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Old 08-28-2015, 02:00 PM
1stmate 1stmate is offline
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Default 12v battery usage

Hello all-
I have a small 12v system I use for emergency lighting (led) & small battery charging when the grid is down. That hasn't happened for any duration for a couple years, & I leave the panels attached to the batteries (w/a controller). The batteries don't get any real load on them, & rarely are they used below 80%.
My question: should I occasionally put a load on the batteries to "exercise" them? If so, I low should I drain them?
Thanks for the help!
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Old 08-30-2015, 04:36 PM
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12vman Male 12vman is offline
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The first thing I would do is perform a load test on the battery if they have been dormant for a couple of years. The electrolyte could be stratified and require a good heavy charge to mix them up again. Does your charge controller have an equalization function? (Assuming a flooded cell type battery)

"Also, in batteries that are in a standby condition at float charge for extended periods, the electrolyte tends to stratify into layers with higher concentrations of acid near the bottom of each cell and more diluted electrolyte near the top because the acid is heavier than the water. This causes uneven specific gravity within a cell further reducing its capacity, efficiency and life span. This uneven specific gravity causes the top portion of each cell to accumulate more sulfate on the plates, and the more acidic electrolyte lower in the cells can accelerate corrosion of the plates."

"My question: should I occasionally put a load on the batteries to "exercise" them? If so, I low should I drain them?"

If you have a multi-stage charge controller, (Bulk-Absorption-Float) any small, constant load will cause the controller to go through the stages and help keep the electrolyte mixed.

I use some LED outdoor lighting with a day/night photo switch for this function. The battery gets some discharge during the night and the absorption stage boils the battery enough to keep things mixed up automatically.

If you have a very basic voltage sensing controller, this could still help but the results won't be as good, being the charge voltage will only rise to the controllers maximum preset level. On multi-stage controllers, the absorption stage allows the charge voltage to rise above the float stage setting a volt or so and set there for an hour to allow the battery to boil a little more than normal. This reduces stratification..

Hope this helps..
"Without Deviation from the Norm, Progress is not Possible".
*Frank Zappa*
"Two roads diverged in a wood, and Ió I took the one less traveled by, And that has made all the difference"
*Robert Frost*
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Old 08-31-2015, 11:55 PM
1stmate 1stmate is offline
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Location: NH
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Default Thanks 12v Man!

I think I've got it. My controller is very basic; the only discharge the batteries get is when the controller is on a different battery. I have to switch the panels' input as the batteries are of different types/ages. So, when the "unattended" battery drops below 12.7v, the controller goes there, & the other one sits until 12.7v is reached, etc.
I just didn't know if an occasional draw down would be better for the overall battery life span.
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Old 09-05-2015, 03:54 AM
Kachad Male Kachad is offline
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Location: MN
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I have a few batteries that I use between March - December. They see regular use during these time periods. Typically, I will use them for about 5 days then fully charge them, and they will sit for maybe two weeks.

In December I bring them back home and hook up a trickle charger until March.

Prior to using the trickle charger, I had a lot of batteries that went bad over this time period.

So I don't know if this helps at all, but trickle chargers are pretty cheap - and the life of batteries have been extremely good when using this strategy, versus letting them sit.
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