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!!!!!