DPV research

[TooCold]

Noise takes energy, period. Conservation of energy is a thing.

How much is lost via noise, I have no idea, nor how to quantify it.

Well I guess you could record the noise and play it on a speaker and measure the watts

Sound is generated by vibration; noise (undesired sound) - undesired vibration. Vibration can be outside audible frequencies and would still consume energy to generate. Subsonic vibrations probably (I would guess) consume more energy than audible. On the other hand energy losses through waste heat are probably much more signifcant when considering battery life.

When the vibration (audible or not) is generated by a motor-driven system then (I would also guess) it's more a sign of drivetrain inefficiencies and/or wear-and-tear.

 

[lostsheep]

I'm curious: in the context of the OP's question, is noisiness really a desirable feature you look for in a DPV?

I think you misunderstood what I meant. I didn't say that I DESIRED a noisy scooter, I said that I HAVE a noisy scooter. The excess noise tells my dive buddies when I am around. This is helpful when I am following, if I drop too far back that the leader can't see the nose of my scooter, he can still hear me. Similarly, if we get separated they know I am not far.

Features I desired were listed as:

I’ll take a shot at it.

User replaceable batteries
Ability to accept smaller housing/batteries or larger based on desired run time.
As few hull penetrations as possible.
Battery meter
Integrated compass
Inertial nav ?
Speedometer
Can fly on an airplane
Ambidextrous controls
Kill switch
Thru hull charging
Integrated mounts for accessories

 

[TooCold]

I think you misunderstood what I meant. I didn't say that I DESIRED a noisy scooter, I said that I HAVE a noisy scooter. The excess noise tells my dive buddies when I am around. This is helpful when I am following, if I drop too far back that the leader can't see the nose of my scooter, he can still hear me. Similarly, if we get separated they know I am not far.

Features I desired were listed as:

got it. thx for clarifying

 

[TooCold]

@Jona Silverstein thanks for the very informative post. I'm a little confused though ...

all they changed was driving the motor from BLDC to Sensorless FOC

As for the efficiency, there isnt much difference between sensorless and sensored, only a few % but the difference between those and BLDC is pretty significant.

I think of BLDC as referring just to the motor type, that is "BrushLess DC", with two categories of drive method: "sensored" and "sensorless". FOC is sensorless. Using hall sensors or encoder is sensored. What kind of drive method do you mean when you say "BLDC", and how is it not sensored or sensorless?

 

[Wibble]

Sound is generated by vibration; noise (undesired sound) - undesired vibration. Vibration can be outside audible frequencies and would still consume energy to generate. Subsonic vibrations probably (I would guess) consume more energy than audible. On the other hand energy losses through waste heat are probably much more signifcant when considering battery life.

When the vibration (audible or not) is generated by a motor-driven system then (I would also guess) it's more a sign of drivetrain inefficiencies and/or wear-and-tear.

The Blacktip noise reduction in software version 1.15 was something to do with the AC waveform to drive the motor being made more sinusoidal.

There’s some info on DiveXtras website

 

[Wibble]

Just take them out of the tube. It is only a draw when they are plugged into the tube.

If I’m on the boat for a day I’ll load the batteries and seal it up on land and only open it when back and on it’s side, e.g. in the car boot — so no drips fall in the scooter.

This could be 8 hours or more.

 

[stuartv]

If I’m on the boat for a day I’ll load the batteries and seal it up on land and only open it when back and on it’s side, e.g. in the car boot — so no drips fall in the scooter.

This could be 8 hours or more.

Ditto. And if the difference in draw in that time from land to diving it is enough to make the batteries be out of balance, then that is a serious design flaw... even if it's something that would only manifest over a period of time, and only if you always put the same battery in the same position.

For me, I have my batteries labeled 1 and 2 and I don't pay attention to which is which when I put them in the scooter or charger, so I would expect which has been in which position in the scooter to, historically, be somewhat random.

 

[tbone1004]

Alright, couple things, some of which have been touched on.

First and foremost, the Genesis batteries are NOT UN38.3 certified, nor are the ones that are sold by Fathom. They live in a gray area the same as the large size canisters from Light Monkey in that the individual cells are, and they are technically disconnected, but as they are still in the same pack it is very much against the actual rules. Does it matter/will you get in trouble? Probably not, but people have had their supposedly UN38.3 compliant Light Monkey packs confiscated because they were over 160wh so if you want to risk that then by all means go for it.
The PTB's are there to remove liability from the manufacturers as well as the cost/hassle of having to deal with them. For the vast majority of divers a 12ah Blacktip is more than enough. A few years ago a UV18 with ~400wh of capacity and a UV26 with ~600wh was considered a really big DPV. The Blacktip is in line with the UV18 in terms of range/speed/etc and is more than enough scooter for anyone except long range cave divers.
The strap system/having to remove the batteries to charge is a consequence of this design, but up until very recently the Genesis was the only DPV that didn't have to be opened to charge. Dive Xtras has chosen to run the PTB's in series on their low voltage side. I have not asked them why, but the obvious reason is to have a "limp home" warning if one of the packs dies and the voltage is cut in half. If they were run on their higher voltage side of the Flexvolts then they could be charged in the DPV and you would have higher power but wouldn't easily have the warning if a single pack failed and that could be a problem. There is no "push pull", the brushless motors operate under full voltage at all times and the frequency of the pulses are what is being controlled, essentially pulse wave modulation which can also run brushed DC motors to simulate a lower voltage, but in this instance it is controlling the specific RPM of the motor, very similar to how EV's work and industrial machines that run with variable frequency drives. This is done with most modern scooters with the exception of the SS Viper and the Suex DPV's. I'm not aware of any other commercial DPV's that still run on brushed motors.

 

[geoff w]

... The PTB's are there to remove liability from the manufacturers as well as the cost/hassle of having to deal with them...

When you stop to think about it, it's as much a business decision as anything. Dewalt probably has more engineers working on designing PTBs, and has spent more on battery pack R&D, than any DPV manufacturer has engineers. As newer generation 21700 cells come out, Dewalt has the engineering and manufacturing to offer up 15 AH PTBs in the same form factor, and weight, as their current 9 and 12 AH offerings (although probably not TSA approved at that point). Not dealing with battery packs frees up Dive-X to focus on their scooter design and manufacturing, and leverages everything Dewalt does with PTBs. Plus no battery warranty issues for them to deal with, no long term battery support, and when owners need new batteries they're readily available at Home Depot, Amazon or eBay. Plus, like with everything else, liability, so if a PTB catches fire (I've seen it happen to a buddy's Blacktip battery when it got wet), it's a Dewalt liability issue, not Dive-X's

 

[lostsheep]

Agree with most of that but want to point out that 15ah are not the same form factor or weight. Also, 15ah does say that with the transport cap on it is 3 individual 90wh batteries so I think they should be able to fly.