# Kill-A-Watt Meter Modification?



## ithinkidontknow (May 14, 2009)

I just got my Kill-A-Watt meter to measure the kWh efficiency during charging but this got me thinking. 

Would it be possible to rewire or modify the meter as it currently exists in order to have it be able to measure DC current, voltage, kWh? For those of you who are unfamiliar, the Kill-A-Watt meter measures your AC outlet energy consumption through a voltage, current, frequency, wattage, and kWh measurement. 

I realize that this system is set up for an AC system but also cant imagine that designing a system similar to this for DC would look much different. Maybe someone who actually knows something about electronics could prove me right or wrong. 

I think that this could have an amazing amount of use for smaller EV projects to make measurements. I say smaller EV projects because it can only handle around 15 amps according to the their website. 

Anyway, if anyone would like to help me work on making this possible for DC applications, please respond. Also, if anyone would like pictures of what the electronics look like inside, I can take fairly high resolution pictures. 

Thanks


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## Amberwolf (May 29, 2009)

I dont' know if anyone has done that yet, but there are some modifications including adding wifi to it (to send it's data remotely to your computer) at the ladyada.net forums. Since there are several versions of each model of the KaW, at least portions of it have been figured out several times, so asking there might get you even more info.
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Peak Towers Condo Pattaya


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## JRP3 (Mar 7, 2008)

Otmar took one apart:
http://www.cafeelectric.com/killawatt/index.php


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## Zemmo (Sep 13, 2007)

I've been using these meters for a while to measure my KWh on charging. It does a pretty good job. But it can't handle 15 amps constantly. I have burnt up 2 of these so far. I can only get a constant 13.5 amps (still gets warm and some plastic getting brittle but still fine). Anything higher than that the unit starts to over heat and the plastic starts to melt or become brittle because of heating up and then cooling off. I've contacted the company that makes them to complain about it not actually being able to handle 15 amps and they just gave the standard reply message of send it back for a replacement. I haven't found another product that will do the same thing at a 20 amp ratting for a reasonable price. If you do find one, please let us know!


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## ithinkidontknow (May 14, 2009)

While the links are appreciated and a little bit helpful, this still doesn't really answer a lot of the questions I have. 

Does anyone know if the electronics would even be able to monitor DC? From the Cafe Electric website I see that "It seems that R17 is the current measuring shunt, U1 amplifies it for the processor." I don't know too much about electronics but it seems that this is a generic setup that could report DC.

I have tried hooking up 27v DC through the meter in order to successfully power a small motor but the meter screen will not boot up. Does anyone know why this is? Is there some part of the circuit that will not work unless it has sufficient current? 

Also, 13.5 amps is not really ideal for a maximum load so I am now looking at what sort of modifications it would take to increase the maximum amount of current. Question though, what sort of parts on the board would be the limiting factors for how much current the board could take? Generally, better cooling ought to help but it seems like getting beefier components would help more.


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## Amberwolf (May 29, 2009)

Anything can *measure* DC, but the microprocessor would likely have to be reprogrammed to display the DC measurement instead of the AC one it does now. That's why I recommended checking with the ladyada.net forum.

EDIT: also, the device is powered by the wall-level ac power that comes in, if I understand it correctly. Again, modifications you would have to make for it.
________
Laguna Beach Resort Jomtien


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## ithinkidontknow (May 14, 2009)

I will check over on those forums and put up a post, hopefully I can learn something useful, and when I do I will make sure to post them in this thread.


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## rfengineers (Jun 2, 2008)

Zemmo said:


> I've been using these meters for a while to measure my KWh on charging. It does a pretty good job. But it can't handle 15 amps constantly. I have burnt up 2 of these so far. I can only get a constant 13.5 amps (still gets warm and some plastic getting brittle but still fine). Anything higher than that the unit starts to over heat and the plastic starts to melt or become brittle because of heating up and then cooling off. I've contacted the company that makes them to complain about it not actually being able to handle 15 amps and they just gave the standard reply message of send it back for a replacement. I haven't found another product that will do the same thing at a 20 amp ratting for a reasonable price. If you do find one, please let us know!


I bought a meter and socket for about $55 (including shipping) It can handle 100 Amps at 240VAC. I mounted it on the wall of my carport and put my dedicated "EV charger AC outlet" underneath. I just note the reading every time I recharge the car.

Here is a similar (but not identical) meter from the guy I bought mine from:
Ebay Item number:180374028907

Edit:
Oh, here is the same meter I bought: Item number:180383353469


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## O'Zeeke (Mar 9, 2008)

rfengineers said:


> I bought a meter and socket for about $55 (including shipping) It can handle 100 Amps at 240VAC. I mounted it on the wall of my carport and put my dedicated "EV charger AC outlet" underneath. I just note the reading every time I recharge the car.


Joe, thanks for the ebay info, I just bought one myself.


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## Stunt Driver (May 14, 2009)

in other words you can use any power household meter, hopefully found at scrap If you can reset it - that's all that is needed. But how off this is - proper EV must have real BMS that will monitor DC current going to and from batteries.


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