Urban Mover Nimh 8ah

[bluebus]

Hi All,

I was recently given a non running urban Mover UM44 with the older type Nimh 24v 8 ah battery.

first thing I charged the battery which was showing full power on the battery indicator light when disconnected. I have checked the 24v battery after a charge which is reading just over 20v at the power connections and on further inspection each set of 3 x D cells are reading on average 3.3 v (or 1.1v per cell). The battery is composed of 20 of these D size rechargeables. I believe the bike is out of use for a number of years but was functioning when retired.

My question is has this battery pack had it or is there any way of reviving the cells? If the pack is indeed a large paper weight would users suggest replacing the existing cells with Nimh or upgrading to a similar size lithium battery.

your help and advice is much appreciated.

 

[WheezyRider]

Hi All,

I was recently given a non running urban Mover UM44 with the older type Nimh 24v 8 ah battery.

first thing I charged the battery which was showing full power on the battery indicator light when disconnected. I have checked the 24v battery after a charge which is reading just over 20v at the power connections and on further inspection each set of 3 x D cells are reading on average 3.3 v (or 1.1v per cell). The battery is composed of 20 of these D size rechargeables. I believe the bike is out of use for a number of years but was functioning when retired.

My question is has this battery pack had it or is there any way of reviving the cells? If the pack is indeed a large paper weight would users suggest replacing the existing cells with Nimh or upgrading to a similar size lithium battery.

your help and advice is much appreciated.

It might be possible to get it going again. It may be that some of the cells have died, so really you need to look at the voltage of each individual cell. Nominal voltage of these cells is 1.2V and something like 1.35 OCV when fully charged.

 

[Nealh]

At 1.1v per cell look at a lithium replacement, the controller shouldn't be an issue but make sure you buy a new charger with the battery.

 

[vfr400]

Lithium batteries are lighter, cheaper and give more range. You can buy a 24v cell-pack from Aliexpress that will fit into your existing case.

If it were my bike, I'd get rid of all the electrics except the motor and upgrade to 36v with a modern controller. 36v will give the bike 50% more power without any downside. Those bikes were gutless at 24v.

 

[WheezyRider]

If you can afford it, go for the lithium conversion, the result will be a lot more satisfactory. If not it's a case of trying to revive any dead cells.

 

[Nealh]

With my Swizzbee #2 I simply replaced the Nimh with lithium celled packs of my own build, utilising the original controller.

 

[bluebus]

Thank You so much for all your advice and guidance. Strangely the cells in the battery pack have increased voltage from 1.1v after charging to a healthier 1.30v 7 days later. The pack is now reading 26v after reading c. 20v for 6 days running. Will try pack back on the bike but definitely like the idea of upgrading to lithium in the near future! I have the feeling this revival of cells may be short lived and related to temperature increasing in the garage

 

[Danidl]

Been there as it were and have the teeshirt. I still have an UM 22 7 speeds small wheel bike .. foldable from about Match 2007 ,I think . It gave sterling service for about 3 years on the original battery. In and out to work 3 to 4 miles each way ,5 days a week. Saved itself on car parking charges. Then I attempted to build up my own NimH pack when the battery was only good for 3 miles , with mixed results .. yes it worked but occasionally unreliable. I sought out li ion alternatives , but the space available for mounting the pack , on a foldable never worked with any available commercial units. However, there was a model called Frog , Purchased the 28v version, removed the battery mounting plate, and wired up the frog assy on a bracket above the rear carrier. The replacement was nominally 10amp hours, and worked a treat for another 3 years but by now is down to short hops only. The only problem is that the led indicators of battery consumption as fitted on the throttle display are wrong when the li ion are usef.