Sorry if I'm reviving an old thread, but I use DeWalt 20V Max and can definitely state that DeWalt does perform cell balancing on their batteries. With Makita pushing lightning-fast (9 amp!) charging speeds, it's a bit disappointing to find that their battery control circuitry draws on only one cell, causing the whole pack to fail prematurely if it isn't used regularly. It's also an odd decision to disable the entire pack on three failed charge attempts—I understand the safety concern, but this isn't necessary if the battery can simply communicate to the tool/charger that one or more cells have failed. Unfortunately, this seems to be necessary because not all Makita tools can digitally communicate with their batteries, and not all batteries can communicate with the tool; older Makita 18V LXT tools and batteries without a star mark don't have the company's "STAR Protection Computer Controls". (I'm not here to bash Makita—they make great tools, but are a bit backwards in their battery design. Then again, they were the first to introduce an all-lithium 18V battery platform. The 18V LXT platform dates back to 2005, so their initial implementation was apparently missing the digital communication features new batteries and tools have.)
The DeWalt battery has B+ and B- connectors where the main 18-20V output is supplied to the tool. However, there's a total of eight connectors on the battery, four of which are specifically for cell balancing. Along with the B+ and B- connectors, the C1-C4 contacts are hooked up to the individual cells: from negative to positive, B- to C1 for the first cell, C1 to C2 for the second cell, C2 to C3 for the third cell, C3 to C4 for the fourth cell, and C4 to B+ for the fifth cell. They are hooked up internally in series and all of the pins are present on the charger, which performs the cell balancing. Fresh off the charger, each cell should have a voltage of about 4.1 V for a total voltage of 20.5 V. (Side note: The remaining two pins on the battery are marked ID and TH. I'm guessing ID is to identify the battery type, perhaps for communication between the battery and tool/charger to distinguish between 20V Max and the nearly electrically compatible 12V Max, which might simply not have pins for C3 and C4. The TH contact is probably for temperature sensing. My DeWalt DCD790 drill has pins for B+, B-, TH, and C3, but I'm don't know why it needs the C3 contact.)
What I'd like to know is whether Makita has these cell-balancing contacts on their 18V LXT batteries. Can someone check one of their Makita batteries to find out?
--DragonLord
Edit: So I read through the thread again, and it seems that the newer batteries and chargers do have cell-balancing connectors. If only Makita would fix the single-cell discharge issue...
I believe DeWalt uses the Sanyo (now Panasonic) UR18650RX cells for their 20V Max XR 2 Ah and 4 Ah batteries. These cells are rated for 22 A maximum discharge rate, so the DCB204 premium 4 Ah battery (which has 10 cells in 5S2P) can reliably supply up to 44 amps of current. Not sure what the upcoming DCB205 5 Ah batteries will use, though.
The DeWalt battery has B+ and B- connectors where the main 18-20V output is supplied to the tool. However, there's a total of eight connectors on the battery, four of which are specifically for cell balancing. Along with the B+ and B- connectors, the C1-C4 contacts are hooked up to the individual cells: from negative to positive, B- to C1 for the first cell, C1 to C2 for the second cell, C2 to C3 for the third cell, C3 to C4 for the fourth cell, and C4 to B+ for the fifth cell. They are hooked up internally in series and all of the pins are present on the charger, which performs the cell balancing. Fresh off the charger, each cell should have a voltage of about 4.1 V for a total voltage of 20.5 V. (Side note: The remaining two pins on the battery are marked ID and TH. I'm guessing ID is to identify the battery type, perhaps for communication between the battery and tool/charger to distinguish between 20V Max and the nearly electrically compatible 12V Max, which might simply not have pins for C3 and C4. The TH contact is probably for temperature sensing. My DeWalt DCD790 drill has pins for B+, B-, TH, and C3, but I'm don't know why it needs the C3 contact.)
What I'd like to know is whether Makita has these cell-balancing contacts on their 18V LXT batteries. Can someone check one of their Makita batteries to find out?
--DragonLord
Edit: So I read through the thread again, and it seems that the newer batteries and chargers do have cell-balancing connectors. If only Makita would fix the single-cell discharge issue...
I use quite a number of Sanyo UR18650SAX. Only 1300mAh, but 25A continuous rated and cheap, they make good robust high performance RC-type packs for low cost. Sanyo also has the successor WX and RX, 1500 and 2000mAh 20A cont.
I believe DeWalt uses the Sanyo (now Panasonic) UR18650RX cells for their 20V Max XR 2 Ah and 4 Ah batteries. These cells are rated for 22 A maximum discharge rate, so the DCB204 premium 4 Ah battery (which has 10 cells in 5S2P) can reliably supply up to 44 amps of current. Not sure what the upcoming DCB205 5 Ah batteries will use, though.
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