The new lithium batteries are fantastic for a bunch of applications
from cell phones to car batteries.
Most of us have some power tools that use them but
the battery packs are EXPENSIVE
Here is a bit of information about the care and feeding of these
new batteries as well as information about building or repairing
these battery packs

This info is tailored to E Bikes but should apply to most
other stuff.

Maybe even a fancy pre rotater with a brushless DC motor?

http://www.ebikeschool.com/how-to-build ... 650-cells/

Hi.

I'll do that when the time comes.

I've been flying R/C planes and helis for more than 30 years,
so I know the tech. My heli uses a 12 cell LiPo of ca. 45 Volts.
And the small brushless motor can deliver 4 HP. That's enough
for a useful prerotator. The ESC's are easy to use also - they
are controlled by a pulse that varies from 1 millisec to 2 millisec.
1 being idle and 2 full power. Some gyronauts use a simple servo
tester, where you vary the pulse by turning a potentiometer.

I am looking at using a small Arduino processor to read amps
and then be able to make a push-button start. Because the first
few revs are so hard for the motor, I'm thinking of adding a
centrifugal clutch to the motor, just to get it going without
burning it out. Others just give the blades a few flips and then
start turning the potentiometer.

Cheers
Erik

Yes, LiPo batteries are awesome... until they get overcharged, or damaged.... then they turn into little volcanoes that you cant put out.... they just have to burn out. So, that is why I wouldnt like an electric car with a battery the length of the car... if a family is trapped in an electric car with a battery fire, the emergency services cant help, they cant be sure the ground around the car is not live... so the people in the car just get cremated... although the fumes will kill them long before the heat....

Just wait until electric cars kill a few people... or a bom chucker drives into a tunnel and shoots thru the floor into the battery.... everyone in the tunnel will get gassed...

Electric cars are the most dangerous things on the road these days... and soon there will be thousands more... not to mention, they dont pollute while they are running.... most of their pollution is done in their construction and the power stations making the electrickery to run them.... terrible things

The biggest (most cells) my heli's have is 4S, one of my boats is 6S and my biggest monster truck is 4S.... I cant imagine the power of 12S ... in reality, you could make a pronged fork, fit a 12S and poke someone with it and Bzzzzzzzzz... assume dirt temperature

I wish I could find the picture of mine.... it blew up and looked like a mushroom.
Stunk like shit during the whole flight!
Even with a voltage regulator set at 14V the damn thing gave in.
After spending all that money and going through the aggravation a good old fashioned motorcycle lead/acid battery was the answer.
Heavy? Yeah....and reliable!
Well NOTHING is when you are on a remote off field and need to start up that engine!!!

The LifePo4 batteries don't blow up like the regular LiOn .

I haven't heard of the lifepo4 batteries, but Lithium Ion (Li-ion)are docile and take alot to damage... and generally don't do much if you do damage them... these are like the 18650.... it is the Li-Po Lithium Polymer that are fantastic, but temperamental.... (Just like Nabs)

I have the Life-Po4 battery on my gyro.
.

lithium iron phosphate or cobalt are the best and safest.

Muz,
12s is 12 x 3.7 Volts (nominal). That's not going to electrocute anyone.
When you have a 4 HP motor on a heli, 12s helps to keep amps and thereby losses down.

Cheers
Erik

I know, I mean, it would be fun, amazing to have the power of 12S, because all of mine are 4S and less...

Each cell is 3.7v .... but fully charged is 4.2v .... so 12S is 50.4v... so that wouldn't tickle

My boats are 3S and 4S and the difference between them is noticeable... so 12S must be amazing

Of course you can electrocute someone with 12S? You just need a big enough step up and make sure you charge the battery well enough (or a 240v inverter)

It would definately be.... Bzzzzzz assume dirt temperature...

Making electrocuting folks great again

As for the issue of the batteries having a major meltdown IMHO that can be mostly
accounted for by 2 issues.

The first one being simple physical damage. That has been a problem problem
for a hundred years or more what has changed is that we used to associate that
issue with fuel tanks. Rupture a fuel tank or any part of the fuel system and you
could have some major problems up to and including fire or explosion.

The next issue being that the actual definition of battery seems to have changed.
The definition used to be a group of cells lashed together to to get a higher voltage
or amperage capability than a single cell can provide.

A common example is a car battery of the lead acid family.
They are generally made of 6 cells lashed together. each cell can produce
about 2 volts the 6 cells lashed together produce around 12 volts and are
typically charged to around 14 volts.

With lithium batteries each cell is rated for about 3.7 volts and generally
are charged to around 4 volts but the proper care and feeding of a lithium battery
requires another device that is called a BMS or battery management system.
On your common 18650 lithium cell the charging current MUST be limited
to 500ma "1/2 amp" or less and also limited to 4 volts.
Charging starts as a constant current process and as the cell reaches almost full
charge it is allowed to soak at 4 volts with very little current flow to get a full charge.

The BMS is supposed to control the charging plus also prevent discharging a battery
to much and also prevent the current draw from being to high.

If the BMS screws up a perfectly good battery can turn into a fire cracker..

I tend to think that a BMS failure is the reason for most of the catastrophic
lithium battery failures.
A $30 BMS can turn hundreds of dollars of lithium cells into a melted mess.
so when using batteries of the lithium family be sure to use a proven and reliable
BMS.

Keep in mind that with the time proven lead acid automotive battery system if you have
a voltage regulator go to hell you can produce a LOT of explosive hydrogen gas
that can result in a face full of acid or worse.

My thoughts were over simplified a bit but I did not want to write a whole book in one
post.
Just my 2 cents worth your mileage may vary.

Marc

I had a 6 volt lead acid battery explode in a golf cart I was working on...
It was a less than desirable experience to have, unless one likes being deafened in one ear for 2 days and having battery acid splashed all over themselves.......Yes proper care and handling are paramount for any energy source.

Lithium ion like the 18650 is fully charged at 4.2v same as each cell of a Lithium Polymer.... the thing with a Li-ion is it can be used to below 3v with little issue, however, if you get a LiPo below 3v, quite often it wont survive...

Yes, physical damage is is the worst enemy of any battery, but LiPo is worse, because they go off like mt vesuvius and they cant be put out. Some have those metals in them that explode with contact with water.

So, the danger is, if a bom chucker drives into a tunnel at peak traffic and shoots thru the cars battery... there will be alot of people in the tunnel gassed. If an electric car runs over half a brick, or a rock on the road that punctures the floor and the battery, the battery can erupt. If the driver notices smoke and pulls over, but gets it stuck in a ditch or between trees and cant open the doors... they will get gassed, then cremated. Emergency responders are not allowed to approach a crashed electric vehicle until they are sure the ground isn't live... so they cant rescue anyone until someone with an electrical gadget comes along to say it is safe to go near the wreck.

So, wait until the bad guys hack the Tesla or google car again and it crashes into a gas car with a family... and they get killed by an electric car.... very soon, electric cars will be off the road and banned. It will take a catastrophic accident or terrism for it to happen, but it will happen soon.

Besides, the 'green' electric vehicle is so 'un-green' it makes ones eyes water... People are working this out now... so, electric cars are doomed...

If an electric car misses a corner and goes off the road into a lake or river... it wont float on the surface for a few seconds then sink....

it will just go straight to the bottom because of the weight of the battery. Being so streamlined and heavy, if it runs fast off an embankment at 55 and spears into the water, it wont even slow down, it will just go into the water and hit the bottom, even 50' deep and stub itself like a cigarette....

People in electric cars are at grave risk from nearly every angle. A pointy front electric like a Tesla, if someone hacks it and instead of locking the brakes ON this time.... decides to switch off the brakes and go full throttle, will do like the splicer... and just go under the 4x4's with head high bullbars and truck decks and wont want to stop... even if the driver and passengers heads have already come off...

That is why these people are hacking the Tesla... to show the faults possible from hackers and ransomeware.... Once someone hacks a car companies fleet of cars sold to the public and makes all the airbags go off and says they will all go full throttle any day... they will instantly ALL be off the road.... how will that be for the economy?

Electric vehicles run by hackable systems not in the control of the driver are totally, totally dangerous....

And everyone is lapping them up...