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[J.beazley]

At the stage of getting the right battery set-up in my Pollux.
Ive got a 6v 4ah SLA that sits in the hull and takes her down to the waterline nicely.

The problem ive got is i cant lay it flat in the hull, So i need you bunch of like minded modellers to get your digital scales out and let me know how much your battery's weigh .

My 6v 4ah is 670grams which is perfect for the little tug but too big in the hull, anything under this weight will be better. The smaller the battery the better on either 4.8v or 6v, im looking for a reasonable running time from the battery aswell.

Jay

[Shipmate60]

Jay,
Have you considered a Lead Acid 6 volt 3 Ah.
Mine weighs 600 gms but is longer and thinner than a 4Ah.

Bob

[J.beazley]

I was going to take my scales down the model shop and weigh each SLA and see which one would suit.

If i get time Bob i shall pop over and show you. maybe the 6v 3ah will fit  :)
In the process of making a battery pack from 4x C size 3500mah NiMH cells with solder tags, not being heavy the 4 cells with lead only come to 410grams.

Jay

[Colin Bishop]

Check this out. Weight and dimensions of 6v 3ah SLA battery:

http://www.modelpower.co.uk/acatalog/6v_sla.htm

[alan colson]

Get yourself 5 cells (6Volts) or 6cells (7.2Volts) and make up a pack yourself that will fit nicely into your model. The other advantage of this is that you can also charge these cells from the car providing you have the correct fast charger if the battery runs out of power whilst you are out for the day. Great if you are at a show for a weekend. Would be wonderful to see you at Alfold, check this out www.alfoldboatshow.co.uk

[malcolmfrary]

Having got the size and weight from Colin's link, make a cardboard box as a try-out to see how your intended battery will fit in the hull.  SLAs are not particular about being used upright, but should be upright when being charged.

[Tom Eccles]

Question please, from one who is confused by all this electrickery.

Why would an S.L.A. need to be upright when charging?

[Colin Bishop]

I've never found that SLAs needed to be charged upright myself. Mine are essentially built in and lie flat to keep the centre of gravity low. Maplins don't stipulate that they must be charged upright and say they can be used in any position. I'd have thought it would only be an issue at very high charging rates which might cause internal gassing. SLAs are not really suited to high charging currents anyway.

[malcolmfrary]

Any battery when being charged undergoes a chemical reaction, part of which involves the generation of gas.  In olde worlde acid batteries, you had to constantly check and top up.  The modern sealed ones have some tech trickery to allow the gas to be re-absorbed (might or might not be true - theres nothing I can do about it in mine because its sealed, so I choose to believe the "magic" explanation) which might not work if the battery being charged is not upright. 
Just something I read - if somebody has one that works OK on its side, it could have been the maufacturer being overly cautious when writing the instruction book.  A member of my club had a puffer which the builder had resined in place, and in that case, it would only charge if stood on one end, in the manner of an Atlas ready for take off.

[wombat]

Most modern SLAs - everyone I have encountered can be charged either upright or on its side. They cannot be charged upside down though - I guess because this will obstruct the relief valve. Incidentally Yuasa insist that theirs are not SLAs (Sealed Lead-Acid Accumulator) but VRLAs (Valve Regulated Lead-Acid Accumulator)