Chargers
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The standard supplied NiMh charger with eZee bikes is a sound reliable charger with adequate 53 volt headroom and full temperature control of charge termination, but it cannot carry out the occasional discharging that NiMh batteries need to keep them in prime condition for the longest life. This has to be inconveniently carried out by riding the bike until the battery is nearly empty with the risk of running out on the road.
A better method is to use a charger with a discharge function that can take the battery cells nearly down to 1 volt each. A possibly desirable facility is the ability to maintain a small trickle charge at the end of charge to cancel the natural loss of 1% to 1.5% of charge each day while a charged battery is unused. I've identified and thoroughly tested
A better method is to use a charger with a discharge function that can take the battery cells nearly down to 1 volt each. A possibly desirable facility is the ability to maintain a small trickle charge at the end of charge to cancel the natural loss of 1% to 1.5% of charge each day while a charged battery is unused. I've identified and thoroughly tested
a very reasonably priced charger that can do just that, of particular relevance to anyone wanting a a second charger, switching to NiMh from Li-ion, or just wanting to buy one to get the best from each battery, and it's illustrated at the right. It performs the full, charging function in exactly the same way as the standard charger, fan cooled while doing it, but has the option of pressing the red button at the outset to discharge the cells to refresh them. The operation is fully automatic. When the button is pressed, discharging commences and the fan speeds up to dissipate the heat from that. Once discharged, it reverts to charging and takes exactly five hours from empty to full charge. On completion of charge it automatically maintains a small trickle charge. Full technical details are in a separate section at the foot.
The status is displayed by two LEDs at all times, left hand one Charge, right hand one Power as seem on the photograph. Discharging shows red-red, charging shows red-green, charge complete and trickle charge shows green-green. Flashing LEDs indicates a fault status such as a poor connection, but I've never seen that at any time. The charger can be bought from the specialist US company Powerstream, and the exact cost for UK users will depend on exchange rates. With the very favourable current rate, the total amount charged to my credit card was £41.74 including P & P via US Postal Express service which took 12 days to reach me. The breakdown of cost was charger: £28.20, P & P: £13.54, all quite a bargain for such a capable product. If I'd chosen the basic Priority postal service my total cost would have been down to just £36.35 for charger and P & P. I've had considerable experience with the 24 volt version of this model on Lafree bikes, as have many other users following an earlier recommendation, so I can vouch for the reliability. You will need to solder on an XLR connector to suit the eZee battery, and there's full illustrated details below on doing that.
When ordering, the link is only to the home page, so click Battery Chargers at the left, then scroll down and click on NiMh and Ni-Cad Charger Index, then scroll down to the 36 volt NiMh etc charger, part number PST-3PN9545-36 and click on it. When you proceed to the checkout, you'll see a very high total price due to it being with a UPS Expedite service, well over doubling the cost. If you don't see alternatives, click the recalculate button and then from the list choose an alternative. Powerstream
The XLR plug can be bought from Maplin on this page, and if you scroll down you'll be able to enter your post code and be shown the local stores with their stock of this item, plus the distance in miles from your home.
When ordering, the link is only to the home page, so click Battery Chargers at the left, then scroll down and click on NiMh and Ni-Cad Charger Index, then scroll down to the 36 volt NiMh etc charger, part number PST-3PN9545-36 and click on it. When you proceed to the checkout, you'll see a very high total price due to it being with a UPS Expedite service, well over doubling the cost. If you don't see alternatives, click the recalculate button and then from the list choose an alternative. Powerstream
The XLR plug can be bought from Maplin on this page, and if you scroll down you'll be able to enter your post code and be shown the local stores with their stock of this item, plus the distance in miles from your home.
Here's the connection details, plus added information for those who are a bit uncertain about their abilities. The charger comes with a NTC connector which you need to unassemble and then unsolder the connections. That leaves the wire ends exactly right for connecting to your XLR plug, needing no trimming.
Remove the two clamp screws and body screw from your XLR plug to expose the connection block shown at the right. The colour codes and the correct points to connect to that are as shown, (blue negative, yellow/green thermistor, brown positive).
Remove the two clamp screws and body screw from your XLR plug to expose the connection block shown at the right. The colour codes and the correct points to connect to that are as shown, (blue negative, yellow/green thermistor, brown positive).
Before soldering on the wires, make sure you've put the other XLR plug parts onto the lead as shown at the right, first the rubber grommet (1) the right way round, then the body (2) as shown, last the clear insulating sleeve (3), cone larger side towards the cable end. When soldered, slide the clear cone over the three solder connection tags, then slide on the metal body and tighten it's screw firmly, finally twist in the grommet head and replace the cable clamp and screws.
Some tips for those nervous about the soldering part. Tin the three connections on the XLR plug by applying the soldering iron and a little electrical solder first, and also re-tin the three wire ends with a little fresh solder. Then the wires will solder onto the tags easily with just the soldering iron application. Since you need one hand for the wire and one hand for the soldering iron, a simple way of stopping the connector skating around is to put it in the rounded opening in the jaws of a pair of pliers, held closed with a rubber band as shown here.
The discharge rate is less than one fifth of an amp, so the discharge function is best used on a battery that is already fairly low on charge so the discharge doesn't take too long. Since discharging and recharging is a slow process, make sure there's enough time to do it overnight if you need the bike first thing in the morning, and for many it might be best done at the end of the week when the bike isn't needed early the next day.
Caution: Manufacturers do not recommend continuous trickle charging. Therefore I won't recommend it's use over sustained periods, though the period following a charge, which could be a few hours with an overnight charge is perfectly safe. For more on this see the foot of the technical section.
Technical
This charger is made for Powerstream by specialist company Shenzhen. The full technical specification is shown on the order page, but here are I'm showing the main factors in comparison to my standard eZee charger, eZee figures in brackets:
Peak charge voltage: 56 (53).
Output current max: 2 Amps (2 Amps)
Battery capacity range: 3 A/h to 17 Ah (not known).
Battery voltage at end of charge: 43.9 (44.2).
Cell voltage at end of charge: 1.463 (1.473). ( 1/100th volt difference negligible)
Discharge termination battery voltage: 31.8 (N/A, no discharge on the eZee charger).
Discharge termination cell voltage: 1.06 (N/A)
Above ambient case temperature degrees C at end of charge: 11 (11).
Thermocouple checked.
Thermistor matching: R25 = 10k, B = 3950 (R25 = 10k, B = 3435).
As can be seen, the Beta factor doesn't match, but the Shenzhen charger is specifically designed to be generic. As the technical will appreciate, the beta factor is not everything, the RT curve, that is the change of temperature over time, is what really matters. The chargers response takes care of a wide range of differing beta factors to fit it's generic role. It has three charge termination methods. First is the temperature rise (dT/dt), then the ultimate temperature, limited to less than 50 degrees C, finally the peak cell voltage, limited to less than 1.59 volts per cell.
In practice, the charge on the eZee battery terminates on the first, the temperature gradient, and with the leisurely full charge of 5 hours, the battery is given an easy time.
The trickle charge mode on this charger is of the preferred pulse type, giving one pulse of less than a second in each three second period, the pulse strength regulated by the cells resistance. In addition, the average trickle rate of charge is below the recommended safe rate of C.05. In practice the pulses vary between 190 and 310 mA net, averaging about 270 mA. With the pulse duration less than 1 second in 3, the average charge rate is always below C.045. Use this mode at your own risk of course, since cells vary and what might be ok with most batteries could catch out the odd one.
Caution: Manufacturers do not recommend continuous trickle charging. Therefore I won't recommend it's use over sustained periods, though the period following a charge, which could be a few hours with an overnight charge is perfectly safe. For more on this see the foot of the technical section.
Technical
This charger is made for Powerstream by specialist company Shenzhen. The full technical specification is shown on the order page, but here are I'm showing the main factors in comparison to my standard eZee charger, eZee figures in brackets:
Peak charge voltage: 56 (53).
Output current max: 2 Amps (2 Amps)
Battery capacity range: 3 A/h to 17 Ah (not known).
Battery voltage at end of charge: 43.9 (44.2).
Cell voltage at end of charge: 1.463 (1.473). ( 1/100th volt difference negligible)
Discharge termination battery voltage: 31.8 (N/A, no discharge on the eZee charger).
Discharge termination cell voltage: 1.06 (N/A)
Above ambient case temperature degrees C at end of charge: 11 (11).
Thermocouple checked.
Thermistor matching: R25 = 10k, B = 3950 (R25 = 10k, B = 3435).
As can be seen, the Beta factor doesn't match, but the Shenzhen charger is specifically designed to be generic. As the technical will appreciate, the beta factor is not everything, the RT curve, that is the change of temperature over time, is what really matters. The chargers response takes care of a wide range of differing beta factors to fit it's generic role. It has three charge termination methods. First is the temperature rise (dT/dt), then the ultimate temperature, limited to less than 50 degrees C, finally the peak cell voltage, limited to less than 1.59 volts per cell.
In practice, the charge on the eZee battery terminates on the first, the temperature gradient, and with the leisurely full charge of 5 hours, the battery is given an easy time.
The trickle charge mode on this charger is of the preferred pulse type, giving one pulse of less than a second in each three second period, the pulse strength regulated by the cells resistance. In addition, the average trickle rate of charge is below the recommended safe rate of C.05. In practice the pulses vary between 190 and 310 mA net, averaging about 270 mA. With the pulse duration less than 1 second in 3, the average charge rate is always below C.045. Use this mode at your own risk of course, since cells vary and what might be ok with most batteries could catch out the odd one.
Li-ion Charger
It's important that only the manufacturer's supplied charger is used on the eZee batteries, the dangers of using an incorrect one are considerable and could include personal injury.
Conversely, in an emergency, the eZee Li-ion charger can be used to partially charge the eZee NiMh battery. Since this charger's peak voltage is only 41.4 volts, it will only take the NiMh battery to around two thirds charge, with the exact amount varying, but it could be a useful in some circumstances.
For example, someone who has switched from Li-ion to NiMh batteries might be able to use their Li-ion charger at their workplace to add a little top up charge on the NiMh battery for the return journey.
It's important that only the manufacturer's supplied charger is used on the eZee batteries, the dangers of using an incorrect one are considerable and could include personal injury.
Conversely, in an emergency, the eZee Li-ion charger can be used to partially charge the eZee NiMh battery. Since this charger's peak voltage is only 41.4 volts, it will only take the NiMh battery to around two thirds charge, with the exact amount varying, but it could be a useful in some circumstances.
For example, someone who has switched from Li-ion to NiMh batteries might be able to use their Li-ion charger at their workplace to add a little top up charge on the NiMh battery for the return journey.
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10.11.2007
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