House battery power cuts off

[jrcwen]

On a recent trip in my 2006 View, after dry camping with solar panels for 5 days, the 12V house batteries would cut out when an additional load was applied (turning on lights, using water pump). Power could be restored by pushing the battery cut-off switch to on. The battery indicator indicated "full" and the battery voltage was 11.9-12 volts (measured at battery with voltmeter). After plugging into 110V for several hours and recharging the batteries, this never happened again. A year ago, while dry camping, I had run the batteries down to the point that the generator would not start and never had this disconnect type of problem. Does this indicate a problem with the battery mode solenoid or battery disconnect switch? Thanks for any help.

[MrTransistor]

Hi jrcwen,

11.9 to 12 Volts is an essentially dead battery. Normal charged voltage will be 12.8 Volts or above. You say solar panels, did you install extras? If you are referring to the one that Winnebago installs from the factory, it is only a 10 Watt unit. i.e. less that one Amp. at 12 Volts and that is not enough to supply you while dry camping.

The additional load, depending on what circuit it was on, would drop the voltage to the solenoid. I am not aware of a low voltage drop out circuit in these contactors but there could be.

Run the generator for a couple of hours when the batteries get down to 12.5 Volts or install a couple of 165 Watt solar panels on the roof if you plan to do extended dry camping.

Note: All voltages stated are temperature dependent. Lower in the summer, higher in the winter. (by a couple of 1/10ths) See battery owner’s manual for temperature correction factors (i.e. plus or minus mVolts / degree C) and state of charge voltages for your particular batteries.

[hamguy]

Quote:

Originally Posted by MrTransistor Hi jrcwen, 11.9 to 12 Volts is an essentially dead battery. Normal charged voltage will be 12.8 Volts or above. You say solar panels, did you install extras? If you are referring to the one that Winnebago installs from the factory, it is only a 10 Watt unit. i.e. less that one Amp. at 12 Volts and that is not enough to supply you while dry camping. The additional load, depending on what circuit it was on, would drop the voltage to the solenoid. I am not aware of a low voltage drop out circuit in these contactors but there could be. Run the generator for a couple of hours when the batteries get down to 12.5 Volts or install a couple of 165 Watt solar panels on the roof if you plan to do extended dry camping. Note: All voltages stated are temperature dependent. Lower in the summer, higher in the winter. (by a couple of 1/10ths) See battery owner’s manual for temperature correction factors (i.e. plus or minus mVolts / degree C) and state of charge voltages for your particular batteries.

I'm sorry, Mr. T but I must take exception with your statement that "Normal charged voltage will be 12.8 Volts or above.".

Lead acid cells have a nominal charged voltage of 2.1VDC +/- .02 or so. (laws of physics/chemistry). That makes a 12 VDC 6-wet cell battery have a fully charged (and not residual charge) of 12.6 VDC.

Now in order to charge a battery, a voltage of > than 12.6 volts must be impressed on the terminals in order to force current into the battery. Normally you opt for an initial charge current of about 0.1 to 0.15 C, C being the capacity of the battery. This is not very critical but you don't want to charge at 1.0 C for sure.

In any event, most RV Converters are 3-stage smart chargers. They initially put out a voltage of 14.2+ to rapidly boost the charge status. They then back off to a forcing voltage of 13.6 volts to complete the charge. After this, they drop to a sustaining voltage of 13.2 VDC.

Immediately after reaching the sustaining you can turn the charger off and at that time, you will read up to 12.8+ volts That is the residual charge voltage. BUT, that is NOT the battery voltage. If you place a 2-3 Amp load on the battery, it will drop down to ~12.6VDC .

See - http://tinyurl.com/knbm76for a good explanation. And see -
http://www.ccis.com/home/mnemeth/12volt/12volt.htm for a superb technical treatise on RV 12V systems and the care and feeding thereof.

[jrcwen]

Thanks for both of your replies--the question is whether this is normal behavior for the battery disconnect relay to shut down power when the voltage drops. I called Winnebago Service Advisor who said that this is not normal, and that confirms my prior experience when the batteries ran low that this did not trip. I think, unless I hear differently from someone with experience, that I will replace the battery disconnect solenoid/relay. Any comments/thoughts would be appreciated. Thanks, Jim

[Luv2go]

I just looked at the wiring diagram for a 2006 View (picked the first model as I did not know your exact model), the battery disconnect relay should definitely not be cutting off because of low voltage.

This type of relay does not need any voltage to hold it in either the on or off position. The relay connects to a yellow wire coming from the batteries to wire KKF which goes to a buss bar with the Coach Panel 40A breaker as well as a Battery mode switch breaker (6A).

Here's the link for the assembly diagram that I found most useful:

http://www.winnebagoind.com/diagram/...ire_152714.pdf

The Battery disconnect relay is in the lower-right corner of the diagram, Winnebago P/N 86273-01-000 which probably crosses to an Intellitec battery disconnect relay (they are pretty much the industry standard).

Here's a link to the relevant page:

http://www.intellitec.com/PDF/5300066.100.pdf

By the way, Winnebago has an excellent set of resources for your coach (and any coach they have made, as near as I can tell) including wiring, plumbing, assembly diagrams, etc. I wish other manufacturers (Newmar included) would publish such good documentation, it would be a lot less frustrating to work on the coach. I have requested such documentation for our coach twice and each time received a CD with sparse documentation for other models, not mine.

Good luck!
Stewart

[MrTransistor]

Hi Jim,

I concur, I would just replace the contactor. If for some reason, the control switch was pressed for an extended period of time, the contactor may have overheated which would cause it to drop out sooner under low voltage conditions. Me? I would take the old one apart just to see if it 'had' overheated. This is a similar condition to what happens to the tie contactors, overheating.



Hi hamguy,

I applaud you, I couldn’t master the code, wife says I have no ear for music. I did room with a ditty-bop when I went through Radar Sets training at Keesler though. I was trying to keep this simple since most people don’t have a First Class with Radar Endorsement, 40+ years in electronics, Net+ certification, and electronics instructor experience as a background. As you can see from the second article you reference as well as the one listed below, lead acid battery technology is quite variable.

Since the meters in the coaches are only 2 and a half digit displays, they tend to read 'most' RV batteries “in the spring and fall” at a rest voltage of 12.8 Volts. The reason that the voltage is just a tad higher is because instead of pure lead and pure lead dioxide as was used over 50 years ago, modern lead acid batteries use an alloy of lead and antimony or calcium to improve the mechanical properties of the lead. This changes the chemical reaction very slightly which increases the at rest voltage per cell to just around 2.13 volts per cell ‘properly aged*, 20° C, at rest, no surface charge, 100% charge, and no loads” (tough to do). The math puts the output at 12.78 Volts which on a meter with only one decimal place should read 12.8 Volts. As I said in the original answer to Jim:

Note: All voltages stated are temperature dependent. Lower in the summer, higher in the winter (by a couple of 1/10ths) See battery owner’s manual for temperature correction factors (i.e. plus or minus mVolts / degree C) and state of charge voltages for your particular batteries.

Lead acid battery technology is a career field in itself. The problem with any advice we give on this forum is in the details or ‘not knowing the details’. Battery brand, type, age, temperature, cycle experience, leakage characteristics, charger type, etc. all have an effect on the specific voltages that are read from any given battery’s condition at the time it is checked. The manufacturers themselves are pretty vague with their numbers for the same reasons, but they try to give us something that the layperson can use if not quite understand. So, I recommend that everyone take the advice above and go to the battery manufacturers site first. They usually have very helpful information even if they don’t get down to the mVolt precision.

http://en.wikipedia.org/wiki/Lead-acid_battery

* New batteries must be initially aged by cycling to realize their full Amp./hour potential. You don’t, of course, have to do this. The difference between new and conditioned is probably less than 5%.