I have 2 6v batteries that are not on slide out trays so for 8 years I have been checking with a volt meter. I wired the pos and neg with 2 wires that I can easily check from inside the MH. I have no room to fit my temp compensating bulb hydrometer to check above the batteries so I bought a WM short floating needle type which is only 6 ins long that I could fit in above the batteries. Which I use on occasion which always read 1.300 when the volt meter read 12.7v. I decided to test it with distilled water last week and it still read 1.300. I post this for others that have no room for a real hydrometer reading. Has anyone figured out a way to take readings without removing the batteries?

Of course the best sure way is to use the hydrometer method. I however use this chart to get me in the ballpark of the battery state of charge when I am camping off the power grid. It of course is approximate but served me well over the past few years of re-charging my batteries when they hit 12.0VDC back up to at least 90% SOC. I can do around 12-14 daily runs of these 50% to 90% charge states and them I must do a full 100% state of charge to keep from doing damage to the batteries...My 255AH capacity of Batteries are just now dropping off in performance since installed in 2008.

1.300 seems kinda high to me. Should be more like 1.275 or even 1.285.

That chart doesn't tell you anything unless the system is completely unloaded for 2 days.If you are experienced at dry camping, and know your rig's battery/charging system well, all you need is a digital volt meter mounted where you can see it all the time, and connected near the batteries. Then I can assure you it won't take very long for you to know what voltage you should be seeing under a given load.For instance, my volt meter is at my tv where I can see all the time, and w/ the tv/sat playing, and a couple lites on, as long as I don't get below 11.2-4, I know I'm in good shape, and most times it settles down and stabilizes at 11.8 for several hours, before slowly going down.

RJsfishin wrote:That chart doesn't tell you anything unless the system is completely unloaded for 2 days.X2, very true. I'll add when camping, the closest you'll get to a resting voltage will be in the mornings before you start running stuff. That's if you're not in an area that's really cold and your furnace is running. The furnace will pull down the battery voltage while it's running.

refractometer?mena661 wrote:1.300 seems kinda high to me.Especially for distilled water!

Checking Battery SOC | Good Sam Community

11 Replies

mena661
Explorer
Jul 20, 2013
Gjac wrote:
My point was you can't trust the WM floating needle type of hydrometer. I have been using my volt meter with the chart Roy posted, but would like to take readings with my good hydrometer but it is too long. I was looking for ideas for using it. I didn't know if anyone made some sort of flexible hose to fit on the end to reach the batteries.
Ah, I see now. I could use this too but have not come up with anything like that.
time2roll
Nomad
Jul 20, 2013
RJsfishin wrote:
That chart doesn't tell you anything unless the system is completely unloaded for 2 days.
Actually the chart is for a battery under a moderate load.

To the OP, I try hard to avoid using a hydrometer. If I was having issues with 8 yo batteries I would probably remove and replace.
Gjac
Explorer III
Jul 20, 2013
My point was you can't trust the WM floating needle type of hydrometer. I have been using my volt meter with the chart Roy posted, but would like to take readings with my good hydrometer but it is too long. I was looking for ideas for using it. I didn't know if anyone made some sort of flexible hose to fit on the end to reach the batteries.
mena661
Explorer
Jul 20, 2013
tplife wrote:
A surface charge is gone in 2 hours after charging, not two days.
Only if your batteries are bad or if you still have a load on them. It takes at least 24 hrs for my batteries to lose their surface charge in which case they indicate 12.83V. If you checked my batteries two hours after being charged, they would still read in the 13V range.
tplife
Explorer
Jul 20, 2013
A surface charge is gone in 2 hours after charging, not two days. Test the battery with a voltmeter after 2 hours of reaching full charge. If you're using a gel or AGM battery, simply use a calibrated voltmeter as a hydrometer is older technology and has its own calibration requirements.
KD4UPL
Explorer II
Jul 20, 2013
You could get an electronic battery meter. This is more than a voltmeter. A battery meter includes a shunt that measures amps in and out of the batteries. You program it for the size of your bank and other factors like charge efficiency. If properly installed and programed it can give you a pretty good reading of what's in the bank.
Bogart Engineering makes the TriMetric 2025-RV. Schnieder/Xantrex makes the TM-500A. Outback and Magnum both make units that interface with their inverters.
red31
Explorer
Jul 20, 2013
refractometer?

mena661 wrote:
1.300 seems kinda high to me.

Especially for distilled water!
mena661
Explorer
Jul 20, 2013
RJsfishin wrote:
That chart doesn't tell you anything unless the system is completely unloaded for 2 days.
X2, very true. I'll add when camping, the closest you'll get to a resting voltage will be in the mornings before you start running stuff. That's if you're not in an area that's really cold and your furnace is running. The furnace will pull down the battery voltage while it's running.
RJsfishin
Explorer
Jul 20, 2013
That chart doesn't tell you anything unless the system is completely unloaded for 2 days.

If you are experienced at dry camping, and know your rig's battery/charging system well, all you need is a digital volt meter mounted where you can see it all the time, and connected near the batteries. Then I can assure you it won't take very long for you to know what voltage you should be seeing under a given load.
For instance, my volt meter is at my tv where I can see all the time, and w/ the tv/sat playing, and a couple lites on, as long as I don't get below 11.2-4, I know I'm in good shape, and most times it settles down and stabilizes at 11.8 for several hours, before slowly going down.
mena661
Explorer
Jul 20, 2013
1.300 seems kinda high to me. Should be more like 1.275 or even 1.285.

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Checking Battery SOC

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