Charging an AGM battery

[Bala]

I have BAE VRLA. 2V Cells 12V system.

I have not had to Eq.

They are set to Charge Bulk and Absorb at 2.366 V Per cell, so 28.4V for my system. For these batteries, new a bit over 3 years ago, I fitted a new Morningstar tri star regulator. It rarely goes into float even though they are 100% soc. It will only go into float when we are not home so seems to act on minimal current draw. Basically a max smoke set up.

I old system with FLA and different controllers would float by noon.

The specs for my batteries give 2.4V per cell as a gassing Voltage. When I had them new I had settings given to me by the supplier that were 2.4V or higher and I could hear them gassing so went by the manufactures data and dropped it back to the 2.366.

Your initial question is can you go higher in Voltage than specs. I would say no, you need to stay under gassing V.

[-robw-]

Yeah, I think what I'm observing here is just a difference between a battery that will gas, and one that will not. Since floodeds gas, we can throw as much amperage as we want, regardless of SOC, which will then be converted to literally gas. But AGM's don't gas (much) so they can't convert the extra amperage, and "tell" the CC that.

Got that right?

[Bala]

I don't know enough about your system, your usage or sun hrs to help much.

I suggested one option to try to diagnose the system.

Another would be to try running each string separately with one controller.

I thought I had a failed Lithium in my caravan but it was just slightly loose connection. A friend had a charging problem with a lithium that was just a slightly loose connection.

You seem convinced it is the type of battery causing the problem. I am not so sure.

[-robw-]

Yes, I'm convinced, although now not so much that it's a problem. A disadvantage, for sure, but if I can now escape this homestead for a couple of weeks w/o wet cells going dry it's well worth it. Luckily I have the AGM's on a pretty powerful array so as long as I get some sun, and in Texas we obviously get a lot, I should be good. Thanks for the term "gassing", got me thinking about that and reaching this conclusion.

I've now converted to lithium and AGM's on two systems, at costs borderline more expensive than my prior floodeds, and am a happy camper. God, those things were horrid..

[Bala]

I went to sealed for same reason. Do not need to worry about water. I can't remember the last time I looked at my batteries, it could be 12 months.

I never let my soc get below 80%. If the batteries are down I run the generator to charge and at the same time heat water, wash and dry clothes etc.

I have lithium in my caravan and Ute auxiliary. The house will get lithium next.

[-robw-]

But if I used my generator at 80% I wouldn't be able to brag to my two woke girls how much greener I am then them

Thanks again.

[-robw-]

My thinking is you have either a problem with your controller wiring/setup or with your battery wiring/setup or batteries.

I have only used series batteries for my house. Firstly FLA and now sealed.

If I had your problem I would turn off all loads and use my external A/C charger and charge the bank taking note of the charge current. They should taper off to 0 amps current or almost. If all is well this will give you a true 100% Soc but faulty batteries can also taper off to 0 amps current.

I would do that coming up to dark so that you then start the night with a known 100% soc and reset meter. Turn the loads back on.

Assuming a nice sunny day next day monitor what happens.

It is just on daybreak here, my meter is telling me I am -70Ah, so I know I what I need to get back today.

FWIW; a couple of things seem to be true about these Renogy 200ah AGM's.

1) Their efficiency is a lot better then 85%. Granted they're only a month old, but they're tracking closer to 100%, which my wet cells could never do. This was observed by, once ammeter showed full, shutting the system down and connecting my NOCO charger to a battery in each bank. They were indeed full.

2) It'll take warmer weather to confirm but I doubt they're 200ah @ C20. I now have them registered on my ammeter at 175ah, which is tracking perfectly with battery box at ~50 degrees.