36V Bosch tool battery for e-bike use
- Thread starter WheezyRider
- Start date
I'm finding this very intriguing, because two 6Ah packs with 20A continuous discharge capability, would do for my shorter journeys. What makes me nervous is the soldering!
Same kit on ebay for £25.20 from China. It's almost a dead cert getting refunded on ebay - much easier than AliExpress, none of their burning hoops to jump through.
GBH36V-LI Battery Case PCB Circuit Board-tools For Bosch 36V GBH36V-LI Li-ion | eBay
Find many great new & used options and get the best deals for GBH36V-LI Battery Case PCB Circuit Board-tools For Bosch 36V GBH36V-LI Li-ion at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk
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If you settled for 6Ah, you could have 2p x 3 Ah cells with a higher current rating than for 2p x 3.5 Ah cells for giving 7Ah, so potentially higher than 20A for a 2p setup. However, it would be good to know what the PCB rating is - that will most likely be the component that becomes the bottle neck, I'm not sure what it's rating is.I'm finding this very intriguing, because two 6Ah packs with 20A continuous discharge capability, would do for my shorter journeys. What makes me nervous is the soldering!
Same kit on ebay for £25.20 from China. It's almost a dead cert getting refunded on ebay - much easier than AliExpress, none of their burning hoops to jump through.
GBH36V-LI Battery Case PCB Circuit Board-tools For Bosch 36V GBH36V-LI Li-ion | eBay
Find many great new & used options and get the best deals for GBH36V-LI Battery Case PCB Circuit Board-tools For Bosch 36V GBH36V-LI Li-ion at the best online prices at eBay! Free delivery for many products.www.ebay.co.uk
Well that sort of sinks it, until we know more. They could send either one of these. "Random delivery":
Unsure which this is the other side of, looks like the second one:
No details offered re: rating on ebay.
If you have two packs in parallel it would be less of a concern. Will need to do some more digging...what is the motor rating of a 36V lawn mower? I think these may be 800W. I'll have a look.Well that sort of sinks it, until we know more. They could send either one of these. "Random delivery":
Unsure which this is the other side of, looks like the second one:
No further details offered re: rating on ebay.
Even the manual doesn't say - perhaps the motor is labelled? Or you might just find a part number...
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Given that part of the appeal of using something like a Bosch tool battery is the relatively small size, high current capacity (for the capacity of the pack) light weight and expected reliability why do you then want to start throwing likely substandard Chinese copy parts into the equation. There are plenty of other tool batteries that are much cheaper than Bosch why not just use them instead.
I prefer the recelling option of an old pack with dead cells with known good quality cells. The Chinese kit option is interesting as it has all the Nickel strip precut and if some of the external case parts on an old battery are a bit tired, they could be replaced with new. As for the PCB, it could be a poor quality Chinese copy, or it could be the exact same PCB that is going into the Bosch product - that is the unknown. Although these genuine Bosch batteries were initially made in Poland, they have been made in China for quite some time:
It would be good to know, agreed.
This guy reports at 07:28 that he is pulling around 35A through a pair of 36V 6Ahr on a small quadbike;
Interesting that they were in series, not parallel, so it was 35 A for each pack. He thinks the BMS cut off must be 40A.
However, if the cells inside are Samsung 3 Ah 18650, these seem to have a max cont current rating of 15A, so in 2p would give 30 A max. I think this guy is pushing his luck at 35A, although he didn't go that high for very long and cells can do short bursts at higher than recommended cont current. There is a later video where a year later he does a capacity check and they were giving less than 6 Ah, although he didn't check from new and he doesn't say how many cycles in total he has done. In the bike though he does seem to be doubling up the batteries to give two series and two parallel.
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What is interesting from the video about the strip down and recelling of a genuine Bosch pack is you can see the PCB has a fuse built in. It would be good to know what value it has. The eBay/AliExpress board does not seem to have this. There seem to be quite a few other differences as well. From the Big Clive video of the Aldi pack strip down it looks like microcontrollers are used to monitor the pack. This would require proprietary firmware. If the PCB is a copy, either they would have had to steal this software, or tried to code their own. Interesting...
Another thing I've been thinking about is the amount of coms between the pack and the tool in its designed for use. These Bosch packs only have three pins. More modern stuff seems to have more pins and some functions are shared between the tool and the pack PCB. One thing is temperature cut off, another is low voltage cut off. Some of the "Bosch" AliExpress boards say that they do not have LVC capability, this is monitored by the tool. Also, I think some tools have a shut down capability built in if the pack temp goes too high. From looking at the Bosch PCB it looks like the NTC thermistor is connected directly to the centre pin, which probably communicates pack over heating to the charger and the tool.
What would be useful to know is if the pack itself shuts off power if the temp goes too high. I don't think it will, I can't see a big power MOSFET on the board to switch this. This is something to think about as if there is a thermal runaway at high current on a bike, things could get bad very quickly.
A different approach seems to have been taken by Einhell. They are only using 18V packs, however, everything would appear to be controlled at a pack level, without any tool/pack coms. There are only two pins on the tool, so unless data is somehow sent over the power connections, battery management must be confined to the controller in the pack.
What would be useful to know is if the pack itself shuts off power if the temp goes too high. I don't think it will, I can't see a big power MOSFET on the board to switch this. This is something to think about as if there is a thermal runaway at high current on a bike, things could get bad very quickly.
A different approach seems to have been taken by Einhell. They are only using 18V packs, however, everything would appear to be controlled at a pack level, without any tool/pack coms. There are only two pins on the tool, so unless data is somehow sent over the power connections, battery management must be confined to the controller in the pack.
This is the Einhell system. They have taken an 18V approach and double up packs in their 36V tools. Not sure how it handles things if one pack is at a lower state of charge than the other.
They have an option to reduce capacity and extend battery life. Probably charges to a lower cut off voltage when charging and has a higher LVC. I wonder what happens in a 36V tool if one pack is set to 5Ah and the other 8Ah? Maybe there is some sensing in the tool, comparing voltage of each pack...
They have an option to reduce capacity and extend battery life. Probably charges to a lower cut off voltage when charging and has a higher LVC. I wonder what happens in a 36V tool if one pack is set to 5Ah and the other 8Ah? Maybe there is some sensing in the tool, comparing voltage of each pack...
My duff Bosch battery arrived this morning, I bought it for around £10 to check stuff. The battery and two mounting plates I found are shown below.
The black one is just for storing the battery on a wall etc. its nice and thick and has countersunk mount holes, £3.50 on ebay.
The red one, £9 on eBay, is for a 18V Bosch battery but it does fit, a little bit of smoothing in the inner rails help the battery slot in and out easily. The blades do connect to the battery contacts.
The black one is more suited to carry the weight of the battery. In the picture below is a possible battery connection hack. There are some copper plated lugs in the battery contacts that will take an M5 bolt. Maybe you could drill a circa M6 hole in the right place at the bottom of the holder and use a nut to secure the lug in place. The same hack could be used to get access to the centre connector which is the temperature sensor, on either the red or black brackets.
For my eBrompton I am currently moving the battery from a handlebar bag to one on the front baggage block. The weight of the battery is taken by an aluminium bracket.
A bag will then be fitted over the aluminium bracket. The same approach could work with a Bosch battery, with the holder fitted to the bottom of the aluminium bracket. The bag I am using for eBrompton would take the Bosch battery too;
Next will be taking the battery to bits to see how the temperature sensor works.
The black one is just for storing the battery on a wall etc. its nice and thick and has countersunk mount holes, £3.50 on ebay.
The red one, £9 on eBay, is for a 18V Bosch battery but it does fit, a little bit of smoothing in the inner rails help the battery slot in and out easily. The blades do connect to the battery contacts.
The black one is more suited to carry the weight of the battery. In the picture below is a possible battery connection hack. There are some copper plated lugs in the battery contacts that will take an M5 bolt. Maybe you could drill a circa M6 hole in the right place at the bottom of the holder and use a nut to secure the lug in place. The same hack could be used to get access to the centre connector which is the temperature sensor, on either the red or black brackets.
For my eBrompton I am currently moving the battery from a handlebar bag to one on the front baggage block. The weight of the battery is taken by an aluminium bracket.
A bag will then be fitted over the aluminium bracket. The same approach could work with a Bosch battery, with the holder fitted to the bottom of the aluminium bracket. The bag I am using for eBrompton would take the Bosch battery too;
Next will be taking the battery to bits to see how the temperature sensor works.
No cutout in this 2.6Ahr battery, the +ve and -ve from the cell bank goes straight to the external battery terminals.
Fuse is labeled 1 607 502 093.
Fuse is labeled 1 607 502 093.
Did a search for the fuse part number turn up any info? Had a quick look, but couldn't find it. Wow, so no BMS control of the output. The board is only there for charging it seems, and only to tell the charger there is a problem, - possibly gives a tool data on battery temp during discharge.
The wiring of the central connector suggests its for detecting when the battery is plugged in and not for sending a temperature warning to the tool.
From the picture below you can see that the bottom leaf of the central connector is connected to the -ve battery connector at the bottom of the PCB and the top leaf of the central connector goes off to the 'controller'. If you put a solid blade in the connector both leafs are shorted together and presumably the controller knows there is a tool connected. With that central connector grounded it not likely its being used to signal to the tool that there is a temperature issue.
What the charger does with that central connector might be different however.
Thats disapointing, the temperature sensor does work, if you heat it up then press the button for the voltage display the temperature warning LED does come on, but why bother ?
Rather a lot of components for what appears to be just a voltage level meter and temperature sensor.
From the picture below you can see that the bottom leaf of the central connector is connected to the -ve battery connector at the bottom of the PCB and the top leaf of the central connector goes off to the 'controller'. If you put a solid blade in the connector both leafs are shorted together and presumably the controller knows there is a tool connected. With that central connector grounded it not likely its being used to signal to the tool that there is a temperature issue.
What the charger does with that central connector might be different however.
Thats disapointing, the temperature sensor does work, if you heat it up then press the button for the voltage display the temperature warning LED does come on, but why bother ?
Rather a lot of components for what appears to be just a voltage level meter and temperature sensor.
This is looking more and more like a Bosch hand grenade!
So if the tool develops a short, or the output is deliberately shorted, there is nothing to stop the whole thing going bang (other than the fuse which must be quite a few amps). There is effectively no BMS on discharge, so if one cell goes out of balance, power gets dumped into it and it could burn. There is no balance function...