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Old 03-07-2009, 07:11 PM
Tony1M Tony1M is offline
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Default What is maximum voltage during charging of a 12 volt battery?

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.)

The owner's manual states:

.............. "charging will continue until the battery voltage reaches approximately 14.4 V and the charge current has reduced to about 0.5 amps. At this point the amber Charging light will turn off and the green Charged light will turn on. At this point the internal charge reference will change in order to maintain battery voltage at 13.2 volts. Under this condition, called Maintain, most batteries can be left charging indefinitely."

The charger has been charging the battery for about 8 hours and presently the voltage is 15.0 Volts (reading taken with multimeter while charger is attached to battery and charging). Presumably the 0.5 amp criteria has not been met, because the charging cycle continues, unabated.

Just in case the new charger is faulty, so that I know when to pull the plug on the thing, what is the maximum voltage a 12 volt battery can be charged to without damaging it?

Thanks for any information.
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  #2  
Old 03-07-2009, 07:48 PM
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Default Re: What is maximum voltage during charging of a 12 volt battery?

Quote:
Originally Posted by Tony1M View Post
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.)

The owner's manual states:

.............. "charging will continue until the battery voltage reaches approximately 14.4 V and the charge current has reduced to about 0.5 amps. At this point the amber Charging light will turn off and the green Charged light will turn on. At this point the internal charge reference will change in order to maintain battery voltage at 13.2 volts. Under this condition, called Maintain, most batteries can be left charging indefinitely."

The charger has been charging the battery for about 8 hours and presently the voltage is 15.0 Volts (reading taken with multimeter while charger is attached to battery and charging). Presumably the 0.5 amp criteria has not been met, because the charging cycle continues, unabated.

Just in case the new charger is faulty, so that I know when to pull the plug on the thing, what is the maximum voltage a 12 volt battery can be charged to without damaging it?

Thanks for any information.
According to http://www.solarnavigator.net/battery_charging.htm

"
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.
"
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Old 03-07-2009, 07:57 PM
Tony1M Tony1M is offline
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Default Re: What is maximum voltage during charging of a 12 volt battery?

rfengineers,
Thanks very much! Looks like things aren't as wacky as I thought.
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Old 03-07-2009, 09:07 PM
Tony1M Tony1M is offline
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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.
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Old 03-07-2009, 09:16 PM
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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Originally Posted by Tony1M View Post

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?"
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Old 03-07-2009, 09:28 PM
Tony1M Tony1M is offline
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Default Re: What is maximum voltage during charging of a 12 volt battery?

Yes, and after watching that show, it is very difficult for us to feel much sympathy for a company that crushes perfectly good EVs.
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Old 03-08-2009, 10:25 AM
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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.
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Old 03-08-2009, 11:23 AM
Tony1M Tony1M is offline
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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Originally Posted by JRP3 View Post
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.
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Old 03-08-2009, 05:20 PM
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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Originally Posted by Tony1M View Post
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.
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Old 03-08-2009, 09:29 PM
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Default Re: What is maximum voltage during charging of a 12 volt battery?

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Originally Posted by Tony1M View Post
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.
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