your old solar controller to charge only your starter battery is a “waste of solar energy” IMO (you’re pretty much trickle charging an already full starter battery all day and not contributing to your leisure battery). If however you plan to turn your lithium off during winter then at least that 100w panel will trickle your starter battery (so there is a scenario where re-wiring your old controller is not a bad idea - not my preference though).

 

[Guigsy]

Mismatched panels aren't great for efficiency. If you connect them in parallel, you'll get the voltage of the lowest side. Or connect in series and it's the current of the lowest panel. You might get lucky and get a reasonable chunk of extra juice. Or you might find you actually get less yield with the old panel added.

My vote would be that if you've still got the old controller, hook it up to your cab battery.