flecc, thanks for your comments. Can I just ask what you mean by 'From past experience this sort of thing can happen when supplies of parts are unreliable.' Is that to suggest it's better to avoid at the moment? Also, the rear sprocket situation, can that be done on both the Forza and the Kalkhoff? Thanks.
Sorry about the delay in seeing this.
No need to wait, part supply unreliability is a semi-permanent situation in cycle manufacture in recent years, there's always something in short supply due to surges in demand for certain models or types of bike. The big manufacturers buy up supplies in advance to ensure production continuity, leading to shortages for the others.
The simple sprocket change I mentioned is only on the Kalkhoff, due to it's hub gear and both motor and rider driving through it.
However, you wouldn't need to make any gearing change on the Forza since it has a gear range that covers any hill steepness, right through to over 20 mph.
Referring to the battery type, much depends on whether you have hills to climb and how steep or long they are. On steep or long climbs where the throttle is held fully open for quite a while, the Li-ion battery will not be able to sustain the high current demand of the Forza motor and a safety cutout will operate. That could make your journey frustrating. However, if your trip is mainly fairly flat, enabling you to keep up speed well above 12 mph or so, you won't suffer badly from the cut-out problem simply because the bike will run at half throttle with power to spare in those circumstances. NiMh batteries do not suffer that cutting out.
It's a balance, the NiMh don't cut out and last a bit longer, but are not so convenient when charging as they need some extra attention.
Li-ion can cut out as described when used with powerful motors, and they can be shorter lived, but they are very convenient in use since they can be charged at any time by any amount, in no way restricting the way they are charged, so simplest to use.
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