Went out today and batteries were getting 15.2V

[JCruse]

And being January in the northeast the sun isn't exactly that strong, plus the house blocks any hope of direct sunlight. I've seen this same voltage a couple of times in the last few months. Went out half hour later and voltage was back down to a safe 14.5v. I'm charging either one or two AGM's (depending on settings) so they're not supposed to see over 15v. Plus both batteries were fully charged already. Any idea what's going on here?


(Renogy 100W panel and BatteryMinder SCC-180 controller)

 

[spressomon]

Not familiar with the controller you are using but from a quick glance it looks like it can perform as a "desulfator". From the voltage reading you got I would assume it is in desolation mode along with lead acid setting?

 

[george_tlc]

The various charging voltage thresholds (charge, float, bulk etc) are temperature dependent - higher voltage with colder temperatures. You presumably connected up your charge controller's temperature sensor?

cheers,
george.

 

[JCruse]

The various charging voltage thresholds (charge, float, bulk etc) are temperature dependent - higher voltage with colder temperatures. You presumably connected up your charge controller's temperature sensor?

cheers,
george.

It is quite cold today, 32*, went down into the 20's last night. And yes absolutely I do have the temp sensor connected, always.

All I really know about that 'over 15V' issue I got from Odyssey batteries saying not to exceed 15v for long, if at all, and then only by a little, which it was.
I was mostly surprised by the fact that the batt's are fully charged, so why the high voltage? The starter batt isn't even connected! So no parasitic draw even.
I figured this might be a good opportunity to learn something too.



Output Shaft: I thought regular wet cell batteries tolerated the higher voltages more so than AGM.




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[george_tlc]

Charging voltage is temp dependent like I wrote above. 32F is pretty cold in the charging temp range and the charge controller will run at >15V (the manual even states that) for AGM. http://www.batteryminders.com/content/manuals/SCC180 D060514.pdf

Why it is not sitting at 'float', I have no idea, it will be whatever algorithm they decided to implement. Float should be near 14V (even when very cold). Maybe the SCC-180 cycles between float and a charge. Best bet would be to contact the manufacturer to find out the details of what/why...

Maybe it restarts the charge cycle every time the sun level drops low and then pops back up... the manufacturer should be able to tell you.

cheers,
george.

 

[george_tlc]

Yes, but that's not what you want to float at. Given the batteries are supposedly fully charged, then they should NOT be floating much above 14.2V at 32F.

cheers,
george.

 

[george_tlc]

^ yes, I realize that the charger will follow a profile. That's why I recommended that the OP contact the manufacturer if he wants the details of what algorithm it follows for situations such as sun shading and re-appearing. Or other cycles where it goes through a test by going from float back to charge/bulk before settling back to float.

A data logger over a period of a day or two would show what the charger typically does.

cheers,
george.

 

[LAMBCRUSHER]

everyone is an expert

 

[JCruse]

Thanks for the replies guys.

I forgot to mention that usually when it's going over 15V it does so by swinging constantly from mid 14's to low-mid 15's and does so quickly. In a minute you can see the whole swing up and back down. Then other times it hovers around the higher numbers. Just now I saw it swinging from 15.21 to 15.39 and back down in 10 seconds and back up again etc. It is 34*.

 

[JCruse]

Get a better charger.
These are the best:

Battery Chargers - CTEK Battery Chargers

Dude we're talkin SOLAR chargers.

Besides I have a ProMariner ProNautic 1250P charger, so that base is well covered.

Hey to the BatteryMinders credit at the close of the day - 3 hours after dark - the Lifeline 31XT had a voltage of 13.29V.
After dismal sun.







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