# Li-Ion batteries.



## TonyWalsham (Jan 2, 2008)

My foray into Li-Ion batteries has been brief and instructive.

Due to a misunderstanding of exactly what the electronic Low Voltage Protection (LVP) circuit fitted to my packs did when it took effect, for the time being I am no longer going to offer Li-Ion batteries for the Australian market.

I was told that when the LVP cut in, it shut off the output completely. That was not the case.

My testing determined that, whilst it certainly did limit the current, it did not shut off completely. The load of the loco lights and logic overheads very quickly took the battery voltage below the point where the charger could actually charge the battery. This is called "going to sleep". It is possible to get the battery to "wake up" but the procedure is not something I am prepared to advise consumers to do.

For me to consider selling any sort of batteries they *MUST* be idiot proof.
Until my supplier is able to locate a different circuit that will shut off the battery completely, except for the 5 ma overhead, regretfully I am not prepared to sell them.


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## K27_463 (Jan 2, 2008)

Tony: your supplier has a poorly designed protection pcb. They need to do some research and find an up to date design. Too bad this happened. I have never seen one that worked in the manner you describe. EVERY one I have ever used offered total shutdown- both on the low voltage side and over voltage / overcharge. 

Jonathan/EMw


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## TonyWalsham (Jan 2, 2008)

Thanks Jonathon. 

Perhaps you could suggest a suitable pcb we could use?


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## Stan Cedarleaf (Jan 2, 2008)

Tony.... I'm sorry to hear that you've had that problem with your supplier. I must agree with Jonathan that they were not properly protected. 

I certainly not a "techie" in the battery field but I've been using the 14.8 mAh 4400 Li-ion packs for some time now with pcb protection with great success. They run until the voltage drops below the pcb limits, train stops, I change batteries and continue running. I know you do most all your installs with batteries on board so the locomotive or tender would then need to be brought to the charging station and recharged with the proper Li-ion charger.

Here are 2 links for suppliers here in the US. They also supply just the pcb which you will find on each site.

PCB only

All Battery.Com The proper 1.5 Amp hour charger charger is at the bottom of the page.

PCB only

Battery Space Again, the proper 1.5 Amp hour charger is at the bottom of the page.

PS..... I use them because they are *Idiot Proof*....


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## itsmcgee (Jan 4, 2008)

Stan, how long does it take to charge that 4400 pack using the 1.5 charger. I have the same pack with a .5 charger and my one complaint is charge times.


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## Greg Elmassian (Jan 3, 2008)

Stan, the first link for the PCB has this item: 

"Low current standby mode when cells are discharged. " 

The idea of the low current mode is to keep the memory alive, but not allow operation... it seems this board acts EXACTLY like what Tony does not want. 

If you look at the datasheet on the second link to the second pcb, you will see it is the identical board also. 

So we need to look a bit further... 

A suggestion: use a relay so that when it goes into low current mode, the relay coil drops out and cuts power, including itself... 

Unfortunately, you will have to have a circuit to re-latch the relay, and not draw too much current... on further thought that may be tricky with a relay without a manual reset.... 

Let me think on it. 



Regards, Greg


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## Stan Cedarleaf (Jan 2, 2008)

Posted By itsmcgee on 17 Aug 2009 09:16 AM 
Stan, how long does it take to charge that 4400 pack using the 1.5 charger. I have the same pack with a .5 charger and my one complaint is charge times. Charging times are generally 3 hours when the pack has shut down. I've used the .5 amp hour charger but like the 1.5 much better. 

I have a .5 for my 11.1volt 6600 mAh batteries and they take 8-10 hours to charge, but I get 6-8 hours of run time out of them..


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## Mike Reilley (Jan 2, 2008)

Posted By Greg Elmassian on 17 Aug 2009 09:43 AM 
Stan, the first link for the PCB has this item: 

"Low current standby mode when cells are discharged. " 

The idea of the low current mode is to keep the memory alive, but not allow operation... it seems this board acts EXACTLY like what Tony does not want.....

Regards, Greg 



I saw that too...but the data sheet for one says MAX draw is 30 microamps...and the other PCB says MAX draw is 35 microamps. Frankly, that's zip. Putting that into practical terms, it means that over a year, with the batteries discharged to the minimum where the cut off takes place, these boards are going to absorb 300 mah. Over a month, the loss would be 25 mah. Over a week, the loss would be just 6 mah. On a 2400 mah pack, that's pretty minimal...especially if the storage time without being recharged is measured in weeks.


Now...compare that to the projected capacity loss from age alone...20% of capacity per year of shelf life. That would be 480 mah for a 2400 mah pack if it's kept fully charged when on the shelf for a year. New stuff in the Wikipedia on this topic talks to reduced capacity loss when the batteries are "stored" in a partially charged state. 

"At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year. However, a battery in a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures, which will significantly shorten its life. Different storage temperatures produce different loss results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.http://en.wikipedia.org/wiki/Lithium-ion_battery#cite_note-23[24] " 

I couldn't find any data regarding what voltage the cells sink to after cut off...and the continuing 35 microamp draw. From my Navy work, I do recall that the voltage drop off as the cell capacity is used up is quite steep. That's good for the low voltage cutoff circuit...makes live easy. 

But, remember, the question here is twofold...what's happening to the battery...and can an idiotproof fix be found. Regarding the first question, we know that the purpose of the low voltage cutoff is to protect the future battery capacity. If it's output voltage goes below cutoff, chemistry changes begin to occur that cripple the battery capacity faster...kind of like keeping them fully charged while they're not being used.


As for the idiot proof fix...I'd be looking at the charger end of the equation. The Wikipedia article says " This (LVC) circuit prevents deep discharge in normal use. However, when stored for long periods, the small current drawn by the protection circuitry may deeply drain the battery. Some applications attempt to recover deeply discharged cells by slow-charging them." Since there is a way to "wake up" the LVC circuit, perhaps we should be lobbying for Maha and others to add some software that looks for this situation...and does what is necessary to "wake up" the LVC board...and charge the battery. THAT would be pretty idiot proof.


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## Greg Elmassian (Jan 3, 2008)

Good analysis Mike... in practical terms, if the loco is discharged to the threshold where it won't run, then maybe the small current that can still flow is not much compared to the internal self-discharge. 

If you took 20% (77 degrees on discharged battery), then does it seem that self-discharge would be faster than the 30-35 microamps? 

Tony, you may have absolutely nothing to worry about unless the user does not run the train for a year AFTER leaving it in a discharged state. I'd say that that kind of abuse of a rechargeable deserves a replacement battery! 

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

Thanks for the input. 

Stan. 
Having them built into the loco is not the problem. Unattended running is the problem for the packs I had. 
Thank you for the suggestions.

Greg, 
I am not sure what you mean by "absolutely nothing to worry about". 
I am well aware about the small overhead current draw draining the battery more deeply after a long time. 
What concerned me is that my battery supplier is using a LVC that does not actually cut off the battery voltage *completely*. The battery pack was still able to deliver enough current to power loco lights and electronic overheads before it went down below the "going to sleep" threshold. 

I need to cover myself for those users who simply leave a loco running unmonitored and come back to find it stopped and the battery unable to take a charge. 

I think there are two solutions: 
1. A LVC cut off that actually cuts off fully. (Except of course for the aformentioned overhead). 
2. Mikeys suggestion to get the charger manufacturers to devise a procedure that takes care of the "going to sleep" phenomenon.


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## rmcintir (Apr 24, 2009)

This would be a great project. It requires two inputs, voltage and temperature. The logic is pretty simple. The real work is in creating the various curves for voltage and temperature to determine when to cut off. The actual design is pretty simple. Creating the empirical data tables to act on is the tough part. It would also be good for NiMH.


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## Greg Elmassian (Jan 3, 2008)

Hmm... I guess I was not clear... 

The absolutely nothing to worry about meaning the boards Stan recommended... they should not do what the ones you have are doing... 

big difference in current.... MICROamperes... 

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

Greg. 
OK I got that bit. 
I still have to worry about the LVC not actuallly cutting out supplying enough current to run lights etc.


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## Greg Elmassian (Jan 3, 2008)

Just for grins, I would order one of those boards... with the specifications given, it should meet your requirements. the 30-35 microamps should not run anything like lights, and again, this very low current drain, roughly 1,000 times less than what you experienced with your system, should do the trick. 

Regards, Greg


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## James Kuhns (Jan 12, 2008)

Now I know what Greg is doing when he doesn't answer his phone. 

James


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## Mike Reilley (Jan 2, 2008)

For the continuation of this thread...it's been derailed to another thread....go here http://www.mylargescale.com/Communi...fault.aspx


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## Greg Elmassian (Jan 3, 2008)

!!!!![/b]


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