A way To Save Charging Time

[Fuss]

Originally Posted by Kenomac

To answer a couple of the prior posts, here's the nagging daily anchorage problem I'm looking to solve.

The first day out the batteries are charged to 100% and I have a full 377Ah and usable 188Ah. 50%

Day #2, the generator will only bring the batteries up to 95% despite 3-4hrs of run time on the previous 50Ah charging system.

Day #3, the genset can now only achieve 90%

Day #4 84%

Day #5 82%

Etc. etc. etc.

Until the end of week #2 when I'm eventually down to 75% or so max and using a very narrow battery capacity between 45-50% and 75-80% until I do a long motoring trasit or plug in to shore power.

Will solar solve this?

Will solar solve this?...not sure yet, but I would suggest the following....

At the moment you have added an additional 75ah of battery charging that you say has made a significant difference so why not see how this is working over the next week before committing to the 450w of solar.
For sure, as the solar is planned to be installed under the boom on the bimini, it won't give you the 100ah a day contribution that I originally said.
It will be less.
After the next week, send us another post like your last post with the new figures using the additional 75ah that your new charger is contributing during generator run times.

Then see what to do with the solar.

....another thought as you are probably going to spend 3000 euro with the solar guy, ask him to bring the 450w Array and mppt controller and place them temporarily on the bimini under the boom and see how many ah they produce at midday with the boom shadow.

No shade would give you around 13ah maybe.
If they contribute more than 9h and the install looks like it would be very nice and have no big downsides and be generally invisible, then its probably worth buying them.
But tell him you will decide in a week after testing the changes with the new 75ah of charging.

[Sailmonkey]

Originally Posted by Kenomac

My best guess is 80-100Ah during the day. I'll turn off the shore power first thing tomorrow morning after breakfast and have an answer tomorrow night. I'll have a six hour number for you in about... six hours.

Cool, that will help clarify this whole thing.

[Kenomac]

Fuss and Sailmonkey,

Great ideas.

Tonight around 8pm Italian time, I'll have figures on the Ah consumed during the day primarily from refrigeration. I'll then charge up via genset. Will do the same thing tomorrow and the next day to find out the fall off figures on the genset being able to bring the batteries back to a full charge.

Many thanks

Ken

[barnakiel]

I think a big downside of genset / solar combo is you would want to start the genset at the lowest point and before the solars kick in. This lets you use the genset to push thru all or most of the bulk.

BUT this seems to be early morning on most boats - before the sun is up. There is no problem to start the genset auto (say at 05) except that maybe only a small Panda somewhere in the lazarette is that silent. Many onboard owners my be shy to start their gensets say at 05:00 LT.

Starting the genset early morning (if you get up at 06 or 07, I do not) is second best.

b.

[Kenomac]

Originally Posted by barnakiel

I think a big downside of genset / solar combo is you would want to start the genset at the lowest point and before the solars kick in. This lets you use the genset to push thru all or most of the bulk.

BUT this seems to be early morning on most boats - before the sun is up. There is no problem to start the genset auto (say at 05) except that maybe only a small Panda somewhere in the lazarette is that silent. Many onboard owners my be shy to start their gensets say at 05:00 LT.

Starting the genset early morning (if you get up at 06 or 07, I do not) is second best.

b.

We would typically run the genset from 8-9:00am each day during the summer, then again around supper time 7 or 8:00pm for around a half hour while cooking. Not looking to reduce this genset run time of 1.5 hours or slightly less, just the additional two hours per day that is needed on most days, usually between 9-11am.

[sailorboy1]

I already posted that running the generator 9n the morning for about 1 hour allows my 290W of solar to get the batteries to 100% most of the time (less than 0.5% amp acceptance at absorption voltage). That is when we are on the boat living. If off the boat, with the freezer and refrigeration running, the solar gets there on it's own.

[weavis]

My nephew is playing with positioning the 100W panel on the Centaur. He told me that a lot of power is lost if shaded in any way... He is thinking of having it movable so as to maximise the weak light in the Uk

Check that your positioning maximises light input Ken...

[Sailmonkey]

Originally Posted by Kenomac

We would typically run the genset from 8-9:00am each day during the summer, then again around supper time 7 or 8:00pm for around a half hour while cooking. Not looking to reduce this genset run time of 1.5 hours or slightly less, just the additional two hours per day that is needed on most days, usually between 9-11am.

Imho, depending on what your pulldown today reveals, and with your additional battery charger, I think the solar will allow you to maintain full charge with your cook time runs of the generator.

Unless your daily consumption is insanely high........but the solar will still extend the time needed between a dockside charge.

[Kenomac]

Originally Posted by mrm

While I like simple, oversimplification is not good. How can you be sure of your answer without knowing what the continuous drain on the bank is? Knowing the panel wattage and location gives an approximate answer to how much energy is produced daily, but how much will be stored in the bank (if any at all)? How can you tell without knowing the energy budget of that particular boat?

Some of these mysteries now have numbers.

During the day with only the stereo turned on the drain is 1.5Ah, when the freezer compressors turn on with the associated water pump, the drain increases to a total of 11Ah on the meter for 10 minutes, then drops back to 7Ah. The fridge draws 3Ah on start up, then drops back to 2Ah. When both units are running at the same time, the total draw is 9Ah continuous after they settle in when combined with the stereo.

The fridge runs 5-6 hours per day (24hrs) and the freezer 4-5 hours per day. Each runs at least 3-4 hours during the daylight hours, less at night.

It's beginning to look like our boat is more energy efficient that I thought, although the energy consumption will certainly increase by 50% during the hot summer months.

Another Solbian factory direct quote just arrived in at €2500 for 450w excluding installation, which I think we can handle ourselves.

[Kenomac]

Originally Posted by sailorboy1

I already posted that running the generator 9n the morning for about 1 hour allows my 290W of solar to get the batteries to 100% most of the time (less than 0.5% amp acceptance at absorption voltage). That is when we are on the boat living. If off the boat, with the freezer and refrigeration running, the solar gets there on it's own.

Can you please remind me where your solar panels are mounted? My only choice is the top of the bimini.

[SeaSon]

Originally Posted by smac999

We often install ~200a of charging on boats (12v).

The gen should always be maxed out while running. Or you are wasting time and fuel.

The gen will only get the batteries up to 85-90%. Though unless you run for 5+ hours. So unless you plug into a dock at least once a week. Solar is still highly recommended otherwise your batteries will suffer . But you could probably do with less now.

Agreed. I found using my 80A charger/inverter that it was more effecient and effective to run the gen set twice a day vs once a day for 2.3x longer. I'd shut down once charge current dropped to 50 amps on my 420ah bank. This appeared to take the bank from about 60pct to about 85 -90 pct based on the ah counter each charge.

[a64pilot]

Originally Posted by senormechanico

Interesting.
That's basically what we get in the PNW in the summertime on nice days with 440.

Your way North, but I think also during the Summer, you have some really long days to make up for it.
Your Winter numbers I bet are bad though

[mrm]

Originally Posted by Kenomac

Some of these mysteries now have numbers.

During the day with only the stereo turned on the drain is 1.5Ah, when the freezer compressors turn on with the associated water pump, the drain increases to a total of 11Ah on the meter for 10 minutes, then drops back to 7Ah. The fridge draws 3Ah on start up, then drops back to 2Ah. When both units are running at the same time, the total draw is 9Ah continuous after they settle in when combined with the stereo.

The fridge runs 5-6 hours per day (24hrs) and the freezer 4-5 hours per day. Each runs at least 3-4 hours during the daylight hours, less at night.

It's beginning to look like our boat is more energy efficient that I thought, although the energy consumption will certainly increase by 50% during the hot summer months.

Another Solbian factory direct quote just arrived in at €2500 for 450w excluding installation, which I think we can handle ourselves.

OK, so roughly, in summer months, consumption during daytime:
fridge+freezer+stereo: 9A * 13V * 6h = 702 Wh


Now the production side. Assuming horizontal mounting with unknown shading one can roughly estimate to get 65-70% of rated panel power, for 5-6 hours per day. Erring on the side of caution, production estimate is:

450W * 65% * 5h =~ 1460 Wh

Net balance available for charging: 1460 - 702 = 758 Wh

If I remember, your plan was to do bulk charging phase using generator and once absorption is hit continue with solar?

[Kenomac]

Yes, that is correct.

[mrm]

Originally Posted by Kenomac

Yes, that is correct.

So, given your bank size (377Ah), the bulk/absorption transition point is
37.7A at 14.7V (maybe 14.5V? check your battery spec). The absorption to full is holding voltage (14.7V) till current drops to 0.5% of C20 (<2A).

Modeling this as a linear current drop over time and estimating the whole process to take 5 hours, the energy requirement is:

14.7V * (37.7 + 2)/2 A * 5h =~ 1460 Wh

without accounting for charger inefficiencies. Seems way above your net energy budget, but likely the linear current drop model is wrong. MaineSail? Help?