Ultimate battery hog

[tvodrd]

http://www.theregister.co.uk/2009/01/08/dad_battery_challenge_droid_sub/

"An autonomous British robot submarine has just set out on a mission which will see it plunge deep beneath Antarctic ice shelves. Interestingly, the "Autosub" has no truck whatsoever with li-ion, fuel cells, stirling engines, hydrogen peroxide or any other trendy undersea power system: it runs on ordinary torch batteries, 5,000 of them to be exact."

Larry

 

[Mr Happy]

Let's see: at 20,000 mAh per D cell and 5000 cells, that is 100,000 Ah!!

Put another way, that is approximately 120 kWh.

I hope they got a good deal on the batteries!

(Do you think the battery manufacturer will replace the sub with a new one if any of the batteries leak? )

 

[SemiMan]

That is at room temperature. However, if this things is operating under sea ice, the temperature could be much lower. Given that it has a very long operating life, I would expect the self heating to be very low hence the batteries could be sitting closer to 0-5C. Hope they took that into account....

Semiman

 

[Fallingwater]

I imagine that's the reason why they aren't going with rechargeables.

On the other hand, with the amount of money that replacing all those primaries is going to cost, they might have been better off with a small RTG, if such things can be bought by privately owned firms.

 

[Mr Happy]

In bulk quantities, I expect alkaline D cells can be had for 50 cents apiece or less. So 5000 of them is not going to cost a lot of money compared to other options.

 

[Fallingwater]

If it was a one-time expense I'd agree, but with the amount of power a sub eats I doubt they last them more than a trip or two.

 

[davegLED]

$2500 for batteries is nothing, even if they only last one trip. The cost of designing a different solution would cost much more than this surely? I mean if you pay someone $50,000 and it takes them just 2 weeks to complete the whole design it would be $2000 just in labour to design.

 

[mdocod]

The break-even point for most rechargeable options happens after around 5-20 cycles for many of the various rechargeable options out there. So I guess it depends on how many times they plan to deploy. I have to believe that a lead-acid solution could have been arranged that would not be all that much more expensive than all those D cells, not to mention, WAY simpler since you can get much larger individual cell sizes, so the total cell count and wiring to deal with would have been way cheaper.

 

[crofty]

At the end of the article it says their working on a "next-gen, rechargeable li-ion version"

Wonder how many LED`s it would power :devil:

 

[Fallingwater]

The break-even point for most rechargeable options happens after around 5-20 cycles for many of the various rechargeable options out there. So I guess it depends on how many times they plan to deploy. I have to believe that a lead-acid solution could have been arranged that would not be all that much more expensive than all those D cells, not to mention, WAY simpler since you can get much larger individual cell sizes, so the total cell count and wiring to deal with would have been way cheaper.

And how exactly do they replace all those D cells? I imagine they have to either disassemble it from the outside and replace them one by one, or a dude has to crawl in and toss them up from the main hatch

 

[mdocod]

And how exactly do they replace all those D cells? I imagine they have to either disassemble it from the outside and replace them one by one, or a dude has to crawl in and toss them up from the main hatch

I was envisioning a great comedy skit based on replacing all those cells....

Reminds me of those "hoaxes" on youtube about tearing apart a 6V lantern battery to get 24AA cells for cheap.

"just tear open an old submarine and WOW, 5000 D cells will just fall out the back end!"

 

[Illum]

And how exactly do they replace all those D cells? I imagine they have to either disassemble it from the outside and replace them one by one, or a dude has to crawl in and toss them up from the main hatch

more points of contacts =
higher chance of intermittent contact
higher resistance
higher maintainence costs
...

I'm inclined to think they built a battery pack of sorts using a battery welder then wrapping it in plastic for water resistance. Ordinary torch batteries eh? Define ordinary:nana:

I can guarantee you, if theres no insulator or heater element on board your going to need extraordinary alkalines to give you any power at all. At -10~0C electron tadpoles are literally stuck on their highways. Heck, some say this sort of temperature actually impedes chip weevils

 

[shadowjk]

It's probably not that bad temperature-wise.

A range of 400km on one load of batteries. Assuming the sub is driving itself hard at its top speed constantly, 3.4 knots, the batteries would last a little bit over 63 hours.

That's 1/63C, folks, at maximum speed! The duracell spec sheet says "For most cells, up to 75 percent of the rated capacity at room temperature can be delivered at 32°F(0°C).". So that means they could be carrying 1000 extra batteries to compensate for the cold Duracell has the "up to" qualifier in that statement, but if you look at the discharge graph at the 60 hour point, you'll see the difference between 21C and 0C isn't far from the 75% quoted.

 

[Guy's Dropper]

I'd like to find out how it is that they are managing this. I can't imagine that using 5,000 D alkaline batteries is at all practical for application.:duh2:

 

[georget98]

Wasn't there another underwater research sub like this linked from here a few years ago? I think it used 1,500 D cells.

Someone here at work used to work at Benthos which makes a lot of underwater stuff. He told of having to solder together battery packs of 300 D cells in series.

 

[mpteach]

Sealed lead acid batteries would be many times larger and heavier than alkaline primaries. What is the cost difference per wh between leadacid and alkaline chemistries though?

 

[roadie]

like i always say for primary cells .... FIRE AND FORGET !!

maybe 'some company' donate the cells in the name of science, so money is no problem....

ooops
read the last sentence : "Their colleagues back in Southampton are working on a next-gen, rechargeable li-ion version."
R & D is a good thing u know....