Putting Christmas lights on our boat for the first time, looking for suggestions pls

[tazmajazz]

Hello! I have gathered quite a bit of info on this topic but I would like some advice from someone that has experience decorating their boat. I know the lights that I want to use and I know how to add up the amps or watts and determine the watt or amp power that is needed to power the lights for X amount of time, however I'm not sure if the boat's electrical system has any limitations other than the battery power that I need to be aware of.

I am thinking of two options. One would be to buy a portable 600w/28aH power pack that I estimate will let me run my lights for about 7 hours. the other option would be to buy two DC/AC inverters that would plug into my two 12v outlets on the boat and give me two outlets each for a total of four. I haven't checked my current battery capacity yet but I have two starting batteries hooked up and am willing to purchase a deep cycle if necessary since I know that will be enough juice to run everything, however are there any limitations to a boat's electrical system besides the amount of power the batteries themselves can provide? Am I going to blow fuses if I try to run these lights through the 12V outlets using power inverters? Keep in mind, my b oat is a 20ft boat and I'm not looking to light an absurd amount of lights or anything but I calculate it should e around a 477.6w or 3.98a power draw.

I've never done this before and would really like some suggestions or advice. Thanks!

taz

 

[26aftcab454]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

use LED lights--go with the powe inverters--
alsp try NOT to use extention cords.
POST A PICTURE!

 

[Silvertip]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

Remember -- the alternator and batteries are limited as to what they can accomplish. Whatever you suck out of the batteries must be replaced by the alternator. Also understand that an inverter is only 85% or so efficient so you lose 15% right off the top. Also remember that an inverter operates with a factor of 10 difference in power going in vs power going out (12 volts in/120 volts out). That factor of 10 means the input side of the inverter must be capable of handing the current load which I doubt your accessory sockets can handle, nor the fuses that protect them. So: you are pulling just shy of 4 amps on the output side of the inverter. That means you need 40 amps of 12 volt DC on the input side, plus another 15% for the losses in the inverter. Think your accessory outlet can handle that? Then you have 40 amps/hour of operation so 7 hours of operation would suck 280+ amps from the batteries. While you have enough battery power with two or three deep cycles, y0u do not have the wiring for it. The inverter would need to be hard wired to the battery bank using a minimum of 10 gauge wire and that would be right on the threshold of being too small so #8 would be preferred. There is no free lunch with inverters -- meaning if all it took was an inverter and there were no losses and conversion factors involved, we might all have coffee pots, refrigerators, 50 inch TV's and air conditioners on our boats regardless how big or small they are. Unfortunately big power users require big (really big) inverters and insanely big battery banks as well as equally big on-board chargers and engine alternators. What you want to do will work, you just need a properly sized inverter and properly sized, fused, and wired 12 volt circuits. The real solution to cut the power requirements is to use the newer LED light strings as suggested. Much less current draw.

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

hmm, not sure what the amp rating is on the accessory outlets. I checked the manual and it did not say. What if I got a deep cycle battery and a 400w inverter that I alligator clip directly to the battery and run everything off that? Actually, I could get two 400w inverters and wire them both to the deep cycle...would that work better? Thanks for the info!

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

or even better, I could get one of these guys and then connect two power strips?

http://www.amazon.com/Power-Bright-...G2FG/ref=sr_1_2?ie=UTF8&qid=1324247907&sr=8-2

 

[Bondo]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

I'm not looking to light an absurd amount of lights or anything but I calculate it should e around a 477.6w or 3.98a power draw.

or even better, I could get one of these guys and then connect two power strips?

http://www.amazon.com/Power-Bright-...G2FG/ref=sr_1_2?ie=UTF8&qid=1324247907&sr=8-2

Ayuh,... That'll work til the battery goes dead....

Just how long do ya plan on runnin' 'em anyways,..??

Check the size of the fuse for the accessory outlets, 'n then you'll know their limits...

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

Ayuh,... That'll work til the battery goes dead....

Just how long do ya plan on runnin' 'em anyways,..??

to be honest I'm not sure. We're participating in a boat parade which we have never done before so I we just need them to work as long as we are in the parade, maybe a couple of hours? I'm thinking an Optima D27M with this inverter http://www.amazon.com/Power-Bright-P...4247907&sr=8-2 and two power strips should suit my needs. Actually if we replace most of the strips with LED lights AND get the Optima battery, we would probably be fine with just a 400W converter since LEDs take so much less power...thoughts?

 

[Silvertip]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

Again, I'm not concerned with the "output" and with LEDs 400 watts should be a big enough inverter. You need to pay attention to not just the connection to the battery but the size of the wires going from it to the inverter. Fuses are there to protect the wire - not the device the circuit feeds. Until you are absolutely certain what the current draw is going to be we cannot provide positive information. Light strings have either an "amperage" or a "wattage" rating listed on the tag. Add those numbers and that's how big the inverter needs to be PLUS 15%. Whatever that number turns out to be multiply by 10 and that's what the "input" circuit must be capable of handling. If you use a deep cycle battery, look at it's label for the RC (reserve capacity). That number is usually specified as xxx minutes @ 23 amps. What that means is the battery can provide 23 amps for xxx minutes before it can no longer do so.When making that run-time calculation you use the inverter INPUT amperage, not the OUTPUT amperage. You don't need a bunch of power strips. The set of LED lights I put on my deck indicated I could connect 60 strings end to end (provided the strings were identical).

 

[fucawi]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

you worry me sometimes Silvertip..
..Also remember that an inverter operates with a factor of 10 difference in power going in vs power going out

Oh so thats how you get 85 % efficiency ?? ha ha .....since when was power measured in volts????

 

[series60]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

12 volt led rope lights do a very nice job. Christmas led lights come in 12 volts also. Truck drivers use them all the time. Look at large truck stop for Christmas lights.

 

[Silvertip]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

How helpful that was! While using the term "power" (as in P in Ohm's law) rather than voltage (as in E in Ohms law) perhaps confused you, here is visual proof of what I related in the above post. This example shows a standard 75 Watt, 120 volt bulb being powered from a Cobra 800 Watt inverter, which in turn receives 12.6 volts input via a garden tractor battery. An ammeter is inserted in the positive lead between the battery and the inverter. As the picture shows, the meter is reading 6.5 Amps (DC) input. The 75 Watt bulb draws draws .625 Amps. So: to get .625 amps of 120 Volts AC out of the inverter you need to put 6.5 amps of DC into it. By golly .625 into 6.5 is a factor of 10.4 using AMPS in this case is it not? It is also a factor of 10 if you use VOLTAGE as an example. You can run the efficiency numbers yourself I'm sure.

And the inverter being used:

 

[Bondo]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

to be honest I'm not sure. We're participating in a boat parade which we have never done before so I we just need them to work as long as we are in the parade, maybe a couple of hours? I'm thinking an Optima D27M with this inverter http://www.amazon.com/Power-Bright-P...4247907&sr=8-2 and two power strips should suit my needs. Actually if we replace most of the strips with LED lights AND get the Optima battery, we would probably be fine with just a 400W converter since LEDs take so much less power...thoughts?

Ayuh,... I think yer Over-Thinkin' it....

Yer talkin' 4 amps, Right,..??
Yer boat is gonna have it's motor runnin' during this parade, Right,..??
What is this motor,..??
Does it have a Starting battery,..??

Check the amperage of the fuses for yer accessory outlets....
If those fuses are of a Higher amp rating than the draw of yer inverters,...
Plug 'em in, 'n run yer lights for yer parade...

Or, take Bubba's idea, 'n use 12v lights...
Either way, unless you've got a tiny outboard, the existing battery, 'n charging system will power what ya got goin' on,...
No Problem......

This Ain't rocket science....:facepalm:

 

[fucawi]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

most mains led fairy lights are based on a 24v AC transformer and powers 5 to 10 w so little load for even a 300w inverter..or as suggested 12v lights..use what you have its only for a couple of hours ..borrow a spare battery off the wifes car !!!

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

ok well my wife already bought LED 120v lights so we will have three strands of those (33ft each) and then we have two lighted figures made out of regular bulbs. I added up the amperage of everything and it is 1.991 amps which should translate to 238.92 watts (1.991a * 120v). So I should be ok with the 400w inverter. Also, I'm looking at getting an AGM battery rated at 79 amp hours which means that I should be able to sustain that load for 39.67 hours (79ah / 1.991a).

sounds good to me, am I missing anything?

thanks for all the replies!

 

[kmarine]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

As an expierienced vinetian night boat captin withh a couple of awards I have practical knowledge that may help. with a 400 watt inverter at appx 300 watt load a 27 series deep cycle battery lasts about 1.5 hours. This can be extended if you attach cables to your boats main battery and charging system . My boat has a 90 amp alternator. I recomend not using clips due to possible power loss from weak connections, and heat creation. What type of boat engine do you have. I personally would not do it with an outboard motor. I also now have a small honda generator on the swim platform for my ski boat which sits on top of a crate for extra clearance from water( inverter was not powerfull enough for my last contest).

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

I have a yamaha 150hp outboard I was actually wanting to keep the lights and the goat's electrical system separate. Can you tell me where I was off in my calculations? How does a 2 amp load on a 79ah battery only last 1.5 hours?

What do you suggest for the connection besides clips?

thanks!

 

[Silvertip]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

I have a yamaha 150hp outboard I was actually wanting to keep the lights and the goat's electrical system separate. Can you tell me where I was off in my calculations? How does a 2 amp load on a 79ah battery only last 1.5 hours?

What do you suggest for the connection besides clips?

thanks!

I suggest you go back and look at the picture and the description I presented using a 120 volt/75 watt light bulb, a 12 volt battery, and and 800 watt inverter. You are indeed missing the fact that whatever current you draw at 120 volts OUT of the inverter means you need to put 10 times that amount current at 12 volts INTO the inverter.

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

I apologize if I haven't followed everything. I understand much better now after everyone's replies. I believe my confusion was in the different calculations between the input voltage @ 12V and the output voltage at 120V.

so...I think I have a better understanding now. The lights will draw about 240w of power from the inverter and at 120v, that is about 2 amps of current. However, the battery needs to supply the inverter 240w which at 12v is 20amps current. So if I am using a 79AH battery, at 20 amps current, it will last aprox. 3.95 hours.

however, according to silvertip, the inverter will only be 85% efficient so the battery will REALLY need to supply 23 amps to the inverter (20 * 15%) to enable it to supply the 2amp current to the lights, so that means that a 79ah battery will last aprox. 3.43 hours.

Does that sound better?

thanks again folks

 

[tazmajazz]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

thanks silvertip, I think I understand that correctly now. See my last post. do those calculations look correct?

 

[Silvertip]

Re: Putting Christmas lights on our boat for the first time, looking for suggestions

You got it! 85% efficiency is a rough number and it may be as high as 90%. When doing conversions up or down using electronics, losses are always involved. But I think your inverter will kick out long before that. It depends on what the "low voltage" limit is for your particular inverter.