Cheap PWM charge controller

[eddystone]

I planned to get a cheap (about £12-15) PWM charge controller from ebay to control 2 x 20W solar panels going into 3 x 85 ah batteries. Is there anything wrong with these - are the £30 worth getting instead?

 

[Pete7]

The cheap ones might work and be efficient but there is no real way of knowing or doing a comparison. I opted for a pair of PWM chargers from Barden as they are a known quality at a sensible price and have used them before. I have a pair of them only because it was easier to wire up two panel in different locations than run long wires all around the boat. There is a slight conflick but they work well enough together. One of the smaller Solara PWM would suit your needs or something from Morning Star.

http://www.barden-ukshop.com/solara-regulators-150-c.asp

 

[rogerthebodger]

I also have 2 Morning Star PWM regulator in parallel. What is the conflict that you are seeing.

I have found that when the regulators are reducing current feed that I get a buzzing and my radio and TV. The buzzing stops if I switch the feed from the panels with the PWM regulator.

Have fitted some capacitors on the output of the regulators to try to smooth the output. Not checked the result yet.

 

[eddystone]

OK I have 1 x 85 ah engine battery and 2 x 85 ah service batteries in series (I think) making 1 x 170 ah service battery. As PWM dual battery controllers are expensive and this is a low cost installation to keep the house batteries topped up, seems I have 2 options. 1) Run the wiring for the 2 panels separately through a controller each to the engine and service batteries. however, I also have a jump starter for emergencies if the engine battery won't turn the engine so ...2) Connect the 2 panels in series and then into single regulator into service bank. Presumably if they are connected in series (if that's the one where Ahs are summed but voltage stays the same) its OK to connect to one of the batteries (I'm not doing it myself just supplying the kit)

I assume with 2 x 20 watt panels a 5 or 6 amp controller will be sufficient?

 

[ghostlymoron]

OK I have 1 x 85 ah engine battery and 2 x 85 ah service batteries in series (I think) making 1 x 170 ah service battery. As PWM dual battery controllers are expensive and this is a low cost installation to keep the house batteries topped up, seems I have 2 options. 1) Run the wiring for the 2 panels separately through a controller each to the engine and service batteries. however, I also have a jump starter for emergencies if the engine battery won't turn the engine so ...2) Connect the 2 panels in series and then into single regulator into service bank. Presumably if they are connected in series (if that's the one where Ahs are summed but voltage stays the same) its OK to connect to one of the batteries (I'm not doing it myself just supplying the kit)

I assume with 2 x 20 watt panels a 5 or 6 amp controller will be sufficient?

As always, it depends how much power you use, only you can decide that. But I would think 2 x 20w panels would be fine assuming you're not running air-conditioning 24/7. 40 watts divided by 12 volts gives you 3.3a so a 5 amp controller would be OK. Generally it's not necessary to charge the engine battery with solar, the alternator will replenish the power used in starting in a few minutes. So only connect the solar to the leisure batteries but maybe have some means of starting via the leisure batteries if the engine battery develops a fault. A bypass switch is ideal but you can use jump leads (but not so convenient).
The leisure batteries must be wired in parallel for 12v and there's a special way of doing it so that the draw from each is equalised.

 

[VicS]

OK I have 1 x 85 ah engine battery and 2 x 85 ah service batteries in series (I think) making 1 x 170 ah service battery. As PWM dual battery controllers are expensive and this is a low cost installation to keep the house batteries topped up, seems I have 2 options. 1) Run the wiring for the 2 panels separately through a controller each to the engine and service batteries. however, I also have a jump starter for emergencies if the engine battery won't turn the engine so ...2) Connect the 2 panels in series and then into single regulator into service bank. Presumably if they are connected in series (if that's the one where Ahs are summed but voltage stays the same) its OK to connect to one of the batteries (I'm not doing it myself just supplying the kit)

I assume with 2 x 20 watt panels a 5 or 6 amp controller will be sufficient?

As Ghostlymoron indicates you need to start by understanding the difference between series and parallel

If your two 85 Ah house batteries are both 12 volt then they will be connected in parallel to give you a 12 volt 170 Ah battery bank.

Like wise if your solar panels are to give you twice the output at the same voltage they must be connected in parallel.

Parallel is positive to positive and negative to negative. Like towing another boat alongside, bow to bow, stern to stern

Series is in line with with each other, like towing your tender behind you.

Series doubles the volts but does not increase the Ah capacity of the batteries or the amps output of a solar panel.

Diagram to follow if I can find it!


The "special" way to connect two batteries in parallel is to connect them as above, + to + and - to -, but then make the output connection to the + terminal on one battery and the - terminal on the other. It prevents the little bit of resistance in the interconnecting wires unevenly loading or charging the two batteries. For your application probably splitting hairs .. relevant though for heavy users, like a canal boat liveaboard.

Yes, a 5 or 6 amp controller will do the trick.

2x 20 = 40 watts . 40 watts at 12 volts is only just over 3 amps, but solar panels are rated at the "maximum power" voltage which is probably nearer 16 volts and 2.5 amps for the two. The manufacturers spec for the solar panle should tell you the maximum current, which will only be a little more than 2.5 amps for the two.

 

[VicS]

Diagram that shows the difference between series and parallel

Diagram that shows the "special" way of connecting two batteries in parallel

 

[Hoolie]

I recently bought two 100w panels and two PWM chargers - not yet fitted.

My logic is that the two panels may have widely different conditions ie one in sun, the other in shade or shadow. A single controller will set itself for the higher output panel and effectively ignore the other. But with two controllers they'll each be operating according to the panel they're connected to and there'll be useful power from both.

 

[VicS]

I recently bought two 100w panels and two PWM chargers - not yet fitted.

My logic is that the two panels may have widely different conditions ie one in sun, the other in shade or shadow. A single controller will set itself for the higher output panel and effectively ignore the other. But with two controllers they'll each be operating according to the panel they're connected to and there'll be useful power from both.

The controllers dont actually control the panels ,
ITYWF that they control the current going to the battery. I don't think there will be anything to gain by fitting to separate controllers.

You might get a bit more by using an MPPT controller.