Large Scale Central

Big, New, Dead LiIon battery pack

Problem Solving
#1

A Tenergy 14.8v 6.6 AH battery gives 0 output. I can put it on the charger and after a minute or so, the charger says it’s charged. Talked to the source, “sorry, out of warranty.” (Bought it Feb of last year).

So, I ripped it open. Found the negative end, the positive end, and each of the 3 taps. The whole pack reads 14.1v, but the output to the leads is 0v. 12 gray 18650 cells. You think it’s the protection board that’s dead? All the slobber joints look good. Don’t see any escaped goop.

What do you think? Take it out to Hollingsheds and let him shoot it with something large or order a new board?

#2

Nah, hit it with a torch and have a big fire…

yep, see if you can figure out if the protection board needs a reset or it is toast.

Greg

#3

There is a PCB reset procedure for the Tenergy batteries. I have it written down somewhere in a pile of papers in my shop. I’ll see if I can find it - or try Google.

#4

Buy my batteries and it will come with a year warranty.

#5

Got to charge them every 4 months, whether you use them or not.

#6

Jim Agnew said:
Got to charge them every 4 months, whether you use them or not.

Jim, are you saying a Tenergy 14.8v 6.6 AH battery will self discharge over a 4 month period?

#7

Hmm. Haven’t had any luck googling how to reset that and my laptop battery is about done. Perhaps my laptop battery needs its protection circuit reset too.

#8

Tony, I have over a dozen and they all drop a few volts over a 4 month time period. If they drop to around 12 volts, forget it.
AirWire and Batteryspace both recommend a 4 month charging cycle.

#9

I have one that stays charged, and one that discharges.

I check them about once a month.

Don

#10

Tom - When I google I get lots of different methods, non are the one I used which I think I got from a Tenergy data sheet on the PCB. I will look tonight.

#11

Thanks Jim.

Do other brands of Li-Ion cells also exhibit the self discharging characteristic?

I was led to believe that, unlike NiMh where self discharging is very common, this did not happen with Li-Ion.

My local Sanyo distributor will likely be able to provide an answer.

#12

Tony Walsham said:

Thanks Jim.

Do other brands of Li-Ion cells also exhibit the self discharging characteristic?

I was led to believe that, unlike NiMh where self discharging is very common, this did not happen with Li-Ion.

My local Sanyo distributor will likely be able to provide an answer.

That’s been my belief, too. Charge the battery, put the loco on the shelf for the winter, pull it off in the spring, and you are good to go with 80-85% charge.

#13

Tony Walsham said:

Thanks Jim.

Do other brands of Li-Ion cells also exhibit the self discharging characteristic?

I was led to believe that, unlike NiMh where self discharging is very common, this did not happen with Li-Ion.

My local Sanyo distributor will likely be able to provide an answer.

That’s been my belief, too. Charge the battery, put the loco on the shelf for the winter, pull it off in the spring, andied you are good to go with 80-85% charge.

#14

Steve Featherkile said:

Tony Walsham said:

Thanks Jim.

Do other brands of Li-Ion cells also exhibit the self discharging characteristic?

I was led to believe that, unlike NiMh where self discharging is very common, this did not happen with Li-Ion.

My local Sanyo distributor will likely be able to provide an answer.

That’s been my belief, too. Charge the battery, put the loco on the shelf for the winter, pull it off in the spring, andied you are good to go with 80-85% charge.

The new Lithium chemistry batteries (LiPo Graphene) I just bought came with a recommendation of “For best results, store batteries a approximately 1/2 charge of the capacity listed”.

They have a sticker on the box that says “Shipped at 30% charge return to storage charge ASAP”

The accompanying paperwork states that “Always verify voltage of batteries that have been out of service for greater than 6 months”

My charger has a “Storage” mode that is level I charge them to until they are required, I was advised by a model aircraft person to check then about every 3-4 months while in storage.

I did a bit of searching on the net and came across this article, explaining self discharge;

http://batteryuniversity.com/learn/article/elevating_self_discharge

and this one on storage.

http://batteryuniversity.com/learn/article/how_to_store_batteries

Both good bits of information to help make informed decisions.

#15

Tom, does each battery have proper voltage individually? It seems it must because you reported the overall voltage is fine.

So, it sounds like your pcb is bad… it does not sound like it tripped, since the batteries are at proper voltages.

Why not just buy another protection PCB, or charge the batteries normally and dump the pcb?

I’ve used batteries for years without a protection pcb.

Greg

#16

Good references Graeme! This info has been the accepted standard for many years, OEM cell manufacturers specification sheets support same…

If you’ll note the discharge curves clearly define the problems associated with discharge below recommended voltage termination, which is often the reason these cells fail prematurely. Improper care and feeding is commonplace IMO.

Michael

#17

Pretty funny on storing li-ions… if you want them ready to go, you are sort of damned if you do and damned if you don’t

Store them fully charged and they self discharge more.

Store them partially charged, and they self discharge less, but you have a lower state of charge anyway.

So, bottom line to me would be store them fully charged, that way I don’t have to check them so often, and whatever method used, you will still have to charge them when coming out of storage. (I’m assuming several months of storage)

I read the part where a fully charged battery is more prone to failure, but not sure I believe it much, but no matter, since we are talking storage, it loses a lot right away, therefore no longer fully charged.

Greg

#18

Hi Greg.
I discussed this matter with the Victorian manager of the Sanyo Agents here in Australia.
He confirms what you have said above.
His company quite often has unsold brand new cell only Sanyo batteries on the shelf for many months with virtually no measurable loss after 6 months.
The packs they make with protection pcb’s that I sell here in OZ, have never failed and, to the best of my knowledge, have minimal if any discharge when not being used.

Made up packs with protection pcb’s will discharge more quickly but still very little. Battery packs with pcb’s that can display battery voltage will discharge quite quickly.

Whilst I cannot comment on the particular cells used in Tenergy batteries, my supplier doubts they are Sanyo.
Cheap Chinese cells should be avoided.

Caveat emptor.

#19

I read the part where a fully charged battery is more prone to failure, but not sure I believe it much, but no matter, since we are talking storage, it loses a lot right away, therefore no longer fully charged.

Greg,

Back in the day when I was evaluating, cycling, grading and learning the peculiarity of the 18650 lithium batteries for onboard flight power systems 13 years ago I realized said anomaly, I recorded data over a two year span or so. Batteries stored fully charged, discharged faster and failed at a higher rate (as I recall it was better than 2:1).

Tony mentions a valid consideration; while Li-Ions likely have the lowest self-discharge values as compared to all other technologies, one must consider and or allow for quiescent current draw with cell/battery protection circuits. That said the self discharge rates are still very low of batteries that are young and have not been beat down with excessive discharge regimens.

Michael

#20

I think it’s lost one set of cells. A 12 cell 14.8v pack, so it has 4 rows of 3 cells.

The bottom cells measure 3.66

The next set measures 4.10

The next set measures 4.24

But the top set measures 0.79

If I get 3 new cells for this, should I do something so they all have the same state of charge before I put new cells in this old pack?

Hollingshed’s high-=power rifle is starting to sound tempting.