Battery help please

[bolocop]

I have a hobie livewell. It's about 3 years old. Recently, I plugged the battery in to charge it and the status light on the charger stayed green. I plug in the battery after a charge but it doesn't last long.

My question is how do I tell if my battery is bad or if the charger is bad?

[YakDout]

Take a volt meter and hook it to your battery on 20vdc and report what it says.


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[rossman]

Originally Posted by YakDout

Take a volt meter and hook it to your battery on 20vdc and report what it says.


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best to check that voltage while under load. Many bad batteries will read fine until you put a load on them

[bolocop]

So I tested it and it's 6.2V. The hobie charger still reads green when I plug it in. Strange because it was dead after a day of use, I plug the charger in and it stays green but now it can run the pump. How did it charge if the light stays green. Thought circuitry would shut charger down to prevent overcharging.

Testing it under load is tough, the hobie battery contacts are covered.

Any other suggestions? Probably a new battery?

[YakDout]

To test it under load you might have to poke through the insulation on the wires a tad with the prongs on your volt meter. A few wraps of electrical tape and no worries. Or could solder and shrink tube if its a big hole and youre worried. 6.2 isnt that bad. Like rossman said though to be more accurate you should place it under load. Ive heard of the chargers going out so its not a stretch. Its beginning to sound a little like that but dont replace it until you test battery under load.

Or if your near an oex, bring your battery in and put it on one of their new chargers. Im sure they would be cool with that.


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[FullFlavorPike]

Test the charger with the multimeter?

[YakDout]

Originally Posted by FullFlavorPike

Test the charger with the multimeter?

Yep testing the output of the charger with voltmeter should work

[FullFlavorPike]

Originally Posted by YakDout

Yep testing the output of the charger with voltmeter should work

My thought is that perhaps the thing is only throwing 3.2V at 18mA or something. That would be an easy diagnosis.

I may be wrong about this, but isn't the "battery charged" indicator light just th product of some kind of diode responding to the current in the battery? When it meets a certain threshold, it shuts off power to the battery and flashes that green light.

Depending on how the charger is actually wired, there could be any number of ways in which it could fail to charge the battery, or provide a kind of false positive for reading the battery's state of charge.

My (admittedly inexpert) guess is that the easiest way to wire the charger would be that it responds to the battery's charge as compared to the current coming out of the charger. When the battery's charge is less than the charger's output, it charges, but if the charger's output is equal to or lesser than the battery's charge, it shuts down and flashes the CHARGED light. THe thing doesn't think, it just responds to the ratio of electrical forces between battery and charger. If the charger were outputting insufficient current, it would think the battery was charged, even if that were not the case.

[jorluivil]

If its 3 years old just save yourself the time and buy a new battery.

[bolocop]

Originally Posted by jorluivil

If its 3 years old just save yourself the time and buy a new battery.

Definitely thought of that, but I was worried about the charger too.

Thanks for the help, everyone!

[bolocop]

Thanks! I will give that a try when I get home! So if it's not reading anywhere near 6V, I need a new charger, right?

Originally Posted by FullFlavorPike

My thought is that perhaps the thing is only throwing 3.2V at 18mA or something. That would be an easy diagnosis.

I may be wrong about this, but isn't the "battery charged" indicator light just th product of some kind of diode responding to the current in the battery? When it meets a certain threshold, it shuts off power to the battery and flashes that green light.

Depending on how the charger is actually wired, there could be any number of ways in which it could fail to charge the battery, or provide a kind of false positive for reading the battery's state of charge.

My (admittedly inexpert) guess is that the easiest way to wire the charger would be that it responds to the battery's charge as compared to the current coming out of the charger. When the battery's charge is less than the charger's output, it charges, but if the charger's output is equal to or lesser than the battery's charge, it shuts down and flashes the CHARGED light. THe thing doesn't think, it just responds to the ratio of electrical forces between battery and charger. If the charger were outputting insufficient current, it would think the battery was charged, even if that were not the case.

[PescadorPete]

With no battery connected, charger reads about 6.8V. With a fully charged battery attached its about 6.5V. When I connect the pump, it drops to about 6.2V. I don't know what it would read with a discharged battery connected, I'll check next time I have to charge it up.

[bolocop]

The charger is reading 7.5V so the battery is toast. Like someone said,it's a 3 year old battery. Time to cut off the connector and buy an Amazon 6V 10amp/hr battery.

Thanks again for all your help!