[Michael Glavin]

FWIW:

Charge/discharge protection circuits or monitors are used by some and most definitely not all original equipment manufacturers or aftermarket pack builders/assemblers. Please consider that those that believe such is true of ALL Lithium-Ion cells or any Lithium cells for that matter may become complacent with the care and feeding of their Lithium batteries. Reckless behavior with this technology has long been its Achilles heel; miss information fosters bad habits IMO. Remember that the aforementioned protection circuits are ancillary devices or accessories not integral parts of the individual cells, accordingly you can include same or not.
As eluded to by others the concept that outside forces contribute to self or shelf discharge is true of the aforementioned protection circuits as a slight quiescent current draw is continuously drawing down the battery.

Best case for Lithium cell storage is in the discharged state for extended periods of time while frequent charging is purported to be desirable if in play. Regular deep discharge ultimately is the cause and effect of cell capacity reduction. In other words Lithium reaps benefits from frequent charge cycles regardless of the batteries discharge state.
Occasional testing of your batteries is paramount IMO, especially if your cells are stacked in series/parallel configuration. A dropped cell is realized by decreased discharge current, capacity reduction and reduced voltage under load. I have found many bad cells by using a loaded expanded scale volt meter, (no load voltage is a go, while a loaded voltage test depicts another reality). More sophisticated purpose built Lithium battery packs typically come with an additional pigtail attached with a plug which interfaces with a charger that can monitor, balance and charge each cell individually. The increased life of these batteries is nearly doubled when used in high discharge environments. Its easy enough to check a batteries individual cells with a voltmeter to identify a bad cell too.



Regards,
Michael Glavin

 

[Dave Ottney]

Good info Michael. One note though, for storage the Li-Ion cells should be at about 3.8v per cell. This is what we do with LiPo's (not appropriate for RR'ing due to ESC not having low voltage cutoff circuitry).

If one really wants to take of their cells, built the pack with a balancing plug on it and use a balancing charger like an FMA Cellpro4 charger.

Again I recommend looking at the RCGroups Battery forum (http://www.rcgroups.com/forums/index.php) to get very good information about various battery chemistries. LiPo's are big in flying but Li-Ion's are being in many cases. This forum has a very fast search function and its a very very active forum.
Dave

 

[Michael Glavin]

Dave,

Yes one can garner some useful info at RC Groups if you want to wade through many posts. That said Lithium Poly (Li-Po) cells just like Lithium-Ion cells are offered with or without the cell protection devices, so one can use Li-Po/Li-Ion if there careful not to discharge the cells below 2.9V respectively or if they have a cell/battery protection device it’s a no brainer. The same consideration is true of all battery technology deep discharge below minimum recommended parameters is detrimental to the cells long term life. NiCd and NiMH should not be discharged below .9V per cell respectively,

Does anyone pay attention to the voltage numbers or do you just run the trains until they slow down?

I have a lot of experience with Lithium Poly for powering model airplanes, 10oz models up through 30lb Giant scale. Li-Po is well proven and can provide high discharge currents. Probably the only consideration IMO for model rail roading is there form factor or outer protective layer is not has robust as Li-Ion cells in that that are constructed with a soft or pliable Mylar envelope so to speak. We also don’t really need the high discharge capabilities, but more is often consider better…


Regards,
Michael Glavin