Golden_HVAC
Fulltime, CA, USA
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Hi,
One way to solve the "Problem" is to use a tiny inverter to run just the TV set, and then use the main inverter to run everything else.
When I saw this post, I was thinking low battery voltage is causing the interference. Then I read that you have a really large battery bank, and I was thinking what problem now? Then I read about how the voltage dips while the microwave is running. This will cause a slight problem.
The pure sine wave inverter is actually a stepped square wave that has up to 50 small steps in each waveform. So the waveform is slightly square steps on each waveform. You really have to see it on a oscilloscope display to visualize it.
So it looks like you can either put up with the wiggles on the screen a few minutes a day, or get a dedicated inverter to run the TV. The biggest advantage to running a 150 watt inverter for just the TV is it will be much more energy efficient than the larger inverter, so it will draw less amp hours from the battery to run the TV than the larger inverter. A 150 watt inverter will also run a VCR or DSS or DVD at the same time as the TV set, without overloading it.
You can find out more about how an inverter works if you contact the inverter repair people at this website. SolarOnSale.com They repaired my Trace inverter many years ago, and do factory repairs of inverters.
Good Luck,
Fred.
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frecku
Idaho
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Quote:After reading your latest replies again, I noticed you had the batteries isolated into 3 separate battery-banks. I would suggest you disconnect the isolators and parallel the battery-sets. It won't cost you any money, and they may cause the momentary voltage drops. You can always hook them back up if nothing changes.
The reason I have 3 separate battery banks is by design alone. The 1 original bank is by the entrance step, the 2 is in the rear 17' back and the 3 also rear 19' back. There is no way to combine all 3 in one spot. I carefully calculated the voltage drop and used the correct cable lenght to balance each load precisely so no bank depletes faster. In fact using a claw Amp meter I get 53 amp draw from each bank when the microwave is running, they are perfectly equalized.
So in short hookup in series/parallel is out of the question. However all 3 banks join at a single bussbar and the inverter draws its power from that source.
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pianotuna
Regina, SK, Canada
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Hi ron.dittmer,
Perhaps the OP should ground his inverter to the chassis?
When I had only 3 twelve volt batteries (they were five years old) I had no problems running my microwave via the inverter.
I do notice interference on my radio from running the fluorescent lights on AC power--and it happens on the FM tuner!
ron.dittmer wrote:frecku,
99.99% of us here are not able to run the microwave off the inverter as we don't have 6 batteries to make that work. You have a very unique problem the rest of us cannot comment informatively.
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
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frecku
Idaho
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The inverter is grounded to the chassis by a 1 AWG wire, all appliances do work including the microwave except when the TV is on during microwave operation it has a slight distortion, i.e. wobble on the screan.
I guess i will learn to live with it.
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smkettner
Southern California
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Three battery banks? Are all the main feed cables tied together to minimize creating an inductive loop?
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
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frecku
Idaho
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All 3 banks come together at one bussbar from which the inverter draws its power.
The interference on the TV is not related to the operation of the microwave exclusively, as mentioned earlier any simultaneous use of a high Amp item i.e. toaster or kettle produces the same distortion on the TV.
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MNtundraRet
Bloomington, MN
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Greg:
I think we may have gotten off the track for the real problem. Let's assume the setup is okay. A 100% charged battery is 12.6 to 12.7 volts. A 0% charged battery is 11.8 volts.
When you tested the batteries, you stated almost 12.9 volts. That is a surface charge. When you tested the batteries with the heavy load you stated around 12.0 volts and 11.7 volts. That is an extreme voltage drop. I think the current problem may actually be a battery, or two, with a bad cell. Try to isolate the problem by checking voltage, with a multimeter, at the terminals of each individual battery-pair, while under load. The fact that the reading of 12.49 volts (85% charged battery) for television setup alone suggests some bad batteries. The television setup alone on 100% charged batteries should have held a 12.6 volt reading for most of the day, for your battery-bank size.
Mark
Mark & Jan "Old age & treachery win over youth & enthusiasm"
2003 Fleetwood Jamboree 29
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frecku
Idaho
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That is an excellent idea, i will take those measurements and get back to you. You did notice however in my prior posts that my banks are 17' and 19' away and that when the TV is switched off the voltage at rest returns back to 12.93V
As to the voltage at 100% capacity, you are right it used to be 12.62 to 12.68, but since I upgraded to a Progressive Dynamics PD9270 with inteli-wizzard I now routinely get 13.0-13.15 at rest.
The inverter also has a built in 120 Amp charger, I can use either one on mu setup, just a matter of switching off a breaker. The inverter has a 5 step charging program and my resting voltage was as high as 13.4 and then settled after a few hours and stabilized at 13.1
The difference on the light output is amazing.
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MNtundraRet
Bloomington, MN
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One thing I forgot to mention is the easy way to find a bad battery. A bad battery cannot recharge to full capacity. That means if you recharge your battery-bank, all batteries will read at least 12.6 volts or have the excess surface charge. If you now tested the system by using up amperage equal to 10% of your battery-bank (900 amp bank - use up 90 amps) and stopped leaving the RV off shore-power. Let the batteries rest an hour or two to recover. If all batteries were good as new, you should see 12.5 volts (90% charged) at each battery. An old or bad battery will be lower. Most likely 12.2 volts (50% charged) or less. A bad battery will reach 12.6 volts, acting like it is fully charged, much more quickly than a good battery. Once under load the voltage will quickly drop to the battery's true voltage (% charged).
Mark
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klhutch
Sububan Chicago
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I think you first need to determine if the problem is radiated interference from the inverter or microwave or conducted interference through the power lines. An inverter generates some unintended high frequency noise as it operates. The more current you draw from the inverter the more noise power is generated. So the fact that you have interference issues at the high current level the microwave draws is understandable.
A second inverter would partially isolate the power connections between the TV and microwave although they are still connected via the battery input lines. I think a better test would be to run the TV from an extension cord connected to shore power while the microwave runs from your inverter system. If the interference goes away then the path to the TV runs through the power system. In that case a separate inverter for the TV may solve the problem. Putting ferrite interference suppressors on the DC leads to the two inverters as Ron suggested would help prevent the interference from using the common DC connection of the two inverters as a path to the TV.
If you still have the interference when the TV is running off an extension cord to shore power then the path must be radiation from the inverter or the wiring into and out of it. The wiring is the most likely culprit and ferrite cores should help suppress radiated energy as well as conducted energy.
As others have suggested the issue could be variations of the AC Voltage to the TV that your meter just can't capture. The shore power test will fix this problem too and most likely, as has been suggested, a separate inverter for the TV will also fix it. In this case the ferrite cores on the wiring would be unnecessary.
Your battery system sounds solid, with enough redundancy to tolerate a weak battery. But it doesn't hurt to double check it.
Ken
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