Large capacity batteries.

[Paul75Participant @paul75]

[Paul75Participant @paul75]

Hello everyone.

I'm completely new to the world of r/c boating so here's the first of probably many silly questions.

I'm looking to power a largeish model ship with a GRP hull approximately 6 feet long with a scale displacement of about 20kg, driven by four 540 motors and equipped with other auxillaries. I'd like to use the model for at least 2 hours on one charge of the batteries.

I contacted a local battery supplier and they stock 6v 12Ah sealed lead acid batteries weighing 2 kg each (dimensions 150x100x50mm) which they say are suitable for model boating.

Do you think I'd be over-stressing the ship's hull by installing one or more of these monster batteries? I would take the precaution of installing the batteries on wood boarding to spread the weight but I wouldn't want the ship to fold in two when I pick her up out of the water! Perhaps it's more prudent to install a larger number of smaller capacity batteries?

Please let me know your thoughts.

Many thanks,

Paul.

[The Long BuildParticipant @thelongbuild]

I know a few guys who use these on smaller vessels with no problems, and as they weigh 6kg as well provide some of the ballast. These are 12v however

**LINK**

[ashley needhamParticipant @ashleyneedham69188]

I dont think you will have a problem with folding hulls, but all the weight will be in one place, and it may be better for the balance of the boat to have two smaller batteries to get a better performance on the water.

No need to get loads of very small ones.. I find that larger SLA last longer than small ones, being more tolerant of the charging/discharging cycle….or it may be I just dont use them to full capacity to find out how much charge they ARE holding!

I would make room for two large batteries (as you have loads of room), but wait until you can try a ballasting trial before puchasing anything,

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

If its a model of a, say, 40000 ton warship at about, say, 1:125, rather than 540's, think of something with more poles, such as 545's. A working rule of thumb I was given stated that the motor should have more poles than its prop had blades.

The batteries will need proper support, not so much as to prevent the hull folding, because it will be rigid enough with the deck fixed, more to make certain that they stay put. You hear of full size ships being lost because the cargo shifted. A model with a wandering battery illustrates the problem.

I wouldn't use a car charger with any SLA, dedicated SLA chargers are available and cost less than replacement batteries.

A single battery has the merit of simplicity. With multiple motors, if there are multiple ESCs, you have the option of getting the reliability of one battery per ESC wired individually or commoning the batteries and distributing power via fuses.

[Paul75Participant @paul75]

Many thanks for your replies. As Ashley has suggested, I think I'll experiment with the ballasting of the ship to achieve the most stable set up with an even weight distribution first.

As for the plumbing of the electrics, I think I can safely predict lots more questions coming your way!

Thanks,

Paul.

[Dave MilbournParticipant @davemilbourn48782]

Allow for the extra length of 555 motors. You will ultimately fit them instead of the 540s……….
DM

[ashley needhamParticipant @ashleyneedham69188]

Hear hear. 555`s should be the order of the day at this size. Using 540`s unless geared may be cause for concern in the AMP and HEAT department.

THEN, as they are fairly slow revving, you can use the common 7Ahr 12v SLA batteries; these may be a bit cheaper than large 6v ones possibly due to being common.. What size props are you contemplating ?? Ashley

[Paul75Participant @paul75]

I understand that the 4 props are three-bladed with a diameter of about 3.5cm. I say "understand" because I'm buying the incomplete model from a fellow Model Boater and will be collecting it in a few weeks time – so I'm getting way ahead of myself! Patience certainly isn't one of my strongest virtues but I thought I'd seek your advice on certain general topics before I impulsively rush out and buy the wrong thing.

Many thanks again for your advice – I'll certainly be seeking more detailed advice once I've collected the model.

Paul.

[Ian GardnerParticipant @iangardner62867]

I would certainly endorse the idea of building battery boxes, I have only recently seen one model sail off with a distinct list because the battery was just flapping about in the hull, and another practically turn turtle on launching as the battery shifted when the boat was put on the water. I use a ply box or tray secured to the hull after trimming in the bath.

Ian

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hello Paul,

when I built the Sea Crusader (Celastine) she was poered by two MFA Torpedo 500 motors, both run off a 6V large gel battery [about 12Ahr] and she would run all day. She was about 6feet long.

I had to add ballast, and added it using a bolt on keel beneath the hull made from solid copper buzz-bar. You can see that in this image. It weighs in about 5Kg and is attached with two bolts up through the hull.

To this day she has never turned over, and I have sailed her with some success in competition.

Kim.

[TelstarParticipant @telstar]

Hi Paul

My model 1.2m long with a displacement of near 26Kg uses 2X 6V 12aHr SLA batteries. These are connected in series to give a 12V power supply. As well as providing propulsion, they are used for lighting, sound unit, smoke generator, radar drive and of course radio (via BEC). I usually need to stop sailing when the TX battery goes down.

Using 2 batteries allows me to site the batteries either side to help with stability, and 12V means less current, hence less heating. (Note Ashley's post). If you select your system volts from the start then work to that there should be no problems.

Good luck with your model, post some pic's

cheers Tom

[steve hParticipant @steveh76883]

Hello Paul, I bought my 6v 12amp batteries from a fishing bait boat company on ebay, £17each and they had tamya connectors soldered on already. Steve.

[steve hParticipant @steveh76883]

Hello again paul, my batteries are up for sale if your interested. Used them once for a quick test sail, they are 6v 12amp.

[Dave MilbournParticipant @davemilbourn48782]

Steve
You may be disappointed by the response; Component Shop sell the same batteries for £12.95.
Dave M

[steve hParticipant @steveh76883]

Bugger. cant use em now anyway , too heavy. steve.

[Colin BishopModerator @colinbishop34627]

I find gel cells come in useful as a general power source in the workshop when you are testing things etc. Once you have charged them they will hold their charge for two or three months. I have sometimes used mine with bulbs as a lighting source during power cuts.

Colin

[steve hParticipant @steveh76883]

Good idea, saves draining my bike battery when im tinkering. steve.

[Author]

Posts