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Discussion Starter #1
To prevent overcharging and damaging my car battery I'll be checking it every 1/2 to 1 hour periodically when I place it on a charger. I've read on the web that dont let the battery get hot to the touch. How hot is hot to the touch? Is it like a high fever hot? Can someone let me know before I start charging my battery. Also I'm using a 10 amp simple, not a smart, charger so I'll need to check on it periodically during the charging process.
 

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If you hear any bubbling of the electrolyte, you are getting gassing (which is explosive!). You might want disconnect the charger for 30 minutes if you hear rapid bubbling or if the case on the top is quite warm. If the battery top case is quite warm definitely back off or you will shorten the life of the battery. If it is so hot that you want to pull your fingers off after touching it, disconnect your charger quickly and wait 30+ minutes before reconnecting it.

Make sure that you add distilled water (don't flood it) if the electrolyte level is low and near the plates, and check the level periodically during the charging process.

The generation of heat and bubbling depends on the condition of the battery and how badly it has been discharged. A deeply discharged or deteriorated battery may got hot quicker than a good, slightly discharged one.
 

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Discussion Starter #3
Thanks John. Now I know when to back off on the charger. Also, if I need to add water how high should I fill it to be sure that I don't overfill because there is no level indicator on the battery housing.
 

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Most modern batteries are sealed and aren't serviceable. There have been too many injuries. Wear safety glasses. If the caps are removable, you should be able to see a 'cupped' appearance of the electrolyte ~1/2" above the plates.
Watching the current draw on the charger will give an indication of the charging rate and the heat to expect. I would only want a battery to get slightly warm to the touch.
Rapid charging can damage a battery and create a dangerous situation as can a shorted cell. Provide plenty of ventilation and keep sparks and open flame away. Hydrogen gas is explosive.
If the battery doesn't accept a charge, sometimes a slow charge over a few days can bring it back. A taillamp bulb in series with the terminal and charge clip will limit the current draw to a safe level.
If you suspect that the battery is defective, exchange it for another one.
 

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KOG
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Use a 2 amp setting and no problem. It will take at least overnight to fully charge on that way, but it's safe for you and won't damage the battery.
 

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+1. Fast charging reduces the life of a battery noticeably. Charge at 2 amps for 24 hours and you should be good to go, and no fear of it getting even warm.
 

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To be specific about it...

122[sup]0[/sup]F or 50C electrolyte temperature, is the limit at which all charging should cease in a standard, flooded lead acid battery. The advice above regarding recharging at 2 amperes, is sound. i terminate 2-amp charging when voltage reaches 15.0. I am a retired lead acid battery design engineer.
 

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Discussion Starter #8
Thanks for the advice. I'd like to charge at a lower current level but my charger is fixed at 10 Amps so I will have to monitor the battery during charging. I will stop when it gets warm at the top or at the middle cells or when the electrolyte sound like its boiling (gassing). Also does anyone know what open circuit voltage level I should get after letting the battery settle for about 4 to 6 hours after charging? The web shows ranges from 13.2 to 12.6 volts.
 

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The real test of a battery isn't the voltage measurement, but the 'work' that it can perform under load.
The battery will hold a 'surface charge' after charging and some testers ask that you turn on the headlamps for a moment before you resume testing in order to get a valid test result. The momentary load should remove the surface charge from the battery.
http://www.smartgauge.co.uk/surf_chg.html
 

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KOG
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Get another charger.
 

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+1. Harbor Freight has a good Chicago brand charger for about $30, it has a 2 amp and 6 amp rate, and automatically scales down the charging as it tops off.
 

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Discussion Starter #13
Or simply place a 12 volt bulb in series. This will limit current.
As the bulb dims, the battery is nearing full charge.
I think I'll go with your solution to let me know when the battery is nearing full. I'm thinking of using an interior dome light because it's an inline type that I can splice and solder into one of the charger leads. Would it be safer to splice the lamp into the negative or postive lead wire of the charger?

As for getting another charger, family and friends will now know what to get me for Christmas. :thumbsup:
 

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I was getting ready to reply, when I saw Dave Eidell chimed in, with the info I learned from him on another forum.

2 amps for 12 hours is not enough to fully recharge larger batteries which were totally depleted though.

And many automatic chargers will not even try to charge a battery whose voltage is under 10.5. A good battery should first be paralled to it, then the auto charger connected.

I doubt a starting battery will recover from such abuse( extended time resting at or below 10.5 volts)
 

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KOG
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The trick to charging with autochargers is to put them onto engine start for a minute or so to get enough voltage in the battery so they'll charge.
 

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2 amps for 12 hours is not enough to fully recharge larger batteries which were totally depleted though.
That's why I said 24 hours. And yes, it may not recover anyway. But it's worth a try.
 

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Well, very possibly even 24 hours would not be enough to fully charge on the 2 amp setting. No snarky tone intended.

I have a group 27 rated at 115 amp hours.(12.75"x6.75"x9") 62 lbs. Most starting batteries are much smaller and are around 84 A/h. I am not sure what size battery is in the OP's vehicle.

If MY battery were still newish and healthy but accidentally discharged 100% to 10.5 volts overnight, If I then put a 2 amp charger on it that actually puts out 2 amps , starting it at 10.5 volts(rested), it would not even be 50% charged after 24 hours.

If this battery was older and more sulfated it might only have 65 amps hours left, so then 2 amps for 24 hours would indeed bring it closer to 100%

And that is not including charging inefficiencies or the fact that the 2 amp charger is likely going to start tapering to 1 amp well before then.

A temperature corrected glass hydrometer is the best tool for a flooded battery.
A voltmeter a distant second, and relying on the accuracy of the ammeter on an old manual charger behind that.


My Manual Schumacher on the 10 amp setting has never gone above 7.5 amps according to my modern digital ammeter.

The 2 amp setting measured 1.8 amps when starting charging at 12.4 volts.

Think of an aging battery like a 15 gallon fuel tank which just keeps getting smaller with age.
After a few years, or a few months of abuse(chronic undercharging)
You can still fill it up, but it might only take 3 gallons to do so and then only has 2.5 gallons to dispense, and you need 1.5 gallons to start the engine.
 

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Hydrometer is great, BUT. Many (most) batteries now are sealed so that's not going to work. And putting a hydrometer in the hands of people who don't know which end of a screwdriver has the point on it is a recipe for disaster.
 
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