Latest update: 11/25/2019 Mean Well power supply found for V2 grid charger
This version of the grid charger really can't be built anymore because the LED drivers it used aren't sold now. Use this link V2 Grid charger article to go to the latest version of the charger.
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Enthusiasts on insightcentral.net/forums have devised a way to rebalance the battery cells by slowly charging the pack to 100%. Many of the 2000 to 2006 Insight IMA batteries can be brought back to life by giving them this low current charge for an extended period of time (24 to 35 hours). Typically 0.20 to 0.35 amp is used. The this low level charge allows all the cells of the battery to become fully charged without overheating the better cells of the pack which will reach full charge first. The battery will charge to ~174 volts.
Even new batteries ought to be grid charged once every 3 or 4 months after they are 6 to 9 months old. This keeps them balanced and will help them last longer. Think of it as maintence task to extend the life of your battery.
The charger that does this is called a "grid charger" because it derives it's input power from the normal home power grid (the wall sockets). The charger is basically what auto mechanics call a "trickle charger" because it charges at a very low rate. A normal 12 volt car battery charger can NOT be used on the IMA battery because the voltage and current is not correct for our purpose.
The grid charger also powers the normal Insight 12 volt battery cooling fan to insure that the IMA battery pack doesn't overheat due to the extended low level charge or discharge. There is also a fan inside the grid charger to cool its components.
Information about LED driver change
Read this, it is important; (4/4/2019)
You MUST use current limited power supplies for a grid charger at this time. Not constant current supplies. The difference is subtle but most constant current supplies when wired in series will not track properly. Unfortunately eBay Chinese sellers of LED power supplies have switched over to constant current supplies and the current limited supplies aren't listed on eBay anymore. If I find a current seller of a 45-90 volt supply I will post it here.
I have tested several different constant current pairs and typically the first supply that reaches it's maximum current (considering the load) will prevent the other supply from delivering 1/2 of the voltage to charge the battery due to a race problem when the supplies start up. This will cause one supply to operate above it's wattage rating. I will describe this further near the end of this section.
Note, even though the current limited LED drivers are not available anymore, the rest of the information in this article will help you understand what grid chargers are used for and with luck how you can build one.
The following are the results of two typical identical Chinese 60-90 volt, constant current 300 ma supplies that I recently tested.
Test 1: Test both supplies individually for consistency.
Supply #1: (Tested by itself)
No load voltage: 126 volts
Loaded with two 40 watt light bulbs in series: 89.9 volts @280 ma (after 10 minute warm up)
Supply #2: (Tested by itself)
No load voltage: 131 volts
Loaded with two 40 watt light bulbs in series: 88.5 volts @275 ma (after 10 minute warm up)
Test 2: With both supply's outputs wired in series
No load voltage: 261 volts (NOT 180 volts as you would expect from two 60-90 volt supplies in series.)
This is actually normal for a constant current supplies. The no load output voltage has to be higher than the expected loaded voltage to deliver the maximum specified constant current to the load.
A limited current supply has a maximum voltage it can deliver (for instance 60-90 volts) and will if necessary, also limit the current so as to not exceed it's rated maximum output current. That is the subtle difference between the two types of supplies. The lower rating (60 in this case) is the lower limit for normal operation.
Test #3: Check individual load voltage of the two supplies connected in series.
Load with two 40 watt light bulbs connected in series to simulate charging current: 120 volts @ 239 (that sounds reasonable)
Output voltage of each series connected supply: (Wait till you see the next test readings @ 239 ma!!)
Supply #1: 4 volts (Yes, FOUR volts!)
Supply #2: 116 volts
Obviously these two typical non-precision constant current supplies are just not going to work for our grid charger since each supply is rated as a 25 watt supply. One supply is overloaded and doing most of the work and the other one basically took the day off.
Here's what caused one supply to only output 4 volts. When the AC power switch is set to ON there is a voltage/current race problem between the two supplies wired in series until one of them reaches it's constant current condition.
Since the supplies are wired in series, power supply #2 with the lower constant current capability with that load will have also reached it's maximum capable voltage at that maximum current. Supply #1 then fills in the remaining voltage (only 4 volts in this test) because of the current supply #2 is already forcing through both supplies. The higher current capable supply #1 can't force more current through the series connected supplies to balance the voltages because supply #2 won't allow any more current to flow.
Current limited supplies don't have the race problem because they each put out the their maximum voltage listed (90 volts) and if necessary limit the current to their maximum specified current. Yes the lower max current supply rules but only after it reaches it's specified voltage. Since the lower current sets the current the other supply is able to also output 90 volts for a total of 180V.
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Purpose of this article
This article is an idea provoking one to present how my DIY grid charger looks and to present the schematic with a parts list so you can build one for yourself. I am not going to give a detailed mechanical dimensions of where to drill holes etc because the parts you buy, the case you use, the individual parts, power supplies etc may vary in size from the parts I used. And truthfully I don't want to encourage people to copy my design to sell [6/11/13].
Ready to use grid chargers from simple to very elaborate computer controlled models can be bought through insightcentral.net/forums/ and eBay. This article describes a simple grid charger (no fancy computer control) that can be built from components found on eBay etc. If you are familiar with reading schematics, soldering and using simple hand tools you should have no problem building your own charger. You also have to open the battery box (IPU) behind the Insight seats to install a charging harness. You can find information how to install the harness (some with videos) at the Insight Central forums.
When I built this charger in February 2013 the main electrical components cost me less than $30 not including the used computer power supply case with it's fan, the switches and other mechanical parts. Naturally your cost will vary depending upon how many parts you already have. I had most of the parts. The parts price now is typically less than $70. You can usually find a local computer repair store to buy a junked ATX power supply for the case, fan and the AC connector etc. With luck you may also find many other parts on the printed circuit board(s) to use in your DIY charger/discharger.
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Features of this charger
The case I used for the supply is an old ATX computer case with the fan and AC power input connector retained. Try to use a case with a top mounted (larger) fan.
The original power supply printed circuit board(s) and wiring were removed and discarded. The original printed circuit board threaded mounting spacers (PEMs) in the case are used on my first grid charger. Luckily I found a nice case in my used parts collection that had ventilation slots on the top and one side. This allows me to position the charger on various sides and still have enough air flow. You might be able to use some of the components from the power supply PCB.
The unusual features of this simple charger are that two LED meters are used and it has a connector to plug your discharge load into. The discharge connector allows you to use the built in metering to monitor the discharge voltage or current. I won't use the 12 volt meter for any other grid chargers I might build. (The voltage always stays the same.)
One of the meters displays the 12 volt supply output voltage and the other meter is a dual function meter that has a front mounted push button that allows the meter to now read either 0-199.9 volts or 0-500 ma. The multimeter micro processor is set up to use an external shunt that originally allowed the meter to display 0 to 50.0 amp. I use a different value shunt which allows the meter to display a reading of 0 to 500 ma. Unfortunately the decimal point is preset and will be in the wrong position when reading current. The meter will be displaying 0 to 50.0 which is really 0 to 500 ma (normally we charge at 350 or less which will display as 35.0). Otherwise the meter works fine.
The multimeter is very handy to monitor the IMA battery system while charging or discharging it. The multimeter requires a separate small power supply with an isolated output voltage between 6 to 15 volts at less than 50 ma to power it. I used a small 6.25 volt cell phone charger supply but that is not a common voltage so I listed a 12 volt wall wart instead at the end of this page. I have built another charger and I was able to modify a 5 volt cell phone charger to output 7 volts with it still regulated. The supply must have the output isolated from the AC input. This is necessary because the DC negative lead of the small power supply is connected to the negative lead of the high voltage being measured by the meter. Switch mode power supplies have the output leads isolated from the AC input wiring. The common 5 volt cell phone chargers are not rated to power the multimeter without modification.
The IMA battery charging voltage is created by two "LED driver" current limited supplies wired in series. Each supply I used is rated to deliver 45 to 90 volts and are rated for 300 ma output current. The grid charger will output 178 to 181 volts no load and ~255 ma when charging the battery. These supplies are normally used to power strings of LEDs for lighting or special affects. The supplies I used are protected for short circuit, over temperature and limit the maximum output to 300 ma. The cases of the supplies are aluminum and will dissipate heat much better than plastic cases. By mounting them to the bottom of the metal case of the power supply more heat can be dissipated.
[4/11/2019 Update] Since the current limited LED drivers aren't listed on eBay anymore I have been investigating how to adapt the constant current LED power supplies for a grid charger. It is slow work because it takes a month or more to receive power supplies from China to test. I hopefully have configured a safe method of modifying the constant current supplies now listed on eBay to act as a limited current pair for the grid charger.
I am waiting for another set of isolated power supplies to hopefully confirm what will become an updated V2 of my DIY grid charger/discharger. The good news is that a dual 4 digit V/A meter and LED supplies are much cheaper than the equivalent components listed in the V1 bill of materials.
A good feature of the LED supplies I used is that they have an internal diode connected across the output leads so that when two supplies are used in series as a grid charger they will be protected if one of them quits working (as an example, from overheating). The charger won't output any charge current but at least it won't let the magic smoke get out of either of the supplies. In use I have found the charger supplies run at whatever the ambient temperature is. The supplies do not feel abnormally warm to the touch after charging for many hours.
I also use a series output diode within the grid charger to keep the IMA voltage from being present on the supplies when they are not operating. This allows the charger multimeter to display the IMA battery voltage when the supply is connected to the car but not charging. This also allows you to read the voltage and discharge current while discharging the battery.
The 12 volt, 2 amp rated switching supply I bought seems to be a typical Chinese supply in that it really doesn't put out 12 volts AND 2 amps at the same time. 12 volts is output with a 1 amp load. At two amps load the voltage drops to 11.1 volts. On the other hand, even 11.1 volts at 2 amps should drive the grid charger case fan, the Insight 12 volt Insight battery cooling fan and the BCM if you want to run it while charging the battery. I set the no load voltage to be 13 volts with the built in calibration potentiometer.
Construction and description of how to build a grid charger
To see an enlarged view of these pictures, left click on a picture or right click and select "View Image".