I have been experimenting with Poweriser’s 18.5 volt 10 amp LiPo as a substitute power pack for the 16.8 volt 8 amp NiMh supplied as standard with the Dahon Roo El 20” folder (Sram Sparc motor system).
To install the LiPo, up-end the battery box and remove the four sunken screws. Remove the box lid and disconnect the NiMh pack from the small circuit board (the red and black wires from the pack to the small white plug – this is locked and requires the insertion of a small screwdriver at its back to unlock it). Remove the large spring clip which holds the pack in place and lift out the NiMh pack.
Before fitting the new LiPo pack, drill a hole in the side of the battery box to accept the black two pin charging socket which is connected to the pack. This should be secured in place with super glue or epoxy resin adhesive.
The Poweriser 18.5 volt 10 amp LiPo fits nicely in the box and can be held in place with the large spring clip. The red and black discharge wires from the pack have then to be fitted to the discharge circuit on the circuit board (red to the left and black to the right). I used spades and heat shrink insulation. It is important that they should not come loose, and highly advisable to leave the insulation which comes with the pack in place on one wire while working on the other wire. A short across these two wires will have a disastrous outcome for the battery and will seriously disturb the installer’s equilibrium!
The small charging wires which connect between the right side of the circuit board and the original NiMh charging socket at the base of the box can be left in place, being now redundant.
I have found that the LiPo gives about the same range on the Roo El as the NiMh, namely 15 to 20 miles with the motor always on (ie road speed between 2 mph and 15 mph, and pedals always turning), and up to 30 miles range with the motor only on intermittently eg for gradients. However although the LiPo costs twice as much as the NiMh it weighs 1 kilogram less (pack and box weigh 1.6 kg against 2.6 kg for the NiMh). Therefore if the battery runs down (the inbuilt cut-off stops discharge at 15 volts – measured across the discharge terminals without load) the bicycle, now weighing 17 kgs against 18 kgs with the NiMh, is quite easy to pedal. Or a second battery can be easily carried in the saddle bag and switched over at the half way stage.
The only drawback I have found with the combination of the Poweriser 18.5 volt 10 amp pack and the 1.5 amp smart charger is that it takes 9 hours for a full charge (21 volts across the discharge terminals without load), but it will reach 18 volts or thereabouts in about half that time which is the time it takes to charge the NiMh with the Dahon 2 amp charger.
With the LiPo having a nominal voltage of 18.5 volts and the NiMh 16.8 volts there is small degree of over voltage which has quite a noticeable effect on speed and acceleration when the battery is fully charged. On the flat this means that the cut-off speed of 15 mph is reached in a shorter time, thus reducing the motor-on and battery-discharge periods.
I would recommend the Lipo for the weight saving alone. Taking 1 kilogram off an 18 kilogram bicycle makes quite a difference and helps maintain the Roo El's claim to be the lightest electric bicycle available.
To install the LiPo, up-end the battery box and remove the four sunken screws. Remove the box lid and disconnect the NiMh pack from the small circuit board (the red and black wires from the pack to the small white plug – this is locked and requires the insertion of a small screwdriver at its back to unlock it). Remove the large spring clip which holds the pack in place and lift out the NiMh pack.
Before fitting the new LiPo pack, drill a hole in the side of the battery box to accept the black two pin charging socket which is connected to the pack. This should be secured in place with super glue or epoxy resin adhesive.
The Poweriser 18.5 volt 10 amp LiPo fits nicely in the box and can be held in place with the large spring clip. The red and black discharge wires from the pack have then to be fitted to the discharge circuit on the circuit board (red to the left and black to the right). I used spades and heat shrink insulation. It is important that they should not come loose, and highly advisable to leave the insulation which comes with the pack in place on one wire while working on the other wire. A short across these two wires will have a disastrous outcome for the battery and will seriously disturb the installer’s equilibrium!
The small charging wires which connect between the right side of the circuit board and the original NiMh charging socket at the base of the box can be left in place, being now redundant.
I have found that the LiPo gives about the same range on the Roo El as the NiMh, namely 15 to 20 miles with the motor always on (ie road speed between 2 mph and 15 mph, and pedals always turning), and up to 30 miles range with the motor only on intermittently eg for gradients. However although the LiPo costs twice as much as the NiMh it weighs 1 kilogram less (pack and box weigh 1.6 kg against 2.6 kg for the NiMh). Therefore if the battery runs down (the inbuilt cut-off stops discharge at 15 volts – measured across the discharge terminals without load) the bicycle, now weighing 17 kgs against 18 kgs with the NiMh, is quite easy to pedal. Or a second battery can be easily carried in the saddle bag and switched over at the half way stage.
The only drawback I have found with the combination of the Poweriser 18.5 volt 10 amp pack and the 1.5 amp smart charger is that it takes 9 hours for a full charge (21 volts across the discharge terminals without load), but it will reach 18 volts or thereabouts in about half that time which is the time it takes to charge the NiMh with the Dahon 2 amp charger.
With the LiPo having a nominal voltage of 18.5 volts and the NiMh 16.8 volts there is small degree of over voltage which has quite a noticeable effect on speed and acceleration when the battery is fully charged. On the flat this means that the cut-off speed of 15 mph is reached in a shorter time, thus reducing the motor-on and battery-discharge periods.
I would recommend the Lipo for the weight saving alone. Taking 1 kilogram off an 18 kilogram bicycle makes quite a difference and helps maintain the Roo El's claim to be the lightest electric bicycle available.
