LI-PO Batteries in subs

[anonymous]

What experiences have people had with these?

I have seen occasional mentions in the Forum and a recent new product announcement but I wonder if there any problems we should know about e.g safety, mechanical damage, water damage, protection against over discharge etc?

I am working on a small model of a Holland class sub and Li-Po are an attractive option in terms of small size and ease in providing approximately 12v but I don't want to be the first in my club with a working depth charge!

Your views?

Davy

[Guest]

http://subpirates.com/viewtopic.php?f=41&t=339

http://www.subcommittee.com/forum/icon_biggrin.gif

http://subpirates.com/viewtopic.php?f=41&t=339

[Wheelerdealer]

Don't over charge (bad) and

Don't over charge (bad) and use a compatible charger, dont pull more amps than the pack can handle, dont deep discarge or let the voltage drop below 3volt per cell (ruins cells,its pretty much 90% depleted at this point) and dont short circuit it (very bad). Works under water in the wet just fine in fresh water.
Electric RC planes are now pretty much runnung on LiPos. Lithium Polymer batteries are found in near all mobile phones now. Personally I think they are far safer in a submarine underwater than next to you head or your crown jewels

[Rogue Sub]

DO it. Im using my

DO it. Im using my helicopter lipos in my seawolf. Some one else has also run them wet with zero problems. Just make sure they are dry brfore charging.

[anonymous]

Thanks for the encouraging advice.

Running

Thanks for the encouraging advice.

Running them in water sounds very interesting and I notice in the instructions that they actually recommend discharging them in salt water prior to disposal - so actually using them in fresh water looks OK.

One problem you highlight, is the need for a battery shut off on the ESC. Aircraft ones all have this but I don't know of any boat ones (i.e with reverse) that do this.

You also mention that they are now in all sorts of electonic equipment that we carry close to our valuable bits!

It occurs to me that for submarines we may be able to use these more normally rated Lipos (i.e without the high peak current demand for aircraft) Anyone know a good supplier (in the UK)?

Thanks for all the advice so far.

David

[Wheelerdealer]

Try something like this
http://www.ashtekelectronics.com/shop/h ...

Try something like this
http://www.ashtekelectronics.com/shop/h ... 29816.html

Better than a cut off and risk losing your sub due to lost power.

I've used these guys, http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %26fvi%3D1 batteries work fine (I always assume the 50% of the C rating when dealing with unknown brands but thats still more than enough for the current draw you'll need.

[Guest]

As you know how to

As you know how to code PIC's, you could use the output from the low voltage detector that Ramesh suggested to trigger a failsafe or perhaps soften the throttle response to the ESC.

This would give a better indication for model submarine use than a sounder, which is almost useless when underwater.

Andy

[anonymous]

Interesting again, thanks.

I suppose I

Interesting again, thanks.

I suppose I was hoping for something more ready made. Those model flyers get everything done for them!

I could do something with PIC's. I suppose the best way to signal that your batteries are low would be to turn off the 11v supply for a few seconds every minute , say. Leaving the 5 v supply on.

Thanks for the Lipo link too, Ramesh. I'm just amazed how cheap Lipos have become! I think I will go staight from lead acids to Lipo without going through Nicads, Nimhs etc. etc..

David

[Guest]

Something like this perhaps?-

http://www.dimensionengineering.com/SmartBEC.htm

Something like this perhaps?-

http://www.dimensionengineering.com/SmartBEC.htm

[anonymous]

Just the job Andy!

Those flyers

Just the job Andy!

Those flyers have been at it again!

David

[tabledancer]

I`m using a lith./ion 7.2

I`m using a lith./ion 7.2 pack in my boat for 2 yr.,no problem.I wraped the pack in a balloon and run it in the wet.
TD

[anonymous]

Thanks Tabledancer,

That's reaasuring. I am

Thanks Tabledancer,

That's reaasuring. I am no expert on the different chemistry involved but I assume that lithium ion batteries also have risks attached if misused?

It all looks very promising and I have just ordered a Lipo as per Ramesh's suggestion.

Thanks for all the help.

David

[anonymous]

Hi All,

Just a little feedback

Hi All,

Just a little feedback on this.

I have carried out some successful initial pond trials of the Holland using a lead acid battery but I will be trying it with a Lipo very soon. (I need to save the internal hull space.)

On Andy's suggestion I ordered and used one of Dimension Engineering switch mode power supplies (Ordered from Technobots here in the UK) and it is very small and works very well.

Worth looking at for anyone dropping a 12 volt supply to 5v with a BEC or separate power supply. If the heatsink is getting hot that is the power you are wasting.

As far as the Lipo low voltage warning goes, I intend to combine an opamp voltage comparator with my favourite Velleman kit water detector.

Thanks for all the useful advice so far.

David