I have 9 batteries. 5 are on Battery Tenders that maintain at 13.2 volts. 2 are on larger automatic chargers that maintain at 13.2 volts. The last 2 are on cheap Schumacher and Harbor Freight charger/tenders that maintain at 12.5 volts. Is 12.5 volts good enough to prevent sulfation and early demise of those batteries?

gperky wrote:I have 9 batteries. 5 are on Battery Tenders that maintain at 13.2 volts. 2 are on larger automatic chargers that maintain at 13.2 volts. The last 2 are on cheap Schumacher and Harbor Freight charger/tenders that maintain at 12.5 volts. Is 12.5 volts good enough to prevent sulfation and early demise of those batteries?Short answer ? No

12.5V is roughly 80% charged (at rest)Not good for long term

If you start to rotate the chargers, then the battery at lower voltage will start to see some higher voltage. Perhaps the cheap chargers will keep the battery at 13.2 but is not able to put in enough amperage to get it above 12.6?Right now, because the 12.5 volt battery is only about 50% full, and will need something on the order of 50 amp hours to fully charge it, they will not get that no matter how 'good' the maintenance charger is, they normally only put out 0.5 - 1 amp per hour, sometimes less.I would get a larger amp capacity charger on the discharged batterys very soon! Fred.

Just keep in mind that 13.6VDC will start boiling out of fluids over time where 13.2VDC will not do this as much if at all...If the batteries are already charged I would think anything above 12.6-7VDC would do the trick the maintain them... The batteries will demand how much current they want to see depending on their charge state. The only reason to have alot of DC CURRENT available would be to be able to charge several batteries in the battery bank at the same time and try to maintain around 17-20AMPS of DC CURRENT per battery if you want to charge them then in a quick three hour time frame. Otherwise it will take longer to charge them. My maintenance trickle charge is somewhere around 12.5-12.7 VDC and I monitor the battery charge status on a scheduled basis... I guess what the folks on here are saying if you want the batteries to stay at 12.7-8 VDC you should have your trickle charge at that level or a tad higher... In my case I guess they are saying my fully charged batteries will eventually drop down from their 12.7VDC level to my trickle charge level of 12.5VDC over time ???Also alot of folks will get their batteries to a full charge state and then just disconnect them and let them set. When they drop down to 12.5VDC or so over time then re-charge them back up again and disconnect again.I do this method as well just leaving them sit in the battery box and switch them completely out of the circuit. If they are charged-up they won't be affected by freezing temperatures.Roy Ken

The 12 Volt Side of Life. You may find it helpful.Have a good Turkey Day. :)

Is 12.5 volts sufficient for battery maintenance?

MEXICOWANDERER
Explorer
Nov 26, 2015
12.5 would make a great voltage level for a battery SUBSTITUTION device.

We have to keep in mind, most most vehicles have flooded batteries that are maintained at 13.6 to 13.9 volts over most of their operational life. Doesn't sound impressive, does it. Now raise battery temperature to 140F

13.9? At 140F? Should remove all the water in what, say a week? A lot, meaning perhaps 99% of the utterly urban legend about 13.6-13.8 "boiling batteries" at moderate temperature is because...

The owner allows three months to pass. Checks his battery. Dry. Looks at the voltage (say 13.8) screams "Thirteen Point Eight Volts Boiled My Batteries Dry!"

Wrong!

The battery was OLD. Antimony migration. If enough plate antimony migrates to the negative plates, it increases electrolysis ONE THOUSAND PERCENT. Ten times the water usage of a new battery. It'll use TEN TIMES the water at 13.2 volts and TEN TIMES the water at 14.2 volts.

Get the picture?

Trying to share a complete picture that shows battery temperature and charging voltage involves too much typing. I can't do it. But at 0c 32F the "right" voltage is absolutely wrong for 30c 86F. Google BATTERY TEMPERATURE CORRECTION and look at the chart.

I have maintained a group 31 AGM Lifeline for almost 16 months now at 13.65. About four tenths of a volt higher float voltage than what Lifeline recommends. Of course they are correct. Of course my digital scale (after dust has been carefully wiped off the battery case, says the battery has not lost .01 GRAM of weight. When electrolysis occurs, a frees a hydrogen atom from the electrolyte, meaning two atoms of oxygen are liberated. FREE AT LAST. They don't stick around. One molecule of water says bye-bye. Water means weight. It ain't light. So you can bey your bippy one HUNDREDTH of ONE GRAM of water weighs less than one eyedropper drop. And guess what? The hundredth of a gram ain't lost.

The moral of the story.

Don't base assumptions, or conclusions about batteries by one single solitary experience with an episode that left you unhappy. Sure you found your battery smelling like Yellowstone National Park. Sure you found cells so low the plates were exposed. The voltage was found to be 13.8. Smoking Gun! WRONG! Old battery or memory fart. Yes the battery was checked. Just this last August.....2012

When a battery maintenance charger voltage is checked and it is of a reputable brand, it makes sense that this voltage is much more likely to be correct than the voltage of a product that costs one twentieth the price from a place that has a shaky (at best) reputation for electronics.
Sam_Spade
Explorer
Nov 26, 2015
Boon Docker wrote:
Sam Spade wrote:

NO. Any additional "discussion" is just a waste of time.

??????

NO is the only answer he needs or asked for.
Additional "information" is just forum clutter; that includes ??????.
Boon_Docker
Explorer III
Nov 26, 2015
Now where is that ignore button.
robatthelake
Explorer
Nov 27, 2015
Try 14.8 on a decent pair of Golf Cart Batteries! A quality Charger will bring them up ,then taper off!
westend
Explorer
Nov 27, 2015
You could just use a set of jumper cables or even wires from one battery that has one of the bigger chargers to the ones that are at 12.5V.
RJsfishin
Explorer
Nov 27, 2015
There are only 3 reasons that voltage would be reading 12.5 while on a maintainer charger.
1- the battery is charging and voltage is slowly getting higher
2- the battery is junk
3- the charger is junk
What is so hard to understand about that ??
There ain't no big long drawn out reply going to change that !
Bobbo
Explorer II
Nov 27, 2015
RJsfishin wrote:
There are only 3 reasons that voltage would be reading 12.5 while on a maintainer charger.
1- the battery is charging and voltage is slowly getting higher
2- the battery is junk
3- the charger is junk
What is so hard to understand about that ??
There ain't no big long drawn out reply going to change that !

This is true. If after 12 to 24 hours, the voltage is STILL 12.5v, you can eliminate option #1.
MEXICOWANDERER
Explorer
Nov 27, 2015
Suuuuuurrrrreeeeee there is RJ,

With a tiny maintainer at capacity with a larger battery, use a digital voltmer and the second decimal column will rise a hundredth of a volt at a time. The battery is attempting to take a charge. This is a diagnostic observation.

"Ain't got no reason to try and learn me" is a classic response against education.

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Is 12.5 volts sufficient for battery maintenance?

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