Batteries - power for ? long

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albertaangler

albertaangler

Active member
Joined
Jan 16, 2010
Posts
31
Location
Banff Alberta
OK Here's our issue.
We have  22 foot TT, 2 grp 27 batteries. We dry camp in semi wilderness areas
At home these batteries will take a tad over 13v,on generator and TT charger only 12.7ish
I have taken every power consumer out of the system (switch for radio), disconnect co2 detector.
Even without the furnace running, lights for as little as an hour, and fridge off we still awake to as 1/3 battery.
We are so paranoid of losing power we use a lantern in the evenings for cards etc and only use lights when gennie is running for a short time to read in bed.
So, what are possible causes of the power drain? How important is that batteries match exactly in CCA and age? One of mine is 600 one 625 CCA, one a year old one two years old. Both were on desulfating cycles over the winter and summer with a CTEK 7002 charger.

Ideas???????

 
You're only looking at half the equation.  You have to measure both voltage and current going into the battery to determine if it's charging.

Get an automobile ammeter (the 50-0-50 type) and put it in line with one of the battery leads.  See how much current is flowing in when you charge it, from that you can determine how much of a charge it's taking.  The battery will continue to charge (drawing current from the charger) even after the charging voltage rises to 12.7 or 13 volts.

I suspect you aren't running the generator long enough to to fully recharge the battery.  If the battery isn't at a full charge there's less you can draw out of it before it's discharged.

Two Group 27 batteries hold about 100 amp-hours each when fully charged.  An amp-hour is 1 ampere of current for one hour.  Figure on being able to use about half of this in normal usage.  In other words, two fully charged Group 27 batteries should last about 40 hours running a 2.5 amp light bulb, or 15 hours running a 6 amp furnace blower.  Or any other combination that totals 100 amp-hours.
 
Lou: Thanks.
I have certainly never gotten anywhere near 40 hours us using anything either with this trailer or our older camper.
Our last trip went likw this.
So, start with fully charged batteries from home. Drive 4 hours, set up, and with only fridge and co2 running by next evening we are low on power. Run gen for 3 hours.
Next day less than 11v. Run gen 5 hours, next evening low again.
Disconnect co2 and turn off fridge. Start evening with 12.7v wake up to 11.8 with nothing running.
We then kept fridge on, ran gen at least 3 to 4 hours a day. Lucky we have good sleep bag as there were a few nights nearing 0oC and would have loved to trust my power to keep furnace going, but didn't.
Same basic scenario daily for two weeks.

I'm on the way to dealer on Tuesday to repair a faulty water pump (that's another issue.........)
Is there something they can check on the TT circuits? I suspect no grounds faults or I'd be dead all the time.
Tks
Don
 
12.7 is not charging voltage. A fully charged 12v battery should read at least 12.6 and normally will show more like 13.3-13.6 (excess surface charge form the charger). So it would seem you have a problem with the RV's onboard charging system (or are you trying to charge direct from the generator via 12v output?)?

What condition are these two Grp 27 batteries in? They should have about 105 amp-hours each or 210 total and that is plenty to run your lights and equipment for a couple days, assuming little or no furnace use (the furnace fan is a hog!).

How are you measuring 1/3 battery? Voltage?    33% charge would be about 11.85v with the battery at rest (no load).
 
we spent 5 days in yellowstone last summer dry camping and still had lights/pump.  Did not use furnace.  we have 2 batteries also.  I cleaned the battery connections  and posts before we left.  I also have a cheap load tester I use with the batteries fully charged, and mine checked out ok.  bob
 
You said, "At home these batteries will take a tad over 13v,on generator and TT charger only 12.7ish". Are you using a different charger at home? As I think Gary said, 12.7 isn't charging voltage. It should be at least 13.5 or so. You may have a charger problem on the TT.

You also said, "How important is that batteries match exactly in CCA and age? One of mine is 600 one 625 CCA, one a year old one two years old." Are these deep cycle batteries? CCA is cold cranking amperage. They are designed for very high amperage for a very short time. If they are regular group 27 starting batteries you should get some true deep cycle batteries like golf cart batteries. You want a high amp hours rating.
 
albertaangler said:
Both are 'deep cycle' one labelled 'rv' one 'marine'
I'll get the notebook I used tomorrow en-route to dealer.
Click to expand...

It is odds on that the one labelled "marine" is a dual purpose unit with some cranking power (many thin plates)  gained at the expense of deep cycling (fewer thick plates). 

You should be buying true "rv" deep cycle batteries and in pairs so that both batteries are identical both in electrical properties and in age.   
 
I had a similar problem with our brand new Cougar. Both batteries would appear to be fully charged (12.65 to 12.7 volts) after a day of towing, but then would be down around 12 volts the next morning. We were only using the refrigerator and the water pump. Turned out to be one battery had a "dead cell" and the other battery "wasn't much better" according to the dealer. Dealer replaced both batteries under warranty and problem went away.
 
The fact that they were at 12.6-12.7 is a dead giveaway. A freshly charged battery in good condition will show a surface charge of 13.3-13.7 volts rather than 12.6. This over-voltage is a normal artifact of the charging.  A battery with a weak cell will prevent it from achieving a full charge, so the over voltage effect  is lower, e.g. something under 13 volts.
 
Like Gary is saying...

Mine when the AC power is available I see 14.5 to 14.7 on the charger max voltage then after it bulks up and settles to storage mode it settle down to about 13.2 to 13.5. Now if I unplug the AC power (pull the main fuse) the batteries will come to rest at about 12.8 after about hour or so. Then it hold this value for many days.

As for boondocking i can get about 1-2 days from the batteries without charging it all depends on what we are using for power.

As for another test I pulled in early spring. I fired up just the fridge with no AC. It ran a total of 14 days and the batteries where just starting to drop below 11.6 Volts.

So I know the lighting and water pump and other pluging in accessories are the big consumer of power...
 
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