Question about LIPO and charging

bertus

Joined Apr 5, 2008
20,664
Hello,

Wich battery are you planning to buy?
There are a lot on the page:
Beat LIPO battery1S 2S 3S 4S 5S 6S 850mAh 35C 3.7V 7.4V 11.1V 14.8V 22.2V Lipo Battery for FPV Racing Drone Quadcopter

The charger board you show seems to be for a 2S 7.4 V version:
2S 10A 7.4V 18650 lithium battery protection board 8.4V balanced function/overcharged protection Good

Bertus
 

Thread Starter

christiannielsen

Joined Jun 30, 2019
298
actually it would be much easier to buy a power socket charger and a lipo 7.4 battery.For example this one (select color green).

But to me it looks like it only has 2 wires for charging. How can it balance the cells with only two wires?
 

bertus

Joined Apr 5, 2008
20,664
Hello,

The shown battery is 850 mAh.
The charger board is capable of 10 A.
You will likely need a much lower current.

The other charger will be much easier in use.
It looks like the other charger can be bought as a set with batteries of 2500 mAh.
The battery has 2 connections, on one side the 2 pin connections for output and a 3 pin for charging.

Bertus
 

jpanhalt

Joined Jan 18, 2008
10,109
The charger board should limit the current. 850 mAh batteries should charge at 0.5 to 1.0 C (850 mA max). That should be no problem as the charge port is probably rated at 1 A or more.
 

Thread Starter

christiannielsen

Joined Jun 30, 2019
298
I think I prefer the socket charger (EU) + battery.

But I need a small battery in size of a 9 volt battery or not much bigger. That is why I found a 850 mah.
 

LowQCab

Joined Nov 6, 2012
41
A USB Power Supply puts out (maybe) 1-Amp, at 5 Volts.
5 Volts is high enough to charge 1-Cell at a time.
You can't use 2- USB Power Supplies because they are not "Transformer-Isolated" from each other,
and in a 2-Cell LiPo Battery, like the ones shown, you can not electrically separate the Cells,
but you can charge 1-Cell at a time by using the "Cell Balancing" connector to access the connection
between the 2- Cells.
To charge both Cells at the same time, you must have a Power Supply that can generate at least ~10 Volts,
because each Cell requires EXACTLY 4.2 Volts REGULATED to within ~0.05 Volts while charging.
LiPo Battery charging, especially with the types of LiPo's designed for RC Hobbyists, have very
demanding, and exact charging procedures that MUST BE followed to the letter.
LiPo's will CATCH ON FIRE, AND YOU CAN'T PUT IT OUT, it's a chemical fire.
All you can do is cover it with sand, and then hope that the surface that it's sitting on won't catch on fire too.
Fires can happen from shorting-out, overcharging,
or physical damage that lets Air get into an individual sealed Cell.

Next, these Batteries are specially designed to be charged and discharged, at unbelievable Amperage rates.
You "can" use then at lower rates, but why spend twice as much if you don't need all that current ???
Notice that there is a HUGE "35C" rating on these batteries.
That means that they are designed to supply "up-to" 35 TIMES their normal Amp-Hour "C-Rating",
which is 0.85 Amp-Hours, times 35 = 29.75 Amps, but in reality,
the batteries on this page are garbage, don't waste your money.
If you really-really need all that Amperage, then go to a reputable Hobby Supply / Battery dealer like
MaxAmps.com, they can even make you a custom battery if you really need it,
but their batteries are 2 to 3 times more expensive than the crap you linked to.
You get what you pay for .............. (sometimes).

This brings me around to charging LiPo's.
LiPo's have a really low internal resistance, this means they can also be charged very fast,
usually on the order of 3 to 4 times faster than their "C-Rating".
The C-Rating is how many Amps can the Battery supply for one whole hour before being dead.
It's also a guideline for charging the battery.
Some types of batteries can only be charged at ~0.5-C, which is half of it's "C-Rating",
that means that it's going to take at least 2 hours to charge that battery at an Amperage that is limited
to half of it's "C-Rating".
But, a High Amperage LiPo can sometimes be charged in 15 minutes or less,
but this requires serious power from the charger,
4 times 0.85 "C-Rating" Amps = 3.4 charging Amps, at 4.2 Volts per Cell,
a USB adapter would take at least a full hour to charge each Cell, one at a time,
and may not have a high enough Voltage to overcome losses in the charging circuit,
and still be able to provide exactly 4.2 Volts.

The next item is "Cell Balancing", which is what the Charging Board you picked out is designed to do.
High Amperage LiPo's, with multiple Cells, MUST have some means of balancing the charge on each Cell.
And, while the Board you picked out will "probably" do the job,
I wouldn't buy it because it's too cheap, and you are depending on this unit to PREVENT a FIRE.

The Charging / Balancing Board that you picked out is designed to be powered by Car Battery.
It is also "Current Regulated" to below 10 Amps, and this is probably more Amperage than these
small batteries you have picked out can withstand, I don't really know, because they don't
advertise how much higher you can go over the "C-Rating" when charging,
and if they don't advertise the number,
then you must assume that they can only be charged at "1-C", which would be Current Limited to 0.85 Amps.
A charger that is Current Regulated to 10 Amps is going to try to charge the battery at a "12-C" Rate.
You can do this with many top quality LiPo batteries, if you're brave,
but with the batteries you picked out, you'll probably just start a FIRE.

Don't say I didn't warn you.
 
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