"NTC option" in BH Easy Motion Li-ion Battery Charger

[Ebike Commuter]

I was looking at the back of the 36V charger that came with my Easy Motion Street bike and noticed that in addition to a "+" and "-" output there is a "NTC" output on the charger. The charger is evidently made by a company named "Modiary Co. Ltd," located in Shenzhen, China. Searching the web, I found the following website that sells this charger for $30 USD and it mentions that NTC is an option.

Link to website selling charger:
http://www.aliexpress.com/item/36V-...ower-tool-solowheel-e-scooter/1566236363.html

Does anybody know why there is an NTC option built into these Lithium battery chargers? NTCs are negative temperature coefficient thermistors and my understanding is that these circuits allow for battery temperature monitoring during charging. Temperature monitoring is sometimes needed for NiMH and NiCAD battery chargers, but not necessarily for Li ion battery chargers. So, why then did BH choose a charger with this functionality? Is the NTC circuit actually used when charging the Lithium BH Easy Motion batteries? And If so, how is it used (e.g. to reduce current/voltage or abort charging under high battery temperatures)?

 

[Ravi Kempaiah]

Actually, this is the charger used and the adapter is quite different from XLR for NEO or EVO batteries.
There are temperature sensors in certain motors (for ex: ST2) and also in chargers on bikes like BionX or Stromer. Intially, BH was using a charger with fans and then they moved to fan-less chargers like the one mentioned above.
From what I have read on German forums, fan-less chargers change the output current if it senses temperature rise.

 

[Vern]

Actually, this is the charger used and the adapter is quite different from XLR for NEO or EVO batteries.
There are temperature sensors in certain motors (for ex: ST2) and also in chargers on bikes like BionX or Stromer. Intially, BH was using a charger with fans and then they moved to fan-less chargers like the one mentioned above.
From what I have read on German forums, fan-less chargers change the output current if it senses temperature rise.

Is this an option for a replacement/second charger? Heck of a lot cheaper!!

 

[Ravi Kempaiah]

Is this an option for a replacement/second charger? Heck of a lot cheaper!!

Believe me. I spoke about this to few concerned people and expressed my thoughts.
Anyway, not going to happen because the batteries are custom shaped and the connectors are quite different compared to XLR. If you knew your dealer, you could certainly get the charger at a good value.

 

[Ebike Commuter]

Is this an option for a replacement/second charger? Heck of a lot cheaper!!

Seems to me like it could be a viable replacement charger. The main issue is that you would need to ensure that the connector to the battery is of the same type as the existing charger. The singatron plug looks to be identical to the receptacle on the frame of my street. One could also purchase the extension "pigtail," from easy motion and solder it to an XLR connector.

 

[Ann M.]

Better check the polarity on the XLR that it matches what your Neo or Evo setup or it won't do anything.

 

[Ebike Commuter]

The Modiary 36V charger that comes with the BH Easy Motion Street has 3 output wires: red + DC, black -DC and a thinner white NTC wire. One can use a voltmeter to ensure the correct polarity. I'm not sure what the white NTC wire if for. Seems like it could be some type of temperature protection. For example to prevent charging or to adjust voltage when the ambient temperature is very high or very low. Regardless, I have confirmed that the white NTC wire it not required for ambient temperature charging at room temperature.