# Volts? Millivolts? Amps?



## Williams Ex Co (Dec 25, 2007)

OK Sparkys... I bought a new battery for my HD and the directions (yeah, I read 'em!) say to charge at 500 MV for something 20 hours as I recall. My charger has three options 2A, 10A, and 50A. Which setting is correct or closest? Thanks!


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## txgencon (Jan 4, 2011)

2A - I think HD actually specifies 1.5 A is optimum. You'll want to check it before 20 hours to make sure it isn't boiling dry.


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## 480sparky (Feb 1, 2009)

Williams Ex Co said:


> OK Sparkys... I bought a new battery for my HD and the directions (yeah, I read 'em!) say to charge at 500 MV for something 20 hours as I recall. My charger has three options 2A, 10A, and 50A. Which setting is correct or closest? Thanks!



The only way a battery is going to get charged at 500 mv is if the voltage of the battery is less than that.

Do you mean 500 mA? If so, 2A is the closest you'll have, because 500 mA is ½ Amp.


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## Williams Ex Co (Dec 25, 2007)

480.... I think you caught me in my F'up. I do think the directions specify milliamps. thanks!


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## GettingBy (Aug 19, 2010)

20 hours is the "C/20" rate.

If the recommended charge rate is 500 mA then your battery must have a 20 x 500 = 10,000 mAh = 10 A-h rating, so the "C" rating of your battery is 10 A-h.

2 A is then C/5 so it should take more or less 5 hours to charge your 10 A-h battery at this rate. 

Don't leave it longer than that. Charge it outside; batteries under charge give off hydrogen, which is explosive.

You can reduce your charge rate by using resistors or incand. bulbs in series with your charger but 2 A is not too abusive for a 10 A-h battery.

Can you post specs to your battery?


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## Williams Ex Co (Dec 25, 2007)

GettingBy.... The brand name is Exide. Battery type is 10L-A2. 
Under 10L-A2 it says 'replaces 12N10-3A-2'

It does specify 500 mA for 10 hours.


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## GettingBy (Aug 19, 2010)

Williams Ex Co said:


> GettingBy.... The brand name is Exide. Battery type is 10L-A2.
> Under 10L-A2 it says 'replaces 12N10-3A-2'
> 
> It does specify 500 mA for 10 hours.


This would be 5 A-h of charge put into a 2 A-h battery. It kind of says that half of the charging energy is wasted in heating the battery and that's why you need to put twice the energy into the battery while getting out only 24 W-h.

Anyway, charging it at 2 A, the "C" rate, would be kind of abusive.

0.5 A max into a dead battery from a fully charged car battery would take a resistor of value 12.8 v/0.5 A = 26 ohms, at 6 W or so. These resistors are costly.

Instead, put a 60 W, 120 V incand. bulb in series with the battery in series with a car battery, + to +, - to -, car engine off.

The bulb will stay dark.
If you have an ammeter and the current is way less than 0.5 A then go to a 100 W bulb or a 200 W bulb.

When the HD battery reaches 12.8 V when disconnected it's fully charged. It may take all day. 
I think 11 v or so means a discharged lead acid battery but these specs are available on the Web. If you have a hydrometer it is more accurate for reading the state of charge.
Or else just use jumper cables. Once the "donor cycle" is running its alternator will charge the battery at a safe rate.

I put a fully discharged car battery across a fully charged car battery and only 3 A flowed, but the discharged battery turned out to be defective so this small current may not be typical.


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## Tinstaafl (Jan 6, 2008)

GettingBy said:


> Put a 60 W, 120 V incand. bulb in series with the battery in series with a car battery, + to +, - to -.
> The bulb will stay dark.


Would this be under a full moon, on a Tuesday?

Buy an inexpensive trickle charger and be done with it.


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## Williams Ex Co (Dec 25, 2007)

Tinstaafl............. Ya got me LMAO now! I'm figuring I'll probably have to buy a new battery now. I kinda roll with an 'If one is good two is better' mindset.... Well, I just found out that 2 amps is a little abusive so I'm pretty sure that the last few hours set on 10 amps has probably junked it.... Oh well, I'll get another new battery and trickle charger and try again!

GettinBy... Thanks for the indepth information on the battery. It is appreciated but it sounds like I have probably smoked this one!


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## Tinstaafl (Jan 6, 2008)

Well, I wouldn't automatically trash it. They can often take abuse everyone says is sure death, but keep on ticking.

I used to be exactly like GettingBy; I'd rig up some of the most outrageous affairs just to (a) save a buck, or (b) prove I could do it.

Then I finally realized that my time here is limited. :wheelchair:


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## 65535 (Jan 16, 2011)

Cheap trick for a Pb Acid battery to trickle it and do the initial forming charge is to butcher an old 12V 500mA wallwart (you know everyone has a few from dead electronic devices) get a pair of color coded alligator clips on the end of the wires and you have a trickle charger. A few hundred mA either way will just require some adjustment on minimum charge time, but you can't really hurt the battery leaving it on for extra time.

Good luck.


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## GettingBy (Aug 19, 2010)

Tinstaafl said:


> Well, I wouldn't automatically trash it. They can often take abuse everyone says is sure death, but keep on ticking.
> 
> I used to be exactly like GettingBy; I'd rig up some of the most outrageous affairs just to (a) save a buck, or (b) prove I could do it.
> 
> Then I finally realized that my time here is limited. :wheelchair:


My time here is limited to 18 years according to the mortality tables but I still try to save a buck. 
A good day is when I don't end up on the evening news. :thumbsup:

It may that the charging protocol for first time charging of small lead acid batteries is different from the normal charge/discharge. Someday I'll have to ask Exide about this.


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