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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
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  #21  
Old 03-28-2008
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No PLUMP...you are wrong. Trickle charging on a 12V battery takes place at low AMPS...not low voltage. To get amps to flow into the battery you must be above resting voltge of 12.7...You will see the float setting on regulators for wet cells is at 13.3 Volts. In a trickle charge situation you may only be putting in 1/2 an amp but it will be at 13.3V. Any excess energy is bled off in heat rather than electricity.
Your digital volt readout may indeed be showing 14.1-14.6...but amps will be adjusted to reflect a maximum of 48 watts. The physics are simple:
AMPS times VOLTS= WATTS. You know watts are max 48...so whatever volts you are operating at absolutely limits the amps you can input.
The days up by you do get longer in the summer but the sun is lower on the horizon so there is an offset angle there that you must take account of AND atmospheric interference at low angles of incidence REALLY detracts from power. Furthermore...I am talking about averages...and of course you pay for your extended summer sunshine with extended periods of darkness so the average doesn't change anything over time.
Anyway...believe what you want or go read the entire solar wind thread again and the articles that have been cited that delve into this topic with hard data. I have tried to be helpful to you...but believe what you want to.

HS...you beat me to it. Thanks for the independent verification.
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  #22  
Old 03-28-2008
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This still doesn't add up for me. The voltage is being metered at a 12v plug in inside the boat. The 48w self regulating panel is also run through another regulator and hard wired to one battery which is combined with another via a combiner switch. (standard A both or B switch) If I measure the batts in the dark separately I get 12.6v. If I measure them separately during daylight, I get a charge (normally well in excess of 13.3) on the battery that is hard wired to the panel and 12.6 one the other. When I combine them I get the higher voltage reading. Although my consumption is low, I honestly think it is more than 15 amps per day (your estimate) and my panel seems to always keep my batts topped up just fine. One of my lazy lying around the boat things to do is watch the juice start to flow from the panel right as the sun pokes its head over the horizon.
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Old 03-30-2008
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I don't want to drag anything off-topic, but I feel like I am misunderstanding something somewhere and wanted to see if someone could clarify.

When you are talking about charging voltages, are those with the panels connected, or unconnected? I just got a little 2W trickle-charge panel to keep things topped off, and in good sun I measure the output straight from the leads at 17v - 20v. As soon as I attach it to the battery bank, I see the overall voltage in the system read whatever the batteries were putting out on their own.

I understand that you need a higher voltage going into the system to charge the batteries, but it's not clear to me if that's happening or not. When you are talking about the 13.3v, is that what the panels must be producing independently, or is that the level to which they have to energize the entire sytem when they are connected in order for any charge to apply?

I ask mostly because the trickle charger doesn't seem to be working; if I leave it hooked up for a day, the overall voltage reading in the system seems to be lower at the end of the day than it started out (this is without going into darkness at all; the panel has a regulator which is supposed to prevent it from bleeding juice out of the system at night, but I eliminated any potential problems with that component by only connecting and measuring during daylight hours).

If it's the case that the panel has to bring the whole system up to 13.3v to charge, then how exactly do small trickle chargers ever work on larger battery banks? I've only got ~200AH of capacity in my house bank but it doesn't seem all that large, and they market these trickle chargers as being able to keep your car, boat, or RV 'topped up' when not in use. I'm confused as to how that happens, I guess, or if it's simply untrue and you need really massive panels to see any sort of charging at all.
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"More on solar panels" ??????

Is it possible that there can be more on solar panels than is posted here: effectiveness of solar & wind

Please read this thread first and then, if your question is not answered, consider the services of Dr. Jack.

There is no "more" on solar panels. In fact there's already enough on solar panels to bring Evelyn Wood to her knees. Please help stop the madness. Countless souls sacrificed marriage and the opportunity to see their children grow up before their eyes to publish this link on solar panels. And they are just crazy enough to do it again. That link again is: effectiveness of solar & wind. My advise is to cancel your plans to launch the boat on Memorial Day, you're gonna be busy until at least the 4th and maybe Labor Day.

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Old 03-30-2008
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"If it's the case that the panel has to bring the whole system up to 13.3v to charge, then how exactly do small trickle chargers ever work on larger battery banks?"

At a certain point, they don't. A trickle charger needs to exceed the voltage of the battery, and to supply sufficient amperage. For a Group27 battery, 30-50 milliamps may be enough. For a pair of T-105s, that will not be enough and you may need a 250mA charger to trickle charge them. (I'm not looking up the exact figures.)

The charger--any charger for any system--must be matched to the system requirements, or it will either undercharge or overcharge or waste a lot of money.

"When you are talking about charging voltages, are those with the panels connected, or unconnected? " The only numbers that matter are "connected" with the device in circuit and under load. That applies to solar panels and chargers of all types, alike.

It is also possible that your trcikle charger would be fine--but your batteries are old and sulphated, and they will no longer accept the charge the way they should. In that case, if you test the batteries without a load, you will only read the "surface charge" on the cells, and that drops dratically as soon as you put them under load. Or, if they are allowed to sit for 24 hours without any charging, and distribute the charge internally. (Yes, a charge may have a physical "location" in a wet cell, as the electrolyte and ions slosh around and migrate through the plates, or not.)
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To maybe put it a bit more simply...even if your batteries are discharged to 12.25V (50%) and your 2W panels tries to deliver current at 12.5V...it will only develope less than .2 amps. Given a 5 hour direct sunlight equivilent...this means that over a day..less than one amphour will be stored in your battery. If the bilge pump kicks on, or your radio memory or TV standby function is on you will probably use more than this...hence the lower readings at night. Furthermore...on a 200 amp bank of wet cells..the self discharge rate can easily be in excess of 2 amps per day.
So...briefly...a 2 watt panel is a waste of time and money. Try 20 watts!
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Quote:
Originally Posted by sailaway21 View Post
Is it possible that there can be more on solar panels than is posted here: effectiveness of solar & wind

Please read this thread first and then, if your question is not answered, consider the services of Dr. Jack.

There is no "more" on solar panels. In fact there's already enough on solar panels to bring Evelyn Wood to her knees. Please help stop the madness. Countless souls sacrificed marriage and the opportunity to see their children grow up before their eyes to publish this link on solar panels. And they are just crazy enough to do it again. That link again is: effectiveness of solar & wind. My advise is to cancel your plans to launch the boat on Memorial Day, you're gonna be busy until at least the 4th and maybe Labor Day.

Don't make me come back here!
I am not sure I understand why folks can't discuss things even if they have been discussed by others before. You seem to spend a lot of time telling people to go away and read old discussions. Why can't they ask questions and discuss anew? There are only so many things regarding sailing to talk about. That is why magazines print articles about the same things over and over again. That is life. If you have already learned all you can, why don't you just not read the thread? Why do you persist in telling people to read the history when all they really want to do is chat about something interesting?
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I did a double check on my batts and panel today at 10:30. It was a typical cloudy greyish Victoria March day and my meter was reading 14.2v in. I don't understand why your figures and my experience differ because you seem to be able to talk about this pretty fluently. I wish I new more about the subject. My batts and panel seem to work very well together and keep me in juice (with my low demand) indefinitely.
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Plumper...I will try one more time.
You did not give both VOLTS and AMPs taken at the exact same time.
If you do that and are using accurate instruments and measuring properly...then you multiply them together the result will never be more than 48.
It is physics and OHM's law...you don't get to play around with that in this particular universe!!

As to sailaways remarks that you object to. This topic has been totally dealt with before in somewhere around 1000 posts where we did a lot of research, have excellent links and which provides an excellent grounding in the subject. I have better things to do with MY time than to provide the same high quality and throughly researched answer to the same question posed by newcomers who were not present for the first go round. Thus we provide a link for YOUR benefit instead of ignoring you.
If you have questions about what you read on the link or think of new ones, we welcome the opportunity to help. But don't ask me to re-write war and peace every time someone new asks the same question.
Do your homework before you ask for further help when given a reference link.
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Quote:
Originally Posted by Plumper View Post
I am not sure I understand why folks can't discuss things even if they have been discussed by others before. You seem to spend a lot of time telling people to go away and read old discussions. Why can't they ask questions and discuss anew? There are only so many things regarding sailing to talk about. That is why magazines print articles about the same things over and over again. That is life. If you have already learned all you can, why don't you just not read the thread? Why do you persist in telling people to read the history when all they really want to do is chat about something interesting?
The thread I referred you to consists of one full year of daily postings on the topic of solar power. There are over 1100 posts within it, some quite useful.

If someone handed you a copy of Bowditch would you ask them to explain what an azimuth was before even cracking open the bible of marine navigation that they've just given you? And it's not like you had to go out and buy it or wait for it to come in the mail. The information is right at your finger-tips.

You'll have noticed that I posted in the GPS/Sextant thread because I thought there was new information of some relevance. I did not bother repeating my past, and lengthy, previous postings on the matter.

Some people seem to thrive on answering the same questions every other week here. I prefer to refer people to far better answers than I can perhaps provide and answers I've found helpful in the past. It's much easier to have that interesting conversation you're talking about if everybody is up to speed on the topic. (as in the recent posts by Cam on new battery technology in a thread whose name I don't have handy)

I tend to think I'd be doing you a disservice by not referring you to that solar thread. Hellosailor has done yeoman service in researching and testing many components and his knowledge, among others, is contained in that thread. You or I may have questions on some of the things in that thread and it'd be nice to think that people like Hellosailor would still be available to answer those points of confusion and not be burnt out on reanswering the same old questions. But that's just my opinion.

btw, a lot of people do not know that there exists a voluminous series of articles, many written by those writers you see in the sailing mags, within sailnet. They're left over from the previous incarnation of sailnet and contain an amazing amount of information. I've spent hours paging through them. You can talk about Fastnet here on sailnet with somebody who's never gotten past the sea-buoy or you can read what John Rousmaniere, who was actually there, has to say about it. Were you aware of their existence?
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