inverter watts

[craigco]

Looking to get an inverter to charge 18 volt batteries in my truck. How many watts do I need. It 18 volt Dewalt.
 

[LJD]

A small 200W-400W inverter that plugs into your cigarette lighter is plenty big enough. The quality of the AC power, not the watts - is the issue. It will work but will not charge as fast as when plugged into AC. The early 18 volt chargers were approx. 30% slower when used with a modified-wave inverter. The newest chargers handle the "square wave" better and can charge 80% to 100% as fast as when on AC. Much depends on the quality of the inverter and the voltage peaks at the tops and bottoms of the waves. Grid power makes 170 volts. Many inverters only make 150 volts at the peaks and dips.

The best way to do it is to buy a DC charger for your gun. Plugs into the cigarette lighter. Just a DC to DC charger. I have one for my Ryobi 18 volt tools.

Dewalt DC9319 DC to DC charger is $75-$80.
 

[John T]

In line with what JD noted, if you first use a 12 VDC to 120 VAC INVERTER and then plug your DeWalt 120 VAC to 18 VDC Charger, YOU HAVE WASTED SOME ENERGY in the form of heat losses since none of those devices are 100% efficient. But ifffffffffffff you can buy a 12 VDC to 18 VDC charger (it still has to have some inefficient electronics for 12/18 conversion) you would be better off as far as saving the trucks battery energy...

So ifffffffff they make a plug into cigarette outlet charger to charge 18 volt batteries (still needs some electronics to do that) ??????????????????? Id go that route, however, if not or exepesive or hard to find, its true a cheap plug in Inverter in the 200 to 400 watt range (around $40 or so) would be quick n simple into which you plug your regular DeWalt 120/18 charger...........Plus the Inverter is there handy to charge youre regular 120 VAC cell phone and laptop etc if you dont have a 12 volt charger device?????

Lots of choices, do some shopping and consider youre needs, heck the 400 watt 12 VDC/120 VAC regular plug in Inverter would be simple n handy to have, its what I use in the RV so I can watch TV or charge my devices etc etc when Im dry camping with no hook ups

John T THANKS VETERANS
 

[LJD]

Inverters really are a "crap shoot" unless high-end and power certified. My experience with charging 18 volt power tools with inverters has been as already stated. No major issues with any of the small cheap inverters. Just a little slower. Same for cell phones.

But . . here's one for you. I recently got a so-called Ramsond Sunray "true sine wave" 3000 watt more-pricey inverter. I had to in order to pass building inspecting since a mod-wave will not run smoke alarms and GFIC outlets properly. An inverter that can be hard-wired is also necessary for inspection. Guess what? It will NOT run my Dewalt or Ryobi 18 volt chargers. Yet, all my cheap mod-wave inverters do the job just fine. If just goes to show that very few of them make a true sine-wave unless you spend $1000s on a unit. I checked AC output with a RMS volt meter and this "true sine-wave" unit is only putting out 109 volts AC. All my other inverters put out 114-120 VAC when read with RMS. If read with a non RMS el-cheapo voltmeter, the mod-waves only read around 85 volts (but work fine).
 

[John T]

I hear and believe what youre saying, I'm just too rusty on "electronics" to have much input as I was more into Secondary AC Distribution in my later work years and I stopped that back in 91. All I know is the 400 watt Cobra and other off the shelf cheaper brands in the RV work good enough to charge my cell phone, run a small TV and run the laptop and thats all I need.

As always, fun sparky chattin with ya...

John T
 

[LJD]

There IS no way to keep up unless you actually use these different units. You certainly cannot tell by reading their advertised specs.

Yes, I've got many cheap Cobra, Vectors, Harbor Freight, Duracell, AIMs, etc. and all work fine for most things. None will run a GFIC outlet of a smoke alarm though. That's an issue when wiring a low voltage house and trying to pass inspection.

So, I HAD to buy this $800 "true sine wave" inverter to pass inspection. My 4000 watt hard-wired Trace/Xantrex would not pass since it cannot run the smoke alarms and GFICs. Note that this new unit runs the required stuff perfectly but will NOT run an 18 volt charger. It comes on but never shuts off. I left one on for two full days. Then stuck it on a cheap mod-wave Vector and it got done in 15 minutes.
 

[big jt]

I am with LJD.

If all you want to do is charge your Dewalt batteries just get a cigarette charger. You may be able to do better on price on ebay, etc.

I attached a link to a fleabay auction for $71 after shipping but does include a battery.

jt
Untitled URL Link

 

[Steven-Id]

I have one of the cigarette lighter chargers for my 18v dewalts in my work truck and they work slick. They will recharge my batteries in about 35 minutes.


Steven
 

[John T]

Thanks for the Link, now I know they do indeed make them and I may just get on for the RV. Yepper a search on Flea bay will find aobut anything lol

John T
 

[Tramway Guy]

The Dewalt chargers work just fine on an inverter plugged into the power outlet of a vehicle...
 

[Jon Hagen]

All this talk of solid state inverters sometimes not being quite right for some battery chargers, got me thinking about a device I saw 20-30 years ago.

At a construction equippment shop, they had a little motor-generator unit that had a 12VDC motor and a 120VAC generator combined in the same case. I seem to remember it being about 5 inch diameter and 2 ft long, DC stud terminals at one end and a 120V duplex at the other end. A yellow tube laying on it's side on 4 little legs.
The thing being a generator, should have produced "real" sine wave power ? I don't know if the thing had any sort of speed contro; on the DC motor to try to maintain correct 60 cycle speed.
A quick Google search does not show anything like that avalible now. Anyone know if they are still being made ??