solar cynergy blocking diodes

venturadan · June 2012

I have 2 Solar Cynergy 12v 65w solar panels for charging a battery bank. Does anyone know if they have blocking diodes or will I need to install one. I have requested this information from Solar Cynergy but have not received a response. If I need to install how do I calculate the size diode needed.

Cariboocoot · June 2012

Re: solar cynergy blocking diodes

Welcome to the forum.

Two words: charge controller.

Buy one the right size for your application and use it. Eliminates the need for blocking diodes and makes sure the battery is charged properly instead of haphazardly. Those panels will be about 3.7 Amps Imp (17.6 Vmp). If you use them in parallel on a 12 Volt system the controller needs to be able to handle 8 Amps or more. A small SunSaver 10 Amp unit would be fine: http://www.solar-electric.com/ss-10.html

venturadan · June 2012

Re: solar cynergy blocking diodes

I was planning on connecting the panels directly to the batteries and use a divert controller to divert power to resisters for free heat when the batteries reach a point of being fully charged. If I use a charge controller wouldn't it keep the batteries from reaching the point where the divert controller would divert the load?

waynefromnscanada · June 2012

Re: solar cynergy blocking diodes

venturadan wrote: »

I was planning on connecting the panels directly to the batteries and use a divert controller to divert power to resisters for free heat when the batteries reach a point of being fully charged. If I use a charge controller wouldn't it keep the batteries from reaching the point where the divert controller would divert the load?

Think about it - - how much "free heat" do you get from a 40 watt light bulb that might, or might not be on for an hour a day?

Cariboocoot · June 2012

Re: solar cynergy blocking diodes

venturadan wrote: »

I was planning on connecting the panels directly to the batteries and use a divert controller to divert power to resisters for free heat when the batteries reach a point of being fully charged. If I use a charge controller wouldn't it keep the batteries from reaching the point where the divert controller would divert the load?

The amount of "free heat" you will get from two 65 Watt panels is practically nil. Look at any space heater on the market: you'll find they start at 500 Watts. That's a long ways from 130 Watts. Depending on the size of battery you use, there's not likely to be much heating going on at all as the panels would have to be above charge Voltage for a long time and that's not likely to happen. Besides which, the heat would come and go as it wants (middle of the day), not when you need it.

Those panels would only be good for recharging up to about 140 Amp hours @ 12 Volts, and would work best at about half that. That's not much power capacity at all.

Always a good read, the battery FAQ's: http://www.windsun.com/Batteries/Battery_FAQ.htm

Electricity is a lousy way to heat things.

BB. · June 2012

Re: solar cynergy blocking diodes

Diversion/dump/shunt controllers don't do as well as standard series charge controllers charging/maintaining battery banks.

Diversion controllers tend to be "harder" on the battery bank (potentially, larger charging/discharging currents "micro cycling" the battery bank, as I understand).

Basically, your choice is to over charge the battery with too much current as it nears 100% full, or discharge the battery (current should exceed maximum output of solar panels) into the dump load. And nothing in between.

In theory (and as required by NEC), because loads/controllers can fail, the NEC requires two controllers (second one as a backup) in case the first controller, or load, fails. (overcharging a battery bank can, eventually, be a fire hazard).

-Bill

solar cynergy blocking diodes

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