Charging time for 12 V battery

I have a 12 Volt battery, 9.5 Ah that uses a 12 volt charger 1.0 amp.

Assuming the battery is completely discharged, is there a way to determine how long to charge ?

Thanks, Andy

Reply to
andrew_kennedy7
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I'll assume that it's an SLA (sealed lead acid) or AGM (Absorbed Glass Mat) battery. Makers and model numbers are a good thing to disclose.

long to charge ?

Yep. Math.

Incidentally, if your battery is completely discharged (i.e. zero volts), it's probably dead.

A new lead acid battery has a Coulombic Efficiency of about 75%. That means for every amp you feed the battery, only 75% of it stays in the battery. 12v * 9.5 Amp-Hr / 0.75 = 152 watt-hrs will be needed to recharge the battery. If your charger actually delivers 1 amp, it will take: 152 watt-hrs / (12v * 1 amp) = 13 hrs

This is under ideal and simplified circumstances. Coulombic charge efficiency varies from 50% to 98% depending on battery type and age. Your battery may not be completely discharged. Your 12v 1A charger (maker and model please?) may be capable of delivering a 1 Amp maximum, but will probably deliver much less while charging. SLA batteries just hate going over their rated maximum voltage. So, it's likely that the charger is set to a conservative voltage, that may not fully charge the battery. The charge current is also not constant over the entire charge cycle. Lots of variables, potential errors, and guesswork here.

My wild guess(tm) is about 8-10 hours will be about right. Better to undercharge than to go over. I can make a more accurate guess(tm) when you find the makers and model numbers.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

long to charge ?

Power Wheels Charger for Gray 12v Battery 00801-1778

Reply to
andrew_kennedy7

Power Wheels Charger for Gray 12v Battery 00801-1778

** Always post links.

DO NOT expect others to do the running around for you.

And BTW - this is the WRONG NG for such a question.

.... Phil

Reply to
Phil Allison

That number shows up as several different devices. Don't think you have any choice but to measure what your charger does.

I think your bigger problem is gonna be sulfation. The kids are gonna ride it until it stops dead. The next time you hear about it is next spring when the battery won't take a charge.

I lost a set of electric scooter batteries because it got shuffled around in the garage and the power switch was turned on all winter.

It might also be interesting to compare the calculated time to charge against the attention span of kids.

Unless you want to pay close attention, you need something automatic.

Reply to
mike

Autistic?

Reply to
orion.osiris

Free lobotomy gone bad. Another of Dr. Frankenstein's failed experiments. :(

Reply to
Michael A. Terrell

Yes, this is the newsgroup for people down under to go on a Tourettes rant.

Reply to
miso

This might help: About 14 hrs and no more, assuming a totally discharged battery.

Looks like the Power Wheels fans are going for replacement chargers. I can see why as the stock charger appears to be a constant current charge with no automatic shutoff. Leave it on for extended periods, and you have a dead battery.

There's also some advice on batteries and chargers on the FAQ: Looks like a good place to start reading.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Yeah, that would be nice. However, I have a different formula for asking questions:

  1. What problem are you trying to solve? A one sentence description is sufficient. Details can come later.
  2. What do you have to work with? Hardware, software, versions, makers, models, photos, etc. Numbers please, not prose. Also test equipment available, level of expertiese, and such.
  3. What have you done so far and what happened?

There are plenty of other things that would be helpful, but these are the basics.

Yeah, but I like off topic questions. It suggests that the OP is either clueless, lazy, or both. That makes it easier for them to accept my guesswork and pontifications.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

There's something wrong with the chart for state of charge someone posted. Lead-acid has a negative cell voltage tempco...

Reply to
bloggs.fredbloggs.fred

e how long to charge ?

That's a standard 0.1C trickle charger. C is battery capacity 9.5AH, chargi ng current in amps is 1/10 C, so ideally charge time is C/(0.1C)=10 hrs. Problem is battery does not store all the charge passed through it, so you need to add about 25%, that gets you about 12 hours. It is one of the best ways to charge because nothing is real critical as far as damaging battery with overcharge or reducing battery life.

Reply to
bloggs.fredbloggs.fred

long to charge ?

Yes, with a rule of thumb type approximation: The amount of charge you put back into the battery needs to be about 1.2 times as much as you took out of it.

So if you know how much charge your charger puts into the battery per unit time, divide that into 1.2 times the amount of charge taken out to get an idea of the total time needed.

All of that goes out the window with a modern variable rate charger and/or if you don't know how much charge was taken out or the rate of charge supplied by the charger or if the battery has been damaged etc etc.

Ed

Reply to
ehsjr

Lead-acid has a negative cell voltage tempco...

I checked every message in this thread. There's no chart and no mention of lead acid battery temperature coefficient. Maybe a different newsgroup or thread?

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Lead-acid has a negative cell voltage tempco...

Didn't you post this?

"This might help: About 14 hrs and no more, assuming a totally discharged battery."

The chart is there.

Ed

Reply to
ehsjr

---- Fuck you, pissant.

Phil's right and you're not only wrong, you're out of the running.

--
JF
Reply to
John Fields

Jeff Liebermann schrieb:

Hello,

it is not necessary to multiply with 12 V and then to divide with 12 V again.

9.5 Ah/(1 A * 0,75) = 12,66 h will do.

Bye

Reply to
Uwe Hercksen

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