Looking For A 36v Solar Battery Maintainer

[Rickochet]

Originally Posted by Sergio

If You get an MPPT charger controller, then You can use a smaller voltage solar panel array of high wattage and the controller will boost the output voltage as needed to maintain the configured charging output

While these things are not rocket science, there are a few basic concepts that need to be understood.

If You just connect solar panels in series, the only concern is what kind of "bypass" system the panel arrays have to exclude sections of the panel that are not generating voltage.

A solar voltaic cell that is not getting sun will have a high resistance and will stop all current from flowing through the entire system.

If Your panel has a built in controller, the + and - wires coming out of it are not the output of the solar cells, but possibly the PWM of the charger or whatever unknown circuit is being used.

I have never heard of connecting solar chargers in series, the proper solution in this case is to use an MPPT controller where the solar panel voltage and the battery voltage don't need to match.

The recommended float charge voltage for a 36v Trojan pack at 77F is 39.6v, You can look up the correct voltage for your batteries and the proper temperature compensation.

Thanks Sergio, will do some digging for a panel and controller. BTW, my batts are Trojans and show 38.2v at rest after charging.

[Sergio]

Just so You have other options to research, the alternative of using an MPPT controller is to use a PWM controller and a solar array that has higher voltage than the batteries.

The less expensive PWM charger controllers can only "buck" or reduce the voltage, not "boost" like the MPPT controllers.

You would want to have a sollar array of at least 48v to accommodate some of the sections being "shunt" off the system due to shading.

Here is an example of a PWM controller that You can adjust the float output to your desired value:

http://www.amazon.com/Intelligent-Regulator-Controller-Environment-Charging/dp/B015MOC3VM/ref=sr_1_1?ie=UTF8&qid=1452792795&sr=8-1&keywords=Intelligent+LCD+30A+36%2F48%2F60v+PWM+Solar+Panel

http://www.amazon.com/Intelligent-Regulator-Controller-Environment-Charging/dp/B015MOC3VM/ref=sr_1_1?ie=UTF8&qid=1452792795&sr=8-1&keywords=Intelligent+LCD+30A+36%2F48%2F60v+PWM+Solar+Panel

[Rickochet]

Originally Posted by Sergio

Here is an example of a PWM controller that You can adjust the float output to your desired value:

http://www.amazon.com/Intelligent-Re...WM+Solar+Panel

Thanks Sergio. I was just looking at that one on ebay. Unfortunately the higher voltage panels I have found so far are too expensive. Looks like I am back to MPPT controller and single 12v panel or back to the three separate chargers idea. Lots of time to tinker since I won't need it until April.

[Rickochet]

Originally Posted by Sergio

If You get an MPPT charger controller, then You can use a smaller voltage solar panel array of high wattage and the controller will boost the output voltage as needed to maintain the configured charging output

Sergio what wattage 12v panel would I need to work with the MPPT controller?

[Sergio]

A typical 6v-225AH battery will loose 1% capacity a day or 2.25AH.

So in order to compensate for the loss, You need to generate approximately (per day):

80w @ 36v
120w @ 24v
240w @ 12v

The 24v panels would be ideal regardless of the MPPT controller.

The 12v panels could work fine also if the controller has a low enough input voltage so it can operate on not so sunny days.

Those watt ratings are "watt-hour" per day requirements, so a 120w@24v would require 1 hour to generate the needed charger, while a 60W@24v would require 2 sunny hours.

Good water-proof MPPT controller:
https://www.altestore.com/store/char...-carts-p10634/

Good size Panel that will actually provide a small charge as well:
https://www.altestore.com/store/sola...-panel-p10355/

What I noticed after a few searches is that by the time you get the controller, panel(s), brackets, connectors and everything else You need, those kits like I posted originally are not much more expensive.

If you are brave enough I am sure You can get equivalent parts for half of the price from China.... If so, let us know the outcome.

[jacannon]

My cart sits in the woods, far from any power poles. 2 12 volt storage batteries, 3 solar panels, controller and and inverter for an off grid cabin. I can plug in my battery charger and keep my cart up and running.

[Rickochet]

Originally Posted by jacannon

My cart sits in the woods, far from any power poles. 2 12 volt storage batteries, 3 solar panels, controller and and inverter for an off grid cabin. I can plug in my battery charger and keep my cart up and running.

Great idea, but my issue is that I leave the cart in a parking lot at a state park with about 40 other carts. Everything must be located on the cart. I don't have room for an extra battery.