While wandering around the "Battery University" site I came across a posting titled, "BU-808: How to Prolong Lithium-based Batteries"  A link to the article is posted below

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries


KEY INFORMATION in this article is that a peak charge is a stressful event for a Lipo cell that defines its cycle life.  Knowing this leads to a dirt simple method to greatly extend the lifetime charge cycles for our Lipos.  All we have to do is to charge them to a slightly lower peak voltage.  What really caught my eye is that lowering the peak charge by only .1V per cell can DOUBLE the lifetime charge cycles for a Lipo pack!  The table showing the effect of lower peak voltage and battery life is copied and shown below.  (please forgive the miss aligned columns)

CHARGE LEVEL*           DISCHARGE CYCLES            AVAILABLE STORED ENERGY **
    (V/CELL)   
     [4.30]                            [150–250]                              [110–115%]
      4.25                             200–350                                     105–110%
      4.20                             300–500                                       100%
      4.15                             400–700                                       90–95%
      4.10                           600–1,000                                   85–90%
      4.05                            850–1,500                                   80–85%
      4.00                           1,200–2,000                                 70–75%
      3.90                           2,400–4,000                                 60–65%
      3.80                              See note                                  35–40%
      3.70                              See note                              30% and less
Table 4: Discharge cycles and capacity as a function of charge voltage limit

I have only started dabbling with this approach, so my results are limited - but promising.  For example I have a Classic airplane I am flying we 3Sx3500 packs.  When peaked to 12.6V (4.2V/cell) it uses around 2665 mah per flight.  I recently flew it with the packs charged to 12.3V (4.1V/cell)  and usage (predictably) increased by 96mah to 2761 mah.  However, end of flight voltage of the pack was 11.1V which is of course nominal for a 3S pack.  That sounds like nearly zero added stress on the battery due to a too-low voltage state.  I also use these packs another lightweight airplane that only uses 1900 mah per flight - the lower voltage charge will be a no-brainer there!

I was able to set the peak charging voltage to 4.1 by a dirt simple means; when I set my chargers to Li-Ion (instead of Li-Poly) the charging peak changes to 4.1V/cell instead of 4.2V/cell  (I like simple!)


Most folks I have talked to are flying with some excess in their battery capacity - it only makes sense for electric (or glow for that matter) set-ups to NOT fly right at their limits.  Since we fly with less than peak power for our power systems, always fly the same speeds and duration we can very accurately repeat our battery usage and determine if lower peak voltage will work for us.  If that applies to your case, then consider taking advantage of the reduced peak charging strategy to reduce the stress and extend the life of your lipos.

Does this also apply to cell phones and hand power tools?

Hi Doc
The answer is yes, BUT since those devices come with dedicated peak chargers it would be hard to implement.

In the article I showed, the author talked about how Cell phones are usually charged to their peak, because most folks want the longest possible extended charge, and that cell phones have their own "planned obsolescence"  which, curiously, is about the same as the life cycle of the battery!

In contrast, the article states that electric cars are designed to be charged at something less than the maximum peak because it is recognized that battery replacement in an EV is prohibitively expensive, and that it behooves everybody to help the batteries last as long as possible.

I already do that because I have tons of head room. I could go to the 4.1V but that means I end up with 30 percent in the battery and I wand to have piece of mind that I don't have a surprise.

The PowerLab 6 and 8 are great, but not currently being sold new.  Used are available.  Increment drops are 0.005v.

The TP Quad chargers allow increments of 0.01v.  Many chargers do as Dennis noted, down to to 4.1v set as LiIon charger, but you may need 4.15 or 4.17 for example to have enough left at the flight end.

The TP Quad chargers are easy to use and are reasonable.  You can charge 4 batteries, each with its own "charger" and balance as opposed to parallel charge.

By specifications, the TP1225HVC charger is similar to the Cellpro PowerLab chargers, but I they haven't been available for a long enough time to know about quality.  Of course TP has a reputation for quality.

From the table in the original post above, and from my experience with various cutoff voltages, 4.10v is only about 90%. or less.  Check the voltage after about 30 minutes off charge and see what the rested voltage and capacity is.  Also, the capacity may have dropped some with age and use, if that is applicable.

Thanks Denny for the info. I’m all about getting more life from our batteries.