More accurate battery gauge?

[allen-uk]

On me Wisper 905 (2010) I've got the usual 3 power settings and lights on the bars, and the 4 light system on the actual battery, but it struck me that the difference in remaining power when the battery has JUST gone down to 2 lights is quite different from that when it has been on 2 lights for 5 or more miles.

I wondered a) whether any of the fancier bikes had a more sophisticated or accurate display of how the battery was discharging, or b) whether such a device is obtainable (and thus mountable) on bikes like mine.


Allen.

 

[morphix]

I've noticed most electric bikes seem to have these silly LED's for the power level indicator on the handlebars. You would think when you're spending £1k+ on a bike you'd get something more accurate wouldn't you.

I know the Wisper 906 and few top end bikes have the fancy LCD's now which have a battery icon with a proper series of bars. I wonder if it's possible to retrofit an LCD console for battery and speed as I know they're available to buy separately. I suppose you would need a controller to match?

 

[Synthman]

I'd say the ones on my Ninja are extremely accurate. It has a row of 4 LEDs plus a LOW LED. On a full charge I can drive up a steep hill and the lights wont drop under load. Each LED dims a bit before it goes out.

Basically the first LED starts dimming under load, then goes out, then the next one etc as the battery depletes. I can then tell almost exactly how much juice is left when the throttle is closed. When opened I can tell by how much the lights drop how weak the battery is. By the time the LOW light comes on there's less than a mile left.

I do think it was designed for a SLA, and indeed you can buy a Ninja with SLA batteries.

 

[Synthman]

Oh here's a pic....

 

[flecc]

I've noticed most electric bikes seem to have these silly LED's for the power level indicator on the handlebars. You would think when you're spending £1k+ on a bike you'd get something more accurate wouldn't you.

See my article on the link below which explains why they are not accurate and can never be:

Battery meters
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[Lloyd]

There are 2 things that affect how accurate the battery meter readout can be, the display itself, but more importantly the battery BMS. I have been testing some different setups on our prototype bikes for next years entry level Raleigh Range. Whilst I hope you will appreciate I cannot go into the ins and outs in too much detail just yet the basic idea is simple. Most of the cheap units that use basic led lights work off a very basic BMS system, which as Flecc states is affected by the current drawn not just the voltage.

Some high spec batteries can come equipped with an advanced BMS that will give a more accurate readout of battery voltage state regardless of curent drawn.

This does make a huge difference in accuracy, as we tested 2 identical bikes, one run with the advanced BMS, one without. On a short but steep climb, the advanced bms with me riding it remained a steady readout. The standard BMS on the same battery dropped on the LCD display. We swapped riders and recorded the same result. The batteries, bikes and displays were identical on both bikes.

We have specced the new advanced BMS on our entire entry level range for 2011, to run with an LCD display.

For those of you interested, yes I have been a bit vague and all will be revealed soon regarding the rest of the bike.......

 

[flecc]

Some high spec batteries can come equipped with an advanced BMS that will give a more accurate readout of battery voltage state regardless of curent drawn.

This does make a huge difference in accuracy, as we tested 2 identical bikes, one run with the advanced BMS,

Definitely, very much better. Nothing can overcome the fundamental problem of attempting to measure a chemical state electrically though, but BMS controlled metering is probably good enough for our purposes since other factors affect range from remaining charge so greatly anyway.
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