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#1678999 - 11/20/09 05:41 PM How to read the meter on a battery charger
GhostFlame Offline


Registered: 07/15/09
Posts: 424
Loc: Doylestown, Pennsylvania
Forgive me if this has been discussed.

I have a 4amp 12.6 volt battery charger. No extra settings. the meter jumps to 6 amps when the battery is drained. it moves slowly left to the lower amperage numbers after a while of charging. from left to right the meter reads 1 2 3 4 5 6

When do I know the battery is fully charged? there is no volt meter on the charger.

I had my daughter's battery on the charger for about 16 hours after she left the lights on for like 2 days. the battery jumped to 6 and after about 2 hrs settled down to 4 but never went any lower. the car started but, I would like to know.

Would my handy volt meter be a better indicater? I think 12.6 or 13.2 is the magic number when it's fully charged.

Any help , thanks
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#1679005 - 11/20/09 05:46 PM Re: How to read the meter on a battery charger [Re: GhostFlame]
EricF Offline


Registered: 07/14/09
Posts: 1640
Loc: SF Bay Area
what happens is the meter shows the amount of amps being pulled.
so when the meter was at 6amps, the battery was drawing 6amps of power to recharge itself. after a while as the capacity gets fuller, it draws less amps, so now you're at your 4. when it gets to 1 or 2, you're at a trickle, and the battery is/should be/close to full capacity.

you have a slow charger, 6amps, so charing for 16hours is normal for an extremely drained battery.

the magic number for a charged battery voltage with no load is 12.3 - 12.5volts at rest.
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#1679006 - 11/20/09 05:48 PM Re: How to read the meter on a battery charger [Re: EricF]
GhostFlame Offline


Registered: 07/15/09
Posts: 424
Loc: Doylestown, Pennsylvania
That was fast thanks!! very informative.
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#1679040 - 11/20/09 06:29 PM Re: How to read the meter on a battery charger [Re: GhostFlame]
Mr Nice Offline


Registered: 09/12/04
Posts: 16916
Loc: Orlando, FL
Eric,

what is the voltage of the battery when the engine is running ?

What is the range of voltage as the engine RPM increases to redline ?

Thanks
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#1679104 - 11/20/09 07:24 PM Re: How to read the meter on a battery charger [Re: EricF]
JHZR2 Offline



Registered: 12/14/02
Posts: 38287
Loc: New Jersey
Originally Posted By: EricF
what happens is the meter shows the amount of amps being pulled.
so when the meter was at 6amps, the battery was drawing 6amps of power to recharge itself. after a while as the capacity gets fuller, it draws less amps, so now you're at your 4. when it gets to 1 or 2, you're at a trickle, and the battery is/should be/close to full capacity.

you have a slow charger, 6amps, so charing for 16hours is normal for an extremely drained battery.

the magic number for a charged battery voltage with no load is 12.3 - 12.5volts at rest.


If your battery is 42Ah, and flat, it could take 7+ hours at 6A charge to go full. The rates do change, so in reality it takes a bit longer.

Two things though... First, the battery will charge at up to 14.1V - some may feed at a higher voltage. Even after it is full, the battery will have a "surface charge", which keeps it over 13V open-circuit.

Second, a full battery at normal temperature is roughly 12.72V at OCV.

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