Portable (suitcase) solar "install" question

johnm1 wrote:
Is the 0.6 - 1.2 volt drop going to kill my recharging ability with solar or is this where the CC comes in and somehow makes it work?

My wiring thoughts ...
- 50-100ft (1 direction) of 10 gauge wire with Anderson type connectors between the panels and the CC.
- CC within 5 ft of the battery (either inside the RV or inside a waterproof box).
- 10 gauge wire from CC to battery? I don't know what's biggest wire that I can use on the CC.

Keep in mind, I have a generator to (hopefully) do the heavy lifting charging every few days and (again hopefully) the solar will just hum along and finish it up.

edit: just saw red31's post.

Do I use the 17.8vpm instead of 12v for the drop calculations? If yes, then I'm guessing I'd be well above the 12-14+ volts needed?

your configuration of wire size is similar to mine. good choice IMHO. One suggestion. Break the 100ft of wire into 3 sections, a 50ft, and two 25ft sections. that way you can pick and choose what fits the camping situation.

for voltage drop calculations, you need to know current. drop is Amps x Resistance.

For your configuration and wire guage, if your using a PWM controller, don't worry about voltage drop. with a 160W panel, and around 9A max current with 10ga wire, it's a non issue. it won't affect the charging current at all, nor the float voltage. you'll see a max drop of around 2V which is still keeps you above battery voltage.

If your using a MPPT controller, you'll loose a few watts of bulk charging power. 100ft of 10 ga has 0.2ohms resistance. at 10A thats 20 watts of lost charging power, or 1.5A max. out of around 15A max current available with MPPT controller. again don't worry about it.

Now if you had 500W of solar or so, and a MPPT controller with panels in parallel, voltage drop will have noticeable effect on your max current at 100Ft of 10ga