FAQ
TL;DR: Makita 7000 packs use 6×1.2 V Ni‑Cd; typical Li‑ion conversions use 2×3.7 V in series. “This third pole is the output from the temperature sensor.” [Elektroda, bubu1769, post #16965886]
Why it matters: This FAQ helps DIYers safely convert Makita 7000 Ni‑Cd batteries to Li‑ion while keeping charger compatibility and over‑temperature protection.
Quick Facts
- The third terminal is a thermistor lead; some chargers won’t start without it. [Elektroda, bubu1769, post #16965886]
- Wire the thermistor between battery ground and the third contact. [Elektroda, Freddy, post #16971334]
- For Li‑ion, use a charger with a balancer; don’t rely on old Ni‑Cd chargers. [Elektroda, Freddy, post #16971376]
- High‑drain cells advised: INR18650‑25M referenced as the right class. [Elektroda, Freddy, post #16971394]
- Conversion example: replace 6×1.2 V Ni‑Cd with 2×3.7 V Li‑ion (2S). [Elektroda, norwidus66, post #16971712]
What is the “third pole” on the Makita 7000 battery?
It is the thermistor lead used by the charger to monitor pack temperature. Without this sensor connection, certain chargers refuse to start charging as a safety measure. Treat it as a temperature-sense terminal, not a power pin. [Elektroda, bubu1769, post #16965886]
How do I connect the thermistor when converting to Li‑ion with a BMS/PCM?
Keep the thermistor in-circuit and wire it between battery ground and the third contact, outside the cell-balancing path. This preserves temperature monitoring while the BMS manages voltage/current protection. As one expert put it: “Connect as it was—between ground and the additional contact.” [Elektroda, Freddy, post #16971334]
Can I keep using the original Makita Ni‑Cd charger after the Li‑ion conversion?
Use a Li‑ion charger with cell balancing. The original Ni‑Cd charger is not suitable for charging Li‑ion chemistry safely. A modern charger with a balancer ensures proper cutoff and equalization for the 2‑series pack. [Elektroda, Freddy, post #16971376]
Which cell configuration replaces the stock Makita 7000 pack?
The original pack is 6 cells × 1.2 V Ni‑Cd. A common Li‑ion retrofit uses 2 cells × 3.7 V in series (2S). This yields the required nominal voltage while reducing cell count and weight. Verify tool current demands before finalizing. [Elektroda, norwidus66, post #16971712]
What Li‑ion cells are recommended for a drill/driver conversion?
Choose high‑drain INR18650 cells; INR18650‑25M is specifically recommended. Low‑drain cells sag under load and shorten runtime. Matching high‑current capability helps the tool maintain torque and reduces stress on the BMS. [Elektroda, Freddy, post #16971394]
Is there a minimum current rating I should target for the cells?
Use cells capable of around 20 A discharge for robust performance in power tools. A user referenced 20 A Samsung cells as a good fit for this application, aligning with high‑drain requirements. [Elektroda, norwidus66, post #16971386]
What is a BMS/PCM, and do I need one?
A BMS/PCM protects Li‑ion packs from overcharge, over‑discharge, and short circuits, and may balance cells. Include it in the converted pack to prevent damage and safety risks. Route the thermistor separately to the third terminal. [Elektroda, norwidus66, post #16971352]
Will the charger work if I omit the thermistor connection?
No. Some chargers will not initiate charging without the thermistor signal. This is a safety interlock to avoid charging a pack without temperature feedback. Always restore the third terminal wiring. [Elektroda, bubu1769, post #16965886]
How do I physically wire a 2S Li‑ion pack for the Makita 7000?
Basic steps: 1) Build a 2S stack with appropriate nickel tabs. 2) Connect the BMS: B−/B1/B+ to cells, P−/P+ to tool. 3) Wire the thermistor between ground and the third contact. Confirm continuity and insulation before closing the case. [Elektroda, bubu1769, post #16971470]
Can I balance the cells inside the battery housing?
Yes. Install a balancer or a BMS with balancing inside the pack. This supports even cell voltages during charge and discharge, improving longevity and safety for your 2S setup. [Elektroda, norwidus66, post #16971386]
What is a thermistor and why is it in the pack?
A thermistor is a temperature‑dependent resistor used for thermal monitoring. The charger reads its value to detect over‑temperature and control charging. Keeping it connected ensures safe operation and prevents charge refusal. [Elektroda, Freddy, post #16965890]
What’s the failure mode if I pick the wrong cells?
Low‑drain cells cause voltage sag under load, weak torque, and early cutoffs. As noted, without the right INR18650‑25M‑class cells, performance drops quickly and pack life suffers. [Elektroda, Freddy, post #16971394]
Do I need to modify the tool terminals?
No terminal changes are required if you preserve the three contacts: positive, negative, and the thermistor lead. Ensure the BMS output goes to the main +/- while the thermistor remains on its own line. [Elektroda, bubu1769, post #16971470]
Any soldering tips for assembling the pack?
Use spot‑welded nickel strips when possible. If soldering, work quickly on tabs, not cell cans, to avoid heat damage. Verify insulation and strain relief before reassembly and test with the charger. [Elektroda, norwidus66, post #16971484]
Will I notice better runtime after converting to Li‑ion?
Yes, when using high‑drain 2500 mAh Li‑ion cells and proper balancing, users report multi‑year service and stronger performance compared to tired Ni‑Cd. Keep thermistor and use a Li‑ion charger for best results. [Elektroda, norwidus66, post #16971386]
What’s the quickest way to confirm my wiring before first charge?
Check that the charger starts only with the thermistor connected, and that pack voltage matches a 2S Li‑ion (about 7.4 V nominal). If it refuses to start, re‑verify the third terminal wiring. [Elektroda, bubu1769, post #16965886]
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