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KS18L - max. charging current


Seba
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Hi,

does anyone knows what is the charging current limit for KS18L? I mean limit imposed by wire gauge or BMS circuitry (wire gauge, MOSFET or balancing capabilities etc.). I plan to make a long trips and having quick charger would be important to overcome ~60 km limit on a single charge (60 km is a safe distance I've confirmed in my case). After about 50-60 km I could stop in a restaurant for a hour or two and charge wheel while resting, having lunch etc. With standard charger, during one hour I get charge equivalent to another 6-8 km, which is too low for me. I would be happy to get at least 20 km of charge during one hour of charge, so after two hours of charging I can ride another 40 km.

Next year I plan an expedition, during which I want to cross Poland from north to south and back on a KS18L. I would like to make a 100-120 kilometers daily - three hours of driving then two hours break, another two hours of driving then one hour break, finally one hour's drive. Two weeks of riding, over a thousand kilometers to ride :-) Standard charging overnight, quick charging during daily breaks.

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9 minutes ago, phatmike said:

You can use two chargers with the KS18 L

Yes, I know, but this is still not enough - I'll get max. 16 km of additional range per hour of charging.

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30 minutes ago, Seba said:

Hi,

does anyone knows what is the charging current limit for KS18L? I mean limit imposed by wire gauge or BMS circuitry (wire gauge, MOSFET or balancing capabilities etc.). I plan to make a long trips and having quick charger would be important to overcome ~60 km limit on a single charge (60 km is a safe distance I've confirmed in my case). After about 50-60 km I could stop in a restaurant for a hour or two and charge wheel while resting, having lunch etc. With standard charger, during one hour I get charge equivalent to another 6-8 km, which is too low for me. I would be happy to get at least 20 km of charge during one hour of charge, so after two hours of charging I can ride another 40 km.

Next year I plan an expedition, during which I want to cross Poland from north to south and back on a KS18L. I would like to make a 100-120 kilometers daily - three hours of driving then two hours break, another two hours of driving then one hour break, finally one hour's drive. Two weeks of riding, over a thousand kilometers to ride :-) Standard charging overnight, quick charging during daily breaks.

I would advise not to go over 5 Amps, that goes for nearly all EUC available, reason is the wiring.

If you really want a faster charging then you Need to Change the wirings inside the Wheel.

5 Amps are About 420Watt per Hour...

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18 minutes ago, US69 said:

5 Amps are About 420Watt per Hour...

Yes, I'm aware about 5 amps being a safe limit, and 5 amps is an absolute minimum what allows me to reach my goal. 420 Wh equals to 21 km (safety margin included). I'm wondering if using 6 amps charger may also be considered safe enough. This additional one amp would be a good, additional 20% safety margin. I'm not sure if it will be easy to plan all my expedition with each day divided perfectly to 60 km + 40 km + 20 km segments, so having 10-15 km of charge reserve would be a wise idea :)

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1 hour ago, Seba said:

Yes, I'm aware about 5 amps being a safe limit, and 5 amps is an absolute minimum what allows me to reach my goal. 420 Wh equals to 21 km (safety margin included). I'm wondering if using 6 amps charger may also be considered safe enough. This additional one amp would be a good, additional 20% safety margin. I'm not sure if it will be easy to plan all my expedition with each day divided perfectly to 60 km + 40 km + 20 km segments, so having 10-15 km of charge reserve would be a wise idea :)

You could add second charge port and wiring in parallel with the existing one, then use for example two 4A chargers or 8A charger with two outputs. Check the amp-hour capacity of the cells, the rule of thumb is you shouldn't charge 18650 lithium-cells above "1C" -speed, which means charging from empty to full in one hour (theoretically, in practice it takes longer because the amperage and charging speed drops after the constant voltage -phase begins). So 1C = same amount of amps for charging as the combined amp hours in the parallel packs, 2C = twice the amount of amps (theoretical 0.5h charging), 0.5C = half the amphours (charged to full in 2 hours, again theoretically). The faster you charge the cells, the more it stresses them and lowers their lifespan and capacity. If going way overboard with charge current, the cells can overheat and catch fire/explode.

I don't know the battery set up for the KS18L, but if it's 20S (84V max, 74V nominal for 3.7V nominal cells) batteries, you can make a good enough guesstimate of the amphours based on nominal voltage and watthour-capacity, so for example if it's 1000Wh total capacity, 1000Wh / 74V = around 13.5Ah. 8A shouldn't be a problem with the cells, since it's "only" about 0.6C charge speed, but still should charge your pack nearly to full in 2 hours (I say nearly, because of the constant voltage-phase in charging which slows things down, it would charge in about 1.6 hours, if the current was 8A all the way through). The parallel packs should divide the total current evenly enough (since the packs are already connected in parallel they are all at the same voltage, but there might be slight differences in internal resistances).  

But even if the cells can take it, there's no saying about the BMS or the wiring, the latter is easy to fix by changing to thicker gauge wiring, if necessary, but changing the BMS is a no go (especially because I think newer KS's use some form of dataline between the mainboard and the battery BMS's). GX16's are something like 5-7A max per connector, don't know if it's a conservative value or not, but wouldn't like it if the charge port got so hot as to start melting the plastic parts inside the connector or the shell around it ;)  Thus using two ports in parallel with 4A each and thick enough wiring.

Edited by esaj
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18 hours ago, andress said:

@esaj Actually KS 18L doesn't use GX16 but Lenovo connector. Do you happen to know what is the max amperage for those?Monokoleso-Kingsong-KS-18L-18.JPG

Can't see the image you've added, but do you mean Lemo-connector or Lenovo-connector? I don't know what the latter is, for Lemo's, there are multiple series and the amperage depends on series and amounts of pins, for example the K-series 2-pin version can handle 15A, but the 8-pin version only 5A...

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Some googling later, the so-called "Lenovo-standard" connector is called C36 by many manufacturers/resellers, such as for example:  

https://www.bixpower.com/CNT-C36-p/cnt-c36.htm

https://lasa-electronics.co.za/products/laptop-accessories/c36-tip-plug-power-connector-lenovo-x1-carbon/

The "C36" is not a standardized designation though, many manufacturers have completely different type of connectors under the C36 -name.

I couldn't find any "official" number for the amperage, but there are chargers meant for Lenovo-laptops going up to at least 120W at 19.5V output (6.15A):

https://www.tme.eu/gb/details/ak-nd-52/laptop-power-supplies/akyga/cpsunotaky-07812/

Some other site mentions 135W / 20V Lenovo charger, which would be 6.75A. 

EDIT: Lenovo's own web-store sells chargers up to 230W:

https://www.lenovo.com/gb/en/accessories-and-monitors/chargers-and-batteries/chargers/PWR-ADP-BO-TP-230W-AC-Adapter-slim-tip/p/4X20E75119

Doesn't mention voltage though, but if it's around 20V, that means over 10A max output current. Not sure if the "slim-tip" is the exact same connector though?

 

Edited by esaj
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  • 2 weeks later...

News are coming :) Charger connectors are connected in paralell, and only two 18AWG wires are going to the controller board. So we can assume that charging current cannot exceed 7A. This is the limit imposed by wires, and 7A equals to 0.5C for whole EUC (there are two battery packs, 7Ah each).

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  • 1 month later...

Did anyone find out about this?
I find it an interesting topic, mainly taking into account the difference in price between:

The official charger ($75)
84v 2.5A charger 5.5x2.1 ($34)  + Lenovo connector adapter 5.5x2.1 ($1) 

84v 3A charger ($21) + Lenovo connector adapter ($1). Requires cutting cables as there's no matching connection, unless we find that adapter type.

Having 2 charging ports may make some people think about getting a 2nd charger, if they need it.

Maybe those I linked will not work with the KS18L, I don't know, I hope someone will correct me if that's wrong!

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Finally I've bought a 6A 84V charger (https://nexun.pl/shop/pl/ladowarki/211-ladowarka-20s-84v-6a-505w.html) and made few modifications:

  1. Added voltage and current meter.
  2. Current can be regulated from 1A to 6A.
  3. Voltage can be regulated from 78V to 84V (equivalent of 3.9V to 4.2V per cell or 60% to 100% SoC).

I will post photos and details this evening. However in field tests this charger set to 6A performs very well, allowing for quite fast recharge in reasonable time.

Edited by Seba
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On 10/28/2018 at 4:09 AM, Seba said:

Finally I've bought a 6A 84V charger (https://nexun.pl/shop/pl/ladowarki/211-ladowarka-20s-84v-6a-505w.html) and made few modifications:

  1. Added voltage and current meter.
  2. Current can be regulated from 1A to 6A.
  3. Voltage can be regulated from 78V to 84V (equivalent of 3.9V to 4.2V per cell or 60% to 100% SoC).

I will post photos and details this evening. However in field tests this charger set to 6A performs very well, allowing for quite fast recharge in reasonable time.

Your charger must match the KS18L BMS system else you will destroy your battery pack in short order.

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3 hours ago, Jerome said:

Your charger must match the KS18L BMS system else you will destroy your battery pack in short order.

6 A flows into two battery packs, each with own BMS. Because of almost identical pack resistance, this current divides equally to 3 A per pack. I assume it should be well within the limits of charging-side MOSFET of BMS. Each pack of KS-18L is configured as 20S2P and made with 40 cells (LG MJ1). Each cell is rated at 3500 mAh with 0.5 C of standard charging current (1 C max.). So for each pack standard charging current is 3.5 A, which is higher than 3 A. So far, so good, but how about the wiring? AWG17 wires are used on charging side, which imposes 7 A limit in total. This is also higher than 6 A used in my charger.

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8 hours ago, Seba said:

6 A flows into two battery packs, each with own BMS. Because of almost identical pack resistance, this current divides equally to 3 A per pack

Do you know the resistance of each pack based on measurements or assumption? I am probably being overly cautious and you are okay. Isn't the ah rating of each battery pack ~6 ah? If so you would be charging at 50% of the total capacity. That seem high to me, but the bottom-line is it will work, the only question is will it cause premature failure. I will follow your progress as I want to do a 161 km day ride next summer solstice, but charging down time would make it hard to do the ride in all daylight, which is must for me. Good luck and keep us posted. Thanks for the link to the charger!

Edited by Jerome
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On 8/24/2018 at 5:09 AM, Seba said:

Next year I plan an expedition, during which I want to cross Poland from north to south and back on a KS18L

Nice. If I was in Poland I would take that trip with you. Sounds like fun. :efefae4566:

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16 hours ago, Jerome said:

Do you know the resistance of each pack based on measurements or assumption? I am probably being overly cautious and you are okay. Isn't the ah rating of each battery pack ~6 ah? If so you would be charging at 50% of the total capacity. That seem high to me, but the bottom-line is it will work, the only question is will it cause premature failure. I will follow your progress as I want to do a 161 km day ride next summer solstice, but charging down time would make it hard to do the ride in all daylight, which is must for me. Good luck and keep us posted. Thanks for the link to the charger!

No, I didn't made any measurements. This is just assumption, but INR18650 cells (like other Li-Ion cells) are manufactured with very tight tolerances, so it's safe to assume that each battery pack have equal resistance. Plesae note that many EUC battery packs BMSes lack any type of balancing circuit. KS-18L battery pack BMS is equipped with bleeding balancer working with only 40 mA (0.04 A). Single battery pack capacity is 7Ah, total capacity is 14Ah. Safe (standard) charging current for 14Ah pack consisting of MJ1 cells is 7 A (0.5 C), so with 6 A we have a 1 A of additional safety margin.

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11 hours ago, Lutalo said:

Nice. If I was in Poland I would take that trip with you. Sounds like fun. :efefae4566:

You can always go for a two week trip from Washington to Miami - it's about 1130 miles, about 80 miles per day :)

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5 hours ago, Seba said:

You can always go for a two week trip from Washington to Miami - it's about 1130 miles, about 80 miles per day :)

You have me thinking my friend. That's a whole lot of overnight hotel stays though. Despite my deep admiration for what he did, I ain't rollin like Monsieur Flex. For me, a cheap motel beats a tent anyday of The week. :efee8319ab:

Edited by Lutalo
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1 hour ago, Lutalo said:

You have me thinking my friend. That's a whole lot of overnight hotel stays though. Despite my deep admiration for what he did, I ain't rollin like Monsieur Flex. For me, a cheap motel beats a tent anyday of The week. :efee8319ab:

I can't promise I could make it, but I'd sure like to try! (As I invite myself!) Sounds like fun! (KS18S-1680 wh)

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