Lithium battery troubleshooting and repair.

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Lithium battery troubleshooting and repair.

Lithium ion battery reuse with testing and repairing. This article can help those with Lithiumitis, the dreaded weak battery illness that will affect all of us in time. Lithium battery technology is great, but expensive, hard to repair and limited life if abused. I have used SLA for years with WE kits and they are great but heavy, limited life and capacity drops off steadily even when charged religiously.
I have been taking used lithium batteries and reject factory batteries and repairing them and using them for over two years on two bikes. The problems are:
1. Cells die and are hard to troubleshoot without schematics and no one sells “individual cells”
2. Internal Control circuits are different (builder to builder) and often potted or sealed over to thwart repair or modification.
3. There are no schematic diagrams to scope out and shops to fix batteries are not available.
4. They are expensive to replace and often good cells still live in the shell of the battery.
The basic problem is you may have one or two cells that keep the battery from working. The circuits inside the battery sense the low voltage on the bad cells and shut off the output! What took you 8 to 10 miles, now does 2 and shuts down. You can get more distance by shorting the output FETs. Solder the drain and source pins of the three pin drivers that are attached to the heat sink. This keeps the control circuit from cutting off output. But that just lets you run down the bad cell to nothing and then forces all wattage though the dead cell.
Look up the number of the three pin FET and type in the number with Google and see the pin out. Short the D and S pins, not the gate. Scrape off the goo on the circuit board if present, some are silicon and that is easy. The epoxy type is bad news, often you damage the traces if you try to remove!
Better to weed out the bad cells. Basically I take two battery packs, sort out the good from bad cells and make a good pack from bad. Bring life from death, the Egyptians worshiped that, let’s do it.
I use a cable connected to a 110 volt heater with no fan. This imitates a load without having a bike, motor and controller on your bench. Cheep, simple and three levels of heat switch can imitate 10, 15 and 20 ohm load that allow us to test battery output under load. Under a load the voltages will drop, unloaded batteries can show lots of volts but may pass little current. You can use it to run the battery pack down and check each cell with a meter to see what one is the lowest voltage, that one is most likely the weak cell. Dead cells show no voltage or ½ of the other cells. Normal voltage is 4.1 for a 3.7 volt cell when full. The charger puts out just over 4 volts per cell to charge and shuts down completely when done, no trickle.
You can unsolder the old cell out and in with a good one. The true test of a battery is the capacity in amp hours. The typical battery is 10 amp hours and I find bad cells have 4 or less amp hours and are the main problem. Vencon and Cadex battery tester systems are the pro choice, often Battery plus stores have these testers and you can ask them to test cells. I don’t know what they charge but maybe you can work something out when they are slow.
If not then run the battery down, take out the lowest voltage cells under load and replace with others from another pack that had high voltage. Always take care to disconnect as many wires from the fuses and switches as you can before starting so to avoid the sparks and exciting times troubleshooting.
The worst are the packs that are sealed up with duct tape, hard to open and easy to damage the soft cells, they are cheap but avoid them. There are many cell types out there. Some battery and charger combinations have the load balancing in the charger and 14 or more pin military type connectors. Most have the balancing circuits in the battery housing. The majority have metal housings for each cell and are strong.
One big issue I found if there is any overcharging or over loading outputs the cells swell up and are hard to get back into the case. Often there is no room in the case for expansion and so the soft pack cells burst from the crush of pressure and they are messy when leaking, keep away from the liquids, wash hands often if you have a leak in your pack. Recycle them all at centers near you, the worst battery type are nickel metal batteries, avoid them like the plague (heavy, inefficient and toxic as three mile island.)
Always watch out for packs that can only provide wattage outputs for 250 to 350 watt motors, they will not supply the 600 watts for larger motors and you will need two in parallel for the current output. It is not just volts and amp hours but how much can they push out without overheating and swelling. The scooter batteries for motorcycles are higher output and can deliver more to the larger motors.
You can even recycle laptop batteries and three old cells from bike batteries to make 12 volt packs for lights. They are slightly lower than 12 volts for lights but that will still work.
Enjoy! Keith

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