safe to charge battery while riding?

[melk]

Would this work to charge the stock battery, at all?

If so, would it be ok to have it plugged in while riding?

Code Select Expand

Jackery Explorer:
240 watt-hour (16Ah, 14V) lithium-ion battery pack
AC outlet (110V 200W, 400W peak)

---------------------

Code Select Expand

My stock radmini battery:
672 watt-hour (14Ah, 48V) lithium-ion

[DCH3416]

That aught to charge the battery just fine.

Whether you can charge and ride at the same time. Maybe? Probably not recommended though.

[crorris]

I would be concerned about potentially hitting the cable/plug where it plugs into the battery with my leg or knee while pedaling. You could end up damaging the jack on the battery if that happened. I'm also not sure how much actual additional ride time that might give you. Using the standard charger the battery charges pretty slow and takes a long time. I think in most cases you're going to be using a lot more power than would be replaced by this. Check your display on the bike when you are riding as you normally do to see how many watts it is using. Even on pedal assist level 1 you will use more than this is providing. This Jackery has a 240 watt hour battery. The Rad charger draws 120 watts from the AC power and provides 96 watts output charging (48v x 2 amps). There also is some energy lost as well inside the Jackery converting from the DC battery to the AC for the power outlet. Based on this, it looks like the Jackery would only be charging for about 2 hours or less. If you already own the Jackery, you could try using it to charge your Rad battery (not while riding) from zero and see how much it actually charges the battery. That would give you a very rough estimate of how much extra battery you might actually get. If you don't already own the Jackery, it may not be worth it just for this application. You'd probably be better off putting the cost of this toward a second Rad battery. it sucks that they are so expensive though.   

[crorris]

Just saw this other topic on using the Rad charger with an inverter (like what's inside the Jackery).  Topic: 12 volt accessory adapter charging  (Read 30 times)

The Jackery is 200 watts continuous/400 watts peak. It will be interesting based on the experience of these other folks to see if that is enough for the charger. I'm not sure why the other people had issues. The 120 watts on AC that is specified and written on the charger is less than the inverters he was trying.

[melk]

I would be concerned about potentially hitting the cable/plug where it plugs into the battery with my leg or knee while pedaling. You could end up damaging the jack on the battery if that happened. I'm also not sure how much actual additional ride time that might give you. Using the standard charger the battery charges pretty slow and takes a long time. I think in most cases you're going to be using a lot more power than would be replaced by this. Check your display on the bike when you are riding as you normally do to see how many watts it is using. Even on pedal assist level 1 you will use more than this is providing. This Jackery has a 240 watt hour battery. The Rad charger draws 120 watts from the AC power and provides 96 watts output charging (48v x 2 amps). There also is some energy lost as well inside the Jackery converting from the DC battery to the AC for the power outlet. Based on this, it looks like the Jackery would only be charging for about 2 hours or less. If you already own the Jackery, you could try using it to charge your Rad battery (not while riding) from zero and see how much it actually charges the battery. That would give you a very rough estimate of how much extra battery you might actually get. If you don't already own the Jackery, it may not be worth it just for this application. You'd probably be better off putting the cost of this toward a second Rad battery. it sucks that they are so expensive though.   

Thanks for the thoughts. I already own it, so next time I guess I will try charging the stock rad battery and see how that goes. Jackery does sell larger models with 500W or even 1000W output and above (although at very steep prices)

I really just don't understand enough to know if there is a real danger even trying to charge the battery while it is also discharging. You would think the controller would have the ability to deal with this scenario and certainly not allow anything that would damage the battery (or the controller itself) but, who knows.....

[JimInPT]

I really just don't understand enough to know if there is a real danger even trying to charge the battery while it is also discharging. You would think the controller would have the ability to deal with this scenario and certainly not allow anything that would damage the battery (or the controller itself) but, who knows.....

You can switch the battery on while charging and bring up the display (and I think the headlight), but keep in mind that the designers would have tested for this, but probably didn't envision a mobile-charging scenario where the motor is under load while the battery is charging.  Keep an eye on the thermals; that might be a lot for the controller to deal with and I'm thinking it or the battery could get pretty warm.

Pure speculation and I'm just a dumb recovering mechanical engineer, not electrical, but all engineers worry about stuff like this.  Even the ones who drive trains, I bet.

[DickB]

I don't see a problem with operating the charger while riding. I have reverse-engineered a good portion of the battery and its BMS. The battery actually has separate charge and discharge current paths. The Rad charger puts out 2A max. If the motor is using that or more, the 2A will go to the motor; if less to the cells. The controller has nothing to do with it - it just sees voltage and current from the battery, and doesn't "know" if current is coming from the charger, battery, or both. I don't see heat as being a problem. While riding the BMS is not doing much either except monitoring for fault conditions. It does not enable balancing except during low "trickle" charge only.

[crorris]

Great info DickB. Thanks!

[melk]

I don't see a problem with operating the charger while riding. I have reverse-engineered a good portion of the battery and its BMS. The battery actually has separate charge and discharge current paths. The Rad charger puts out 2A max. If the motor is using that or more, the 2A will go to the motor; if less to the cells. The controller has nothing to do with it - it just sees voltage and current from the battery, and doesn't "know" if current is coming from the charger, battery, or both. I don't see heat as being a problem. While riding the BMS is not doing much either except monitoring for fault conditions. It does not enable balancing except during low "trickle" charge only.

Very interesting indeed. I did not consider the controller at all in this, I forgot that it sits between the battery and the motor. I'll have to chew it over some more.

The balancing during trickle charge, is that cell balancing? How many cells are there typically in the stock rad batteries?

[DickB]

Yes, cell balancing. My Rad Rover 5 has 4 cells grouped in parallel with 13 groups in series.