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Author Topic: Lead Acid Batteries.  (Read 755 times)

ojays

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Lead Acid Batteries.
« on: April 08, 2019, 03:07:48 PM »

I recently acquired a 60" HMS Cornwall model that is unfinished, and am looking for suggestions with regard to using a lead acid battery.
All my past builds I have used NIHM's because of weight/size considerations.

This is my first with such a large model and am unsure of what mah I should be looking for.
She has 2 X 6 volt 480/500 size motors already fitted, and the props are scale 35mm.

I do know that I yet have to ballast her, as she rides way too high, so the battery will be part of her ballast.

Looking for suggestions from more experienced builders please.

Thanks in advance.
Gregg
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unbuiltnautilus

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Re: Lead Acid Batteries.
« Reply #1 on: April 08, 2019, 08:02:30 PM »

I would suggest a pair of 6v 4.5amp gel batteries.They should be small enough to fit through your hatches.Also two batteries gives you flexibility in placement of the cells for fore and aft trim. You could also run port and starboard motors on two different batteries and speed controls for independent throttle control. Might be useful on smaller waters.
Keep 'em right on the bottom of the boat though!!
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Buccaneer

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Re: Lead Acid Batteries.
« Reply #2 on: April 08, 2019, 08:16:12 PM »

Beautiful looking model! As ubn says make sure the batteries fit. Component Shop Website has all the dimensions and weight, very useful.
John
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ojays

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Re: Lead Acid Batteries.
« Reply #3 on: April 08, 2019, 08:27:55 PM »

Wow, thanks for the prompt responses.
I'm also awaiting feedback from the original builder.

Thanks guys.
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gingyer

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Re: Lead Acid Batteries.
« Reply #4 on: April 08, 2019, 10:24:56 PM »

Can I suggest putting in something (wee bags of sand) and check the weight before buying any batteries.


I only needed 2x 6volt 12Ah batteries and a small bit of lead to ballast my 1:72scale version.
I would perhaps work out how much weight you need and also the size you can fit in before buying anything.


as said before, lay the batteries as low down as you can and the model will be pretty stable  :-))
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Colin Bishop

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Re: Lead Acid Batteries.
« Reply #5 on: April 08, 2019, 11:02:51 PM »

Also bear in mind that if you lie an SLA battery on it's side the 'bottom' end will usually be heavier than the 'top' end. The weight is not evenly distributed!
Colin
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unbuiltnautilus

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Re: Lead Acid Batteries.
« Reply #6 on: April 09, 2019, 07:31:39 AM »

Also bear in mind that if you lie an SLA battery on it's side the 'bottom' end will usually be heavier than the 'top' end. The weight is not evenly distributed!
Colin


A very good point often forgotten. The top of most gel batteries,down to a depth of about 10mm, is mostly fresh air! This is why a 6v 10amp laid down on its side in the Type 22 would need trimming weights to compensate for the weight of the battery being off to one side. The 6v 4amps suggested will only lay down fore and aft ( don't stand them up!! ), but you could change their orientation fore and aft, to effect slight trim changes if needed.
On a related point,the model will still need lead, right down in the bilges, and to be honest,if it was me,I would use one or two 5000mAh NiMhs,rather than gel batteries. This will allow you to get all the weight right down in the bottom of the model. You want stability to be front and centre your main priority with a long skinny, high freeboard model like this. Better to get the best performance possible, than be watching the weather before a sailing session, in case it is too breezy!
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malcolmfrary

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Re: Lead Acid Batteries.
« Reply #7 on: April 09, 2019, 08:51:32 AM »

Since the OP is well used to NiMH, I would just use them and add lead ballast in the bottom of the hull.  A shallow draught but tall model like this is going to be tender and needs all the help it can get lowering the center of gravity.
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ojays

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Re: Lead Acid Batteries.
« Reply #8 on: April 09, 2019, 11:28:49 AM »

Many thanks again for all your input.
I have had a response from the original builder who had done a ballast test prior to me acquiring her.
He hasn't stated what size battery he used, although he did say she was well ballasted with extra lead low down.

I'm now going to carry out my own tests to see what's needed.
He did say that all the superstructure is made from thin plasticard, so I would imagine there wouldn't be too much
topside weight. (hopefully).

I will let you know how I get on.

Regards
Gregg

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Onetenor

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Re: Lead Acid Batteries.
« Reply #9 on: May 09, 2019, 05:10:38 PM »

You may find some Motor Cycle/Scooter batteries that will fit, Some are a gel type and sizes and shapes vary a lot.You should find one to suit. Gel type are more evenly balanced too.Good luck John
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ojays

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Re: Lead Acid Batteries.
« Reply #10 on: May 09, 2019, 08:13:48 PM »

Many thanks for all the advice.
I have been in touch again with the original builder, and found out he used a 2500mah 7.4 NiMh when checking out the ballasting.
Going to go down this road and see how it goes, just need some decent weather.
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