Crazy Battery Readings

[LHS61]

Two months ago I installed 2 new deep cycle, 6 volt golf batteries from NAPA in my Class A. I thought my battery problems were solved, but not so. All was fine when I was spending most of my nights on shore power for the first 4 weeks (right captain obvious). In the last month I have been dry camping and running the generator every 2-3 days. Then the refer started giving alarms about low voltage... at about 11.8 volts about a week ago even though I had ran genset 24 hours earlier.

 

So I read some RV books and decided to hook up MH to shore power for 18 hours. Sure enough the voltage now reads 12.6 BUT the specific gravity sets at 1.12 which indicates the need for recharging... Color me confused! Should I have gone through some break-in procedure for these new batteries? What am I missing? How long should the genset run to properly charge the these deep cycle batteries?

[AFchap]

What refrigerator do you have? The Norcold 1201 that came in my coach would pull the three 12v house batteries down to the recharge point in not much more than overnight ...no way could I have gone 24 hours or even close to it.

[LHS61]

Its a Norcold 1200 but I see that as a separate issue.... I run it on LP 90% of the time. My concern focuses on why I could be reading 12.6 volts from the battery bank and have a failing specific gravity of 1.1 reading on the hydrometer

[Rif]

Without knowing how much power you are using daily, it is hard to be definitive. Still, running the generator every two or three days is likely not enough. It depends on how long yo run it and the charge capacity of your converter (I assume that's what you are using to charge your batteries). We're going to need some more information to help you pin it down.

 

As for why the SG and the voltage are inconsistent, you could be getting a surface charge into the batteries, but not enough to get them properly charged. It will take several hours of charging to get them where they should be.

[lenp]

Was that 12.6 volts while you were still connected to shore power or after disconnecting and waiting a few minutes?

 

A reading of 13.0 to 14.4 would be expected when your still connected to shore power. Depends on what charger you have and how "smart" it is and what charge state it is in.

 

After disconnecting from shore power (or generator) and running only a small load (like a light fixture) for ten minutes, you should get a reading of 12.6 or close to that IF the batteries are fully charged. And it does not sound like they are getting charged based on your specific gravity readings.

 

This is a case where a clamp on amp meter would be VERY helpful to see what your actual charging rate. If you have a one of the low end converters that come on many entry level RVs and only put out 6-7 amps and assuming you have two 6 volt batteries with 200 Amphour rating (that is still only 200 at 12 volts) you would need to be connected to shore power or run your generator for 28 hours to bring a fully discharged battery back to full charge. Unfortunately, if you have totally discharged it, most likely it will never fully recover. Always best to keep the batteries in the TOP half of their charge capacity.

 

Lenp

[mscans]

What converter do you have? Your mountain aire may have an old single stage unit and is not up to the task of properly charging your batteries, especially if you only charge for a few hours. Look at a 3-4 stage charger or adapter if you have the ability to add a charge wizard to your converter. The above poster is right, you may have a poor surface charge and need a better converter.

 

Once charged correctly it may take several days to properly charge your batteries the first time.

[oldjohnt]

If you have an old style "dumb" Converter/Charger they act more like a constant voltage source, maybe 13.4 to 13.6 volts, and DO NOT have any fast initial Bulk Charge stage, therefore it can take a longgggggggggg time to ever charge those house batteries and running the genset every few days for x amount of time will likely NOT keep battery charge levels up, SUBJECT TO LOADS AND YOUR CHARGER which I do not have so no warranty on my guesses.

 

In the event you have an old style charger, my recommendation would be to invest in a modern so called Smart Charger which has 3 or 4 automatic stages as it will charge the batteries faster and kick into the BULK high charge rate (around 14.4 or so volts) when you fire up the genset, as opposed to maybe 13.6 volts for an old style converter/charger. Perhaps some solar is another method to charge the batteries while dry camping??????????

 

An at rest stabilized voltage reading of around 12.6 to 12.7 is what id expect for a good battery that's charged, while 13.4 to 13.6 is what id expect if coupled to an old style charger when plugged into shore power or your genset is running. If its a smart charger Id expect an initial voltage of 14.2 to 14.4 until the charger backs off to maybe 13.6 or so Absorption then eventually 13.2 + for float.

 

NOTE again I don't know what you have for a charger now and your loads so I cant say for sure what the problem is.

 

John T

[Kirk W]

I'll not repeat what several have already suggested as my version would pretty much match what they have said. I do suggest that you may have an automotive battery charger that is multi-state as those are fairly common and if you do, and if we are guessing correctly about the converter in your RV, then I suggest that when charging from the generator set you would get better results with less time by using that rather than depending upon the converter.

 

If you have a reasonably good digital volt meter that displays to at least 2 decimal points, try lifting the negative cable from your batteries and then checking the voltage that way, but after they have been given at least an hour or two of rest. That should give you a voltage reading that will match pretty closely to the specific gravity.

[trailertraveler]

If you choose to try to use a stand alone automotive smart charger, I would disconnect the battery from the coach as the onboard converter/charger and stand alone charger may not play well together. For example the constant approximately 13 volts from the converter/charger may confuse the smart charger as to the state of charge of the battteries. With an older converter/charger, I would suggest trying to find out whether the converter will work properly without a battery to supply the 12v systems while the battery is disconnected.

[Fulltimer51]

http://www.rolls-battery.com/content/technical-downloads?q=node/51

 

See if this helps.

[LHS61]

I discovered I have 2 each 45 amp Iota chargers running in parallel. I just ordered the "IQ4" smart controller from Iota to make these units into 4 - stage chargers. That should help some. In addition, I will move to the other side of the property and hook to shore power for a week. I'm not sure these 2 month old batteries were 'broken in' properly. When I got them I hit the road and dry camped for about 5 days. That was followed by 6 days on shore power in a campground. I'm getting educated about these chargers by reading Bill Moeller's book and the good advice on this forum. Moeller recommends the Xantrex Battery monitor which tracks amp-hour usage... which I will be installing soon. He says to never discharge below 50% of the battery's capacity and preferably stay above 70%. He also claims that repeated discharging below 12.1 volts will shorten battery life.

 

I can't understand why Newmar doesn't install the $30 smart controller in the original build. Actually, the Mountain Aire is not an entry level coach.

 

Thanks for all your advice

 

PS - I just talked to the tech dept at Iota Engineering and they said the smart controller will make the chargers have a bulk charging voltage of 14.8 whereas the bare charger puts out 13.6 to start. Like I said, some experts do crazy things...

i.e. Why would anyone not want a 4 stage charger in their RV?

[oldjohnt]

Dave, that "Smart" Controller option sure sounds like a good choice. I certainly agree, why NOT use a quality 4 Stage (Bulk, Absorption, Float, Equalize) Charger, that's what both mine are. When you say you think the batteries were not "broken in properly" I take that as THEY WERE NEVER PROPERLY AND FULLY CHARGED but that Smart Charger should cure that..........

 

Bill Moeller's advice " He says to never discharge below 50% of the battery's capacity and preferably stay above 70%. He also claims that repeated discharging below 12.1 volts will shorten battery life." IS CORRECT IN MY OPINION and agrees with pretty well every article and every authors advice and opinion I've ran across out there including the fine gents here. A battery has only so many "Life Cycles" so the better its kept fully charged and never deep discharged, the less of those you are using up.

 

Are we havin fun yet, I am, will be heading West to 5 Natl Parks soon with lots of dry camping to exercise my Solar Panels and Battery Bank

 

John T

[lartross]

I went through 3 specific gravity meters before I got one that read my newish batteries as good when the resting

voltage was 12.6-12.7 [2-6v in series]. So, in my case my scottish/welsh frugality cost me time money and usnecessary

worry