Electric Bike Conversion Kit Battery Pack: Overheating Issues

From my own experience with 24v 6.6 Ah lithium-ion battery packs from Clean Republic (the ones that come with their Hill Topper electric bicycle conversion kits) are prone to cutting out or automatically turning off in long climbs.

Users try to overcome the issue by turning the battery pack off then on again. The off-on solution works until the controller inside the battery pack get busted (perhaps the fuse or the protecting wire in the controller burns out upon reaching a maximum temperature). If the controller does not get busted the high temperature sometimes melt the soldering inside the chrome plug connector, cutting out the power supply to the motor. It is difficult to determine if the cutting out of the motor is due to melting of connections inside the chrome plug or burned out controller.

Apparent overheating issues are reported by least 5 people who posted their experience on the net.
1. Angela Medina of Seattle (see Sept 27, 2013 CR Facebook post)
2. Noel Jarvis of Florida (see CR Facebook post)
3. Elrollo (on Clean Republic forum)
4. Rinataga (on Clean Republic forum)
5. cwestergard (on Clean Republic forum)

The cutting out issue is consistent with my own experience with my Clean Republic 10-mile Lithium-ion Sprinter.  I had two of my controllers busted which I had to return to Clean Republic two times. Thanks to them they replaced both but with some delay the first time and promptly the second time. Unfortunately, I spent 125 USD total to get the two replacements: 50 USD for sending back the first one to Clean Republic for inspection and replacement, another 50 USD for sending the second one, and 25 USD for Norway import duties for receiving the second replacement (which Clean Republic sent back as ' 90 USD merchandise' instead of the customary '1 USD gift' customs declaration). I was levied double import taxes because of Clean Republic's erroneous re-export declaration of the repaired Sprinter battery pack as a new merchandise. They should have correctly declared it as 'repaired item resent to customer'. When I alerted Clean Republic about the mis-declaration, I was advised to notify them on how to declare the repaired item next time before they could sent it back to me--which is weird considering that it is THEIR responsibility as shipper to accurately declare a shipment's content as repaired item sent back to customer and not as a new merchandise which will definitely incur the receiver new import duties!

Anyway, the main issue here is the problem of CR's and LEED's battery packs/controllers cutting out power on steep climbs due to overheating. I discovered that this issue is due to overheating of the battery pack controller on steep climbs which burns out a component inside. Replacing the controller with a new one solves the problem but this costs money to the user, especially if the user sends back the whole battery pack to Clean Republic/LEED. The most cost effective way to get the controller replaced is to simply report the problem to seller. Ask them to send back the repaired pack as a gift. Otherwise toll charges will be levied again.

Overheating is normal with Lithium-ion batteries especially when the output required is high (in long climbs this is true!). Turning the battery pack off and on will only reset the controller but will not solve the overheating problem and will either result to the controller burning out or the the chrome plug connections melting.

My old SLA battery pack melted the connecting wire in a 1 kilometer steep climb back in 2011. Last March 2014, my new LEED battery pack (purchased January 2014) had its soldering inside the chrome plug connector melted after several steep climbs on this route. First, I thought the controller was busted but upon inspecting the chrome plug it turned out that the controller is still OK and only the melted soldering in the chrome plug is the problem. After I re-soldered the wirings the LEED battery pack worked again. This reminded me of a similar problem I had with my SLA battery pack in 2011.

The moral of the story is this: there is a maximum temperature (perhaps, between 50 - 60 Celsius) that Clean Republic and LEED battery controller (especially the chrome plug soldering) could tolerate in long climbs even if users assist the motor by pedaling. In other words, there is a limit to how long the battery could assist a user's climb--the maximum temperature that the battery/controller could tolerate.

Some of the batteries from Clean Republic and LEED are packed in phase change material (PCM) that is supposed to protect the batteries from overheating (see here for LEED battery specs and  here on AllCell and Clean Republic's  joint venture).

Possible work around: avoid overheating the battery!

Mike Shoppe advises not exceeding 32 Celsius in his post on the Forum (see here). I am sure he meant the outside operating temperature but the battery connector/chrome plug itself gets too hot such that the immediate surrounding area near the chrome connector plug could get as hot as more than 47 Celsius in my experience (in this peripheral temperature the connector itself is too hot to touch).

My 30K Samsung battery pack from LEED also shuts down on long climbs but does not reset when I turn it off and on again. Instead it turns off and cannot be turned on again until I have recharged it. To avoid this problem I installed a thermometer to measure the temperature of the connecting chrome plug. There is a 30-second to 1 minute delay in detecting increase in temperature but as soon as it hits 31 Celsius, I turn the battery off. The temperature still increases up to 47 Celsius even with the battery off but cools down again. As soon as it cools down I turn the battery on again.  I haven't tested this with my Clean Republic Sprinter but this seems to be the way to avoid burning out the controller.

If your controller gets busted, just send it back to Clean Republic/LEED. But first check if your chrome plug connector soldering is intact

In case you have already busted your controller due to overheating in long climbs, just send it back to Clean Republic/LEED. They should replace it with a new one. Do not send the whole battery pack if you want to avoid the expensive shipping fees and possible re-importation duties (due to possible mis-declaration errors that could happen). Before sending the controller, check if your chrome plug connector soldering is intact using a multimeter tester. Otherwise, you might unnecessarily send back the controller that is still working when the real problem is actually just the melted soldering inside the chrome plug.

NOTE: More posts on e-bike conversion projects are available here.