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Author Topic: What battery capacity do I need?  (Read 2435 times)

NFMike

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What battery capacity do I need?
« on: August 12, 2012, 11:25:17 pm »

For my first boat I'm building a Model Slipway Aziz. Twin screw (in case you didn't know) and using a pair of MFA 540 brushed motors with 6:1 gearing. I will be using 12V nominal for the electrics, probably with ACTion electronics, and having read all the debates about NiMH/NiCd, Lipo, etc, I think I'll stick with SLA for the battery(s).

But what sort of Ah capacity battery should I be looking for?
Obviously doing some bath tests would be ideal, but to do that I'd need a battery ....
So, as I'm sure plenty of others have built this or similar kits with these motors, I'm hoping to milk your collective brain for the information.

Peter Fitness

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Re: What battery capacity do I need?
« Reply #1 on: August 12, 2012, 11:36:20 pm »

My answer to your question would be, the bigger the better. I haven't built an Aziz, but it seems to have quite a big hull which would allow you to fit a fairly big battery. It also seems likely that you would need ballast, so using a bigger battery would solve two problems - ballast to bring the boat down to its waterline, and running endurance. There are a number of members who have built Aziz, and they may have some ideas for you.

Peter.
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john s 2

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Re: What battery capacity do I need?
« Reply #2 on: August 13, 2012, 08:56:19 am »

A pair of 12v 7 amp hr batterys should be fine and help to cut down on Ballest. John.
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NFMike

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Re: What battery capacity do I need?
« Reply #3 on: August 13, 2012, 03:39:13 pm »

A pair of 12v 7 amp hr batterys should be fine and help to cut down on Ballest. John.
I have several kilos of lead flashing by my left elbow, so ballast is not a problem :)
So 14Ah is a likely figure? 7A per motor for one hour ... does that sound about right?
I don't really want to parallel connect high capacity batteries unless its essential - I feel its a path to problems.

Netleyned

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Re: What battery capacity do I need?
« Reply #4 on: August 13, 2012, 04:35:37 pm »

Lead flashing does not run a motor
Just gives weight that has to be propelled through the water.
A bigger battery or two gives weight and thrust

Ned
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NFMike

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Re: What battery capacity do I need?
« Reply #5 on: August 13, 2012, 05:18:57 pm »

Lead flashing does not run a motor
Just gives weight that has to be propelled through the water.
A bigger battery or two gives weight and thrust

Ned
True. However, I'm unlikely to need more than an hour, maybe two, of running time at 'pootle' speeds. As I already have plenty of already paid for lead to hand there is no point in me spending extra money on excess battery capacity.

NFMike

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Re: What battery capacity do I need?
« Reply #6 on: August 13, 2012, 05:34:10 pm »

I'll also need to source a battery and charger. I thought I saw a recommended supplier on here a little while back but of course I can't find it now.
Any recommendations, or avoids (subject to not being sued of course).

Netleyned

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Re: What battery capacity do I need?
« Reply #7 on: August 13, 2012, 05:40:37 pm »

You wont go wrong with the guys at www.componentshop.co.uk
No bad words about these guys

Ned
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Gazza

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Re: What battery capacity do I need?
« Reply #8 on: May 26, 2013, 07:15:59 pm »

its all down to Mah  or Ah  the bigger the number the longer the run time
 
so a 2200mah Li-Po say lasts 20 minutes then a 4000 will last 40 minutes type of thing
so bigger is better in run time but longer on the charger
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