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What are proper battery readings when parked

After being parked for several months plugged into 50 amp AC and exercising the boost each week for 24 hours, my readings are as follows .... With boost ON: Prosine (house batt.) 13.8, Driver's info center (engine batt.) 13.2. With boost OFF:  Driver's info center (engine batt.) 12.2, (as I switch boost off, drops to 12.5 and moves through to 12.1 and settles at 12.2). Two hours later w/ the boost off during that time, the dash and Driver's info center (engine batt) read a steady 12.2.
My Optima Yellow tops (engine batteries are 8 years old).
Are these readings within the proper range? Should I make any other readings? 
r.schwab
2004 U270 36'

Re: What are proper battery readings when parked

Reply #1 –
I recommend that you measure voltages with a reliable meter at the battery terminals.

13.8 volts is at high end of the range for a maintenance charge according to recommendations on the Optima web site. Optima Battery Charging - AGM Battery Charging

If the chassis batteries quickly drop to 12.2 volts with no load as measured at the battery terminals, it is time for new ones.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: What are proper battery readings when parked

Reply #2 –
Thanks JD
Engine batteries w/ reliable volt meter read 12.57 w/o removing the cables. Why should there be a difference between the volt meter test and the Driver's info center (engine) @ 12.2?
At eight years old, I suppose new ones are in order!
r.schwab
2004 U270 36'

Re: What are proper battery readings when parked

Reply #3 –
Quote from: r.schwab –
Thanks JD
Engine batteries w/ reliable volt meter read 12.57 w/o removing the cables. Why should there be a difference between the volt meter test and the Driver's info center (engine) @ 12.2?
At eight years old, I suppose new ones are in order!

There could be a lot of reasons for the difference in voltage at the battery terminals and at a remote readout. Corroded connectors somewhere in the link would do it, for sure. Measuring right at the terminals (on the battery post... not on the part that connects to the battery post) is the best way. I also often measure between the battery posts and the connectors just to see if there is a voltage difference. Corrosion products can build up between those.

If your battery measures 12.57vdc at the terminals - and holds that voltage for a couple of hours after charging - then it seems to me that the battery is pretty good.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: What are proper battery readings when parked

Reply #4 –
Quote from: r.schwab –
Thanks JD
Engine batteries w/ reliable volt meter read 12.57 w/o removing the cables. Why should there be a difference between the volt meter test and the Driver's info center (engine) @ 12.2?

By the time it gets to the DIC it could be loosing voltage due to bad connections causing resistance. Reading off the battery is more accurate especially if you are going to make a decision to buy new ones.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: What are proper battery readings when parked

Reply #5 –
Like other said, its a long way, and a lot of connections to the dash that will effect volt readings, meter at the battery is the answer. I have another one for you running down the road Eng temp 185, oil pressure 60 psi, turn on the head lights Eng temp goes to 195, o/p to 50 psi. Lights off right back to normal.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: What are proper battery readings when parked

Reply #6 –
Read the info at this site and then disconnect each engine battery from it's neighbor and check the battery voltage at the battery post a couple of hours after charging with a digital voltmeter. Make sure to use a hydrometer also if your batteries aren't sealed. The correct hydrometer readings are also listed at the site. A bad cell in one battery can bring total voltage down but always replace both or all three in my case at the same time.

I usually disconnect ground (-) first, replace last.

Battery Charging Tutorial | ChargingChargers.com

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: What are proper battery readings when parked

Reply #7 –
R. Schwab

After my coach sits in storage for awhile with everything off and chassis battery negative cable disconnected, the Optima Red tops will always read about 12.5 and the MK gel or AGM (not sure which I have) will be about 12.75 as measured at the battery.  I think the difference is due to the fact that they are different batteries and made by different companies.  After sitting for a month the red tops can crank the engine for 30 seconds.  It would fire almost immediately except I disconnect the electrical connection to the fuel shutoff, so that some oil is pumped thru the engine before starting. (I only do that when it has not been started for more than a week.  If I didn't do that the engine would probably still outlast me.)  I believe the later model electronic engines do not fire until there is some oil pressure detected by the electronics.  My voltage indications at the dash are always lower than at the batteries.  If your chassis batteries can crank the engine without any boost, they may have some life left.  Many places that sell batteries will test them for free.  Don't tell them how old they are, but a good technician will know anyway.  It may be worth the peace of mind to replace them.
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: What are proper battery readings when parked

Reply #8 –
To reaffirm what Jerry said, and voice my frustrations - the coach gauge readings seem to have no basis in reality.  My dash gauge reads 10 volts for a fully charged battery, 12.6 measured at the battery with a volt meter.  The house battery gauges don't do much better.  As critical as battery voltages are you'd think they would have done a better job on them.  I suppose the newer models do or else it's the price I pay for being in the poortravel group  :(

1996 U270
Build #4846
 

Re: What are proper battery readings when parked

Reply #9 –
Hmm... I noticed my dash gauge is low by a volt and a half. Does anyone with the VMS-PC when used in a ISC (electronic) know if that system displays battery voltages and if they are more accurate than the in dash VDO gauge? Could provide yet another reason to spring for the system...
Don
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson