battery

pushtoy 2 wrote:
what is the voltage on a fully charged 12v battery

For an AGM battery here is the charge table (open circuit voltage after surface charge has dissipated):

100% SOC 12.8 volts+
90% SOC 12.7 volts
80% SOC 12.6 volts
70% SOC 12.50 volts
60% SOC 12.30 volts
50% SOC 12.20 volts
40% SOC 12.00 volts
30% SOC 11.80 volts
20% SOC 11.70 volts
10% SOC 11.50 volts
0% SOC 10.50 volts

This, among other things is why I just changed out the lower section of my converter/charger.

The Parallax Series 7300 Model 7345 is found to be unreliable and inconsistent. After boiling two batteries dry and then undercharging the new ones, i decided to install just the lower section with an upgraded 3 stage charger. The original chargers in most coaches are single stage, well mine was either not enough charge or too much.

it came with a new fuse panel and looking forward to giving it a test run next week.

Try fully charging your battery, then check voltage a couple times a day to see how long before it stabilizes. My newer batteries will read well over 13 volts resting for a month. Perhaps drawing some current from it would remove the “surface charge” so a reasonably accurate state of charge can be found with a voltmeter.

The instrument of choice is the battery monitor that counts the amp hours charging and discharging so it can display the per cent of full charge all the time.
https://forums.goodsamclub.com/index.cfm/fuseaction/thread/tid/29798122.cfm

Bordercollie wrote:
Yes, there is a "surface charge voltage" of around 13.6 volts which gradually lowers to around 12.6 volts when batteries are not being charged.

But that is NOT what you said in the previous post.

While it is not optimum to run your batteries down until DEAD, convenience is more important to me.

I refuse to get up at 3AM to start the generator just to keep the batteries from reading 12.0 the next morning.
If that shortens their life a little bit.......so be it.

My information is based on what I find when checking voltage of two deep cycle 6volt house batteries in series connected to converter/charger with motorhome connected to 110vac shore power or when disconnected from shore power and engine alternator is charging batteries. Yes, there is a "surface charge voltage" of around 13.6 volts which gradually lowers to around 12.6 volts when batteries are not being charged.(if good batteries). Voltage readings may differ depending on battery condition, state of charge, resistance in battery connections, etc. From everything I have read, running lead/acid batteries down to where lights dim is hard on any batteries and to be avoided for longest useful life.

If you have just remove it from a charger it will be higher than what others have said. If you let it "rest" for about 30 minutes it will come down.

Approximately 12.65 volts resting voltage, but that depends on the particular 12 volt "chemistry" being used.

Bordercollie wrote:
Forgot to mention, try to never run your house batteries down to 12 volts which is "dead".

MORE wrong information.
12.0 volts is about 75% discharged.....which is not "dead".

Deep cycle batteries especially won't be phased by that IF they are charged back up soon.

Bordercollie wrote:
Also, with battery not being charged, a fully charged battery should read around 13.6 volts.

Others will NOT benefit from incorrect information.
The above is just simply wrong.

A conventional wet cell battery is fully charged if it has a resting voltage of 12.6. An AGM is 12.8; some 12.9.

Forgot to mention, try to never run your house batteries down to 12 volts which is "dead". This damages battery innards and shortens useful life severely. A newish healthy battery should be fully charged but not over-charged for adequate performance and useful life. Camping while connected to shore power is best with a standard house battery system. BTW, many/most RV's do not have provision to charge the engine starting battery while connected to shore power. I added a Trik-L-Start device which routes some of the charging current from the converter charger to the engine starting battery. A simple battery maintainer/trickle charger may be used to charge the starting battery if 110vac power is available.