Battery concern.

Batteries, Chargers, and Battery Management Systems.
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Paderolis   100 W

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Battery concern.

Post by Paderolis » Jul 27 2017 2:32pm

Hello all! I have a question concerning a battery I just received from an eBay purchase. It is a 48V 12AH Lithium-ion battery. I didn't know until I got it that it is rated for a 500W MAX motor, as it wasn't in the description text. It is on the actual battery label, but you don't see that unless you zoom in on one of the photos. Honestly I never realized it mattered, I thought as long as the voltage rating was the same, you were good. Okay, so my system is a 48V 1000W system that I use 99% of the time as a pedalic only. My throttle is installed but not connected. If I use this battery, will I damage my motor? The battery? Both?

I have been using LIPO batteries until now, 3 18.5V 5,500mAH in series. Thank you for your advise.

http://www.ebay.com/itm/New-48V-12ah-El ... SwrhBZAjgU

zackclark70   100 W

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Re: Battery concern.

Post by zackclark70 » Jul 27 2017 5:56pm

potentially you can damage the battery or the BMS you could always get a 2nd battery and run in parallel for double the power change the BMS if the cells can take it

if your willing it might be worth talking a look at the internals and seeing what cells it has inside

GlowInTheDarkNinja   10 mW

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Re: Battery concern.

Post by GlowInTheDarkNinja » Jul 27 2017 6:22pm

I'm still very much a novice, but I'm a student and have been up and down the battery pages a few times getting ready for my build. I'm also planning to build with 18650 li ion...but here's what I'm thinking.

Basic lipo cells has 3.3v on the low end, 3.7v nominal, 4.2v full.
Based on that I assume there are roughly 12-14 cells in series.
Most lipo cells I've seen support at least 5C, at 12Ah this translates to 60A of current.

Now if you have a 1000w motor running on 48v. 1000w/48v= 20.8333A
Or at the lower end, lets say you only had 12cell in series at 3.3v per cell.
12s*3.3v=39.6v 1000w/39.6v=25.2525A

So from my understanding, ignoring wire and cell resistance, you should be able to safely use this battery because you will never be able to draw enough Amps to hurt the cells. You may want to try and identify the AWG of the wires on the battery in order to get a reasonable guess to what it was built to handle. If the wires can sustain 25A you should be safe.

Long story short I think ZachClark70 is correct. It seems like it was miss labeled or misread as 500W when it should be rated as a 500wh battery. 48v*12Ah= 576Wh

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Ypedal   100 GW

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Re: Battery concern.

Post by Ypedal » Jul 27 2017 6:30pm

Controllers have Max Amp ratings and that rating does not change according to the voltage you put it.. it's a fixed number... ie : 20 or 25 amp controller... or 35 etc...

example.. a 10 amp controller will draw 10 amps from either a 36v ( 360w )... or 48v ( 480w ) battery.
ES site status page:
http://www.ypedal.com/ES/ES.htm
----------------
http://www.ypedal.com

Paderolis   100 W

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Re: Battery concern.

Post by Paderolis » Jul 27 2017 6:59pm

Thank you for your input guys! I contacted the seller about it, he runs an electric bike shop in California. He said the battery will work fine, I just wont get as many miles between charges as a larger AH battery with the same voltage. The 500 Max motor thing threw me off. He did say he would try to update the description for the future.

zackclark70   100 W

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Re: Battery concern.

Post by zackclark70 » Jul 27 2017 9:54pm

Paderolis wrote:Thank you for your input guys! I contacted the seller about it, he runs an electric bike shop in California. He said the battery will work fine, I just wont get as many miles between charges as a larger AH battery with the same voltage. The 500 Max motor thing threw me off. He did say he would try to update the description for the future.
just be careful when you try it just to be on the safe side the BMS "should" cut it off if you go over speck but you never know for sure

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Sunder   100 MW

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Re: Battery concern.

Post by Sunder » Jul 27 2017 10:43pm

The battery will work - but the problem is, you don't know if you're going to get 3 years or 3 months out of it.

As another poster calculated, towards the end, you'll be pulling 2C. I've got some cells which I draw 10C from every day, and they've lasted years. I've got some cells that from the day I bought them, (and I knew they were cheap/bad), a 1C draw caused big voltage and within 30 cycles, the cells started puffing, despite no over-discharge.

If I were you, and it might not be possible on your bike, I would insert a voltameter into the circuit, then go to a small hill. Note the resting voltage of the bike, then go full throttle up the hill. Check what the lowest voltage you see is. If it drops much more than 10-15%, your battery is going to have a fairly short life.
eBike: Q100H on 16S with Phaserunner FOC Controller
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After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca

zackclark70   100 W

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Re: Battery concern.

Post by zackclark70 » Jul 27 2017 10:53pm

Sunder wrote:The battery will work - but the problem is, you don't know if you're going to get 3 years or 3 months out of it.

As another poster calculated, towards the end, you'll be pulling 2C. I've got some cells which I draw 10C from every day, and they've lasted years. I've got some cells that from the day I bought them, (and I knew they were cheap/bad), a 1C draw caused big voltage and within 30 cycles, the cells started puffing, despite no over-discharge.

If I were you, and it might not be possible on your bike, I would insert a voltameter into the circuit, then go to a small hill. Note the resting voltage of the bike, then go full throttle up the hill. Check what the lowest voltage you see is. If it drops much more than 10-15%, your battery is going to have a fairly short life.
just so anyone that reads this know this only works well for low power bikes as big bikes at high powers will have a bit more sag

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Sunder   100 MW

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Re: Battery concern.

Post by Sunder » Jul 27 2017 11:15pm

Yeah, not sure I 100% agree with that...

Sure, high powered bikes will pull the same battery down a lot more than a low powered bike. That part I agree with.

BUT, the cathode erosion occurs at an accelerated rate when high discharge rates are used. The cathode doesn't pop out and check whether you have a high powered bike or low powered bike. If the rate of discharge is faster than the cathode is designed for, it will wear prematurely.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: 5.5kw On-grid solar with battery backup coming soon!

After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca

zackclark70   100 W

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Re: Battery concern.

Post by zackclark70 » Jul 27 2017 11:47pm

Sunder wrote:Yeah, not sure I 100% agree with that...

Sure, high powered bikes will pull the same battery down a lot more than a low powered bike. That part I agree with.

BUT, the cathode erosion occurs at an accelerated rate when high discharge rates are used. The cathode doesn't pop out and check whether you have a high powered bike or low powered bike. If the rate of discharge is faster than the cathode is designed for, it will wear prematurely.
most of us with high power bikes will see 10% drops on big hills but its only for a few a sec ( i am pulling 20c peaks on my offroad bike and thats with a very good battery and i still see 10-15% v drop at times depending on what the SOC is but i am pushing the power far more than 90% of the people on here )

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Sunder   100 MW

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Re: Battery concern.

Post by Sunder » Jul 27 2017 11:58pm

zackclark70 wrote: most of us with high power bikes will see 10% drops on big hills but its only for a few a sec ( i am pulling 20c peaks on my offroad bike and thats with a very good battery and i still see 10-15% v drop at times depending on what the SOC is but i am pushing the power far more than 90% of the people on here )
From what you described, I would say your battery is fine, but close to the limits of design for a full life. It doesn't really fall into the case that I described (10-15% on a small hill, you're on the lower end of that on a big hill.).

But you do bring up a good point, which I hesitated to because I didn't want to confuse the matter. SOC does matter, because internal resistance is dependant on SOC. It's less noticeable in LiIon/LiPo, because the discharge curve is more of an even slope, but doing the test on a full LiFePo4, where there's like 5% capacity between 3.65v and 3.3v (10% voltage drop right there), would give you erroneous results.

Either way, there's no "magical line" where your battery will get a long and full life on one side and will die a short and fiery death on the other. But from my reading and personal experience, 10-15% sag is where things start to get concerning.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: 5.5kw On-grid solar with battery backup coming soon!

After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca

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dogman dan   100 GW

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Re: Battery concern.

Post by dogman dan » Jul 28 2017 5:59am

It will work, but likely not last 4 years. The more you pedal, or rather, the more you limit the amps on the steepest hills, and on starts, the more the battery will be under 500w continuous. and like he said,, when its nearing empty, that's when to really slow down and go easy on it.

Into some wind, up slight hills, etc, 20 mph will take about 600w. That is about 12.5 amps, or 1c more or less for your battery. I see no problem with you riding your bike 20 mph all you want.

It will draw close to double that at 30 mph,, into some wind, up a slight hill. Wind and your back, or downhill, haul ass all you want.

One thing you can do that will help you monitor how your battery is doing is install a digital voltmeter, or watt meter on the bike. You will then be able to judge how hard your battery is being run by the sag under load. 2v sag is excellent, but you won't see that. 4-6v sag under heavy load is what I think you will see. Try to ride so at cruise, you have 2-4v of sag.

The other way to judge it, is even simpler. If after a ride, your battery is really hot, you pulled too hard on it. Sure, its within factory spec, but it did not like it. The battery will always get very warm. I mean it gets so hot its uncomfortable to hold it in a bare hand. try to avoid that.

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