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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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
100_0037.JPG (66.95 KiB) Viewed 942 times
I got these from Luna Cycle, but they seem to have dropped them. Look around and maybe you can find something simuilar.
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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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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by markz » Jan 02, 2018 11:28 pm

jonyjoe303 wrote:
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
Just what I am looking for. I was thinking Ardruino or Raspberry Pi but I hate programming. I really need to see what Ah I am getting when battery dies. I'd buy Justins if I were a rich man, but I aint.

Thanks for the link!

Here was the first one I found
http://www.instructables.com/id/DIY-Ard ... ster-V10-/
but Im going with $20 ebay find of yours!

I just have to ask, how are you liking your unit so far?
Is it worth it?
Is it accurate?

I have the same blue unit as you, but I think I fried mine :oops:

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by flippy » Jan 13, 2018 8:42 am

accuracy is "meh" at best. the shunts are usually of horrible quality.
just having a 10 led bar indicator is much simpler and arguably more accurate.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by trazor » Jan 17, 2018 8:06 pm

jonyjoe303 wrote:
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
Keep in mind that if you want to measure a nominal 72V Li-Ion the top voltage is 84V. I'm using this with "good enough" results:

https://es.aliexpress.com/store/product ... autifyAB=5

The "TK15 High Precision meter" looks very nice and would love to mount one in my e-moto but 80V max is probably a hard limit. Somebody can try it at 84V and tell the results? :)

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by dogman dan » Jan 18, 2018 8:19 am

Cheap blue watt meter, KISS.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by flippy » Jan 20, 2018 2:32 am

trazor wrote:
Jan 17, 2018 8:06 pm
jonyjoe303 wrote:
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
Keep in mind that if you want to measure a nominal 72V Li-Ion the top voltage is 84V. I'm using this with "good enough" results:

https://es.aliexpress.com/store/product ... autifyAB=5

The "TK15 High Precision meter" looks very nice and would love to mount one in my e-moto but 80V max is probably a hard limit. Somebody can try it at 84V and tell the results? :)
I have one of those on my charger. It is off by about 5%. The shunt quality just sucks. If you can order a separate more accurate shunt it might be fine.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by dogman dan » Jan 20, 2018 8:10 am

Duhh the cheap blue watt meter is for 60v max. I just realized you have more than that.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by jimbo69ny » Feb 14, 2018 10:04 am

Has anyone tried one of these before? https://www.ebay.com/itm/400V-300A-DC-D ... 1438.l2649

They come in all different variants. They seem nice for the money but I worry that they are cheap Chinese junk.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by flippy » Feb 15, 2018 5:42 am

jimbo69ny wrote:
Feb 14, 2018 10:04 am
Has anyone tried one of these before? https://www.ebay.com/itm/400V-300A-DC-D ... 1438.l2649

They come in all different variants. They seem nice for the money but I worry that they are cheap Chinese junk.
these are a different version of the power supply version of this unit. eevblog did a review of those units a while back and he liked it for the money.

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Re: Lithium Li-Ion 18650 capacity meter "Gas gauge"

Post by jimbo69ny » Feb 15, 2018 6:31 pm

Thats good news because I just bought one. :)

Should be here in 4 months

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