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kms bismark

battery capacity and voltage

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chris fenerty11/03/2021 21:22:19
24 forum posts

hello everyone,

i have a major question concerning battery`s.

i need 12 volts and 5 volts, and i was considering using sealed led acid batteries, because LIPO`s have a bad reputation for blowing up.

if i need 12 volts for my motors, do i need a higher battery voltage, and how many A/hr would i need to have at least a hour worth of fun if not longer

ashley needham12/03/2021 09:03:02
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7318 forum posts
156 photos

Chris. Go for Nimh batteries, unless you HAVE an SLA ready to go. I only use Lipos when weight or size is an issue, ever had one blow up....with a bit of care they should not go that wrong. In addition they do not last as well as Nimhs. I might get two 6V batts and a series lead, If one pack goes, you can effectively replace just "half" of the 12v pack. It also gives you some 6v packs for other projects.

You will not be going fast with a battleship so the battery will likely last for hours. 4500mAhr size, oads of endurance.

The receiver is a handy source of 5v depend on the current drain. I have a few boats on which a spare rx channel powers led lights et.

Ashley

Malcolm Frary12/03/2021 09:43:17
1027 forum posts

The ESC will often have a BEC that eliminates he need for a separate supply for the radio itself and other items that plug into it.

As Ashley says, go for NiMH. A pair of 5 cell packs allows you to position them more easily than a Lead Acid lump. They are also much easier to look after than either SLA (need fairly constant attention to ensure long life) or Lithium which do have a charge cycle limit and very careful attention. Being lighter than SLA, you get to position the batteries where they are convenient to you. This allows you to position any ballast where you need it to be - preferably out at the ends to give a more realistic looking ride through waves.

What scale Bismark? I am assuming not a 1:350 one, since that size doesn't really lend itself to any SLA. Unless totally inappropriate motors are used, 4500mAH should give a very full afternoon's cruising.

chris fenerty12/03/2021 17:48:05
24 forum posts

hello everyone,

my model boat is approximately 2.75 mtr long, the 12v is for 3 main motor drive, stepper motors for turrets and guns,

as well as radar

5v for sensors, control processors, lights, and rc reciever.

should i use 18v with a voltage regulator to produce 12v, there is heat loss due to voltage drop x current.

i was considering 24v but i have found a new source for 6v batteries.

i was going to monitor the voltage and bring up a alarm, so i knew when to bring it back in.

the sealed lead acid batteries i was going to use three for 18v and parallel another three to increase my a/hr

and use them for ballast at the same time.

what do you gentleman think of that idea

ashley needham12/03/2021 22:37:15
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7318 forum posts
156 photos

It is a shame you did not appraise us with more particulars of the vessel initially as it is a tad larger than we were anticipating and suggestions so far run a bit short of the reality.

If the motors are 12v it seems pointless stepping down 18v to produce 12v especially as you have a source of presumably lead 6v batts.

How are you wiring the motors? Three esc...one for each, or are you going for a prop-steer arrangement? In any event the motors would be wired in parallel and not series so 12v is all you need. Run duration is dependant on the current consumed by the motors and the A/hr capacity of the batteries, and is usually a bit of a guesstimate in cases like this whereby there will be periods of manpower work, and loitering.

A voltage regulator could be used for the 5v supply.

Ashley

Dave Cooper 613/03/2021 10:37:05
305 forum posts
32 photos

Quite an ambitious project Chris.

I should look out for RC Swordfish torpedo attacks and rudders jamming !

Computer-controlled gunnery ? (There's a fascinating technical description of this on the internet. Sorry, couldn't find a suitable link for you just now).

I'm planning to use an "Arduino" for the turret on my RAF launch. In the 'C' program code you can select a random number generator and then get the chip's output pins to drive a stepper motor - fun to play with...

Good luck with the project,

Dave C

Malcolm Frary13/03/2021 11:24:30
1027 forum posts

For 12 volt motors, a 12 volt battery is the most efficient answer. A model that size could carry a much, much bigger battery than a 7AH one. A 1:96 Bismark, done as a full hull model rather than a shallow draft representation, will weigh about 112 pounds floating at waterline. Plenty of space for real, full size, car batteries if proper precautions regarding ventilation and acid proofing the battery compartment are made.

No point in using a higher voltage and regulating it down using a linear heat generator - UBEC regulators are available, but probably not easy to come by for the power levels needed. If odd items need higher voltages, circuits are available to step up voltage. Google for "step up voltage regulator".

A total of 15A needed for scale performance gives a theoretical 4 hours off a 70AH battery, probably a lot longer if cruising rather than escaping the attentions of the Home Fleet. A set of 3 of12v7AH batteries, one powering each ESC plus another to power the non-esc items, will work and give plenty of run time.

chris fenerty13/03/2021 19:12:51
24 forum posts

hi everyone,

i intend to use a4988 micro stepper for control of a hollow shaft stepper motor for moving my main gun turrets and the six 100mm guns along the side (3 each side), as well as radar and targeting array.

i chose hollow shaft so i could use a actuator to raise and the guns azimuth, the a4988 requires minimum 12v for controlling output but 5v for control signals, each gun requires 5 optical sensors i case a lose the step count, so i need three sensors for turret position - hard left, center, hard right. two sensors for gun movement - fully lowered, fully raised. the stepper motor only requires 2 inputs - direction and step.

although the boat is long, it is narrow and the hull height is less than 200mm, so i do not think i can get a car battery inside it.

i was going to use some arduino mega pro or nano v3, i was going to couple a potentiometer to the rudders control, so when i deemed that i was going hard to port or starboard, i would reverse the appropriate motor so i could turn quicker, i also thought of choreographing the gun controls as the data flow using lora between the boat and me would be incredible but i am still interested in trying that out.

hence my question about needing a higher voltage and regulating it so the stepper controllers have 12v

Colin Bishop13/03/2021 19:16:44
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Moderator
4966 forum posts
6089 photos
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The link referred to by Dave re using Arduino to control turrets etc. is here:

**LINK**

Colin

Malcolm Frary14/03/2021 09:27:57
1027 forum posts

i was going to use some arduino mega pro or nano v3, i was going to couple a potentiometer to the rudders control, so when i deemed that i was going hard to port or starboard, i would reverse the appropriate motor so i could turn quicker, i also thought of choreographing the gun controls as the data flow using lora between the boat and me would be incredible but i am still interested in trying that out.

Differential steering. Look for "Mixer". Either hardware in the boat between radio and ESC or done by the transmitter. Many transmitters do mixing. No point re-inventing something that is already on the market unless it is either going to work much better or cost a lot less, or both. Or do something extra that well established hardware cannot.

hence my question about needing a higher voltage and regulating it so the stepper controllers have 12v

5 volts will be needed, probably at very low current, for the control circuits. The control circuits will, if properly designed, be quite happy controlling any voltage. If a stepper motor control circuit requires the full motor voltage to provide the control signals, it comes down to a question of designing the right interface between the stepper control input and the arduino output.

 

Quick check of my car battery height - 175mm.  I didn't check the weight.

Edited By Malcolm Frary on 14/03/2021 09:40:05

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