• Ian Watts

500km later...

Well... I thought I should make a *quick* update.

Scoot-ee has now completed more than 500km since going back on the road after the conversion to electric. Nothing major to report (except the previous battery re-configuration work).

A video can be found < here > . This was my first foray into blogs, my first scoot conversion and now this is my first YouTube video; needless to say, I'm extremely anxious ! It does go a long way to proving though - if I can do it in my garage, so too can anyone else with a mind to do so !

Anyways, on a not so great a note, some of the in-use problems I had :

1: SSRs : I decided to use SSRs (Solid State Relays) to handle the power switching on Scoot-ee. I encountered a few issues here : SSR's dislike back EMFs and spikes and, like any other 'switch' they can't control inrush current (like when connecting the battery to the controller). There are also tons and tons of el-cheapo Chinese copies that are simply not up to spec / masquerading as 60A units when, in fact, they're only 25A or 30A internally !! I'm not making this stuff up, I actually stripped the third failure down - one 25A FET... That was it !! VERY annoying. (If I get time, I'll make a post about my work with this too). The inrush current is handled in many different ways. For me, being an electronics sort of chap, I decided to go down the NTC / PTC thermistor route. I contacted those really nice guys at Ametherm (Canada) and was re-directed to their European (UK) office. To cut a long story short I found (thanks to Tony Chedester - Canada and Eleonore Hofmann - UK and some formulae they supplied me with) that the AS32 5R020 does a great job providing inrush current limiting across the Hi-V (Controller) SSR as did a chunky 100v, 6A diode in reverse across the SSR to deal with back EMFs to the battery. Between these two components and a 'real' (not cheap Chinese copy) 100A DCDC SSR I have had no more inoperative SSRs for over 400Km now. Result !!

2: Charger : I found the charger (much like the controller) really didn't 'like' the instant it was connected to the on board batteries. Each time a connection was made a noticeable electrical 'crack' could be heard. A temporary way around this issue was to ensure the charger was connected to the mains and 'On' before connecting it to the batteries but... that was 'fiddly' and prone to error (forgetfulness). Anyways, once again, Ametherm and their formulas and data sheets came to the rescue. Once I'd fitted a suitable, in-line, inrush current limiter between the charger output and the batteries, the problem went away - permanently. Another Result !!

3: Batteries : I had initially designed my batteries to be 'long and thin, siting them above the motor (low centre of gravity etc), 20 x 18650 cells long and 4 cells wide (as per the previous posts). In fact, by the time I'd refitted all the fairings / seat panels, I found it almost impossible to remove and refit the battery packs. A redesign was required !! I redesigned (Sketchup) the packs to be 10 cells long by 8 cells wide. No mean feat re-jigging the packs / spot-welded connections... but... a days work and two days 3D printing time later, I now have new 2 x re-jigged packs. MUCH better. An additional unexpected 'plus' - the battery pack re-design would appear to enable me to fit 3 (as opposed to the designed-for 2) battery packs within the available area below the seat, the shorter / squarer batteries fit best further aft... which means I used the now 'spare' space ahead of them for the charger which no longer sits on a shelf above them. I've discussed all this in a previous post. All the above is neat and really works out well - day-to-day charger access isn't really needed - however, to the 'negative' bit - relocating the charger forward of the batteries basically 'hides' it away which means the red (charging) and green (charged / finished) LEDS are no longer visible ! So... I now need to add a remote / more visible Red/Green charging/charged LED. I'm currently thinking about a suitable site / method of doing this...

4: Range : There are two 20S4P packs fitted. Range though is (depending upon use) between 25km and 38km. 25km when driven REALLY hard, two up. Much better, up to 38km without any run-out-of-juice dramas, if my wife is in control or I select the 'Lo' Speed setting (you may remember, I wasn't sure why I would need 'Lo' but... I added the Hi/Lo switch some weeks ago) !!! I'm sure this could be bettered still BUT youngsters feel the need for speed and it doesn't really matter how often I tell them, the throttle grip appears to be a two stage switch for them (with no in-between) off / stopped and on / full speed !!!

5: Coulomb counter / Volt/Amp meter : We've learned to 'take it real-easy' and 'limp' home when the displayed voltage drops below 68V on the level and with no (or very little) acceleration ... Still 30plus Km for a 2Kw pack (around 30cents a re-charge) is brilliant ! I really do need to get onto that coulomb-counter... My logic here is to design an Atmel microprocessor based board that monitors voltage and input (charging) / output (motor / lights etc) current. I'm thinking a small micro-processor based board (once programmed / configured) should be able to display remaining Amps and, therefore, remaining Km. Either on a dedicated display or, this summer's job (if nothing else more urgent pops up) on the existing fuel gauge. When the gauge drops into the red, it's time to head for a recharge !!

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© 2017 Ian Watts