Hi, I would like to share with you small modification to your Bosch tool 12V and 18V chargers.
You can use it for almost all Bosch chargers what I have seen, for example part numbers GAL 18V-20, GAL 18V-40, GAL 1880, GAL 18V-160, AL 1820, AL1115CV, AL1130CV.
Bosch (today also other brands using the same system like Wurth, Fein) does not care if you destroy your batteries, because they can sell you new ones. So the marketing is telling you only about speed of the charging, so you will not wait for your batteries to charge too long. Me as a customer want the tools and batteries to last as long as possible, so with my electrical knowledge I share this.
Idea:
The idea is to lower the charging current, as this is better for the cells, it also improves heat management (cells does not overheat) and cells are balanced better. The problem of batteries is with use and age they increase internal resistance and all cells in one battery pack start to differ, so it makes the charging more problematic. If you push the cells to maximum, their lifetime will be smaller.
While you look into the Panasonic/Sanyo or Samsung cells datasheet, you will get the optimal charging current.
Example Samsung INR21700-50E (4900mAh) standard charging 2450mA, maximum 4900mA (not for life cycle).
The smaller Bosch batteries (2Ah, 4Ah Procore) are single cell (5x), middle size (4Ah-5.5Ah) are dual cell (5x), 8Ah are triple cell (5x) in paraller.
Therefore by example 18V 4Ah Procore battery pack uses 5 cells in series (no doubles in paraller), therefore you should use 2A charging recommended.
But when I am not in hurry, I keep the charging current smaller, 1A is very generous for the cells.
Modification:
The modification is simple.
After disassembly of the charger body and removal of the PCB (no need to dicsonnect or desolder anything), locate the feedback resistors near the battery terminal.
There are what I have seen usually 2 resistors for 2A charger, 4 resistors for 4A charger etc. They are on the thick traces and they are in parraler. Resistor value is 0.15 Ohm. I am not sure if that is for each variant.
So by removal of some of the resistors, you will lower the charging current. It is as simple as 4 resistors on 4A charger -> remove 3 resistors, keep 1 placed, you have now 1A charger.
There is also possibility to add external switch on the body of the charger, so you can switch on fast charging, when needed. But be careful not to swtich the traces together, just switch the original resistors into their places or disconnect them by the switch.
I have attached photos of the GAL 18V-40 (SMT resistors) and AL 1130 CV chargers (THT resistors).
Photos are after the modification.
I kept the resistors on the PCB just placed (not connected), so I can return it back if needed.
Others:
I think this modification or upgrade can be done for any brand, Dewalt, Milwaukee, Makita, Hikoki... The chargers are usually simple power supplies with readout of the battery temperature and battery data. The circuit will be pretty similar.
You can use it for almost all Bosch chargers what I have seen, for example part numbers GAL 18V-20, GAL 18V-40, GAL 1880, GAL 18V-160, AL 1820, AL1115CV, AL1130CV.
Bosch (today also other brands using the same system like Wurth, Fein) does not care if you destroy your batteries, because they can sell you new ones. So the marketing is telling you only about speed of the charging, so you will not wait for your batteries to charge too long. Me as a customer want the tools and batteries to last as long as possible, so with my electrical knowledge I share this.
Idea:
The idea is to lower the charging current, as this is better for the cells, it also improves heat management (cells does not overheat) and cells are balanced better. The problem of batteries is with use and age they increase internal resistance and all cells in one battery pack start to differ, so it makes the charging more problematic. If you push the cells to maximum, their lifetime will be smaller.
While you look into the Panasonic/Sanyo or Samsung cells datasheet, you will get the optimal charging current.
Example Samsung INR21700-50E (4900mAh) standard charging 2450mA, maximum 4900mA (not for life cycle).
The smaller Bosch batteries (2Ah, 4Ah Procore) are single cell (5x), middle size (4Ah-5.5Ah) are dual cell (5x), 8Ah are triple cell (5x) in paraller.
Therefore by example 18V 4Ah Procore battery pack uses 5 cells in series (no doubles in paraller), therefore you should use 2A charging recommended.
But when I am not in hurry, I keep the charging current smaller, 1A is very generous for the cells.
Modification:
The modification is simple.
After disassembly of the charger body and removal of the PCB (no need to dicsonnect or desolder anything), locate the feedback resistors near the battery terminal.
There are what I have seen usually 2 resistors for 2A charger, 4 resistors for 4A charger etc. They are on the thick traces and they are in parraler. Resistor value is 0.15 Ohm. I am not sure if that is for each variant.
So by removal of some of the resistors, you will lower the charging current. It is as simple as 4 resistors on 4A charger -> remove 3 resistors, keep 1 placed, you have now 1A charger.
There is also possibility to add external switch on the body of the charger, so you can switch on fast charging, when needed. But be careful not to swtich the traces together, just switch the original resistors into their places or disconnect them by the switch.
I have attached photos of the GAL 18V-40 (SMT resistors) and AL 1130 CV chargers (THT resistors).
Photos are after the modification.
I kept the resistors on the PCB just placed (not connected), so I can return it back if needed.
Others:
I think this modification or upgrade can be done for any brand, Dewalt, Milwaukee, Makita, Hikoki... The chargers are usually simple power supplies with readout of the battery temperature and battery data. The circuit will be pretty similar.
Attached Files
