Batteries Not Charging

Ted,

Outstanding that you found the problem!! A simple no-cost solution, too.

I have a couple of meters mounted right on the cab's dash that will show me when this is happening while driving down the road or camped.

Problem solved
It was suggested here that my negative cable from the battery to my MH frame may be corroded
Sure was,just removed bolt ,wire brushed everything & now everything works as designed
Greatly appeciate everyone for your suggestions & help
Thanks Again
Ted

Great Site
Thanks everyone
Plan on checking corrosion both at solenoid & connection of negative cable to frame
I suspect & hope its one of the above
Take Care
Ted

I have a 2004 Tioga 26Q, may have a bad rocker type auxiliary battery switch in the monitor panel or solenoid. I think that the solenoid is buried under wiring in left side of battery box. Suspect that it is stuck or not getting high enough voltage to actuate. When I cycle the switch, I don't hear the usual clunk. I'm going to disconnect the battery and check resistance at solenoid as suggested above. Will check all connections for corrosion, etc.

Yes, corrosion anywhere along the input path (from the converter) could cause what you're seeing. A point of corrosion in that 5 foot input path all the way from the converter's terminals to the lug on the input side of the solenoid could be the cause. If so, it's a corrosion point outside of the solenoid, so a new solenoid is not required.

Also - it may not be corrosion in the 5 foot positive input path between the converter and the battery(ies) ... it very likely could be corrosion in the negative battery path ... maybe where the negative cable from the battery(ies) connects to the frame of the RV.

Hi Phil
I feel selenoid may be my problem as you suggested
Even though I get the same reading on both sides of selenoid would corrosion on incoming side reduce my reading to in this case 12.2 V & therefore this same reading would appear on other side????
Thanks
Ted

Hi Phil
I really appreciate your comments & will check my selenoid contacts this morning
I did put a voltmeter on both sides of the selenoid & got the same reading on both sides:12.2 I understand from others if the reading on both sides is the same then devise is good I understand reading at selenoid should be same as converter output which is 13.7 Don't know where I'm losing the 1.5 difference????
Only 5 feet between converter & battery selenoid
Plan on crawling under MH to try & locate cable to see if damaged in any way
Does the engine power boast switch come into play here???
Not to smart when to comes to electricty but if conact on selenoid appear corroded if I turn off or disconnect all power sources including chassis battery can I safely work on selenoid????
Thanks
Ted

Ted,

Your problem seems related to one I'v had twice in over ten years of owning our Class C motorhome.

Your coach batteries are connected to your coach's 12 volt system with a solenoid (eletrically activated switch). These solenoids can develop a frustrating failure mode in which they are opening and closing all right whenever you operate the coach battery on/off switch on the wall (mine is by the coach entrance stairwell) ... such that the contacts of the solenoid have too much resistance between them when they're closed. What this can do is cause 13.7-13.8 volts to be read on the side of the solenoid coming from the convert and something less to be read on the other side that's connected to the coach batteries -> whatever voltage the coach batteries are resting at. The coach batteries can be kept charged partially by the converter but not all the way and whenever you check, on one side of the solenoid shows full converter voltage but on the other side you see the lower battery voltage.

In my two solenoid failures in the past, it was the other solenoid that connects the coach batteries to the engine alternator whenever the starting key was ON (the engine running). The alternator would be delivering, say, 14.2 volts to the engine battery but the coach batteries would show less voltage on them - say 12.7 volts .... as if the alternator voltage wasn't getting applied to the coach battery terminals through the solenoid contacts. What was wrong was corroded solenoid contacts such that they would still convey current, but through too much resistance due to the corrosion on the solenoid contact surfaces. The solution was a new solenoid - which I had to install two different times over the years. A good solenoid is supposed to have zero resistance across it's contacts .... a solenoid with aged contacts will have a resistance reading (in ohms) across it's contacts. Your batteries can still supply power or be charged through the solenoid's corroded contacts, but not very well.

Maybe I've misread something about your problem - but be warned - 12 volt battery system solenoids are not always doing just the simple function they're supposed to be doing.

Thanks Drew
Ted

I suspect your converter is a WFCO converter, rather than a WAFO. If you want to throw money at it, there are better converters available, but I haven't seen anything you've written that suggests it's not working properly nor adequate for typical uses.

Wiring loss of 1.5V is not normal. If you have 13.7V at the converter output but only 12.2V at the batteries at the same time, there is a poor (high-resistance) or open connection between the two somewhere. The two places should be at about the same voltage, certainly within a few tenths of a volt.

The experiment with running the engine for awhile to charge the batteries shows that they were indeed being charged from the alternator. 20 minutes is not enough time to charge them fully, or even close to fully, if they're anything more than slightly discharged, so there's not much to guess at their condition based on that. I don't think they were behaving as though there was a shorted cell or other similar problem that would make them completely useless, but they may well be not in great shape still. Regardless, even if they are worn, that is not your only problem.

I would trace the wiring between the converter and the battery and measure voltages to find where the voltage drop is happening, and fix whatever is wrong when found. It's not always a the easiest task as the wires are rarely easily accessible, but I don't know of a better way to find the problem. It's almost certainly at some connection between parts or wires, rather than in the middle of a wire, unless possibly there's some obvious damage to a wire.