I charged my battery incorrectly

[HanksB3B]

Darn it I thought I had my Sears charger set correctly but when I went down to check it tonight somehow it was set on 2 amp 12 volt and not 4 amp 6 volt. The light was orange indicating a low charge. As soon as I flipped the switch over to 4 amp 6 volt the indicator turned green. I turned my dome light on and it seemed maybe brighter than usual.

1. Did I harm or burn out my battery? (I had the ground terminal disconnected while charging so I don't think I could have harmed anything else)

2. If I start my truck tomorrow will it harm anything? (can a 6 volt battery actually store 12 volts in it if charged that way?)

Lastly, what would happen if I charged a 12 volt battery with the switch set to 4 amps 6 volts (I'm batting 1000 here...)

Thanks,

Hank

Edited July 29, 2011 by HanksB3B

[Merle Coggins]

Over charging a battery will usually over heat it and possibly boil off some of the acid. The fact that you used a low amperage may have helped, but you still may want to check the fluid level in your battery now that it's cooled down. You certainly didn't do it any favors, but it may still be usable.

If you had done things the other way, charge a 12v battery on 6v setting, you wouldn't be charging it up at all.

Merle

[coW52Dodge]

A battery is charged by sending a current through it at some predetermined level, usually 10 percent of its capacity. When you charge it at that level for 10 hours, you end up with a fully charged battery. If you charge at 20%, it will take 5 hours, 50 percent for two hours, etc.

Of course, levels like 50 percent are likely not safe. because they can only take but so much current going through it for a given time without heating up. Ten percent a safe level and 5% (2 amps, in your case) is perfectly safe but you charged at that level for too long of a time.

The maximum current that can go through it is determined by the battery's internal resistance.

Dumb chargers just limit the current by putting a resistor in series with the charge but the smarter chargers are current limited in that they only allow a max current to flow. In your case that is 2 Amps. You did run it at that level for a time longer than normal so more current was allowed to flow while the battery was already charged.

That level could have caused a dangerous condition to exists because it releases more than normal levels of hydrogen gas in the process. It could also damage the battery.

A battery rated for 6V can't retain a 12V potential so that shouldn't be a problem.

Long story short, I'd discharge that battery safely by loading it with a 6V lightbulb for a while and then just carefully recharge it. Keep your eye on it while it is doing that and make sure it doesn't get hot. Maybe recharge it outside or in an area where it can vent well.

If it takes about 10 hours to recharge that battery, it should be okay.

Edit: Merle's absolutely right about checking the fluid level.

Edited July 29, 2011 by coW52Dodge

[HanksB3B]

Thanks Guys. Can I connect my ground and just turn on my dome light to discharge my battery without doing harm to any other component?

I would think so because of your statement "A battery rated for 6V can't retain a 12V potential so that shouldn't be a problem."

I would also appreciate help understanding how to measure (and adjust) the Voltage Regulator. You may have seen that I keep a capped off wire so that I can polarize my regulator anytime I feel like it. I do have a kill switch on my truck and I'm still not convinced that my regulator is always charging the way it ought to. My truck is 6 Volt stock with turn signals and only has an additional brake/right taillight added. Please tell me how to measure the charge being sent to my battery and what it should read i.e. 6.2-7.0 volts or something like that. I almost feel that I should carry a spare charged battery in a good looking, lockable housing attached to my running boards. It's the one thing that has plagued me in the past. Getting stuck in some remote place really make you realize just how big and heavy your truck really is.

Thanks again,

Hank

Edited July 29, 2011 by HanksB3B

[coW52Dodge]

Thanks Guys. Can I connect my ground and just turn on my dome light to discharge my battery without doing harm to any other component?

I would think so because of your statement "A battery rated for 6V can't retain a 12V potential so that shouldn't be a problem."

I would also appreciate help understanding how to measure (and adjust) the Voltage Regulator. You may have seen that I keep a capped off wire so that I can polarize my regulator anytime I feel like it. I do have a kill switch on my truck and I'm still not convinced that my regulator is always charging the way it ought to. My truck is 6 Volt stock with turn signals and only has an additional brake/right taillight added. Please tell me how to measure the charge being sent to my battery and what it should read i.e. 6.2-7.0 volts or something like that. I almost feel that I should carry a spare charged battery in a good looking, lockable housing attached to my running boards. It's the one thing that has plagued me in the past. Getting stuck in some remote place really make you realize just how big and heavy your truck really is.

Thanks again,

Hank

It is hard to say what the voltage across the battery will be while it is charging with modern chargers because they tend to be designed to be constant current sources with some smarts built in. The 'smarts' often does things like checking the battery's health while charging.

With most modern constant current source chargers, if you set a smart charger to charge with 4 Amps, it basically drives its voltage up until it measures 4 Amps. Remember your high school physics classes where they discussed ohms law: E=IR where voltage(E) equals I(current) times R(resistance)? The resistance is the internal resistance of the battery. Let's assume that's 2 ohms. If you drive 4 Amps through that, you'll see a terminal voltage of 8 Volts. (2 x 4).

It is nothing to worry about: 8 volts is of course higher than your normal operating voltage of 6V but it takes 8V to make 4A flow through a battery that has an internal resistance of 2 ohms. Remember, it is the current that makes the battery charge.

As the battery is charging, its internal resistance chances some so the terminal voltage will likely changes as well, causing the voltage to change along with it. That's why it is impossible to predict what the terminal voltage is during the charging process.

All that is perfectly okay and it will continue to charge as long as the voltage on the terminals exceeds 6V.

Smart chargers 'know' when a battery is fully charged and then stop charging with the full 4 Amps and switch to a 'trickle' mode, where they send a brief current pulse through the battery once in a while - that keeps it charged, healthy and ready to go at all times. I have a couple of inexpensive chargers (Harbor freight and Sears) that all work that way so suspect your Sears charger operates the same way.

I'd make sure the battery looks healthy, with no swelling, leaking and such. Follow Merle's suggestion checking and adding to the level, if that's necessary. Make sure the battery's voltage is about 6V.

I'd put it in the truck, leave a light on for a bit to let it drain down. It doesn't have to go down all the way but you just want to see if it can take a decent load for period of time without going dead. Maybe run a head light for an hour or so.

Then disconnect the ground and try to recharge it again, monitoring that it doesn't get hot.

If that behaves normally, you're likely good to go.

Edit: please note that the internal resistance is usually a lot lower than 2 ohms - if it was, you could only ever get 6/2=3Amp out of a battery and we know that the max output current is much higher than that.

Just used that number because it illustrates the behavior well.

Edited July 29, 2011 by coW52Dodge