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08-02-2013, 11:51
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#1
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Registered User
Join Date: Nov 2012
Location: panacea, florida
Boat: morgan 41 sloop
Posts: 43
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48v 36v 24v and 12v system
i dont understand the point of having anything but 12 volt on a boat.... all motor and appliances i have seen are 12 volt. what is the purpose of wiring batteries and having chargers in 24 volt or higher? what possible electrical devices could i use that isn't 12 volt?
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08-02-2013, 12:11
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#2
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Registered User
Join Date: Aug 2011
Location: Petersburg, AK
Boat: Outremer 50S
Posts: 4,229
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Re: 48v 36v 24v and 12v system
Quote:
Originally Posted by drousy88
what possible electrical devices could i use that isn't 12 volt?
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Just about anything. The amount of power available is a function of voltage times current. So, at 24V all other things being equal, the same equipment will use half the current. For instance, a windlass that draws 100A at 12V will draw 50A at 24V and 25A at 48V (if they all have the same power rating).
The required wire/cable size is a function of current, nothing else, so higher voltage systems can have smaller wires, lowering installation costs (especially with copper as valuable as it currently is).
Most boat items are available in 24V, but may cost you more because they are not derived from the mass-production automobile 12V market. However, as accessory power usage goes up even some autos are moving toward higher voltages.
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08-02-2013, 13:09
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#3
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Registered User
Join Date: Feb 2011
Location: Northern and Southern California
Boat: too many
Posts: 3,731
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Re: 48v 36v 24v and 12v system
During the war, US auto makers went from 6 volts to 12 to save copper for the reasons Dsanduril gave, 1/2 the current for the same work (watts) done. On my next boat I will go to 48 volts for the inverter house bank also for that same reason.
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08-02-2013, 13:09
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#4
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Registered User
Join Date: Dec 2006
Location: Seattle
Boat: Cal 40 (sold). Still have a Hobie 20
Posts: 2,944
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Re: 48v 36v 24v and 12v system
If you double the voltage you half the current as stated above, so you can reduce wire size by 3 AWG for the same voltage drop in the wire.
100 amp windlass at 12 V with a 40 foot round trip for the wire with a 10% voltage drop needs a 4 AWG wire. At 48 volts that becomes a 10 AWG wire.
Do much high current wiring in your boat and it adds up. Windlass, 2000 watt inverter, etc.
Rule of thumb change size of wire by 3 AWG and you half or double the resistance. 10 AWG is 1 ohm per 1000 ft.
or
American wire gauge - Wikipedia, the free encyclopedia
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08-02-2013, 13:14
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#5
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: 48v 36v 24v and 12v system
Quote:
i dont understand the point of having anything but 12 volt on a boat.... all motor and appliances i have seen are 12 volt. what is the purpose of wiring batteries and having chargers in 24 volt or higher? what possible electrical devices could i use that isn't 12 volt?
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most industrial stuff is 24v dc
__________________
Interested in smart boat technology, networking and all things tech
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08-02-2013, 13:31
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#6
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Registered User
Join Date: Nov 2012
Location: panacea, florida
Boat: morgan 41 sloop
Posts: 43
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Re: 48v 36v 24v and 12v system
you use less amps at 48v but it also makes your battery bank have less amp hours. i.e. if i have 8x 6volt 225ah batteries wired to 12 volt i have a battery bank of 900ah. if i were to wire them at 48 volt then my battery bank would only have 225ah.......right?
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08-02-2013, 13:35
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#7
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Registered User
Join Date: Aug 2009
Location: oriental
Boat: crowther trimaran 33
Posts: 4,414
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Re: 48v 36v 24v and 12v system
Higher voltage is a good thing because:
1. lighter gauge wire
2. higher efficiency appliances
3. it allows you to put your batteries in series as too many in parallel has a chance of complete meltdown if one of the battery cells fails shorted and allows the other batterys to discharge thru it.
with that said I used 12 volt with 4 batteries in parallel... I am basically limited by my solar setup. In the future I would look for higher voltage panels, or several smaller ones in series that will be mounted on exact same angle next to each other as series panels do poorly in partial shade
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08-02-2013, 13:40
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#8
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Registered User
Join Date: Oct 2010
Location: Marathon, FL
Boat: Hans Christian 33
Posts: 652
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Re: 48v 36v 24v and 12v system
Wasn't this the argument of Tesla versus Edison in which case I think Tesla should have won but was out maneuvered by Edison?
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08-02-2013, 13:45
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#9
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Registered User
Join Date: Dec 2012
Location: New Orleans
Boat: Bruce Roberts 44 Ofshore
Posts: 2,841
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Re: 48v 36v 24v and 12v system
Most small boat electric propulsion systems are 48 volts sothere are quite a few chargers, inverters, and dcdc converters for 48v. There are also a lot of electrical appliances for 36v because most older fishing boats have 36vdc electrical systems so there are cheap heavy duty fans, reefers, etc for that voltage. A lot of high current elecrronics such as radars are 24vdc. One of my near future projects is to go 48v for my house bank because eventually when my atomic gives up the ghost i will probably go electric oe diesel electric hybrid drive. I would go 72 or 144v if inverters and chargers were cheaper. Inverters have gotten much more efficient and AC household and industrial appliances are cheaper than 12v and last longer. So I am running out of reasons to prefer a 12v bank. I dont know of any 48v starter for rhe atomic so I will keep a group 29 batt just for starting.
The reasons for higher voltages are already well stated above, as are the reasons for 12v so I wont restate the obvious but these days 48v is looking more attractive to me.
__________________
GrowleyMonster
1979 Bruce Roberts Offshore 44, BRUTE FORCE
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08-02-2013, 14:00
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#10
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Registered User
Join Date: Dec 2012
Location: New Orleans
Boat: Bruce Roberts 44 Ofshore
Posts: 2,841
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Re: 48v 36v 24v and 12v system
Quote:
Originally Posted by drousy88
you use less amps at 48v but it also makes your battery bank have less amp hours. i.e. if i have 8x 6volt 225ah batteries wired to 12 volt i have a battery bank of 900ah. if i were to wire them at 48 volt then my battery bank would only have 225ah.......right?
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Yes. So? 1/4 the current at 4x the voltage is the same amount of energy and accomplishes the same amount of work.
__________________
GrowleyMonster
1979 Bruce Roberts Offshore 44, BRUTE FORCE
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08-02-2013, 14:20
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#11
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Registered User
Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 20,420
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Re: 48v 36v 24v and 12v system
Yes, but the wires are finer, lighter and cheaper. Big factor in any big boat.
b.
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08-02-2013, 15:02
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#12
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Registered User
Join Date: Dec 2006
Location: Seattle
Boat: Cal 40 (sold). Still have a Hobie 20
Posts: 2,944
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Re: 48v 36v 24v and 12v system
Quote:
Originally Posted by drousy88
you use less amps at 48v but it also makes your battery bank have less amp hours. i.e. if i have 8x 6volt 225ah batteries wired to 12 volt i have a battery bank of 900ah. if i were to wire them at 48 volt then my battery bank would only have 225ah.......right?
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More detail than the last post, but basically the same info.
Power is what you use to accomplish the task. Power = voltage times current.
A 12 volt windlass that draws 100 amps consumes 1200 watts of power.
To be able to pull up the same size anchor at the same rate with a different windlass would require it to use 1200 watts of power.
48 volts x 25 amps = 1200 watts.
You can only compare amp-hrs for the same voltage. If you are going to compare different voltages you want to look at your battery capacity in watt-hours.
900 amp-hrs times 12 volts is 10800 watt-hrs
225 amp-hrs times 48 volts is 10800 watt-hrs.
The amount of work you're able to do is the same.
power is work/time.
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08-02-2013, 17:00
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#13
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Registered User
Join Date: Nov 2012
Location: panacea, florida
Boat: morgan 41 sloop
Posts: 43
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Re: 48v 36v 24v and 12v system
Quote:
Originally Posted by cal40john
More detail than the last post, but basically the same info.
Power is what you use to accomplish the task. Power = voltage times current.
A 12 volt windlass that draws 100 amps consumes 1200 watts of power.
To be able to pull up the same size anchor at the same rate with a different windlass would require it to use 1200 watts of power.
48 volts x 25 amps = 1200 watts.
You can only compare amp-hrs for the same voltage. If you are going to compare different voltages you want to look at your battery capacity in watt-hours.
900 amp-hrs times 12 volts is 10800 watt-hrs
225 amp-hrs times 48 volts is 10800 watt-hrs.
The amount of work you're able to do is the same.
power is work/time.
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i understand now, so what's the safest daily discharge out of my 900 ah bank?
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08-02-2013, 17:14
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#14
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Re: 48v 36v 24v and 12v system
Quote:
Originally Posted by drousy88
you use less amps at 48v but it also makes your battery bank have less amp hours. i.e. if i have 8x 6volt 225ah batteries wired to 12 volt i have a battery bank of 900ah. if i were to wire them at 48 volt then my battery bank would only have 225ah.......right?
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What matters are the total number of watt-hours that can be stored. Comparing amp-hours is fine as long as you are also comparing the same voltage. This way you are comparing apples to apples.
__________________
David
Life begins where land ends.
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08-02-2013, 18:12
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#15
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Marine Service Provider
Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,974
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Re: 48v 36v 24v and 12v system
The one issue with drawing down batteries is that lead acid prefer to be discharged slowly, particularly with the deep cycles we use on boats. This does result in an efficiency gain, so by drawing 6 amps at 24v you do actually get more usable power from the same batteries than if you draw 12amps at 12v.
__________________
Greg
- If animals weren't meant to be eaten then they wouldn't be made of food.
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