National Free Flight Society

SEN 2424

  1. More on Charging

More on Charging
A few SEN issues back we talked about our experience in charging and controlled discharging od LiPO batteries intended for timer applications. There is a little more to that story.

Firstly the charger that we used that gave a bad result and only partially charged the battery was a sophisticated charger with many options.   Some of the electronics that we use  have a charger included, this is the same for many consumer products too. The reason why this is possible is because quite a number of the semi-conductor manufactures make a chip that with the addition of just a  few resistors, capacitors and maybe and LED is a very good charger for a particular capacity of LiPo cell.  Below is a link to the product list of just one such manufacturer of their mainly one cell, but some are 2 cell chargers. Just to show you how many there are, and this is only one manufacturer.

These small chips make it possible to develop a very compact charger, sometimes with a variable charge rate and maximum voltage.  There are also available and typically work very well.  There are some links below.

When we charge our small batteries we typically use a max charge voltage of 4.2 volts and the battery supplier says that the nominal voltage is 3.7 volts.  Recently a number of higher voltage LiPo batteries have appeared on the market. These batteries are charged at 4.3 volts and have a minimal voltage of 3.8 volts.  Many of these contain graphene and sometimes are called HVLi.
Reading what our friends on RC Groups say about the graphene  LiPo is generally positive.  Some have had bad experiences but overall the positive outweigh the negative by a big margin. I think they are good choice for performance applications.

During my testing of my friend’s battery I also tested a 220 mah HVLi graphene battery from Hyperion.  The test of this battery was very promising with a flat discharge curve. I had bought this battery a while back but had not tested it because I did not have a charger that would do a battery of this size with a 4.3 volt cut off.  Recently I found an interesting battery charger from Banggood, this charger is intended for people who fly lots of small indoor R/C model that are powered by a single small LiPo, the ideal size for a F1B timer !  This charger will do 6 cell at a time.  Initial use of this changer also looks promising.  I have run it off a transformer, off a large hobby LiPo and off my LiPo emergency car starter battery.  There is a link to this battery below.

This is the up to 6 cells at a time battery charger (needs 12 volts)

This is the link to the grahene high(er) voltage battery that looks good for a F1B timer application.

This the Australian simple LiPo charger that I have used, the word Free in the company name Freetronics  is a bit of a misnomer as they do charge for the charger !

This company has an excellent reputation and their products are used by many electronics innovators and hobbyists

or this

Caveat Emptor

During the process of writing this I got a call from another F1B friend, he uses a Cooney/Foremost or ADR timer and wants to upgrade the battery from about 100 mah to 250 mah because he wants to use the timer battery to power a flasher.  The good part of this is that he realized that the flasher would draw much more current so he  knew he should upgrade and was looking for a charger to better handle the bigger battery.  The hidden bad side is that when integrating components from different suppliers there are sometimes some hidden gotchas (problems).  In this case a flasher can have high momentary current draw that might cause problem, another potential source of problems is that whatever electronics is used to make the LED flash may generate some RF that could flow down the power wires and upset the timer or servo in the timer.  The most important thing to do with a new electronics installation like this is to run a series of “flights” with the model on the ground for at least 3 minute flights and to do this at different battery charge levels.

One good point about using the batteries intended for the small indoor R/C models is that they have a high “c” rating which means they can deliver a higher current with a drop in voltage.