Nickel Cadmium or Nickel Metal Hydride ?

“Which battery would you recommend ?”
I have been asked this question or something similar many times in the past year. Not wanting to misdirect an operator on a $4000-$7000 purchase, in addition to finding out for myself, I decided it was about time someone should run some extensive testing in normal film operating conditions with nominal current draws on the batteries. The term normal to me is a situation on the film set in rehearsal mode where an operator would be powering up a monitor, video ass’t camera, transmitter, and F I & Z receiver/servo amp. Then of course the film camera itself when needed.
On the market today we see three popular battery chemistries, Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH), and Lithium Ion. Since the latter, Lithium Ion, at this time has very low tolerance for mid to higher capacitance draws, this battery technology for powering motion picture cameras has no legs to stand on. I have, however, seen some fair results in the past 1.5 years on using these batteries for other applications. More on this at another time. This leaves us with two practical battery chemistries left to use, NiCad and NiMH.
After talking with three of the major professional battery suppliers in the world, IDX Technologies, PAG and Anton Bauer, reading their literature, asking their technicians and engineers about cell types, performance, capacitance, chemistries. One thing they all agreed upon was hands down “if your components require a large initial start up capacity from a battery, you need a battery that has that capacity”. O.K. which one ?
Unfortunately it’s not that easy. 14.4 vs. 13.2 Vdc, 1 , 2 or 3 batteries on your sled, parallel or series your batteries, direct connect wiring (old style) or modern power circuits, linear power supplies, microprocessors, switchers, C cells or D cells, nominal power draws, multiple camera start up currents are all factors.
Out of the three manufacturers, Anton & PAG are the two that offer multiple options of both battery chemistries and a variety of voltages that fit very nicely into our industry. Both offer interactive and non interactive battery technologies, both manufacturers offer high quality chargers. Basically they compete for that exact same market. However, I have found a difference in one manufacturers battery receiving plate over the others. But this is not what I am testing for at this time.
So strictly out of popularity in the US market, I have chosen Anton Bauer batteries to test.

So lets do a side by side comparison of two battery chemistries. Same voltage, same battery manufacturer, same age of cells and similar number of cycles on each battery, age of batteries (5 months) , #cycles each battery 22-30

Battery Manufacturer: Anton Bauer
Both are 14.4 Vdc C cells
Hytron 50 - are a Nickel Metal Hydride type cell (NiMH)
Trim Pac - The Nickel Cadmium type cell (NiCad)

I am testing and comparing three 14.4 Hytron 50 watt hr. NiMH, with three Trim Pac 14.4, 45 watt hr. NiCad, non interactive.

My first comparison was pricing: Prices will vary.
Hytron: $375 ea.
Trim Pac: $235 ea.

Charger type was Anton Bauer 2000 - works for both battery chemistry types.
All cells tested were taken hot off the chargers, no battery ever sat idol for longer than 5 min. I felt this to be necessary for accurate testing. All voltages were measured at the battery block and remained very accurate on initial power up of each battery under a simple load - Monitor, Video Transmitter, Video Ass’t Camera, Digital Level, F I & Z Receiver. The voltage readout was a constant
16.4-16.6 Vdc on both battery types all the time.

My second comparison was charging times, since I had to keep recharging these batteries for testing. In all cases the batteries were rotated evenly between charging and discharging on each of the three batteries, in case of cell failure. (there were none) All batteries were drained at the same rate, and down to a constant 9.5 Vdc. Of course, this varied depending on which camera was being tested. Both battery chemistries were tested equally with each camera.
Charge times:
Hytron 50’s avg. charge time was 2 hr. 23 min. each.
Trim Pac 45’s avg. charge time was 1 hr. 17 min. each.
One could say that the charge time should be shorter on the 45 watt hr. vs.
the 50 watt hr. battery because of rated capacity. I could adjust the charge time to reflect a 50 watt NiCad charge time based on 45 watt data, but then I would have to adjust run times as well. So let’s leave it stand as we buy them off the shelf.

My next test was to set up a sled, as if I were in a rehearsal mode. Not powering up a film camera, powering only the following items all turned on and set:

TB-6 Smart Monitor w/Duo Digital Frameliner in the 1.66 aspect ratio
Modulus 3000 transmitter
Sony XC77 video tap
Programmable Digital Level
Preston microwave receiver

The motion picture camera was not plugged in to ensure it would not be turned on. This test was not to test a batteries effective capacity under mid to high capacitance loads, but rather a low capacitance load.
RUN TIMES: Low capacitance load
Hytron 50’s avg. 1 hr. 27 min.
Trim Pac 45’s avg. 1 hr. 21 min.
Hytrons ran on average 7% longer. However this is misleading because they are a 10% higher capacity battery, and should run the scenario 10% not 7% longer.

So here is a brief recap of results before we turn on the camera.
Hytron 50 Trim pac 45
$375.00 Cost $235.00 Hytrons 59% more expensive

2hr. 23 min. Charge time 1hr. 17 min. Hytrons take 85% longer to charge, in ideal weather.
1hr. 27 min. Low capacity 1 hr. 21 min. Hytrons lasted 7% longer, but
discharge rate have a 10% higher watt hr. rating than the Trim Pac 45’s
so they should last even longer
than they did.

This tells me that before I run film in the camera, I will deplete my batteries faster than I can recharge them using Hytrons, so I better purchase another charger and at least a few more batteries.

Camera Test #1
The first camera I will test using these two battery chemistries on will be the ARRI BL3. Ser#35872. Since I do not have an unlimited supply of film I will use the ARRI magazine tension test gauge to simulate tension on the take up side of the mag.
The camera was started and stopped every 200’.
Equipment the battery will need to power:
ARRI BL at 24 fps.
TB-6 Smart Monitor/Duo Digital Frameliner
Modulus 3000 transmitter
Sony XC77 video camera
Preston microwave receiver

RESULTS
14.4 Trim Pac 45- 2700’ on average at 24 fps.
14.4 Hytron 50- 2400’ on average at 24 fps.
Footage is rounded to the nearest 100’. I would run the camera until the camera failed to start on required power up or until it stopped running while it was turned on.

Camera Test #2
ARRI 435 ES Ser#7111
This camera, as we all know, is a 24 Vdc camera. So to enable a single battery to run at 24 Vdc we have run the battery through a newly designed 12/24 Vdc power switcher. This will be done of course for all battery chemistries.
Also, I am not advocating running your sled on a single battery. I am merely comparing two battery chemistries with same voltages, close to same watt hrs., same cell size “C”, uder the same loading conditions.
Running ARRI torque tension gauge on take up side of magizine, and turning the camera on/off every 200’.
Equipment the battery will need to power:
ARRI 435 ES at 24 fps
ARRI Built in color video system
TB-6 Smart Monitor/Duo Digital Frameliner
Modulus 3000
Preston microwave receiver
RESULTS
14.4 Trim Pac 45- 2200’ on average
14.4 Hytron 50- 200’ on average. No - this is not a typo. Every time the camera would start fine as long as the internal impedance of the battery would not drag its own voltage down below 15.3 Vdc at start up. The problem is the batteries chemistry. This battery has a very high internal impedance. Tests have proven every time the camera would start once but never twice with this battery chemistry.

The next test is to run these batteries at higher frame rates.
Camera Test #3
ARRI tension torque gauge to simulate film on the take up side of the magazine, using a single battery through a power switcher.
Equipment the battery will need to power:
ARRI 435 ES at 150 fps
ARRI Built in video system
TB-6 Smart Monitor/Duo Digital Frameliner
Modulus 3000
Preston microwave receiver
RESULTS
14.4 Hytron 50- 0’ on average at 150 fps
14.4 Trim Pac 45- 2000’ on average at 150 Fps.
By checking the digital readout on the sled I could see that these batteries still had plenty of voltage left in them, but not enough effective capacity to deliver the power needed at 150 fps. So I dropped down to 100 fps on the same batteries. On average the Trim Pac’s were able to deliver another 1400’ at 100 fps, and another 900’ at 60 fps. All on one battery. Bringing the total number to 4300’ on average, on one 14.4 Trim Pac 45 battery.
This was impressive.

Camera Test #4
Cold test. Since I am affected by cold working temperatures, I have done more than my share on cold weather work. It is important to everyone that batteries can deliver the power in cooler temperatures. I have worked with my West Coast compadres above the 45th parallel in the winter. You will most likely never see a larger power drain on batteries than when the temperature drops below 10 degrees Fahrenheit. Camera body & mag heaters automatically turn on, movements and lens’ stiffen, batteries remain cold losing their effective capacity.
So I have taken six fully charged batteries, three of each chemistry NiMH & NiCad, placed them in the freezer around 10 degrees Fahrenheit for 1.25 to 2 hrs. The ambient room temperature was in the high 60’s, so all batteries had the ability to warm up slightly during the testing period. The time varied in the freezer because it took time to run each test. But no battery was removed from the freezer until it was ready to be tested. Hytrons were the first cells to be tested.
The camera was started and stopped every 200’.
Running ARRI tension torque gauge on take up side of magizine.
Equipment the battery will need to power:
ARRI BL at 24 fps.
TB-6 Smart Monitor/Duo Digital Frameliner
Modulus 3000 transmitter
Sony XC77 video camera
Preston microwave receiver

RESULTS
14.4 Hytron 50- 0’
14.4 Trim Pac 45- 1600’ PLUS, I stopped the testing at this point, because I could
see the batteries were thawing out, and felt the test point was proven.
Next I took the remaining frozen batteries, set up an ARRI 435 ES and
wanted to see how they performed running this camera at both 24 & 150
fps. I once again used the ARRI torque tension test gauge to simulate
footage take up on both battery chemistries.
RESULTS
14.4 Hytron 50- at 24 or 150 fps. 0’ were run. The only speed I was able to achieve was 6 fps maximum.
14.4 Trim Pac 45- at 24 fps I ran 1600’ and stopped the test. Then I grabbed
another frozen battery and ran 2000’ at 150’ and stopped the test. Both
batteries had plenty of power to keep going. But I felt the test had proven
its point.

Summary
1) Anton Bauer 14.4 Hytron 50’s are 59% more expensive than a Trimpac NiCad 14.4, and by Anton Bauers own statements have at best one half the cycle life of the NiCad batteries they manufacture. Hytron 50- $375. / Trim Pac $235. non interactive.
So, if you own 7 Hytrons at $375 = $2625 x 2 = $5250.00 VS
7 NiCads at $235 = $1645.00 for the same cycle life.
This does not include the cost of chargers and shipping.

2) Hytron 50’s take 85% longer to charge in ideal weather conditions than the Trim Pac batteries, and could take up to 150% longer in cold weather conditions. Taking all batteries down to a 9.5 Vdc up to 16.7 Vdc when the charger says they are ready.
Charge times were:
Hytron 50 2 hr. 23 min. on average.
Trim Pac 45 1 hr. 17 min. on average.

3) Hytron 50s have a 10% higher capacity rating the Trim Pac 45s. But under average film production working conditions with even a low capacitance draw on these batteries, (monitor, transmitter, video ass’t & wireless lens remote system idol), Hytron batteries out ran the Trim Pacs by 7% on average, but according to their watt hr. ratings they should last even longer.

4) When running film camera, Under no testing condition did the Hytron 50 outperform the NiCad Trim Pac 45.
In fact the only time the Hytron NiMH came close to the performance standards of the Nicad battery was in running time in ideal weather conditions,
when we ran the BL 3 test.
In the cold weather testing Hytron 50 did not start the BL 3 camera.
(This is very important to note, see cold weather testing)

Camera & speed Total footage run - Trim Pac 45 Hytron 50
Arri BL 3 24 fps 2700’ 2400’

Arri 435 ES 24 fps 2200’ 200’

Arri 435 ES 150 fps 2000’ plus 0

Arri BL 3 24 fps (cold test) 1600’ plus 0

Arri 435 ES 24 fps (cold test) 1600’ plus 0

Arri 435 ES 150 fps (cold test) 2000’ plus 0

All camera tests can be verified by the owner of our very well equipped local camera rental house and one of their technicians, who supplied all the equipment for testing. Cinequipt, Inc, 651- 646-1780.
ARRI torque tension gauge is used to simulate film. It however is not a replacement for the torque and power draw film puts on a camera battery, but merely used for this test to add some additional drawdown of the camera power. It is as well safer to use than to repeatedly rerun film at highspeed through the camera body.

As always there must be a disclaimer, that test results may vary. But by the sheer number of batteries tested, cycle times, different current draws, and having no allegiance to any battery manufacturer, or chemistry. My only parameters was to find out the reliability issue in real life applications using Nickel Metal Hyrdide batteries vs. Nickel Cadmium batteries.
The only place where NiMH batteries may have a benefit is in the weight category. I say “may” because weight to some may not be of concern, or that one may need to add weight below the gimbal to balance the system depending of course on the camera and sled you are flying and how you wish to set up your sled. Using the Postal scale at two different post offices, that measure down to .05 of an ounce, this is the readings they gave me on the batteries.
Hytron 50 - 2 lbs. 1.3 ounces
Trim Pac 45 - 2 lbs. 10.0 ounces


OPERATORS FEEDBACK
I have spoken with a few operators who use the Hytrons and here is what they tell me bothers them when using Hytrons.
They no longer have any type of useful low battery indicator. I am told (by Anton Bauer) and testing has shown, Hytrons have the ability to deliver every watt hr. of power up to the last second and then they drop out completely. What this means is that you have very little ability before or during a take to know when your camera will fail, or to intelligently know when you should change your batteries under intermittent mid to high capacitance draws. All our usual low battery indicators on the Preston wireless, Modulus, or Seitz unit have preset low battery thresholds that the battery passes through on the way down through system shut down. Because Hytrons are designed to deliver every watt hr. at a high voltage, your low battery indicators pop on only as your system has already failed. Giving you on average about 2 seconds of low battery indication.
Yes, Hytrons do have an LED display on the side. Testing has shown me conclusively this bar graph to be very inaccurate when used on mid to high current intermittent applications, turning cameras on/off. This display does react better with low power and constant power draws with no flucuations.

In addition to the testing results above, I did purchase and test out three Hytron 100 “D” cell batteries. This battery weighs in at 5 lbs. 9 oz. and charges in 4 hrs. and 40 min. I thought that one of these cells would outperform two NiCad Trim Pac’s C cells. Well, once again to my surprise the 14.4 Hytron 100 watt hr. batteries still did not have the effective capacity to power up a 435 ES to 150 fps. Running at 24 fps on low power consumption applications, it did however out perform two Hytron 50s combined. More testing will should to be done to draw any more conclusions on these Hytron 100 batteries and capacities. I felt the 4.5 hr. charge time was just a little too excessive to make them useful.
I also tried out the 60 watt hr. D cell NiCad 14.4 batteries. They seemed to last a very long time, one battery had no problem powering up a 435 ES to 150 fps. In fact, I ran over 4000’ with the ARRI torque tension gauge before I stopped. But more testing should be done for accurate conclusions.
Anton Bauer states the one battery at approx. twice the watt hr. will always outperform two batteries at half the watt hr., all of the same chemistry, and I found this to be true.
Testing results have shown me conclusively how I will answer the question of “Greg, what do you think of the Hytrons?” Unquestionably, my answer will be, “Don’t get rid of your NiCads.” I also see Anton Bauer offers these 30 watt hr. Proformer NiCads 14.4 30 watt hr. batteries, weighing in at 1 lb. 14 ounces. I have not tested this battery, but by seeing what NiCads are capable of in comparison to the NiMH, I can imagine this to be an impressive battery.