Upgrades, People, Upgrades

[Autosnap]

Excellent! Thanks for the clarification! I'm learning quite a bit thanks to you guys.

[rickst29]

Originally Posted by Autosnap

Does anyone know why the purchased "Solar" wire is much larger diameter, has finer and more stands (like 10 to 20x more), are tinned copper, and have twice the thickness of insulator than my full copper awg cable?

I know it's softer and easier to pull, but it doesn't feel safe. Should I be concerned that my insulator isn't as thick or should I just take all the bought solar wire back and use the copper I have from my friend and just make up my own cables? They are stiffer, but I'm not concerned about that.

Far more important than pre-attached MC4 connectors is the higher quality of insulation - it's made for weather exposure, especially for handling UV and lower-frequency sunlight. "Household wire" insulation can't handle sunlight, and it's especially bad on a TM - where the wire is also exposed to high winds during travel. Wind pushes and pulls the wire, further increasing the development of cracks in non-flexible insulation.

Sllghtly OT: Buying short wire solar segments with connectors "already attached" commits costs a lot, and the sizes you get aren't exactly right for the short panel-to-pane connections you wil need on YOUR roof. You can instead cut "exactly right" segments from just two longer purchased lengths (black and red), adding your own connectors instead.

But putting MC-4 connectors on solar wire ends takes a bit of practice. Even I stil mess up about 20% of my attempts, so you should buy at least 50% extra "sets" of DIY MC4 plastic connectors, washers, and internal connecting pins if you try to do your own. (If you "need" 10, buy 20 - for both initial practice and later mess-ups.)

[rickst29]

Originally Posted by Wavery

4, panels wired 2S2P is doable (with 1 portable. You would end up with ~42V and ~20A (assuming panel rating of 10A).

3 panels would have to be wire parallel and would be ~21V and ~30A. The decreased voltage with parallel is safer but the increased amperage will take larger wire to keep the resistance (and heat) down. You would probably want to still use the same wire as in your diagram.

If the configuration is changed to "2 panels front, one panel rear" they definitely can be (and probably should be) wired in ALL IN SERIES. Your say that your MPPT solar controller rated at 150 Volts, that's an "absolute maximum". It can likely handle solar input voltage of up to 120 volts with zero problems and no lifespan issues, the unsed safety margin would be 20%. In comparison with Victron's soft limit (internal), you would still have around 16 volts of extra headroom.

Several posts have advised that you should add less weight to the front roof, and I agree with those posts. Your rated panel power would be only 600 watts, but that's enough for nearly anyone. (Excluding only a myself and a couple of other "Air Conditioner form the batteries" owners.)

From a rear-mounted battery and MPPT, the MPPT "Solar -" goes up to the rear shell panel "-" along a rear corner lift arm. Under sunlight, The rear "Panel +" output cable provides some current at around 22 volts (Vmp). ERoute that wire down the same lift arm, but DO NOT connect it to the MPPT.

That wire (a long one), instead comes down the rear corner lift arm, goes along the frame and floor joint outside, and then goes UP a forward shell lift arm to become input to the first of 2 "front shell" panels. Connect it the "panel -" lead of your "first" front panel.

Under good sunlight, that first front panel should have the result of raising the voltage from about 22 volts to around 44-45 volts. It's output wire is providing the lower of two current values: If both panels are near full power, it will still be around 8 amps.

The length of panel lead versus the distance between "front shell" panels might be short enough to connect them together directly, though you might need to add a small "jumper" to cover the full distance for that connection. The "+"output wire of the first front shell panel connects to panel "-" input for the second panel.

Then, "+" output from the second panel goes back over the lift arm. Route it down, then through a fast acting fuse (just 20 Amps would be fine), and then into the MPPT "+".

Under optimal conditions, The MPPT input will probably be a bit less than 8 Amps at around 67 volts, at noon on a perfect day late June day. MPPT conversion costs only about 5%, with maximum theoretical output current slightly under 40 amps (536 watts * 0.95 efficiency / 13.0 minimum output volts = 39.2 amps).