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I have a couple old battery chargers in the garage that will be put out for the garage sale.



I want to check these chargers to make sure they work. Can I plug them in to 120VAC and use the DVM (on volts) to check the "output", , ,or will that blow the DVM fuse?


I'm not real sharp about some electronics, , sorry if its a dumb question.
 

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The DVM would be fine on a 20 volt scale. But I wouldn't try to check amperage. Just hook up the charger to a good battery, then check voltage across the terminals. With the charger on and with it off. Any voltage reading above actual battery voltage would indicate that it is charging. The higher the voltage, the higher the current. A battery maintainer or trickle charger may only raise the voltage to 13.5, where a 20-30 amp charger may raise it to 14+ volts. A fully charged battery should show 12.7 after the surface charge has drained off. When you see the voltage rise with the charger on shut it off, and watch the battery voltage drop to resting voltage, eventually reaching @12.7.
 

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Thanks Maynard, , , ,I'll try that


Is there any method WITHOUT using a car battery in the process??
If the battery charger is "selectable" between 6Amps and 10 Amps, is there a way to measure each to see what they're actually putting out?
 

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Amperage it a measurement of "load", the battery is the load for the charger. As voltage from the charger increases so would the load. This happens untill the battery becomes more charged, when the battery voltage increases load (amperage) decreases. Amperage will vary withe battery size and state of charge/discharge.

Some chargers have voltage controls with different settings for maintenance free or deepcycle batteries. But the ones in the 6-10 amp range are generally just a transformer and a rectifier.


There is a way to measure what you want, but it would require an ammeter. Your DVM may have this, but would be at the limit of its capacity at 10 amps. Meter would have to be in series with the load.
 

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I have a 300 amp shunt that I used for years, hook it to a battery and measure the volts across the shunt ( it has a special resistor for that ).

for a charger?
get a couple of old headlight bulbs, use them for a load.
 

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I have a 300 amp shunt that I used for years, hook it to a battery and measure the volts across the shunt ( it has a special resistor for that ).

for a charger?
get a couple of old headlight bulbs, use them for a load.
The Amp-U-Tron (digital amp/volt meter) on my bike measures volts and amps via a shunt connected to the negative battery post.
 

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Discussion Starter #7
I had four different battery chargers that were "garage-sale" material. Three of the four were checked while charging a battery and tested out as "working". The fourth one is now living in the dumpster because I couldn't get it to charge.



Thanks for the comments/help with this. Much appreciated
 
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