A123's
Hm.
The attachment ought to have worked.....
Trying again. It is comfortably 'sized', probably the script blocker in my browser decided to interfere!....
The A123's, are a modified LiPo battery, with some extra chemistry, improving their ability to stand high discharge currents in particular.
They are an interesting battery, but are small. To get a genuine 36v, you have to use 12 cells (the 3.6v/cell figure, is basically the 'just charged' number). The basic cell gives 2.3Ah, at 3.3v, so a pack of 12, gives you 39.6v 2.3Ah = 91Wh. They do genuinely perform better than most small LiPo cells, in terms of being able to maintain a larger percentage of this 'rating', when currents over 1C are drawn. So assuming your motor is around 200W 'continuous', so drawing about 5A (2.2C), they still give about 98% of this 'rating', and on hills, when your motor goes up to say 400W, and pehaps nearly 5C, they still give well over 90% of this rating. They can stand being discharged well down their power curve, without damage. But I think some people are a little 'overconfident' that they will self balance, so do give them a balance cycle if they have been used heavily.
I have tried them on the Nano, and on the 26" conversions.
Now I tend to be an 'assisted' rider, rather than an 'electric' rider, using the electric on hills, into headwinds, and sometimes for a fractional boost on pullaway in traffic. As an example, I rode a local 'loop' of roads, to visit a friend yesterday. Just over 15miles, and averaged 15.1mph. Given that the assist cuts out around 15mph, you can quickly realise that most of the ride is 'pedal powered'. Looking at the track graph, tells it's own story.
Basically. there is almost no time at all on the graph, spent between 0mph, and 12mph. There are then a number of sections on hills etc., at between 12, and 15mph. On the 15 miles ride, 11.8miles, was 'over' the speed where the assist cuts out, typically cruising at around 20mph, leaving 3.2miles with assistance almost certainly being used. This would agree well with the battery indicator, which had just dropped into the red under load (usually meaning you have about 1/4 left). I reckon on a single pack, giving around 5 miles of 'full assist' on flat roads (the cruising 200W ish output), but half this on reasonable gradients. There were two hills over 15% gradient on the ride, and both were done with full assist at about 12mph.
For me, having two batteries is great. You can leave the switch 'off', and ride as normal. Come to a hill, and hit battery one as needed. I don't think I'd be 'happy' riding with just one of these packs, since you'd only need to find yourself with a massive headwind/rain when you turn home, to be back with the misery of no assistance. However two packs gives about 10miles useable, and you can use gentle assist from one, saving the other for 'when you need it'. Also these batteries do chemically 'recover' a little. If you have been loading them hard, and cut the power, the voltage comes back up (normal), but it continues to climb over the next few minutes, and more power is then available when you ask again. So (for instance), with two packs you can get a little more range, by using a battery on a hill, and then switching to the other one for a while as it recovers.
Traditional (seems silly to talk about 'traditional' for a technology that has been around for for as little time as this....) LiPo packs, seem to perform less well when pushed up to high currents versus cell capacities, but are lighter for a given capacity. So (for instance), you could put together a 5Ah pack for little more than the weight of the A123 pack, bringing the 'C' numbers down. Currently the A123, is only managing about 80Wh/Kg, versus a 'best' from LiPo, of about 160Wh/Kg....
My 'ideal' pack, would probably be something like a 5Ah pack, with one of these 2.3Ah packs as my 'reserve'. This would potentially give about 300WHr, (about 1.3Kg for a 5Ah LiPo pack), and with current technologies would still total under 2.5Kg.
Best Wishes
