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Old 02-07-2014, 08:54   #1
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How to check you have sized your Electrical System correctly?

A general guide to see if you and your energy systems are in sync.

No need to know Peukerts law, just follow these steps after reading them all first.

1 - note your battery state of charge
2 - cover all battery monitors and voltage displays.
3 - go sailing for 2 weeks
4 - life as normal when using energy, no artificial saving.
5 - anchor for 4 straight days during this time.
6 - at the end of 2 weeks take a guess at the state of charge.
7 - now remove the tape and compare

If the state of charge is worse than you guessed then you are using more energy than your expectations. A resize may be needed.
If the state of charge is better than you guessed then you are using less energy than your expectations. No resize required and good for the future.
If the state of charge is below 50% then you need to be more in tune with your energy use and generation before doing tests like this.
If the state of charge is above 50% all is fine.

If not then you need one or more of the following solutions.
1 - More time charging in a marina.
2 - A bigger alternator or run your engine more.
3 - More solar or wind.
4 - Maybe also a method of producing energy while sailing.
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Old 02-07-2014, 08:59   #2
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Re: How to check you have sized your Electrical System correctly?

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Originally Posted by Fuss View Post
just follow these steps after reading them first.
I'm curious why you think it could be otherwise!

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Old 02-07-2014, 09:09   #3
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Re: How to check you have sized your Electrical System correctly?

follow them before reading?

Real men don't read instructions until afterwards
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Old 02-07-2014, 09:24   #4
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Re: How to check you have sized your Electrical System correctly?

Or a simpler method:

Go sailing for two weeks, including four days straight at anchor.

Don't cover any voltage displays or battery monitors.

After the trip is over -- did you spend a lot of time worrying about electrical power, studying the battery monitor, trying to save energy? Time and mental energy you could have spent enjoying yourself with your guests (or fixing the boat, as is more likely)? Did you run the generator to the point that it became annoying?

Or, did you spend hardly any time looking at the battery monitor and never worried about anything? Used whatever power you needed and charged when you needed to, without it being a particular bother?

If the former -- add battery capacity or charging capacity or replace gear or lighting with more efficient items, or buy a quieter generator, or change your power consumption habits, or some combination of the above, until you achieve the second state.

Simples!
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Old 02-07-2014, 09:31   #5
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Re: How to check you have sized your Electrical System correctly?

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Or a simpler method:

Go sailing for two weeks, including four days straight at anchor.

Don't cover any voltage displays or battery monitors.

After the trip is over -- did you spend a lot of time worrying about electrical power, studying the battery monitor, trying to save energy? Time and mental energy you could have spent enjoying yourself with your guests (or fixing the boat, as is more likely)? Did you run the generator to the point that it became annoying?

Or, did you spend hardly any time looking at the battery monitor and never worried about anything? Used whatever power you needed and charged when you needed to, without it being a particular bother?

If the former -- add battery capacity or charging capacity or replace gear or lighting with more efficient items, or buy a quieter generator, or change your power consumption habits, or some combination of the above, until you achieve the second state.

Simples!
Yes, sounds good.
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Old 02-07-2014, 10:46   #6
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Re: How to check you have sized your Electrical System correctly?

Here's an easier way.

All your electric stuff works when you need it and you don't blow any fuses.

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Old 02-07-2014, 10:55   #7
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Re: How to check you have sized your Electrical System correctly?

You forgot

5. Add more batteries to begin with.

You could do all of your 4, but if you start out with an undersized bank, 1-4 ain't gonna help at all.
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Old 02-07-2014, 11:25   #8
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Re: How to check you have sized your Electrical System correctly?

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Originally Posted by Fuss View Post
A general guide to see if you and your energy systems are in sync.....
You forgot one very important point - disable the Battery Monitor so that it doesn't auto re-sync when it 'thinks' you are 100%!
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Old 02-07-2014, 13:07   #9
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How to check you have sized your Electrical System correctly?

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You forgot one very important point - disable the Battery Monitor so that it doesn't auto re-sync when it 'thinks' you are 100%!

Yes, that's true.

Stu Jackson....you are missing the point. The post is to help show whether your systems and your use and your judgement of your systems are sized correctly and in sync with one another.

Not to make changes before the start.


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Old 02-07-2014, 13:08   #10
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Re: How to check you have sized your Electrical System correctly?

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If the state of charge is below 50% then you need to be more in tune with your energy use and generation before doing tests like this.
If the state of charge is above 50% all is fine.

If you are using the old "rule" of 50% you are living in the dark ages! Definitely if only 51% things are NOT all fine.
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Old 02-07-2014, 13:15   #11
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How to check you have sized your Electrical System correctly?

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If you are using the old "rule" of 50% you are living in the dark ages! Definitely if only 51% things are NOT all fine.

Let's not get complicated Sailorboy1, if you can stay out for 2 weeks without looking at your monitor or/and worrying and still have 50% , then your systems are generally fine.




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Old 02-07-2014, 13:27   #12
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Re: How to check you have sized your Electrical System correctly?

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Let's not get complicated Sailorboy1, if you can stay out for 2 weeks without looking at your monitor or/and worrying and still have 50% , then your systems are generally fine.

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Well I'm never going to agree with that! If you stay out for 2 weeks and your batteries don't get back to 100% every 2-3 days as a minimum then your system needs work!

And this from the person who says to stop obsessing about your batteries.

BTW - I take it we are only talking about old flooded acid batteries. If you have AGMs or gels, 100% SOC everyday applies.
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Old 02-07-2014, 13:53   #13
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Re: How to check you have sized your Electrical System correctly?

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Well I'm never going to agree with that! If you stay out for 2 weeks and your batteries don't get back to 100% every 2-3 days as a minimum then your system needs work!

And this from the person who says to stop obsessing about your batteries.

BTW - I take it we are only talking about old flooded acid batteries. If you have AGMs or gels, 100% SOC everyday applies.

There is a reason for having a battery bank and there is an optimum size / depth of discharge / price... A battery bank is part of a balanced system. Part of an energy system to give you a relaxed time away from the dock.

A battery bank that has to be charged everyday to 100%... Hmmm... I wouldn't want that on my boat.







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Old 02-07-2014, 14:49   #14
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Re: How to check you have sized your Electrical System correctly?

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...If you have AGMs or gels, 100% SOC everyday applies.
Please do tell us where you get this information from!

I have read all of Lifeline's information and postings on Morganscloud.com and Justin Godber does say FOR MAXIMUM LIFE CYCLES you need to recharge after each discharge, so that is where maybe you get your ideas from. In the same paragraph he also says AGMS and Gels are lead acid, just like other FLA batteries, so ALL batteries need to be recharged after each discharge - for maximum life cycles.

My Lifeline bank will take 5 days at anchor, with only 140 watts of solar before it gets near 50% SoC and I recharge. They are in their 10th year.
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Old 02-07-2014, 14:53   #15
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Re: How to check you have sized your Electrical System correctly?

I get some of my ideas from studies of various types of batteries on boats that don't get to recharge each day and their life. Like boats out on mooring or anchors.

If your AGMs are doing, great for you!

I'm not going to chase down studies for you. If you have a study other than your own experience you post it.
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