August 3, 20232 yr 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. Even the manual doesn't say - perhaps the motor is labelled? Or you might just find a part number... https://www.bosch-diy.com/storage/en-gb/advancedrotak-36-850-100050418-original-pdf-411426-en-gb.pdf Edited August 3, 20232 yr by guerney
August 3, 20232 yr 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.
August 3, 20232 yr Author 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:
August 4, 20232 yr 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. 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;
August 4, 20232 yr Author 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. Edited August 4, 20232 yr by WheezyRider
August 6, 20232 yr Author 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...
August 6, 20232 yr Author 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.
August 6, 20232 yr Author 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... https://www.einhell.co.uk/p/4511600-18v-5-8ah-multi-ah-pxc-plus/
August 10, 20232 yr 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.
August 10, 20232 yr 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.
August 10, 20232 yr Author 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.
August 10, 20232 yr 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.
August 10, 20232 yr Author 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. [ATTACH=full]53275[/ATTACH] 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...
August 10, 20232 yr 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. 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... This is a 2.6Ahr battery, I guess its possible the others are different ?
August 10, 20232 yr 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. [ATTACH type=full" alt="53274]53274[/ATTACH] That's interesting. Don't forget the battery and the device that it's working work as a team. It's probable that the LVC is in the device, not the battery. It looks like it does the charge control by temperature rather than voltage. That Bosch battery kit is the same. Edited August 10, 20232 yr by saneagle
August 10, 20232 yr As far as I know, tool batteries are usually designed for very quick charge/discharge times and the temperature sensors play a very important role.
August 10, 20232 yr 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... [ATTACH type=full" alt="53223]53223[/ATTACH] The Ebay kit has a fuse soldered to the red wire half way along.
August 10, 20232 yr Fuse is labeled 1 607 502 093. Speculation on another forum: https://www-pedelecforum-de.translate.goog/forum/index.php?threads/bosch-36v-2-6ah-sicherung-defekt.29165/&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp ...there are rather a lot of datasheets to trawl through: BOSCH 1 607 502 093 Datasheets https://www.datasheetarchive.com/BOSCH%201%20607%20502%20093-datasheet.html
August 10, 20232 yr Speculation on another forum: https://www-pedelecforum-de.translate.goog/forum/index.php?threads/bosch-36v-2-6ah-sicherung-defekt.29165/&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp ...there are rather a lot of datasheets to trawl through: BOSCH 1 607 502 093 Datasheets https://www.datasheetarchive.com/BOSCH%201%20607%20502%20093-datasheet.html It doesn't matter what it is. We know that the battery can do 30A. You don't need anything near that, so stick a 25A one in or whatever floats your boat. You can unsolder it and solder in a car blade type fuse or any other type. A fuse is a fuse.
August 10, 20232 yr Author As far as I know, tool batteries are usually designed for very quick charge/discharge times and the temperature sensors play a very important role. You would think the temp sensor would play an important role, but it seems as if the sensor circuit is grounded when attached to a charger or a tool?
August 10, 20232 yr Author A fuse is a fuse. Well there are different types, like slow or quick blow... It's likely to be 30A as are there are 2 strings of cells, each with a max rating of 15A. Do a search for glass fuses, should be able to find something at 30A:
August 10, 20232 yr You would think the temp sensor would play an important role, but it seems as if the sensor circuit is grounded when attached to a charger or a tool? I cant answer that. There website below claims 'Protection against overheating through temperature monitoring' in link below. Many mobile phone batteries also have an extra terminal for temp sensing. My understanding is that if you want quick charging, its best to monitor the temperature. https://www.bosch-diy.com/ie/en/landing/power-for-all/power-for-all
August 10, 20232 yr Author I cant answer that. There website below claims 'Protection against overheating through temperature monitoring' in link below. Many mobile phone batteries also have an extra terminal for temp sensing. My understanding is that if you want quick charging, its best to monitor the temperature. https://www.bosch-diy.com/ie/en/landing/power-for-all/power-for-all The PCB on the 18V battery is very different, for example, it seems to have a proper BMS, monitoring individual cells.
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