Help! Hi from newbie. 7A or 12A rated current controller for 36v10.4A battery?

Brillo

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Aug 4, 2019
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Hello and thanks to everyone who has contributed to this wonderful treasure trove of ebike info_Of course the more you know the more you realize you don't know!
So as expected with the cheap kit I have the PAS is either off or full speed.I want to upgrade the controller + display for more flexible settings and need to know if it's best to go with 7A ,14A max or 12A,25A max controller if the battery is 36v10.4A. Motor is "250"watt. Mainly used on the flat with occasional short climbs,pottering speed of 15mph .May occasionally have to carry shopping so total weight possibly 125kg.

Thanks in advance.

https://www.greenbikekit.com/motor-controller/kunteng-kt-48v-36v-500w-motor-controller-for-lcd-led.html

Current controller.
31505EBV-36V250WRN-j.jpg
 
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Nealh

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Those Voilamart kit's are very basic no control over PAS with no lcd to flip assist levels.
The GBK coffering's are KT so good, you will need an LCD3. 5, 6 or 8 model to gain access to parameter settings. The 12/25a one will kill your 10.4ah battery over time, I doubt the cells inside will cope very well with 5/6a continuous discharge so stick with the 15a one or get this one and limit the current if need be.
The Voilamart PAS 8 pole should work fine, though they are quite cheap so a 8 pole will be good to have to rule out incompatibility and a throttle if you need one but again the twist grip will work fine. Just a case of insuring wiring order when connecting up and if connector's don't match solder and shrink together.
One thing you will need to check is the motor wire if it only has 8 wires/pins then you will have to get an ext wheel speed sensor/spoke magnet as well if you want a fully functional LCD. Wiring one is very easy and we can tell/guide you if you want us to.
 
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Brillo

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Aug 4, 2019
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Cheshire, UK
Thanks for the reply Nealth.
I may change to thumb or half throttle but for now the original throttle will do while deciding.
I assume as the controller needs to communicate correctly with the LCD so best to buy KT controller + kt LCD (plus a speed sensor). Considering the low cost I will buy the KT 8poles PAS.

Showing my ignorance- how do you get the 5/6amp continuous discharge figure and why would that harm a 10.4amp battery? Would the original controller work with the KT LCD ?
Cheers.
 

Nealh

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Controller and LCD need to be compatible, by this meaning they have to hand shake/communicate to each other. Programming /protocols are different from each company so mixing and matching means they might work but you don't get all the info displayed on the lcd.

I am guessing that your 10.4 ah battery is only 4 cells in parallel and uses maybe Samsung 2600mah cells which certainly wouldn't cope with a constant 5a draw and certainly not 6a, you would kill the battery /see definite capacity loss in less then a year. To utilise a 12/25a controller you need a battery with pucker 10 cells in side or better.
 

Brillo

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Ah,I see. 10 x 2600mah in parallel to cope with 25amp draw. With a 10.4A battery the controller will be try to draw over twice the 2600mah from each cell. Thanks.
 

Nealh

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Not quite.
2600mah is the cell capacity rating and not the current discharge rating (CDR), the CDR is approx. 5a continuous. 10.4ah battery is likely to have only 40 cells, so 4 in parallel to give (10.4ah) & then 10 groups/strings of 4 connected in series to give 10s /36v.
The important bit is the parallel group/string has only 4 cells, each cell with a max 5a CDR is only good for 20a continuous for a short time.

My old Samsung battery was 5 in parallel with 2600mah cells, the battery lost approx. 30% capacity after 18 months with a 17a controller. Though cells have a CDR rating, for them to last current draw needs to be about half of their rating for longevity. So for future battery purchases knowing the nitty gritty of the actual cell used is important to know and in general try and opt for at least good 10a rated cells.
 
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sjpt

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My old Samsung battery was 5 in parallel with 2600mah cells, the battery lost approx. 30% capacity after 18 months with a 17a controller. Though cells have a CDR rating, for them to last current draw needs to be about half of their rating for longevity. So for future battery purchases knowing the nitty gritty of the actual cell used is important to know and in general try and opt for at least good 10a rated cells.
Sounds very similar to our Woosh setup (HL battery with 2600mah Samsung cells, 17a controller, XF07). How far had you ridden in those 18 months, and how often had you used a significant proportion of the full power?

We have ridden just over 1000 miles in just over 1 year, and only hit the power hard for steeper hills; mostly riding in 2/5 and 3/5 on the hills. It seems that 4/5 and 5/5 give greater speed on the flat, but tend not to help that much on the hills. I guess that the XF07/battery combination can't deliver the extra power at low speeds (6mph)?
 

RossG

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This is a useful web page relating to battery configurations, it shows many different battery packs and cell arrangements.
It's a long web page that delves into all sorts of e-bike stuff, but work your way down and you'll find some interesting info. Worth bookmarking.

 
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sjpt

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Thank you. That complements the information I can get from ebikes.ca; for our setup
 

Nealh

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Sounds very similar to our Woosh setup (HL battery with 2600mah Samsung cells, 17a controller, XF07). How far had you ridden in those 18 months, and how often had you used a significant proportion of the full power?

We have ridden just over 1000 miles in just over 1 year, and only hit the power hard for steeper hills; mostly riding in 2/5 and 3/5 on the hills. It seems that 4/5 and 5/5 give greater speed on the flat, but tend not to help that much on the hills. I guess that the XF07/battery combination can't deliver the extra power at low speeds (6mph)?
My battery was part of the now defunct Oxydrive kit, though the bullet proof Bafang CST is still in use and has 6,5k miles on it now.
The Samsung 13ah battery used 2600mah 26F cells 5.2a CDR , mileage was about 3k in that time span though I ride long so battery was always down to lvc to eke out range and didn't spare the horses some of the time. De-restricted I could manage 24.5 mph which also would have taken it's toll on the cells.
It was my first hub kit and battery learning curve was at it's infancy for me, I now know so much more.
 

sjpt

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My battery was part of the now defunct Oxydrive kit, though the bullet proof Bafang CST is still in use and has 6,5k miles on it now.
The Samsung 13ah battery used 2600mah 26F cells 5.2a CDR , mileage was about 3k in that time span though I ride long so battery was always down to lvc to eke out range and didn't spare the horses some of the time. De-restricted I could manage 24.5 mph which also would have taken it's toll on the cells.
It was my first hub kit and battery learning curve was at it's infancy for me, I now know so much more.
Thanks for that response. It looks as if we should get at least 3 years, 3000 miles out of the battery and with luck quite a bit more. We tend not to hammer it too much, and to charge it to full when it gets somewhere around 1/2. It is difficult to judge how much charge it has as the battery level display on the KM529 varies so much with power used; unless the battery is very fully charged the display regularly drops 2 (of 5 or 6) levels as we hit a hill, sometimes even 3. Presumably the reading is just based on the voltage at either the battery or controller output (which should be pretty much the same?).
 

Nealh

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The drop in bars/battery level is known as voltage sag when demand/current is asked typical of most batteries, once demand/current is reduced they rebound to a stable higher voltage until next time.