Powering an Alexa

[John Ritter]

Just could not resist jumping in here............

 

This really has nothing to do with the original post/thread but I feel the need to back up "Mark" somewhat since he is

quoting what I have passed on about the Dionic 90 series.

 

Some history on the Dionic 90...Tech stuff: relates to just about all Li-Ion based packs.

most all cells are rated in capacity and then are rated at max capacity, so if you take the full rated capacity which

can be 2 to 2.5 times the true capacity then you are right back to 50% of quoted rating.

 

Here is an example: first generation Dionic were rated at 80 watts.... packs are made up of 3 cells in parallel, each cell is rated at

21500mAH or 2.15AH so 3 in parallel should be 6.45AH (at 4.1 to 4.2 volts full topped out charge) now you add 4 in series to get the 14.8 volt output.

 

Now if you add this up 6.45amps x 14.8 volts =95.4 watts, sounds good but wait the cell manufacturer only quantifies a 2100 nominal average

because no matter what cells cannot be manufactured with absolute precision.. hence only an 80 watt rating thus allowing some wiggle room.

 

Next generation Dionics.... cells have improved due to manufacturing process now 2250mAh 2200 nominal for a truer 90 watt rating but hold on

it is still rated at only 1 x capacity but can be discharged at 2x capacity....

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Anyway it gets long and boring after a while, later generation Dionic 90 are better than earlier versions,and re-celled are current cell production

for the best possible rating and output.

 

So to make a long story short 6.6 amp cells can be pushed to 12.2 theoretically, just like you can drive your car at 100 miles an hour all day everyday.....

just because your speedometer goes to 120.

 

2nd matter: the factory dionics have thermal protection no real in line circuit breaker or fuse, and just control board, this leaves the cells vulnerable, I add

a second thermal current limiting fuse inline with cell output that will self reset. The reason for this is that over 4 years of repairing and Re-Celling

hundreds of Dionic 90 packs I traced the warranty replacement problems to high current applications (cost me a lot to learn this) Hence I have added a fuse

to the battery, So far not one has returned with blown cells. (yes they do sometimes have other problems, try as I may I can't win them all)

 

I will cut this short and hope I do not ruffle any manufacturers feathers but some claims are on the liberal end, I will just say this, if you want a safe margin of operation

Use 50% to 60% of claimed rating as a good baseline for any application. also keep in mind that manufacturing variations can produce a great result and also a mediocre result

in the same exact product.

 

Regards John Ritter

[Eric Fletcher S.O.C.]

So to make a long story short 6.6 amp cells can be pushed to 12.2 theoretically,

 

In the end if they don't shut down you can use them in your application.

 

Batteries are a consumable and cost of doing business. As long as the batteries I use will run the stack then I will use them, and if the rental house supplies me with batteries you can bet that I will use them, beat on them and not really care if I am taking a few cycles of life off of them, better theirs than mine.

 

One other thing. When you go to a rental house and prep and they are using AB's I suggest that you have a 27xx charger so that you can read in service dates, current capacity and cycles. Get EVERY battery in the house and keep the 6,8,10,12 whatever batteries that test the best.

[James Sielaff]

Ran a Heden M26ve focus motor and the Alexa off the Dionic 90 (on camera). Batt life was short. About 30min. We did several takes. We survived. The battery kept working for the remaining 1.5 weeks of shooting.

 

Just figured I'd share that in case no one else was 'crazy' enough to damage a rental battery in the occasional pinch.