Electric charging at field

[john e. holliday]

After reading the post about flights on new plane with electric I questioned the number of flights(dummy me).  Advantage - timers to set length of flight.  I know in IC(internal compression I can short tank a flight).  I also know most fields have no electric power to the field unless someone brings a portable generator.  I remember when I flew RC(radio control) a gentleman was charging his plane off his car battery with a charger made for that.  Needless to say he didn't keep track and had to get a jump start on his car.   He remembered after that to take a drive around the park where we flew after a few charges to the plane.  Do we have chargers for the CL  electric planes like that?

[Ken Culbertson]

After reading the post about flights on new plane with electric I questioned the number of flights(dummy me).  Advantage - timers to set length of flight.  I know in IC(internal compression I can short tank a flight).  I also know most fields have no electric power to the field unless someone brings a portable generator.  I remember when I flew RC(radio control) a gentleman was charging his plane off his car battery with a charger made for that.  Needless to say he didn't keep track and had to get a jump start on his car.   He remembered after that to take a drive around the park where we flew after a few charges to the plane.  Do we have chargers for the CL  electric planes like that?

Yes - I have had one in my car for..ever.  Even before there were Lipo batteries.  They are called "inverters" and cost anywhere from $15 to about $200.  They will suck your battery dry if you don't watch out!

They convert the DC in your battery to A/C into which you plug your charger which converts the A/C back to DC in the Lipo.  There may be some chargers that do it directly since I have seen some RC types with their hoods up and I have read some posts here and on RC groups about devices that can transfer from one battery to another.

Fortunately, we have A/C at our site.

Ken

[FLOYD CARTER]

Published guides * for LiPo batteries caution the user to not "fast" charge.  A LiPo cannot accept a charge greater than the rate that lithium ions can move back to the negative electrode, to a charged condition.

For longest battery life, and for safety in charging, the charge rate should not exceed 0.5C, where C is the battery capacity in Ampere-hours (usually given in mA-hr.

For a typical flight battery of, say, 2700 maH, or 2.7 Ampere-hours, the maximum charge rate is then 1.35 Amperes.  If you are field charging, the wait time is 2 hours!  Many of us do not wish to hang around waiting for a battery to charge.  If you only discharge your pack down to 20% or so, wait time is shorter, but still long.

I charge my LiPo batteries at home, and I typically set the charger so that it requires 3-4 hours for a charge.


* see "A Designer's Guide to Lithium Ion Battery Charging". Sept 1. 2016.   Digi-Key Electronics Corp.

[Dwayne]

3-4 hours? What kind of charger are you using? Granted I fly R/C as well so I bought a 300 watt charger, it charges 2 5000 MA 4s's at 1c in 30 minutes, I  have battery's that are 5 years old and still going. 

[Ken Culbertson]

3-4 hours? What kind of charger are you using? Granted I fly R/C as well so I bought a 300 watt charger, it charges 2 5000 MA 4s's at 1c in 30 minutes, I  have battery's that are 5 years old and still going.

That really is a long time.  I run 2800's in 4,5,6 cell depending on the motor and I typically run them down to between 25-30%  I store them at around 50% if they are under 30% when I get home and they come up to 99% in about 20min or so when I am ready to go out again.  That is at a 1c.  I have field charged in about 45min.  If there is a typical Saturday crowd you are getting to fly about every 45min so it is entirely feasible to fly all day on about 4-5 batteries.  You just have to remember to put them on the charger.  I used to compete with sailplanes so it is nothing new to make the charger part of your routine.

Ken

[FLOYD CARTER]

It might help to observe manufacturer's recommendations.  Of course, fast charging is OK if you accept the shorter battery life, and you are not concerned about fire.

The stories and reports of lithium fires while charging are all too true. 

[Ken Culbertson]

It might help to observe manufacturer's recommendations.  Of course, fast charging is OK if you accept the shorter battery life, and you are not concerned about fire.

The stories and reports of lithium fires while charging are all too true.

the batteries I use have a MFG Max Charge rate of 5c.  I use 1c.  I don't know how going lower will help.

Ken

[James Mills]

Doc,

I have a deep cycle marine battery that I take to the field if we need to charge.  I usually get several flying sessions before I have to recharge the marine battery. 

James

[Frank Imbriaco]

I bought a small generator , but found lugging it to the field an inconvenience. I charge off my car battery, but don't go overboard. I can safely get 3-4 charges for my 4S 2700s and 3 for my 4S 3900s,
For my RC needs, I get 2 for my 10S 5000s and 3 for my 6S 6000s.

I always charge 1C at home (strictly outside) the morning of flying and storage charge/discharge the day of flying.

Following this regimen since 2010 has worked, but I'm always vigilant. The biggest source of risk are the balance taps.  Being as they're thin guage, years of  frequent twisting /bending them  increases the risk of a breech. Then, you've got a problem which will short and potentially cause a fire.

CHARGE OUTDOORS !
 Even if its just smoke, the stuff is gooey thick and tough to get off ceilings and walls. I store my lipos  at storage state(50%) in real Army surplus 50mm shell boxes, the lid ventilated with 1/4" holes with furnace filter media above all batteries. The floor, sides and compartments are lined with 1/4" Styrofoam and I cap the female ends of the battery with a piece of un shrunk 3/4" heat shrink tubing that is sealed at one end.  Don't pinch the battery wire when you close the lid.
If that sounds like overkill, well...