Headway Cell at 1.000 Volts

[jdbauman]

I was wondering if there is any way to bring a Headway 10Ah cell back to life if it is registering 1.00 volts. Any help would be appreciated...

I was also wondering if the Turnigy (Lipo) packs require a separate BMS when discharging. Thanks!

Jer

 

[Icewrench]

I had an abused Headway cell at 1.1 volt.
Tried to bring it back with a cell phone charger.
No dice.
It is a gonner.
Adios

 

[liveforphysics]

Parts inside the cell have had a permanate chemical reaction occur that will not be reversed from charging attempts. Sadly, it is now a paperweight.

 

[olaf-lampe]

I was also wondering if the Turnigy (Lipo) packs require a separate BMS when discharging. Thanks!

Jer

Usually the RC-ESC have a low voltage cutoff. It's an essential thing.
-Olaf

 

[liveforphysics]

Inside every LiPo pack, there are only cells wired up. I've never used any BMS or LVC, but this means you need to keep a careful eye on pack voltage.

Gary made some really damn slick boards that take all the work out of connecting balance taps and balancing, and provide an LVC/HVC setup all in a slick little package that the packs just plug into.

 

[ZapPat]

Parts inside the cell have had a permanate chemical reaction occur that will not be reversed from charging attempts. Sadly, it is now a paperweight.

This is what I've heard too, Luke, but after having this happen to one small "rhino" brand lipo I decided to try using it anyways. What I did was connect it to another pack with good lipo cells of higher capacity, but through some *very* current limiting resistors (connected cell to cell, not pack to pack). I made sure the initial charge current per cell was something like C/100 or less, and adjusted the resistor value a couple times as the over-discharged cells gained voltage and the charge current dropped too much. After a couple days of this they now had normal voltage levels. I then used a lipo charger with a *very* low C-rate charge to top up the cells. I then discharge with a very low C rate, then charge up a little faster, discharge a little faster, etc. Anyways, this 2 cell lipo pack has been in use in one multi-meter for a couple months now without any problems so far - but this is a very low C-rate application.

Now I've managed to discharge one of my 3p12s (45V nominal) zippy lipo packs down to 7V about two weeks ago! I stupidly connected the controller's logic power wire *before* my main power switch, so it sat there slowly eating away the pack's charge over a few days. I am now in the process of trying to rejuvenate them slowly, and only two cells of the 36 showed a lower voltage after the initial slow charge - these two cells will be removed from the two packs. Four of the packs charged up almost completely balanced after the first slow charge, and now after a few cycles they still seem to be showing no immediate problems. I have not discharged over C/5 yet though, so we shall see what happens in the long run after more charge/discharge cycles. The four packs are kept compressed BTW...

 

[scoot]

Does anyone have a good idea what the "point of no return voltage" might be for these 10ah Headway cells. I had a runaway discharge the other day when my laptop seized up during a low current discharge test, hence the LVC was ignored . My cells drained down to about 1.9 v per cell before i caught it and it freaked me out . I think they are OK though. They seemed to accept a full 10ah charge well enough .

 

[dak664]

Well, here are some links regarding overdischarge:
http://www3.interscience.wiley.com/journal/121418822/abstract
http://www.electrochem.org/meetings/scheduler/abstracts/210/0306.pdf
http://www.batteryuniversity.com/partone-12.htm
Apart from the gas evolution and the interface boundary layer being depleted and having to reform, the copper foil anode is oxidized and replated on the next charge. It seems the degradation proceeds over several days, so a short period at 1 volt might not cause too much loss of capacity. Prospects are not so good at half a volt.

 

[Icewrench]

The abused pack i was looking at had 6 low cells, 3 banks, below 2.5 volts maybe 2.1- 2.3 ? I did not record their voltages. The 1.1 cell was set aside and the other 5 were paralled and a charger connected. These had been low for a while at least 2 weeks maybe longer. 3 of the low cells came up to 3.3 or so 2 of the 5 did not respond to charging and may have gone lower. More paper weights

 

[ahambone]

Of the 125 headway 38120S cells I ordered through Frodus there was one cell that arrived at 1.77 volts. This was enough to scare me and so I labeled the cell with a big mailing-label that said "arrived 1.77, weak". I threw it on a VoltPhreaks charger and have charged it up slowly and have used it in a couple of low-load test packs. It appears to be fine - and holds a surface charge at something like 3.43 to 3.45 volts. My guess is this cell is fine but it's not worth the risk of putting it in my traction pack.

I guess this means that somewhere between 0.5v and 1.75 volts is where the "bad things" happen. I assume these are the voltages where the dendrites form across the cell and start shorting things out?

Cheers,
--Adam

 

[patrickza]

Not sure about the headways, but I have a bunch of konions that I've brought back from 0v... they run my headlight just perfectly and will hold 4.1v+ for weeks. Those really are fantastic cells...

 

[jdbauman]

I just received my charger from Voltphreaks. I attached one of my Headway batteries that was reading .631 volts. At first when I plugged it in, the read light on the charger was flashing. After about 1/2 hour it turned to a solid red light. It took about 6 hours, but the light on the charger finally turned green. When I took the battery off the charger, it was reading 3.67 volts.... YEA!!!!

My question is, do you think this battery has been salvaged and will work okay, or is it likely to not hold a charge very well from now on since the voltage got so low?

Thanks for all your help on this thread BTW!!!!

Jer

 

[Lessss]

Only way to know is to put it under load.