Powering down inverters

[Jeff Bayley]

After using this bus for almost 2.5 years I just discovered something that I suspected for a while. When I use the 12 Volt shut off switch going to the inverters (mine is in the battery bays) nothing was happening. No effect on anything shutting down inside the bus. What the heck was that switch for ? Well, when I just put new house batteries, turns out that at some point someone put the main possitive to the post on the coach at a point nearby the correct post but doing directley to the inverters. Completley bypassed the main shut down switch. If I had something smoking down there there would have been no way to shut power off to it besides getting the main post off the battery bank. I went by Monaco about 2 weeks ago in Elkhart. They don't make Royals anymore but there are a a couple of techs around that know there way around these conversions. I showed them this and asked if there was any reason why someone would have bypassed this shut down switch and done this besides in error.

There is something called a "shunt" that is rated at 200amps that (if I put the main possitive back on the correct post) all the power will be going through on it's way to the main shut down switch. Well, the inverters have in line fuses between the battery bank and themselves that are rated at 350 amps each. Everyone seems to agree that that "shunt" could and should be replaced with a 500 amp (which still doesn't add up to 350 x 2) but that is the recommendation. A monaco tech even produced a wiring diagram that showed it called for a 500amp. Maybe someone kept blowing the 200amps and bypassed it temp and never put it back correct. ??

Any comments on this appreciated. That means these inverters have been "On" for 2.5 years and I have never shut the coach completley down. Since I've been full timing in it until recentley no big uneeded wear and tear I suppose.

I also talked to a very knowledeable guy at a Xantrex dealer (new name for Trace) and he said the units in this bus are the same units that people use to run their entire house on solar, wind, etc, etc when they go off the grid. I found that interesting and surprising.

[Jon Wehrenberg]

We learned at POG III that we need to be aware of potential safety issues with our coaches. One of the items stressed was the need for a circuit breaker or fuse within 72" of a power source.

On our original Liberty the house batteries were in the rear above the bus batteries. The top four were on a slide out tray to make servicing easier.

The heavy cables had slack so the battery tray could be extended. They were about 48" long and went from the last battery post to the house shut off switches and the house circuit breakers. They complied with the 72" rule we were taught. However, when the batteries were in their normal position that cable slack was at the rear, out of sight and as we found out they had the potential to swing and hit a hot engine, which is exactly what happened on a trip.

The cables hit the hot exhaust manifold, and since the point of contact was between the battery post and the circuit breaker we had a dead short on an unprotected part of the circuit. I can tell you for sure the power from six batteries will burn whatever cable insulation is there in seconds, and once the insulation is gone things get really hot at those cables and anything around them.

I ended up reaching in next to a hot engine with wire cutters and just started cutting cables until the sparking stopped and the potential fire hazard was eliminated.

My point is that I had the coach about 12 years at the time, serviced it regularly, looked at it often to try to see potential problems and this one got away from me. Other than having to replace 100% of the house battery cables and losing a couple of batteries my coach was OK. But the lesson I learned was to really look at things on my coach to try to catch potential problems before they become real problems.

This may sound scary but our coaches have a lot of places for potential problems and as Jeff points out we really have to take a hard look at the coach to try to find them. Since Jeff was turning off his switch it is possible he could have been electrocuted because he would have been thinking he had turned off his inverters.

[Jeff Bayley]

Does anyone have any tips for saving more power ? I just replaced my Intersate Deep Cycle batteries for the 2nd time. Free under their 1 year relacement warranty but takes a couple of hours for the job. I've got 8 count of 4d's. I think Harry and a few others said they have better luck with the 6 Volgt golf cart batteries put together in series and I'm ready to try that next.

I go to bed with a full charge on the batteries either from running the gen or driving all day. I have a $1,300 one year old 270 amp house battery alternator on the engine side of the coach. It does a great job charging the batteries when in motion. Anyway, I started turning off the main 12 volt master switch inside the coach rather than just turning all the lights off. I figured I still had some parisidic draws somewhere and I think this helped a bit. Wake up and find the batteries below 12 volts. Started turning the 2nd inverter (that doesn't run the fridge) to the off position in an effort to further reduce overnight drain. The inverters themselves use power I think from the fans running, etc even if your not using power from them inside the coach. I'm still waking up to batteries at 11.7 to 12 volts.

Now the last set of Interstate batteries probabley went bad before the year was up from abuse because I got so freaking tired of trying to keep them above 12.2 volts (the prescribed number to prevent the batteries going below a 50% charge. But with everything off (except the fridge) shouldn't I be getting better performance ? I'm prepared to go back to the old method of "screw it" and just let the batteries drain down to 11 volts. It takes at twice a long for them to drop from 12 to let's say 11.6 then it does to drop from 12.9 to 12. I get much better "performance" in terms of the bell curve in the lower end of the equation above.

[Joe Cannarozzi]

Jeff when is the last time you cleaned the condenser on the fridge.

It could be very plugged and thus the fridge is running ineficiantly.

You need to start to isolate things out one at a time, you will find the problem then.

[truk4u]

Jeff,

With 8 4d's fully charged, you have something wrong if they're below 12V just over night with the minimum loads you mentioned. I have 6 4d's and from about 9:00 PM to 8:00 AM with just some lights, tv and maybe a fan running, I'm still above 12.4.

Perfect example... Chris and Debbie Yates are here visiting and I unplugged Big Red yesterday at 4:00 pm to plug Chris in and I just went out and checked and I'm still at 12.5. So that's 18 hours with the fridge running as well as a fan for air circulation and all the other parasite drag stuff.

Assuming all your connections are good and no weak batteries (even new ones can have a bad cell) I wonder if your getting a full charge. The only way to test them is to load test them one at a time, completely unhooked. What do you get for a voltage read out when you think they're fully charged? It should be well above 13V. Also, once your down in the 12V range, it could take as long as 3 - 4 hours and maybe longer for your inverter/chargers to bring the battery bank back up to 13+.

[Jeff Bayley]

Joe- Is the condensor on the fridge typcially behind it or underneath it ? I had a coil radiator type thing replaced on the rear of the fridge that was for the freezer (and may have worked the fridge portion also) about a year ago. The fridge had to come all the way out of its cubby hole. Anything in the rear would have been cleaned at that time but In don't recall their being anything dirty looking there. I'm betting that what you refer to might be on the underbelly of the fridge. I'll have to get that hatch / trim piece off and check it.

Tom- Your sample of the battery life deffinitley tells me something is wrong. I can't sit with a full charge and everything off for more than an hour or two before it drops below 12.5 volts.

Jeff

[Jon Wehrenberg]

Jeff,

With that kind of voltage drop you have a serious issue.

I hope you literally run to the nearest facility that can work on your coach and that you isolate that problem.

If you are lucky you have a problem as simple as one bad battery in the system pulling all the others down with it. If not you have a substantial load somewhere, and if nothing else you need to figure out what that is, and if it is a safety issue.

You may not worry much about NYC parking tickets, but whatever is pulling your voltage down is something you absolutely need to worry about.