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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV. |
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02-17-2013, 12:48 PM | #11 |
Gone Wild
Join Date: Sep 2012
Location: Savannah, GA
Posts: 2,760
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Re: ebay 500 amp ammeter inaccruate at part throttle
Oh that pesky decimal point, I thought I saw one in your post. I better get by glasses checked.
I'll keep looking for a 1.0uF cap. |
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02-17-2013, 12:52 PM | #12 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: ebay 500 amp ammeter inaccruate at part throttle
Give them a try, they might work.
I was just going bigger because the PWM frequency is relatively low. |
02-18-2013, 05:42 AM | #13 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: ebay 500 amp ammeter inaccruate at part throttle
I mounted mine between the forth and fifth battery (of eight) and mine seems to work. I had to build an isolated power supply, and also used twisted shielded cable.
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02-18-2013, 07:47 AM | #14 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: ebay 500 amp ammeter inaccruate at part throttle
Come to think of it, I'm pretty sure I used a shielded twisted pair cable when I jerry-rigged my ammeter to see if it was going to do what I wanted it to do.
I know I didn't ground the shield, but it was thin, black and flexable, and the only two conductor cables like that in my stash are mike cables. I powered it with a 9V battery for testing, but I'm planning on building a zener diode power supply and tapping into the switched battery pack voltage at the keyswitch when I permanently install it in the cart. After reading this thread, I think I'll toss in a few bypass capacitors. |
02-18-2013, 08:18 AM | #15 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: ebay 500 amp ammeter inaccruate at part throttle
I didn't ground the shield either. I still need to data-log and see how well it tracks with what my Alltrax, but the values seem to make sense, and it tracks well with my charger ammeter, and hits peaks of 400 amps on steep hills, and responds quickly under sudden acceleration.
I bought this for my isolated power supply, but reading the data sheet, it wanted to have more load than the ammeter drew, so I added a burden resister. |
02-18-2013, 09:07 AM | #16 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: ebay 500 amp ammeter inaccruate at part throttle
Here's my ammeter, shunt and power supply.
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02-18-2013, 09:30 AM | #17 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: ebay 500 amp ammeter inaccruate at part throttle
@ yurtle
Unfortunately, it might not work too well for my application. I building a 42V system and the Volt range on the 48V module is 43.2V to 52.8, so it might only work with my battery pack above 65% SoC and it might smoke if I turned on the key while charging. On the other hand, I doubt if the ammeter not functioning below 65% SoC would be a major issue for me and your 48V pack goes up to about 61V on charge. What pack voltage are you reading when you turn it on while batteries are on Charge? ----------- The zener power supplies I've built in the past are sort of hybrid units. I feed the base of a pass transistor with the zener circuit, so the fluctuation in zener current is only about 5% of the fluctuation of load current. Another option I've been kicking around is to power the ammeter from a small gel-cell or sealed lead-acid battery (2AH or so) mounted close to the meter and put a solar panel on the roof to keep it charged. |
02-18-2013, 09:33 AM | #18 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,087
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Re: ebay 500 amp ammeter inaccruate at part throttle
I think you need an isolated supply for that meter. You cannot power it from the battery pack. A 9V will last a long time though. I have several of these meters - use them to monitor the battery voltage in the radio system for my model airplanes. I think the 9V lasts a couple years for me.
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02-18-2013, 10:31 AM | #19 |
Gone Wild
Join Date: May 2012
Location: Rio Verde, Az
Posts: 7,087
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Re: ebay 500 amp ammeter inaccruate at part throttle
One thing I forgot to add here: Make sure that your sense wires from the shunt are at least twisted. Could also be shielded. This is a very small signal and there is lots of RFI generated by a golf cart controller when it's not at full throttle.
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02-18-2013, 11:14 AM | #20 | |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: ebay 500 amp ammeter inaccruate at part throttle
Quote:
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