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Long story short: i have a 120v charger but want to charge off 12v. Dewalt makes one for a $109. 'uhNo

Any Blue smoke Phd's know how to convert a 120v charger to run off 12volts? I've seen a few youtubes converting 120v to 220v but yet to run into one that drops the zero.
Is this even possible? If so, how?
 

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Long story short: i have a 120v charger but want to charge off 12v. Dewalt makes one for a $109. <img src="http://www.mysmiley.net/imgs/smile/confused/confused0086.gif" border="0" alt="" title="confused0086" class="inlineimg" />

Any Blue smoke Phd's know how to convert a 120v charger to run off 12volts? I've seen a few youtubes converting 120v to 220v but yet to run into one that drops the zero.
Is this even possible? If so, how?
I just plug mine into the 120v outlet at the dash. On previous vehicles i used a 120v inverter.
 

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It may be possible but with the smart circuit boards inside to keep the lithium battery from turning into a blow torch, probably not recommended.
 

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You need a good sized converter to handle the beginning 'hot' charge cycle.
1500-2000w sine wave, wired @ the battery (no cig lighter). Downfall is, it's about as much or more $$ than what DW is offering.

But you can use it for other things, justify the expense.
 

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Discussion Starter #5
You need a good sized converter to handle the beginning 'hot' charge cycle.
1500-2000w sine wave, wired @ the battery (no cig lighter). Downfall is, it's about as much or more $$ than what DW is offering.

But you can use it for other things, justify the expense.
i've been running my 120v charger off a 400-450w inverter. Its wired directly to my battery bank.
Seems to be working fine although not sure if i'm doing any long-term damage.

Thoughts?
 

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i've been running my 120v charger off a 400-450w inverter. Its wired directly to my battery bank.
Seems to be working fine although not sure if i'm doing any long-term damage.

Thoughts?
Does it have an on-off switch? inverters draw a small amount of current even when not in use.
 

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Long story short: i have a 120v charger but want to charge off 12v. Dewalt makes one for a $109. 'uhNo

Any Blue smoke Phd's know how to convert a 120v charger to run off 12volts? I've seen a few youtubes converting 120v to 220v but yet to run into one that drops the zero.
Is this even possible? If so, how?

you need an inverter to convert 12V DC to 120V AC. When going from 120V AC to 240V AC all you need is a simple 2:1 transformer to step up the voltage, when converting DC to AC you need to create a sine wave from DC to get AC current so its not as simple as stepping AC up and down. You cannot run DC through a transformer since there is no chance in voltage to create a change in field.
 

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i've been running my 120v charger off a 400-450w inverter. Its wired directly to my battery bank.
Seems to be working fine although not sure if i'm doing any long-term damage.

Thoughts?
You're totally fine. That's like 35 amps at 12 VDC; not even close to a concern with a 150A alternator (note, though, that alternators generally cannot put out their rated current at idle). However, I would definitely not draw that amount of current unless the truck is running.

I routinely draw 2kw to 3kw from my inverter for short periods and 1.5kw or so continuously when covering large distances with my travel trailer; see the link in my signature for details. I've had absolutely no issues and that's over 10k+ miles pulling that amount of current (I have dual alternators, 150A and 220A).

Edit: Not only are you fine at 450w, but you're definitely fine if all you're running is the battery charger because the power draw is probably like a tenth of that wattage. I recommend a "kill-a-watt" meter or something similar to measure it. Note that I run my single-battery Dewalt charger off the in-dash inverter in my truck (150w capacity) and it has never created a problem.
 

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You need a good sized converter to handle the beginning 'hot' charge cycle.
1500-2000w sine wave, wired @ the battery (no cig lighter). Downfall is, it's about as much or more $$ than what DW is offering.

But you can use it for other things, justify the expense.
Nah. Take at least one zero off those numbers.

I run my single-battery Dewalt charger off the in-dash inverter in my truck that supposedly has a 150w capacity; no issues at all.

I run my four-battery charger off a regular 15A/120VAC circuit at home, and on the same circuit I have a big freezer and a bunch of other crap. Never tripped the breaker.

The maximum rate of discharge on these batteries is in the 300-400 watt range, and the charging rates are probably an order of magnitude less than that.
 

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Also, if you are worried about the current, there are aftermarket alternators up to 500 amps available should you want to weld straight off the running truck (that was a joke please dont actually weld with your alternator).
 

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Also, if you are worried about the current, there are aftermarket alternators up to 500 amps available should you want to weld straight off the running truck (that was a joke please dont actually weld with your alternator).
Take the batteries out of the truck and wire them in series first:

 

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I have welded like that.... it does not work well, but it does work well enough if your in a situation where that's all you have.
 

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Discussion Starter #13
.

Edit: Not only are you fine at 450w, but you're definitely fine if all you're running is the battery charger because the power draw is probably like a tenth of that wattage. I recommend a "kill-a-watt" meter or something similar to measure it. Note that I run my single-battery Dewalt charger off the in-dash inverter in my truck (150w capacity) and it has never created a problem.
I have a kill-a-watt but my concern is around peak demand, something a kill-a-watt (or at least mine which is ~8yo) does not measure.
Handy device for sizing an inverter, though.
 

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Discussion Starter #14

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my concern is around peak demand,
This ^ is what melted my 450w inverter....after plugging it in, thought it was all fine and walked away. Then the charger kicked it up in overdrive to another level, and when I stepped back over to the truck....white smoke from the fans and it was screaming it's little "I'm Dying!" whine.

Fried.
 

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I have a kill-a-watt but my concern is around peak demand, something a kill-a-watt (or at least mine which is ~8yo) does not measure.
Handy device for sizing an inverter, though.
What do you mean by "peak demand"? It's a battery charger; current draw will vary over the charging cycle but it will be relatively constant over intervals on the order of minutes, so yes, a kill-a-watt will certainly measure that. The meter will show you the instantaneous power and current.

A battery charger is not likely to have any significant inductance or capacitance, so its power factor should be very close to unity (i.e., "1"), so real/apparent power or current aren't a serious consideration here either. Even if they were, the amount of current that a Dewalt charger draws is so small that even at a terrible power factor of around 0.5 it's just not going to matter.
 

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This ^ is what melted my 450w inverter....after plugging it in, thought it was all fine and walked away. Then the charger kicked it up in overdrive to another level, and when I stepped back over to the truck....white smoke from the fans and it was screaming it's little "I'm Dying!" whine.

Fried.
What kind of charger was this, and are you sure the charger itself (or the battery) didn't fail? The little single-battery Dewalt chargers are definitely fine on small inverters; i.e. 150 watts or so. Even with a crappy waveform (the waveform coming off the in-dash inverter in my truck looks more like a neural spike train than a sine wave; it's disgusting).

I'll check the current draw on my charger when I get to my truck later just to make sure I'm not way off on this.
 

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It was a DW driver saw combo box. In testing later, it would start up low, then a few minutes later I could hear a 'click' and the hum would increase (this, plugged into AC), as it went into fast charge mode.

Maybe their new chargers run more low steady.
 

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I didnt watch this but... this just makes me realize that the money spent on a good welding machine isnt for the machine... its a life insurance policy in which you get a free welder. :grin2:
24V DC is very unlikely to hurt you. There's is not sufficient voltage drive a lethal current through your skin. I say very unlikely because there are situations, like if you punctured your skin on a hot wire, or were soaked in salt water or something, but you would generally not be in harms way with that system sort of the batteries exploding from the current draw.



As for inverters, demand, and such. An electronic device produces a load. the current drawn by a device creates the load based on the input voltage of the system and the resistance the device has within the circuit.

For example. If you have a 1 ohm load, maybe a really high power light bulb, that would draw (12V/1R)=12A. no matter how many batteries you connect, so long as the voltage is the same, and the resistance is the same, the load will be the same. You cannot force more power into a device than the internal resistance of that device will allow to flow through it. This is not just a recommendation, it is a fundamental law of physics. If your device draws 120 watts (120W/12V)=10A it will require 10 amps from the charging system. If you have an inverter that is rated to output 150 watts, and you connect a load that draws 120 watts, there is no situation without hardware failure that would overload the 150 watt inverter. The inverter only needs to be rated for the power being consumed.

Where you may get into issues is with devices like amplifiers, where they are rated in the output power, not the input power. So a AB amplifier that is say 50% efficient, may output 500 watts, but draws 1000 watts and released 500 watts of heat. In this case you could overload an inverter, but a battery charger is unlikely to have sufficient internal thermal losses to make a difference.
 

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Where you may get into issues is with devices like amplifiers, where they are rated in the output power, not the input power. So a AB amplifier that is say 50% efficient, may output 500 watts, but draws 1000 watts and released 500 watts of heat. In this case you could overload an inverter, but a battery charger is unlikely to have sufficient internal thermal losses to make a difference.
Anything with a power factor significantly less than unity can wreak havoc on an inverter. I'm dealing with this right now with my 15k BTU/hr AC. It seems like the circuit is actually carrying the current associated with the "apparent" power and the inverter is dissipating the difference between real and apparent power as heat, causing way more draw on the electrical system than one would expect from the ~1500 watt (real) air conditioner. I am going to try one of those crappy Chinese power factor correction capacitors and see if it has any effect. Hopefully I don't set fire to my truck.
 
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