Originally Posted by steverkemp
It was while the gen was off. I wonder if it was a surface charge. This so makes me want to get a perm voltmeter installed!
Voltmeters are not what you want. A battery monitor like the victron above OR the trimetric will do the job and is really a necessity if you boondock and want to take care of the batts.
If you don't boondock....you don't need to spend the $150 bucks or so. You DO need to understand charging and measuring state of charge.
- Your converter is probably a 55 amp model...if it is the current FR standard. Worth checking.This works off shore power or your generator. It does NOT put 55 amps into your batteries. The batteries limit how many amps it can deliver since wet cells cannot take more than 20% of their rated amp hours. (Example...my Georgetown came with a pair of group 24 batts which each have 75 amp hours...total 150 amp hours and an acceptance of 30amps maximumbased on the 20% rule. (Despite my 55 amp charger.) Check to see what size converter you have and what size batteries to know what your capabilities are.
- You should never discharge a battery below 50% charged or you will begin losing cycle life. This means in my case that I have 75 amp hours to work with if NOT plugged in and charging...before I need to re-charge (hence the importance of a true monitor if you boondock since you need to count amp hours used and remaining...not volts! )
- So...if you were me and trying to replace 75 amp hours at a rate of 30 amps max....you'd figure about 2.5 hours through simple division and you'd be wrong. It takes as long to get the battery from 80 to 100% full as it does to get it to 80%. Figure 4 hours minimum.
- You cannot measure voltage properly while things are on in the coach, or while it is plugged in or within 24 hours of charging. Solution...after charging for 4 hours ...disconnect the negative battery cable and wait 24 hours...then take a voltmeter reading AT THE BATTERY TERMINALS to see the true voltage... use my chart in the post above to determine state of charge and battery condition. If you regularly can't wait the 24 hours...then you need a battery load tester which quickly wipes out surface charge and lets you take a true reading. AGAIN the battery should be disconnected from the coach when doing this.
$20 bucks ...Harbor Freight
- Hope this helps you out.