Why won’t my 20V battery power high-amp tools?
Asked by CraftyHedgehog72
I have a 10Ah 20V battery that measures 19.53V on my multimeter, but it struggles with high-amp devices like my leaf blower and reciprocating saw. The tools briefly start before losing power. However, it works fine with my drill and oscillating tool. I'm wondering if these batteries have some internal protection that might be failing. The other 10Ah battery I have operates all tools without any issues. Any ideas?
Answers
Make sure you're using a two-stage charger. I have a 10Ah that only charges correctly with that type. If you're not, switching chargers could help your battery's performance.
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Sounds like your battery might be experiencing cell issues. DeWalt often builds the protection in the tools rather than the batteries. It’s possible that some cells are failing—good voltage under light loads but crashing when you put them under stress. You might want to check the battery's health further.
TechieTiger34: That makes sense! I had a similar issue where one of the cells went bad. It really affects performance on high-demand tools.
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Fully charged should be around 20-21 volts. It sounds like you might have an unbalanced cell, which is pretty common with the 10s. If you can, open up the pack and check each cell individually; you might find one that’s underperforming.
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RuggedFalcon18: All DeWalt chargers are two-stage, but yeah, some of the newer ones do indicate when they switch stages.