robbe seawolf v.2.

Hi.
I am building this sub, (what a pain), and it does not make clear how you recharge the battery,
I know i will have to constantly withdraw the tray, but the wear factor seems to be
future problem in the waiting.
I am using a nicad 6v 3000 nah cell.
If anyone knows of a foolproof way of carrying out this chore,
i would be greatfull for any advice.
Cheers John.W.

HI John
Just a idea you could put a coil of wire in side water proof tube or box what ever you are using and place another coil on the out side of water proof box when you won't to charge nicad pack in side that way you would never have to take tray out of water proof box or tube to charge. What you would do is set up a inductive field they use the same idea for charging tooth brushes plus you could make a unit that would switch the sub on when you put it in the water charging circuit it self would be in side sub its self and could be made very small hope it helps
SUB JOHN

I think as a general rule - charging inside a WTC is not a good idea anyway. I think even NICADS can "offgas" some hydrogen under rare circumstances.

So generally, make the WTC easy to open and close. (You usually just need to do this for ventilation.

If you have to put power in (or out) external connectors (threaded rod, for example) are fine and only corrode slightly at 12v. (John's "induction" system sound a bit complicated.)

David

Hi Sub John and Dave.
Two birds with one stone!!
John. thank you very much for your input, but sadly its way over my poor old (74), head, but the thought was there. Cheers.

Dave.
The solution you offer is simple and practical, as this is my first sub,
i am finding the instructions hard going, for the robbe, not at all teutonic!!
But lateral thinking is being brought into play here.
and i am coping.
It will be an exellent grounding for my next project, what ever that may be,
so there is all to play for, its too easy to get into the cant be bothered sindrome
at my age, "Pensioner Power" is needed.
I will work something out as i go along, i only intend to use internal recharging
now and then. and open up for inspection, on, say a fortnightly basis.
Thanks guys for your input, it will not be wasted.

Cheers John.

HI DAVID
Normally if you have nicads that give off gas from venting it means you are charging or discharging them to fast,but if you where to use a Polly cell type battery i could not see there being a problem as they do not vent in any way, even if you wonted to make it simple you could fit a nylon bolt with a silicone rubber ring under it balancing plug for charging Polly cell could sit under that so all you would have to do is unscrew bolt out and plug charging plug in.

I have seen on other forums where people have put heat shrink sleeving around nicads seal the ends up and they say it works fine, and they charge them in side the sub would not fancy doing that my self

SUB JOHN

Hi friends,

the danger of an explosion due to battery gases is real and shouldn't be underestimated, so I can only confirm David by his advice of never charging the batteries in a sealed hull. Over the years several battery gas explosions had already happened in Germany, for example see the following link:

http://www.ig-schiffsmodellbau-berlin-mahlow.com/index.php/dies-a-das/41-modellbau-ist-nicht-ganz-ungefaehrlich-

That explosion happened on an exhibition and thanks god there hadn't been severe personal injuries although pieces of the model had been spread in a radius of approx. 50 feet. That modeller collegue had used NiMH cells that are "normally" considered as "gas tight". But as you can see there must have been some leakage of hydrogen, perhaps due to overcharging?

So you may leave the batteries in position for charging but do definetly open the sealed pressure hull and provide a certain ventilation to avoid accumulation of hydrogen (remember: a mixture of 4 percent hydrogen or more becomes explosive).

Kind regards
Hermann

Hi.
Ok i will open up the EVERY TIME i charge,
No problem, as i have now got the wtc to open up much more easily,
i will conform, i am an ex fireman, so i aught to know better!!!!!!Cheers John.

HI ALL

What i did to avoid accumulation of hydrogen, inside my big sub i use 5x12volts 24AHR GEL type battery's plus one 12 VOLTS 17AHR GEL type which is one big battery. When the sub is on the surface vent is open to take in air and what happens is compressor runs sucks air out of main sealed chamber in the sub and stores it in air tanks at 140PSI and then uses it to blow ballast tanks next time you surface, this way fresh air is always took on board and got rid of to blow ballast tanks so hydrogen is always kept low in side the sub. The sub all so has got a fan cooling the insides .

The trouble is with a lot of these accidents to do with battery's going BANG!! is to do with people not charging them correctly

If you look at people that have had poly battery's go BANG its more often there fault doing some thing wrong as back in the early days of the first chargers coming out you had to use jumpers on PCB board to select how many cells you wonted to charge it is a recipe for some thing to go wrong, then you had to select with jumper for the currant you wonted Plus even when sub is switch off if pressure plates was left bolted down vent would still stay open

SUB JOHN