AGM Charging Fun

[Vanada]

Hey all!

About a year ago I switched over to a pair of 6V AGM deep cycles. https://gpelectric.com/products/6-volt-sun-cycle-agm-solar-battery/

So far my solar has kept them running fine but since winter has set in I've had to turn elsewhere to recharge them. It's the coldest it's been on the Canadian west coast this year just dipping below 0C but it's also taken me a while to get a hookup so the batteries were down to around 11.9 at worst. They got a good boost off the alternator the other day (14.2-14.4V, some number of amps) but now they're back down and my intelligent MotoMaster charger is only going to 13.2v even at 12A. Charger: https://www.canadiantire.ca/en/pdp/...lligent-battery-charger-12-8-2a-0111518p.html

To check the charger I put it on the starter battery and it hopped to 14.4V almost right away. Weirdly though it showed 1.5A then went down to 0A and decided that the battery was at 90%.

What's going on? Battery issue? Charger issue? Is the charger trying to warm them up first or something? Theoretically the AGM's were still at 30% so not even catastrophically discharged.

 

[highdesertranger]

New consumer battery chargers are junk IMO. they are automatic/smart, meaning they self adjust.

As soon as the voltage comes up they shut down or cut back. So when the sun comes out and the solar kicks in the battery charger shuts down. You need an old school dumb charger, However every auto parts store and battery store that I talked to last summer they they are no longer available.

BTW I was also told by some who wanted to offer an opinion that you can blame it on the greenies. a battery store in California told me flat out that California had outlawed dumb chargers because of global warming. They went as far as saying that when the charger sensed that the battery was full they had to shut off. I have not looked into this to verify, but it was repeated often.

highdesertranger

 

[user 423]

New consumer battery chargers are junk IMO.  they are automatic/smart,  meaning they self adjust.

As soon as the voltage comes up they shut down or cut back.  So when the sun comes out and the solar kicks in the battery charger shuts down. 

So charging at night would fix that problem?

 

[Vanada]

Thanks highdesertranger!

I ran it overnight and it appears I spoke a little too soon however the point still stands. The voltage came up veeeerrrry slowly but it took a couple hours. That's fine if I'm charging overnight but if I want to run a generator with this charger for a while and keep the batteries from tanking it will essentially do nothing.

It would be interesting to know why the charger does this before I go searching for a manual charger. As for the solar, there's so little here right now (my panels might even have snow right now) but I can easily switch the panels off at the charge controller to let the charger do its thing. Makes sense that if something brings the voltage up that the charger would mis-read.

Vanada