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The plan is 2 65w solar panels,which should get plenty of sun in the Bahamas. I will be running an Edgestar fridge,some LED lights,a stereo sometimes,and occasionally a laptop computer for WiFi and a DVD once in a while. WiFi once or twice a week 10-15 min for Skype,and maybe a DVD once a week.
Will a laptop run on a 300w inverter without an issue,and how much power will a laptop draw typically? Does 130w of solar sound up to the task?

I have run my laptop on a $30 inverter on the new boat without a problem. There is some loss im sure. Not sure about the actual power drain. Unless you are running a server farm, I think you will be OK.

If it is windows, you can set it to run in low power (low performance) mode to further extend the power, at a cost of performance.

What type of batteries are you running (or will run on)? Our Mac has 2 high reserve Roll batteries that haven't let us down, even using them to make coffee using a home coffee maker off the inverter! Having the solar power is great, but having somewhere to store it is important too. Might be a good idea to upgrade/upsize the batteries before the trip

Paul,I have 2 group 27 deep cycle batteries. I considered adding a third,but there isn't much room,and I'm not sure the load requires it. I think the only real draw will be the laptop,as the LED's use nothing,and the fridge should run on half our solar capacity,as we won't be freezing with it.
I was thinking of carrying a 12v battery jumper pack,as a backup. Any idea is the battery pack can be charged by attaching the jumper cables to a house battery when the panels are working? Most packs come with a 110v charger,which I can't imagine using with a 300w inverter.

I wouldn't use the inverter if you can get an auto/air adapter for your notebook. That's what I have and can run my notebook off a standard 12v cig. lighter plug. Plus, I can use it on planes as well.

The inverter takes 12VDC to 110AC then you are taking 110AC back down to DC and probably 12v for the computer. The heat the inverter generates is waste.

Jumper pack is a good idea. It should stay charged for a long time unless you actually use it. When "jumping" you are basically connecting the two batteries together and I would think it should work in reverse. However, charging difference sized/types batteries isn't supposed to be wise and I don't know the reason why. I would just keep the jumper pack for emergencies.


--Russ

Any idea is the battery pack can be charged by attaching the jumper cables to a house battery when the panels are working?

No this wont work. Almost all the modern jumper packs are diode protected. You probably do have a 12 VDC connector which can be used for charging though.

My jumpstart packs I use came with 12v chargers as well as home 120v cable. If it is in the car/truck, it is always plugged in and (hopefully) charged up. My jumpstarter (going on 10 years old now) has no problem starting my v8 land rover or my chevy truck, so starting a pi$$ honda outboard will be nothing for it. Not a bad idea. The batteries in them are usually sealed, so should be pretty safe. Costco has a couple decent models for a good price. I used to carry it on the mac, no idea why I stopped carrying it.

Guess it will be trial and error with your batteries, fridge, etc. 2 27s might be fine if they are fresh and have high reserve capacity. The 2 rolls group 27s I have on the Mac are great.. but are going on 7 years, your batteries must be 5-6 years... so probably OK for the sailing we do with NE-TS. I would consider, if it were me, replacing them before going down. Might cost a $200 to replace them with a top quality fresh wet cell batteries, but might be worth the expense for piece of mind.

But agree with the others, running the laptop with a dedicated 12v adapter would be best (lowest power loss). I looked for a 12v adapter for my dell, and it was quite expensive, so I stuck with the inverter route with the 120v adapter

For all the major brands of laptops you can get a dual voltage power supply. These take either 110v AC or 12v DC as their input and convert it to the required voltage for the laptop.

This is what we provide all our uses with their Dell computers. It does 110 - 240 v AC, 12v DC and also has the special adapter for the power found at the seats in some airplanes.
http://accessories.us.dell.com/sna/prod ... u=310-8814

You can find similar products from all major laptop producers.

There are also many of these 3rd party products on the market
http://www.laptop-battery.org/Adapter/index.htm

All of these allow you to skip the AC inverter and it's losses and just make a simple DC to DC conversion.

The inverter will also work just fine.

In general most laptops run on 16v to 19 v power. You can easily tell by looking at your current power supply. It will be clearly marked with both input and output voltage. For instance, the laptop I am typing this on right now has an input rating of 110-240v at 1.2 amps and an output rating of 19v at 2.1 amps.

Voltage times amps equals watts, so if I were to plug this into an 110v inverter the maximum wattage it would draw is 110v x 1.2a = 132 watts. In reality it draws far less as it is only asked to produce 19v x 2.1a = 39 watts. There is loss in the conversion, but as you can see the load is still small. I have run every laptop I've owned (many different brands) without any issues on my 110v 150 watt inverter.

You should have no problem at all with a 300 watt inverter.

For the laptop I'm using I would expect it to draw around 60 watts with the conversion losses. From a 12v battery, 60 watts is 5 amps per hour of use.

You should work up a electrical budget in amp hours that accounts for all your electrical use in a day. It would look something like this

Edgestar Fridge, 4.0 amps at a 50% duty cycle = 24 hours x 4.0 amps x .50 = 48 amp hours
Lights, 1.0 amps x 5 hours = 5 amp hours
Stereo, 3.0 amps x 2 hours = 6 amp hours
Laptop, 5.0 amps x 2 hours = 10 amp hours
Pumps, 7 amps x 1/2 hour = 3.5 amp hours

For things not used every day come up with a daily average

Add them up, in this example, 72.5 amp hours x 12v = 870 watts a day.

You can expect a 120w solar panel to reasonably produce an average of 60 watts of 12v power for about 15 hours a day. This is 900 watts of power on average. In this example your budget is balanced. Now go plug in your own numbers and see what you get.

When calculating what your batteries can supply, take their amp hour rating, say 100 amp hours for a Group 27 battery, giving you 200 amp hours with the 2 batteries. You should never discharge a battery below 50% of it's capacity so that means you have a 100 amp hour supply in your batteries to supplement your solar production.

On batteries alone you have just over a 1 day supply of power, 72.5 amp hours needed and 100 amp hours available. Going two days on batteries alone would discharge the batteries too far and doing this often will damage them.

If when you do your budget you come up 10 - 20 amp hours short of your solar production you could reasonable expect to be able to supplement this from the batteries for 5 to 10 days before you need to charge from some source.

If you run your engine daily traveling take about 50% of it's rated alternator output in amps times the number of hours under way and add that into the equation.

You also want to be sure you have a proper sized charger on board. If you are going to pull into a dock in the afternoon, say 4 pm, and are 100 amps down in your battery bank, with a 5 amp charger you would need 20 hours plugged in to fill the bank. You better plan on staying at the dock two days. With a 12 amp charger (what we have on board) you could bring the batteries back to full in just over 8 hours. In reality it takes longer to refill than the simple math shows, but you get the idea. A small 5 amp charger means you are tethered to the dock for 2 days at a stop while a medium sized one lets you leave the next morning. If you add more batteries creating a bigger bank and a larger deficit when you arrive at the dock, you need a bigger charger to get things full again in a reasonable amount of time.

IBM/Lenovo Thinkpads usually draw a maximum of around 3.5 amps at 20 volts. Dells draw around 3.5-4.6 amps at 19.5 volts. Actual operating amperage is much less, particularly if you use the powersaving options in the laptop's software and hardware and if you start with a fully charged (good) battery.

The advice about using a 12-volt adapter is spot-on... you'll use less energy that way than if you have to jack it up to 110 VAC and then back down to 19.5/20 VDC. Radio Shack and other inexpensive retailers offer universal 12 volt power supplies for laptops, and they work just fine.

Paul,both batteries are less than 2 years old,so I should be ok.

I think I will go with a 12v adapter for the laptop.Seems more sensible than the inverter.

Duane,just a rough calculation and I am way under what we can expect to generate for power. Only occasional use for the laptop,maybe an hour with the stereo,so the panels should be able to recharge to capacity easily.

Thanks to all for the input (12v and 110!)

Duane,
15 hours per day of solar benefit? Or 5 hours per day as told by this boatus site? I am considering added solar and the calculation stage is where I am at trying to learn about it.
Boatus solar article

Back in Dec. we went on a 4 day cruise with a 15.6 screen laptop and watched 5 movies in CD. during a NE blow, we also ran all our other elect. stuff on board includeing 200 watt sterio,Cabin Lights, chargeing Batteries for cell phones and anchor light and also inflated and deflated a 9.5 ft. dingy.
We have two house 27 deep cycle batteries and after the trip the Voltage was 12.4 volts. I now have a Edgestar 66 quart cooler and will be testing it out for a 3 day trip to Cayo Costa. I have already connected it to the 12 volt system and ran for 6 days in the boat, also opened it couple times each day for around 2-3 min. Voltage was 12.7 when started and 12.6 after 6 days, temp was set at 38degrees.
I do live in SW Florida and this period was thru low temps. 50 degrees at night and 65-70 degrees daytime.
I do not have the house batteries connected to the Honda 50, only the starter battery.
My plan is to have the Edge Star at 32 degrees than unplug AC and run on 12 volt when I leave for a trip and put in 2- 1gal. frozzen water.
Will let you know what the voltage is after the trip but I think will be well above 12.2 volts.
Dave

KayakDan wrote:The plan is 2 65w solar panels,which should get plenty of sun in the Bahamas. I will be running an Edgestar fridge,some LED lights,a stereo sometimes,and occasionally a laptop computer for WiFi and a DVD once in a while. WiFi once or twice a week 10-15 min for Skype,and maybe a DVD once a week.
Will a laptop run on a 300w inverter without an issue,and how much power will a laptop draw typically? Does 130w of solar sound up to the task?

One last thing on this thread - a lot of the 12 VDC computer adapters will run the computer just fine, but wont charge the battery....they are chipped so that the computer wont charge unless it recognises the brand name charger...Dell in particular does this.

Opie,

The Boat US article comes at things from a different direction but gets close to the same place.

They say 5 times the rated output to get the daily average, in the case of a 120w panel this would say it will produce 600 watts per day.

I discounted the output 50% from 120w to 60w in my calculation and used 15 hours arriving at 900 watts per day. 10 hours of sunlight gives you the same number. I think during summer in the Bahama's you will get more sun than that. Up here in the PNW 10 is probably a better number to use.

Both are in the ball park and you should use numbers you feel are realistic for your situation, I think the Boat US number is extra conservative and can be improved by making some smart decisions when you install the panel.

If you install your panel in a way that you can aim it every few hours at the sun you will get better output. You also want to install it where it has the least chance of shadowing even by something as small as a line. Any shadow on the panel will reduce it's output. I think the Boat US example is further discounted by one of the worst location choices for a solar panel that is shown in their diagram, under the boom near the mast. It would be hard to find any time of the day when this location would not have some sort of shadow on it.

For me, on a Mac, there are only a few locations that are really acceptable for a solar panel installation. One is on an aft arch getting it as high and clear as possible from shadow creating objects. Installed there in a way that it could be aimed you should be able to get the most benefit from the panel. The other choice I see on our boats would be to create a system that allowed you to clamp the panel outboard of the lifelines on either side. The clamps could attach to the two cabin top lifeline stanchions. I might even run a SS tube between the stanchions on each side and mount the panel to it. You could use a pigtail to feed a common plug near the mast. I would make the mounts in a way that that the panel could hinge downward for storage and aiming at the sun. You would move the panel to whatever side is the sunny side of the boat throughout the day.



One wildcard with solar on our boats is their tendency to swing wildly at anchor. This can make any aiming difficult. I think if I was relying on solar to provide power for a heavy load like refrigeration I would get very comfortable with setting out a second stern anchor to keep the boat pointed in the desired position. We often do this to keep the bow pointed into passing wakes, but it also would lock the boat in place so you get the most benefit from the solar panel.

I also think I wouldn't be comfortable with a small house bank of just 200 amp hours for an extended trip. My two 6v golf cart batteries give me 220 amp hours in the house bank. These two batteries in their box really don't take up that much space and I would plan to add a second set next to them for a total of 440 amp hours in the house bank. My X could actually use some more weight forward. I find every time my wife goes to take a nap in the vee berth while under way we gain almost a knot in speed.

I have an 800amp booster jump pack it will charge from the batt. jumper cables I am sure but would have to check it also charges from the 110vlot inlet or 12vdc outlet it will run any 12v devise from the 12v dc outlet has a built in 12v light also, they make an excelent third back-up batt. and being mobile to boot are great for emg. can also be used on the beach ! and run my dinghy elect motor

J

Kelly Hanson East wrote:One last thing on this thread - a lot of the 12 VDC computer adapters will run the computer just fine, but wont charge the battery....they are chipped so that the computer wont charge unless it recognises the brand name charger...Dell in particular does this.

I'd heard where people were having problems like that. We bought a Lind....

http://www.lindelectronics.com/cgi-bin/ ... industry=1

.....and it has worked fine on both of our Dell Laptops. It runs on 12 volts, but puts out the 19-20 volts to the computer the same as the Dell 110 power supply. It wasn't cheap, but it is made very well and we would get another,

Sum

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