# genius's help



## lou-ace (Jul 21, 2009)

Help geniuses!! Surely someone has come up with a cheep amp counter in truly DIY spirit. The one spec. that I truly have no idea is my rigs electrical usage. Now I did a SWAG (scientific wild ass guess) estimation based on miles used divided by kwts to recharge my pack, kind of like refilling your gas tank to figure gas mileage, i.e. 10 mi @ 3kwt = 333kwthr/mi but I would really like/need to track my actual usage. Now I know that I could spend a lot of money on one of the vendors systems but camon now isn’t there some way in truly DIY spirit of using maybe a house meter, or some low voltage counter off of my 50mv ampmeter shunt? You guys have come up with some pretty clever stuff so a simple amp counter shouldn’t be too hard. Question #2 I think that I’ve become pretty good at estimating current draw on the fly. If I’m drawing 200 amps pulling 110 volts under way doesn’t that mean that I’m pulling 22 kwts from my pack? I think that it’s interesting that I’ll peak the ampmeter ( 500 amps) on start up, but the pack will pretty well settle down to 25-30 kwt under constant load ( on a 27kwt system that’s about 1c eh? Ok guts come through on the ampmeter/counter for me now thanks Lou-ace.


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## Ziggythewiz (May 16, 2010)

How accurate do you need? And how cheap? As you mentioned, you can see for yourself how much you're pulling, assuming that's accurate. You should be able to figure out how much power you need to get up to speed (you can also just calculate that based on weight etc) and add in what you pull while cruising.

or just save your lunch monies for a month and get a JLD404; great buy at just $70.


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## Woodsmith (Jun 5, 2008)

How about the Cycle Analyst?

Originally designed for Ebikes but they have a high current version, up to 800A, to use in cars. They also have a data logger to record data over time to download later.

I have just bought one for my tractor and will be looking at a second one, with data logger, to convert into a test instrument.


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## lou-ace (Jul 21, 2009)

sounds like a real possibility Ziggy do you have a link or buyer for the jpl gadget, I can't seem t obe able to find it for under $200. And Woody the bike unit looks interesting. how much did you pay and do you think that I can use the device off of the same shunt that I'm now using for my onboard ampmeter? thanks


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## Ziggythewiz (May 16, 2010)

http://www.lightobject.com/Programmable-Digital-AH-meter-Ideal-for-battery-monitoring-P278.aspx

Got mine last week, they also have the extras if you need/want them. shipping was $10

EPS-1212CSW2 1212CS DC-DC 12V (2Watt) Isolated Power Module. Ideal for 12V system 1 $8.50 
ETC-JLD404AH-B Programmable Digital AH meter. Ideal for battery monitoring 1 $69.00 
ES-500A 500A 75mV DC Shunt 1 $16.50


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## Woodsmith (Jun 5, 2008)

lou-ace said:


> Woody the bike unit looks interesting. how much did you pay and do you think that I can use the device off of the same shunt that I'm now using for my onboard ampmeter? thanks


The Cycle Analyst is priced at $130 with a shunt at $18 in their store page.

I got mine in our classifieds ads for $100 but will be getting an additional one in due course.

Whether it will work with your shunt will depend on where and what size your shunt is. The CA shunt is 0.25mOhm and goes on the battery negative return as it is also part of the power supply to the CA.

When my one arrives I will do a write up of its installation on my tractor thread.


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## DIYguy (Sep 18, 2008)

Woodsmith said:


> How about the Cycle Analyst?
> 
> Originally designed for Ebikes but they have a high current version, up to 800A, to use in cars. They also have a data logger to record data over time to download later.
> 
> I have just bought one for my tractor and will be looking at a second one, with data logger, to convert into a test instrument.


Hey Woody. Are they really only rated for 800 amps? (thats an honest question, not sarcasm) cause I've had mine read out over 1200 amps.  I pushed Jason to make the higher voltage version, way back at the time was 250 volts I think. Is it still the spec?


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## Woodsmith (Jun 5, 2008)

DIYguy said:


> Hey Woody. Are they really only rated for 800 amps? (thats an honest question, not sarcasm) cause I've had mine read out over 1200 amps.  I pushed Jason to make the higher voltage version, way back at the time was 250 volts I think. Is it still the spec?


That's what the website implies. Given they were intended for electric bicycles it isn't bad.

There is a standard one with a shunt for 150A cont, 400A peak (that is on its way to me) and the high current one with a shunt for 300A cont, 800A peak (that I will get as a test instrument).

I don't know if a bigger shunt would change anything or if the software would need to be adjusted to read a higher range.

I am new to them myself.


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## lou-ace (Jul 21, 2009)

Ok Ziggy I like it and I ordered one. I'm going to try to hook it up to my existing 500amp shunt that runs my manual ampmeter. I think it's just magnet operated and shouldn't really affet the operation since it's going to be in parrallell. we'll see I think it will be obvious if it isn't workong right at which time I'll buy the other shunt...... happy to finally get a handle on what the rig is using, it might also be interesting to watch the charging cycle, one might be able to infer an effeciency curve with such data.... i.e if from a full charge one used x amps but had to charge y amps to get a full charge what is the effeciency.....eh? thanks again guys. I'll report back with my results.


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## Ziggythewiz (May 16, 2010)

Yeah, I got mine for a hybrid battery experiment I'll be doing, along with the assumption that switching to lithium someday will require an AH counter anyway. So far I've had it hooked up to my 12V system and was quite shocked at how much power I use with just the contactor on, and how little all my lights add on.

For the shunt, I think the parallel bit doesn't affect anything, but the voltage drop does. This thing (and I've heard most Chinese shunts) uses a 75 mv drop while most American shunts (like the one I already had in my car) use 50 mv, so if that's what you have the readings would be off by 50%...or 30% however the math works out...


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