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Author Topic: 12v 20ah SLA?  (Read 1458 times)

tizdaz

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12v 20ah SLA?
« on: November 10, 2016, 02:34:49 PM »

Hi guys,


im thinking of using 2 of these in series: http://www.componentshop.co.uk/12v-20ah-sealed-lead-acid-battery.html 20ah-sealed-lead-acid-battery.html for my drive system (which is a 24-volt motor) & a 3rd battery for all the other electrics such as lights/sound/steam unit etc.


They are rated at 20ah, they weigh 7kg each so the weight will be 21kg in total which will help alot with the ballast for my 1/12 scale tug, as during transport i will remove the batterys.


I was under the understanding that the higher the Ah, then the higher the capacity (longer run times). Which is why i'm confused as some modules i have been looking at (such as sound or smoke) some state that the power source must not exceed 5ah, why is this as i thought Ah is just for the capacity!?


Also if a module requires 6-volt volt, how would i step the voltage down from 12-volt, would i just need a simple distribution board that will have a set number of different voltage outlets? If so any recommendations?


Thanks :)

g6swj

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Re: 12v 20ah SLA?
« Reply #1 on: November 10, 2016, 05:36:58 PM »

Tizdaz,

Looks like you are making progress with your plans for your tug.

What brand/product states "must not exceed 5ah"?

Re dropping 12v to 6volt - save yourself a lot of pain if you use a 6 volt battery

Regards
Jonathan
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malcolmfrary

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Re: 12v 20ah SLA?
« Reply #2 on: November 10, 2016, 06:19:58 PM »

I have seen plenty of circuits which plug into receivers that have a maximum voltage limit of 5-and-a-bit.  This is usually because the I/Cs used in them have that as their maximum.  So, other than either a misprint or misread, no reason at all for a 5ah maximum.
While there is a good range of voltage reduction circuits out there, using the right voltage battery is much simpler, and helps make sure that the only thing giving smoke out is the smoke unit.
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tizdaz

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Re: 12v 20ah SLA?
« Reply #3 on: November 10, 2016, 07:24:47 PM »

Hiya guys,


Yup im just getting a list together of all the kit i need to buy so when i get my hull in few weeks i can get started, im pretty much there now with all the gear i want just going over the list and double/tripple checking etc! :-)


The device thats states 5ah max was the mist module from here http://www.modelboatbits.com/MIST-UNIT


But its all good as ive decided to go for this unit: http://www.steammasterunit.com/ its more expensive, but has more running options to give desired effect.


Will take all your advice regarding batterys and scrap the idea of a step down and just use the correct voltage battery for that device. So im guessing im going to have:
3x 12-volt (2 for the drive and 1 for the 12v modules etc)
1x 6-volt (for 6v modules etc)


So altogether im going to have 42volts floating around the lake!


Ive also just found out that the hull is actually large enough to fit a normal 12v car battery in it! But im going to use the setup of gel cells as i can place them around hull for ballast.


Quick question, what voltage are the leds used for deck and wheelhouse lighting etc?


Cheers guys/gals! :-)

Stavros

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Re: 12v 20ah SLA?
« Reply #4 on: November 10, 2016, 09:35:00 PM »

Told you so ref 12 car batts !!!!!!!.......get your Led's form Component shop but TELL THEM you are running 12v and they will supply you with the  correct resistors




Dave
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tizdaz

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Re: 12v 20ah SLA?
« Reply #5 on: November 10, 2016, 09:45:49 PM »

Oki doke thanks :-)

NFMike

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Re: 12v 20ah SLA?
« Reply #6 on: November 10, 2016, 10:12:01 PM »

The device thats states 5ah max was the mist module from here http://www.modelboatbits.com/MIST-UNIT
Um. The instructions for that 12V unit start talking about 24V a bit further down  :o  .


As to the 5ah (which should be 5Ah) it's a fact of modern life that using terminology, and indeed general language, in a way that is clear has pretty much gone out the window ... "I like the sound of that word - I'll use it in my next sentence" seems to be the thinking.


Technically there could be a reason for specifying a maximum Ah rating. In general the larger the battery the higher the current it can deliver. This means that in the event of a fault a bigger battery can supply more power thus ensuring greater destruction (in power distribution terminology it's the Prospective Short Circuit Current). So perhaps the 5Ah limit is to ensure that should you not fit a suitable fuse inline then a fault won't cause the unit to self-destruct in a dangerous manner.
(No, me neither.)

tizdaz

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Re: 12v 20ah SLA?
« Reply #7 on: November 10, 2016, 10:24:10 PM »

Hi plague,


Thanks for reply, aye the instructions for that device aint too clear, as you said, it says 12 volt and then further down it says upto 24 volt! And then the "Max Ah" etc, like i say im going to go with the other unit, more expensive yup, but it seems a better product and ive watched a few vids on youtube which im happy with :-)

JimG

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Re: 12v 20ah SLA?
« Reply #8 on: November 11, 2016, 09:55:39 AM »

Just as a guess there might be a simple reason for a maximum battery capacity. As the equipment in question is a mister this will contain a water tank to produce the mist. You are not supposed to run them dry so restricting the battery might ensure that it will not run long enough to empty the tank.

Jim
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malcolmfrary

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Re: 12v 20ah SLA?
« Reply #9 on: November 11, 2016, 04:48:53 PM »

Usually the unit has, or should have, a sensor that switches it off on low water.  Vastly more sensible than hoping the battery will run down before the water.  I do see a reason for a minimum value, but not a maximum.
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tizdaz

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Re: 12v 20ah SLA?
« Reply #10 on: November 11, 2016, 06:20:13 PM »

Aye its definately an odd one, i might drop him a mail to find out the reasoning.


Anyway thanks for the help guys :-)
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