[grindez (OP)]

I'm looking for different batteries from 1 to 15 Ah and with 24 V. Does anyone have any suggestions? Pros and cons to the batteries. It shouldn't let out any gas either. The battery is to be put in an airtight capsule under water. Does anyone know if there are any batteries that work in temperatures over 200 degrees celcius?

[chris]

200 C sounds like an ambitious target, although my laptop feels like it's getting close to that sort of temperature sometimes!

Chris

[techmind]

The parameter, in addition to capacity (voltage and Ah) is how long you want it to last for, and whether it is rechargeable.

200 Celcius is going to be very ambitious, and I doubt you'll get much shelf-life at that temperature.

Do you need a low internal impedance (ie will you draw power in short high-current bursts, or only a slow trickle)?

Is physical size an issue, or not really?


Have you considered supercapacitors?

[RD]

Modern submarines still use lead-acid batteries...
http://www.przoom.com/news/29810/
A battery from a truck will give 15Ah @ 24volts,
[it may also give you a hernia when you lift it  []]

[Bored chemist]

I don't think this will help a lot, but it's interesting anyway.
http://en.wikipedia.org/wiki/Sodium-sulfur_battery
It certainly works above 200C- in fact that's too cold for it.

[RD]

Liquid sodium, under water, it had better be "in an airtight capsule"   [:0]

[grindez (OP)]

Size doesn't matter. The battery would be used for short high current bursts. And last for a while. The battery should be rechargeable. I haven't thought of supercapacitors.

[grindez (OP)]

Could a fuel cell on methanol work? OR does it emit water?

[techmind]

Size doesn't matter. The battery would be used for short high current bursts. And last for a while. The battery should be rechargeable. I haven't thought of supercapacitors.

How long must it last between charges? Hours? Days? Weeks? Months?
And what is your average load?

Is this for some under-sea oil monitoring widget or somesuch???

[grindez (OP)]

The battery would be used for oil monitoring on the sea floor. It would be placed in a nitrogen capsule with 1 atmosphere (pressure isn't an issue). Do you have any suggestions?

[lyner]

Submersibles are usually pushed for payload, I believe, so a primary cell would probably be best. Weight for weight, their energy capacity is significantly better.

[RD]

The battery would be used for oil monitoring on the sea floor. It would be placed in a nitrogen capsule with 1 atmosphere (pressure isn't an issue). Do you have any suggestions?

Just a thought, if you include a device which converts tidal-energy or sea-currents into electricity then this could be used to keep the battery charged, rather than having go to the trouble of hauling it up from the depths to be recharged every time the battery became low on power.

[grindez (OP)]

The battery won't be taken up from the water while charging. Too expensive to use primary batteries. Cannot go to dephts of 1000 m and more just to change a battery every month.

[lyner]

So do you have a buouy on the thing and hook up every so often? Or how do you find it?

[grindez (OP)]

The battery will be connected to the umbilical. So it won't get lost.

[lyner]

So why not power it via the umbilical?

[daveshorts]

200°C is certainly a challenge for most battery technologies as their electrolytes are water and they will boil at 200°C, although if you are at the bottom of the sea, you may find that the pressure helps you as it will increase the boiling point of the electrolyte... although this would be using the batteries outside their design tolerances and not something you would want to do on a production device.

There seem to be some batteries based on an ionic liquid electrolyte in development which have a much higher boiling point so will work at higher temperatures, but I don't know if any are available to actually buy though.

[lyner]

Possibly the power supply is the 'poor relation' in equipment. I guess there is, by now, no option to change its placing in the capsule because there is bound to be a position which would be cooler than 200C, bearing in mind it's immersed in liquid water.

[qazibasit]

why dont u insulate the simple lithium batteries. make a potential space b/w the battery and insulating material and wrap the batteries in it. this will atleast prevent it for like 20-30 minutes.