Hello from a rank beginner

historyman999

historyman999

Member
Hi,
I am new here and new to quadcopters. My question is about charging a Lipo and the iMax B6AC.

To ease myself in, I did a lot of reading and have finally purchased a JJRC H31. Something nice and simple to learn on, not too expensive for when I crash it and easy to fly. It comes with a single 400mah 3.7v battery. From my reading, I now know that this is a single cell battery. I have purchased some spare parts for when I break bits, and also 3 more of the same battery to give me longer flying times.
I now know that as these batteries are single cell, I don't need a balanced charger, but the "charger" that comes with it is a USB gizmo that plugs into my PC. I am assuming (dangerous assumption?) that this is a safe way to charge. But given the propensity for Lipos to go bang, I am not particularly happy with this arrangement, but I have bought a Lipo bag.

I am thinking that the iMax B6AC would be a better option, especially as when I progress to a bigger and better quad, the Lipos will be more than single cell. I would also like to be able to charge all 4 batteries at once if that is possible. The IMax doesn't come with a power supply and I have downloaded Youtube videos on how to make one from a PC power supply, but would a car battery charger fit the bill?

Thank you for your patience and your views, suggestions and comments will be gratefully received.
 
Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
I use the B6AC and love it ! ... Yes, it has already has a cord that plugs into the wall AND it can be used in the field too by connecting it to a car battery

There is no balancing a single cell battery because the definition of balancing is the equalization of the more than one cells in a battery pack

DO NOT try charging four batteries at once (neither in series nor in parallel) or you can blow something up (at worst, or get poorly charged batteries at best)

I've seen simple "boards" that will distribute power to more than one battery at a time but that's just asking for trouble ... The only safe and accurate way to charge four single cell batteries at once would be to build an adapter that not only provides the supply voltage to each battery, but ALSO has a balancing plug too, so that your basically treating the four individual single cell batteries as one four cell battery pack, which is something rather advanced so I'll not get into that here
 
Jackson

Jackson

USA member at large
Gyro Doctor said:
There is no balancing a single cell battery because the definition of balancing is the equalization of the more than one cells in a battery pack
Click to expand...
Let's say you hook up 4 batteries to a parallel charging lead before starting to charge. Their initial voltages are 3.6, 3.7, 3.8 and 3.9V. Within a couple minutes they will all be ~3.75V. You don't want a big gap in voltages to start, or different sized batteries but parallel connections are self equalizing. Thousands of those multiple battery harnesses have been sold, have you actually heard of anyone have problems? I tried a search, asking for problems/unsafe/caution etc, and nothing popped up.

The flashlight fanatics have been doing it for years.
166bvrc.jpg

balance.jpg


That said I guess the OP could get this.
http://www.banggood.com/Wholesale-B...ubsan-X4-Eachine-H8-p-51891.html?rmmds=search
 
Rick M

Rick M

Absent-minded professor
I use a 5x parallel charging lead sometimes to charge multiple 1S batteries for my Symas (micro Losi connector, I believe the same as the JJRC H31). It has the red JST connector, which you should get a lead for with your B6 charger. Like Jackson said, you hook them up to the cable for a couple of minutes before you start to charge. Then you can charge them at 3.7 volts (the 1S LiPo setting on your charger), and .1 amps per 100mah. For example, if I'm charging 3 720 mah batteries, the setting is "1S LiPo charge" at (.7 amps x 3 batteries) = 2.1 amps. 2 400 mah batteries would be .4 amps x 2 = .8 amps, etc. You can charge at lower amps just fine, but don't go higher.

The charging cable Jackson linked to actually has a 3S balancing connector as one of the connections, it looks like. You can plus this directly into the balancing connector on the side of the B6, but only if you are charging three batteries at a time. You would not want to use the (white) balancing connector if you were charging 1 or 2 batteries, since the charger will be trying to balance the voltage between all three.

Hope this helps. Link to the one I'm using as an example is:

https://www.amazon.com/gp/product/B018DQYEMW/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
 
Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
Jackson said:
parallel connections are self equalizing
Click to expand...

"Parallel connections are self equalizing" ... Really ?! ... Well sh*t then all of my college professors through all of my electronics engineering classes must've had it all wrong !!! :eek:

Simply put, in a parallel circuit the applied voltage is the same but the current varies
Conversely, in a series circuit the applied current remains the same but the voltage varies

In other words, without having a plug to monitor things, like while using a balancing charger, you are asking for trouble

Jackson said:
Their initial voltages are 3.6, 3.7, 3.8 and 3.9V.
Click to expand...

Let's examine your example using Ohm's law:
The difference between the highest and lowest voltages is only .3 volts
Volts = Amps X Resistance or Amps = Volts/Resistance
The internal resistance of a LiPo cell typically ranges between 2 to 5.5 milliohms (we'll use 3)
Amps = .3/.003 = 100 amps
So the highest battery* is being asked to instantly supply 100 amps to the lowest battery !!! (note)

That exceeds the 1C charging rating of that 400 maH battery by a factor of 250 times recommendation
Not to mention probably also the discharge rating of the supplying batteries* (note: yes, I know that current load supplied is actually shared by
the three higher batteries and not just the single highest one, so what, divide that figure by three and you're STILL (likely) exceeding the discharge
ratings AND (certainly) the charge ratings) ... Do people do it anyway ? Absolutely ... Would I recommend it ? Absolutely not, not even for a moment.

Like I said, you need a balancing plug so it's not an unregulated situation

As for those pics you've shown of makeshift charging rigs ... That's nothing more than proof that there's no shortage of stupidity to be found on the internet
and also hilarious in that the one brand name of the batteries shown is "Trust Fire" ... such irony ... If you try charging a LiPo without proper regulation
you can trust you may get a fire

Gyro Doctor said:
The only safe and accurate way to charge four single cell batteries at once would be to build an adapter that not only provides the supply voltage to each battery, but ALSO has a balancing plug too, so that your basically treating the four individual single cell batteries as one four cell battery pack, which is something rather advanced so I'll not get into that here
Click to expand...
Yep, I stand by my words, which is exactly what that adapter you provided the link for certainly safely do.


Also, your quote of me stating you can't balance a single cell battery stands too, that's a simple fact ! o_O
(Not to be confused with balancing multiple single cell batteries, and certainly not as shown in those pics either)

Ok, rant over :p
 
Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
Oh so now you're going to laugh at the fundamentals of electrical theory ?
Learn how to do basic current and power calculations first, here's a primer:



Now substitute 4.2 volts for "E" (the voltage level a charger will supply before turning off) OR .3 (the small voltage difference between the
highest and lowest battery in the chain) and anything between .oo2 through .oo55 for any of four of the values of "R" and then tell me what
values YOU come up with

A regulated power source (like an iMax) will either trip or smoke being asked to supply over 50 watts
An unregulated power source (like the other hard-wired batteries) will do their best to supply the current asked of them

Of course these ridiculously high levels are not going to be actually seen because there's other considerations that aren't covered, primarily
the limitations of battery chemistry, BUT THAT'S EXACTLY THE POINT

All I'm saying is that I do not recommend unregulated parallel battery charging (especially for noobs) because it can be dangerous, if you want to
insist on arguing with that premise then so be it, I'm outta here
 
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