Makita Radio #1 Cause of Battery Failure

#1 Cause of Battery Failure!

As discussed in my other post on battery maintenance the voltage of the battery packs must be kept in a reasonable range (greater than 15 volts).  Most of the tools have a voltage cut out (MPS -Makita Protection System) or just stop working below 16-17 volts and are then put onto the chargers.

After testing the voltage of "flat" batteries from the local tradesman the following results were discovered:

• Drills & Rattlers stopped working efficiently at around 17 volts with the lowest recorded at 16.2 volts
• Circular Saw, Grinder and the Hammer Drill were cut off by the MPS at 16.5 volts approx
• Nibblers and Vacuum  all ran the batteries slightly lower but ok at 16 volts
• Torch lost brightness at 17 volts but continued to work as low as 16 volts but very dull
• Radio when deemed flat by the radio the voltage was a staggering 10.5 volts!

So why was this the case?  Well upon opening the radio up i found the reason.  The radio accepts all the battery types from 12 -18v.  So where the battery connects there was a simple voltage regulator which converts the battery input value to 12 volts by simply burning the voltage above 12 off as heat (typical regulator).  However the radio has no way of shutting down each individual battery types when it is flat!  So the radio continues to run what ever battery is connected down to the preset cut off of 10.5 volts!  This would cause damage to the cells and over time would contribute to the failure of the BL 1830 and Bl 1815's

Solution

Solution #1 -  This is the solution I have been telling people to do.  The radio can go for a couple days on a charger 1830 so my advice is to change the battery every morning as you start work.  With this method the batteries only drop to about 16 volts (typical 8 hour day). 

Solution #2 - If you are only a moderate user of the tools such as a handyman or at home the option is to change the battery every time you flatten one on the tool that you are using to keep reminding you.  By changing the battery early will not reduce the battery life, in fact improve it!

Solution #3 - If you have any of the older type NICD or NIMH batteries laying about use these in the radio!  They love being totally discharged any will save any of you 18v LXT batteries from doing any damage.

Solution #4 - ADVANCED - Installing and under voltage switch inline with the 18v contacts will ensure that the battery is not drained too low.  An example of such circuit can be built using a similar schematic to the one i have designed. It can be viewed at  https://www.circuitlab.com/circuit/dk4vzq/makita-undervoltage/ I still have not finished the circuit but feel free to use this design

Conclusion

Make sure your radio does not flatten and therefor damage your LXT batteries!!!!!

Battery Maintenance

So I along with many others have been spending time working on the battery failures in the Makita 18v LXT range.  If you check out my other posts including;

http://makita18vmod.blogspot.com.au/   - Which is the repair and modification of the failed batteries

http://makitaradiomod.blogspot.com.au/ - Creating a Bluetooth Makita Radio

The Causes of Battery Failure (lithium Ion Type)

Every person you speak to has a different method or view on battery life and how to manage your batteries. Unfortunately most of these methods are for the older types of batteries (NiCd, NiHh or the standard lead acid car battery).  Some of these methods include flattening the battery before recharging and leaving them flat if you are not using them..

 These methods are FALSE!

Q: Am I giving the battery a memory by not fully discharging them?

A: Lithium batteries do not have memories and by fully discharging the batteries actually damages the cell packs. The packs consist of 5 x 18650 type 3.7 volt cells and they should preferably be discharged no lower than 15v (3 volts per cell) at worst case scenario. 

Q: Should I store my batteries flat or charged?

Lithium batteries have much lower self discharge capabilities than the older style batteries.  Self discharge is the loss of energy over time whilst now being used.  To keep the Lithium cells happy always if possible store them fully charged to avoid the cells dropping too low.

Q: Can I put a Battery that is only half flat onto a charger?

Yes! any chance you get to keep these batteries fully charged the better!  One cycle of a battery is defined as one complete discharge cycle so if you only half discharge a battery and charge it again it is not counted as one cycle but as a half.  so the next time you discharge it by a half its classed as one cycle.

 Other Factors

Temperature is another factor that affect Lithium Ion cell packs and by temperature i mean rapid discharge and charge causing internal heat not ambient temperature.  Most of the tools and the the chargers have methods to avoid this but avoid short circuiting the battery when using it in other non standard equipment.