Conditioning a new battery - what to *really* expect in range

[DynatechFan]

This is a question that crops up and different advice seems to come forth, I wondered what current thinking is in terms of caring for a new battery and whether I should have shown battery size more concern for my first build

My ebay kit is up and running (350W hub motor with 36V 10.4Ah battery) and my typical commute is 12 miles (there and back) with 700ft of climbing (some of it 10%+ so a bit steep). Fully charged, first trip I got approx. half full battery (if the LCD3 is to be trusted) on my return - which is less than I expected and noticeably less than I was getting with a Merida e600 Steps fitted bike which could easily do 2 return trips. One variable is temperature, its been barely above zero Celsius here recently

Current plan is to recharge after every use to avoid the risk of deep cycle. Can I expect the battery to get better in use? Should I have bought a bigger battery?

 

[DynatechFan]

Actually it has occurred to me there are choices in the charging regime too. Right now I plug the battery in when I get home and unplug it a few hours later.

Is it bad to leave a battery on charge for hours once its full?

Would it be better to put the charger on a timer and have it turn on at 4am so the battery is full at 8am on the day I need it, or is it okay to fill it up and leave it full till I need it (which can be days)?

 

[anotherkiwi]

No it will balance then stop charging.

It is best to put it on the charger before you go out, don't leave it fully charged for a long time, leave it at about 38.5v. Once you know how long it takes to charge from 38.5v to 42v you can put it on a timer. You should charge even Li-ion batteries in a safe place btw.

 

[awol]

My battery struggles a bit in colder temperatures too.
Just fully charge it each day, as there is more power in the higher voltages which is handy in the morning.

 

[Nealh]

There is little capacity between 4.1 & 4.2v and what there is disappears very quickly.

 

[Deleted member 4366]

350w doesn't mean anything. The power comes from the controller. How many amps are written on it?

The speed of the motor affects the efficiency a lot - not the speed you ride, but the motors maximum no-load speed. Lift the wheel off the ground, spin the motor up to its maximum (unrestricted) and tell us what the speed is.

 

[DynatechFan]

thanks folks - just popped to the garage in my tea break, the display, assuming it is correct, tells me:
fully charged battery is 41.2V
max motor power spinning pedals on #5 is c430W at #4 seems to be c250W
no load speed is approx 42kmh (might be more but its not an easy test solo)

The controller looks to be a 250W(?), it says:
KT36ZWSR:EP01
Rate 7A Max 15A =/-1A

 

[Deleted member 4366]

430w is very low. That's only 11 amps. Most 250w controllers are around 15 amps at 36v, so you'd see around 600w on level 5.

42km/hr is relatively fast for a motor with only 11 amps. The low current means that it will spend a lot of time in it's inefficient zone (lower than 21km/hr), which might explain your lower range.

You only get maximum current when the motor is under high load at lowish speed, so check your watts again next time you go up a hill. I would expect a 350w 36v system to show 800 to 900 watts.

Basically, the poor range you're getting is because your motor is too fast for its power, so it's not running at optimum efficiency. If you do a lot of climbing, you'd be better off with a slower motor - say around 250 rpm or 20 mph (32 km/h).