Battery "fuel gauge" query

[flecc]

It could leave you that if the current usage was gentle, but later in the ride if there was a high demand, instead of just dropping to one LED, the low voltage cut-out might operate. Switching off and on would get you running again then, but it would then be prone to further cut-outs when demand rose.

The emptier the battery, the more likely a cut-out when current demand rises.

 

[Deleted member 4366]

You cannot in any way relate the display segments/LEDs to battery capacity. The only thing that you can do is note how they behave on your own bike and see what happens and how far you can go when the battery runs down to cut-off. What your bike does will bear little relation to others, so no point in asking anybody else. On some bikes, you lose segments/LEDs as soon as you start riding, on others, they stay lit right to the end and then go down in quick succession. Some batteries sag something rotten, so the LEDs dance up and down like a Xmas tree.

 

[Sheffmax]

OK, thanks. My plan at the moment, to determine range, is to do ever increasing circles until it does cut out. As it's all hills and valleys round here I can get to the foot of my home hill without too much effort so I shouldn't have more than a 2 mile slog up the final ascent.

 

[Deleted member 4366]

That's a better idea. Their behaviour on your bike should be consistent. Don't forget that the higher the load that you put on the motor, like slow speed up hills, the more your battery will sag. It'll also sag more when it's run down, so you need to be gentle on the power for the final hill to avoid premature cut-off.

 

[Streethawk]

I suspect the Bosch system has a watt-meter built into it as the estimated ranges are very very accurate so long as the terrain remains consistent. Even then though, if you encounter a big hill and use a lot of power in a short space of time, the readout's remaining range appears much lower, although it gradually reworks it's estimate all the time.

 

[Richard_M]

A wattmeter is fairly accurate in showing how much battery you have left. It measures amp-hours or watt-hours used...

New Digital 60V/100A Battery Balance LCD Voltage Power Analyzer Watt Meter | eBay

Mine's just arrived and it's a bit flimsy and optimistically rated, but cost less than a tenner. Amazing !
I shall pull it apart and apply all sorts of volts and currents.

Thanks for the link, d8veh. With a bit of modding this could be a handy bit of kit. Just what my bike needs.