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Gear / Technical Help => Remote Power => Topic started by: Life In Rewind on April 02, 2015, 07:33:40 PM
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Am I reading this correctly?
http://www.newegg.com/Product/Product.aspx?Item=9SIA6UM2SD8698
Capacity: 50000mAh.
Input: DC 5V-1A.
Output 1: DC 5V- 1A.
Output 2: DC 5V- 2.1A.
Charging time: about 7 - 8 hours.
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It looks like there are a bunch of "50000mah" USB batteries on ebay in the $15-25 range. Some discussion on one of the amazon links for one states that it's probably not actually 50,000mah, a bit less, but still worth the price. Their words not mine.
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In the specs...
Note:nominal capacity: 50000mAh, battery, actual capacity: 12000-18000mAh
Not sure what that even means but thought it would pertain to this. I'm looking for something similar to run a DR-70d or DR-2d. Potentially something that would power 4 channels for entire shows.
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Most of these Chinese manufactured batteries now quote total Cell mAh and not the actual total battery's mAh performance
This battery is probably made up of 2 x 25,000 mAh 3.2v cells in series (with the charging port wired in parallel - using a diode, etc network). After the output traverses the DC-DC converter and battery gauge circuit the output is 12k-18k depending on load - battery will probably have a load sweet spot around 65-85% load (giving more towards the 18k performance)
DR-70d pulls 5w approx - this equates to 1 A at 5 V or 1000mAh - you should get at least 12 hours from it
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So they have found yet another way to confuse buyers.
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It's not unheard of...in fact it's a well known fact...that the Chinese cell manufacturers flat-out lie about the capacity of their cells. Someone that takes those cells and packages them into a integrated battery SHOULD test the capacity of the cells to confirm the total capacity of the battery. Whether they do or not is anyone's guess.
My advice would be to just be on your toes about a few things when you buy a battery. If they list a mah value without stating the voltage at which the rating applies, that's a red flag. At minimum, as Richard says above, you should probably assume that the rating is either 1) the lowest voltage the battery supplies, or 2) the voltage of each individual cell 'under the hood'.
Ideally, they'd provide either a watt-hr rating or both the mah and the corresponding voltage at that mah (which you can then use to calculate watt-hr).
Also, remember that a battery manufacturer can't work miracles. This is physics and you can get only a fixed amount of power from a fixed amount of any specific chemical compound. So, if the battery is one of the 'typical' chemistries that we all know about...Ni-MH, Li-Ion, or Li-Poly and it's claiming a 2x, 3x, or 4x capacity from a package that's not also physically bigger, be wary.