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Drill battery fettling/improvements

More-idiot-proof drill-battery charging, and upgrading poorly drill packs

Wookey has built proof-of-concept idiot-proof 1hr charger out of makita charger case and B4 35W autocharger They are £9 each. Donor charger bodies off ebay are about £10-13.

B6 50W charger (£11) would charge faster, but is discontinued.


  • Test drill batts from 2017. Done (3 need new cells)
  • Build 2 or 3 balancing autochargers. Cannot source female batt connector, so must buy dead makita chargers (about £10 each). 2 more base bodies bought (May 10th) so we have 3 now. Construction has started. 2nd and 3rd B4s have arrived (15th June). 1st charger built and working. 2 more built. One has only 1 LED. One has one poorly LED. Chargers seem sensitive to reboxing - not clear exactly what's going on.
  • Replace PCBs in 7 ('non-makita-charger') packs with own balance-connector board (about 3 hours per batt!): Done (June 30)
  • Rebuild 3 packs with new cells. Needs proper tab-welder (Tried soldering last year, and DIY tab-welding - not reliable enough). Sponsored Samsung 25R cells from arrived July 7th. Done (July 2)
  • Have bought/acquired parts for battery-tab spot welder (1kW transformer, controller, electrodes). Built, and works (well)!
  • The 2 new packs could get balance-connector board. (optional - will leave for this year so 5 packs still work on Makita Charger)


Existing packs mostly use Sony SEUS18650V cells (nominally 1500mAh, 10A) 4Ah pack uses LG DAHD21865 (nominally 2000mAh 25A)

Batt drilling current tested at 26A, so 15A cells needed. UK supplier is Can now get 2 and 2.5Ah 15A cells, so should be able to build 4 or 5Ah capacity packs for ~£40. Nickel tab-strip bought.

Possible 18650 choices:

Seems like 25R are excellent value and 30Q are best high-end cells (cheaper than VTC6 for same performance) have sponsored us 3 packs-worth of Samsung 25R. Yay! (free due to having + and - labelled on wrong ends.

Last update 2018.07.04