Anyone know if it’s possible to “fix” dead Tenergy Li-on packs? I have two that are unused yet won’t take a charge.
BD
Li-ons for all their many advantages have a distinctive Achilles heel. It is a quirk of their design that they have a minimum voltage requirement to stay alive. If the charge voltage falls below that amount they are forever dead. The circuit that protects them from internal shorts is supposed to protect them from falling below the minimum voltage. This is why LI-ons stop dead at a certain point rather then gradually run down like Ni-cads or Lead acid batteries. They are actually being turned off to protect the pack. It does not always work.
I am not aware of any recourse for this but you could contact Tenergy’s customer service and see if they have a fix.
I strongly advise against attempting any home remedies. We have had the discussion about burning down the house on several threads already. If you choose to go that route please make sure you get video you know how we all love a good BBQ.
Bob, can you check the voltage of the packs and tell me what it is, or are you reading zero volts?
Both read zero. 
Bob
Check the voltage on each cell. You can use a pin or something to probe through the insulation.
The last Tenergy pack I had go to 0 volts turned out to be the PCB. The individual cells measured 3.7v or something close.
I don’t know if you can disconnect the cells and reconnect them to restart the PCB. If not, the PCBs are not too expensive.
Tom
No, don’t do that.
You can check the voltage of each cell and if all the cells are within .03 volts of one another, than we can bring it up to nominal voltage to be charged. If your not reading any volts from any of the cells, then it’s a dead pack. If your reading voltage from each cell but not the PCB, we can reset the PCB, that’s not a problem.
Let me know what you find.
Rick
How do I reset the PCB?
Tom
I would rather you send us the pack so we can test the cells and then see if the PCB needs to be reset. If you touch the wrong leads, you could pop an FET and then the PCB would not function and we would be liable.
I guess that answers that. The cell voltages measure fine.
I will try removing the connections to the board. I may temporarily tie all the terminals together on the PCB.
Just a shot in the dark. I will hook it up again and see if it works. If it doesn’t work, I will buy a new PCB and hook it up.
A new PCB is much cheaper than half the postage for sending the pack on round trip to Iowa. If I stumble on the correct
way to do it, I will post it.
Thanks for all your help Rick.
Tom, if you have any problems…stop and give me a call.
Rick, what do you charge to test the cells and then see if the PCB needs reset?
Did the OP (Bob) ever test the voltages on the individual cells?
Most protections circuits can be reset by forcing a charge on the cell, bypassing the protection circuit.
I know Rick won’t like hearing this, but I fix most stuff myself.
Clearly you need to not overcharge the cell, overvoltage, overcurrent, etc. etc. your mileage may vary, no cute animals were harmed…
Greg
Greg, and don’t all the cells have to be within a certain voltage of each other too?
David Maynard said:
Greg, and don’t all the cells have to be within a certain voltage of each other too?
Yes - They need to be close. I don’t know the maximum acceptable variation, but my packs will balance all cells to within .02V Most LiIon packs don’t have a built-in balancing plug, but you can balance them if you carefully slice into the insulation to expose the individual cell connections and tap in there. Any new packs I build will include a balancing connector.
There is a procedure to “reset” a PCB that has shut down. I have it written down and it’s risky if you don’t know exactly what each terminal on the PCB is, so I won’t share it here.
I don’t know if I will invest in any more Tenergy packs. I’ve lost quite a few of them due to under-use. The Tenergy cells that I have installed in locos have been doing great, but they get cycled much more often.
I’d suggest “under-use” (nice terminology, John) is unlikely an issue. These cells have a life cycle that begins as soon as the cells are manufactured and or the chemicals are combined. That said, there are common issues herein with regard to care and use which can and does effect the cell/batteries life. The most common failure mode is likely associated with regard to DOD (depth of discharge) and SOC (state of charge) of battery at time of and or while being stored. There is also concern for properly sizing the battery to carry the load and or current demands and heat is the ENEMY!
Cell balancing is and will always garner the best results with regard to cell/battery maintenance. The benefits of individually evaluating and charging/discharging cells to balance the voltage of each cell in a grouped environment (battery) is the recognized standard in todays battery world…
I’ve suggested many-many-many times herein that running Lithium-Ion cells down to such time that PCB turns them off and or below 60% of the batteries respective rated capacity severely effects the cell/batteries life cycle!
Michael
Michael Glavin said:
I’ve suggested many-many-many times herein that running Lithium-Ion cells down to such time that PCB turns them off and or below 60% of the batteries respective rated capacity severely effects the cell/batteries life cycle!Michael
Yes you have, and I now practice frequent charging religiously. When my problem packs were new I didn’t know any better and would always run them down to cut-off. Perhaps that is the real reason so many have gone south.
So how does one manage this, keep a stop watch running based on previous run times before shut down. When doing ops I often lose track of time and don’t realize until the locomotive stops.
Gary - If you charge before every session do you have enough run-time to complete on one charge? If so, just charge before (or after) every session. I prefer after so loco is ready to go whenever the mood strikes.
It’s not a perfect system, but it eliminates most of the auto cut-off situations.
I can usually tell when my batteries are a few minutes from cut-off; sound volume decreases and loco runs a little slower. Unfortunately by the time this happens I don’t have enough left to get back to the shop.
Gary, you can do what I do and just not care.
I use safe(ish) charging practices but other than that I run the crap outta my trains. Sometimes I charge them when I’m done sometimes during and sometimes before. Sometimes I run them dead and other times I don’t. I don’t keep track. My oldest battery finally quit after six years. I’ve had to replace one other that didn’t want to cooperate. I use the (kinda)smart chargers, I plug them in and walk away.
I run with scissors too.
T
Hi Gary, I have a simple/painless way to monitor your battery level. Use one of my LED battery status meters. After each session I take a reading and can predict how much longer will be the runtime. In the loco shown is a 18.5v lithium. This battery will charge up to 20.5v so I still have a another hour of runtime. I need to know what size plug to attach. Please contact me for more details at [email protected]
Don Sweet
