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Topic: House Batteries Overcharging? (Read 204 times) previous topic - next topic
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House Batteries Overcharging?
We’ve been on the road for about a month.  Just this morning, my house batteries showed a 109% charge.  By midday, 110%.  They now show 113%.  I don’t recall ever seeing a reading above 105%.  According to my battery meter, it’s still being charged now.

We’ve been under heavy clouds with rain all day, and the sun set about 3 hours ago, so the charge isn’t coming from my solar.  Is this a normal situation, or is there a problem brewing here? 
Still pretty new to RV lifestyle & Lazy Daze
2014 27’ MB
Two beautiful Weimaraners, Junie & Pearl (now our angel dogs)
 
Re: House Batteries Overcharging?
Reply #1 –
Where or what is providing you with these readings? I have never seen a 100+% reading on any battery monitor.
A bit more information would be helpful.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: House Batteries Overcharging?
Reply #2 –
Quote from: Larry W  - 
Where or what is providing you with these readings? I have never seen a 100+% reading on any battery monitor.
A bit more information would be helpful.

Larry

I have a battery meter, Bogart Engineering TM-2030-A.  The batteries are AGM.  This morning it shows the batteries back to 102% charge status.  Last night, that (along with two other on-board meters) showed the house batteries at 13.6V.  This morning, 13.2V.  I typically see about 101% while in storage plugged into AC power.  On a sunny day, it will typically run up to about 102%-104%. 

We are plugged into AC power now, so the 102% morning reading seems pretty normal—maybe very slightly high. There would have been almost no DC load overnight, so I was surprised but relieved to see more normal readings today. 

Jay

Still pretty new to RV lifestyle & Lazy Daze
2014 27’ MB
Two beautiful Weimaraners, Junie & Pearl (now our angel dogs)
Re: House Batteries Overcharging?
Reply #3 –
Since the Bogart unit is an amp counter, its accuracy can drift over time as your batteries lose capacity with age. This type of battery monitor needs to be recalibrated every year or so, and in particular, have their battery capacity (total amp-hours) value reduced to reflect the batteries' gradual loss of capacity. So you might want to ask yourself how old are your batteries, and when was the last time you recalibrated your Bogart meter. If you haven't done that in the last year, now might be a good time.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: House Batteries Overcharging?
Reply #4 –
Quote from: Andy Baird  - 
Since the Bogart unit is an amp counter, its accuracy can drift over time as your batteries lose capacity with age. This type of battery monitor needs to be recalibrated every year or so, and in particular, have their battery capacity (total amp-hours) value reduced to reflect the batteries' gradual loss of capacity. So you might want to ask yourself how old are your batteries, and when was the last time you recalibrated your Bogart meter. If you haven't done that in the last year, now might be a good time.

Thanks…the batteries are about 5 years old & I’ve never calibrated the Bogart meter.  I’ll review the documentation & follow your advice when we return home later this week.
Still pretty new to RV lifestyle & Lazy Daze
2014 27’ MB
Two beautiful Weimaraners, Junie & Pearl (now our angel dogs)
Re: House Batteries Overcharging?
Reply #5 –
Here's another thought. AGMs, like all lead-acid batteries, have a fairly high series internal impedance that is temperature sensitive. When charging quickly - such as a good solar day - some of the charge put into the batteries gets dissipated as heat, rather than accumulating charge. If the monitor was calibrated based on a sunny day, then the slower charging of a cloudy day, where a higher percentage of charge does not go into heating the battery, you would get a miscalibration of the reading resulting in higher than 100%. This is why most battery monitors have an auto-synchronization function that will correct the readout to 100% when it determines the batteries are fully charged. They do this by testing when the charge current falls below a certain level (tail current) for several minutes, then resetting to 100%. Your meter at least should have a manual way to do this.

Steve

ps. Lithium batteries have such a low internal impedance that they are relatively unaffected by this.
2004 FL
2013 Honda Fit
Re: House Batteries Overcharging?
Reply #6 –
Very interesting; thanks, Steve!
2003 TK has a new home
Re: House Batteries Overcharging?
Reply #7 –
This is an interesting thread. I have had three Trimetrics and none ever displayed over 100%. After calibration it would always get up to 100%. I never paid any attention to degradation of the batteries. I wonder if others with Trimetrics ever see a higher than 100 reading?
jor

09 27' MB
10  Suby Forester