Latest progress on cell upgrade for Bosch battery.

[El Champiero]

Are we talking about the new 2014 Bosch batteries as regards to hand shaking etc?

Anyway, from my own experience I can honestly say that for the pre 2014 Bosch systems, the battery is not tailored to the motor that came with the bike.

I am aware that the BMS in all the Bosch batteries (pre 2014 and 2014) logs the charge cycles. I don't know exactly how many charge cycles it has gone through.

I can estimate this though with a reasonable accuracy (when I find out the purchase date of the bike)

I haven't heard anything on the German forums to suggest that the pre 2014 BMS has an inbuilt expiry inside it.

 

[Deleted member 4366]

I've seen some guys using dual Bosch batteries (rack and frame), but I've never seen anyone using a Chinese battery. I was wondering why.

 

[trex]

I've got a junk mail the other day from a Shenzen company that make 'plug compatible' Bosch and Panasonic batteries - deleted the junk mail by mistake so can't remember which one it was. I think they quoted about $200 for the 300WH Bosch compatible battery with Samsung cells.
I am not sure about logging charging cycles. How many pins are there on the output of the battery? if only 2, then there is no handshake.

 

[Deleted member 4366]

It looks like five pins are connected. I can only guess what they do. Two for power out. One could be for charging, another one to switch on the BMS, although they could use two. Someone must know.

 

[El Champiero]

There are definitely 5 pins on the connector. You have pins 4 and 2 as positive and negative leads. Pins 1,3 and 5 take much smaller diameter wires (coloured green, purple and yellow. These wires are connected to the BMS - not sure what they do - though I am sure it could be figured out with reference to other BMS set ups). The actual PCB looks pretty complex. The only things I can make out on there are the main processor chip, a piezo sounder (probably an alarm for overheating or something) and 40amp soldered fuse.

 

[El Champiero]

This website mentions the BMS ensuring the battery has about 1000 charge cycles. I don't think this implies that a counter is on the BMS though. http://ebikeee.com/2013/01/31/we-visited-the-official-bosch-ebike-training/

 

[El Champiero]

@ Trex - if you do happen to find that email I would be very interested in looking at it to see how they do it. The plastic matrix which holds the cells together is custom made and necessary to hold the cells rigidly in place. So to copy it they must have used a 3D printer or something.

So far I think the best method for re-celling the pre 2014 batteries is to use the company I used and then connect up the BMS and pop it all back in the case.

 

[Deleted member 4366]

"The special BMS makes sure that the lifetime of the battery is about 1000 charging cycle". How can it do that then? There's nothing it can do to improve the number of charges other than limit the current and keep the cells in the safe range of volts, which all BMS's do. Sounds very suspicious to me.

 

[El Champiero]

My guess is that the 1000 cycles is an estimate. Just found out when I started using my bike. It was from the start of December 2012. I de-restricted it in Feb 2013.

so, approx full charge cycles as follows:

Used 3 times per week on average. Usually charged twice per day so that makes 6 charges per week (full charge cycles)

12 months use from Dec 12 till end November 2013 (when I changed to another new 288wH battery) = 52 weeks.

Therefore, approx 312 charges so far.

 

[El Champiero]

I just found this link. http://www.alibaba.com/product-gs/1611695646/Bosch_Replacement_36V_8_8Ah_electric.html

They say that they use Samsung cells inside the battery pack. They are also a gold supplier so for them to pull a fast one is highly unlikely I think. I think they have done a bare bones copy of the BMS PCB. My guess is that they have left out the bits that aren't really necessary like the sounder and some other stuff. Minimum order quantity is 1 unit. The case is probably not as good quality as the original Bosch units. Also, This is only for the 8.8aH battery but I reckon you could get them to put higher capacity cells in there if you requested a custom build.

I think it is worth going for at this price. It would be interesting to see how the copy battery performs against the genuine one.

 

[El Champiero]

And some more info - the copy battery BMS lets you run the pack down to 30V instead of the standard 36V which Bosch employ. This may lead to shorter battery life in the long term.

 

[trex]

it could be that they did not copy Bosch but made a plug compatible as they said.
The Bosch battery may have a data logger running on one of those smaller wires. Without tracing the yellow/green/purple wires, we just don't know.
It may be worth the effort to check which pins on the charger have 42V across them, that will identify the remaining wire as the datalogger's.
It could also well be that the datalogger is only accessed when someone runs the diagnostics. In that case, the plug compatible does not need a datalogger.

 

[El Champiero]

Just checked the charger with the voltmeter:

There are three terminals on the charger. Whilst putting the red test probe on the centre terminal on the charger plug and the black probe on the terminal which goes into positive terminal on the battery the reading was 4.63V. When this was done on the negative terminal on the charger the reading was 4.94V.

Any ideas ?

 

[El Champiero]

I think you are correct re: the data logger. It is essentially pointless with regards to the overall functioning of the battery so I guess the factory in China haven't bothered with it.

 

[flecc]

There are definitely 5 pins on the connector. You have pins 4 and 2 as positive and negative leads. Pins 1,3 and 5 take much smaller diameter wires (coloured green, purple and yellow. These wires are connected to the BMS - not sure what they do

That looks similar to the Panasonic unit's battery setup.

With that, counting from the bike's rear, pin 1 is current positive, pin 2 charging positive, pin 3 feeds the battery content information to the handlebar unit, pin 4 is the negative and pin 5 monitors the battery.

 

[El Champiero]

Seems to me like you have got it spot on flecc.

I am also guessing that the BMS from the Chinese battery clone has cell balancing incorporated into it as well as the usual protection functions.

 

[KirstinS]

Interesting


Are you saying the BMS fails & no longer allows the remaining good cells to be charged.
Or
The BMS kills the remaining good cells making the whole thing useless.

I'm asking because in the past I've built RC packs (NiMh) using good cells from dead power tools.

It's neither. The chip in the BMS simply shuts down whole BMS permanently after 5 failed charges (for whatever reason)

There is no way to reset that chip , once it decides the pack is dead is nothing you can do to change its mind

So you can find duff cell and replace it but the BMS will prevent charging (or rather the chip will)

Worse still many packs are designed so the BMS runs off one cell all the time. Leave it on a shelf and that cells goes below 3v after a few weeks and whole pack is a write off

 

[El Champiero]

It's neither. The chip in the BMS simply shuts down whole BMS permanently after 5 failed charges (for whatever reason)

There is no way to reset that chip , once it decides the pack is dead is nothing you can do to change its mind

So you can find duff cell and replace it but the BMS will prevent charging (or rather the chip will)

Worse still many packs are designed so the BMS runs off one cell all the time. Leave it on a shelf and that cells goes below 3v after a few weeks and whole pack is a write off

Been reading about that too - the only work-around would be to salvage a working BMS from another pack or purchase a non genuine battery which will almost certainly not have the shutdown feature installed. Then when these cells deteriorate, replace with better quality ones. Makita and others will say its due to safety but we all know what they really want out of this.

 

[KirstinS]

Yes indeed just buy non matika branded packs. They often at least as good. And don't have the chip as it represents a pointless cost - y

 

[RobF]

Looks like the more popular down tube Bosch pattern battery has a minimum order of 10.

I don't understand this alibaba stuff, so if one ordered 10 what would the final bill be delivered to a UK address?

http://www.alibaba.com/product-gs/1634143121/Longer_service_life_36V_eletronic_bike.html