Where Do You Place the Meter Leads When Taking a Voltage Reading on the Charge Grid?

Beginning off you might inquire, "Why even discharge the IMA battery?"  Expert question.

In utilise the individual cells of the IMA bombardment will tend to deteriorate over time and the cells will accept different levels of watt hour capacity. This is called an "unbalanced battery".  When driving the car, the weaker cells limit the time and amount of assist the bombardment pack tin deliver.  The batteries tin usually exist brought back to good capacity by properly grid charging them.  This is chosen "balancing the bombardment" or "a balancing charge".  New batteries ought to be grid charged three or 4 times a year after the beginning half-dozen months to a twelvemonth of use. This helps to keep the battery pack balanced over time.  A weak bombardment should be beginning charged to balance them as much equally possible, then discharge the bombardment, and then accuse again.  Really weak batteries respond better to doing the charge/discharge sequence several times in a row.

The purpose of discharging the battery is to discharge all the cells downwardly to what is considered the discharged status.Private Ni-MH battery cells are considered discharged when they read 0.ix volt per cell.  Of course we tin't read each jail cell of the pack while the cells are installed in the car so we have to fudge the discharge a little hither.

Unfortunately when discharging an unbalanced battery pack the weak cells volition belch to 0.9 volts much quicker than the skillful cells.  In fact really weak cells can not only belch to 0 volts but they tin exist slightly "reversed" charged by the belch electric current while the good cells in the pack continue being discharged.  At loftier current levels, opposite charging cells is non good!  Using too high a belch electric current with cells reversed charged can event in those cells overheating with venting which will cause all sorts of issues over fourth dimension.

Through experimentation, the general consensus on the Insight Central  forum is that if the cells are reversed charged at a depression current, that minimum or no damage will occur.  What that low current  is, is still upwards for some debate.  But 200 ma or less range at the finish of the discharge should be OK.  And if your battery is on information technology'southward last legs anyhow it may be worth to practise this process on the take a chance yous volition get more life out of information technology. Several people have discharged weak IMA battery packs to zero volts and had very proficient results even subsequently the first grid accuse to 100%.  Two charge, belch, accuse cycles are improve.

As the say in the TV advertisements, "Only outset .........."
If you take installed ane or two diodes in the high voltage charging harness you will Non be able to discharge the bombardment. So if you want or later need to discharge the battery remove any diodes in the HV lead(due south) of the charging harness.

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OK, here's how you really make the discharge load.

The actual discharger I shortly  apply consists of two ceramic light sockets mounted on a curt piece of ane" x 6" board.  Ane socket has a pull chain ON/OFF switch on information technology. The actual belch load can be made by using 120 volt light bulbs of various wattage combinations wired in serial. Zero exotic nigh that, but wire the two sockets in series like Christmas tree lights with a single length of wire and attach the 2 wire discharge cable to the unmarried complimentary terminal on each socket.  I used a long 120 volt power cord from a vacuum cleaner every bit the belch cable so I can take the light bulbs within my garage to proceed an center on the discharge while information technology is running.

The current drain when using calorie-free bulbs volition vary depending upon the battery voltage.  With 2 serial connected 60 watt bulbs and the battery at 162 volts the discharge volition start at ~265 ma. When the bombardment is down to 115 volts the discharge will exist ~240 ma.  If you want a lower belch rate vary the wattage of the 2 bulbs as the current changes depending upwardly on what final current yous want to discharge at.  Lower wattage bulbs give lower belch currents.

I would recommend the belch to be below 200 ma near the end of the discharge if possible.  But once again these numbers are still beingness discussed and tests on the Insight Central forum are still being done equally you read this.

I did some demote tests on diverse wattage incandescent lite bulbs to help sympathise the current vs voltage. I also checked the current menstruum using a 500 ohm, 100 watt resistor for comparison. The information is presented on the chart below. Use this nautical chart as a guide to what wattage bulbs to apply depending upon what current yous desire to discharge the bombardment at.

While using a resistor as a belch load will piece of work; you lot do have to take into consideration that the resistor will be dissipating up to 60 watts when starting the discharge with a fully charged pack.  Even mounting my aluminum cased 100 watt resistor on a three" 10 v" finned heat sink did not keep it cool enough so it wouldn't cook your finger if you touched it.  A figurer fan did not assistance much.  Every bit a test I finally used a microprocessor dual heat pipe heat sink with a big shrouded fan to be able to keep my fingers on the resistor for a short while.

Again, I recommend using two old fashioned light bulbs.  We know they are going to exist hot and generally don't put our fingers on them.  And they do give some indication of how the discharge is going along.

Click on the chart to see it full size.

One thing to find is that the electric current vs voltage for an actual IMA discharge does not exactly correspond to the demote measured currents using the same bulbs by ~iii%.  I rechecked the calibration of my grid charger at room temperature and the voltage and current readings are correct using the aforementioned DVMs used for the bench measured information and the grid charger calibration.

Other people have also noticed that the electric current limited LED commuter supplies do non always run in current limiting when charging the IMA battery. When driving a resistive load my supplies current limit at ~300 ma when the voltage is above 145 volts DC. In utilise the grid charger maximum output is ~255 ma.

 Only they do the job so we use them.

I would take the nautical chart currents to exist a close approximation of what the discharge currents will be equally a belch load.  With the current meter built into the grid charger you tin can check the actual discharge current and peradventure use different size bulbs in various combination to get the electric current you desire at the beginning or end of the discharge.

One-time fashioned incandescent calorie-free bulbs are getting difficult to find and CFL bulbs will Non work.  Halogen overflowing lights piece of work fine and take the aforementioned curved discharge current vs voltage as the normal old fashioned bulbs.

Before I could wire the ceramic bulb sockets I had to route out an surface area on the board underneath where the sockets would mountain with a ~ane/2" wide trench between the sockets for the wires to get between the sockets.  There is another short trench from one socket for the two wire discharge cable to leave the board.  I used a matching 2 pin male connector on the terminate of the cable to plug into a 2 pin female connector on the grid charger.

The picture on the left shows the routed out area underneath where the sockets mountain.  The right side picture shows the sockets mounted on the board.

I used a long ii wire string from a vacuum cleaner (with the plug changed) so I could have the discharger sitting in my closed garage to have an thought how the discharge is going.  Information technology would be possible to also accept provision on the board to mount a voltmeter to go on track of the discharge.  I didn't practise that because I use my gird charger multimeter to read the current and voltage and run the cooling fans.

Some people use dual bulb "Y" sockets designed for wall mounting.  They have two wires on each socket that tin can exist wired in series.  You lot don't accept to route the lath with a "Y" socket. The problem with the "Y" socket is that there is no switch on the ones I've seen.  I like the remote cutting off feature of having a switch on one of the sockets.

While the battery is being charged or discharged the batteries get warm so you MUST run the bombardment pack cooling fan at the aforementioned fourth dimension.

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