Lithium Li-Ion 18650 capacity meter "Gas gauge"

Batteries, Chargers, and Battery Management Systems.
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llile
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Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by llile » Nov 20, 2017 3:31 pm

Is there a commercial meter than can be used as a capacity gauge for Li-Ion cells? Is there one that can work at higher numbers of series cells, such as for a 72V pack? or am I getting out the Arduinoes again? And what the hell is the proper plural for Arduino? Is it Arduineau?

Obviously the cell voltages for a pack are hard to measure, as the voltage slope is pretty flat, and the voltage would drop under load, complicating the "gas gauge" measurement. I can usually calculate remaining capacity kind of in my head looking at the voltmeter on my cycle analyst, (not to mention read the KWH measurement) however I'm working on a non-bicycle application, where a cycle analyst is total overkill. I just need to know if my batt is fully charged, or state-of-discharge in rough increments. I'd be OK with having to idle the load to get a real number. A % display would be nice, however not absolutely necessary. It would also be nice if it went into sleep mode or used very little juice when things are idle. I've been googling and come up only with meters that can handle 4-7S cells.
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motomech
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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by motomech » Nov 20, 2017 4:14 pm

You have already learned to interpolate a Voltmeter, why not just add a small one?
I use a LCD meter that only draws Miliamps when connected an the drain is so little that even after days, the battery Voltage doesn't change. The back-lighting has to be activated and times out, so that is not a factor. Here's a pr.(I have 2 batt. packs);
100_0037.JPG
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I got these from Luna Cycle, but they seem to have dropped them. Look around and maybe you can find something simuilar.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, 2.4 Holly Rollers run ghetto tubeless. 25 mph. Mean Well HLG-320H-48A
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llile
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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by llile » Nov 20, 2017 4:48 pm

motomech wrote:
Nov 20, 2017 4:14 pm
You have already learned to interpolate a Voltmeter, why not just add a small one?

I got these from Luna Cycle, but they seem to have dropped them. Look around and maybe you can find something simuilar.
What? You want me to make this easy?
Also, this particular batt might be used by the spouse, who although she has a PHD, may not be able to interpolate in her head. If I tackle the project, it may be a range hack for an electric car. Worth putting some effort into. But I'll keep the K.I.S.S. approach in mind!
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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by jonyjoe303 » Nov 21, 2017 10:06 pm

this measures 8 to 80 volts, tells you everything you want to know on the screen. I use it on my 110 ah lifepo4. You program the battery amp hour and the meter keeps track of amps going in/out of battery pack. Cost me 22 dollar on ebay. In the picture its shown next to dc wattmeter, the readings on both are nearly the same. It even tells you how time you have left as you deplete the battery.

TK15 High Precision LiFePO/Lithium/Lead Acid Battery Tester Coulomb Counter 50A
a coulometer.jpg
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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by changeissimple » Nov 22, 2017 3:26 pm

I am browsing this thread looking for a bit of information on my ebike battery range. I went out for a great ride after work, running errands all over town in my newly built e-moped. It is 48v 26.1AH battery and a 1500 watt hub motor. By my calculations I should be able to run about 20 miles (possibly more). I have a cycle analyst 2.4 DP on the bike. Last night was my first really extended ride and it seemed to be I was using about 1ah per mile and had gone about 9 miles and the Cycle analyst was saying I have used 9.5ah. BUT the battery gauge indicator graphic in the top left of the Cycle Analyst was showing i was very low, so I headed for home. I wondered if the number of the AH indicator is more accurate than the battery graphic gauge? Also, how drastically will cold temperatures affect the ride distance? In my electric car it really shortens the ride in the cold. I live North of Boston so we deal with sub 32F regularly this time of year. I attached a photo of the bike I built, it is fairly light maybe 75 pounds and I weigh only 145.

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