Thank you for a nice and clear experiment. I assume the protection signal can be connected to a brake sensor.

If you can work out what the data format is and read it with a suitable small micro, then you ought to be able to sense a high temperature condition and use a transistor to trigger one of the brake sensors. Ideally you would want to turn off the display\controller, but that might be a significant hack.

 

I presume ARRC conversions have custom hardware and software in their controller to read the data and flag an over temperatue condition.

 

Does anyone know anyone with an ARCC Brompton conversion ?

Edited August 20, 20232 yr by StuartsProjects

I have found, by experiment, that if the BUS line on the battery is connected to +5V via a high value resistor, 27K in this case, the battery wakes up and sends 4 blocks of data, which might be bytes. But that is all it sends, so it looks likley that the battery is waiting for a response from the charger, before it continues to send temperature data, which is what happens during charging.

I have found, by experiment, that if the BUS line on the battery is connected to +5V via a high value resistor, 27K in this case, the battery wakes up and sends 4 blocks of data, which might be bytes. But that is all it sends, so it looks likley that the battery is waiting for a response from the charger, before it continues to send temperature data, which is what happens during charging.

 

That's interesting. If you set the BUS line high momentarily, does the battery send 4 blocks of data again?

That's interesting. If you set the BUS line high momentarily, does the battery send 4 blocks of data again?

 

If you leave the resistor pullup in place, then only one block of data is sent.

 

Remove the pull up and then put it back and another block of data is sent.

 

Hence the battery does appear to be waiting for a response from the charger before it keeps sending what appears to be the temperature data.

If you leave the resistor pullup in place, then only one block of data is sent.

 

Remove the pull up and then put it back and another block of data is sent.

 

Hence the battery does appear to be waiting for a response from the charger.

 

Ok, is the data block always the same for the same temperature of the thermistor?

Ok, is the data block always the same for the same temperature of the thermistor?

 

Not checked, but whether it is or is not I doubt is significant.

 

For an eBike situation the key would be decoding the stream of data sent approximatly every 5 seconds, which is much longer than the intial wake up block.

Might be worth replacing the thermistor temporarily with a potentiometer so you don't have to keep heating it. If you need to encode a range of say 100 C with 1 Deg resolution, you'd need at least 7 bits?

 

Or maybe it doesn't even need to measure the actual temp and it just gives a good/no good signal? Or maybe it is transmitting temp - does ARC stand for accelerating rate calorimetry? So the rate of change of temp is important if that is the case.

Let's say you simply connect the middle pin to a pullup resistor. The battery sends a block then waits. You then heat up the thermistor. Would the line goes low?

Let's say you simply connect the middle pin to a pullup resistor. The battery sends a block then waits. You then heat up the thermistor. Would the line goes low?

 

Not that simple unfortunately

Well before going into the detail of the intial wakeup, it really needs to be shown if the BUS data is bidirectional or not.

Well before going into the detail of the intial wakeup, it really needs to be shown if the BUS data is bidirectional or not.

 

My guess is that the board waits for a high signal on the BUS, then transmits some data, then waits for the BUS to go high again and then sends updated data.

It seems unusual to have just a single BUS line. Most protocols normally have at least two connections. I wonder if it is some form or variation of 1-wire coms:

 

https://ww1.microchip.com/downloads/en/appnotes/01199a.pdf

It seems unusual to have just a single BUS line.

 

Not so unusual in the sensor world.

 

The BUS line appears to be used for temperature sensing and eleswhere those are often read with a 1 wire protocol, such as that used by the DS18B20 temperature sensors etc.

Batteries of less than 100Wh/8.4Ah capacity are allowed on airlines apparently, so if you wanted to use your own ebike for pottering short distances on holiday, say from your palatial holiday villa to the local market and back, and your bike folded into a suitcase...

Batteries of less than 100Wh/8.4Ah capacity are allowed on airlines apparently, so if you wanted to use your own ebike for pottering short distances on holiday, say from your palatial holiday villa to the local market and back, and your bike folded into a suitcase...

Grin Technologies sell special 100wh batteries for that, which clip together to make bigger ones.

LiGo Batteries - Grin Products - Product Info (ebikes.ca)

Batteries of less than 100Wh/8.4Ah capacity are allowed on airlines apparently, so if you wanted to use your own ebike for pottering short distances on holiday, say from your palatial holiday villa to the local market and back, and your bike folded into a suitcase...

 

I think 100Wh corresponds to just over 2.6 Ah for 36 V packs. 8.4 Ah sounds a bit large!

I think 100Wh corresponds to just over 2.6 Ah for 36 V packs. 8.4 Ah sounds a bit large!

 

Oops, yes.

 

Using Bosch batteries with your folding ebike on holiday, is a good reason to upgrade cells in old genuine Bosch packs. Airlines will go by capacity quoted on the battery pack labels, probably. Alternatively, rent a couple of Bosch tool batteries near the airport or your private infinity pool, for about £60 a week...

Using Bosch batteries with your folding ebike on holiday, is a good reason to upgrade cells in old genuine Bosch packs. Airlines will go by capacity quoted on the battery pack labels, probably.

 

The thought of DIY 'upgraded' lithium batteries on aeroplanes, what could possibly go wrong .................

The thought of DIY 'upgraded' lithium batteries on aeroplanes, what could possibly go wrong .................

 

The thought of weak DIY welds makes me nervous, which is why I'm unlikely to ever make a battery pack - it's either welds or compression using kits like Vruzend's, and the one below, but never both, which might be a good idea should welds fail?

 

https://vruzend.co.uk/

 

 

Well it looks like summer is over, so it's back to sorting my 'cave' and as a first step, doing something with the (good) 18650 cells I recovered some time back from a prematurely dead Swytch Mk 1 battery pack. They still look good(?) after sitting some months as single cells at about 3.4V (ie after discharge test).

 

Now that I am regularly using 36V Bosch lawnmower/tool batteries for local trips on my converted touring bike - I have acquired a total of 4 genuine + 1 look-alike batteries - I am wondering could I safely piggy-back a selected set of the spare 18650s onto a genuine Bosch battery for use (and charging with a genuine Bosch charger)?

 

Has the missing BMS on the Bosch batteries been solved? Is it a matter of hand balancing cell sets?

On the older lower capacity packs, there is no BMS, but there is a temperature monitor.

 

I seem to recall seeing a picture of the battery controller board for the more modern 6AHr battery and that appeared to have wires to each cell group, which the lower capacity batteries do not have. However it seems unlikley that the 6Ahr battery does do balancing, although it possible it detects balance errors and reports through the central battery connector.

 

I have seen people using these batteries with just the power connectors but that implies that any error the battery controller board detects is not picked up. Presumably if the battery detects an error it signals that error so that the power tool can stop powering the motor.

 

For eBike use I would suggest that you need to implement some form of switch off of the eBike motor, say via a brake switch sensor input, if the battery reports a fault. To do that you need to work out the signal protocol that the battery uses.

 

I guess it depends how lucky you feel.

Hello guys. Thanks a lot for sharing all the information; it is very useful.

 

I bought a mower (easy-rotak 36-550) but without a battery. I created a custom battery for the machine, but the problem is that it doesn't start. I figured out that the main issue is that I do not have the middle pin connected to the machine.

 

With an original Bosch battery, the mower works as expected.

 

Do you know how it is possible to bypass the middle pin (BUS)? Is there a workaround?

 

Thanks a lot!

Do you know how it is possible to bypass the middle pin (BUS)? Is there a workaround?

 

You would need to replicate the control unit inside a Boch battery that the mower expects to see.

 

Sounds like a question for a lawnmower or power tool forum.

You would need to replicate the control unit inside a Boch battery that the mower expects to see.

 

Sounds like a question for a lawnmower or power tool forum.

 

I wonder if you just took a control board from a dead Bosch battery and connected it in parallel to the DIY pack whether it would provide the centre pin signal? All it seems to do is monitor temperature and if that's at room temperature, it wouldn't report an error.