Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 12, 2025 ...

Over-Charge in Amp-Hours values

September 12, 2013, 01:46:18 am

I've been plugged into shore power for about 4 months now. Initially, the amp-hours reading was approx. -330, and over time the charger did its thing to  make that value climb back up to zero (and the flashing lo-battery message then went out)

Now I have a positive value of 12 showing in amp-hours, 13.62 volts as a charge rate, and .1 amps.

I read the manual and it states a little displayed over-charge value is normal, but doesn't give any more detail. This has been increasing by a value of 1 each day since it reached zero.

I have all AGM batteries in the Coach that are about 10 months old. I want to make sure that I'm not harming the batteries with this over-charged state.

Can anyone comment on their experience with this situation?

The unit above the door is the original "Amp-Hour +" factory installed unit made by Cruising Equipment Company

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Re: Over-Charge in Amp-Hours values

Reply #1 – September 12, 2013, 05:18:22 am

I wouldn't worry about your numbers.  My coach does the same thing.  It just resets when I disconnect from shore power and replug in next time.  Your biggest problem is your coach isn't moving!

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Reply #2 – September 12, 2013, 06:05:17 am

I agree with Brett.  The amp-hours calculation drifts with time.  It integrates amps over time and needs to be reset periodically.  How it gets reset is a function of the particular gauge.

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Reply #3 – September 12, 2013, 07:39:35 am

Michael
13,62 volts may be a little high for the float voltage setting.
You can check with your battery manufacture for their recommended float voltage just to be sure that's OK.

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Reply #4 – September 12, 2013, 09:16:46 am

Reset and accept as normal.

Brett

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Re: Over-Charge in Amp-Hours values

Reply #5 – September 12, 2013, 02:04:18 pm

I am surprised in this thread that no one has mentioned that recharging a discharged battery uses more amphours then the number of amphours which were used. The lower the discharge, the more inefficient recharging is. Recharging an 8D battery after discharging it 20 amphours (circa 10%) will require about 35 amphours. Recharging a battery from 50% to 60% charged (20 amphours) will require about 25 amphours. This is because the recharging efficiency for recharging from 90% to 100% is only 50-60%, while recharge efficiency for recharging from 50-60% is almost 90%. If an 8D battery is discharge by 100 amphours (50%), recharging will require 140 amphours.
 
An amphour meter is built to count all amphours out but not all amphours in. Newer amphour meters allow adjustment of the recharge efficiency in an attempt to display zero amphours when the battery reaches full charge. The recharge efficiency is affected by the type of battery as well as the condition of the battery and the condition of the battery is affected by by equalizing or desulfating. All amphour meters require periodic resetting.

How to know your battery is fully charged involves "shades of gray". The most accurate way is using a hydrometer. This is not possible with the sealed batteries which most of us have. Using voltage alone to determine "state of charge" is not very accurate unless you know what has been happening to your batteries and know what type of batteries you have.

The float voltage for a fully charged battery will depend on type and condition. Float voltage will vary from 13.2 to 13.8, but is generally considered to be good at 13.4 with sealed batteries. My batteries float at 13.5 or 13.6 volts because I am using desulfators, which causes battery voltage to rise.

I have set bulk voltage to 14.6 for solar but only 14.4 for alternator. The amps from solar is limited by the solar panels while the amps from alternator are not.

After charging, check your batteries to see if they are hot or bulging (charging too fast).

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Re: Over-Charge in Amp-Hours values

Reply #6 – September 13, 2013, 08:15:49 pm

Thanks for the excellent explanation, Wyatt.

Disconnecting from Shore Power -- waiting a few minutes -- and then plugging back in did not re-set the amp-hours to zero. I had to remove the unit and disconnect the red wire at the spade connector. Again -- waited a few minutes and re-connected, and now it reads zero.

My float voltage is 13.67, and the amps displayed fluctuates from zero to .1

My Solar panels interior display unit read-out (analog meters) during the day now is 13.2 volts and .8 amps.

I did check all the batteries for heat and/or bulging. Everything appears good.

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Re: Over-Charge in Amp-Hours values

Reply #7 – September 14, 2013, 03:36:29 pm

I drilled a small hole in the panel and installed a "normally closed" push button temporarily disconnect on the "+ lead" of the original Amp-Hour meter installed by Foretravel. This allows resetting to ZERO, without taking the meter out.

The other amp-hour meters which I installed have reset ability already. These new meters are much better at showing ZERO amp-hours when the batteries are fully charged.

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