Panasonic Battery Issues

[flecc]

The capacity meter was something that 50C drew my attention to within this forum. It's obviously there for a reason and it has been stated on this forum many times that Panasonic equipment is of very high quality and very reliable, which it is (motor). I had just assumed that the metering systems were to the same high standard.

I'll forget about it for a while and see how I go.

I think the equipment standard is ok, it's just the method that isn't completely accurate. The only accurate way to tell what a battery's capacity is to fully charge it, then measure what comes out during use. Even that varies according to the rate of usage.

For example, if your battery was used at a rate of 4 Amp discharge and with the accurate method showed it had 10Ah capacity, when used at a rate of 8 Amp discharge it's capacity would be less, possibly lower than 7 or 8Ah. This is because the stress of discharging affects the cell efficiency, the higher the discharge rate, the lower the efficiency.

So you can see there's nothing set in stone about battery capacity. Interestingly A to B magazine tested one of the newer eZee batteries in this variable discharge rate way and showed the capacity varying from it's nominal 10Ah down to as low as 6.5Ah

I agree that it's best to agree with 50cycles that you use it for a while to see the trend over time, which might show that there isn't a fundamental problem, just a peculiarity relating to your usage pattern.
.

 

[tillson]

I think the equipment standard is ok, it's just the method that isn't completely accurate. The only accurate way to tell what a battery's capacity is to fully charge it, then measure what comes out during use. Even that varies according to the rate of usage.

It should be fairly easy for me to detect any trends as I use the bike 90% of the time on the same route. I also have access to accurate climatic data, so should be able to do comparrisons over time under similar conditions.

I'm hopeful that with the help and advice that I have extracted from this forum, this problem might finally be resolved!

PS 10210! How do you do it? It was only a few hours ago that you were passing 10000. It's just incredible. Its taken me since May to achieve 154. It just goes to show how little I know.

 

[kraeuterbutter]

hey.. i wanted to ask about if somebody has some pics of an open panasonic battery and what kind of electronics (if so) are included

however:
this "only 4 LEDs"-problem and "too few capacity" is also currently discussed in the German forum..

there i found a quote from the biketec (they build the Flyers and use the panasonic-drive + batteries) forum:

""Akku Problem gelöst! Enwarnung! (Schär Kurt)
Geschätzte Kunden und Interessenten Die gute Nachricht vorneweg: Alle Akku-Probleme mit zu frühem Abschalten und Blinken nach kurzer Zeit sind technisch NICHT defekt. Im Gegenteil, die Schutzabschaltung setzt zu früh ein. Der Akku kann in der Regel weiter gefahren werden obschon es blinkt. Ursache und Lösung: Der Akku muss bei einer bestimmten Spannung abschalten um nicht tiefentladen zu werden. Die Betriebsspannung beträgt bei vollem Akku und Normalgebrauch bei Raumtemperatur 25.9V. Bei grosser Stromentnahme (z.B. zu grosse Gänge, sehr sportliche Fahrweise) sinkt die Spannung durch die Belastung durch die Strohmentnahme. Bei kalten Temperaturen sinkt die Spannung ebenfalls schneller als bei Raumtemperatur. Bei gleichzeitigem Eintreten beider Ereignisse sinkt also die Spannung während der Fahrt also relativ schnell und stark, was völlig normal ist. Bei ca. 21V wäre der ideale Abschaltpunkt des Akkupaketes um die volle Kapazität zu nutzen und den Akku nicht zu tief zu entladen. Aus Vorsichtigkeitesgründen wurde diese Abschaltspannung etwas zu hoch angesetzt (ca. 23V), was bereits bei Erreichen dieser Spannung zum Abschalten führt, obschon noch viel Kapazität vorhanden wäre. Im Normalgebrauch funktioniert der Akku mit dieser Spannung problemlos. Von diesem Effekt betroffene Akkus können bei Biketec ab März neu auf die 21V programmiert werden. Also: Entwarnung! Der Akku war einfach zu gut geschützt und ist NICHT defekt! Für Auskünfte wenden Sie sich bitte per E-Mail an den Leiter Kundendienst, Herrn Mario Kofmehl: m.kofmehl@flyer.ch Freundliche FLYER Kurt Schär, Geschäftsführer Biketec AG Mail:k.schaer@flyer.ch" "

maybe this helps...
to make it short:
for safety reasons the cut-offvoltage was set to 23V
so: when going over hills (high load) AND cold temperatures this leads to a lower cell-voltage which further more leads to shutdown

the 23V were set too conservativley
so: no problem with the batteries, they are not damaged, they are only protected too well..

you can email biketec for sending the batterypack to them so they can reprogramm the cut-off-voltage to 21V instead of the too conservativ 23V

well..
so: has somebody fotos of an open pack ?
or tried to replace the batts
or even tried to use other battery-packs with the panasonic drive ?

thx..

 

[flecc]

Hi kraeuterbutter, it's not so much the metering of content that's the problem here, more the separate capacity measurement method when the cut off voltage should not affect the reading.

I don't have a photo of the BMS electronics, only one showing the polymer cell pack from the Derby Cycles factory:



It's not easy to use other packs due to the multi-connector five blade plug in arrangement of the battery on these, and in any case, all these bikes are well within their two year battery warranty period so it's not a time for modifications.
.

 

[kraeuterbutter]

yes, the cut-off-thing is for the problem, that the range is less than expected..
that is and was the problem of too high cut-off-voltage settings
so if you see this problem: it can be fixed

for the battery: maybe you can use an old battery to dismantel, and use just the case...
the batteries/cells itself can even be outside of the original battery-case...

like Molly from powerinmotion has done it in there video with the BionX system

 

[flecc]

The trouble is that it isn't always a shortage of range, in some cases the capacity check (not the content check) is showing that the battery capacity is 20% or 40% down but the range is still ok, so clearly the capacity check is wrong then.

In other cases both the capacity check reading and range have dropped, but after further use the capacity and range returns, and this hasn't always been in extreme weather. That's odd, once substantial capacity is lost one might expect it to stay that way.
.

 

[tillson]

I think I understand what is being said here. Is it that our (kalkhoff) batteries have a conservative protection system built into them to prevent damaging deep discharges? If so, surely this is a good thing and will extend the battery life?

 

[flecc]

I think I understand what is being said here. Is it that our (kalkhoff) batteries have a conservative protection system built into them to prevent damaging deep discharges? If so, surely this is a good thing and will extend the battery life?

Yes that's right, the slightly high cell cutoff voltage does allow a longer life, and it's probably a condition of the Kalkhoff battery warranty anyway.

Most cell types last longest of all when they are cycled between 20% and 80% of capacity, never going below or above those bottom and top limits.
.

 

[tillson]

high cell cutoff voltage does allow a longer life, and it's probably a condition of the Kalkhoff battery warranty anyway.

Most cell types last longest of all when they are cycled between 20% and 80% of capacity, never going below or above those bottom and top limits.
.

This is probably why they have the confidence to offer the 2 year warranty then.

 

[Fecn]

Before you read this post... Yes.. I know I should get out more

When I got my replacement battery from 50C, I thought I'd start keeping some records on it's performance. I have only completed one conditioning charge so far as work and weather have prevented me from spending much time on the bike lately, however, the one time I have charged the battery so far, I had the charger plugged into one of those plug-in watt meters.

Initially, when I plugged the charger in, it was drawing only 52 watts. (The charger is rated as 62 watts). A couple of hours later when I checked, it was drawing 60 watts. At this point, I realised that this is because it is a current-limited charger delivering it's maximum 1.8A and as the pack voltage rises, the total watts (Watts=Amps * Volts) used must increase too. A few hours later still, I saw that the charger using it's full 62 watts.. and shortly after that the watts started to drop down as the charger reached it's 29.38v cutoff point.

From this, I surmised the following...

1. Panasonic got their ratings on the charger absolutely bang-on.
2. The most power the charger can deliver into the pack is 1.8A*29.38V = 43.16 watts
3. In order to deliver it's maximum power, the charger consumes 62 watts. This means that it has an efficiency of 52.88/62 = 85.2%
4. Given that we know the efficiency of the charger, we can calculate the pack voltage at any pretty-much any stage of the charge... My inital 52watts consumption would correspond to (52*0.852 / 1.8A) = 24.61v. This is pretty much what I'd expect at the start of a charge cycle.

In total, my first conditioning charge used 285Wh of energy from the mains, which given an 85.2% charger efficiency would mean that 242.82Wh of it ended up in the pack (not bad for a 259Wh pack). Given a pack voltage of 25.9v, then I got about 9.37Ah of charge into the battery. Again, this is pretty much what I'd expect.. I rode the bike until the battery light was flashing indicating less than 10% remaining and then about another mile till I got home.

Given the magical 85.2% figure, it should be possible to calculate battery health for any pack regardless of what the battery meter says... Just flatten it, and measure how much power gets put back in. 85% of the watts out of the mains end up in the battery.

 

[flecc]

Agreed, thats a far more accurate way of checking the capacity Fecn, much better than an on the spot attempt at measuring it with metering.

Thanks for the efficiency measurements, as you say, they are quite impressive and indicative of the good design.
.

 

[wotwozere]

Hi

Really clever stuf you guys keep up the good work.

thx

Bob

 

[Fecn]

There was some nice weather at lunchtime so I went out on the bike and finished draining the battery for it's second conditioning charge. I was quite a long way from home when the battery light started flashing, so did roughly 5 miles with the light blinking before I could get to the charger. The charge cycle has just finished. As before, it started at 52 watts (around 24.6V pack voltage) and peaked at 62 watts. In total this cycle consumed 0.33kWh.

As a slight change to the fudged figures in my last post, I will now use a rough average of the pack voltage (25.9 + 29.4 / 2 = 27.65V) instead of the pack's default voltage.

85.2% of the 0.33kWh I took from the mains ended up in the pack (0.33*0.852=281Wh). Given an average pack voltage of 27.65V this would indicate that I squeezed in around 10.16Ah this time.

I think there can be no doubt that this pack is both healthy and properly conditioned right now.

 

[JamesC]

In total this cycle consumed 0.33kWh.

As a slight change to the fudged figures in my last post, I will now use a rough average of the pack voltage (25.9 + 29.4 / 2 = 27.65V) instead of the pack's default voltage.

85.2% of the 0.33kWh I took from the mains ended up in the pack (0.33*0.852=281Wh). Given an average pack voltage of 27.65V this would indicate that I squeezed in around 10.16Ah this time.

I think there can be no doubt that this pack is both healthy and properly conditioned right now.

Fecn - thanks for the figures on efficiency.

I have also monitored the kWh mains input on each charge of the 2 Panasonic batteries that I have been using since June.

On the few occasions that I have taken the batteries to exhaustion, they have both been consistent with your figures in taking 0.33kWh from the mains for a full recharge.

Today was warm enough to see an uplift in range, coming close to the mileage achieved last September/October of 25-26 miles per battery with a 19T sprocket.

James

 

[lectureral]

Advice request

My panasonic battery is about 8 months old and I have done a bit over 800 miles with it. The capacity test (press and hold the button) now shows only 3 lights. I haven't ridden to empty so don't know what the current range is - today I got to the flashing light after about 15 miles.

Does the panel think that I should seek a replacement under warranty (I bought in Switzerland so don't know if my seller will be as obliging as 50 Cycles)?

 

[flecc]

I certainly think you should pursue this, that rate of deterioration is greater than one would expect at 8 months.

However, it would be a good idea first to ride it to empty and then fully charge it, since that can condition the battery again and restore capacity when you test it.

You might find you go a very long time on the flashing light when riding it to empty, indicating the meter has lost registration. The action of emptying it resets it's zero point, correcting the problem if it exists.
.

 

[Fecn]

When I got my battery swapped, it was showing 4 lights on the capacity test, but managed just 6 miles before the flashing light started. Definitely do what Flecc says... fully drain and then recharge it as the capacity meter might have to re-learn the battery performance.

 

[lectureral]

Thanks guys - I will try that on this charge - and try to end up at a higher altitude than home when I do run out of juice!

 

[tillson]

I have experienced this indication of battery deterioration on 3 batteries so far. The last time it happened, the last light started flashing very early and the capacity test indicated 4 lights. I continued to ride the bike until the battery cut out and found that the range had not actually reduced. After recharging the battery, I found the capacity test had re-set to five lights.

Ever since the battery has been fine and today I have arrived at work still with 3 lights illuminated. I have never achieved this before. I am becoming more confident that there is no deterioration issue with these batteries, rather the capacity and charge level indicators are drifting. Time will tell I suppose.

 

[lectureral]

Yes - from reading the thread it seems that it may be a calibration rather than deterioration problem - I will let you know about mine when I have flattened and recharged it - lost 1 light at just under 5 miles today but then had to come back as winter was returning over the Jura and my 18 month old passenger was getting chilly and grumpy.