Battery Monitoring what numbers to use

[NoResults]

When fully charged says 12.8 V 100% charged. Another time it says 12.2 V and 94.2% charged.

If I read a typical chart it says that 12.2 is 60% charged not 94.2% so what good is the % of charge indication.

I just want to keep the batteries in good condition and fully charged them at 12.2V.

Dave

[OTRA15]

Not sure if you are getting the Volt and Percentage figures from the same monitor? Ours only shows volts FWIW, so I will comment on this side of the equation. Just one lay person's opinion.

After you charge your batteries, and wait one hour after unplugging shore power, the general rule of thumb is that your monitor should show 12.8 volts plus or minus. The batteries should then hold a charge above 12.5 for 2-3 days, assuming you do not use any 12-volt items.

When the batteries get down to 12.5 volts, they are still holding about 90% charge. When they get down to 12 volts or so, they are then at 50% and you start to do serious damage to them if you use them further without charging. We always try to keep ours above 12.5 volts, as we have a quiet Yamaha tri-fuel 1000 watt generator, which is easy to hook up and run without disturbing the neighbors.

I am on the road right now, but will post reference material and a chart when I get home in an hour or two.

Peter

PS edit -- have not read your other thread yet, but for every one's information:

http://www.airforums.com/forums/f449...ll-155393.html

[GenXair]

The best investment I made when getting my trailer is the Garmin RV GPS. Highly recommended.

[55AS]

Originally Posted by GenXair

The best investment I made when getting my trailer is the Garmin RV GPS. Highly recommended.

Perhaps...

[OTRA15]

GenXair did you mean to post in another thread perhaps?

[NoResults]

I should of been more clear. I added the Victron Battery monitor which gives
the following info

batt voltage, current (amps) power (watts) consumed amp hours, state of charge time to go (h) estimate of how long battery can support current load till neading charge., batter temp

I thought would gain some valuable information but now I am a little confused.

[OTRA15]

I would recommend going back to the other thread for continuity purposes. I saw some posts by Lewster, the resident expert here, about information overload. We are re-inventing the wheel with Lew on board already on this trailer, in my personal opinion.

Good luck!

Peter

PS -- Edit -- yup here is the post:

Originally Posted by lewster

I would add the 702 and even go a step further with the new Color Control Monitor as well. They will give you more information that most can use, but it's great having information overload!

PS2 -- Here are the resources I mentioned earlier -- FWIW for continuity on this thread:

http://www.marxrv.com/12volt/12volt.htm
Voltage table on its own: http://www.marxrv.com/12volt/voltchart1.gif

[Rocinante]

One thing for sure...the most reliable measure of your battery voltage is *at* the battery. We have a solar panel that reports voltage, and it's regularly at least 0.2V low. The See Level II monitor seems to vary from being on target to being 0.1V or 0.2V low. So, sometimes we think the battery is lower than it is. So I got out to the tongue and measure it. In fairness, I should also say that we don't have a shunt or a measure of amp hours going in / out of the batteries. I just go out there with a volt meter. Some day...

[Zil]

"I should of been more clear. I added the Victron Battery monitor which gives
the following info....."
The Victron measures amps-in / amps-out to track state of charge. I use the % scale on mine. All the negatives must go through the shunt. Then the meter must be set to the proper specifications for your battery bank.
One way to determine 100% charge is how many amps are the battery accepting at 14.++ volts. Maine Sail has a very good article about this. http://www.marinehowto.com/

[lewster]

Just a quick note about the chart above. This is applicable for many LIQUID CELL batteries but does not apply to many AGMs, especially Lifelines, which are 100% at 12.8-13.2VDC and 50% at 12.2VDC.


Lew Farber