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Old 05-03-2019, 09:36   #16
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Re: I'm running a 12v bilge pump on a 24v system

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Originally Posted by Valmika View Post
Wouldn't it draw less current?


More current because itís being run at higher than spec voltage.
But likely less amperage due to the higher voltage.
A 24V motor would draw half the amperage of a 12V of course, but running a 12V at 24V is running it harder than itís design, so more current than it should.
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Old 05-03-2019, 09:38   #17
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Re: I'm running a 12v bilge pump on a 24v system

just put a resistor, same as the resistance of the pump, in line (make sure it's rated for the current draw) This will reduce the power to 12v at the pump
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Old 05-03-2019, 10:12   #18
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Re: I'm running a 12v bilge pump on a 24v system

I think some people forgot Ohm’s Law. It would draw half the current (which is amperage) at 24v compared with 12v. The problem isn’t current but rather heat generation from motor winding speed.
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Old 05-03-2019, 10:33   #19
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Re: I'm running a 12v bilge pump on a 24v system

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But now I'm confused , lets say its 2 oclock in the morning and the correct 24v bilge pump has failed, I don't know why it failed , it was only 2 years old
I've found that 12v bilge pumps often die because of voltage drop. Your pump circuit may run from the batteries up to the bridge and back down to the engine room. You could have 20' of wire. Using a relay near the pump and fused power coming from near or at the battery might mean 5' of wire. The switch in the bridge would only be operating the relay.

I have a long wood boat that has 6 bilge areas. Pumps were only lasting a few years. I rewired them all with relays and haven't lost a pump since. And no I don't have thru the hull leaks. Pumping was after wash downs or hose/plumbing changes.
Back when I had 32v pumps this was never an issue. Pumps lasted decades.
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Old 05-03-2019, 11:47   #20
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Re: I'm running a 12v bilge pump on a 24v system

Assuming that your 24 volt system is made up of 2 x12 volt batteries in series and you wish to run a 12 volt pump , you can connect directly to the 12 volt battery that is the first from the ground or negative up. If you have a true 24 volt battery you will need a dc to dc converter of 24 to 12 volt these are fairly reasonably priced. Don't use a resistor which converts half the voltage to heat, that is an old school solution.
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Old 05-03-2019, 12:08   #21
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Re: I'm running a 12v bilge pump on a 24v system

I think there are some confusing bits of conflicting terminology being used in some of the replies.

Typically "Current" is the same as amperage. I would hate to see anyone get confused, and since we have members from different parts of the world we should be careful when it comes to electrical advise. Probably better to avoid "Current" and simply use Voltage and Amperage.

Just my Opinion, hopefully helpful!
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Old 05-03-2019, 13:25   #22
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Re: I'm running a 12v bilge pump on a 24v system

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Originally Posted by S/V Illusion View Post
I think some people forgot Ohm’s Law. It would draw half the current (which is amperage) at 24v compared with 12v. The problem isn’t current but rather heat generation from motor winding speed.
Thank you, thank you!!! That is exactly what I thought!

Voltage is measured in volts, current is measured in amps and resistance is measured in ohms. ... The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size. There is a basic equation in electrical engineering that states how the three terms relate. (sciencehowstuffworks)
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Old 05-03-2019, 15:31   #23
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Re: I'm running a 12v bilge pump on a 24v system

Responding to your post # 7
If a Storm was raging ect .
I assume you have multiple battery's I would try to hook just to a single battery (12v) so it would be more likely it would perform without premature failure and leave you with no pump .
Long term I would not connect to a single battery because of battery and charging issues.
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Old 05-03-2019, 16:03   #24
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Re: I'm running a 12v bilge pump on a 24v system

I don't think that it is a problem. Measure the amp draw with the pump on and pumping water. I think that it will draw less amps than it would at 12 volts, not quite half but much less. You should spend the the same amount of watts for a given amount of work. The pump rotor should only let it do so much work so would serve as a throttling device. If you throttle a pump it will produce high pitch whining but actually draw less juice. Just don't test it dry very often and it should be fine. Of course it would be nice to get some actual amperage figures at different voltages. If you get around to it let us know.
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Old 05-03-2019, 16:30   #25
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Re: I'm running a 12v bilge pump on a 24v system

12V winch @ 24V

"Just don't test it dry"(Thumbs up) = "What actually kills the motors is over revving. This usally occurs when winching cable out of load".

I LOVE READING THIS STUFF IT IS VERY FUNNY.
Reality............
All the top Aussie teams run 24v through 12v motors.
Most expect a life expectancy of somewhere around 18months to 2 years from there motors.
Tjhe difference is they service there motors regularly, blowing out the carbon dust etc...
There winching is very voilent and extremely hard. The reason they use 24 through 12 is that it is like Nitro charging your winch, it will pull like hell and never give in and at great speed.
What actually kills the motors is over revving. This usally occurs when winching cable out of load.
The Aussies have got over this by using free spool systems, however there are people that don't.
Paul Wightman has been running 12v Xp's with 24v going through them for over a year with no troubles and they are still has fit as the day he fitted them.
The only really usefull bit of info in this thread so far is the person that wrote "Flat batteries kill motors" this is correct.
Three of our Twins have just done the Rain forest challenge unfortunately all the teams had to be rescued and 50 cars left in jungle due to severe monsons and flooding, but those using 24 through 12 suffered no problems and were amazed at what they where having to pull through just to stay out of danger.
So there it is, Yes you can. But do remember to pulse the out button if you are paying out. If you want to see how quick they are i recommend watching the Alpine challenge 2007, where almost all the cars were using twin motor setups (either ours or Wazzas) resulting in 5 of the top 6 places for us and ALL including the rest of the top ten using 24 through 12.
Doing stuff that most would call impossible and almost ALL will never do.
Waiting for the fun to start
Jim
Sorry forgot to say.............
The motors do not get over hot doing this either, we have found that they stay cool to medium temp 125ft long pulls
However if the batteries get low.......The heat builds up very quickly.
I have run 24 through 12 myself many times, but i must tell you that i have destroyed motors by over revving them.
I however have NEVER destroyed one by over heating or burning out.
Jim

https://forums.lr4x4.com/topic/20463-12v-winch-24v/
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Old 05-03-2019, 17:35   #26
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Re: I'm running a 12v bilge pump on a 24v system

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Thank you, thank you!!! That is exactly what I thought!

Voltage is measured in volts, current is measured in amps and resistance is measured in ohms. ... The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size. There is a basic equation in electrical engineering that states how the three terms relate. (sciencehowstuffworks)
But the equation is V=IR. Voltage equals current times resistance. The pump has a constant resistance of its windings. Let's say R=1 ohm. Since the pump was designed for 12 volts it would have a designed current flow of 12 amps. Now if you hook it up to 24 volts you haven't changed R, so I = 24 amps. Your power dissipation (P=IV) has also gone up from 144 watts to 576 watts. All that extra power is heat, which becomes your problem.
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Old 05-03-2019, 19:20   #27
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Re: I'm running a 12v bilge pump on a 24v system

I can't believe all of the disinformation in replies to this thread.
There are a couple of accurate replies but most are filled with BS.
Get out your basic electrical books....E=IR.
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Old 05-03-2019, 21:28   #28
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Re: I'm running a 12v bilge pump on a 24v system

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Originally Posted by Quadrille in JB View Post
I can't believe all of the disinformation in replies to this thread.
There are a couple of accurate replies but most are filled with BS.
Get out your basic electrical books....E=IR.

I bet the experts are reading our posts and having a real chuckle!!
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Old 05-03-2019, 21:48   #29
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Re: I'm running a 12v bilge pump on a 24v system

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But the equation is V=IR. Voltage equals current times resistance. The pump has a constant resistance of its windings. Let's say R=1 ohm. Since the pump was designed for 12 volts it would have a designed current flow of 12 amps. Now if you hook it up to 24 volts you haven't changed R, so I = 24 amps. Your power dissipation (P=IV) has also gone up from 144 watts to 576 watts. All that extra power is heat, which becomes your problem.

Watts = Amps X Volts

To do the work of pumping let's say it takes 240 watts.

So with a 12V pump it will draw 20 Amp.

With 24V (and the same pump doing the same work) it will draw 10 Amps.

But in reality the pump will run faster on 24V and pump more water but to pump the same amount of water (as the 12V pump) it will be on for a shorter time.
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Old 05-03-2019, 21:59   #30
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Re: I'm running a 12v bilge pump on a 24v system

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Watts = Amps X Volts

To do the work of pumping let's say it takes 240 watts.

So with a 12V pump it will draw 20 Amp.

With 24V (and the same pump doing the same work) it will draw 10 Amps.

But in reality the pump will run faster on 24V and pump more water but to pump the same amount of water (as the 12V pump) it will be on for a shorter time.
Please explain how the internal resistance of the pump went from 0.6Ohms to 2.4Ohms?
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