Range extenders

[Atlav4]

Hi quick question for the boffins, As i understand it range extenders are simple power packs with an output socket used to charge the main battery and cannot be used to power the motor directly. An extendable cable runs from power pack to the charge port on the bikes original battery, trickle charging so extending range. Question is why has no one manufactured a Generic cheapish one, surely if the charge port is accessible, (on any type of ebike) and appropriate connections used then this could be achievable. These could then be made like a bottle for internal downtube batterys, like a saddle bag for rear batterys, or long and thin slung under the crossbar for external downtube batterys. As with power packs used for mobile phones these could be marketed as emergency range extenders when on untried journeys or terrain, to be carried in the event that present range may be a problem. Just a thought.

 

[sjpt]

For simple reasonably standard batteries it is usually simpler just to have a second battery.
For the proprietary systems the charger has custom handshakes with the battery (and on the Bosch at least the charge point is hidden while the battery is in use)

 

[Atlav4]

Hi i understand about some chargers being exclusive to certain makes of battery, and know not all have excessible charge ports whilst on the bike. There must be many makes where it could be possible. This would be an emergency portable pack, hopefully weighing a kilo or less that once attached (and left awhile) would supply around 5 to 10 miles. Only taken when unsure of routes or road conditions or terrain and your current range might come up fractionally short. Majority of rides never come close to max range BUT on exceptional occasions you just might

 

[Ocsid]

If it is just 5 to 10 miles is it worth the hassle, just bite the bullet and pedal home and "learn" the bike's limits?

Pre the "lockdown" I a very few times took the charger so we could top up the wife's e-bike at a coffee shop break; in reality the need to use it was very rare.

 

[Atlav4]

I know you quickly learn your bikes limit and most riders from the door have several routes they do with probably a favourite. But if you take the bike to areas of which you are not familiar then if you had a lightish extender you'd probably chuck it in bag just in case. Even with careful route planning it doesn't always go to plan.

 

[Nealh]

Range extenders aren't used that way for ebikes, in general any range extender is physically connected in series to turn a 36v battery in to a 48v one or paralleled voltage wise to become a larger capacity pack.
With lithium cells you can't use one to charge another as the voltage has to be nearly the same or within 0,025v other wise heat transfer is too much as it flows unless you can regulate the current flow and add the necessary pcb software to allow this to happen, heat is bad for cells and the transfer will be so hot you can't touch the wiring. The flow rate needs to be low like 1 or 2a and not tens or hundreds of amps.
The simplest solution is too parallel packs/batteries.

 

[Atlav4]

Thanks for your patient replies nealh I think I understand the heat exchange danger. The initial question was just curiosity/interest but both have been triggered. So when googling around I came across a site that has programmable connections between batteries (ie when to draw current and in what ratio from duel batteries) Now then the bike would then have to have a second housing/cradle with a protective cover when not in use. If this cover had a dummy connection and sat in the cradle it could be fashioned to act as a bottle holder and act as such 99% of the time. Until an extra battery was inserted then it could be used in a pre programmed efficient way. Probably only used on bikes that are stealth types ie ticket/faro etc. Then the extender battery would be fashioned to look like a bottle. I know this mimics the x35 and fazua and others systems but would hopefully retail much more realistic than those mentioned. Just the ramblings of an old dude, think the site was King meters not sure.

 

[Benjahmin]

Seems a lot of faff when a simple Y lead acting as a splitter does the job to parallel the batteries. Also charge voltage is 41.6 - 42 volts, li ion batteries quickly move below that when in use, so would it work?
I carry a second soft pack battery in my pannier just paralleled to the rack battery. I just check the voltages before I plug them together. Generally there is well less than 0.5v between them, any more and I use them seperately.

 

[Atlav4]

Your solution sounds perfect for bikes with rack batteries, and of course you only carry the soft pack if pushing existing range. On bikes with internal batteries aesthetics are more important and stealth of course, the more the second battery looks like an actual bottle the better. With a splitter xt60 and a second housing/cradle can you switch between the two manually? If so them being almost identical isn't a problem. Then a lightweight dummy cover converted to an actual bottle holder again aesthetically pleasing, could be manufactured. Then the actual second battery could be the size of your choice (within reason) and budget, complimenting the looks of the bike.