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Old 02-26-2007, 10:12 PM   #1
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Help! Inverter or battery or both?

This is going to take a minute, so please stay with me. Bought my first vintage trailer Friday, '65 Safari. Picked it up and all electrical seemed fine. First night, used all interior lights and heater on battery power, no problems. Second night had plug in and ran on 120v all night, no problem. Next morning while plugged in, reading light above middle couch went out. Thought bulb was out, didn't think much of it. Later while trailering, no lights or any other systems on battery power when I stopped to check and make sure everything was riding OK. Got home and plugged it in, still no lights, but noticed reading light above middle couch was working, as was water pump. After a few minutes plugged in, lights all came on and everthing was normal. Yesterday, had battery tested at O'Reilly's, and it showed 'bad' after they charged it and checked it. Went to buy new Interstate today, they said old one was OK, so I went home and took closer look at electrical. Noticed the 'battery' screw-in fuse receptacle on the Univolt showed signs of heat and also that the center contact point where the fuse makes contact in the bottom had come loose and fallen off. I removed socket, repaired contact point and re-installed with new fuse. Now, I've got nothing but reading light and water pump, plugged in or not. Don't know where to start. I have power to the Univolt, but neither fuse socket is hot. D/C fuse block is hot, as is 120v breaker box.

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Old 02-27-2007, 04:39 AM   #2
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Electrical problems.

Hi Chris; There is a lot to consider of what the problems may be. First you need to visualize and compare your electrical system to that of plumbing. Since you cannot see electricity it is difficult to understand it. Therefore for that reason I am making this recommendation. Battery is nothing more than a storage container. The larger the container the more it can store. The volume stored, is amount of amperage available.

This stored amperage [volume] came from the charger which had to utilize pressure to fill your battery [tank]. Since that could only be done by means of pressure [pump] which is set for the safe level of pressure for which the container is rated for. In which case is 12 Volt. Therefore a 12 Volt battery rated at 800 amp, can be compared to a tank which can hold 800 gallons of water at required pressure of let's say 12 PSI. For as long as the pressure exists, the battery should give you it's rated amperage per hour. However, once the pressure has diminished below 12 volt the battery will not deliver rated volume, because delivery depends on the pressure behind it.

The battery however is only a source of stored energy. From here on are wires, fuses etc. All of that is responsible for distributing that mass of energy under pressure, just the same way that plumbing distributes the water. If you have no pressure you have no flow. No volume, no flow. Size of wire can be compared to size of pipe. The larger the pipe the more volume it can deliver in given time. The high demand for volume through a larger diameter pipe, will however drain your 800 gallon tank much quicker than a small diameter pipe at the same rate of pressure. This is proportional to demand and size of pipe supplying the demand.

If your pipe is too small for the demand, two things will happen. You will not get enough volume needed and in case of electricity, and the wire will become overloaded and the demand for energy flowing through it, will create heat because the component draws more than the wire can supply. End result, blown fuse or burned out wire. On the other hand the pipe supplying the energy may be large enough but it has restrictions in it [clogged up]. The result is the same. The wire is only as good as it's loose or weak connection. If the wire has 12 strands and it is rated for 20 Amp and six of them are broken off at the connection then that wire can only supply 10 Amps. Also, as the demand exceeds the wire's rated capacity it creates heat, which even further drops the available amperage by increased the resistance in the wire. Hence, low available amperage creates heat. If any circuits which get hot, there is some form of restriction in that circuit.

Since you own a older unit you must carefully inspect all wire connections
which are accessible to your inspection. Make sure they are not frayed, broken or loose. This includes all grounds as well because they are the continuation of your pipe, and a viable part of your closed loop circuit. Chances are you have loose connection in your distribution panel, which may be affected further by heat generated by weak connection. Second issue may be your Univolt. They were not most reliable source of charging or power supply, and I would recommend upgrading it.

Visually check all connections first and if you find anything unusual PM me and I will try to help you. Thanks, "Boatdoc"

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Old 02-27-2007, 04:51 AM   #3
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The BoatDoc gave a very nice example of how electricity works! Go BD!!!

I would concur that the first thing to do is dump the Univolt! Replace it with a modern switch-mode converter with 3 stage battery charging. Your battery will thank you and will last longer also!

Then check EVERY electrical connection that you can find to be sure that they are all clean and TIGHT!!! That should solve most of your problems unless you have frayed/burnt wire issues that are hidden from sight.

Good Luck
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
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Old 02-27-2007, 05:01 AM   #4
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Small thing but I found my fuses corroded and they would get warm with just a few lights on. Cleaned them up and everything works fine now. How do your fuses and connections at the fuse block look?
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Old 02-27-2007, 06:57 AM   #5
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Thanks for the advice. Last night, after I posted my question, I did some reading about others with similar problems and the advice they'd been given. Went on e-bay and found an Intelli-power 9245for $100 from an e-bay power seller. He says it's brand new with 2 year warranty and for $20 shipping, I'll have it later this week or early next. It's so cheap, the skeptic in me can't help but wonder if it's not a re-conditioned one, but I guess I'll take my chances. I realized during all my reading last night that my Univolt isn't making the humming sound everyone was talking about, so I'm willing to bet it's not working at all. Will check my connections as suggested and, when my new Inteli-power comes in, I'll install it, along with a new battery, and I think I'll be OK.
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Old 02-27-2007, 11:46 AM   #6
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You will need to pull the big fuse from the Univolt and use it or a similar fuse. I just replaced my Univolt with an Iota two stager last year. Here's the thread I made on it. I'll try to get some of the other pictures up tonite on the install. Yes, replacing the Univolt is certainly one of the first things to do. I still would not discount a bad battery, however. You may have more than one weak link.


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