Inverter/battery life -- what is normal?

[rv rick]

Our 2008 Tour with a 2000w inverter seems to have very poor battery life when dry camping. When showing a 50watt draw on the inverter, and no lights on (but other parasitic items still running), fridge on propane, we drop from a full charge to about 12.1 - 12.2 volts in just a couple hours. We have 3 group 31 batteries (factory issue) for the house side. I asked the dealer to test these since I knew the coach sat for a few months before I bought it, but was told they were good.

My 2004 Meridian with 3 group 27 batteries and the same inverter seemed to last much longer. I suspect I need new batteries, but would appreciate hearing from the experts out there.

Thanks!

[rv rick]

Our 2008 Tour with a 2000w inverter seems to have very poor battery life when dry camping. When showing a 50watt draw on the inverter, and no lights on (but other parasitic items still running), fridge on propane, we drop from a full charge to about 12.1 - 12.2 volts in just a couple hours. We have 3 group 31 batteries (factory issue) for the house side. I asked the dealer to test these since I knew the coach sat for a few months before I bought it, but was told they were good.

My 2004 Meridian with 3 group 27 batteries and the same inverter seemed to last much longer. I suspect I need new batteries, but would appreciate hearing from the experts out there.

Thanks!

[AFChap]

I would try equalizing the batteries first. The first time we boondocked I was surprised at how quick our batteries ran down. After equalizing, there was a huge difference in capacity. Your inverter should have an equalize feature. Mine takes 8 hrs to run the full equalizing cycle.

[Mr_Bill]

Where would I look to find the equalizing feature to activate it? I have the same type of problem.

[rv rick]

I looked through my Dimensions Inverter/charger materials and could not find anything on equalizing. The only thing I found was on battery conditioning, which is an automatic function that occurs every 10th charge which means this has already been done on my rig several times.

UPDATE: My batteries lasted about 14 hours ((before dropping to 11.6v) while we ran at 50 to 75 watts plus usual items such as occasional water pump. We were not in the coach for 4 hours of this time and everything possible was off. Fridge is on propane. This seems like a short run time to me.

[AFChap]

I have a Freedom Inverter/Charger. My manuals mentioned equalizing, but I had to call a tech via Coachnet to find out how to start it. I don't know what you have or how it would work on your coach if you have an equalizing feature, but I have a checklist on equalizing on my website at http://www.pjrider.com/RVChecklists.htm.

Rick -- I wonder is your "battery conditioning" is some form of equalizing? If you have a 4-door Norcold refrigerator, I believe that even running on LP it is using 12v to run some fans. We've never attempted to go on just battery power for longer than just overnight, often running a ceiling vent fan on low.

[BryanL]

I would not worry about 'equalizing' when it comes to small RV banks like this - just make sure all three are fully and properly charged. Use a proper maintenance charger on them when not in use for more than a few days like the Battery Minder or the WFCO or ChargeWizard inverters.

As for a draw of 4 or 5 amps over a few hours pulling voltage: that's maybe 25 AH out of a capacity of 300 or more. That's hardly enough to take off the surface charge.

As for the difference between the new batteries and the old set, I can think of two possibilities. One is that the new set is bad and the other is that the new set has a bit higher internal resistance than the old - given everything else about the same.

When measuring voltage, it is a good idea to let them sit for a half hour or more with little or no load on them before you determine voltage.

Also take note when you have the load applied whether the voltage continues to drop (bad) or whether it just drops to something like 12.1v and pretty much stays there (OK). If you measure voltage at the load end you might have a lower reading due to wiring resistance.

If the batteries are OEM, I'd be suspicious of them. These often suffer from sitting around a sales lot in hot conditions without proper attention and that can age them prematurely.

[John_Canfield]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rv rick:
Our 2008 Tour with a 2000w inverter seems to have very poor battery life when dry camping. When showing a 50watt draw on the inverter, and no lights on (but other parasitic items still running), fridge on propane, we drop from a full charge to about 12.1 - 12.2 volts in just a couple hours. We have 3 group 31 batteries (factory issue) for the house side. I asked the dealer to test these since I knew the coach sat for a few months before I bought it, but was told they were good.

My 2004 Meridian with 3 group 27 batteries and the same inverter seemed to last much longer. I suspect I need new batteries, but would appreciate hearing from the experts out there.

Thanks! </div></BLOCKQUOTE>If you have flooded cell batteries (wet), measure your specific gravity with a hydrometer during discharge to determine your battery state. Trying to use a voltmeter while you are discharging the batteries to determine the charge state is extremely difficult. Only the hydrometer will provide the accurate charge status during battery discharge.

Using a voltmeter to determine battery charge must be done with the battery at rest for 24 hours - not easy to do.

You might actually be okay with your battery capacity.

After some period of time, sulfates (if I remember my battery chemistry correctly) will flake off the lead plates and accumulate on the bottom of the battery box. If they accumulate to a great enough depth, they will contact multiple plates and cause shorting of cells. Conditioning or equalizing (same term) will force a higher voltage than usual into the battery causing (hopefully) the sulfates to recombine in the acid solution.