Battery Charger broke my Class D amp?

[johnviera]

I am using this battery charger to charge the 12V battery on my Tripath TA2024 powered portable boombox:

Duracell 2 Amp Battery Maintainer | Duracell

It is hooked via DC jack into the circuit where the battery is connected directly to the Tripath TA2024 amp.

My last amp died unexpectedly. I just replaced the amp and was getting ready to hook up the charger when I had a funny feeling. I pulled out my multimeter and read the output voltage on the Duracell battery charger... 19V !!!! WTF?

I thought this was a 12V Battery Charger? Is this why my other amp broke?
How do I charge the battery without frying the amp?

Thanks for your help.

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[johnviera]

These specs are right off of the Duracell website:

Output current 2 A
Output voltage (nominal):
Charge 14.4 Vdc
Float 13.0 Vdc
Equalize n/a
AC input voltage 115 V, 50/60 Hz
Inverter no-load current N/A
Inverter low-battery shutdown N/A

WTFF !!! ?!?!?!?!?

Sorry. I am frustrated.

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[geraldfryjr]

Yes,In order for the battery to accept a charge the charging voltage must be higher than voltage from the battery taking the charge.

Also you should never use a battery charger as a power supply unless you have some sort of filtering device such as a battery or a large filter capacitor hooked to it.

I am not sure what the input voltage range is on the Tripath amp but I am suspecting that that the extreme ripple voltage may have been what killed it.

jer :/

[Andrew Eckhardt]

Those specs only hold with the charger connected to a good battery. It must never be connected to a load without a good battery in parallel. Severely deep cycling the battery, especially if it isn't in great shape, could also allow the terminal voltage to temporarily rise too high when the charger is applied.

[geraldfryjr]

Also the spike caused when you hooked up the charger to the battery could have been high enough to take out the amp as well.
This is the same thing as too why you should have both vehicles off when you connect a set of jumper cables to both batteries.

When a large current causes an arc they also cause High Voltage spikes and it sometimes takes out the computer or other devices causing costly electronic repairs in vehicles.

jer

[geraldfryjr]

Hook the charger up First then plug the charger into the wall then you should be okay (I hope).
And unplug the charger from the wall first before you dis
connect it from the battery.
You should be much safer that way.
jer

[johnviera]

The voltage reads 14.4V when charging and 19V when just idle. Weird. That spike sucks. Is there a simple solution I could wire into the circuit to limit the spike? Something to keep it under 15V at all times?

Thanks.

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[geraldfryjr]

post #6 or just leave charger hooked up at all times and then just plug it in to the wall when you need it.

There maybe other methods as well but you said "simple".

jer

[johnviera]

Thanks for the help. I might have to just get a smaller different spec charger

[wwenze]

TA2024 shouldn't be supplied more than 12V.

Chances are, the 19V is the charger's unloaded output voltage. If you don't draw enough current from it (and with this amp you won't), the voltage will remain high.