Odd Electrical Trouble

[teachergal]

A few weeks ago I was dry camping in Acadia NP and had an interesting electrical issue...still not sure exactly what happened but we solved the problem and it hasn't happened since. I have a 2011 PW Plateau (Sprinter).

We started the day in Millinocket, ME and I switched off the propane and put the fridge on DC. (I'd been plugged into 15 amp service at the campground so it should have been charged, but the electrical service was iffy at best - my fridge was AC in the campground and it was NOT on auto so if the power had gone out it would have sounded the alarm and I would have fixed it.) We drove about 15 miles and stopped in a truck stop for what was going to be a quick stop but ended up taking 2+ hours. Fridge was running on DC. I then drove another 150 miles and stopped again for about an hour - left the fridge on DC.

When I arrived at the campground I switched the fridge to LP. I accidentally left the bathroom light on - it's not LED - while I was gone...about 4 hours. When I returned, and turned off the light, the battery was full. I used minimal electricity as I got ready for bed - a few LEDs and I ran the fan all night. I usually run the fan and usually after the 1st night dry camping the battery is down to 2/3. (I dry camp more than I'm plugged in).

In the morning I discovered that the battery was at 1/3. What? How'd that happen? I looked at everything and there wasn't anything that had gotten left on or anything. Since my propane detector will go off if the battery gets low I decided to run the generator to charge the battery. I ran the gen for about 15 minutes before I had to go. This is where it gets really weird....when I turned the gen off, the power went out to the entire coach. No lights. No water pump. Nothing. I tried running the gen again, but it cut out after about a minute.

Luckily my dad was there so he came over and we read the book and found the battery reset switch and pushed it and power was restored. We ran the generator for about an hour and left. When I returned that afternoon the battery was full. Again I used minimal electricity and the next morning the battery was on empty! I was heading out that day and didn't worry too much about it.

I drove 450 miles that day and was dry camping at Wal-Mart - when I arrived the battery was full. I ran the generator to heat dinner in the microwave - it didn't cause the battery to cut off. That night I was in the RV - LED lights burning all evening - and the next AM the battery was still full.

The only thing different was that at Wal-Mart I didn't run the fan (it was raining). Could it be the fan is dragging the battery down? My other theory was the fridge and running it on DC while I was driving and being stopped so long, but that doesn't really add up. I haven't had the coach that long, but in other settings I've run the fan at night and not had an issue with the battery - I can usually go 2 nights before I need to drive/run the generator.

After that I spent 2 nights at a KOA with 30amp and now she's back in storage so....

Just a random isolated incident or something bigger?

[markopolo]

Short answer: I wouldn’t worry about the fan etc. The monitor panel is off a bit. KiB’s allow for a 5% tolerance which is a lot. Full or C might be lit up at less than 12.7 volts. Your battery most likely didn’t recover from the long stop with the fridge on DC. You started both nights with the battery very low.

Longer answer:
If you have a KiB Monitor Panel (newer than 1992)
Full: C - CHARGE 12.7 volts
2/3: G - GOOD 11.9 volts
1/3: F - FAIR 11.2 volts
E: L - LOW 6.0 volts

I don’t know what fridge you have but some Norcolds will draw 15ah in DC mode.
If the first stop was close to three hours then your house battery (if you only have one) was pretty much fully discharged after that stop.

Then you probably drove for 3 hours which should have / could have brought the battery up to 90% charged. Then the next stop drew current at the 15ah rate again. Probably knocked it back down to 70% charged. Then there was probably some more driving (more charging) which may have been cancelled out by leaving the incandescent light on after you parked.

The panel should not have shown full at that point. (maybe the up to 5% tolerance coming into play here) I would have expected it to show G or Good which, at the lower end, is not good at all!

My guess is that you started the night with a battery at 70% capacity. The overnight fan might have taken another 15ah. At that point your battery would be below G or less than 11.9 volts which is basically discharged. The battery disconnect probably tripped from the high current initially drawn by the almost dead battery.

After one hour of generator run time I would have expected to see G again when you returned later that day. G is a voltage over 11.9v. My guess here is that your battery might have been at 70% state of charge (12.32 volts). You probably started the second night with the battery in a similar state to the first night.

Basically, with a KiB panel, a reading below G would mean recharge immediately to me. From the PW brochure, I think your van has a PD converter with a charge wizard. I’d keep it plugged in at home all the time. It will go into float mode when the battery gets fully charged. (make sure you have the Progressive Dynamics converter with Charge Wizard)

--------------------------------------------------------------------------------------------------------------------

Compare the following battery state-of-charge chart with the KiB panel approximate voltages.


source: http://www.windsun.com/Batteries/Battery_FAQ.htm

KiB Monitor Panel (newer than 1992)
source: http://www.kibenterprises.com/troubleshoot/k_panel.pdf
Full: C - CHARGE 12.7 volts
2/3: G - GOOD 11.9 volts
1/3: F - FAIR 11.2 volts
E: L - LOW 6.0 volts

[teachergal]

That makes total sense!!!!

So what I shoulda done was realize I'd left the fridge on battery longer than it should been and ran the generator when I got to the campground!

Would it have solved the battery disconnect issue if I'd started the engine and let it idle and then started the generator? (the chasiss battery does charge the house battery) Or would it have been better to let the generator run longer (in that setting I couldn't because I needed to go, but in a different setting I could have ran it longer).

Thanks so much for your help solving this mystery!

Unfortunately I can't keep the van at home - I keep it at a boat/RV storage place and there are no plugs so I disconnect the house battery when I leave it. So far I haven't disconnected the chassis battery when I've left it but I haven't had it in storage for more than about 4 weeks, if next winter is as mild as this winter I won't leave it then either!

[markopolo]

I should mention that I assumed that you have a single house battery with a 100 ah capacity. So you can see the impact a 15 amp hour load for three hours would have. 1/2 the capacity could be gone. True deep cycle batteries can be discharged 80% but many people recommend to not discharge your batteries below 50%. I mentioned keeping the van plugged in because it can take a few days to fully charge a battery.

The battery use and maintenance you describe is in common with many other RV'ers. You're doing the best you can.

Trying to charge deeply discharged battery by running the van motor can cause a temporary problem also. Most RV systems will have a circuit breaker of some sort on the wiring from the van isolator to the house battery. That breaker will trip if overloaded. Usually they are self-resetting after they cool down. But, while the breaker is in its tripped state, the house battery won't be charging.

Plugging in would be my first choice for recharging a deeply discharged battery. That will let the converter/charger do its job. Second choice for me would be a generator. Again, that lets the converter/charger do its job.

[markopolo]

You could make a playing card sized laminated cardboard sign with "Fridge on battery" written on it and clip it on to your van key ring whenever the fridge is on battery. I've started putting a sign like that on my steering wheel whenever my van is plugged in. Mine says "van plugged in". I started doing that after I almost drove off with the van plugged in one day! Might sound like a silly idea. To this day I can't believe I could've driven off while still plugged in - it's such a basic thing. My co-pilot saved that day.

[Rick]

I have had a similar problem last week with my PW Sprinter. We were dry camping with the fridge on LP. We watched TV for maybe an hour. Ran the fan a little, but not all night. Battery did not last long. Does the fridge draw much off the battery when on LP? I ran the engine fro about 15 minutes each day and it would bring the battery up but by the next morning it would be 1/3 or less.

The chart on battery level is handy.

[Mike]

The fridge shouldn't use any electricity when it's running on propane.
The TV and fan, and any hard wired detectors like propane and CO will pull down your battery.
And there might be a vampire draw somewhere. In my 2002 Roadtrek, there are 2 courtesy lights
that run off the coach batteries. It's possible to accidentally leave one on, after the rear doors close
and not be able to see it, because it's located under the bed in that storage area. The other one is
in the external storage locker, driver's side. It can only be on or off, it doesn't come on when the
the external storage door is opened, like the one under the bed.

Have you had the battery tested, with a meter, or are you reading charge level on your monitor panel?
Running the engine for 15 minutes shouldn't recharge a battery which was run down to discharged.
I have 2 coach batteries rated at around 100 ah each and I'd have to drive it for at least a couple of
hours to fully recharge them from 50% discharged. You may be seeing a "surface charge" which can
give a false reading when tested too soon after running the motor.
Here's a short read. See section 3, which describes how to test a battery, and explains "surface charge".
http://marine-electronics.net/techartic ... /b_faq.htm

[Rick]

Thanks for the info Mike, I think you are right about surface charge, it would show that it was charged up from 1/3 but shortly after running something it was back down. They tested the battery at the Benz dealer and said the battery is good. My old coach had 2 batteries and the lasted well. If I get a generator how long do you have to run it to bring the battery back to full charge frm 50%?

About the fridge, it is 6 cu.ft , when it was running on the hot days it was making a noise like a fan running. Was that because it was so hot?

[arrveedogz]

The RoadTrek Adventurous manual says "if the aux batts are not being used, they should be recharged monthly by connecting to an outside electrical power source such as connecting to shore power or by operating the generator, for at least 12 hours or by running your vehicle's engine for a minimum of 2 hours." -- my emphasis

I don't know where these people keep their rigs, but running the generator for 12 hours isn't going to fly.

During off season, I've been running the engine and generator (under load, ie with the AC turned on) for a short period (certainly not two hours) each month. Sounds like that may not be accomplishing much electrically, although I've only had one battery problem in 3 years - and that was due to a bad set of batts that wouldn't hold charge at all.

Sounds like it would be better to plug it in (with main batt switch on) for a 12 hour period.

[Rick]

Thanks for the information. I will have to see how long it last next time I am out. I know my fridge does take power to heat the strip between the two doors to prevent condensation according to the fridge book.

[Mike]

Originally Posted by Rick

Thanks for the info Mike, I think you are right about surface charge, it would show that it was charged up from 1/3 but shortly after running something it was back down. They tested the battery at the Benz dealer and said the battery is good. My old coach had 2 batteries and the lasted well. If I get a generator how long do you have to run it to bring the battery back to full charge frm 50%?

About the fridge, it is 6 cu.ft , when it was running on the hot days it was making a noise like a fan running. Was that because it was so hot?

Sorry, have been busy last few days packing and stressing.
My manual suggests similar run times to arrveedogz's manual.
I would agree with him that the generator may not be the best choice as a battery charging source.
Plugging in is probably best, but if you drive/tour in your B like I do, 2 hours charge time off the
vehicle alternator/converter charger is easily achieved. I've only ever really beaten up my 2
batteries once when I left the fridge on DC for a while longer than I should have, after we stopped, instead of switching to propane right away, or just switching it off. My bad, but we only use it to chill stuff while we're between stops. Like bottled water.
As far as the fan noise, possibly. It has been hot lately, including up here in Canada. Even some of
our permafrost snow turned slushy.

[markopolo]

I think 1 to 2 hours of generator time should get 1 battery back to 90%. It depends on the converter/charger output and the rate at which the battery will absorb the charge.

To minimize generator run time but still maximize charging you need a meter that shows you the amps flowing to the battery. A clamp on ammeter ( link: http://www.classbforum.com/phpBB2/vi...hp?f=29&t=1038 ) would give that information. When the amps show zero turn off the generator. No need to keep running it. You might just need to monitor it once or twice for baseline data. Also, this post http://www.classbforum.com/phpBB2/vi...hp?f=12&t=2257 might interest you if you are technically inclined.

I had forgotten about that heat strip between the fridge and freezer doors on two door fridges. I had that in a B+ and a full Class C but not in a Class B. I always kept it off - the Dometic fridge had a switch for it.

These larger RV fridges going into Class B's do have DC current draws to be aware of. Here are the DC draws for a 8 cu ft Norcold. I don't know if any of the new Class B vans have 8 cu ft fridges or not but it gives a good idea of the loads.

[Mike]

Originally Posted by markopolo

I think 1 to 2 hours of generator time should get 1 battery back to 90%. It depends on the converter/charger output and the rate at which the battery will absorb the charge.

Depends on how depleted the batteries are when you start the generator, too, wouldn't it? Agree
about the charger output and even the type of charger (smart charger versus "dinosaur" dumb
charger like I've got) might shorten the recharge time because it will try to maximize the rate.
Or maybe not.

[markopolo]

Yes. With the two batteries in your Roadtrek bringing them back to from 50% discharge would need 100 amp hours or so. Probably more like 3 or 4 hours. Getting the batteries back to 90% on a generator is a practical goal.

Voltage matters also: http://www.progressivedyn.com/battery_basics.html

One disadvantage of recharging a lead acid battery at a fixed voltage of 13.6-volts is the recharge time is very long. A typical 125-AH RV or Marine battery will take approximately 80 hours to recharge at 13.6 volts. Increasing the charge voltage to 14.4-volts will reduce battery recharge time for a 125-AH battery to 3-4 hours. Once a battery reaches 90% of full charge, the voltage must be reduced from 14.4-volts to 13.6-volts to reduce gassing and water loss.

[Mike]

If I recharge my batteries with the generator, it's purely accidental, while I'm running the generator to do something else, like run the A/C or power my power drill or the air compressor. Luckily, we move around so much our batteries are almost always ready for use. As you said, the charger output is probably the biggest determining factor in recharging times. I think I'm going to do some experimentation next time we're on the road, to see how the genny does as a battery replenisher. If the fridge is on DC, and I fire up the generator while we go out for a while, it should reduce the depletion rate on the batteries. Our fridge just kills the batteries on DC.
Phred has an amazing write up on it all, if you have an afternoon to read it all....(I know you've probably already read it). Wish I understood it better.
http://www.phrannie.org/battery.html

[Rick]

Wow, a lot of great information. The chart Markopolo posted is interesting. My firdge is 6 cu. not 8 but I would assume some of the draws would be similar like divder heater. Not sure what a flapper heater is. I am assuming that the heater and perhaps the fans may run even on LP and that is why battery (only have one) depleted quickly. It was very hot the week I was out, it was in the great white north in Ontario Canada. Mike was right it has been very hot here. We were along the St. lawerence near Kingston.

[markopolo]

Over 24 hours that divider heater would draw 16.8 amps. (24x0.7=16. add the fans etc. and it is definitely something to be aware of and plan for. Hopefully, it can be turned off.

[Rick]

That is a lot. How many amp hours in a typical deep cycle battery? Thanks for all the information it si very helpful

[markopolo]

I use 100 amp hours as typical single deep cycle capacity rating. As an average, it might be a bit on the high side. 80ah to 120ah is the range of ratings I've seen.
So, with a 100ah capacity and only discharging 50% before recharging leaves only approx 50ah to use.

[Rick]

Thanks again, you have been a great help