I've been exploring the possibilities of using a range extender for touring purposes. I don't generally need an extender for day rides; tThis would be to allow a recharge when it's not possible to get the whole bike to a charge point at a B&B, so that I can continue riding the next day. I have so far investigated three types of system:

• Bosch 'powermore' system. As far as I can tell this system will run down both batteries (main and extender) at the same rate. So if (at the end of a day's riding) both batteries are at 50%, it's only possible to add another 50% to the extender. You start the next day with 50% of main and 100% of extender. Not ideal, especially if day 2's B&B doesn't allow charging either.

• Specialised Creo range extender. This appears to have two modes; you can switch between using the extender first, or using them both together (as per the Bosch system). Using the extender first means that it will be at 0% at the days' end, and the main battery will be at more than 50%, - so you can add more charge to the extender and start the next day in a better state of charge overall. One drawback of this system, though, is that you need to use the app to switch modes, and if left on 'extender first' mode the bike won't be powered at all when the extender runs out. So any problem getting the app to talk to the bike mid-ride would be a bit of a disaster.

• Mahle X35 system ; the range extender for this will charge the main battery as it runs down (it doesn't power the bike directly), so it will by default run down first and therefore can be recharged fully at the B&B. This seems to be a similar method for the newer Mahle systems (X20).

Clearly one solution for the 'charging at B&B' scenario is to use a removable battery like the Fazua system. I have tried this and wasn't very happy for various reasons which is why I'm considering a new bike.

Can anyone confirm any of the above, or offer any other thoughts , or systems I haven't noted?

Thanks

Edited March 31Mar 31 by quilkin
more research done

I'm not into big brands but got the same gist as you about Bosch and Mahle extenders.

Can you clarify why a removable extender battery would work better for you than the removable main did? It's the obvious simple solution and often extenders are smaller. Another way would be to swap between two batteries, one carried rather than fitted as an extender, to copy the Specialised scheme without app hassle. I like to charge outdoors where possible so my own solution is a 6m mains lead for my portable charger.

You can use any battery you like as a range extender and you don't need to buy any special system or phone app.

All you have to do is splice two wires to the two battery power wires somewhere between the main battery and the motor. If you do as simple as that, both batteries need to be fully-charged when you connect the extender. They will both go down in voltage together until the Bosch battery switches off when empty.

Next up from that is one of those Aliexpress/Ebay parallel battery diode arrangements for about £20. With one of those, you can connect the extender battery at any state of charge. Whichever battery is highest will go down until they're the same voltage, then they'll go down together. It will work as long as the Bosch battery has enough charge to switch on because the Bosch battery is needed to do the hand-shaking protocols. The extender doesn't need comms to work in parallel, even if it's the one providing all the power.

My question would be, 'Why buy a Bosch powered bike?'.

If you're looking for a different bike anyway why not get a nice tourer and put a conversion kit on it, thereby circumnavigating all the difficulties thrown up by trying to hack the Bosch system. You can then run as large or as many batteries as you want/need, either in parallel or swopping them over as they become empty.

I have run two batteries, via a Y splitter, for a few years. It stresses each battery less (as each takes around 50% of current load), reduces voltage sag and increases range. Also good quality generic batteries are way cheaper than any Bosch battery and the bike and kit itself will be much cheaper.

Thanks for feedback. More questions than answers! I'll try to explain.

22 minutes ago, Benjahmin said:

My question would be, 'Why buy a Bosch powered bike?'.

If you're looking for a different bike anyway why not get a nice tourer and put a conversion kit on it, thereby circumnavigating all the difficulties thrown up by trying to hack the Bosch system. You can then run as large or as many batteries as you want/need, either in parallel or swopping them over as they become empty.

......

I've tried that; I converted a Dawes Galaxy with a Whoosh kit a few years ago. I didn't like the weight of the whole system, and I didn't like the poor power control system (although that has maybe improved over the years?). I'm aftera lightweight bike, no more than 14g or so. Bikes that are too heavy don't handle as well on the road, and are more difficult (for an oldie like me) to carry up steps, load into a train, etc

8 hours ago, D8veh said:

You can use any battery you like as a range extender and you don't need to buy any special system or phone app.

All you have to do is splice two wires to the two battery power wires somewhere between the main battery and the motor. If you do as simple as that, both batteries need to be fully-charged when you connect the extender. They will both go down in voltage together until the Bosch battery switches off when empty.

....

I'm not into modifying systems like this: (a) it would invalidate any guarantee (b) it would increase the risk of fires

8 hours ago, AntonyC said:

I'm not into big brands but got the same gist as you about Bosch and Mahle extenders.

Can you clarify why a removable extender battery would work better for you than the removable main did? It's the obvious simple solution and often extenders are smaller. Another way would be to swap between two batteries, one carried rather than fitted as an extender, to copy the Specialised scheme without app hassle. I like to charge outdoors where possible so my own solution is a 6m mains lead for my portable charger.

I have tried two Fazua systems. I don't like clunkiness of the clutch engaging and disengaging. The battery/motor assembly is heavy to remove - my partner broke her toe when it dropped onto her foot while removing it from her bike.

A 6m mains lead would be a lot of extra weight while touring! and I won't leave my bike outside a B&B overnight

54 minutes ago, quilkin said:

I'm after a lightweight bike, no more than 14g or so.

You are certainly an optimist at 14g! (but I think we know what you mean)

I converted a Dawes Galaxy with a Whoosh kit ... I didn't like the poor power control system (although that has maybe improved over the years?).

Sadly I don't think so unless it's changed recently.

I'm aftera lightweight bike, no more than 14g or so. Bikes that are too heavy don't handle as well on the road, and are more difficult (for an oldie like me) to carry up steps, load into a train, etc.

Walk assist can help with steps and trains. A modest-assist kit can be had for ~ 4kg and if it's a hub motor you can replace the electrics with KT: they can be set up for entirely different power control.

I'm not into modifying systems like this: (a) it would invalidate any guarantee (b) it would increase the risk of fires

Wise words if you're in any doubt.

A 6m mains lead would be a lot of extra weight

Typical charger 2A -> 100W -> 0.5mm mains flex -> 31g/m -> 180g for PVC flex indoors with the charger lead going outside to the bike; double for outdoor flex.

The battery/motor assembly is heavy to remove - my partner broke her toe when it dropped onto her foot while removing it from her bike.

I'm still not clear why a removable main battery with or without a spare - surely the commonest OTS solution - isn't acceptable, as they must start around 2kg. If it's purely awkwardness / ergonomics I'd fashion a decent handle out of wood (seriously) and paint it. D8veh's old posts show you can get a fantastic finish that way.

You can build a lightweight ebike as said above, there are a selection of lightweight hub motors between 1.45 kg and 2.1 kg. A 36v 10Ah bag battery is 1.8 kg, 15Ah 2.4kg. Add a kt controller which is power based control system rather than speed based control system and a 10-11kg donor bike

Edited March 31Mar 31 by Peter.Bridge

1 hour ago, Peter.Bridge said:

You can build a lightweight ebike as said above, there are a selection of lightweight hub motors between 1.45 kg and 2.1 kg. A 36v 10Ah bag battery is 1.8 kg, 15Ah 2.4kg. Add a kt controller which is power based control system rather than speed based control system and a 10-11kg donor bike

That's what I'd do if I wanted a lightweight ebike. You can get a nice donor for about £250, add your own lightweight electrical stuff for less than £400. Then you have a really nice ebike that you're in control of re spares etc. No need to worry about invalidating warranties or anything like that, and you can buy multiple batteries of any size for whatever length journey you want, and each one would cost less than £200. I have a little folding bike that can run an 8Ah 24v battery or 10Ah 36v one - completely interchangeable, and a nice KT control system.

I did this one on a facebook marketplace Boardman Hyb8.6 with an AK M100 motor, and a downtube 36V 17.5Ah battery and KT controller, weighed in total 16 kg including battery, but you could go for lighter motors, batteries and donor bike if you were that bothered

47 minutes ago, Peter.Bridge said:

I did this one on a facebook marketplace Boardman Hyb8.6 with an AK M100 motor, and a downtube 36V 17.5Ah battery and KT controller, weighed in total 16 kg including battery, but you could go for lighter motors, batteries and donor bike if you were that bothered

I built this one from a Whyte road bike that I paid about £150 for in 2017 with a 1.5kg Xiongda motor and I built my own 1kg battery. I later changed it to a rear Xiongda cassette motor with a standard 1.2kg bottle battery from Aliexpress. The whole kit was less than £250:

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2 hours ago, Peter.Bridge said:

You can build a lightweight ebike as said above, there are a selection of lightweight hub motors between 1.45 kg and 2.1 kg. A 36v 10Ah bag battery is 1.8 kg, 15Ah 2.4kg. Add a kt controller which is power based control system rather than speed based control system and a 10-11kg donor bike

Thanks, may be interesting. Can you point me to a website etc for this kit? The Woosh systems don't seem to have change much in the last 5 years.

BTW, one thing I don't like about kit based systems is the plethora of untidy wires that end up all over the bike.

I ordered it from topbikekit - which is more expensive than some but good quality and has a very extensive range of components - I bought the battery with built in KT controller in the battery holder (which helps cable management)

Hailong 1 Battery 36V17.5AH Panasonic NCR18650GA Battery Pack with 36V inner controller
9Pins 60cm 9pins extend cable
Charger M120-36V2.5A
Display KT LCD5
Cable 1-2 cable
PAS KT-V12L

There are bottle batteries with built in controllers if you want a lighter option

TBK-100AD CST 260 rpm motor - I then got Arrow wheels to build the wheel

https://topbikekit.com/

https://www.arrow-wheels.co.uk/

Edited March 31Mar 31 by Peter.Bridge

I'll have to remind myself that heavier two wheeled vehicles handle badly next time I am riding one of my motorbikes - especially the 200 Kg Royal Enfield.

To be honest, I have never ever noticed them handling badly - not once. Quite the opposite. They feel very stable and steady and handle even quite monstrous potholes at speed. Last week I went through a pothole about three inches deep at 5O miles an hour. I felt it, but I'd have been off if Id run into that at twenty on a bicycle.

This may be an 'odd' opinion, but even with an ebike, the weight of the bike is a small part of the total weight of bicycle and rider. I weigh 76Kg stripped and probably nearer 80kg in my outdoor gear. The weight of my ebike is but a quarter of that.

As a cantangkerous git - I am going to suggest that there is FAR too much nonsense talked about shaving a few grams or even a kilogram or two off the weight of an ebike or any kind of bike - often by riders who have eaten too many pies and vastly outweigh their super lightweight steeds.

2 hours ago, D8veh said:

I built this one from a Whyte road bike that I paid about £150 for in 2017 with a 1.5kg Xiongda motor and I built my own 1kg battery. I later changed it to a rear Xiongda cassette motor with a standard 1.2kg bottle battery from Aliexpress. The whole kit was less than £250:

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Nice looking velocipede that.

Bargain all round I'd say.