Mobile UPS battery backup

[Dan Robinson]

I'm trying to use an APC UPS unit in my car that will keep power from getting killed to the plugged-in devices every time I start the car, and also allow us to keep our network's router running while we stop for dinner, etc. The problem is, the UPS device does not like the inverter. The 'site wiring fault' alarm goes off and the unit will not power on. The documentation shows this will happen if there is not a proper ground. Although my inverter is grounded to the car, it is not connected to true 'earth ground' which is why I suspect the UPS is objecting. I haven't even plugged anything into the UPS yet.

Has anyone been successful getting a UPS to work off of an inverter in their vehicle?

 

[Tyler Allison]

I haven't done extensive testing but I tried to run a UPS for my home computer off of a 12V solar system using an inverter (it's basically car power, just that instead of an alternator I'm using the sun)...it complained as well with all the beeping and what not and would not allow me to power anything off it.

There's definately something going on if you are having the same issue.

I don't see how you can ground the inverter. I have a black and a red wire...but no ground location.

Maybe you have to move up to the more expensive true-sine wave versions that are hundreds of dollars, instead of the Walmart style I suspect you and I tried.

 

[John Erwin]

Of course this is just my opinion, by why not simply use a second car battery and run the inverter off that?

I'm guessing that you don't want the hassle of the extra installation issues... however let me tell you about a portable setup I used for awhile. I had a deep-cycle battery in a plastic "battery box" and had an inverter mounted on top. I used a trickle charger to keep it topped off from the cigarette lighter. Since I didn't have any big loads off this supply (no radios, only a laptop and cell phone) it could run for hours. Not an entirely ideal solution, but cheap and worked well for the purpose I used it for. Since then I've installed a permanent second battery and use an isolator.. power to spare and I don't run down my main battery.

 

[John Diel]

Just a real SWAG here, but you might try running the UPS off of a power strip rather than plugging it straight into the Inverter. It "might" be the circutry is reading the ground fault from the inverter that may be isolated to the Inverter. Bypassing that with the power strip may be enought to remove the ground fault condition.

I haven't done this though. It's simply a guess. However, just hardwiring the inverter to the battery should take care of your power issues. Just make sure you use the heavy gage wiring. Make sure you have a good battery as it will continue to draw power from the battery once the engine is turned off. You run the risk of a dead battery, but for short stops, it shouldn't be an issue. I've had mine run for about an hour with no apparent ill effects to the battery or it cranking charge.

I also have an inline breaker from the battery to the equipment feed. That helps protect the equipment from the power surge during engine start.

 

[Tyler Allison]

Since then I've installed a permanent second battery and use an isolator.. power to spare and I don't run down my main battery.
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What isolator did you use. Care to write up a 'howto' with pictures?

 

[John Erwin]

What isolator did you use. Care to write up a 'howto' with pictures?
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Sounds like a good idea Tyler, but I'll wait until the season is over and I have a bit more time for it. I plan on making a few minor changes to the system so that would be a good time for photos and a writeup. I used an isolator from Hellroaring Technologies. Basically I wanted to be able to run devices while the engine was off and not worry about killing my main battery. To fulfill my other need (being able to run high-current loads while driving) I chose to upgrade my alternator to a high-output model from Mean Green.

I tend to find that power is the one area many people tend to scrimp on a bit for their vehicle, even though they've spend a lot of money on many other areas. Makes for a much better experience in my mind when you have the power when/where you need it.

 

[Dan Robinson]

Thanks for the suggestions. We might end up just getting the isolator and second battery because we could use it anyway.

We are running a 750 watt inverter hardwired to the main fuse terminal box under the dash with heavy gauge wire (the closest to the battery we can get without poking another hole in the firewall). Off of the inverter, we have a surge protector power strip that all of the sensitive electronics plug into (laptops, routers, camera chargers). I've tried plugging the UPS into both the inverter and the power strip, and both result in the alarm. All the UPS really needs to support is the one router, since the laptops won't turn off when they lose AC power momentarily.

I've been running a setup like this for the past four seasons and the only drawback is that it wears my battery out faster. After about a year, the battery won't hold a charge when the car is left sitting for more than a day or so, requiring the use of the jumper pack. But, a new battery only costs $40 so it's not a big issue to replace it every year.

 

[Brandon Clement]

Rockford Fosgate has a battery that is ideal for this but it is very expensive. I went to the local distributor for Excide batteries and they actually make the battery for Rockfort Fosgate. The only difference is they slap a different product sticker on the batter before it leaves the warehouse. I purchased one without the sticker that had a scratch on it for $40 compared to the retail price of $149. There are several isolators that can be used but the one I am using is the PAC isolator http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...&category=67771 . I am running a combined 3600 watts in my vehicle at full load and this setup has saved me a lot of gas money since I can leave stuff running without cranking my vehicle and I don't have to turn everything on and off everytime I get out of the vehicle. The battery just charges off the altenator and wont allow your cranking battery to go dead.

The biggest problem with running a second battery and all the electrical components is the strain it puts on the altenator. If you have an older car (especially GM) then I would highly suggest purchasing a high output altenator or having your old one beefed up. It would be a little more $$ but would actually save you money in the long run and it would be WELL worth it if it saves you from being stuck on the side of the road.

The 750 watt invertors from Wal-Mart actually only put out a small fraction of what they are rated at. I have a 2400 watt invertor and I charge my camcorder batteries, scanner, two way radios, playstation 2, laptop and use it for many other things along the way and never have to worry about it overheating or not delivering the needed power. I have 2 guage power and ground wire running directly off the battery and the price difference between the two invertors were about $50. I have a ton of stuff in my truck and if IMO the best investment was the battery, isolator and invertor since it protects and powers all of my expensive goodies. It all works as a system and the best component is only as good as the weakest link.

 

[Tom Burgess]

We use a simular system. Went to the local radio shop and got the iso switch. paid abot $70 for a good one. Added a 1000 cold cranking amp battery under the hood and ran large wire back to a homemade power center. We have 2 800 watt coleman inverters 2 ham radios ,3 laptop computers, printer,2 light bars,and 4 way flasher system that does not tieup the brakelights and a wireless cell phone router. Useing everything can run 30 min. without starting the van or 3 or more hours when not useing the lightbars. Pics can be seen at www.wxtech.com and click on the pic of the van to see the layout. The equipment in the front runs off a seperate system

 

[J West]

Thanks for the suggestions. We might end up just getting the isolator and second battery because we could use it anyway.

We are running a 750 watt inverter hardwired to the main fuse terminal box under the dash with heavy gauge wire (the closest to the battery we can get without poking another hole in the firewall). Off of the inverter, we have a surge protector power strip that all of the sensitive electronics plug into (laptops, routers, camera chargers). I've tried plugging the UPS into both the inverter and the power strip, and both result in the alarm. All the UPS really needs to support is the one router, since the laptops won't turn off when they lose AC power momentarily.

I've been running a setup like this for the past four seasons and the only drawback is that it wears my battery out faster. After about a year, the battery won't hold a charge when the car is left sitting for more than a day or so, requiring the use of the jumper pack. But, a new battery only costs $40 so it's not a big issue to replace it every year.
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What vehicle is this in? There are very few autos or light trucks that have enough spare infrastructure to support the added electrical load that most of us impose upon them. I'm not an expert by any stretch, but here are a few educated thoughts from working with communications and emergency equipment installations...

The only way to go is a dedicated power run from the battery, thru a suitable fuse and/or manual reset circuit breaker near the battery, back into the vehicle where the equipment is located. In your particular case, you should be running a 6 gauge cable (minimum) into the trunk or rear cargo area, where you can split it out thru a fused distribution panel. I also second the recommendation to upgrade the alternator, as most vehicle electrical systems are barely adequate for the OEM systems. I've found that GM electrical systems are very poor, with Ford and Mopar slightly better. I don't have enough experience with imports to make an educated comment.

For the gadget loaded installs around, a second battery with an isolator is a great idea. This allows the user to power the lights, radios, computers etc. with the secondary battery and never run the risk of overloading the primary OEM system or causing the primary battery to fail or die at the worst time.

As for batteries, Optima is the way to fly...they are about $120 (with exchange) at most decent places and are a much more robust battery than most, which means they take more abuse and higher run loads over time. It's more expensive at first, but they pay for themselves after a year or two.

 

[Dan Robinson]

The vehicle is a 2005 Ford. The inverter is direct-wired to the main terminal/fuse box under the dash with heavy-gauge wire. This fuse panel is then connected to the main fuse panel under the hood, which is hooked directly to the battery. A large fuse in the main panel protects the dash fusebox (I know this because I accidentally let the two leads to the inverter touch momentarily during the install, blowing the fuse up front).

The firewall in this car is so sealed up and reinforced that there is no room to put two even small-gauge wires through existing wire passageways. Drilling through didn't seem like a good idea, and my only other option was to run the wires on the outside of the car to get to the battery (bad idea).

Although we have a myriad amount of equipment wired in, I would never run all of it together at the same time. I doubt the alternator could sustain that abuse for very long. However, we can comfortably run the 2 laptops, and other small low-wattage accessories (battery chargers, LCD screens etc) with no problems.