Building a TRUE Sinewave UPS for My DVC-500

I started this project shortly afetr installing my Harman DVC-500. Two weeks after it was up and running, we lost electricity. "No Problem" I thought, I'll just go outside and start the whole-house generater. Well, that took about 10 minutes total elapsed time that the stove was without electricity. But as I discovered, without the Draft fan and Combustion fan running, the fire quickly dies from lack of oxygen.
OK..... so I begin to get ready to restart the stove. But Wait! Where is that funny buzzing noises coming from. Uh-ohhhh, its the DVC-500! The stove doesn't like the taste for Generator 'lectricity! Finicky little stove! It want a TRUE Sine Wave waveform. The Modified waveform from the generator just won't cut it.
OK..... so time to look for a UPS with a true sine wave. "No Problem!" I says to myself, the Harman Dealor offers one! Called up the dealer and got the price for it, and, "Oh, BTW... the price DOES NOT INCLUDE THE BATTERY". After I stopped laughing, I promptly thanked him and quickly hung up.
OK.... so time to BUILD my own True Sine Wave UPS. The DVC-500 only uses 186watts.

And thus the Saga begins.....

The components I choose are readily available "Off-the-shelf". Heres is my parts list:
1) 300/600 True Sine wave Inverter - 12vdc input, 120vac output, purchased off of ebay for $103
2) Schumacher "Speed-Charge" Ship-n-shore charger. Part # SSC-1500A. FULLY automatic , from Walmart - $54
3) EVERSTART MARINE Battery, model # 24MS-6. It has 625 Marine cranking Amps at 32F. Walmart - $58
4) Relay 4PDT 110vac coil, 5 amp 600v contacts. I already had this, I guesstimate $15
5) Battery box. Walmart - $7
6) Miscellanious wires, most of the wires I used, came with the inverter and charger.

I started by disassembling the inverter. Surprisingly, they used the entire aluminum cover as a massive heatsink. OK,,, I won't be able to shrink the sides of it. But the length, with all switches, outlets and lites, removed from the sides of the inverter, I will be able to cut 1 1/4" off the length of the inverter case/heatsink.

Time to disassemble the charger. There was a LARGE compartment in it, just to house spare wires. I will use this compartment to install the inverter. Once charger was apart, I measured the empty compartment. It was 1/4" too narrow to house the inverter heatsink. DRAT!
OK.... time to move the PC board in the charger, over by 3/8". Re-drilled the mounting holes, filed some corners, and had to add a jumper on PC board, because one new drill hole went right thru a circuit path. Re-mounted Charger PC board. measured again. YES! Got room now, for Inverter PC board.! Just had to remove 1 1/4" inches of the inverter case to fit it between two screw posts in the charger box.

Time to start wiring. The 12v wires going to the battery, will be soldered to the charger's OUTPUT leads, and the Inverter's INPUT leads. No need to seperate these with a relay.

The 110vac plug will be used to bring in grid power, and will also be used to run the Charger. The plug wires are soldered to the Charger INPUT leads, and also to the relay coil, and two legs on the relay. This will feed the OUTLET so the DVC-500 can run on grid power when available.

The 110vac OUTLET in the inverter gets both White and Black wires connected to the relay. When relay coil is powered, the 110v OUTLET will be fed by Grid. When relay coil is not powered (NC) the 110v outlet will be fed by inverter. Also, when relay coil is NC, IE. no grid power, the inverter will be powered up. I did this by simply removing the SPST ON/OFF switch from the side of the inverter, and connecting the leads to a leg on the relay.

I was concerned the relay would begin creating heat, since the coil was powered while on grid power, it would be ON 99% of the time. So I connected the mini-muffin fan that was in the inverter, to the 12v battery/charger/inverter circuit. What this does, is the fan is powered when the inverter is on. and it is also powered when the relay coil is powered. It now a dual-function fan.

On one side of the charger case, I cut a holes for the 110vac outlet, for the inverter fuse, for the 110vac plug wire, and slots for the airflow over the relay and inverter. On the other side of the charger case, I cut a circular hole, and mounted the inverter muffin fan.
On the top of the charger case I drilled two holes for the inverter's Power-on lite, and Low-voltage Warning lite.

After making all connections and mounting everything with either RTV or HOT-glue, I buttoned the case back together.

Time to test....

Connected battery cables to battery. Got a quick "CHIRP" from the inverter's low-voltage alarm (Scared the piss out of me!) the inverter-on lite, and the inverter muffin fan kicked in. All looks good so far. Ok, test 110vac outlet. Testing good 125vac. Plug in a dimming lamp. Lamp works, and dims properly.
Time to test grid power. I left the battery connected. Plugged UPS plug into wall outlet. Charger lites came on. Lamp that is plugged into inverter's oulet never blinked, but inverter powered down as expected. The Lamp is now running off of grid power, and the charger is now charging battery . COOL!
As a side note, the reason I chose this charger is because of its fully automatic operation. IF NO BUTTONS ON THE CHARGER ARE PRESSED WITHIN 10 MINUTES OF POWER-UP, It goes into Auto-charge mode. NICE! It first tests to see if a battery is connected. If so, it tests to see if it needs charging, If so, it starts charging at 2 Amp/Hr rate. Once it senses full capacity, it STOPS chargeing, and goes into Monitoring mode. Testing the battery everynow and then, to see if it needs charge. It could start a Trickle charge, if required, during this mode. All of the above functions can be overridden. All of the chargers features are still functional.

OK.... so now a test lamp works on inverter, the charger works, the inverter works, time to test it on the DVC-500.

Late Friday nite, I plugged the UPS into the wall by the DVC-500, then plugged the DVC-500 into the UPS. I let it run this way all nite. In the morning, I pulled the UPS plug out of the house outlet, to simulate a loss of grid power. The Inverter "CHIRPed" once as it powered up, then the stove came right back up to speed. Keep in mind, there was a 3 second delay from the time the grid power was removed, to the time the inverter powered itsself up. I can live with that. (Going from inverter power back to grid power shows no noticeable delay at all). Anyway, the stove is up and running on battery/inverter power. I tested it under the "Load" condition. I am getting 124vac from the inverter, with the DVC-500 running. The battery shows 15.2VDC. I tested in another 2 hours, and the inverter showed 123.4vac and the battery was 12.4vdc. After another 30 minutes, I had to empty ashes and fill hopper. Nothing out of the norm was noticed. Draft motor ramped up to full speed as expected. After another 30 minutes (Total of 3 hours now) I got a audible warning tone that the battery was low. I tested output again, and inverter was putting out 121.6vac. Battery was at 11.7vdc. After 10 minutes, the inverter's LOW Battery lite came on, and the inverter shutdown, then the DVC-500 shutdown. I pluged the UPS plug into the wall (grid power) and the charger started charging, and the stove started running on grid power.

SO.... on a 625Amp deep cycle battery, the DVC-500 ran for 3 hours.

My only change now, would to put a SPST switch in line of the relay coil, to allow me to turn off the coil manually. What would this do?
When on GENERATOR power, IE.. grid power is lost, but I have my whole-house generator running, the charger in the UPS will charge the battery WHILE the DVC-500 is running on the inverter.
Keep in mind, ALL of the charger's features are still fully operationable, and override-able at any time. If I am running the house on generator power, I still don't want the DVC-500 to use Gen power. It has a Modified Sine Wave output, that the DVC-500 does not like. The DVC-500 will continue to run on UPS power. BUT I have to change the rate of charge, at the charger. This charger is capable of charging at 2Amps, 10Amps, or 12Amps. Default is 2Amps. Easy to switch it to 12Amps, to charge battery AND feed invertor. COOL!

SO.... By allowing the charger to operate at the same time the inverter is operating, the generator can be running the charger the charger can be charging the battery, the inverter can be running off of the battery, and the DVC-500 can be running off of the inverter.

My thanks to Tom M and JB Sparks for being another set of Eyes and Ears as I progressed with this project.

See attached slide show.

Great Job. Thanks for the show.

http://www.rollsbattery.com/
http://www.dcbattery.com/optima2.html

offshore lighthouse back up power uses the rolls cells. I prefer the optima blue top deep cycle 1K amp/hr

but the wallyworld one is easier to get warrenteed prob. again, good project completed! thanks

Poconoeagle wrote:Great Job. Thanks for the show.

http://www.rollsbattery.com/
http://www.dcbattery.com/optima2.html

offshore lighthouse back up power uses the rolls cells. I prefer the optima blue top deep cycle 1K amp/hr

but the wallyworld one is easier to get warrenteed prob. again, good project completed! thanks

Thanks Poconoeagle, Yeah, I know I'd get longer run times on the Optimas, but cost was a factor with this project, so I had to go "Cheap".

GREAT JOB Chris!! :nice:

Good job on the project. What kind of generator is it that does provide a pure sine wave output?

Yanche wrote:Good job on the project. What kind of generator is it that does provide a pure sine wave output?

Thanks Yanche.
My generator is a honda 8000watt 13HP. It provides a 60hz Modified Sine Wave 120 or 240vac. Most everything, including the oil furance, refridgerators, TVs, well pump, etc.... will run on it. But the DVC-500 really complains by making screeching noises. The Radon fan also complains about the Gen power. I'll make sure the next generator I buy produces a true sine wave.

I bought an older 1500va (handles 950watts) APC UPS. I then rewired it and hooked up two Costco marine batteries. I've tried running my Alaska stove on the inverted power with no problems. This UPS is suppose to put out a pure sine wave. The UPS was originally 400.00. I paid about 100.00. I almost purchased a Tripp Lite inverter charger for about 450.00 that handles about 1000 watts and is made for my application but decided to get the lower cost way. http://www.tigerdirect.com/applications/searchtoo ... 4&csid=_27

Very cool! What a fun project. Thanks for sharing the details. Ya done good! *smile*

For those that it might help.... I have access to deep cycle gel batteries CHEAP. They are used and come from wheels chairs. You see, wheel chair people change batteries by the calendar. Some are spent, but by far, most are still close to new. I can get them for $10 each. Of course shipping might kill you if someone wanted one. 50 amp hours are the common ones, but now & then I can get 70 amp hour ones. The other thing is, they MUST be charged by a "smart charger". A regular charger will not work.

You likely could clean up the generator output with some inductive filtering. Find two identical junk microwave ovens. Remove the transformers and wire them up secondary to secondary. The transformers will do the filtering. The high frequency harmonics produced by the generator will be converted to heat in the first transformer. Whatever it's secondary voltage is will be changed back to line voltage by the second identical transformer. Keep in mind this solution still has the potential for failure. High voltage spikes might damage the transformer, in just the same way it would damage the stoves motor, by breaking down the enamel insulation on the windings. Don't go overboard by putting to much load the transformers. Try and match the size of the microwave in watts consumed to the watts consumed by the stove motors. Larger wattage on the microwave transformer is better. Doing this for the entire generator's load would require AC welder transformers or if you want to get carried away two identical power company step down transformers. If you try this be careful the voltages can be lethal!

Yanche wrote: If you try this be careful the voltages can be lethal!

Been there, done that. When I was 12 or 13, I saw an article in a magazine (I think Boys Life) on how to make a Bugg Zapper out of a door bell transformer, yep, just feed 120vac into the secondaries, hook up the primaries to parallel wires wraped around 4 wood dowels mounted on two pieces of plywood. Well, I accidently touched the primaries, now producing, I don't know, 600volts or so. I'll tell u what, I'm glad to be alive. Never felt a shock like that before or since. I can now take 110volt shocks without even flinching , no problem!

You could just buy a used UPS like I'm using and then power it with the generator and let the UPS power the stove.

traderfjp wrote:You could just buy a used UPS like I'm using and then power it with the generator and let the UPS power the stove.

Thanks, I looked into that....
Most of the small Computer UPS's (APC, Tripplite, etc....) produce a Modified SineWave output, cuz computers don't care what kind of power feeds them. They have their own inverters and filters, since the CPUs in them are VERY sensitive to what power feeds them.

UPDATE:
I ran my second duration test today. I'm getting 3 1/2 hours run time on the battery. Thats pretty consistant with the first test. It's ALOT lower than I predicted. I need to measure total drain from the battery while the inverter is on. Unfortunately, my multimeter can't do this. ( I need a new mutimeter ).
Anyway, I went ahead and made my final modification. I installed an SPST toggle switch on one leg of the Relay coil. This has no effect when there is no external power source (Grid or Generator).
But once I get my generator up and running, I can flip this switch, DE-ENERGIZING the Coil. That will power-up the charger WHILE the inverter is still feeding the stove. Now, the battery is being charged, while it is feeding the inverter. I may need to override the 2Amp Default charge rate, Bump it up to 10 or 12 Amps, But it works, already tried it .

Still, a very cool project. You'll get it perfected I'm sure.

I built an electric motorcycle last winter. It works as designed, but while researching and building I learned one thing about batteries and calculating how much power they'll deliver. If you know the Ampere hours of the battery and how much you are drawing, do the math and calculate the time they should last. Now, divide it exactly in half. That's closer to the actual life you'll get per charge. Now, the faster you discharge them, the less efficiency, so for you, you might get a bit more then half. For a motorcycle that is asking a lot, half is right on.
Another battery tip: Charge soon and charge often! The deeper a battery is discharged, and the longer you wait before it gets recharged has a big effect on it's life.

Well, its been very windy for the last 24 hours. We finally lost power and phone at 4:00 today. tree fell across wires.
The DVC-500 kept right on running, no issues. The UPS works!
I started the generator about 5:00, and the UPS battery started charging automatically.
No surprises.