Actual power budget of cruising monohull?

[robert sailor]

Originally Posted by Paul L

I set my solar reg to the specs I got from Rolls for my AGMs. I wouldn't characterize those as aggressive or conservative. Just what the manufacturer suggests. I don't consider all daylight hours as 'a short period of time'.

I really wasn't aware that a batt that transitions at the correct acceptance amps/volts to Float is only at 90% charge. If this is true, then I am not getting to 100%.

I wouldn't worry about it, your Rolls batteries are top of the line and have a great reputation, using modern methods to charge them will give you umpteen years of use. I think we are starting to pick fly **** out of pepper

[a64pilot]

Originally Posted by Paul L

I really wasn't aware that a batt that transitions at the correct acceptance amps/volts to Float is only at 90% charge. If this is true, then I am not getting to 100%.

It may or may not, easy to tell though just watch charge rate prior to tripping into float, yours may be getting you right to where you want to be.

[Paul L]

Originally Posted by a64pilot

It may or may not, easy to tell though just watch charge rate prior to tripping into float, yours may be getting you right to where you want to be.

transitions at the correct acceptance amps/volts to Float was the conditions I was referring to.

[noelex 77]

Originally Posted by Paul L

I really wasn't aware that a batt that transitions at the correct acceptance amps/volts to Float is only at 90% charge. If this is true, then I am not getting to 100%.

This is quite common, perhaps even universal for boats at anchor so is not a cause for concern.

If you have Rolls wet cells the effect on battery life is only slight. If you have Rolls AGM batteries charging them to a true 100% occasionally is more important, but this very difficult to achieve at anchor.

The only practical way to obtain a true 100% charge is when connected to shore power (or wind if you have powerfull wind generator and consistent breeze) so if you have AGM batteries hook up to shore power even if solar is keeping up demand. The positive charging rate over say 24Hrs or more will raise the SOC to 100%.

Rolls batteries are very durable but an occasional true 100% SOC helps battery life especially for AGM batteries.

[Oceanride007]

At Anchor. My Solar often cuts into float around 10am, and it may oscillate between bulk and float many times due to load (power tools, charging other stuff) and cloud cover. I have seen 4 amps going into batteries in float late afternoon, so at best guess my SOC is at 90%. Now I know that my battery bank is way undersized and often I have to make a decision about having ice blocks that night or watch TV. Not both. Yet there is heaps of underutilized solar in the afternoon, due to the limitation of battery acceptance.

The important measurement to me regarding spread sheets is to measure the Amp hours between sundown and sunup to ensure my bank does not go below 50% by the morning (Assumed to be 12.2Volts at near zero amps). If I anticipate I don't have enough, on goes the Engine (hate that).

Of course I do not want a Voltage meter ruling my on board life, but it is important to understand my priority, be it, up the Battery or Solar or Wind or Honda or Amp Counter, but a tricky one is installing that first Solar panel as you need to get the sizing right, I have 2 now, room for another, but too late (without expense) to up the size to longer narrower and get more watts. Solar panels on a given string must be the same size if in series, which I prefer.

Night sailing, I will use my shaft generator. Day sailing I find I have plenty of excess solar to drive the AP.

[a64pilot]

I don't get the 24 hours to full charge? At least Lifeline says your fully charged when your at .5% of the banks AH rating at absorption voltage.
Mainsail achieved that at 5 to 6 hours with big chargers, longer of course with smaller charge rate, but not 24 hours unless your on a trickle charger?

Way I understand it, if your at the battery manufacturers stated charge rate for full at absorption voltage, your fully 100% charged. Example I'm a 660 AH bank, Lifeline says .5, so for me at absorption voltage that is 3.3 amps.
Is this wrong? Have a reference?

[a64pilot]

Originally Posted by Paul L

transitions at the correct acceptance amps/volts to Float was the conditions I was referring to.

Then you are fully charged, unless there is something I don't understand, but it seems real clear to me.

[Davidhoy]

So much good info here, thanks everyone! I do realize that a power budget is just a starting point, no more.

To answer a few of the questions raised:
* I do have a backup charging source, an 8kw Northern Lights diesel genset. My goal is to reduce my dependence on it, and fossil fuels in general, to an absolute minimum.
* I have a 420 aHr main bank, 4x group 31 FLA batteries, install new in September after my boat was hit by lightning.
* There is space to fit 3x 40" wide solar panels on a bimini-like structure over top of my dinghy davits. Based on panels I've seen online I could get over 1000 watts of solar up there.
* My refrigeration system, currently 110v AC water cooled, consists of a 5cuft freezer box with 3 holding plates and a 14cuft fridge box with a single plate. The plan is to change this over to 12v DC.
* I do have air conditioning, but only expect to use this on generator or shore power.

My hope is to install enough solar to charge the batteries, and then use excess power in the afternoon to make water, continue to chill down the refrigeration, maybe even make a little bit of ice for evening cocktails. Longer term I can look at increasing the house bank size too.

Am I on the right track?

[Paul L]

Originally Posted by Davidhoy

So much good info here, thanks everyone! I do realize that a power budget is just a starting point, no more.

To answer a few of the questions raised:
* I do have a backup charging source, an 8kw Northern Lights diesel genset. My goal is to reduce my dependence on it, and fossil fuels in general, to an absolute minimum.
* I have a 420 aHr main bank, 4x group 31 FLA batteries, install new in September after my boat was hit by lightning.
* There is space to fit 3x 40" wide solar panels on a bimini-like structure over top of my dinghy davits. Based on panels I've seen online I could get over 1000 watts of solar up there.
* My refrigeration system, currently 110v AC water cooled, consists of a 5cuft freezer box with 3 holding plates and a 14cuft fridge box with a single plate. The plan is to change this over to 12v DC.
* I do have air conditioning, but only expect to use this on generator or shore power.

My hope is to install enough solar to charge the batteries, and then use excess power in the afternoon to make water, continue to chill down the refrigeration, maybe even make a little bit of ice for evening cocktails. Longer term I can look at increasing the house bank size too.

Am I on the right track?

You need to come up with an energy budget. How many amp-hours, on average, while at anchor will you use in a day. That reefer setup is going to burn a fair amount, especially if you plan to be in the tropics. Can you shrink the size of the reefer with some interior insulation to get the draw down?

[Oceanride007]

If you have generator run it to topup and make water enjoy the conveneience of AC power.
Making water people have 2 camps, one frugal, plenty of Solar the other camp is generator. Just a observation but it does appear this argument is favoring the Generator group. You already have a Generator suggest you use it.

[SV THIRD DAY]

Two things you can never have too much of on a cruising boat:

Power and Time.

[tomfl]

Originally Posted by Davidhoy

SNIP

* I have a 420 aHr main bank, SNIP

* There is space to fit 3x 40" wide solar panels on a bimini-like structure over top of my dinghy davits. Based on panels I've seen online I could get over 1000 watts of solar up there.
SNIP

My hope is to install enough solar to charge the batteries,SNIP

Am I on the right track?

400-420 watts should be plenty to charge your battery bank if the rest of the system is set up right; as long as your are not using more than around 200 amps once it gets dark and the solar is no longer charging. As more than one person has posted here the key to a long lived working system is not killing your batteries by draining them every night. Some of the newer non flooded batteries can be run down more but the 50% rule is a good one.

As other posters have said your fridge may need to be replaced or more insulation added. AC is also a killer in terms of draining the batteries if it is used at night. While getting a good marine fridge system may seem expensive if you are living on the boat it will pay for itself if you have to upgrade/replace the battery bank and solar array. Some marine systems have a card that can be installed which will turn on the compressor at 25% for the first five minutes, then 50% for the next five minutes, then 75% for the next five minutes, and finally 100% if the first 15 minutes has not gotten the fridge to temperature. This not only saves on power which means the batteries should last longer, but also reduces wear and tear on the compressor which means it should last longer as well. Not sure what fridge you have but I doubt it will be a long term solution for anything but having shore power.

While not all cruisers/live aboards have this problem if you have to replace your battery bank/solar array/fridge system in a third world country the importance of having your systems last as long as possible is important. Even for those who will seldom be away from shore power replacing things on a boat can get expensive.

[StuM]

Originally Posted by tomfl

400-420 watts should be plenty to charge your battery bank if the rest of the system is set up right; as long as your are not using more than around 200 amps once it gets dark and the solar is no longer charging.

If he is using 200 Amps once it gets dark, his nominal 420Ah battery bank will be completely dead in less than 2 hours.

(See what happens when people don't use the correct units? )

Assuming that you meant using 200Ah overnight, 400W is not going to replenish that the next day, even if he has no daytime draw. He's going to be lucky to consistently get 150 Ah per day out of those panels.

[admiralslater]

I am in Bequia at the moment and at my link 10 when I started to read this thread .At 5 atlantic time the sun is quite flat so we were in the discharge faze of the day.
I was drawing a net -3 amps with 97 % of capacity left . At 9 am I am putting in net 10 amps having taken down the batteries to 83% overnight.
I run a frigoboat deep freezer,beat up Isotherm fridge and an engle cooler in the cockpit.
When my wife is here we use a toaster and a hair dryer of a VictronConnect inverter .we also have the usual phones etc.
For charging the boat has 590 watts of solar running through bluesky mppts to 525 amps of Firefly carbon batteries.
I almost forgot new electric head this year. As you can see I am not shy about using the juice and I have not been plugged in for two weeks. I don't use the engines to charge at anchor but there was 3 hours of motoring in that time .
The effectiveness of my system was a surprise to me and I think it comes down to the batteries ,their ability to accept high rates of charge allows the rate of power usage that I have . I have only the stock alternators on my engines with Balmar regulators ,we had to motor the other day first thing in the morning and I check the link and I was putting 50 amps in and an hour later it had not change much.
The long and short is that this system lets me use a hundred amps in the non solar periods with out effort .
I accept that the Caribbean makes solar very viable and that what I can achieve here may not work in other areas

[StuM]

Originally Posted by admiralslater

For charging the boat has 590 watts of solar running through bluesky mppts to 525 amps of Firefly carbon batteries.

That would be 525 Amp hours.

The long and short is that this system lets me use a hundred amps in the non solar periods with out effort .
I accept that the Caribbean makes solar very viable and that what I can achieve here may not work in other areas

And that would be 100 Amp hours.

Jusr like Tomfl's case, if you use 100 Amps, you will drain your 525Ah bank in a few hours.