Ford — Battery Capacity Test
Testing & diagnosis
From a Ford service manual — check it applies to your exact model before use.
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Before you start
- Battery gas mixture can explode if flames or sparks are near vent openings
- Sulphuric acid can cause serious burns
- Always disconnect the battery ground cable when charging
Procedure
- Turn the control knob on the Battery-Starter Tester to the OFF position.
- Turn the voltmeter selector switch to the 20-volt position.
- Connect both positive test leads to the positive post and both negative leads to the negative post.
- Turn the load control clockwise until the ammeter reads three times the ampere-hour rating of the battery.
- With the required load for 15 seconds, note the voltmeter reading.
- If the reading is 9.6 volts or more the battery has good capacity; check specific gravity.
- If below 9.6 volts, check each cell specific gravity and charge or replace per the charge schedule.
Tools required
- Rotunda Battery-Starter Tester ARE 16-31 Amazon
- Voltmeter Amazon
- Rotunda Cell Analyzer (SRECA-200) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltmeter 9.6 volts or more = good
- Specific gravity 1.230 or below = charge
- More than 50 points (0.050) between cells = replace
Source: Ford service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.