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Electronics => Electronics => Topic started by: gamefreak on January 27, 2008, 09:33:23 PM

Title: Is this battery "dead"
Post by: gamefreak on January 27, 2008, 09:33:23 PM

I have an old 7.2 volt 1500 MaH battery here, and a multimeter reads 1.4 volts, is this battery in the doomed deep cycle?

Title: Re: Is this battery "dead"
Post by: Trumpkin on January 28, 2008, 09:25:37 AM

have you tried recharging it? also if you scroll about half way down this page http://blog.makezine.com/archive/make_podcast/2.html you will see joule thief you might be able to use that to get a little more life out of your battery. :)

Title: Re: Is this battery "dead"
Post by: Admin on January 31, 2008, 09:24:16 PM

What type of battery?

Probably doomed, but I'd try to save it anyway. Just charge it up and see what happens . . .

Title: Re: Is this battery "dead"
Post by: gamefreak on February 03, 2008, 02:56:29 PM

NiCD

I ripped off the plastic casing because it appeared that some wire insulation was falling off and the wires very close to touching, rewrapped it with ducttape, checked its voltage, .5 volts, put it on my charger at ~.75 amp hour, and it finished charging withen 20 minutes(should have taken two hours), and checked the voltage,it read 8.06 volts, seems very strange.....

I then switched over to amps and it measuered 1.5 amps, steadily dropped and I then stopped at .4 amps, switched back to volts, and the battery steadily rose from 5 volts to 6.6 volts when i stopped measuring, this battery is magic.....

Title: Re: Is this battery "dead"
Post by: Admin on February 03, 2008, 05:47:49 PM

The voltage on a battery isn't fixed. When it says 6V rating, that doesn't mean it is ever actually 6V. As a battery is drained, the voltage drops too.

The voltage is dependent on the internal charge level (measured in mAh). A battery that can't hold a charge (which effectively has a low mAh), will drop in voltage much faster.

I know some types of lead acid batteries can be 'saved' by charging and discharging it a few times (its a chemistry thing, too lazy to explain). NiCads however I'm not sure . . . worth looking up, or experimenting to find out . . . but I think your battery is dead . . .

Title: Re: Is this battery "dead"
Post by: Trumpkin on February 03, 2008, 05:58:52 PM

yep definently dead, buy another one, all battery is having a sale http://www.all-battery.com/ .

Title: Re: Is this battery "dead"
Post by: gamefreak on February 03, 2008, 06:08:09 PM

If i set my multimeter on amps and and just connect it to the battery, will it give me the MaH?

Title: Re: Is this battery "dead"
Post by: Trumpkin on February 03, 2008, 06:09:02 PM

depends on if your multimeter reads mah.

Title: Re: Is this battery "dead"
Post by: Maltaeron on February 04, 2008, 07:52:24 AM

It will be pretty obvious which one it is. VERY good batteries might have around 2 aH, or 2000 mAH. If yours is not in the decimal places, it is being measured in mAH. Also, next time grab some niMH batteries so that you don't have to worry about the memory effect of niCads.

Title: Re: Is this battery "dead"
Post by: Admin on February 04, 2008, 08:12:37 AM

Quote

depends on if your multimeter reads mah.

For those who didnt catch trumpkin's clever sarcasm, no, you can't measure mAh with a multimeter. ;)

The way to do it is charge up the battery, put a current sensor data logger on it, and measure the current in time it supplies with a resistor across the leads.

Title: Re: Is this battery "dead"
Post by: Trumpkin on February 04, 2008, 01:04:39 PM

I'm suprised no 1 else got my joke.

Title: Re: Is this battery "dead"
Post by: ed1380 on February 04, 2008, 03:02:25 PM

o we got it all right.

Title: Re: Is this battery "dead"
Post by: HDL_CinC_Dragon on February 04, 2008, 05:48:45 PM

aw crap I didnt notice hahaha
my mind automatically dropped the 'h' lol