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Universal battery charger & Li ion Safety WARNING

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Re: Universal battery charger & Li ion Safety WARNING

Postby bbrider » Thu Feb 16, 2012 5:17 am

I have a dc two slot usb power supply that is 5v 2100 ma split between the two slots with the full 2100 availabel when only one slot is used. Can I use this with my Gopro Hero1 or should I buy ANOTHER dc power supply that is 1000ma?
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Re: Universal battery charger & Li ion Safety WARNING

Postby BriteStar » Thu Feb 16, 2012 8:40 am

Should be OK.
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Re: Universal battery charger & Li ion Safety WARNING

Postby at361 » Thu Feb 16, 2012 11:54 am

BriteStar, so a higher mA charger is perfectly fine to use? For example, this one:

Xuma USB, $9.99, specs: Input 100-240 V AC (50 / 60 Hz). Output 5V DC 1500 mA
http://www.bhphotovideo.com/c/product/7 ... _with.html
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Re: Universal battery charger & Li ion Safety WARNING

Postby BriteStar » Thu Feb 16, 2012 12:47 pm

NO. Read the section "BATTERY CHARGING" again.
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Re: Universal battery charger & Li ion Safety WARNING

Postby PandaGFX » Thu Feb 16, 2012 2:17 pm

why not? all above should work ok as long as its 5.0V USB standard

a "USB Power Supply" is simply just that, it supplies power - it is not a "charger"

the actual Li-ion charging circuitry is built into the GoPro;
this is what limits the current & stops charging when full

power supply is rated at the maximum current it can supply eg 500mA, 1000mA=1.0A, 2100mA=2.1A
but the GoPro will only suck what it needs, about 1.0A when charging battery at its fastest possible rate.
It draws a little bit more if available when you're both charging & using the camera simultaneously.

If supply is 500mA (standard USB port) or less the battery will charge slower.
2.1A units are often called "iPad 10Watt".

you can also use a "portable USB batterypack" ... a decent size unit will contain 3000-8000mAh
and most are able to pump out 5-25A @ 5V if you're crazy enough to put sufficient load across it.
But when you hookup your GoPro or other charging-off-USB device it will only draw as much as it needs.
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Re: Universal battery charger & Li ion Safety WARNING

Postby BriteStar » Thu Feb 16, 2012 2:51 pm

"the actual Li-ion charging circuitry is built into the GoPro;
this is what limits the current & stops charging when full"
WRONG.

Simple Li ion battery charge circuits (aka GoPro) function on a time/ voltage process they are not current limited as you state.

Some lower-cost consumer chargers may use the simplified “charge-and-run” method that charges a lithium-ion battery in one hour or less without going to the Stage 2 saturation charge. “Ready” appears when the battery reaches the voltage threshold at Stage 1. Since the state-of-charge (SoC) at this point is only about 85 percent, the user may complain of short runtime, not knowing that the charger is to blame. Many warranty batteries are being replaced for this reason, and this phenomenon is especially common in the cellular industry.

I AM NOT GOING TO RECOMMEND PROCEDURES THAT I CONDISER POTENTIALLY DANGEROUS. THERE ARE NUMEROUS DOCUMENTED EXPLOSIONS OF MOBILE PHONE BATTERIES RESULTING IN THE LOSS OF FINGERS, LAPTOPS CAUSING HOUSE FIRES & RC CAR BATTERIES EXPLODING ON THE TRACK.

Still not convinced & a stupid enough to risk a Li ion battery explosion; make sure your life/ home insurance is up to date. Then check out this video.
http://www.youtube.com/watch?v=SMy2_qNO2Y0
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Re: Universal battery charger & Li ion Safety WARNING

Postby PandaGFX » Sat Feb 18, 2012 1:36 am

don't worry... own a lot more bigger lipos than that tiny 1100mAh GoPro bugger, puffed only a few past 18yrs ;)

methink there must is some current-limiting by the GoPro circuitry - it doesn't charge any
noticeably faster off a iPad 10W wallwart (2.1A max) vs a standard iPhone 1.0A unit.
Both takes ~2hr for the red light to go out from (what camera thinks is) dead flat, that's barely 0.5C.

Charged it once from partially charged (2bars on LCD)... took about an hr for red light to go off.
Lipo charge routine is highly dependant on cell voltage anyways, since current/capacity is preset.

Read somewhere some say it keeps charging for a bit after red light goes out, can't confirm
until i've rigged up a suitable USB power source with ammeter to tell what its really doing.
(Sony Cybershot camera's manual does write that though; & Vaio got 2 user-selectable cutoffs 80% & 50% too)


ok you've got me curious... HD2 was plugged in since dinnertime & should be fullycharged by now,
so i yanked out the lipo & probed it --> measured only 4.06V.

Wow that's not even close to 4.20V.
I'd expect @ 4.06V it'll still be in constant current charging stage, then just cutoff.
Be simpler to implement than a Reducing Voltage stage, although that's not rocketscience either.
Guessing that GP is (litigious!) US-based, yeah they probably plan to play it real safe :twisted:


Will wait till i get a few more batteries before any further probing;
be interesting to see if offboard chargers will pump them any higher vs runtime.

For the record currently getting 123mins recording from onboard charging.




----------------
@OP: sorry for offtopic hijack; yeah that iPad 2100mAh wallwart is what i use more often that not
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Re: Universal battery charger & Li ion Safety WARNING

Postby BriteStar » Sat Feb 18, 2012 10:42 am

From your observations, obviously there is current limiting circuitry in the system & I was wrong.

Single stage charging will only ever get the battery to about 85% capacity. Maybe you could trick the system by disconecting the charger when full charge is indicated by the camera, allow a rest/ cool time for the battery then recommence charging.

I have a twin B pack comprising 2X Li ion 18650 cells with built in charging PCB. With 10 volt supply from bench PSU the cells reach 4.2 volts then the charge IC disconnects.

We are talking about a Chinese batteries in the GoPro.

Raising the cutoff threshold voltage will provide higher capacity at the expense of battery life. Thermal control provides a safety net but be carefull.

Best solution is to carry a couple of spare batteries.
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Re: Universal battery charger & Li ion Safety WARNING

Postby PandaGFX » Sat Feb 18, 2012 5:02 pm

BriteStar wrote:[b]....Maybe you could trick the system by disconecting the charger when full charge is indicated by the camera, allow a rest/ cool time for the battery then recommence charging.


tried that the other day, no cigar. HD2 was corded for many hrs then I unhooked
to format a few cards; later hooked back to USB and red light did not come back on.


will test out the "wasabi" type charger in coming weeks

I've got something similar for Sony packs and it definitely pumps them
a lot closer to 4.2V than the camera's onboard circuitry algorithm.
Sony runs about 10-15% longer IMHO.



btw 1st post said GP sells USB PSUs... do they still?
Can't find any such thing in current GP catalog that's offered locally.
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Re: Universal battery charger & Li ion Safety WARNING

Postby BriteStar » Sun Feb 19, 2012 4:23 pm

Fuji BC-45W charge voltage 4.2. At full charge hot off the charger battery voltage = 4.19v.

Regularly switch the 16 GB SanDisk SDHC card from my Fuji to GoPro with no problems. All files are listed in the "DCIM" folder numerically: "100_Fuji "...... "101GOPRO" & so on.

GoPro only offer USB cable & the DC auto car charger with dual 1000mA USB outputs.

If you can recommend a suitable mains 1000mA charger I will include it in the list of recommended chargers on the original post.
Thanks,
H
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