CaliMobber
Adventurer
Yup solar can handle just about everything you need but A/C and a microwave. Thats the moral of this thread. 
why generators are bad battery chargers
- Thread starter Mwilliamshs
- Start date
pugslyyy
Expedition Vehicle Engineer Guy
Yup solar can handle just about everything you need but A/C and a microwave. Thats the moral of this thread.
That's certainly my experience.
jodygraham
New member
Actually, transformers don't "transform" AC into DC. A transformer simply increases or decreases the amplitude of an AC output with respect to the input.
You then use a diode rectifier to convert the AC into DC and then smooth it with a couple of inductors and/or capacitors. It's really not that complex - the article grossly misrepresents the process of converting 120VAC->12VDC.
This is a better illustration (230VAC->5VDC but you can get the point from it)
I don't see how this article grossly misrepresents the process of converting 120VAC to 12VDC. If you took the time to read a few paragraphs down you would read...
"Next, the 12 volts AC must be rectified to DC using a single phase rectifier."
The article also does not state that a transformer magically "transforms" the 120 VAC to 12VDC. Nowhere does it say that, nor did it. A transformer simply changes the amplitude (most of us call voltage) as you correctly stated. It does nothing to the waveform.
It is so easy to criticize someone's work but at least read it all first. Many times I have read an article on a website and thought "what a stupid mistake that author made" or " that statement is completely false" only to read it again or look at the context and realize I was the dummy, not the author.
What really bugs me is someone from a forum will quote something incorrectly about someone's website and all of a sudden there are many on the same forum criticizing the website without out even taking one minute to be sure it was the webpage that is wrong, not the forum poster.
There have been a few changes made to the webpage in the past day or so but not to try and hide any mistakes, just to make things a little easier to understand.
Please show me on the article where "the article grossly misrepresents the process of converting 120VAC->12VDC".
As well, for everyone who reads the article, the purpose is to help folks who operate larger off grid homesteads with large battery banks, not a small RV battery or similar.
When you have a large bank of large solar batteries, charging them with an automotive 3 phase alternator (and bridge rectifier) coupled to a fossil fuel engine is much, much more cost effective than using a 120/240 split phase fossil fuel generator. There is no question about it. I have used both types personally and installed many as a professional solar installer.
I hope I do not come off as negative or angry but I hate it when someone's work is criticized without being looked at.
Cheers!
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pugslyyy
Expedition Vehicle Engineer Guy
1. Welcome to Expo. You used your first post to criticize an electrical engineer on his home turf.
2. I did read the entire article.
3. My commentary was accurate.
4. You have no idea what you are talking about.
Good day.
Mwilliamshs
Explorer
FIFY, JonJon
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Jodygraham, welcome to expo, for real this time. Keep posting. We're not all as touchy as the marathon maniac above.
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pugslyyy
Expedition Vehicle Engineer Guy
Knowing what I'm talking about apparently makes me a god on this thread. I'm okay with that. Can I be Loki?
dwh
Tail-End Charlie
Sorry, but no you can't be Loki. Or Kokopelli, who is the same guy just using an alias while on tour.
You can be Ptah or Heh - I don't think those are taken.
jodygraham
New member
Thanks so much for the real welcome Mwilliamshs. I thought this forum was a place to ask questions and figure things out together. But there always seems to be the same insecure people on every forum. I have only had a few real world experiences with electrical engineers and they were negative. Theory is useless when you can't wire a light switch. I am sure they are not all like that. Most have forgotten more than I will ever know.
I will tell this story though. A few trips ago to Haiti I had an electrical engineer volunteer to "help" me install a solar pumping system for a small village (approx. 300 people) at the top of a mountain. I had to get the water up 2000 vertical feet over a pipe run of about 4200 feet. This fellow happened to a be a professor at a local university. He took my very crude drawings to his co-workers and all of them agreed the system would never work for three reasons.
1. The pipe I was using was too small (1/4" inside diameter but only needed 1/2 gallon per minute)
2. There was no return line for the water. I needed to have two pipes? Still not sure where that came from.
3. The solar modules were going to destroy themselves the first time the battery bank became full. I had a charge controller (Outback FM60) that disconnected the solar array from the batteries as they filled up. Their theory was that the solar modules would continue producing electricity until they destroyed themselves from the stored up energy. Wow!
I politely asked him to stay home as I already had plenty of help but he decided to come along anyway. After three days of hard work we had a gallon a minute flowing to the top of the mountain which might not sound like much but each family only uses 1 gallon per day. Keep in mind they had to climb to the bottom everyday and climb back up (4 hour round trip) carrying a bucket of water on their heads every morning of every day so they were used to conservation. One gallon a minute turned out to be 720 gallons per day as we were able to operate the pump about 12 hours per day with 4 Surrette/Rolls S530 530 AH (100 hour rate) and 1000 watts of solar. We had a custom made DC 6 stage piston pump made by Easy-Kleen a large pressure washer manufacturer. It operated at 960 psi. We used tiny plastic pipe (rated at 5000 p.s.i.) we sourced from a company that supplies the US military with piping/tubing they use to move water from place whether its in Alaska or Iraq.
Regardless the electrical engineer/professor came, did nothing but pose for photos and came home to tell everyone he designed and supervised the installation of a pump to help the people of Haiti. I finally figured out why he came. He used the trip to tell everyone (including our largest newspaper) how he designed a solar pumping system and supervised the installation so the crew would know what to do. He used these lies to raise over ten thousand dollars so he could fly first class to Haiti a few weeks later and do nothing like he did the first time. Haven't heard from him since.
I do have a poor attitude about electrical engineers as any of them I have dealt with think they are superior to the common man. I do realize this isn't fair as there are likely thousands of wonderful, intelligent, and down to earth electrical engineers.
I truly did want to know what was so wrong with that particular webpage as that is how I learn. I ask questions of people that are smarter than me.
Getting the following reply:
1. Welcome to Expo. You used your first post to criticize an electrical engineer on his home turf.
2. I did read the entire article.
3. My commentary was accurate.
4. You have no idea what you are talking about.
Good day.
did nothing to increase my intelligence but perhaps pugslyyy thinks I am too stupid to understand conversion from AC to DC. Telling me I had no idea what I was talking about was of no help to me and much more offensive than anything I posted. The illustration he originally provided was excellent (and yes I actually understood it) but it is a little heavy duty for the average dude who wants to charge a car battery or solar battery bank with a generator. Telling the average cottage/RV owner that the 120 VAC must have its voltage lowered by a transformer first and then be rectified to DC is enough for them to wrap their head around.
I will try not to hurt anyone's feelings and hopefully I can learn lots from this forum.
Hope everyone will forgive me for being so critical and wish everyone the very best in 2015.
DiploStrat
Expedition Leader
Fools Rush in ...
when folks are talking past each other.
The key post here is #3, by my buddy dwh. For most of us, the issue is not electrical efficiency, but rather amps per $ of fuel. Some points to remember in an RV/expedition camper/whatever. (These may or may not apply to an off grid house, etc.)
-- You probably have a mixed voltage load, that is, 12v lights and a 110v microwave, air conditioner, hair dryer, or whatever.
-- You probably need to be able to run your loads from either 12v or 110v.
-- You are probably using some combination of solar, motor vehicle generator (an alternator is a generator, just ask GM), and a stand alone genset powered by gasoline, propane, or diesel.
-- You probably have a battery bank of some (LARGER) size.
This means that at various times you are attempting to power your load directly and recharge your batteries. Unless you have a Lithium battery bank, you will find that the maximum charge rate of your batteries will drop faster than you expect, thus it will take much longer than you expect to fully charge your batteries. (Read up on surface charge, etc.)
Modern campers usually have an inverter large enough to carry the full load on battery (12v), provide around 100A of battery charge, and the ability to pass some 30A at 110v through a transfer switch. (FWIW, large inverter/chargers are about 85% efficient.) Older campers may have a smaller "converter" and may not be able to power their big 110v loads except by direct connection to a genset.
So, to go back to the original point, a genset is called on for two, often contradictory jobs:
-- Power a big 110v load and, assuming a large enough charger, fast bulk charge. This it can do at a reasonable cost in fuel. (Noise and insect repellence are other factors.)
-- Provide a small amount of power for an extended period of time to compete the absorb/acceptance charge of a battery bank. Here a classic, high efficiency genset will not perform well as its fuel consumption will be high. A less efficient, variable speed genset may, on the other hand do quite well.
In my case, I find 2x250A alternators connected to the vehicle engine to be more than adequate to substitute for a stand alone genset and I depend on solar for the long acceptance charge. For those times when the sun absolutely refuses to shine, I have to run the vehicle engine or use shore power. The number of times that this has happened has been low enough that I have never regretted the decision not to install a genset. If it became an issue, I would use one of the Honda or Yamaha variable speed units.
As will all of this, YMMV, but I believe that the points that I have outlined above are correct.
Full disclosure: I an not an electrical engineer and I do know a bit about Haiti.
when folks are talking past each other.
The key post here is #3, by my buddy dwh. For most of us, the issue is not electrical efficiency, but rather amps per $ of fuel. Some points to remember in an RV/expedition camper/whatever. (These may or may not apply to an off grid house, etc.)
-- You probably have a mixed voltage load, that is, 12v lights and a 110v microwave, air conditioner, hair dryer, or whatever.
-- You probably need to be able to run your loads from either 12v or 110v.
-- You are probably using some combination of solar, motor vehicle generator (an alternator is a generator, just ask GM), and a stand alone genset powered by gasoline, propane, or diesel.
-- You probably have a battery bank of some (LARGER) size.
This means that at various times you are attempting to power your load directly and recharge your batteries. Unless you have a Lithium battery bank, you will find that the maximum charge rate of your batteries will drop faster than you expect, thus it will take much longer than you expect to fully charge your batteries. (Read up on surface charge, etc.)
Modern campers usually have an inverter large enough to carry the full load on battery (12v), provide around 100A of battery charge, and the ability to pass some 30A at 110v through a transfer switch. (FWIW, large inverter/chargers are about 85% efficient.) Older campers may have a smaller "converter" and may not be able to power their big 110v loads except by direct connection to a genset.
So, to go back to the original point, a genset is called on for two, often contradictory jobs:
-- Power a big 110v load and, assuming a large enough charger, fast bulk charge. This it can do at a reasonable cost in fuel. (Noise and insect repellence are other factors.)
-- Provide a small amount of power for an extended period of time to compete the absorb/acceptance charge of a battery bank. Here a classic, high efficiency genset will not perform well as its fuel consumption will be high. A less efficient, variable speed genset may, on the other hand do quite well.
In my case, I find 2x250A alternators connected to the vehicle engine to be more than adequate to substitute for a stand alone genset and I depend on solar for the long acceptance charge. For those times when the sun absolutely refuses to shine, I have to run the vehicle engine or use shore power. The number of times that this has happened has been low enough that I have never regretted the decision not to install a genset. If it became an issue, I would use one of the Honda or Yamaha variable speed units.
As will all of this, YMMV, but I believe that the points that I have outlined above are correct.
Full disclosure: I an not an electrical engineer and I do know a bit about Haiti.
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228B
Observer
This is what I'm learning. I plan on using this very technique, but, say, once per week if boondocking for several weeks at a time. I will be using a solar charging system I've just finished building as the sole charge source for the rest of the week. The system is in a camp trailer and consists of a 100W (+100W for days of full cloud cover) PV array/charge controller/8AWG stranded copper/100Ah Group 31 Sears/Odyssey AGM combination, but I've installed an EnerSys/Odyssey (120V input) OMAX-50A-1B (that's a solid 50 amps for the bulk phase!) charger initially as a backup charging source, powered by my trailer's 120V shore input. Now I simply need to replace the Honda 1000i with a 2000W inverter generator and then I'll have it made in the shade. (with the panels in the sun! on 30', 10AWG extensions).
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This thread was pretty funny until it was trolled. Thanks for the great humor.