Renew the cells in Kalkhoff battery

[warmrain]

Hello all,
My wife bought a secondhand Kalkhoff Tasman electric bike which was "new" in 2008. After a small service on the mechanicals it works well but I suspect the "10aH Li-ion Mn" battery has lost substantial capacity because it registers a blinking low battery light (from full) after just a mile or so in moderately hilly terrain.

At that point (low blinking light) the resting voltage across the two measurable pairs of terminals on the removed battery measures 25.5v and 28v.

Immediately following a full recharge to charger switch off, the voltages are 26.2v and 28.8v.
After then standing for 24hr, the corresponding resting voltages are 28.6v and 28.6v.

My queries are:
1/ I presume one of those voltages is the "reference" voltage set after charging which the BMS/contoller uses to decide how discharged the battery is. -- Is this correct?

2/ The voltage (25.5v) at which the 'battery critically low' light starts blinking still seems quite high. Is the controller / BMS being unduly pessimistic?

3/ Is it possible to replace the cells in the battery, and if I do so with a type other than the original ?Li-Manganese? can the original Kalkhoff charger still be used to charge correctly?

4/ Any instruction or tips on replacing the cells would be most appreciated, including as a starter, how to open the case without breaking it (!). I can see 4 small screws which I thouht were Torx type but none of my torx bits fit.

My thanks in anticipation of any advice.

 

[Alan Quay]

I think your best bet is to contact Jimmy, at insat. He Can re-cell it and is held in high regard around here.


http://www.bga-reworking.co.uk/insat-li-nmc-ebike-battery-10ah-24v-36v-48v.html

You don't say what nominal voltage the battery is, and the readings you give don't add up. I don't understand how you are getting two different readings. Possibly your meter is faulty or not being used correctly.

Sent from my HTC 10 using Tapatalk

 

[warmrain]

I think your best bet is to contact Jimmy, at insat. He Can re-cell it and is held in high regard around here.


http://www.bga-reworking.co.uk/insat-li-nmc-ebike-battery-10ah-24v-36v-48v.html

You don't say what nominal voltage the battery is, and the readings you give don't add up. I don't understand how you are getting two different readings. Possibly your meter is faulty or not being used correctly.

Sent from my HTC 10 using Tapatalk

My apologies for not making it clear.
The bike has what I presume to be a Panasonic crank motor running at a nominal 24v.

The battery actually has 5 terminals. One is marked (+) and one marked (C) with the others being negative. Remeasuring now with a reasonable quality digital multimeter, the reading (after full charge and standing for 24hr) the reading of either (+) or (C) terminal against either of the 'outer' negative terminals gives 28.6v but if measured against the 'middle' negative terminal gives 26.1v .

Sorry for the initial confusion and also thanks for the reference to Insat Services. I still wonder if I can renew it myself though and would appreciate any other advice.

 

[flecc]

Yours is the early Panasonic unit and battery which introduces difficulties since it doesn't use the regular cylindrical cells. Instead it has soft pouch cells. The page on my Panasonic help site linked to below gives all the details you need about which is the output connection to measure voltage at, and also illustrates the battery internals with the 14 pouch cells. I doubt Jimmy will be able to recell this or that you can get these cells.

Panasonic 26v 10Ah battery
.

 

[Alan Quay]

My apologies for not making it clear.
The bike has what I presume to be a Panasonic crank motor running at a nominal 24v.

The battery actually has 5 terminals. One is marked (+) and one marked (C) with the others being negative. Remeasuring now with a reasonable quality digital multimeter, the reading (after full charge and standing for 24hr) the reading of either (+) or (C) terminal against either of the 'outer' negative terminals gives 28.6v but if measured against the 'middle' negative terminal gives 26.1v .

Sorry for the initial confusion and also thanks for the reference to Insat Services. I still wonder if I can renew it myself though and would appreciate any other advice.

You may be able to DIY, but you'll need a spot welder. I'm pretty sure Jimmy will be the most economic solution.

Sent from my HTC 10 using Tapatalk

 

[flecc]

You may be able to DIY, but you'll need a spot welder. I'm pretty sure Jimmy will be the most economic solution.

See post above Alan, these batteries are radically different.
.

 

[Alan Quay]

See post above Alan, these batteries are radically different.
.

Why not re-cell it with modern 18650's?

Sent from my HTC 10 using Tapatalk

 

[flecc]

Why not re-cell it with modern 18650's?

If there's room for them it would be ok. Some of their unit batteries have been rather awkwardly shaped for conventional cells to fit, one for Jimmy to experiment with perhaps.

Of course Kalkhoff replaced this battery with their own boxy BMZ version which does use 18650s, so the OP can buy one of those.
.

 

[Alan Quay]

If there's room for them it would be ok. Some of their unit batteries have been rather awkwardly shaped for conventional cells to fit, one for Jimmy to experiment with perhaps.

Of course Kalkhoff replaced this battery with their own boxy BMZ version which does use 18650s, so the OP can buy one of those.
.

I'm pretty sure Jimmy could do it. With these new 3.5ah Panasonic cells you'd only need to get 21 cells in there for a 3s7p, giving 25v 10.5ah.

Sent from my HTC 10 using Tapatalk

 

[warmrain]

Many thanks for the information on the Panasonic system and batteries Flecc. Very useful. I think perhaps before I do anything else I should take it through a couple of full "reconditioning" cycles first and see how much it improves matters.

Incidentally, what voltage do you think one should be getting (measured) at the battery if it is truly discharged to its safe limit and not just the BMS/controller monitoring system getting out of calibration?

Also, I suppose if there were just one bad cell in the battery it might pull down the voltage when on high load and trigger the low battery warning light?

 

[flecc]

Many thanks for the information on the Panasonic system and batteries Flecc. Very useful. I think perhaps before I do anything else I should take it through a couple of full "reconditioning" cycles first and see how much it improves matters.

Incidentally, what voltage do you think one should be getting (measured) at the battery if it is truly discharged to its safe limit and not just the BMS/controller monitoring system getting out of calibration?

Also, I suppose if there were just one bad cell in the battery it might pull down the voltage when on high load and trigger the low battery warning light?

Yes, definitely do the reconditioning cycles first to ensure the meter is accurate. Once done, ideally with a new battery you would get 29.4 volts fully charged, 22 volts at cutoff.

A cell that was failing would behave as you've described, prompting premature cutoff.
,

 

[oriteroom]

Looks like an easier option

http://www.ebay.co.uk/itm/391614891006?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

 

[warmrain]

Thanks to Oriteroom for pointing me towards ebay.

Has anyone tried or used this replacement below (or any other batteries from that seller) for any length of time, and are they any good? Made in China and supposedly constructed with 'Samsung cells'.

http://www.ebay.co.uk/itm/24v-25-2v-20-8ah-electric-bicycle-lithium-ion-battery-sliver-new-SAMSUNG-cell-/222011627958?hash=item33b0ec99b6:g:zU4AAOSwOVpXa1jE

 

[flecc]

Has anyone tried or used this replacement below (or any other batteries from that seller) for any length of time, and are they any good? Made in China and supposedly constructed with 'Samsung cells'.

http://www.ebay.co.uk/itm/24v-25-2v-20-8ah-electric-bicycle-lithium-ion-battery-sliver-new-SAMSUNG-cell-/222011627958?hash=item33b0ec99b6:g:zU4AAOSwOVpXa1jE

View attachment 16328

I don't know anyone who's tried one of these, but it looks extremely wide on the left hand side. That makes me wonder about crank arm clearance. Panasonic and Biketec did a wide battery version that wasn't as wide as this for Biketec's off-road X model, but that had widened crank arms.
.

 

[warmrain]

Good point Flecc regarding the 20.8aH battery.!
Doing the best estimation I can, measuring the likely projection from the one fixed point I have which is the connector slot and stated battery dimensions I reckon it may project at least 6cm, which is at best very very close to hitting the R hand (offside) crank -- within a millimetre or so.

Unfortunately I can't be sure without having a physical example to try out and I wouldn't want to get one without being sure. Bit of a catch22 situation! It would have been better if they had redesigned the larger case to be taller (with the lock in the same place) instead of being fatter

 

[Kenny]

I use 18ah batteries on my crossbar and step through Kalkhoff bikes.
They are 130mm wide so are 23mm narrower than the 20.8ah battery.

I just checked the clearance on both bikes and the crank arm has just over 20mm clearance, each side, on both bikes so the 20.8ah battery should be fine.

I'd buy one myself if I needed one. looks a very good bargain!

 

[warmrain]

Looks like an easier option

http://www.ebay.co.uk/itm/391614891006?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Incidentally, Oriteroom, I did successfully bid for these batteries(!) but had to return them because they both had some kind of internal fault as the main output connections (indentified as per Flecc's documentation and also verified on my old battery) only had 2.9 to 3.0v despite being apparently charged up with 5 lit LEDs. They also didn't look quite as new as described...

Just a heads up to anyone else to think carefully, in case these particular batteries above get relisted!