Thread: Solar dilema

If it was me I would just run them all in parallel.
Just make sure you mount the regulator near the battery not on the panel.

If your aux battery is a medium to large the alternator won't hurt it.

Dave.

depending on the input voltage of the regulator I would suggest that a full 12v in parrallel setup with high quality blocking diodes would be the best bet although thats potentially going to cost you a couple of hundred mA per diode/panel.

But it does stop partial shading causing headaches.

If you can set the array up so that all panels get lit you can do without the blocking diodes and run a parallel setup but when one panel dies it will pull the power out of the system.

if you flatten the AGM and then dump 140 amps from the alternator into it its not going to like you very much. Id suggest putting something in that will act as a current limiter if you plan on flattening the battery too much but this wont be a problem if you keep the battery inside its normal operating spec.

Dave,
Can you explain what these blocking diodes are for?

I have two 80 watt panels which I take when I go camping. I have one connected to the car to run the engle and the other to the caravan to run lights and water pump.

As 80 watts is a bit of overkill for the caravan I have made up a lead to connect the two in parallel to run the engle on a cloudy day.

This will deliver about 5 amps each when sunny to about one amp each when heavy cloud.

Ok, lets say the sun is shining and I am getting five amps x two and the wind blows one of them over and therefore one is out of action, don't I still get five amps from the other one?

Dave.

The only advantage to running them in a series then parallel config would be to double the voltage, which would reduce the current, which means longer cable runs for the same voltage drop, but you have 5 panels, which means one panel left over. you should only series identical panels(same age etc), so two sets, one set of new panels in series, one set of old panels in series, then parallel the outputs of the two sets.
Thats a lot of wiring to put together on site!
If you just parallel the lot, they can all "piggy-back" off each other, so you can add and remove panels as you wish.
The MPPT regulator will pull the voltage down to the point where you are getting maximum total output from whatever panels you add.

Cheers,
Fraser

the panel may still be outputting 5 amps but the one thats fallen over will now be drawing current.

if you think of it like a pair simple permanant magnet generators in parralell while both are being driven your getting power out of both of them. If you remove the drive from one it will carry on spinning becasue its gone from being a generator to a motor. The output from the generator thats still being driven goes to making the undriven generator turn instead of into the batteries.

a blocking diode also forms the simplest form of charging regulator because it stops the battery from discharging into the panel when its not providing charge.

Hi I was wondering if or how do I measure amps, I have a digital multi meter and it tells me how many volts my panels are putting out but have no idea how many amps??
Andrew

Andrew,
Most digital multimeters usually have a current measurement of ten amps.
If you have this you will need to unplug the non common lead and put it into the current measurement jack. You then remove one of your solar panel leads from the battery and connect it to one of the multimeter leads. Then connect the other lead to your battery. Don't worry about which way round the leads are. If it is wrong you will just get a minus before the reading.

The above procedure is known as connecting the multimeter "In series"

Dave.

Thanks Mr Whippy I will try it out soon as the sun comes up.
Andrew