PaulC

I would reinforce Mary's comments on tyre pressure - the harder and more inflated the tyre is, the less rolling resistance. When GM built their first electric car back in the 1990s and tested it, they found they could add a noticeable improvement in range by using a special tyre with low rolling resistance. Paul

Hi, I'm surprised no one has mentioned the thief equation when comparing the two styles of bike: Man's electric bike = Thief magnet Girly electric bike = Not a thief magnet My personal preference is for the step-through electric bike but that is because I do 80% utility cycling so lots of stops and starts are easier with this style. Paul

Hi, I would recommend a book that may only be available secondhand. It is "The Bicycle Repair Book" 2nd Ed 1994, by Rob van der Plas. He covers both derailleur and hub gears, and I have found it to cover all parts of bikes. There is nothing on electric bikes, but then I would recommend this forum for electric problems. Paul

The obsolete 24Volt Merida electric bike that I bought cheaply (their demo model) from one of the two e-bike dealers in NZ did not come with the original set of 2x12Volt 9AH SLA batteries. The original batteries had died of old age so the dealer replaced them with 2x12Volt 12AH SLA batteries which were too large to fit in the bike's battery container. Instead he fitted one battery in the container and the other battery was tied to the top end of the rear carrier /luggage rack. The battery on the carrier rack has 2 thick copper wires from its terminals going back into the battery container (through a small hole) where I assume they are joined up to the wiring. That way the container has no large holes or cuts in it. The power range is increased as well. This works OK for me as I use panniers that clip on the side of the carrier rack, so I have never used the carrier top for anything. Sorry but I don't have pictures to show you what this looks like, Paul

Hi Wizard, I couldn't find your exact make of SLA charger on the Internet but I suspect from the current rating that it is a standard chinese electric scooter charger that has been rebadged so it would be very similar to the Currie one I had. Here are my charging stats which I have made independent of the battery voltage so it would apply to your 36V SLA battery. My remaining 10AH battery capacity at start of charging was between 50% and 70% (approx= 37.5 volts) so it took 2.5 hours before the green light came on. The charging current at the start was 1.7Amps and had dropped to 0.7A when the green light came on. It took another 1.75 hours before the current dropped to 0.1A (=1% of 10AH) so the battery was at full capacity. My bike manual says the green light indicates 90% charged so what I do now is charge until the green light comes on and then I give it another hour before I stop charging to take it up to somewhere between 90% and 100% of charge. As a guide, you can always roughly assess how much capacity remains in your battery by measuring the voltage while the bike is not turned on. Here is a simple approximate table: 36V = 20% -> 35% 37.5V = 50% -> 70% 38.5V = 75% -> 90% 39V = 90% or greater. Hope this helps, Paul

Hi, what is the make and model of the charger? My own experience with a Currie SLA 24Volt charger and an upmarket SLA 24volt charger on 10AH batteries is that the green light comes on when the battery is charged up to around 80-90% of capacity. General rule of thumb (as per the good PowerTech SLA battery guide) is that an SLA battery is fully charged when the charging current has dropped to 1% of the Amp-Hours rating of the battery. For example, a 10AH battery is fully charged when the charging current is 100milli-Amps or less. Charging time is quite dependent on how discharged the SLA batteries were. If your batteries were only around 50% discharged, then 3 hours before the green light comes on is about normal. I can supply the charging stats for my 24Volt 10AmpHour (AH) batteries if you like. Paul

From memory, I believe that Nicad and NiMH chargers use a constant-current approach. Cheap chargers just have a timer in them and run for, say 15 hours, inputting a constant amount of current and then stop. Hopefully the battery is fully charged but if it was only half-discharged at the start of the charging cycle, then it will be overcharged. This approach works well for the likes of tradesmen with 2 battery packs for a drill where they run 1 pack to fully discharged before switching to the other pack and placing the discharged pack in their charger. More expensive smart chargers are paired with their battery packs - the battery pack has a temperature sensor in it which feds back the temperature behaviour of the battery pack during charging to the charger. When a Nicad or NiMH battery pack reaches full charge, then a temperature spike occurs inside the pack. The charger sees this spike and knows to stop charging the battery pack (voltage with Nicads and NiMH is not as reliable an indicator of full charge as it is with SLA batteries). The above is why when a smart NiMH charger dies, care must be taken in selecting a replacement charger. Paul

The Currie 24V SLA charger is the same as the IZip 24V SLA charger so you could try http://www.electricbicycles.co.uk for a new one. Alternatively, try EVdeals.com, Electric Scooters, Bikes, Parts! in the USA who seem to be a major supplier of replacement parts for Currie prodrives. I analysed the charging characteristics of this charger and it is a cheap (it is basically an LM317 constant voltage=29.3volts, current limited circuit) charger that will shorten the life of any SLA batteries it is used on if not disconnected in time; if disconnected too early it will fail to fully charge the battery. Paul

On my Shimano Nexus 4 speed hub I find that it is essential to do a slight back-pedal (as described above) when changing down gears (e.g. 3 ->2) but I don't need to do this back-pedal when I am changing up gears (e.g. 3 ->4). Paul

I have a Merida powercycle 550 (from around 2003). This is like the LaFree because the power assistance from the electric motor is via a set of cogs linked to the pedal crank. The rear wheel has a Shimano 4 internal gear hub. The amount of electric power supplied is controlled by a combined torsion + pedal crank rotation rate sensor. When I pedal slowly with heavy pressure on the pedals in any gear, I get the maximum amount of assistance from the electric motor. As my pedal cadence speeds up, the amount of assistance drops off and then the electric motor stops once I go over a certain pedal cadence (regardless of the gear I am in). This is the 15mph speed restriction standard to ebikes. There is an explanation of all this in a patent description available online (merida electric bike patent) but it is difficult to follow. I find it works OK but there does not seem to be any way to turn off the pedal cadence limit Paul

Here in New Zealand it is compulsory for all cyclists to wear helmets, and 99% of cyclists comply with this. It becomes second nature after a while to put on a helmet as part of getting ready for a cycle (like seat belts in cars) Given that NZ drivers are among the worst in the world, every bit of extra safety helps! Paul

A View from the Antipodes I have to agree with Frank about how a single country dealership for electric bikes can be bad as well as good. Here in New Zealand, the eZeebike franchise is held by a firm whose main line is spa pools and outdoor garden furniture, with ebikes as a sideline. When I visited, their stock was outdated old models (Sales of ebikes are slow in NZ). I asked if they would import a Liv and got told "No, we only do top of the range eZee models as special orders". I came away with the impression that it would be high risk to buy an ebike from them as the batteries would most likely be expired from old age, and I would feel nervous about after-sales support. Apart from that, there really aren't any "real" electric bike dealerships in NZ. The only other ebike dealership has changed to selling Crystalite kits and Chinese e-scooters as purpose-built ebikes sell so slowly. Paul

Flecc, thanks for the reply. I think I'll be there doing measurements judging by the lack of replies. Oh well, them's the breaks. Paul

Info needed from IZip / Currie owners - SLA charger info? Hi, I have a 24V Currie charger for the 2x12V=24v SLA batteries on my electric bike. Its model number is 3A-501DA24. It has 1 green LED. When the charger is actively charging this LED flashes green; when the battery is fully charged, the LED shows a solid green light. Would someone be able to tell me what the charging behaviour of this charger is from the IZiP / Currie ProDrive manual? I am hoping that it is the following: LED flashing - charger has a high output voltage that results in an intensive charge current into the batteries. LED solid light - charger has recognised the batteries are charged and dropped its output voltage down to a trickle or float voltage. I am hoping to avoid doing an experiment where I measure the voltages over the charging cycle myself as I don't have a data logger and would have to do this by manual measurements. Thanks Paul New Zealand

Removing brake from SRAM 7 speed hub If you have not already bought this hub, then it is possible to get a 7speed Shimano Nexus hub without any internal brakes. If you already have the bike with the SRAM 7speed hub, then the brake can be disabled by removing the cable. However, you will still be stuck with the external brake housing (including the metal arm that has to be clamped to the bike frame) as this is part of the overall hub axle spacing and provides some weather shielding for the axle bearings. Paul