Coloshaver
Well-known member
A little over a year ago, my daughter bought a DeWalt 20V Max drill and impact driver kit (DCD771 Drill & DCF885 Impact Driver plus two batteries and a charger) to take to her business in Costa Rica. Unfortunately, they failed relatively quickly, but being so far away warranty service was not an option. The kit was put on a shelf and the batteries went flat. I visited over Thanksgiving and brought everything back to troubleshoot.
First, the batteries wouldn’t charge. So using the “connect a good battery to a bad battery trick” I used a low current 20V power supply to get the packs up to about 10V. Then they both took a charge on the charger. Each charged for about 2 hours. They both metered at ~20V.
The first time I connected them to the Drill, it worked. Then I tried the Impact. I worked the first time I pulled the trigger but not again. OK I thought, even though the batteries “charged” they are shot and lost charge right away, But, they both worked on the Drill again and they metered at 20V. I took the Impact apart so I could get to the battery connector inside the tool. I connected a battery, pulled the trigger and metered the B+ and B- terminals. The Impact wouldn’t run, but the battery stayed at 20V - no drop. Then I tried the Drill again - now they didn’t work in the Drill.
I put the batteries back on the charger. They both showed “Charged” and metered at 20V. But, neither the Drill nor the Impact work. I used fine emery paper to clean the battery contacts and the tool contacts. They are all bright and shiny.
I noticed that, as I inserted the batteries in the tools (both tools), just before the batteries lock, the LED flashes. Then, I started experimenting with installing the batteries. Holding the trigger on (both tools), as I slowly slide the battery into the tool, about ¼” before it seats, the tool will run. It will continue to run as the battery is fully seated. I can modulate the speed, but, if I release the trigger, it won’t run again. I can repeat this over and over. Hold the trigger, insert the battery, just before the battery seats,the tool runs. I held the trigger for a couple minutes. It runs steady. Release the trigger, it won’t run again. Both batteries still meter 20V and show charged on the charger.
I’ve checked the solder connections in the tool. They all look good. One youtube suggested broken wires on the connectors to the middle cells. I inspected these and they are fine.
The switch assembly has a heat sink on it so there must be some kind of solid state device. Maybe they failed, but in both tools?
I am baffled. Any ideas?
Thanks,
First, the batteries wouldn’t charge. So using the “connect a good battery to a bad battery trick” I used a low current 20V power supply to get the packs up to about 10V. Then they both took a charge on the charger. Each charged for about 2 hours. They both metered at ~20V.
The first time I connected them to the Drill, it worked. Then I tried the Impact. I worked the first time I pulled the trigger but not again. OK I thought, even though the batteries “charged” they are shot and lost charge right away, But, they both worked on the Drill again and they metered at 20V. I took the Impact apart so I could get to the battery connector inside the tool. I connected a battery, pulled the trigger and metered the B+ and B- terminals. The Impact wouldn’t run, but the battery stayed at 20V - no drop. Then I tried the Drill again - now they didn’t work in the Drill.
I put the batteries back on the charger. They both showed “Charged” and metered at 20V. But, neither the Drill nor the Impact work. I used fine emery paper to clean the battery contacts and the tool contacts. They are all bright and shiny.
I noticed that, as I inserted the batteries in the tools (both tools), just before the batteries lock, the LED flashes. Then, I started experimenting with installing the batteries. Holding the trigger on (both tools), as I slowly slide the battery into the tool, about ¼” before it seats, the tool will run. It will continue to run as the battery is fully seated. I can modulate the speed, but, if I release the trigger, it won’t run again. I can repeat this over and over. Hold the trigger, insert the battery, just before the battery seats,the tool runs. I held the trigger for a couple minutes. It runs steady. Release the trigger, it won’t run again. Both batteries still meter 20V and show charged on the charger.
I’ve checked the solder connections in the tool. They all look good. One youtube suggested broken wires on the connectors to the middle cells. I inspected these and they are fine.
The switch assembly has a heat sink on it so there must be some kind of solid state device. Maybe they failed, but in both tools?
I am baffled. Any ideas?
Thanks,
