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first sailed january 2008
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Discussion Starter · #1 ·
Well, last summer I used very, very little power. So little that a seven watt solar power was my sole means of charging my battery and it never died.

This year I'm upping things. I'm sitting here organizing and packing, well. I'm done for the night, but I've got a LOT of lithium battery toys to charge. I know a lot of it is small. Camera batteries. A laptop. Ipad, phone. Bluetooth things.

Then I have the boat stuff. I've got a ray marine st2000 autopilot, I think I will use extensively, chart plotter, depthsounders, led nav and spreader lights, led interior lights and assorted boat electronics. Oh and a stereo with two speakers.

Battery consumption is on my to do list to learn, but I'm not there yet. Basically do you think I have enough of a system to work?

I have two gel batteries. I believe 97 amp hours each, a 50 watt solar charger, an alternator on my outboard and maybe a small generator. Let's pretend I don't have a generator because I'm not sure I do. Will my solar panel and alternator be enough, and do I have enough for my battery bank?

My thinking is that the solar will do a lot, and the rest I'll just have to be that guy that idles his engine on days I don't spend extensive time motoring to a new place. Maybe idle an hour a day? Is this a good base plan or do I need to start thinking about a fix?
 

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Here's a link to an old thread that had some good info about battery monitors and how to calculate your electrical consumption.

http://www.sailnet.com/forums/electrical-systems/66064-battery-consumption-charging-calculator.html

I made an excel spreadsheet for my boat where I listed each electrical device, an estimate of it's electrical draw when operating, and the estimated number of hours per day that it would be turned on - not sure how to copy it here but PM me and I can e-mail it to you.
 

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There maybe some who tell you to calculate everything, but its impossible.

The only way to do it is trial and error.

I bought a $10 multimeter and just shoved it in the cigarette socket 10 times per day. No battery monitor, no charge controller, just solar directly into the batteries.

When the multimeter says you are under 12.24 without load (ie everything is off) or below 12.11 with big things on, then get the engine on. Or turn off things.

You will see how its going to work with you. I think you need a larger solar panel. But the engine is fine in the interim. Mine idles at 800 rpm but I charge at 1200 rpm.

If you need to charge at 2am do it then.

All the stupid phine batteries etc we have now, i charge in the afternoon when my batteries are full.

Its all just trial and error.

BTW the multimeter has a continuity checker. Make sure yours has that feature :) not for this, but other electrical stuff
 

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Most of your loads are small, with the possible exception of the laptop and the stereo. My gut feeling is you should be OK as long as you are a bit careful with usage. Only issue is that the generators on outboards don't put out the power that an inboard does, so bringing a low battery back is going to take a LONG time. But that 50 watt solar panel should keep up fine. With that size panel and your small battery banks, I hope you have a solar controller.
 

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There maybe some who tell you to calculate everything, but its impossible.
Trying to precisely determine your exact energy usage every day is impossible. No doubt about that. But doing a few calculations, to get you into the general neighborhood, is definitely not impossible. I think it's also very worthwhile.

You at least need to look around and ask yourself what are going to be the big energy hogs, and roughly how much are they going to use. Otherwise you end up like the people we've seen posting here in the past, who can't understand why their battery keeps going dead. Then, when pressed, we find that they are trying to run an air conditioner all night on a single Group 27 battery with a 40 watt solar panel to charge it!

Getting obsessive about trying to nail down your usage to the nearest electron is a waste of time. Doing a few calculations to get a rough idea of how much you will use, and therefore what sort of battery bank and charging capacity you need, is a very worthwhile use of your time.

Oh, and to the OPs question... No, a multimeter is not the same as a battery monitor. Completely different thing.
 

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What model of laptop do you have? Newer ones use very little power, most older ones can use quite a lot.

The battery monitor recommended is the best way to learn how much each of your devices is consuming.

I found a 20 watt panel and the tiny outboard alternator provided more than enough power on my Catalina 25 to keep a cell phone, iPad, and lower-power Macbook Air charged and allowed us to use the LED cabin lights, VHF radio, and ST2000 autopilot. However we were cruising in the middle of Seattle's summer when it was always sunny. We had no battery monitor, just a voltage meter.

On my much longer cruise last summer I had a 40 watt panel and much higher output alternator on my Pearson 28-2 along with a good battery monitor. We've added more electronics (plotter, wind/depth/speed instruments, more advanced autopilot), a second tablet, and electric water pumps. Our batteries never fell below about 90% charge.

On both boats I had 2 group 24 batteries as our house bank. We never plugged into shore power on either trip.

I think you'll be okay, but measuring is the best way to really know. It also depends heavily on your laptop, some consume up to 40 or 50 watts per hour while in use, others consume under 5.
 

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A slight deviation here. I'm in the market for a battery monitor. I've looked at the Xantrex Pro and the Victron, and Clipper. In all the reading it was never mentioned that sensing the alternator charging required a shunt shifter as it is mentioned in the blurb on the Blue Sea Sytems DC panel meter in the Jamestown web site.
"Standard meter operates in negative side of circuit only. Shunt Shifter required for positive side installation such as alternators"

Is this requirement standard for all monitors or just for the Blue Sea?
And just how important is temperature sensing in calculating remaining battery power?
 

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Another small detour. In the last year and a half I ended up replacing my personal electronics. I made sure that each one I bought did its charging through a mini-USB connector. Now with just a USB power port and one cable, I can charge my phone and tablet. No wasted power with a proprietary 'wall wart'.

The 12VDC charger I got for my laptop years ago got very warm while charging it. I knew the charger was squandering my power.

Ken
 

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A slight deviation here. I'm in the market for a battery monitor. I've looked at the Xantrex Pro and the Victron, and Clipper. In all the reading it was never mentioned that sensing the alternator charging required a shunt shifter as it is mentioned in the blurb on the Blue Sea Sytems DC panel meter in the Jamestown web site.
"Standard meter operates in negative side of circuit only. Shunt Shifter required for positive side installation such as alternators"

Is this requirement standard for all monitors or just for the Blue Sea?
And just how important is temperature sensing in calculating remaining battery power?
Battery monitor shunts are universally installed on the DC negative side. The "shunt shifter" that Blue Sea mentions is only if you want to use their digital DC meter on the positive output of an alternator or other charging source to monitor its specific activity in isolation rather than the total current flowing into or out of your battery bank from all loads and sources. Battery monitors like the Link/Xantrex or Victron look at all loads and sources so the shunt needs to go in-line with the ground cable to your battery bank with only your battery on one side and all other ground return wires on the other.

NB, if you're primarily interested in monitoring your bank's state of charge, the shuntless "Smartgauge" from Balmar seems to be the bee's knees. If your primary interest is in monitoring the real-time and accumulated current into and out of your bank, a traditional monitor is better but won't give you an accurate SOC without lots of legwork on your part due to changes in your battery's characteristics as they age.

MaineSail has good writeups on both here:

Compass Marine How To Articles Photo Gallery by Compass Marine How To at pbase.com
 

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Mark, I like your approach. However, the part I don't know (or don't understand) is how to factor in the effect that charging the battery has on the open circuit voltage. ie: the instructions for estimating percent charge is to let the battery rest (no charging ) for a long time, then take a reading. Should I expect the open circuit voltage to be different in the middle of the day while I had just been using stuff, and charging with a solar panel?
 

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A slight deviation here. I'm in the market for a battery monitor. I've looked at the Xantrex Pro and the Victron, and Clipper. In all the reading it was never mentioned that sensing the alternator charging required a shunt shifter as it is mentioned in the blurb on the Blue Sea Sytems DC panel meter in the Jamestown web site.
"Standard meter operates in negative side of circuit only. Shunt Shifter required for positive side installation such as alternators"

Is this requirement standard for all monitors or just for the Blue Sea?
Most factory alternators are case grounded. Thus if you want to monitor the output of a case grounded alternator specifically, then a shunt shifter would be needed.

Typical battery monitors do not require a shunt shifter because they measure the "net" going into or out of the bank.

The Xantrex Link Pro, Link Lite, Victron, Philippi, BM Pro etc. are all decent monitors. The Clipper and a few other elcheapos decide the Peukerts constant for you.. Not good if you ever want it to be accurate. The Blue Sea VSM has some proprietary voltage algorithms that try to predict Peukert , but I have not had a chance to physically test it.

And just how important is temperature sensing in calculating remaining battery power?
Temperature sensing or temp programming is pretty important IF you actually want to derive some accuracy from the monitor.. If your batteries are normally at 70-80F no big deal, not critical, but up here in Maine I had a temp sensor on my Link-Pro when I had lead acid. This saved me from having to reprogram the battery temp for spring, summer and fall... This time of year my batteries might be at 50F due to the cold ocean temps and that can cut into available capacity..

Proper programming and wiring of any Ah counter is critical for the best performance...
 

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A good way to estimate power draw on a laptop is to look up the battery capacity of the laptop, then divide by your actual average battery life. Add about 20% for power supply and charger efficiency losses.

Your laptop has a 95 WH battery. If it lasts 5 hours under your normal use then that is about 25 watts per hour. Your panel can provide about 250 watts per day (assuming a good MPPT charger), so using the laptop a lot does make it a significant draw.
 

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Mark, I like your approach. However, the part I don't know (or don't understand) is how to factor in the effect that charging the battery has on the open circuit voltage. ie: the instructions for estimating percent charge is to let the battery rest (no charging ) for a long time, then take a reading. Should I expect the open circuit voltage to be different in the middle of the day while I had just been using stuff, and charging with a solar panel?
Yes, this is exactly what I mean by 'its all trial and error'. If you walk onto someone elses boat and look at their meter you wont know the state of their charge no matter what their meter reads.

But on your own boat over a period of days or weeks you get to know it well. As I live aboard I watch it all the time... I just checked and at 2:15 pm its 14.45 volts and the Solar charger is flashing which means its more than 90% charged (but I dont know if its 91 or 99%.) the fridge is cycled off. I just manually turned the fridge on and its still 14.45 and flashing so it must be pretty well charged.
At sundown, with nothing turned on, it should drop to about 12.80. Midnight it will be about 12.56, dawn about 12.32.

If at 2 am its down to 12.30 I know I have screwed it up, like used the big computer for too long, or there wasnt enough sun, or the fridge was set too cold etc.

If its 2 am and 12.30 but the fridge is on then I know I am ok till morning.

It only takes a few minutes for the voltage to normalise if you turn something off. And you don't need to let the battery rest for long after charging. Give it 5 minutes then turn a tap on for 5 seconds and when you turn it off the battery will show the correct charge.

The point is that when you live on board you get very attuned to it and you make the electricity out fit with the electricity in.

So, for instance, if I want to freeze something for a week I would have to run the engine at night too. Or fix it. Which is what I am doing this year by getting a bigger battery bank and more solar (or maybe wind for nights).

The trial and error means you have to monitor it the whole time and be flexible.
If you screw up and the battery is down to 11.9 then the batteries have been hurt.

Over a period of time you will get to know yours and if you have excess electricity you will find a way to use it :) thats easy! You can always add.

Its probably easier to start simply and make it all 'fit' together.

I don't know how people can do it if they are only on the boat for weekends. That would really stuff things up.

I hope this helps. :)

BTW the other way of doing it is just to throw money at it... But this is the affordable way.

Mark
 

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first sailed january 2008
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Discussion Starter · #18 · (Edited)
Is this a controller or mppt? I have this that the batteries are connected.

Say...is it hard to reinstall my gel batteries? I know it doesn't seem like it would be, but for some reason when I bought the boat, the owner wanted to give $150 from the sale of the boat to his acquaintance, a guy that has a marine electronics store to install them for me. But when I talked to the shop guy he didn't want to take the money because he said it was easy and I could do it.
 

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I tried to read that book once. It didn't absorb, I'm not good at blue collar trades for the most part.
Well, in that case, you may want to re-think that whole circumnavigation thing, sailing a small boat around the world is likely to involve a hefty dose of that "blue collar trade" stuff... :)

Unless you want to pay others to do it for you, of course...

Creating a rough energy budget isn't exactly rocket science, but it can be pretty damn important. Stanley Paris learned that lesson the hard way :)

Here are some other samples, but the one in Don Casey's book is probably as good as any...





http://newcontent.westmarine.com/content/documents/pdfs/WestAdvisor/Elecbugt.pdf
 

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Is this a controller or mppt? I have this that the batteries are connected.
What solar charge controller do you have?

The 3 basic options are:
* Shunt -- Cheap (under $20), but won't fully charge the batteries. Turns off for long periods of time when the battery charge crosses a certain set point voltage.
* PWM -- Will charge to higher voltages (it turns off for very short periods of time to avoid overcharging). Throws away any excess voltage, so if you panel is generating 18V at 2A and the charger is set to 14V at 2A you are throwing away 8 watts of power (4V * 2A).
* MPPT -- Like PWM, but uses a DC-DC converter to convert any voltage being produced over the charging point into amps. So it would be able to make use of the 8W lost by the PWM.

Genasun sells less expensive MPPT chargers for smaller solar arrays. The one on my boat cost about $70 and is good for up to 5amp (60watt nominal) solar panels.

Say...is it hard to reinstall my gel batteries?
It is no more difficult than replacing a car battery. You need to be careful not to short anything, but it is not hard. $150 is highway robbery to install two batteries if there are already proper battery boxes or trays installed in the boat.
 
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