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Car Forum / Driving, Maintenance, Tuning / RVs / March 2007Inverter problems
I have found some weirdness about my cheap inverter. It is 2000W capacity, but gives an overload alarm when I directly plugged in a space heater which was switched to 1500W. At 750W it seemed to work fine. Every time I plug it in the shore power socket it gives a low voltage signal. Thinking that there was some big circuit draw somewhere, I threw all the breakers off and it still did this. The output voltage metered 96 volts. I realize that this is not RMS reading, but the inverter in my other RV meters 103 volts IIRC. The input voltage was just above 12V. What in the RV could cause this problem. We had a short that tripped GFIs in our house where we plugged it, but that was supposed to have repaired. Maybe I will take it home and plug our other RV into this inverter. > I have found some weirdness about my cheap inverter. It is 2000W > capacity, but gives an overload alarm when I directly plugged in a space [quoted text clipped - 12 lines] > repaired. Maybe I will take it home and plug our other RV into this > inverter. If the "capacity" is *surge* or *maximum* then the actual rated capacity is likely to be half of that. (1,000 Watts in this case.) Although some are labled with both values [1,000 continuous/2,000 surge] not all are. Be advised that the ratings are usually for an input of 13.8VDC: normal vehicular alternator output voltage. It is rated at 2000W normal and 4000W surge. I have another RV ( anybody want a old Toyota?) that has an inverter. Last night, using an extension cord, I connected the new RV to the old one's inverter. It powered up the new RV just fine. I then reversed the cord powering the old RV with the new inverter. It worked just fine. My problem is settling down to the fact that I can't power the new RV with the new inverter. I get a low voltage signal. >> I have found some weirdness about my cheap inverter. It is 2000W >> capacity, but gives an overload alarm when I directly plugged in a space [quoted text clipped - 23 lines] > Be advised that the ratings are usually for an input of 13.8VDC: normal > vehicular alternator output voltage. > It is rated at 2000W normal and 4000W surge. > [quoted text clipped - 4 lines] > fine. My problem is settling down to the fact that I can't power the > new RV with the new inverter. I get a low voltage signal. Check the voltage at the power outlet - it may be low. Also, check the fuse/circuit breaker on that socket. >Check the voltage at the power outlet - it may be low. > >Also, check the fuse/circuit breaker on that socket. You need to check voltage at actual inverter input terminals and watch it under load and surge conditons. My guess is that input voltage is too low for that particular inverter. While most are rated at 13.8 volts they should pe4rform okay down to 12 volts or a bit higher but will start to soften up a lot under heavy load below 12 volts. Also there is the wave shape of inverter output as to how "effective" its voltage output is. Some use square wave and better ones use a modified square wave meant to mimic a sine wave some what. This can effect overall performance as some devices are sensitive to voltage wave shape as well as level. What are you powering and feeding it with? ----------------- TheSnoMan.com The problem is that there is really no load on the inverter. I threw all the breakers and still the inverter gives the low voltage alarm when the RV is plugged in. I had no problem powering the new RV with the old RV's inverter or powering the old RV with the new RV's inverter. I just can't seem to power the new RV with the new inverter. To negate the batteries as a source of problem, I have been testing with the motor running. >>Check the voltage at the power outlet - it may be low. >> [quoted text clipped - 12 lines] > ----------------- > TheSnoMan.com >The problem is that there is really no load on the inverter. I threw all >the breakers and still the inverter gives the low voltage alarm when the RV [quoted text clipped - 4 lines] >To negate the batteries as a source of problem, I have been testing with the >motor running. Okay let be understand this. It gives a alarm when what is plugged in to what that triggers alarm? Also is alarm on inverter itself or in RV power panel? ----------------- TheSnoMan.com >>The problem is that there is really no load on the inverter. I threw all >>the breakers and still the inverter gives the low voltage alarm when the [quoted text clipped - 10 lines] > to what that triggers alarm? Also is alarm on inverter itself or in RV > power panel? --------------- The inverter gives a low voltage alarm whenever it is plugged into the shore power cord. The guy at HF told me that I had to change the ground connection to the frame of the vehicle. I thought I did that a minute ago, but the thing still has the same problem. My only hope is to start the engine so I know that the voltage is good and try again. Any chance the power is wired backwards? (hot-neutral) Steve >>>The problem is that there is really no load on the inverter. I threw all >>>the breakers and still the inverter gives the low voltage alarm when the [quoted text clipped - 18 lines] > still has the same problem. My only hope is to start the engine so I know > that the voltage is good and try again. >Any chance the power is wired backwards? (hot-neutral) You may be one to something. There my well be a neutral polarity issue on ground cord or RV. Something is wrong in the return circuit wiring. Maybe neutral and ground is swapped somewhere too. ----------------- TheSnoMan.com I get voltage from both the negative and the ground. If it were backwards, I would get voltage between the negative and the positive, but not between the positive and the negative. They are letting me return it if I pay for shipping. No problem. I would sure like to buy a 2000W unit locally. > Any chance the power is wired backwards? (hot-neutral) > [quoted text clipped - 24 lines] >> still has the same problem. My only hope is to start the engine so I >> know that the voltage is good and try again. >I get voltage from both the negative and the ground. If it were backwards, >I would get voltage between the negative and the positive, but not between [quoted text clipped - 3 lines] > > I would sure like to buy a 2000W unit locally. He was talking about the AC side. What are you talking about? Oh, I don't know. I can tell you that everything seems to work well from a shore power perspective and I did power the new RV with the old RV's inverter. >>I get voltage from both the negative and the ground. If it were >>backwards, I would get voltage between the negative and the positive, but [quoted text clipped - 5 lines] > > He was talking about the AC side. What are you talking about? >The inverter gives a low voltage alarm whenever it is plugged into the shore >power cord. [quoted text clipped - 3 lines] >still has the same problem. My only hope is to start the engine so I know >that the voltage is good and try again. My inverter plugs into the 12V battery and outputs to some 110V outlets. I am disunderstanding. >My inverter plugs into the 12V battery and outputs to some 110V >outlets. I am disunderstanding. IF the neutral are crossed relative to true ground or hot to neutral, it can cause some strange things to happen when it connected to a external AC source.. I am assuming that this problem happenes when external AC power is attached to RV. ----------------- TheSnoMan.com >The problem is that there is really no load on the inverter. I threw all >the breakers and still the inverter gives the low voltage alarm when the RV >is plugged in. I had no problem powering the new RV with the old RV's >inverter or powering the old RV with the new RV's inverter. I just can't >seem to power the new RV with the new inverter. You don't have the inverter directly grounded do you? This is a great way to fry many cheap inverters. It was grounded to the batteries' grounding point. I have since grounded it to the frame. >>The problem is that there is really no load on the inverter. I threw all >>the breakers and still the inverter gives the low voltage alarm when the [quoted text clipped - 5 lines] > You don't have the inverter directly grounded do you? This is a great > way to fry many cheap inverters. >It was grounded to the batteries' grounding point. I have since grounded it >to the frame. This is a case of where a diagram or schematic of how you are hooking everything up would be a GREAT help in troubleshooting your problem. ----------------- TheSnoMan.com >>It was grounded to the batteries' grounding point. I have since grounded >>it >>to the frame. > > This is a case of where a diagram or schematic of how you are hooking > everything up would be a GREAT help in troubleshooting your problem. LOL! It sure would have! >I have found some weirdness about my cheap inverter. It is 2000W capacity, >but gives an overload alarm when I directly plugged in a space heater which [quoted text clipped - 7 lines] >but the inverter in my other RV meters 103 volts IIRC. The input voltage was >just above 12V. That's over half dead on a 12-volt system. Are the battery/batteries getting older? If you can add water do they need water added? Are the batteries good and charged? How long is the cable connecting the inverter to the, hopefully more than one, battery? How thick? If you're trying to do this off of one battery, forget it. >>I have found some weirdness about my cheap inverter. It is 2000W capacity, >>but gives an overload alarm when I directly plugged in a space heater [quoted text clipped - 5 lines] >>all >>the breakers off and it still did this. are you turning off the charger?? i know you threw all the breakers, but there may be a different breaker someplace else for the charger, or if it's one of those load centre things (charger/converter, mains breakers, DC fuses and all wiring in one unit) then it may be impossible to turn the charger off by flipping a breaker, so what's happening is your trying to re-charge the batteries that are providing the power to run the charger, if the charger is a big un, then it'll quickly pull the battery power down enough to low volt trip the inverter, before i wired in my change over relay, i had to remember to turn the charger off at it's switch before plugging the inverters output to the motorhome's input mains socket, Forgot to do it once, i only have a little 20 amp charger, and back then a single 110 AH battery, it took about 10 minutes before the inverter shut down with the low volts alarm going, and both the inverter and charger were red hot from trying to supply each other power. >>>I have found some weirdness about my cheap inverter. It is 2000W >>>capacity, [quoted text clipped - 8 lines] > > are you turning off the charger? I found the breaker that controls the charger. I can get the lights to brighten and dim by operating it. It is off for the test. > if the charger is a big un, then it'll quickly pull the battery power down > enough to low volt trip the inverter, [quoted text clipped - 7 lines] > down with the low volts alarm going, and both the inverter and charger > were red hot from trying to supply each other power. What did you use as a change over relay? > What did you use as a change over relay? Bog standard 16 amp 4 pole changeover relay with a 12 volt DC coil, i'm in england, and our shorepower is 230 volts at 16 amps. the shore power input wires went to the normaly open contacts on 2 poles of the relay (switching live and neuteral) the inverter live and neuteral goes to the normaly closed contacts of the same 2 poles of the relay, and the centre contacts go to the breaker box. Then a link wire from the shore power cable goes to a 230 V AC to 12 volt DC switched mode power brick, and the output powers the relays coil, did it that was as the relay is under where my head is in bed, and didn't want the buzzing of an AC relay coil annoying me all night when on shore power. the 2 spare poles of the relay... one was used to disconnect power to the charger, the other power to the fridge AC power feed, so that they only get power when the relay is switched by the shore power being plugged in, When shore power is not present, the inverter power is fed to the electrics except the charger and fridge AC side, i have a main switch for the inverter so it's not on all the time when powers not wanted, of course the earth wires were all linked together without going through the relay's contacts (shore power, inverter and power out to the breaker box) as you dont want to be breaking the earth connections when switching from shore power to inverter power. I got the relay from a surplus store for next to nothing, and the power brick i already had, plus a box to put it in, so my automatic changeover relay cost me about £10 to make, similar items are sold for £100 at motorhome shows here. >>I have found some weirdness about my cheap inverter. It is 2000W capacity, >>but gives an overload alarm when I directly plugged in a space heater [quoted text clipped - 14 lines] > That's over half dead on a 12-volt system. Are the battery/batteries > getting older? If you can add water do they need water added? This happened even when the engine was on. > Are the batteries good and charged? How long is the cable connecting > the inverter to the, hopefully more than one, battery? How thick? If > you're trying to do this off of one battery, forget it. The cable is a #2 about 18 feet long. |
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