# What is maximum voltage during charging of a 12 volt battery?



## rfengineers (Jun 2, 2008)

Tony1M said:


> Hi, I've been a lurker on this forum for quite some time and only registered recently. This is my first post and I did not think it would be about this matter, but here goes anyway.
> 
> Yesterday I bought a so-called "automatic", 1.5-amp battery charger that is normally $50, but on sale for $20. I've got it hooked up right now to our motorcycle's Tuasa (typical size) 12V flooded-lead-acid motorcycle battery. (The battery is out of the motorcyle, sitting on our kitchen stove.)
> 
> ...


According to LEAD ACID BATTERY CHARGING INFORMATION

"Battery Charging: Battery Charging takes place in three basic stages: Bulk, Absorption and Float.
Bulk Charge - The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.
Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts."


----------



## Tony1M (Feb 21, 2009)

rfengineers, 
Thanks very much! Looks like things aren't as wacky as I thought.


----------



## Tony1M (Feb 21, 2009)

Well, I just checked the battery/charger at 8:52 PM and, sure enough, the amber "Charging" light was off and the green "Charged" light was on. I measured volatge with the multimeter and voltage is 13.35 volts.

I will now leave the charger hooked up to the battery to maintain its charge until I re-install the battery into our 1984 Yamaha Venture Royale motorcycle - probably in May. Hopefully the bike will fire right up as soon as I hit the starter switch and the fully-charged battery spins the starter.

BTW, this is a fantastic forum. We presently own a 1992 Honda Accord which we bought new and I personally maintain. I'd like keep the car going until we can either buy, or build, an EV for our next vehicle. 

I'm watching Technologic's Sky Energy TK90AHA test thread very closely. There is a 74 Beetle available nearby that would make a very nice EV with those Sky batteries in it. I just have to overcome some resistance from my loving wife. The good thing is that we watched "Who Killed the Electric Car?" last week, and she got genuinely riled by GM's behavior. Strike while the iron is hot. That's what I say.


----------



## grayballs (Aug 27, 2008)

Tony1M said:


> The good thing is that we watched "Who Killed the Electric Car?" last week, and she got genuinely riled by GM's behavior. Strike while the iron is hot. That's what I say.


Stay tuned for "Who killed GM?"


----------



## Tony1M (Feb 21, 2009)

Yes, and after watching that show, it is very difficult for us to feel much sympathy for a company that crushes perfectly good EVs.


----------



## JRP3 (Mar 7, 2008)

Just a point to avoid future confusion, if you are ever using an AGM battery, (absorbed glass mat), voltage should never go above 14.7. That charger claiming to top out at 14.4 sounds as if it should be ok for an AGM but if it's really going to 15 volts or so means it's not AGM safe.


----------



## Tony1M (Feb 21, 2009)

JRP3 said:


> Just a point to avoid future confusion, if you are ever using an AGM battery, (absorbed glass mat), voltage should never go above 14.7. That charger claiming to top out at 14.4 sounds as if it should be ok for an AGM but if it's really going to 15 volts or so means it's not AGM safe.


Thanks for the information. Looks like we'll never own an AGM battery for our car or bike.


----------



## speculawyer (Feb 10, 2009)

Tony1M said:


> Thanks for the information. Looks like we'll never own an AGM battery for our car or bike.


Well, they are the most popular SLA battery these days. So, I wouldn't write them off.


----------



## JRP3 (Mar 7, 2008)

Tony1M said:


> Thanks for the information. Looks like we'll never own an AGM battery for our car or bike.


If you're saying that because of the potential for higher than 14.7 volts from an alternator I don't think that will be a problem. A battery charger could potentially put out over 15 volts for a long time while an alternator would only do that for a very short time. I've used AGM's on a boat and a jet ski with good results.


----------



## nenoludonja (May 11, 2013)

I accidentally tried to charge my 12V sealed acid battery with 35 Volts, for about 1 minute.
Have I destroyed my battery?

Battery was laying for about year and a half, and when I got it, voltage was about 2 volts.


----------



## JRP3 (Mar 7, 2008)

I'd guess if it was sitting at 2 volts it's already destroyed.


----------



## nenoludonja (May 11, 2013)

JRP3 said:


> I'd guess if it was sitting at 2 volts it's already destroyed.



I've been charging it now for almost 24 hours. Charging voltage is 14,5V. But the current is very small it reached value from 1mA to 35mA during that period, It rises slowly but surely . 

Does this mean it is completely dead?? Could it be anyhow recovered??


----------



## JRP3 (Mar 7, 2008)

I suppose it's possible. You certainly have nothing to lose by trying.


----------



## nenoludonja (May 11, 2013)

JRP3 said:


> I suppose it's possible. You certainly have nothing to lose by trying.


Well, i've yust lost two days.
Charging current is still about 25 mA, and when I disconnect hthe charger, battery voltage is 6V. When loaded , voltage drops back to 2V.


----------



## JRP3 (Mar 7, 2008)

One thing you could try is an equalization charge at 15V or higher if your charger can do that. Nigel Calder from Sail magazine recovered some Odyssey AGM's with a 17V charge I believe. Obviously this could be dangerous, watch for swelling, gassing, excessive heating, etc.


----------



## dougingraham (Jul 26, 2011)

nenoludonja said:


> I accidentally tried to charge my 12V sealed acid battery with 35 Volts, for about 1 minute.
> Have I destroyed my battery?
> 
> Battery was laying for about year and a half, and when I got it, voltage was about 2 volts.


The 35v didn't harm it. The sitting around for months discharged did. And it is not recoverable. Well I supposed you could take it all apart and purify the lead and make new plates but for all practical purposes it is time to send to recycling. Find a battery shop that will pay you for it. The one I use gives $8 for a typical car sized LA battery.


----------

