Is my battery charged yet?

[pixurit]

I am dry camping, using mainly 12V power and inverters.  I run the generator to recharge the house batteries.

How do I know when the batteries are fully charged?  I want to get a full charge but not run the generator any more than I have to.  Is there a simple gauge I can install that will tell me when the batteries are full?

Thanks for your help.

 

[Tom]

If you're using a simple charger, the most accurate way of telling the state of charge of your batteries is with a hydrometer. You can pick one up at an auto parts store. Not very convenient, especially if your batteries are tucked away in a hard to reach place.

 

[Lou Schneider]

Or get an automotive ammeter and put it in line with the battery.  When the charge rate approaches zero the battery is charged.

 

[pixurit]

I like the ammeter idea.  Now to figure out where to splice it into the wiring.  I'm thinking that right at the inverter/charger would be best.  Of course that is tucked in under the fridge, behind the 120V breaker panel and 12V fuse panel, surrounded by wiring.  Almost, but not quite, totally inaccessible  :.  Oh well, it'll give me a chance to see if my unit has the Charge Wizard that people seem so impressed with.

I agree that a hydrometer will give the best, most reliable, reading of battery condition and state of charge.  However, I really don't want to go under the hood and fuss with battery acid multiple times until I find that the generator has finished charging the batteries.

I was actually hoping that someone made a monitor panel similar to the info available on a laptop computer.  Oh well  .

Thanks for the tips.

 

[Jim Godward]

Dave,

there are  multile panels for monitoring the batteries.  I have a Trace 500, they are now up to 500A, and it covers battery status very well.  There are others like the LINKs 1000 and ???.  check the Xantrex site or any of the solar power sites for more options.

They are not cheap however.

 

[Tom]

Dave, I didn't suggest one of the monitor panels such as the ones Jim suggested because of the cost. They also involve additional wiring.

An alternative, but less reliable/accurate, method would be to use a voltmeter. See the voltage vs approximate state of chanrge for a 12V battery in this file on Battery charging basics in our forum library.

 

[PhilsFrontier]

Dave, I didn't suggest one of the monitor panels such as the ones Jim suggested because of the cost. They also involve additional wiring.

An alternative, but less reliable/accurate, method would be to use a voltmeter. See the voltage vs approximate state of chanrge for a 12V battery in this file on Battery charging basics in our forum library.

This has me somewhat confuse Tom. When checking my 12v battery, I was getting reading into the 13's on the multimeter. I also just purchased a few 30 watt solar panels from Canadian Tire which came with a charge controller which has a cut of voltage of 14.2 I believe.
Can you or anyone ched light on this for me?

 

[Tom]

Sorry, I should have explained. If you measure the voltage while on charge, you'll read the charger voltage which, by neccessity, is higher than the battery voltage. I also should have explained that, if you measure the battery voltage immediately after turning off or removing the charger, the voltage will appear higher than it actually is due to some surface charge. This surface charge bleeds off after a period of the battery being disconnected from the charger.

 

[rbell]

Tom's right, here are a couple numbers that may help you understand it. A dead battery (fully discharged) will still measure about 11.7 to 11.8 vdc. A fully charged battery after a rest period will measure 12.6-12.7. The rest period bleeds off that surface charge. Most chargers will charge between 13.5 & 14.5 vdc. So called smart chargers will drop back to about 13.1 when the battery is fully charged.