to control or not to control and Mono or Poly

[jffnkrn]

So the question now that we are here.
existing set up is two group 31 agm batteries, all led lighting, 2015 fifth wheel with modern stuff. Panel is also unplugged at sunset and secured for theft prevention.
I have been running a small 65 watt solar panel when boondocking. the panel has a 25 foot cord that plugs into the typical power port installed at the battery location. I place the panel in the sunlight and move it along as the day goes on. I have never had an issue with over charging as there is always a draw on the system, pump light, lp detector, fridge, fridge fan, on and off pump, on and off radio and the use of a small 400 watt inverter for charging puters, phones, toys etc. I am upgrading to a 100 watt panel. why would i need a solar controller if i have a continuous draw on the battery bank? thoughts, ideas, tell me i am crazy etc. thanks in advance. Good Luck & Be Safe!!!

[lawrosa]

Ive used this ecoworthy 20 amp model MPPT with a 280w - 38 volt panel.

IMO start with this. Its cheap and works. Accepts up to 50 volts and 300 watts of solar.

IMO upgrade to a larger panel and use this. It will serve you well for a few years.

http://www.eco-worthy.com/catalog/worthy-mppt-solar-charge-controller-12v24v-p-182.html

89 bucks on amazon...

https://www.amazon.com/Solar-Charge-Controller-Regulator-solar/dp/B00FF1KGT4

A panel like this is a nice start.. Hook both panels in series to get close to max the voltage of controller. That controller will take the extra volts and turn them into amps..

http://www.eco-worthy.com/catalog/worthy-120w-foldable-polycrystalline-solar-suitcase-p-375.html

https://www.amazon.com/ECO-WORTHY-Portable-Polycrystalline-Foldable-Suitcase/dp/B00MGLIIQO

If you have the money get the 200 watt case

http://www.eco-worthy.com/catalog/worthy-200w-foldable-polycrystalline-solar-suitcase-p-499.html

This shows how mppt can turn 5.7 amps from my two panels @ 59 volts to 28 amps charging @ 12.7 volts. Although this is a 40 amp mppt and 560 watts of solar.

[Ed_Gee]

jffnkrn wrote:
OK, if the panel that i am getting has a 5.62 rated amp, and if i get one more that is just over 11 amps. why would i need the 30 amp controller? will the 20 am p controller do?

Yes, even a 15A controller would do. The point being made by a previous poster to get a larger controller was merely to address an easy upgrade to your solar panel count should you decide to increase them in the future. The price difference in controller capacity is not really that much in this size so I would agree ... get at least a 20A controlller...so you could then add a third or even a forth 100W panel easily in the future.

[jffnkrn]

OK, if the panel that i am getting has a 5.62 rated amp, and if i get one more that is just over 11 amps. why would i need the 30 amp controller? will the 20 am p controller do?

[Ed_Gee]

jffnkrn wrote:
ok, now for what it is worth: I may add another 100 watt solar panel. this of course depending on funding in the near future to get the same one, size, style and manufacture. then of course I would be at 200 watts, and the need for the controller, correct?

I would say yes.

[full-timer]

full-timer wrote:
In my opinion you should get at least a 30amp controller, because once you get a taste of solar you will want more.

jffnkrn wrote:
ok, now for what it is worth: I may add another 100 watt solar panel. this of course depending on funding in the near future to get the same one, size, style and manufacture. then of course I would be at 200 watts, and the need for the controller, correct?

______________________________________________________________________

See what I mean about getting a 30 amp controller.

[jffnkrn]

ok, now for what it is worth: I may add another 100 watt solar panel. this of course depending on funding in the near future to get the same one, size, style and manufacture. then of course I would be at 200 watts, and the need for the controller, correct?

[Ed_Gee]

jffnkrn wrote:
just an fyi for all. I don't have the 65 watt panel any longer, i will only have the 100 watt panel, I have the generator also and not planning on adding panel at this time. the one panel has served me well for over 10 years. Good Luck & Be Safe ! ! !

Just to reiterate from my previous comment - you have two Group 31 batteries having a total AH capacity of at least 200AH....maybe 250AH. You are going to use a single 100W panel.....having a nominal output of 5 A. Even were you to receive full sunlight over a 6 hour period ( doubtful ) you would still only be charging your 200+ AH battery bank with 30AH. My point is that your system as proposed does not need a charge controller as it is at best only producing a trickle charge. Your daily RV 12V consumption should easily exceed what you are putting in preventing any harm to batteries.

[jffnkrn]

just an fyi for all. I don't have the 65 watt panel any longer, i will only have the 100 watt panel, I have the generator also and not planning on adding panel at this time. the one panel has served me well for over 10 years. Good Luck & Be Safe ! ! !

[full-timer]

In my opinion you should get at least a 30amp controller, because once you get a taste of solar you will want more.

[MrWizard]

yes you need a controller 165 watts. a 15 amp controller should be large enough

[jffnkrn]

makes sense. thanks for the input. I have ordered the monocrystalline 100 watt panel adn the 20 amp charge controller. thaks everyone!!!!

[KD4UPL]

A basic charge controller can be had for $30 or so. If it saves you from ruining your batteries one time it was money very well spent. Why wouldn't you have one?

[Ed_Gee]

The reason you are getting away with not using a controller is most likely due to the tiny size of your solar panel charge current compared to the capacity of your two group 31 batteries. You are charging at barely above trickle charge rate for your battery bank. Moving from a 65 Watt panel to 100 is not likely going to change much, either. If you plan on using both (165W) I suggest you do get a charge controller. 165 watts can output about 8-9 amps in full direct sunlight.

[Lwiddis]

“I place the panel in the sunlight and move it along as the day goes on.”

Along with watching for theft this sounds fun.