wisper 14ah battery 706 alpino

[dmcgoldrick]

hi , there have been a few battery questions recently so this is just a brief note of todays outing......

freshly charged new battery

started at 240 ft......climbed to 1200 ft over 6km........
freewheeled (braking all the way !!) back down to about 200ft another 4km....

then did a mild undulating run of 28 km....

time taken 1 hour 45 min for the total 38 km.

had assist on full.........

battery looks to still be at half.......

will see how this battery performs from where it is without recharge.... if weather holds over the weekend....need to run it down.........

regards

 

[Wisper Bikes]

Enjoy your ride today David, I am jealous, riding through the Scottish country side.... perfect! I hope the weather is as good as it is here, I can actually see the sun, I also notice the grass needs cutting!

Regards

David

 

[dmcgoldrick]

hi , there have been a few battery questions recently so this is just a brief note of todays outing......

freshly charged new battery

started at 240 ft......climbed to 1200 ft over 6km........
freewheeled (braking all the way !!) back down to about 200ft another 4km....

then did a mild undulating run of 28 km....

time taken 1 hour 45 min for the total 38 km.

had assist on full.........

battery looks to still be at half.......

will see how this battery performs from where it is without recharge.... if weather holds over the weekend....need to run it down.........

regards

Part Two.......

started off on the flat and cycled about 2 km before first small incline........
assist was still on max........battery cut out and warning code 04 appeared
04 flashes
Battery voltage is too low.

Dropped assist level to half and after about 10 seconds assist came back in.
On the level again for another 2 km running ok, but as soon as slight incline ,got same 04 flashing. Turned back as steep incline ahead. Ran another 8km on level with 04 coming on regular....10 seconds then assist back on for short time. battery indicator still showing 2 green lights...ie half full.
Put bike up on workstand and it has run on full assist for another 20km at 27km/hr without any load of course........and is still running !!!!!!

conclusion........although battery showing half full and power without load running motor.......power insufficient to assist bike even on slight incline....

question......is there any way to access the voltage which is still in the battery to give good assist on inclines and increase range ????

regards

 

[dmcgoldrick]

Part Two.......

started off on the flat and cycled about 2 km before first small incline........
assist was still on max........battery cut out and warning code 04 appeared
04 flashes
Battery voltage is too low.

Dropped assist level to half and after about 10 seconds assist came back in.
On the level again for another 2 km running ok, but as soon as slight incline ,got same 04 flashing. Turned back as steep incline ahead. Ran another 8km on level with 04 coming on regular....10 seconds then assist back on for short time. battery indicator still showing 2 green lights...ie half full.
Put bike up on workstand and it has run on full assist for another 20km at 27km/hr without any load of course........and is still running !!!!!!

conclusion........although battery showing half full and power without load running motor.......power insufficient to assist bike even on slight incline....

question......is there any way to access the voltage which is still in the battery to give good assist on inclines and increase range ????

regards

part three, left motor running with bike on bike stand a good while longer(2hours), battery indicator down to one green light, mileage up another 50km...so thats 3 hours running free and battery still not empty..........
have stopped now and put on an overnight charge.....so there is obviously lots of voltage in the battery when it stops giving assist under load on inclines.......
is there anything which can be modified to access this voltage to give uphill assist ? wisper 706 alpino 14ah battery (new)............
regards

 

[flecc]

The consumption when not under load is miniscule, so the motor will free run for very many hours without draining the battery. Trying to drain it that way is usually a wasted effort.

The safe low voltage of a 36 volt lithium battery is about 31.5 to 32 volts and access below this is blocked to prevent damage to the cells. This low voltage setting is in part due to the fact that cells can discharge unevenly and that is not managed by the BMS, only the charging is, not the usage. The 31.5 to 32 volts generally ensures that no individual cell goes down to a destruction level.

In addition, cell life depends on the chemical stress they are exposed to. The stress is at it's greatest in the lowest and highest regions of charge, so the lower limit prevents the discharge getting into the most damaging region. Equally the charging is terminated before the battery is completely full to prevent use of the upper most damaging region. If a very short life was acceptable your battery could contain about 20% more charge, and on the other hand, if only the central 60% of charge was used and the current usage rate was always at the lowest power setting on the bike (Eco), the battery might last several years.
.

 

[dmcgoldrick]

The consumption when not under load is miniscule, so the motor will free run for very many hours without draining the battery. Trying to drain it that way is usually a wasted effort.

The safe low voltage of a 36 volt lithium battery is about 31.5 to 32 volts and access below this is blocked to prevent damage to the cells. This low voltage setting is in part due to the fact that cells can discharge unevenly and that is not managed by the BMS, only the charging is, not the usage. The 31.5 to 32 volts generally ensures that no individual cell goes down to a destruction level.

In addition, cell life depends on the chemical stress they are exposed to. The stress is at it's greatest in the lowest and highest regions of charge, so the lower limit prevents the discharge getting into the most damaging region. Equally the charging is terminated before the battery is completely full to prevent use of the upper most damaging region. If a very short life was acceptable your battery could contain about 20% more charge, and on the other hand, if only the central 60% of charge was used and the current usage rate was always at the lowest power setting on the bike (Eco), the battery might last several years.
.

thanks flecc, i now understand a lot more about how the battery will perform after this trial, and your excellent explanation on why voltage remains but may not be available under load.

regards

 

[Wisper Bikes]

Hi David and thanks Tony.

The control system on our Dapu driven bikes (906, 706,806) is quite sophisticated.

As Flecc quite correctly says, the controller is set to cut power to the motor when it reaches 31.5V to stop the possibility of any damage to the cells. When this happens you will get the 04 error reading on the LCD display telling you why the power has been cut. On the flat the drain on the battery will be very much lower than on an incline so you will be able to keep pedalling after the 10 second re-set period, however as you have discovered if you hit an incline the safety system will cut in again.

You will find your range will increase quite dramatically as the weather gets warmer.

All the best,

David

 

[dmcgoldrick]

Hi David and thanks Tony.

The control system on our Dapu driven bikes (906, 706,806) is quite sophisticated.

As Flecc quite correctly says, the controller is set to cut power to the motor when it reaches 31.5V to stop the possibility of any damage to the cells. When this happens you will get the 04 error reading on the LCD display telling you why the power has been cut. On the flat the drain on the battery will be very much lower than on an incline so you will be able to keep pedalling after the 10 second re-set period, however as you have discovered if you hit an incline the safety system will cut in again.

You will find your range will increase quite dramatically as the weather gets warmer.

All the best,

David

hi david, many thanks for confirming this....good to be able to correlate what i am finding with the technical reasons......
if you ever get a 'Da Hub mountain goat' battery, this is the place to test it out......
dont need to go to to NZ to find some good hills ........(still got snow here while you are enjoying spring !!!)

regards

 

[Wisper Bikes]

still got snow here while you are enjoying spring !!!

Hi David,

It is nice to see the spring flowers popping up everywhere, but it comes at a cost..... I had to cut the grass at the weekend!

All the best

David