Sorry for delay; Windows latest updates somehow crashed my compter, but am now back on line and here are the mods requested.
To dissemble the unit it is only necessary to split the case (2 screws) and unsolder the pushbutton connections on the PCB. You MUST use either a desoldering tool or desoldering braid to remove the solder and avoid stripping copper from the PCB. The whole assembly will now unplug from the display and come away attached to a side panel.
The older unit with the switch can also be modified. Dissembly is similar but you must remove the switch clamp nut.
ESR Meter Mods. Details for single cell operation and measuring small cells
Single Cell Mod
This is intended to enable the meter to measure single cells. It has no effect on normal use.
The electronics within the meter require >6V to drive it which normally comes from the lipo under test but needs to be fed from an external source to measure single cells. The simple mod is to add a lead (I normally use a JST connector so that the external feed can be a small 2S or 3S lipo) which feeds the circuitry via a 1A schottky diode for reverse voltage protection. The current demand is 20mA.
The photo below shows how to connect this; the +ve via the diode to the cathode of D1 and the –ve to 0V rail. You need to feed the leads through the grommet in the side panel as shown.
For measurements it is better to connect the voltage search leads in parallel with power leads to measure small cells. Connect them directly to the cell if possible with large cells ie on the cell side of the power connector.
After use don’t forget to unplug the auxiliary lipo otherwise it will eventually become overdischarged.
Low Current Mod
The normal measurement current of 16A is too large for very small cells (<300mAh) as the max Cell range is 30milliohms. It can be reduced to 1.6A with a simple mod described below and a small slide switch added to make the unit dual range.
The display is a compromise as the meter will now read one tenth of the actual ESR so that the reading must be multiplied by 10 on the 1.6A range
The two photos show the modification on the board and the overall layout. The slide switch can be mounted through the side panel.
R22 needs to be shunted by 19.3ohms to reduce the current to 1.6A. Connecting two 39ohm resistors in parallel will give 19.5ohms which is the easiest way to achieve this. Ideally use 1% tolerance resistors. (I know the two in the photos are 56ohms BTW!)
If measuring very small single cells for indoor flight (70 - 160mAh) you need to add both mods.
Take care with the very small connectors which are used as they will add to the ESR readings if not clean and/or properly mated.
This apart, all the real “C” ratings measurements and John Julian’s Lipotool (www.jj604.com/LiPoTool
) all still apply and work well with the results.
See his findings at http://www.rcgroups.com/forums/showp...75&postcount=5