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Fast charging current - your opinions please


RooMiniPro

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I have been enjoying the extra range I'm getting since I started using my portable charger with my NineBot One E+.  But stopping and waiting for 45 minutes to get an extra 10km is not always ideal.

I charge at 2 amps max (the same as the stock charger) on the portable system.  I want to go higher to save time but not beyond what the Ninebot battery will be comfortable with, without significantly reducing the battery's longevity.

What rate do you think I can charge this battery at? It's 15S2P, 320Wh.

I believe the cells are 3000mah but I'm not certain. Charging at 1C on a 2P pack would be 6 amps. I would be happy charging at 4 amps when I'm out and taking a break to top up. That would still only be 0.66C. I have RC Aircraft Lipos that I charge at 1.5C that are still going strong after 2-3 years and hundreds of cycles. 

What do you think in terms of battery health if I charge at 4 amps, or even 5 amps? Both still under 1C

Thanks

 

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14 minutes ago, RooMiniPro said:

I have been enjoying the extra range I'm getting since I started using my portable charger with my NineBot One E+.  But stopping and waiting for 45 minutes to get an extra 10km is not always ideal.

I charge at 2 amps max (the same as the stock charger) on the portable system.  I want to go higher to save time but not beyond what the Ninebot battery will be comfortable with, without significantly reducing the battery's longevity.

What rate do you think I can charge this battery at? It's 15S2P, 320Wh.

I believe the cells are 3000mah but I'm not certain. Charging at 1C on a 2P pack would be 6 amps. I would be happy charging at 4 amps when I'm out and taking a break to top up. That would still only be 0.66C. I have RC Aircraft Lipos that I charge at 1.5C that are still going strong after 2-3 years and hundreds of cycles. 

What do you think in terms of battery health if I charge at 4 amps, or even 5 amps? Both still under 1C

Thanks

Check the max amperage on the charger plug, if it's lower than what the 1C charge for the parallel packs would be, stay below that. For the GX16's used in most wheels, it's said to be 5A max, but Ninebot uses a Lemo-plug (or a clone of such)... I'd check to see if I can find a datasheet or any mentions of the amperage, but I don't know the exact model.  https://www.lemo.com/en

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20 minutes ago, esaj said:

Check the max amperage on the charger plug, if it's lower than what the 1C charge for the parallel packs would be, stay below that. For the GX16's used in most wheels, it's said to be 5A max, but Ninebot uses a Lemo-plug (or a clone of such)... I'd check to see if I can find a datasheet or any mentions of the amperage, but I don't know the exact model.  https://www.lemo.com/en

Thanks, yes that's a good idea. I don't know the model of the lemo plug either. I imagine it could handle 4 amps for 30 minutes though without melting. My real question is about the battery though. 

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18 minutes ago, RooMiniPro said:

Thanks, yes that's a good idea. I don't know the model of the lemo plug either. I imagine it could handle 4 amps for 30 minutes though without melting. My real question is about the battery though. 

Have you read through Cranium's 5A fast charging topic:

 

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From reading @Cranium's thread and speaking to him via pm it seems that the battery, connector and wiring can handle up to 5 amps with no issues. This is great news! I will be able to charge safely at 4.5 amps and dramatically shorten my charging breaks when out riding and getting low on power. 

Thanks to @Cranium and to @esaj for the help with this!

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I'm not sure where people are getting this 1C charge rate from, but the battery packs in question use Li-Ion batteries as as noted they are often made up of a number of 18650 cells.  A good quality battery such as the Panasonic/Sanyo GA has standard charge rate of 0.5C.  It is not actually recommended to exceed this.  

Another important thing is that temperature matters, so if one is recharging after riding the temperature could be quite high, and under these circumstances charge rate should be moderate.  It is not recommended to charger them above 45deg C.  

There are some variations of course, but not much, so if exceeding .5C then manufactures specifications should be consulted and temperature should be monitored.  

Have to run right now. have a great day!

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35 minutes ago, FreeRide said:

I'm not sure where people are getting this 1C charge rate from, but the battery packs in question use Li-Ion batteries as as noted they are often made up of a number of 18650 cells.  A good quality battery such as the Panasonic/Sanyo GA has standard charge rate of 0.5C.  It is not actually recommended to exceed this.  

Another important thing is that temperature matters, so if one is recharging after riding the temperature could be quite high, and under these circumstances charge rate should be moderate.  It is not recommended to charger them above 45deg C.  

There are some variations of course, but not much, so if exceeding .5C then manufactures specifications should be consulted and temperature should be monitored.  

Have to run right now. have a great day!

The battery cells in my Ninebot are LGDDBMG11865 which translates to LG 18650 2900mAH batteries (2850mAH nominal).  I was even able to put together a spec sheet from online (PDF found in post below).  

Normal charge current is 0.5C or 1.425mA.  Max charge current is 1.0C or 2.850mA.  Since the Ninebot has 2 cells in parallel, the normal charge rate is 2.85A and max charge rate is 5.7A.  This is from the manufacturer and is completely safe to do and thoroughly tested.  As noted in the PDF, the overcharge testing procedure actually cycles the battery for 7 hours at charge rate of 3C up to 4.2V then discharges at 570mA to 2.5V.  It passes if it doesn't blow up or catch fire.  

As you mentioned, temperature also matters.  Good operating practice would not be to charge on hot batteries.  The max charge temperature of these cells is 45°C or 113°F.  My batteries don't normally get that hot in normal riding even though my controller gets really hot.  And if you start charging with the batteries warm (45°C or lower), they will continue to cool during the charge cycle.  

So the way I see it, the only real consideration for charging at higher current is:  Are you willing to possibly shorten the life of the battery a little to charge faster?  Other than that everything else is the same.  For me the answer is YES.  I don't charge at a higher current all the time but there are times where it has been very convenient.

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4 hours ago, FreeRide said:

I'm not sure where people are getting this 1C charge rate from,

 

Generally from the cell manufacturers' specifications and from common knowledge that modern, good quality 18650 cells, as well as lithium polymer pouch cells, can charge at a rate of at least 1C without any concern.  Some cells can handle many times that. Charging at 0.5C should technically increase the useful charge cycle count.  I'll be charging my Ninebot battery at significantly less than 1C.  I am sure that if I tested this under scientific circumstances with regular, consistent discharge and charge rates at a constant temperature I would be able to see that a battery charged on the stock charger would at least somewhat out perform the 0.7C charged battery after several hundred charge cycles.  But for my every day use with so many variables like unpredictable and varying discharge rates, varying temperatures, varying amounts of stops and starts, I don't think I will notice any premature degradation when charging at 0.7 - 0.8C. 

With my Ninebot battery, what I am doing now is occasionally doing a partial charge at 4 to 4.5 amps, which for the 15S2P pack is about 0.7C.  I charge using the stock charger for the full balance charge at home.  But when I am out on a long ride and get low on power I use my portable battery powered charger to top up to about 95% before continuing on my way.  I only go for these long rides once or twice at the weekend.  There's a set route I like to ride and my battery only gets me about 70% of the way.  So I stop and rest for 45 minutes to top up at 2 amps.  I will in future be charging at 4 or 4.5 amps to bring that stop down to 20 minutes.  Apart from those long weekend rides, for the rest of the week I'm only using the stock charger.  So I don't think I'm going to notice any reduction in longevity of my battery by doing these occasional top-up charges.  From @Cranium's tests I feel confident that the wiring and connector can handle the current I will be charging at as he has tested charging at 5 amps since some years ago.

 

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5 hours ago, Cranium said:

The battery cells in my Ninebot are LGDDBMG11865 which translates to LG 18650 2900mAH batteries (2850mAH nominal).  I was even able to put together a spec sheet from online (PDF found in post below).  

Normal charge current is 0.5C or 1.425mA.  Max charge current is 1.0C or 2.850mA.  Since the Ninebot has 2 cells in parallel, the normal charge rate is 2.85A and max charge rate is 5.7A.  This is from the manufacturer and is completely safe to do and thoroughly tested.  As noted in the PDF, the overcharge testing procedure actually cycles the battery for 7 hours at charge rate of 3C up to 4.2V then discharges at 570mA to 2.5V.  It passes if it doesn't blow up or catch fire.  

As you mentioned, temperature also matters.  Good operating practice would not be to charge on hot batteries.  The max charge temperature of these cells is 45°C or 113°F.  My batteries don't normally get that hot in normal riding even though my controller gets really hot.  And if you start charging with the batteries warm (45°C or lower), they will continue to cool during the charge cycle.  

So the way I see it, the only real consideration for charging at higher current is:  Are you willing to possibly shorten the life of the battery a little to charge faster?  Other than that everything else is the same.  For me the answer is YES.  I don't charge at a higher current all the time but there are times where it has been very convenient.

That all sounds good for that cell.  Sounds like you understand the tradeoffs.  As long as people realized 0.5C is the nominal charge rate. 

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2 hours ago, RooMiniPro said:

Generally from the cell manufacturers' specifications and from common knowledge that modern, good quality 18650 cells, as well as lithium polymer pouch cells, can charge at a rate of at least 1C without any concern.  Some cells can handle many times that. 

 

There is no point in mentioning pouch cells or Li-Po cells since the batteries in question are Li-Ion cylindrical cells. I don't think there is yet any 18650 that can handle "many times" 0.5C rate, but like I said what's important is what the actual cell can handle not any specific variety.  An H2 or VC4 might be able to handle more than 1C I didn't check, but it's not really important unless you are using them, and are aware of the tradeoffs. 

I'm not saying you can't use your charge rate, I just clarifying the justification and the tradeoffs.  Yes I realize 2P means you can use twice the rate given proper precautions.  I like your project, and think having an external battery operated charger is a good idea for many situations.  

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34 minutes ago, FreeRide said:

There is no point in mentioning pouch cells or Li-Po cells since the batteries in question are Li-Ion cylindrical cells. I don't think there is yet any 18650 that can handle "many times" 0.5C rate, but like I said what's important is what the actual cell can handle not any specific variety.  An H2 or VC4 might be able to handle more than 1C I didn't check, but it's not really important unless you are using them, and are aware of the tradeoffs. 

I'm not saying you can't use your charge rate, I just clarifying the justification and the tradeoffs.  Yes I realize 2P means you can use twice the rate given proper precautions.  I like your project, and think having an external battery operated charger is a good idea for many situations.  

Yes I agree that there are trade-offs when charging at a higher rate, but in this case I do not believe I will notice a difference in battery lifetime when charging at 0.7-0.8C versus 0.5C.  If you have experience in charging 18650s at higher charge rates over several hundred charge cycles and noticed faster degradation I would be very interested to hear of your findings.  Or from anyone else who has experience with this. 

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