Worrying about battery damage...

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RandomJoe
RandomJoe Solar Expert Posts: 472 ✭✭✭
in Solar Beginners Corner #1
I have added enough continuous loads (primarily a couple of repeaters) to my ham radio solar system that I can't rely just on solar power to keep the battery topped up. I added an AC power supply and things are working, but I'm worried about long-term effects on the AGM battery.

The system consists of a 100AH 12V AGM battery, a 135W panel feeding through a SunKeeper PWM charge controller, and just added a power supply feeding through a RigRunner which is effectively a 3-stage battery charger. Off the battery I have all the ham bench gear plus repeaters.

Nicely, the RigRunner / power supply combo keep the battery floated at 13.5V. When the sun comes up, the SunKeeper picks up and floats just a touch higher, at 13.7V, which means I see the current from the AC supply drop to zero. Exactly what I wanted, I run as much as possible from the sun and the RigRunner makes up the difference (to its 10A limit) after which the battery supplies power.

What worries me though, is the SunKeeper insists on going through the absorption phase every day. So the battery never drops below 13.5V (unless I start transmitting with a high power rig) and gets hit with 14.1V for several hours each afternoon.

I start thinking "plate corrosion"... Should I be worried about that? Should I find a charge controller that won't absorb if the voltage hasn't fallen below - say - 12.5-13V? Other ideas?

The Big System continues to cruise along... Even got to use it to run the house in an outage Sunday morning. Others gripe when the power goes out, I get a childlike grin on my face! :D
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    Re: Worrying about battery damage...

    Does your charge controller have an AGM setting ? What do your battery mfg specs say for absorb setpoints ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    #3
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    Re: Worrying about battery damage...

    It has fixed settings - 14.1V during bulk / absorb (subject to temperature compensation) and 13.7V during float. Doesn't do equalization.

    It's a tiny thing, about the size of a credit card, intended for pole mounting such as on a roadside sign or such. It's been keeping the battery charged for probably a couple of years now, but before I added the AC charger the battery voltage would drop off a bit overnight with no charge input, especially if I was using the ham rigs.

    Edit: Can't find specs for the battery. It's a Werker brand from Batteries Plus. Not exactly "name brand"... The few spec sheets I found don't mention charge voltages.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: Worrying about battery damage...

    if you use the equipment daily it should go through the bulk, absorb, and float cycle to bring it back up. if the equipment is not being used then get a cc that you can set the absorb setpoint real low (between the absorb and float settings) if your present one won't adjust lower so it won't over-do it on the absorb. it should still be brought up to the full absorb setpoint occasionally. the only other solution for an idle battery might be to let it sit a day or 2 without being charged up by the solar.
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