Do I need cyclic batteries?

[Jeremy]

96V at 33Ah is still only a theoretical 3168Wh, or a usable 2535Wh, so significantly less than the capacity that I think you'll need to get the range you want at the speed your hoping to go. The reduced current demand from the battery pack will help thing a bit, but you'll still need a fair bit more capacity to get your desired range.

Regeneration will help if the journey has lots of stops and starts, or is over hilly terrain, but the best you can hope for is maybe 5 to 8% energy recovery, even then. This won't be enough to get a 96V 33Ah pack up to the sort of range and speed you're looking for.

How streamlined is your trike? If you can get the CdA (the product of drag coefficient and projected frontal area) down to a low figure then you may be able to reduce the high-speed power requirement a bit, so reducing the demand on the battery pack. Something teardrop shaped, for example, might give you a high speed range advantage of maybe 20 to 30% over a more conventional body shape.

Jeremy

[newtrikebuilder]

I'm actually looking at 96V at 100Ah, not 33Ah. 33Ah was what should give 25-35miles (I think 35 was slow speeds, and 25 was faster speeds, but not as much as 60mph).

I agree that 33Ah wouldn't have a chance, but I would have thought 9.6Kw would.

The motor is the Etek-RT. It should be able to run at 96V (hopefully), but I will need to make sure it doesn't get too hot.

I haven't decided on any bodywork yet. I'm still in the process of modifying the chassis design (this depends on the battery size etc.), and I will need to decide whether it's worth spending the money. I'd like to do a streamline body, but I don't know whether I will have the skill/experience/money to do it.

[Jeremy]

96V at 100Ah, or 9.6kWh theoretical, maybe as much as 7.68kWh in practice, should be OK, but range will depend a great deal on body shape, frontal area and weight. Getting a low drag coefficient isn't that easy, but reducing frontal area and weight is a bit simpler for a DIY job. The reason recumbent bikes are faster than upright bikes is almost wholly down to the reduced frontal area, both have drag coefficients that are fairly similar (without fairings etc). Anything you can do to reduce this, within the bounds of good visibility for the driver and other road users, will help. For example, if you needed 5kW to do 60mph, then reducing the frontal area by 50% (a tall order) would reduce the power required to overcome drag at this speed to about 1.25kW. Power required is approximately proportional to the cube of drag or the square of frontal area or Cd, ignoring rolling resistance and the power required for hill climbing and acceleration.


I think that the motor you have is really a Mars ME0709, which isn't anything to do with Briggs and Stratton (who own the Etek trademark) but which has been mislabelled as an Etek in order to deceive buyers (in my view) by at least one reseller in the US (something that would be illegal here). I happen to have a new one of these motors spare (purchased directly from the manufacturer, Mars Electric LLC, see here: http://www.marselectricllc.com/me07091.html) but looking at the spec sheets the nominal maximum rating seems to be 72V. However, looking at the Kv it looks like the motor would only run at about 4800rpm or so on 96V, which seems as if it might be OK. John Fiorenza at Mars Electric would be able to confirm this - he's a very helpful chap who designed this motor himself, I believe.

Jeremy