Mazda MX-5 Miata / Grand Touring. Manual - part 40

2. Remove the battery cover from its right side. 

Fig. 4: View Of Right Side Battery Cover 
Courtesy of MAZDA MOTORS CORP. 

BATTERY DUCT REMOVAL NOTE 

1. Remove the under cover.  

2. Remove the battery duct.  

NEGATIVE BATTERY CABLE INSTALLATION NOTE 

1. When connecting the negative battery cable to the battery, connect the negative battery cable and the 

ground cable as shown in Fig. 5 . 

 

2008 Mazda MX-5 Miata Grand Touring 

2008 ELECTRICAL Charging System - MX-5 Miata

  

Fig. 5: Connecting Negative Battery Cable 
Courtesy of MAZDA MOTORS CORP. 

BATTERY INSPECTION [LF] 

ELECTROLYTE SPECIFIC GRAVITY 

1. Measure the electrolyte specific gravity using a hydrometer. 



If it is less than the specification, recharge the battery. (See BATTERY RECHARGING [LF] .)  

Battery electrolyte specific gravity [20°C {68°F}] 1.22-1.29  

BATTERY VOLTAGE 

1. Inspect the battery as follows: 

WARNING:



Since battery acid is toxic, be careful when handling the battery.  



Since battery acid is highly corrosive, be careful not to allow it to 
contact clothing or the vehicle.  



In case battery acid contacts skin, eyes, or clothing, flush it 
immediately with running water. Especially if the acid gets in the 
eyes, flush with water for more than 15 min. and get prompt medical 
attention.  

 

2008 Mazda MX-5 Miata Grand Touring 

2008 ELECTRICAL Charging System - MX-5 Miata

  

BATTERY INSPECTION TABLE

Battery load test current  

46B24L (36): 135 A  

STANDARD SPECIFICATION 

BATTERY STANDARD SPECIFICATION 

BACK-UP CURRENT 

1. Verify that the ignition switch is off (key has been removed) and that all doors are closed.  

2. Remove the battery cover.  

3. Disconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [LF] .)  

4. Connect the tester between the negative battery terminal and negative battery cable, leave the battery 

undisturbed for 30 min. , and then measure the back-up current. 



If not within the specification, measure the back-up current while removing the fuses one by one 
from the inside of the main fuse block and the inside of the fuse block.  

Step

Inspection

Action

1 Measure the battery positive voltage.

12.4 V or 
more

Go to Step 3.

Less than 
12.4 V

Go to the 
next step.

2 Quick charge for 30 min. and recheck voltage.

12.4 V or 
more

Go to the 
next step.

Less than 
12.4 V

Replace the 
battery.

3

Using the battery load tester, apply load current (see Battery load test 
current) and record battery voltage after 15 s. Is voltage more than 
specification?

Yes

Normal

No

Replace the 
battery.

Battery temp. (°C {°F})

Minimum voltage (V)

4 {39}

9.3

10 (50}

9.4

16 (61}

9.5

21 {70}

9.6

NOTE:



If the battery is not left undisturbed for 30 min., the tester will indicate 
a high value (approx. 300 mA).  



If the key or any electrical accessory is operated within approx. 30 
min. after the tester is connected, the battery must be left 
undisturbed for approx. 30 min. from that point.  

 

2008 Mazda MX-5 Miata Grand Touring 

2008 ELECTRICAL Charging System - MX-5 Miata

  

Battery back-up current  

Vehicles with immobilizer system: 25-45 Ma  

Vehicles without immobilizer system: 30 mA or less  

5. Inspect and repair wiring harnesses and connectors of the fuse where the current has decreased.  

BATTERY RECHARGING [LF] 

1. Remove the battery and then place it in a pan of water.  

2. Connect a battery charger to the battery and adjust the charging current as follows. 

Battery slow charge current  

46B24L (36): 3.5-4.5 A  

Battery quick charge current [30 min.]  

46B24L (36): 25 A  

CAUTION:



Operating electrical loads while the back-up current is being 
measured can damage the tester.  

NOTE:



For vehicles with the immobilizer system, the system periodically 
shifts synchronization of the security light flashing. Therefore, 45 mA 
(0.1s) current is supplied when the security light is illuminated, and 
25 mA (2s) current is supplied when the security light is not 
illuminated. In addition, the measuring instrument, which shows the 
average value, indicates around 30 mA.  

WARNING:



Keep all flames away from the battery, otherwise evaporated gas 
from the battery fluid may catch fire, and cause serious injury.  



Remove the battery filler caps when recharging to prevent battery 
deformation or damage.  

CAUTION:



Do not quick charge for more than 30 min. It will damage the battery. 

 

2008 Mazda MX-5 Miata Grand Touring 

2008 ELECTRICAL Charging System - MX-5 Miata