Battery charging

[Rodmiami]

  I would like to know if I should leave my battery on charge all the time or should I unplug it when the light goes green . Its a new battery and I don't want to shorten its life span . Thanks Rod

[Bikemad]

Rod,

If you're going to be using it regularly, it might be better to leave it on charge in between use to ensure it's kept topped up and ready to go.
The BMS will prevent if from becoming overcharged, and the cells should remain nicely balanced

If it's not going to be used for long periods of time, it might be better to charge it overnight once a month instead of leaving it on continually.

If you normally experience very cold winters, it would be better to store it inside during the winter months as they don't like being charged at very low temperatures (they should always be above 0°C while charging).

Alan
 

[dBlues]

I suppose this means switching off the regen brake too for temperatures under 0C?

[Bikemad]

If you're riding your bike in temperatures below 0°C in icy conditions, you are less likely to go fast enough to produce much regen current.
I recently took my Smart Pie on a two to three mile off road ride while walking the dog at a more leisurely pace, and my bike's speed is unlikely to have exceeded 15 mph throughout the whole trip.

When I checked my Watt Meter after putting the bike away, I noticed that my maximum recorded regen figures were 13.5 Watts and 0.43 Amps, and the resting voltage of my 29.6V pack was just over 31V.

As the Smart Pie manages a maximum speed of around 18 mph on my 29.6V battery pack, I suspect that regen current is only really produced if the maximum powered speed is exceeded (i.e. >20 mph).
Although the motor's braking effect was noticeable on the downhill sections (even at very slow speed) I guess it's more of an electrodynamic braking effect rather than actual regenerative braking.

At higher speeds (without the dog) I have recorded 365 Watts of power with over 10.5 Amps of current, so I know the Smart Pie's regenerative braking does actually work if you go fast enough.

I'm sure that both my MPI and MPII produce regen current at much lower speeds than the Smart Pie does, but until I have an ammeter and speedometer installed (where I can easily see them) it's going to be difficult to prove.

I also suspect that the recorded 0.43 Amps of regen current may have been generated while whizzing down the back garden and then quickly braking to go around the side of the house, as I probably went a bit faster then, than I did during the trip.

Alan
 

[GM Canada]

What I do is have a shelf with all of my personal batteries not in use on it. I have my chargers all hooked to one power cord. That power cord is plugged into a heavy duty 7 day timer. Not sure if a heavy duty timer is required but that's what I have. The timer is set to come on every Friday at 1 am for 12 hours. That way its care free and my batteries are all topped up before every weekend. Weekends are the only time I need all my batteries as this is the time I ride some of my other bikes or I share them with my friends. My daily ride is plugged in separately after each ride. When winter comes those batteries join the others on the same shelf. Damn winter!

Gary

[dBlues]

As I understand, most LiFePO4 batteries should be dischargeable in temperatures -20C?

[Bikemad]

I have just been Googling again and found these details from a Chinese battery manufacturer:

Nominal voltage: 51.2V
Rated capacity: 10, 12 or 20Ah
Operating temperature: -20 to 60°C
Charging temperature: 0 to 45°C
Storage temperature: -20 to 45°C

As I could not find any information containing sub zero charge temperatures, I'm guessing that LiFePO₄ packs should also be above 0°C before charging.

Alan
 

[OldNick]

  I would like to know if I should leave my battery on charge all the time or should I unplug it when the light goes green . Its a new battery and I don't want to shorten its life span . Thanks Rod

I know what (little) I know from playing with RC stuff. Same batteries.

I may have missed something, but a lot depends on what type of battery and charger you have. If using LiPo, or even LiFePo I believe, you need a charger that monitors each cell, and will deal with each one to balance the cells in the battery. Without that, leaving the battery permanently on charge can be expensive or dangerous. LiPos are notorious for catching fire if one or more cells are dead or damaged, or even just at too low a voltage because of an imbalance and the charge is being forced in.

Both LiPo and LiFePo are very good at retaining their charge fro quite some time qithout being trickled, too.

Nick

[Morgen 3Eman]

Hi Rod,

I did some internet research on the subject not too long ago, and the consensus of manufacturers seems to be keep the battery charged between 20%-80% during long term storage at moderate temperatures. Frequent full charging  during storage may stress the cell and reduce the number of full capacity charge/discharge cycles. 

I admit to being an old fool, so trust your own research.  I am just monitoring the output voltage once a week or so, and when it drops to 53 volts, I charge my battery back up to 56 volts. 

TTFN,
Dennis

[OldNick]

Sorry. I hate these guys that post a question then never come back

Nick

[GM Canada]

Sorry. I hate these guys that post a question then never come back

Nick

I wouldn't worry about Rod coming back. It may take a little time though as he is retired and living the good life in Miami on his chopper beach cruiser.

Gary

[Rodmiami]

Gee OLDNICK , I didn't know that I needed to reply back to you . I asked a question , I got an answer . I hate people who need to keep a subject going even after it has been addressed . For your information I read the forum ever morning and I felt no reason to respond any further. Rodmiami

[Rodmiami]

  OLDNICK , If you look at my original post it was more than a year ago . I got my answer more than a year ago . I am not going to respond every time someone digs something up from the archives . We got our first cold front last week now the daily highs are only in the low 80's .     
 As Gary said I am enjoying my Nirve bike but I will have to spring for a new front wheel kit if I can be guaranteed that it will run in reverse so I can use the disc brake . It is scary letting people use the bike and not know how to stop it without shutting down the motor . I don't know whether to buy an MP3 or the Smart pie . I am leaning towards the Smart pie because of less weight and less magnetic drag . I will have to purchase another programing cord also . Rodmiami

[GM Canada]

Hi Rod,

You could take your bike to a professional metal fabricator and have a disk mount added to the correct side. I did plan on having calliper mounts added to both my front and rear wheels. But have come to realize the front wheel would most likely slide a lot. I find my Chopper stops well enough with regen on the front and a coaster brake on the rear. I still plan on a rear disk brake for the future. And going to a 6 or 7 speed freewheel.

Gary

[Rodmiami]

  Gary , I don't really have a problem with the braking . I ride on asphalt and concrete . The only time that I get in grass is when I cross a street from sidewalk to sidewalk . I probably could weld the front myself since I have a small welder but I would hate to mess up the chrome ,although the front fork is already starting to rust . I have thought about cutting the mount off the right and moving it to the left . As the Jimmy Buffett song goes ( Only Time Will Tell ) . Rod