Proper portable solar panel connection

[Oldchinahand]

We have two 200W portable panels we use several times a year when boondocking in our 2007 Journey 34SE. We have been positioning them for best exposure and simply connecting them to our batteries (four deep cycle AGM 6v wired to give 12V) with alligator type clips.

So, last week some slick walked by as we were setting up and commented that we should disconnect the negative battery cable before we attach the solar cables to prevent system issues.

Never heard of that. Hasn't happened yet. Any thoughts on out there about proper attachment of portable solar panels.

Or is this just another slick walking by?

[creativepart]

I’m not sure about the advice, maybe yes, maybe no?

So each 200w panel has its own solar charge controller…. Yes? Do the two panels connect together? 400w is a lot of portable solar and combined is capable of putting out nearly (but not quite) 30 amps!

That’s a lot and would require at least 10ga wiring especially for a long run. Seems a hearty amount for alligator clips, as well.

Thinking about the question you asked, if your setup has a power disconnect switch I’d turn it off before connecting the clips. Or, connect the clips before positioning the panels in full sun.

If your Journey has an inverter, and I’d assume it does, read the manual’s warning to never disconnect the main negative battery cables first - always the positive first.

[BobC]

I'd install a solar port that you can plug into, making sure it's properly fused. I assume your panels have a built in controller or controllers. The problem I see is that ports like the Furrion ports are designed for a maximum of 10 amps which is too small for two 200w panels. I suppose you could use two ports, each separately connected to your batteries. You'll also need the proper connectors to mate with the ports. There may be ports available with higher amp ratings from other manufacturers.

https://www.amazon.com/Furrion-FSPIN...10737009&psc=1

[Oldchinahand]

Good observations. I'm running Renogy panels. Theoretical 20 amps each. Less of course. Laziness has kept me from installing ports. So many projects, so little time. It's time.

[Marine359]

This is the port I installed for portable solar. It’s 10awg and rated for 30 amps. I routed the inside wire to an mppt, and then on to a fuse block with 20 amp fuse. If you’re running close to rated max of the 10awg wire, you may want to put an inline fuse between port and SCC.

https://www.amazon.com/dp/B07SL3MBR6...ing=UTF8&psc=1

[HappiHenri]

(1) You did not say if your panels have a built-in solar controllers. Many do, but you need to check as you cannot just connect a solar panel directly to batteries without one as the raw output voltage is too high. But your panels should have included directions in this regard. Solar controllers reduce output voltage to an acceptable charging voltage.

(2) Have no idea what your impromptu walk-by advice giver is talking about. Never heard of this. You can connect / disconnect your solar controlled panels - at any time - directly to your batteries directly as long as observing correct polarities.

(3) The comparison usually made when trying to understand electricity is with water. So consider this -
- Your batteries are like a tank. They hold so much water (electrical charge). When you use your batteries to power items in your RV (lights, furnace fan, refrigerator control circuits, inverters, propane detector, etc) you are using your water tank (electricity).
- To refill your battery "tank" you have to feed electricity back into it. This is typically done by the RV converter, though may also be done by the engine alternator when driving (depends on your RV design). In your case you are also using your solar panels to supply this electricity. Their output is just like a small flow of water into your battery "tank". One or both can be connected as each has its own output, independent of the other.
- As such you can connect one or both of your solar controlled panels to your batteries. When in sunlight they will produce electricity which flows into your batteries, recharging them.
- As others have suggested it would make things easier for you if you installed plug-in connectors on your batteries and each of your solar panels. So - 2 connectors for your 2 panels. These are simple wiring changes to make.
- However - you do not want to overcharge your batteries. Your panels will put out electricity whenever in sunlight. Better solar controllers will control this, but most built in controllers (fitted to the back of each panel only act as voltage reducers, not sensing battery voltage). SO - it is always a good idea to install a battery monitoring meter. (Such as a Victron 712). These are much more complicated to install but will show you many battery parameters which are important to know - such as battery voltage, battery % of charge, current rate of charge/discharge. etc. By knowing how really charged up your house batteries are you can see when charging is needed - or not. Will also help prevent over-discharging - which will ruin lead-acid batteries.

[powercat_ras]

Originally Posted by Oldchinahand

We have two 200W portable panels we use several times a year when boondocking in our 2007 Journey 34SE. We have been positioning them for best exposure and simply connecting them to our batteries (four deep cycle AGM 6v wired to give 12V) with alligator type clips.

So, last week some slick walked by as we were setting up and commented that we should disconnect the negative battery cable before we attach the solar cables to prevent system issues.

Never heard of that. Hasn't happened yet. Any thoughts on out there about proper attachment of portable solar panels.

Or is this just another slick walking by?

No one really answered your original question yet. No you don't need to disconnect the negative battery cable before connecting portal solar panel to +12 and negative ground battery terminals.

200 watt panels would be huge, 5' x 2' each in size. Are they really 200 watt each? If so they could put out 17 amps each, that's a serious portable system. Guess your rig is big enough to haul them, so I suppose it's possible.

As was noted by earlier posters, there should be a solar charge controller to prevent overcharging when it senses the batteries are charged. It would have to be a larger one than is usually used for portable systems to handle 400 watts of solar panels.

As was noted by earlier posters, there should be an in-line fuse sized based on the wire size being used to connect the solar panel / panels to the batteries.

There are some solar charging ports that could do away with the alligator clip method but they are not rated for 34 amps.