How to check you have sized your Electrical System correctly?

[Pete7]

If you can go for 2 weeks with only ad hock charging and still have safely over 50% in the bank you might have one or two (dozen) too many batteries.

Of course if you can afford the extra costs and don't mind the extra half tonne of lead carry on.

[sailorboy1]

Originally Posted by Pete7

If you can go for 2 weeks with only ad hock charging and still have safely over 50% in the bank you might have one or two (dozen) too many batteries.

Of course if you can afford the extra costs and don't mind the extra half tonne of lead carry on.

How much charging is ad hock?

[Ex-Calif]

Originally Posted by Fuss

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.

I tried this method.

- After the first night on the hook the A/C was not running
- The coffee pot made coffee but then the toaster wouldn't toast
- The clothes dryer won't run at all
- Then around lunch time all the cabin lights, tv and power outlets went dead when my wife was drying her hair (after using all the freakin' hot water)

I am sending this from my iPad hooked up to my sat phone.

Do you think I need more solar or more batteries?

The iPad charge is at 20% and the sat phone is at 30% - reply quickly as I don't know how long these will last and I am planning to watch a movie on iTunes...

PS - Your instruction also said I might need more wind. It's been blowing like hell here so I don't think that's the problem. I don't have one of those Propeller thingies like other boats or I could tell you how fast its going. The wind instruments died at lunch too so they are no help. I'm guessing the wind is blowing 20 knots. How do I get more?

[sailinglegend]

Originally Posted by sailorboy1

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

You have made a very bold statement here that suggests this is accepted fact, without saying IMHO.

In my response I quoted Lifeline, you have provided no links to support your ideas.

The bottom line is not all AGMs are equal and MOST users don't charge them properly. They need a minimum of 20%C, so a 400 Ah bank would need at least a 'hot rated' marine alternator or shore power charger of 100 amps - that's 20% for the batteries and 5% for boat loads. I don't mean to create a thread drift here, I'm just looking for accurate postings.

[Fuss]

Originally Posted by Pete7

If you can go for 2 weeks with only ad hock charging and still have safely over 50% in the bank you might have one or two (dozen) too many batteries.

Of course if you can afford the extra costs and don't mind the extra half tonne of lead carry on.

Battery banks and their charging systems don't work the way you understand. Systems have to be in balance.

every cruiser cruises in a different style, however the average cruiser does something similar to this over a 2 week period when not on shore power.

Motors out of an anchorage in the morning for maybe 15-20 mins
Sails for some hours
Motors into an anchorage in the afternoon for maybe 15-20 mins
Sometimes motors if no wind
Spends more than one day in the same anchorage
May sometimes sail overnight or longer distances

So, in order that the cruiser does not spend alot of time converting diesel into electricity without providing propulsion or using the engine when they could be sailing. The following is needed

The right sized battery bank
The right sized alternator
A method of generating power when the motor is off.
Consumption devices should be generally efficient.

[Ex-Calif]

Originally Posted by Fuss

Battery banks and their charging systems don't work the way you understand. Systems have to be in balance.

<snip>

The right sized battery bank
The right sized alternator
A method of generating power when the motor is off.
Consumption devices should be generally efficient.

I was somewhat glib in my first response because I suspected you might be thinking of a new paradigm - that of an abundance mentality.

Your idea that you can just consume and then resize the system to fit that is interesting but there is always a limit.

There are only 3 variables - Consumption, generation and storage.

Generation is the limiting item. There are only 3 viable ways to make electricity on a boat - Solar, wind and burn hydrocarbons.

All of these are limited by boat space and storage space for fuel.

Storage is only about increasing the time between the need to generate more electricity. It is also limited by space on a boat.

Consumption therefore must be limited based on the constraints on the boat.

I agree 100% that things must be in balance. however a 2 week "set and forget" strategy with ad hoc charging is not efficient. Actively managing the power is required.

[Dockhead]

Originally Posted by Fuss

Battery banks and their charging systems don't work the way you understand. Systems have to be in balance.

every cruiser cruises in a different style, however the average cruiser does something similar to this over a 2 week period when not on shore power.

Motors out of an anchorage in the morning for maybe 15-20 mins
Sails for some hours
Motors into an anchorage in the afternoon for maybe 15-20 mins
Sometimes motors if no wind
Spends more than one day in the same anchorage
May sometimes sail overnight or longer distances

So, in order that the cruiser does not spend alot of time converting diesel into electricity without providing propulsion or using the engine when they could be sailing. The following is needed

The right sized battery bank
The right sized alternator
A method of generating power when the motor is off.
Consumption devices should be generally efficient.

People also have different attitudes about generating and consuming electrical power.

Some people don't have generators or don't like to use them. Some people count every amp/hour and worry about it.

I think electrical power is a bit like money -- as long as you spend less than you earn, you're fine, and it doesn't actually matter nearly as much as you might think what that absolute quantum of it is.

On our boat, it's very simple -- we have a big school bus alternator on the main engine, an almost silent heavy-duty generator, and a medium-sized (420 amp/hours at 24v) battery bank. The 110 amps * 24v alternator can produce over 2.5kW and charges the house batts very quickly. It means after any amount of motoring we usually start off with full batts. We rarely have consistent enough wind for 24 hours at a time of sailing, but the batts have enough capacity for making way for 24 hours or so with all electronics running, nav lights at night, some use of microwave and kettle, etc., before we start thinking about charging.

I spend a lot of time, up to weeks at a time, on my mooring or at anchor with no shore power. This is where the Kohler genset is a Godsend. The key attribute is that it is very quiet, so you don't fret about running it, you just crank it up whenever you need it. Living aboard with no shore power, I usually run it for a couple of hours around dinner time, when AC power consumption is at its maximum, and often that's enough. If needed, I run it for an hour or two in the morning (if I'm heating the boat, this is usually required, since the central heating system uses a good bit of electrical power even though it's diesel fired). AC power intensive tasks like washing clothes are concentrated into periods when the generator is running.

We have lot of AC consumers on board (microwave, kettle, washer/dryer, vacuum cleaner, toaster, coffee machine, A/V equipment, etc., etc.), and when there are 5 or 6 people on board, there are tons and tons of personal electronic devices to charge (phones, tablets, laptops, cameras, etc., etc.). So the inverter runs 24/7; I long ago stopped trying to save a few amps by turning it on and off. I charge my own phones and computers with DC chargers hardwired at the nav table; but once you get up to several other people on board which means a dozen or more devices to charge, it becomes impossible and you just have to let people plug into regular outlets.

Could we have a bit larger battery bank? Certainly; I wouldn't mind it. Power is here again like money -- however much you have, a little more would always be welcome . What would be fabulous would be a batter bank of about the same nominal capacity, but LiFePo, so it would have nearly twice the usable capacity. But do I need it? No, not at all -- our present setup fulfills all needs and does not produce any inconvenience at all.

[Zanshin]

sailinglegend - the reason that Sailorboy hasn't posted any links to studies or other sources confiming that AGM or Gel batteries need to be charged to 100% daily is because there aren't any, that is utterly false.

I've got 1000Ah of batteries aboard, and because of acceptance rates the charging rate goes down once 90% of battery capacity is reached, and putting in those last 100Ah at a rate of 40A then later 20A takes 3-4 hours so that I reach 100%. That is patently unfeasible and unrealistic.

I haven't been to a dock in over 7 months and have been traveling around. I started taking battery readings several times a day a couple of months ago because I thought my Xantrex was reading incorrectly and it has become habit, so my spreadsheet has 886 readings as of this morning, including begin/end times for both motor running and genset running. A month ago I put in 375W of solar so recent readings are different, but I have a very good idea of both my consumption and state-of-charge.

Here in warm waters the refrigerator and freezer eat up most of my power (despite my attempts at improving on the insulation) and my daily consumption is about 240Ah, my generator and Victron charger charge at 200Amps and I run the genset for about an hour to an hour and half (until the acceptance drops off to about 40A and the bank is 90% full).

Since I only have 2 days of power (since only 50% of my 1000Ah bank is useable) I believe my bank is too small, hence the foray into solar - if I increase my solar panel size then I can dispense with the genset, except for the weekly or bi-weekly charge up to 100%. But I could do that by running the generator in the morning to 90%SOC and then letting the solar panels do the slow remainder.

p.s. My boat is actually 24V, but the numbers I posted are converted to the more common 12V for easier comparison. In reality I've got 480Ah@24V and use 120Ah per day, an even 5A constant drain.

[sailorboy1]

hey since I haven't said it in a few weeks - I ain't no expert and only can post about things I've read about etc. and that I'm not going to chase down the studies.

For you experts, post your credentials and links to studies to support your position. You just saying so isn't any different than what I did that seems to be so wrong to you

I'm willing to change my position - ALL batteries should be recharged to 100% every day.

[Dockhead]

Originally Posted by Zanshin

sailinglegend - the reason that Sailorboy hasn't posted any links to studies or other sources confiming that AGM or Gel batteries need to be charged to 100% daily is because there aren't any, that is utterly false.

I've got 1000Ah of batteries aboard, and because of acceptance rates the charging rate goes down once 90% of battery capacity is reached, and putting in those last 100Ah at a rate of 40A then later 20A takes 3-4 hours so that I reach 100%. That is patently unfeasible and unrealistic.

I haven't been to a dock in over 7 months and have been traveling around. I started taking battery readings several times a day a couple of months ago because I thought my Xantrex was reading incorrectly and it has become habit, so my spreadsheet has 886 readings as of this morning, including begin/end times for both motor running and genset running. A month ago I put in 375W of solar so recent readings are different, but I have a very good idea of both my consumption and state-of-charge.

Here in warm waters the refrigerator and freezer eat up most of my power (despite my attempts at improving on the insulation) and my daily consumption is about 240Ah, my generator and Victron charger charge at 200Amps and I run the genset for about an hour to an hour and half (until the acceptance drops off to about 40A and the bank is 90% full).

Since I only have 2 days of power (since only 50% of my 1000Ah bank is useable) I believe my bank is too small, hence the foray into solar - if I increase my solar panel size then I can dispense with the genset, except for the weekly or bi-weekly charge up to 100%. But I could do that by running the generator in the morning to 90%SOC and then letting the solar panels do the slow remainder.

p.s. My boat is actually 24V, but the numbers I posted are converted to the more common 12V for easier comparison. In reality I've got 480Ah@24V and use 120Ah per day, an even 5A constant drain.

Solar, of course, is the killer app for lead-acid batteries which need a trickle charge up to 100% from time to time.

Because of the huge inefficiency of charging up the last 10% to 20% of L/A batteries' capacity, it really can't be practically done with a generator. It has to be done when you have surplus power -- shore power, motoring for a long time, or solar.

I would love to have some solar for this very reason (and to keep my batts up when I'm not on board), but I've got no good place to put it. As it is, I try to get a 100% charge at least once a week or so, and it usually means either a passage under motor or a night in a marina. This means I'm working my batteries pretty hard, but they're Trojans which so far (touch wood) are holding up really well to this hard usage.

[Fuss]

Originally Posted by Dockhead

People also have different attitudes about generating and consuming electrical power.

Some people don't have generators or don't like to use them. Some people count every amp/hour and worry about it.

I think electrical power is a bit like money -- as long as you spend less than you earn, you're fine, and it doesn't actually matter nearly as much as you might think what that absolute quantum of it is.

On our boat, it's very simple -- we have a big school bus alternator on the main engine, an almost silent heavy-duty generator, and a medium-sized (420 amp/hours at 24v) battery bank. The 110 amps * 24v alternator can produce over 2.5kW and charges the house batts very quickly. It means after any amount of motoring we usually start off with full batts. We rarely have consistent enough wind for 24 hours at a time of sailing, but the batts have enough capacity for making way for 24 hours or so with all electronics running, nav lights at night, some use of microwave and kettle, etc., before we start thinking about charging.

I spend a lot of time, up to weeks at a time, on my mooring or at anchor with no shore power. This is where the Kohler genset is a Godsend. The key attribute is that it is very quiet, so you don't fret about running it, you just crank it up whenever you need it. Living aboard with no shore power, I usually run it for a couple of hours around dinner time, when AC power consumption is at its maximum, and often that's enough. If needed, I run it for an hour or two in the morning (if I'm heating the boat, this is usually required, since the central heating system uses a good bit of electrical power even though it's diesel fired). AC power intensive tasks like washing clothes are concentrated into periods when the generator is running.

We have lot of AC consumers on board (microwave, kettle, washer/dryer, vacuum cleaner, toaster, coffee machine, A/V equipment, etc., etc.), and when there are 5 or 6 people on board, there are tons and tons of personal electronic devices to charge (phones, tablets, laptops, cameras, etc., etc.). So the inverter runs 24/7; I long ago stopped trying to save a few amps by turning it on and off. I charge my own phones and computers with DC chargers hardwired at the nav table; but once you get up to several other people on board which means a dozen or more devices to charge, it becomes impossible and you just have to let people plug into regular outlets.

Could we have a bit larger battery bank? Certainly; I wouldn't mind it. Power is here again like money -- however much you have, a little more would always be welcome . What would be fabulous would be a batter bank of about the same nominal capacity, but LiFePo, so it would have nearly twice the usable capacity. But do I need it? No, not at all -- our present setup fulfills all needs and does not produce any inconvenience at all.

Yes, all fine, I agree.
I actually did not mean to exclude generators as some use this as a part of their balanced system.

[Dockhead]

Originally Posted by Fuss

Yes, all fine, I agree.
I actually did not mean to exclude generators as some use this as a part of their balanced system.

A generator, especially a heavy-duty low-speed diesel generator, is so far still the best way to produce largish quantities of electrical power on a sailboat.

Downside is that it uses fuel so costs money and eats into fuel supplies you might need for propulsion, and to varying degrees produces noise and vibration. Another downside is that it keeps using fuel and making noise and vibration even if you only need a little bit of power, like when you're trickle charging your batteries that last bit -- so extremely inefficient for low-demand situations.

But still, a low-speed diesel generator plus a good sized solar array is just about an ideal supply system for a boat which needs a fair amount of power. Solar alone is even much better if you can use little enough power or have enough solar cells to have a reasonable balance of production versus consumption.

I personally have very bad experience with wind power, but YMMV.

[valhalla360]

I'd much rather do some preliminary calculations than find out 3 days in the engine won't start because the batteries are dead and we need to get a jumpstart.

At the very least if I'm testing the system, I want to be able to keep an eye on the batteries to see what is using up the power, so I'm not covering the guages.

In reality, this doesn't apply to us as we can pull start the engine easily and we have a portable generator available.

[Dockhead]

Originally Posted by valhalla360

I'd much rather do some preliminary calculations than find out 3 days in the engine won't start because the batteries are dead and we need to get a jumpstart.

At the very least if I'm testing the system, I want to be able to keep an eye on the batteries to see what is using up the power, so I'm not covering the guages.

In reality, this doesn't apply to us as we can pull start the engine easily and we have a portable generator available.

I think this doesn't apply to the great majority of cruisers, who will have separate engine start batteries.

[valhalla360]

Originally Posted by Dockhead

I think this doesn't apply to the great majority of cruisers, who will have separate engine start batteries.

That assumes they don't accidently leave the combiner switch on...which is a common mistake for a newbie to make.

I still stand by my statement that at least a brief review makes more sense than finding out a few days in that the batteries are dead and you wind up spending time and effort addressing the issue in a potentially inconvienent location.

I'm not saying you need a detailed analysis with a 50 page report but taking an hour to rough out an estimate of your consumption and capacity makes a lot more sense than going out in an unfamiliar boat and hoping it works out.