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12-21-2013, 02:36 AM   #1
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LiFePO4 and other AA size high voltage batteries.

Hello,

What do you people think of using AA size Lithium batteries in a K-X?

They are in the 3.2v - 3.7v range so using 4 of them is out of the question.

But what about using two of them coupled with dummy batteries?

Here is a link of an ebay set:

2pcs 3 2V LiFePO4 14500 AA Rechargeable Battery 1200mAh w Dummy Cells Charger | eBay

LiFePO4 have very flat discharge voltage curve so they are great for high discharge tools like a DSLR.

Basic calculations:

LiFePO4:

2 x 3.2v x 1200 mAh = 7680Wh almost the same as the Lithium battery of K-30/50.

Eneloops:

4 x 1.2v x 2000 mAh = 9600Wh but with lower voltage and, arguably, worse voltage discharge rate.

01-27-2014, 12:11 PM   #2
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Bought the "kit" in the link I posted. It arrived today after about 4 weeks of wait (normal for shipments from china).

The batteries were already charged as the green light in the charger turned green after 10 min or so.

Tried in the camera without an apparent ill effects.

Will try again periodically to check how long they hold the charge.

I care more about low self-discharge rate rather than outright endurance as I find myself taking a dozen or so pictures every now and then.

I'll keep you updated in this thread.
01-28-2014, 09:31 PM   #3
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Thanks Deni, I'm interested to see how they fare.
02-12-2014, 03:25 AM   #4
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First update:

Initially the batteries were charge around 10 min before the charger showed green light.

First discharge:

Photos: ~ 100, ~80% with flash.

Video: ~ 10 - 12 min

Lots of viewing and reviewing, 3sec after shot review.

Time: ~ 2 weeks

The af is faster because of the higher voltage the a/f motor has more torque to turn the screw lenses (90% of the shots were taken with FA 50 f/1.4).


The camera is also lighter as the batteries themselves are very light and the two supplied dummy batteries are also very light since they are hollow.

Cons: You cannot rely on the battery meter as after turning yellow you can take around 3 - 5 shots before dying.

Full recharge took around 2 hrs.

Will keep you updated but so far I think it is a good investment for the type of shooting I do.

02-12-2014, 06:59 AM   #5
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QuoteOriginally posted by Deni Quote

The af is faster because of the higher voltage the a/f motor has more torque to turn the screw lenses
no... just... no.
02-12-2014, 10:25 AM   #6
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QuoteOriginally posted by maltfalc Quote
no... just... no.
Saying "no... just... no" brings no information to the discussion you are trying to start. Please explain why.

In the mean time power in W = volts x amps. The motor draws a constant amount of amps so if you increase voltage you increase power.

With 1.2v NIMH you have 4.8X power (where X=amps).

With LIFEPO4 batteries you have 6.4X power (where X=amps).

Prove me wrong.
02-12-2014, 11:37 PM - 1 Like   #7
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1. motors don't draw "a constant amount of amps" independent of what the voltage and load are.
2. the af motor isn't connected directly to the battery. the power goes through at least one voltage regulator and a digitally controlled driver circuit/speed control before it gets to the motor.
3. you're the one making the claim, it's your responsibility to prove you're right, not mine to prove you're wrong... but i did anyway.

but hey, don't take my word for it, i'm just some guy on the internet who repairs electronics for a living.
03-23-2014, 07:52 AM   #8
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So would you recomend those batteries? Becouse I am sick of ni-mh, I also found this chinse new invention on rip off bay 2pcs 1 5V 2800mAh AA Rechargeable Lithium Li ion Polymer Battery | eBay but I am little bit worried ordering batteries from china becouse there is planty of fakes.

06-16-2014, 11:14 PM   #9
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QuoteOriginally posted by lezion Quote
So would you recomend those batteries? Becouse I am sick of ni-mh, I also found this chinse new invention on rip off bay 2pcs 1 5V 2800mAh AA Rechargeable Lithium Li ion Polymer Battery | eBay but I am little bit worried ordering batteries from china becouse there is planty of fakes.
So far, I am happy with them.

Generally, I leave the camera a month without use, use it for a dozen of shots and then leave it without shooting again. For this type of shooting the batteries I bought are perfect.

Disadvantages:
  • Lower amount of photos per charge.
  • Cannot use the battery meter as the discharged voltage is 2.8v so well above fully charged NIMH.

I ordered 4 other batteries (4 Pcs AA 3 2V 1200mAh LiFePO4 Rechargeable 14500 Batteries 1 Years Warranty New | eBay) so I have always 2 sets ready to change.

Pretty happy with them.
07-20-2014, 10:47 PM   #10
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QuoteOriginally posted by lezion Quote
So would you recomend those batteries? Becouse I am sick of ni-mh, I also found this chinse new invention on rip off bay 2pcs 1 5V 2800mAh AA Rechargeable Lithium Li ion Polymer Battery | eBay but I am little bit worried ordering batteries from china becouse there is planty of fakes.
1.5V Lithium rechargeable cells, to my knowledge, are impossible. Batteries rely on the relative difference in reduction potentials of the materials used in construction. In the case of most lithium chemistries, they all sit within the mid 3V range, mainly due to the lithium content (lithium itself has a potential of around 3.04V). There's no way to reduce that potential voltage without creating a sort of miniature battery within itself, as the secondary material would absorb the electron release (and defeating the point of the ACTUAL battery).

The only way to have it at 1.5V would be to have built in circuitry that steps the voltage down. The battery description indicating that it has 2800mWh is also misleading. If we're using 1.5V as true, then it actually only has 1866mAh; with unknown loading sag, and overall possible output. I HIGHLY doubt they were able to wrestle circuitry into the battery itself that can manage stepping down a lithium voltage AND maintaining capacity to nearly Eneloop levels while being in the same physical dimension (step down circuitry takes space, meaning less for battery capacity).

A "normal" 14500 Li-Ion runs at 3.7V with 750mAh, or about 2775mWh. This is from one of the more respected Li-Ion companies, and not your cheap fake chinese cells that don't actually have their stated capacities. Eneloops run with 1.2V at 2000 mAh, or 2400mWh. Again, I do not see how they can manage to fit circuitry that is thin enough to NOT impact cell capacity relative to the normal 14500 cell.


tl;dr version: Don't buy them. More than likely completely fake.
10-27-2014, 01:53 AM   #11
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So far I am happy with them. They perfectly fit the way I use the camera where I can leave the camera without use for a couple of weeks, shoot a dozen and leave it without use again. The batteries have less capacity but it doesn't worry me as I have 3 sets (3 pairs as the other pair is just dummy so don't have to replace it).
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