View single post by dan3192
 Posted: Mon Mar 2nd, 2015 01:13 am
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dan3192

 

Joined: Thu Oct 14th, 2010
Location: Connecticut USA
Posts: 226
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Pete:

I'd like to respond. If I run out of time this evening, I will continue to respond until the subjects you brought up are addressed.

1. Re using protected cells to make a battery pack, I've purchased many of my 18650 batteries from a seller and assembler of commercial cells in Texas. I consider him an expert in what he does. He also sells on eBay under the user name sqtruong and answers an FAQ as follows:

Q:  Is there a Protection Circuit Board (PCB) in this battery pack?
A:  No.  The battery pack is intentionally built without a PCB.  Contrary to popular belief, a PCB does more harm than good to a battery pack.  A PCB prevents the battery pack to be balanced.  All lithium battery goes out of balance as the batteries age, there is no exception.
 
You can read more about this on one of his auctions at the link below. Be sure to note his ability to customize battery packs as well as his large inventory of commercial cells. If you dispute his opinion, please contact him.    
 
http://www.ebay.com/itm/USA-8-4V-7-4V-battery-pack-for-CREE-XML-T6-SSC-P7-18-6Ah-capacity-GUARANTEED-/321630762306?pt=LH_DefaultDomain_0&hash=item4ae2aff542
 
 
Another source of information is the international seller batteryjunction.com. They comment on the use of protected batteries as follows:
 



Home > Batteries > Rechargeable Batteries > 18650/18500/18350 Lithium-Ion Rechargeable Batteries

18650/18500/18350 Lithium-Ion Rechargeable Batteries




"Lithium batteries are a great option for today’s high end electronics as these cells typically have higher capacities than their alkaline counterparts. Although rechargeable batteries tend to cost a little more than standard alkaline batteries up front, over the long haul, these costs are reigned in because you won’t need to replace rechargeable batteries nearly as much as alkaline cells. Of course these upfront costs are lower when you purchase your rechargeable batteries at Battery Junction. Our selection of 18650, 18500 and 18350 series rechargeable batteries from the Ultrafire, Titanium Innovations, TerraLUX and Tenergy brands are typically priced well below retail and in many cases, you can buy these batteries in bulk which lowers the prices further. We have just about every size of rechargeable battery that you need, with products including protected and non-protected cells. The protected cells feature a patented Internal PCB protection against under voltage and over voltage. These protected cells are best used in single cell applications because the protection is based on the correct voltage of a single cell.

If you attempt to bundle protected cells as a battery pack, this defeats the purpose of the protection. Battery Junction also has rechargeable batteries in stock that do not have PCB protection and these batteries are perfect for pack building. The bottom line is that if you are a remote control car or airplane enthusiast in need of batteries to build battery packs for these devices, or if you have a high-quality Nitecore or Fenix flashlight that you need to power, Battery Junction is your best source for very high-quality rechargeable batteries available at very reasonable prices with fast shipping on most items."

Again, if you dispute their opinion, please contact them. I'm comfortable with my decision to not use protected cells in a pack, however, you are free to do what you think is best. Please allow me the same freedom.

On another point you raised, I monitor cell voltage when in use and know how long it will be before I need to recharge. Also, the newer, high capacity batteries I use have sufficient capacity remaining after an operating session so that overdischarge is highly unlikely. Finally, the receivers I use have the ability to shut down when voltage gets low. Therefore my use of protected cells (I only have 2) will be limited to single cell applications.

More tomorrow.  

Dan

Last edited on Mon Mar 2nd, 2015 02:53 am by dan3192

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