Micro Motor Community

3.7v max amp input

#1

Ok quick question to open a discussion in regards to our batteries we use. Most of the batteries we use came with a charger that you plug into usb or you use another type of charger. So first off what is the output amprage of the chargers, ill give two examples. Secondly what is the max input amp that you can put into these batteries? Also so why im on the topic of batteries what is the max draw you can pull from the batteries, IE 150mah 30c or 45c it really dont matter the mah just the C rating. I want to be able to charge while im at the field a couple times but 90 minutes just dont cut it. Rught now im trying five batteries at 45c supposedly, and im putting in 1 amp so far im at 20 minutes and only put 335 mah into the packs mind you its through 5 packs. So basically i want to put in quck, safe, and no damage. Update 62 minutes 632 mah at 1amp input.

Thank you
Mike

#2

Ok started new set. Input: 3.7v 1.2amp. 2 batteries at 260mah per pack so i will update time and final numbers ok final was 490mah at 50 mins end voltage was 4.2

#3

If you want your batteries to last longer charge at 1C that is whatever mah your battery is. If you are parallel charging 5 batteries, you can charge at whatever mah your battery is Times the number of batteries.

So if you have 5 x 200mah batteries you can charge at 1A.

C rating is almost always lies for these kind of batteries. You normally have to watch reviews or ask the community.

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#4

Thank you imozeb, i appreciate the reply, but for instance to charge 5 150 mah supposedly 45c at 1.4 amp taking 70 minutes thats way to long. I can charge my 2 cell 2200 30c in about 15 minutes. I charge at a rate of 2.2a or more depending and that battery has never droped any voltage or punch or life, so there’s got to be a way of speeding the charge up. I know increase the charge rate/amp. So heres the important question what does 4- 716 motors pull in max amps? For instance my 4 cell battery get a constant 50amps pulled from it a half throttle and upt to 80+ on full throttle. So why cant i put 5 amps back in oh wait i do lol, im just tring to figure this out. One more example my cell phone has a pretty good size battery and at 4% life left i can charge and its a 100% in about an hour and that is getting charged at max .8 - 1.0 amp.

Si any way tommorow im gonna mark 1, 150 mah battery fly it charge at 2amp and continue to do this all day and see if this batter drops any performance…i let tne forum know

Thanks Mike

#5

Ohhh just want to say sorry for being a pain in ass lol

#6

This guy did some nice testing on brushed motors:

https://www.rcgroups.com/forums/showthread.php?2009496-1s-micro-mini-brushed-quadcopter-specifications-and-performance-data

I’m not sure why the 1S don’t charge fast whereas your 2S does. Are you sure about the charge rate for the 1S? USB chargers can’t output that many amps.

#7

The C rating of a battery is the “discharge rate” which is equal to C * capacity (mA rating) of the battery and has nothing to do with the charge rate. So for your example, a 150mAh 45C battery has a theoretical max discharge current of 6.75A. In practice however, a battery is not effective at the maximum discharge rate due to the large voltage drop at a high current (due to the internal resistance),

Most batteries will not have a charge rate specified in “C” which means that the safe charge rate is 1C which is the battery capacity rating. e.g, 150mAh or 2200mAh using your two examples could be charged at 150mA and 2200mA respectively.

So in theory, you should be able to charge any capacity battery at 1C which will take 1 hour. In practice however, a lithium based battery cannot accept the full current for the entire hour. The last 10-20% of the charge is slower (less current) so the battery can absorb the entire charge. Lithium based chargers use a multi stage charging algorithm so they charge at a constant current first, then when maximum voltage it reached (i.e. 4.2V), it switches to a constant voltage mode to finish the charge while making sure the voltage never goes above the maximum voltage (i.e. 4.2V)

A good analogy of charging a lithium based battery is the filling of a bucket of water with a high pressure nozzle. It fills fine without over spill for the first 1/2-3/4 of the bucket but you must lower the pressure to fill it to the top, otherwise the water will splash out due to the high pressure.

Unless your battery or the manufacturer specifies that you can charge your specific battery at a C rating >1 (which almost none do), then great, other wise no matter what size lithium battery you have, it will take 1 hour plus a little more for a full charge.

Of course you can charge it at a higher rate but if it’s not engineered to take it, you risk catastrophic damage to the battery and things around it.

Having said all of that, most modelers believe a modern lithium battery (aka 35C or greater discharge rating) can be charged at more than 1C. But most modelers are not electrical engineers either.

I regularly charge at 1.5C to 2C as long as I’m doing it in a safe place and monitoring it but I also know that I am prematurely reducing the lifespan of the battery and I take precautions and responsibility when I do so.

Lot of stuff there but it should give you enough key words that yu can google and find out way more than you ever wanted to know about charging and discharging batteries. :slight_smile:

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#8

The technical term for the catastrophic damage/failure you mention used by the manufactures is “uncontrolled rapid disassembly” lol

I guess they think that sounds safer than explosion and fire…

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#9

LOL! In the rocket science world, I think they call it RUD for Rapid Unscheduled Disassembly.

#10

I read a study where groups of 1s batteries were subject to different charge rates and their overall performance and number of cycles to failure was recorded. There were some interesting results which seemed to indicate that higher charge rates did shorten life by a few cycles but dramatically improved performance of the batteries as they approached the end of their life. I’ll have to try to dig it up. As I remember, approaching 5c charge rate lowered the number of “good” discharge cycles to about 40 before performance dropped.

The green charger above is actually not dumb. Each port has a dedicated smart chip which has a proper charging profile for a lipo battery. The charge rate can actually be set by selecting a resistor in the circuit for each chip. Stock they charge at about 500ma but they can be lowered By Swapping THE resistor. @Bobnova actually modified one to drop the outputs on the ports. He did one for me and gave me a nice range of outputs so I have some slow ports and some fast ports. My personal take on the 1s situation is that I abuse the batteries do hard in flight … that I don’t care how badly I abuse them charging anymore. I take my 40 good cycles and then chuck them for a new set of 6.
Do be carefully with some of the cheap chargers… we have opened and found some that just voltage cut at full without the proper profile and others yet that don’t ever stop charging. Sketchy. …

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#11

Thank you for all your replies.

Ok i only use the usb charger that they come with when im just relaxing and in no hurry. So as for my charger i use is full digital . So for example of i start my charger at 1.5 amp 3.7 in and final will be 4.2 o matter what( unless cell bad ) ok so it starts there and it will only push 1.5a in for a graction of the time as the voltage climbs and gets closer to 4.2v the onput amprage might stable out at .3a and stay that way untill final. So i guess in theory im not really charging at 1.5a . So i guess the manufacturer says safe up to 1c for liability reasons. Lmao ok back to reality thank you all for the comments. I guess it means i just neeeeeeeeeed alooooottttt more batteries.

Thanks mike

#12

@NotFastEnuf, I’d love to read that study if you can find it. Sounds like a interesting read.

@mike-heli, you hit it on the head. I currently have 30 1s batteries and 2 6-port Lipo HV chargers so I can easily fly for a several hour marathon with minimal breaks.

#13

I suggest reading this entire previous discussion initiated by bobnova. Good info and pictures, data sheets, etc there. The article I spoke of is linked in post 17.

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