Charging lifepo4 and then immediately riding

[morph999]

Is there any problem with charging the lifepo4 and then immediately riding it with very little time in between? I waited about 10 minutes between charging and riding. The batteries felt slightly warm but not hot at all after I rode for a few miles.

I just felt them after about 40 minutes of resting after the ride and they feel the same temperature as before so I'm thinking that they didn't even get warm during the ride.

For anyone curious, the 5303 with 72v 35 amp controller has peak amp of about 43 amps...at least on mine it does. Cruising at 20 mph only uses about 12 amps. Half throttle while taking off from dead stop only uses about 30 amps.

 

[icecube57]

They actually supposed to perform better with less voltage sag when they are warmer. They warm up even more during discharge. Especially at the end of the pack cycle my Thundersky cells are warm to the touch. My cells dont warm when charging so im not sure what you are doing lol. You are not gang raping with chargers are you.

 

[Ypedal]

The joys of lithium.. charge and discharge at will.

Nicad/Nimh should be allowed to cool down before charging however.

And yeah, for lithium cells to get hot while charging, you must be pushing some high C rate ?? ( warm is ok.. hot is not )

 

[morph999]

I'm only charging with .5 C . They weren't warm after charging. I just waited 10 minutes just in case they needed to rest a little bit. lol. It's hard to tell the difference between warm batteries and room temperature batteries. I'd feel them and then be like, " are they warm". Then I'd feel them again. I guess I'm just surprised that they don't get very warm during charging or discharging.

 

[LI-ghtcycle]

Anything that isn't uncomfortable to the touch probably isn't terribly hot, I don't remember what batteries your using, but I know with the Dewalt's you really have to do multiple charges to get a full charge (this is the fault of the charger I am sure).

With the Dewalt chargers they stop charging after the 3rd LED is lit, so it's not really a risk since it's not a continuous charge, and it's only during the few seconds of a "top-up charge" after a battery has received a full charge cycle that any charging is going on.

My batteries don't get hot, but I do attempt to get maximum surface charge to try and compensate for the poor balancing of these chargers. I hope to get a battery charger eventually that will charge mine as a group and eliminate the individual battery charge method which is really tedious with 8 batteries (and now I need 8 more!?! :lol: )

I also know that raising the individual cell voltage too high is bad, but I'm not even passing 3.7V per cell with my method so far, so I think I'm pretty safe at 3.625 Average volts per cell.

I have checked individual cells on some battery packs that seemed to have much longer charging times than others, and surprisingly all the cells were perfectly balanced (at least according to my HF $3 multimeter I used to have a nice meter I had for years, and then I left it in the rain! ) so I think your pretty safe.

 

[dogman dan]

I agree, no problem to charge and then ride immediately. Or to ride in warm weather and charge immediately. If either charging or riding got them hot that would be bad, but they just don't heat up like nicads. When I was running my 5304 on nicads you could just about cook a burrito by putting it in the battery bag. The lithium stays very cool by comparison.

When I first got my ping I worried about cooling it down before charging on a hot summer afternoon. Then I realized the temp range was in centigrade. So in other words the lifepo4's operating range was much hotter that I could stand, and my hot garage was actually only kinda warm to my battery. Some will chime in that I shouldn't but I charge in the hot garage all summer without worrying about it, and my pack has lasted fine.

 

[liveforphysics]

The heating is a direct product of the Ri * current^2. Big cells, weak little currents in and out, and the heating is going to be very minimal.

The hotter a cell gets (up to it's safe high temp limit), the better it performs at charging and discharging.

This is why production EV's are often fitted with systems to heat the pack before discharging.