EvaKool 100w solar panel problems

I have recently purchase a bi-fold (2 x 50w) 100w EvaKool solar set with an EvaKool fridge. The solar panels have about 5 metres of quite heavy cable, and a 'EPHC' regulator mounted on the rear of the solar panel with glue. Just our of interest I put the multimeter on the thing today to see what voltages and amperages I was getting. One thing that seemed a bit strange was that at first the voltage cycled between about 11v - 15v (which I believe is part of the Pulse Width Modulation system used by most solar regulators to maximise charging output). Amperage was about right at 5 A or so.

The strange thing was a bit later I took the readings again, and the voltage was registering up around the 22v mark for some reason..... which concerned me to the point I left it a little while longer before taking it off the battery.

Is there some reason for this, or is this a case of warranty issues.....

FYI I had it connected to a 90AH deep cycle 12v wet cell type battery if that makes any difference.

Thanks in advance for your help.

Matt
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Reply By: Member - Ups and Downs - Tuesday, Jun 08, 2010 at 19:51

Tuesday, Jun 08, 2010 at 19:51
Matt

Not technical in this area but coincidentally I had someone check my panels today.
Depending on how much sun was on them (cloudy day) the panels went up to 21 point something volts. Less in part shade.

My panels have a sticker on the back that states, along with other info, 'Open Circuit voltage 23.8v'.

Paul
AnswerID: 420090

Reply By: Steve and Viv - Tuesday, Jun 08, 2010 at 20:15

Tuesday, Jun 08, 2010 at 20:15
Depending on the state of charge of your battery this will change the voltage it can accept. As the battery fills up the more voltage is required to fill it up that little bit more.

There are others that are better to describe this in more detail so hopefully they will be along soon :-)
AnswerID: 420093

Reply By: Member - John and Val - Tuesday, Jun 08, 2010 at 20:44

Tuesday, Jun 08, 2010 at 20:44
Matt,

Depends on the type of controller and just where you are taking your measurements. Simple controllers operate by connecting the panel directly to the battery until the battery voltage rises to about 14.7 (depending on the type of battery), then disconnecting the battery from the controller. Once disconnected the battery voltage drops slowly until the controller decides to cut in again, pushes the voltage up, disconnects..........and the cycle repeats. Until the battery approaches fully charged its voltage will not rise far enough for the controller to turn off, but when fully charged the controller may cycle on and off a few times per minute. This sounds pretty much like what you have observed, assuming that you were monitoring the battery voltage. The story is quite different if you have a more intelligent or mppt controller.

After the system had been running for a while you observed over 20 volts. I would expect that you were measuring the panel voltage, not the battery voltage. When the controller has disconnected the battery from the panel the panel voltage should be about 22V. This is the open circuit voltage. If your measurement of 22V was in fact at the battery, then you may well have a warranty issue, and an overcharged battery. It would be worth measuring right at the battery, between the terminals, to rule out any wiring problems, but if you see more than 15V between the battery terminals I'd suggest look to your warranty.

HTH

John
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AnswerID: 420095

Reply By: paul6108 - Tuesday, Jun 08, 2010 at 20:48

Tuesday, Jun 08, 2010 at 20:48
Open curcuit the panel can go up over 20 volt in good sun but the reg should never let the output charge go up this high. Are you sure it was connected to the battery when checking the voltage?
AnswerID: 420096

Follow Up By: ghostgum28 - Tuesday, Jun 08, 2010 at 21:00

Tuesday, Jun 08, 2010 at 21:00
Thanks for all the info to date......

It was measured after disconnecting it from the battery periodically....... Just seemed strange to me to be measuring the standard PWM range of 11v-15v but then after taking it off the battery, it was up around the 25v....

So just to clarify, both the panels are hooked up in parallel into the regulator that is glued to the rear of the panel. The regulator then has about 5m of 8B&S cable from the regulator to the alligator clips that are meant to go to the battery (which is where I measured the voltage from... the alligator clips that is)

I am also concerned that the AGM batteries that I hope to have it hooked up to (2 x 92AH in parallel) are only meant to have a max voltage of 14.4v..... does that mean I need a plasmatronics type controller that I can program the max output voltage ??

Thanks again.... Matt.
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Follow Up By: GerryP - Tuesday, Jun 08, 2010 at 21:32

Tuesday, Jun 08, 2010 at 21:32
Hi Matt,

From what you describe, everything is fine and working as it should be. You will find that had you reconnected the alligator clips back to the battery, the voltage would have immediately dropped back to around 14 volts again.

Solar panel open circuit (disconnected) voltage will be up around 20 or so volts and this is one method of testing them to see if they re OK.

Cheers
Gerry
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FollowupID: 690269

Follow Up By: Battery Value Pty Ltd - Tuesday, Jun 08, 2010 at 22:19

Tuesday, Jun 08, 2010 at 22:19
Haya ghostgum,

let me guess how this could all fit together...

fluctuating 11-15V @ 5A means high internal resistance of the battery. Could be sulphated up...is there enough electrolyte in it?

"standard PWM" range you're referring to is just an on/off type controller as has been explained by John.
This on/off action can give you wrong readings on the digital meter.
But if your battery was ok, these fluctuations would happen a lot slower so that you can get meaningful readings off the meter.

I'd say the battery is buggered, either sulfated, or it's very very low on electrolyte.
If you're going to connect your AGMs (US made by any chance?), then you'll have to test the regulator out on these.
Chances are that the regulator will show a different voltage once the battery issue has been fixed.
But it's too early to tell, not enough information to get a clear picture.
BTW, you're not killing the AGMs instantly if the voltage rises to 14.8V on them during bulk charging.
Just make sure this voltage isn't being kept up for too long, 2 or 3 hours is plenty.
After that time, the regulator voltage should drop back to around 13.8V (float charging).
If it doesn't do this, trash it and get a better one which will offer adjustable levels and other things.

Best regards, Peter
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FollowupID: 690275

Reply By: Thomo1970 - Wednesday, Jun 09, 2010 at 11:41

Wednesday, Jun 09, 2010 at 11:41
Hi Matt,


The regulator will normally be outputting a higher voltage when not connected to a battery, once the battery is connected properly the regulator "sees" the battery and automatically reduces the voltage to the correct voltage for the state of charge the battery is in.

I can advise that the EPHC regulator is a 4 stage PWM regulator / Charger. The 4 stages are Bulk, PWM, Boost and Float.
The EPHC also has a regulation point of 14.4 volts, so it is designed not to over-charge your batteries.

Measuring across the solar panels, or also across terminals 1 and 2 on the EPHC, it is not surprising if you are measuring over 20 volts. The higher the voltage, the more sunlight (power) the panels are receiving.

You may see the the voltage fluctuate while charging, this is just a part of PWM charging.



Thanks, Brodie
Warranty Manager
Evakool
AnswerID: 420144

Follow Up By: ghostgum28 - Wednesday, Jun 09, 2010 at 13:53

Wednesday, Jun 09, 2010 at 13:53
Thanks Brodie and everyone else..... That all makes sense now. I was just a little concerned that it may have had a fault and was heading towards destroying my new batteries, but thats all sorted now.

Thanks again to everyone.

Regards,

Matt
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FollowupID: 690333

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