Kalhoff battery range indication

[4bound]

Does anyone here know how the "computer" on Kalkhoff bikes calculates the range remaining for the battery at each power level?
I know that on my car the remaining miles is calculated from the amount of fuel remaining and the recent mpg. This has the odd effect that if you start driving more economically than earlier, or maybe just go down a large hill, the remaining miles available starts to increase.
The Kalkhoff does not do this so I assume it has a preprogrammed idea of watt-hours per mile at each power setting.

When I first got the bike and plugged in the battery it said 104 miles remaining on economy power setting. However on every occasion since then when I have charged it it says around 75. I have checked this out by riding the bike on eco to see how many miles it would take to run it down and after 68 miles it said it had 2 miles left. I have no complaints about that but am curious about that initial 104 miles. Are new batteries charged up to a level higher than that achievable by the domestic chargers?

 

[flecc]

No, they are not charged higher, in fact new batteries are usually received with around half charge in them and should be charged on receipt.

Remaining capacity/range are calculated from the battery voltage, since as a battery's content is used, it's voltage gradually declines. This is not a very precise method of determining what's left so the figures need to be taken with a pinch of salt as the old saying goes.

On a few of the more sophisticated batteries such as those on your Kalkhoff, the accuracy also depends on an accurate zero content point being set in the system. When new your bike will be at true zero so the content of an inserted battery will read at a maximum. In use this zero point drifts slightly with each recharge so the subsequent content readouts can be lower. Some recommend that the battery should be used until empty every thirty or so charges to reset the zero point, but that is a little pointless just to achieve an academic figure.

However, your battery also has a separate capacity test by pressing the readout button for more than 5 seconds, and for that to be accurate, a reconditioning cycle is recommended if the capacity readout is unaccountably low. That means running until empty to reset the zero point and then recharging fully.
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[4bound]

Thanks for that Flec - now that I think about it I think I did charge it myself when it first arrived, and then plugged it in and it gave this 104 miles reading. However I am still puzzled as to why it did. I have only had the bike since January and have only cycled the battery 4 or 5 times so presumably the zero will not have drifted out much. In fact I have used it to exhaustion each time except the last, and it was down to 2miles then!
I charged it last night and have just put it back on the bike - it now reads "only" 64 miles on the Eco setting.
I don't quite understand your final paragraph - do you mean the button on the battery? Should I press for more than 5 secs when discharged, or recharged, or both?

I am not sure if I just have a problem with the calculations, with the battery, or with the charger. I am sure 50 cycles will have some useful advice, but trying to see what the problem is before I contact them! Maybe I don't have a problem at all!

Chris

 

[flecc]

I don't think you have a problem Chris, I don't place huge reliance on what range meters say. The button on the battery has two functions:

1) When pressed the five LEDS give a readout of remaining current which can be used, using the same voltage check as the console range indication.

2) If held down continuously for over 5 seconds, the readout then is the capacity of the combined cells in the battery to receive a charge, in other words the number of ampere hours (Ah). That is independent of the current charge put into the battery so this test can be at any time. Four of the five LEDs lit indicates roughly 80% of the Ah capacity for example. That could appear when the battery is getting old, or when the zero point has drifted over time (in which case condition it to reset the zero point). This readout of capacity can also be lower in very cold weather when batteries can be less efficient. Best not to condition it then since it will be self correcting when the weather warms up.
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