Solar Panel Fuse Question

[tricyclerob]

Good day all,

On an O'Day Mariner, originally with no electrical system, I built a stern rail and installed a 95 watt solar panel.
I'm using all LED lighting and other than a Garmin , VHF, a fan and some other tidbits my usage is about 80 - 120 watts per day depending on what I use and for how long.

The set-up is as follows;
I ran 10ga. wire from the panel to a Genasun MPPT Charge Controller, a distance of about 15'.

The controller is next to the battery, a 12v. 100Ah deep cell with 10g.wire from the Controller to the Battery.

From the Battery, a 10ga wire to a "Blue Sea Weather Deck switch panel" with idividual fuses for each circut.

What I don't have fused and what concerns me is the 10g, line from the Battery to the Switch Panel, a distance of about 6'.

What I was thinking of using was a "Blue Sea Systems 5191 Fuse Block Terminal", [30-300 amp] that attaches directly to the battery post, but the lowest amp fuse is a 30amp.

As all the circuits are individually fused, I'm really looking to protect the wire from the battery to the panel against shorting.

Does this sound reasonable?

Thanks,
Rob Jones

 

[justsomeguy]

Yes.

 

[tricyclerob]

Mr.Just,
That was succinct.
Thanks,
robj

P.S. And good for a little chuckle as well!

 

[All U Get]

Pretty nice work, does the panel tilt?

All U Get

 

[tricyclerob]

Thanks,
Yes, The panel does tilt but only fore and aft. I think I would be for the most part leaving it level while sailing then maybe tilting when anchored or in the slip.

The frame around the panel itself was not very robust, so I built a frame for it to sit in from 3/16 aluminum angle.

The bench is removable and stores under a side berth.

I have probably about $1200 or so in everything, or to put it another way, 2 times the original price of the boat. Of course this makes sense.

robj

How do you make a $600 boat worth $3000? Spend $6000 on it.

 

[jviss]

Reasonable?

It's really nice work! The setup sounds reasonable to me. I would certainly install the fuse on the battery terminal.

My other initial reactions are that it's a ton of panel capacity, and a huge battery for a boat that size, without any large electrical loads like a fridge.

Your panel and battery could probably keep an Adler-Barbour 12V DC fridge up 24/7!

Also, the way you express your usage doesn't quite make sense; it would more accurately be expressed in units Amp-hours. Watts is an instantaneous measure of power, not power or energy over time.

Nice job!

 

[syoun10]

It's really nice work! .................

Also, the way you express your usage doesn't quite make sense; it would more accurately be expressed in units Amp-hours. Watts is an instantaneous measure of power, not power or energy over time.

Nice job!

jviss is right! I see this "units" mistake made all the time - even in major publications like Sail and Cruising World, and even by well respected and often-followed authors. I've often wondered whether to comment, but was concerned about being seen as "picky". However there is room for confusion if one is following advice or instructions which contain this mistake. So kudos to jviss.

 

[tricyclerob]

My plan, being semi-retired, is explore as many rivers of the Chesapeake as I can do, as far up river I can get with 10" draft.
Should be pretty far up. [1970 O'Day Mariner, 19', swing c.b., 10" draft]

I spent years camping off the back of a BMW motorcycle so the "cabin" of the Mariner is like a room at the Hilton.

Gone, 2,3,4, 5 days at a time, checking work with a laptop. [As seldom as I can manage without the place imploding]

Ok, here's my math.

I took everything I would possibly use, nav. lights, anchor light, cabin lights, cabin fan, GPS/depth finder, VHF, I-Pad, Phone, identified the amps used per item x maximum anticipated hours per day use.
I came up with 22.05 amps per day x 12 v. = 264.6 watts, [265watts]

The Solarland panel I have is 95 watts per hour per day, [6hrs x 95watts = 570 watts], which is based on 6hrs of "perfect" sunshine.

The monocrystalline panels are very suseptible to any amout of shading, the smallest amount of which can reduce output by 50%. [sail, mast, low flying bird,etc...depending on direction of travel]

Sooooo,
my thinking was I possbly need 265 watts per day, so with 570 watts a day [maybe less if it rains all day, shading, etc..], I should have decent reserve with the 100Ah battery, even if the output is considerable less, and /or it rains for 2 or 3 days.

Keep in mind, no alternator or any other method to re-charge the battery.

Am I missing something?
Maybe I wasn't clear originally, I guess I should have said the "minimum" use would be 80-120 watts,

or maybe I've had a huge "Brain Fart".

Let me know,
thanks,
robj

 

[Ray Bowles]

robj, How many amps do the lights use up to make all that varnish pop as nicely as it does? Nicely done.
Ray

 

[tricyclerob]

robj, How many amps do the lights use up to make all that varnish pop as nicely as it does? Nicely done.
Ray

Ray,
You gave me a laugh. It's about 3-4 coats of the special clear WestSystem with 3 or 4 coats of varnish, wet sanded between coats.
It doesn't take long if doing the pieces all at the same time.

A little bling goes a long way.
Thanks,
robj

 

[tricyclerob]

"Ok, here's my math.
Am I missing something? "or maybe I've had a huge "Brain Fart".

Any Solar Panel Experts out there? A few comments made me doubt my " math", never my strong point anyway.

Thanks,
rob j

 

[tricyclerob]

Dang,
No experts??

robj

 

[jviss]

Dang,
No experts??

robj

I am not a solar power and remote power expert, but I am an electrical engineer. I commented earlier in this thread that you are using the wrong units to express your consumption. Watts is a unit of power, and is instantaneous, that is, it does not account for energy usage over time. Think of it as speed, when what you want to calculate is distance over time.

I recommend you re-do your math to express your energy use and production in units of Amp-hours. For example, how many hours per day, at what Amperage, does each load consume? You should use the measure of Amperage as measured at the battery; otherwise you'd have to factor in conversion inefficiencies. If you want to be more accurate you will account for the battery's charging and discharging inefficiency, Peukert factor, but it's easier to just add some margin to the capacity required after the basic calculations.

The top-level analysis, which I think you have correct, is to determine whether the panel puts into the battery what you consume on a daily basis. Next you have to determine whether the battery's usable capacity is sufficient to hold the loads up when the panel's not producing as much as you are consuming, e.g., at night.

I think you will find that the laptop is the killer load. I have found that mine draws up to 10 or 11 Amps at times, and the power adapter is notoriously inefficient; it's a 15" MacBook Pro. Your mileage may vary. If you can get or make a direct 12V to laptop power adapter that will likely help a lot.

If you need help with these calculations I can assist.

 

[Maine Sail]

I am not a solar power and remote power expert, but I am an electrical engineer. I commented earlier in this thread that you are using the wrong units to express your consumption. Watts is a unit of power, and is instantaneous, that is, it does not account for energy usage over time. Think of it as speed, when what you want to calculate is distance over time.

I recommend you re-do your math to express your energy use and production in units of Amp-hours. For example, how many hours per day, at what Amperage, does each load consume? You should use the measure of Amperage as measured at the battery; otherwise you'd have to factor in conversion inefficiencies. If you want to be more accurate you will account for the battery's charging and discharging inefficiency, Peukert factor, but it's easier to just add some margin to the capacity required after the basic calculations.

The top-level analysis, which I think you have correct, is to determine whether the panel puts into the battery what you consume on a daily basis. Next you have to determine whether the battery's usable capacity is sufficient to hold the loads up when the panel's not producing as much as you are consuming, e.g., at night.

I think you will find that the laptop is the killer load. I have found that mine draws up to 10 or 11 Amps at times, and the power adapter is notoriously inefficient; it's a 15" MacBook Pro. Your mileage may vary. If you can get or make a direct 12V to laptop power adapter that will likely help a lot.

If you need help with these calculations I can assist.

+1

I have one customer who did an energy budget and allowed for 10Ah's/day for his laptop. As he used it, open and on nearly 24 hours per day, for navigation etc. it was consuming more than his DC refrigeration..... BTW my Macbook Pro 15" is also a power hungry pig.

Use a DC volt meter set to DC Amps / 10A range and insert this in series between the - or + connection on your battery. Now turn items on one at a time and note the actual consumption. (Do not turn items on known to draw more than 10A or motors with high in-rush). This will give you a rough guide for fixed amperage loads such as lights and a VHF in standby but won't be much of a help for a laptop which is a highly variable load. Be careful with the laptop as it can possibly surge above 10A and blow the meters 10A fuse... A clamp meter is a much better tool for this but more expensive.

 

[LloydB]

You have a 100Ah battery not a 1200 watt battery hope that helps with the sense of the use calculations.

 

[tricyclerob]

Jviss,
I'm pedaling as fast as I can to keep up.

When I did this; "identified the amps used per item x maximum anticipated hours per day use. I came up with 22.05 amps per day". I used the spec's as indicated for each item but as nothing was assembled or hooked up it wasn't possible to measure any "real time" amp draw.

As you suggested doing, "For example, how many hours per day, at what Amperage, does each load consume?" , that is what I did with my calculations, correct ?, just not with actual measurements.

So when you state, "The top-level analysis, which I think you have correct", you are saying my calculations are correct as far as they go without actual measurements ?

So at 22-23 amp/hrs and figuring at least a 50% reserve, how would I have got to a solar panel size when their output is measured in Watts per hour? This is why I converted my usage to watts as these were the instructions with every solar load calculator I looked at.

I guess this is moot as the panel is bought and mounted but I am curious none the less..

As far as the battery is concerned, this was the largest physical size/Ah I could use that would fit in the space I had available, soooo, I guess that's a bit of a moot point as well.

Like I said, I'm peddling as fast as I can.
Thanks for you assistance,
robj

 

[jviss]

Almost there.

Hi Rob,

You are almost there. I think that with that panel, and the battery you bought, you have as much non-generator or shore power electricity as it is possible to get on that boat. Moot at this point, yes, but probably adequate.

For the calculations you are correct that you should estimate Amps consumed times anticipated hours of use per day, the result being in units of Amp-hours, not Watts.

For panel input to the system the capacity of the panel in Watts is a good starting point. Find the rest of the specs for the panel. Somewhere it might say what the Amperage output of the panel is under load. Your solar panel regulator will have something to do with this, too; by the way, you chose an excellent solar regulator. I, personally, if I had a 95 Watt panel, would start by assuming, conservatively, that I'd get 5 Amps of charging current at the brightest part of the day, that is, 5 Amps flowing into the battery when the battery is in the 13.6 to 14.4 V neighborhood. If you taper this off to, say, 2 Amps at 9:00 a.m. (all summertime calcs) and 2 Amps at 6:00 with three hours in the middle in the 4.5 to 5 Amp neighborhood you should be over 30 Amp-hours per day, at the battery. This is more than your load budget by quite a bit, so I think you'll be fine. This is all seat-of-the-pants calculations. Best to build a spreadsheet and then fine tune it by improving your assumptions and margins.

 

[tricyclerob]

Jviss,
I had actually figured the laptop at 8a. not 10-11, so I'm probably at 25amps or so. The 30 amp charging does give me some margin. The panel indicates 5.52 amps at load.

When I did a battery calculation at 30amps it indicated a 120 ah. battery and mine is 100ah. due to the size limitations of the space I have. All in all, looks like it should work out for my needs. I wonder why all the solar panels are advertised in watts, not amps.

I got the battery portion mostly finished last night, now onto the fuse panel.

I might not know what I'm doing but at least I'm neat about it.

Thanks again,
rob j

 

[DAVA390]

Rob ,It`s worth a breakfast at Sunshine to let me come see this some day.

 

[dandrews]

Nice job Rob, very nice. Are you a pipe bender by trade? The S/S work is top drawer.

Don