Panasonic Battery Issues

[NRG]

To make a 24V pack from 3.6v cells, you use 7 of them in series (which would give 25.2 volts)... then you deduct around 0.7v for the protection circuitry in the BMS. You get a usable voltage of 24.5v.. Round the 0.5 down and you've got 24v.]

Hi Fecn, why would the protection cct drop .7v? Is there a diode in series with the battery? I ask because I'm curious about BMSs in general and how they work, there seems to be some very clever single chip designs available today that use Mosfets to control power delivery and also provide protection IE:

 

[Fecn]

Hi Fecn, why would the protection cct drop .7v? Is there a diode in series with the battery? I ask because I'm curious about BMSs in general and how they work, there seems to be some very clever single chip designs available today that use Mosfets to control power delivery and also provide protection IE:

OK.. I admit it.. I was just making the maths easy for myself because Scott's post annoyed me first thing this morning. Most BMSes wouldn't drop anywhere near 0.7v.. 0.1v is a more realistic number.

 

[Xcytronex]

Hi Fecn

Sorry the post annoyed you. It had the same effect on me, hence the posting at 8:00am.

I assumed Wisper was claiming to use the latest type of lithium battery for pedelec use. Not using the type sold on ebay which is not really for transport use but more like communication devices.

I thought BEBA was for transparency so if a potential dealer or customer wants proof of the battery type then I am entitled to ask the question. It is quite a normal request when buying an electric vehicle.

Having been testing bikes for a number of years, to see the internals of a battery is asked more often than not. I have never been charged £50 for the service.

Best regards

Scott

You have been found to be mistaken-just let it rest.

 

[Fecn]

Sorry the post annoyed you. It had the same effect on me, hence the posting at 8:00am.

I guess that posting on forums is just as bad an idea before morning coffee as it is after evening beer

18650 cells aren't just for telecoms though... As I mentioned before, they're also for powering the Tesla roadster.

 

[flecc]

18650 cells aren't just for telecoms though... As I mentioned before, they're also for powering the Tesla roadster.

And that's the most technically successful electric car ever, so not much wrong with those cells. Everyone would have a Tesla if they weren't £70,000 each.
.

 

[Bandit]

And that's the most technically successful electric car ever, so not much wrong with those cells. Everyone would have a Tesla if they weren't £70,000 each.
.

It does have an awful lot of them, though. Is there a "safety in numbers" effect here?

 

[Tex]

the cells in my battery are manufactured in Japan by Sony (marked BMZ on the plastic casing around them). I think panasonic just purchased Sony Battery division?

 

[flecc]

I think panasonic just purchased Sony Battery division?

I don't think so, but they have recently bought Sanyo who are major battery makers.
.

 

[Tex]

flecc. that is probably the one i was thinking of. thanks

 

[Lloyd]

Personally I think there is a lot of hype around batteries. I have a theory, it is the motor and controller that makes more of a difference to battery longevity.

Panasonic crank drive systems are kind on batteries as during recent testing I struggled to get one to peak over 20A. The same tests on some well known hub brands resulted in peaks of up to 70A!

This is mirrored in model car racing. Over gear the car and run a high powered motor and your lipo packs struggle to last a season (regardless of them being el cheapo's or LRP packs at the top end of the spectrum). If you run a car suitably geared, with a lower output then surprise surprise your lipos last2-3 seasons. To put this into figures a high powered car, over geared, can peak at 100A compared to a much lower 30-40A for the same car, better geared and running a stock motor.

Running a crank system puts far less strain on a battery as the motor rpm remains more constant regardless of your actual speed. Over time I think this is kinder to batteries.

I hope this is right, otherwise I won't have a hope in hells chance of finishing the 24hr race this weekend!

 

[Wisper Bikes]

Hi David

Cannot believe transparency costs £50.00

I am sure your batteries are just fine. At least you have gained 0.5V out of this enquiry.

Cheers

Scott

Hi Scott, transparency costs nothing that's why I am free and easy with it! The £50 was just for fun. I would be happy to show an image of the Panasonic batteries, taking £50 of you as well would be sublime!

All the best

David

 

[flecc]

Personally I think there is a lot of hype around batteries. I have a theory, it is the motor and controller that makes more of a difference to battery longevity.

There's no question that the inadequate discharge rate of the batteries specified was most of the very short life problem of earlier lithium batteries, which is another way of saying the same thing Lloyd.

The most powerful motors like those on the eZee bikes were always going to be a problem for those early batteries, and even now will appreciably shorten their latest battery lives if the motor is used to the full. Life can be as little as 300 charges, while the gentle demands of the Panasonic system could mean perhaps 800 charges.

Both batteries are expensive latest generation types incorporating all the possible advances, but as shown, the lives can be made drastically different by the system, software and usage.

However, there are also the much cheaper Li-ion batteries which are obviously using the older chemistries and constructions, so I don't expect them to compare with the best polymer ones which are using the very real complex-cathode advances.
.