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Old 30-10-2011, 19:04   #31
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Re: Charge Cycle Generator

Quote:
Originally Posted by djmarchand View Post
Sigmasailor: Small alternators are typically no more than 50% efficient at turning horsepower into KW, thus the need for an engine more than two times the theoretical power.

Flyingcloud: Not to be too picky, but given the above, I suspect that you will burn more than 1 liter per hour, but no more than two.

I like the idea of DC generators, but a well designed AC generator, ie small, with a large charger and/or inverter can do the same thing. Some big inverter/chargers have a 150 amp charging spec and can recharge batteries quickly although they will take almost all of the output from a small genset. The AC charger does suffer from lower efficiency and poor power factor which will hurt it some in comparison to a pure DC generator, but AC generators are more efficient than DC alternators so it probably all washes out.

If you have any significant AC load like airconditioning then it makes sense to install an AC generator with a decent DC charging capability to quickly recharge your batteries.

David
Not sure why it takes twice the horsepower to operate a 275 amp alternator that likely that wont put out that many amps... do you have this backwards? My experience with three Kubota based builds ( two at 6hp and one at 12hp) is that the 6hp were lugged pretty well for the first 20 mins driving 125 amp alternators. The 12hp was definitely loaded with a 150 amp alternator. I like DC gen's, but due to heat you can really only pound in the amps for 20 mins or so. My 125 amp alts would put out just over 100 amps for just a few minutes, then gradually back off to 85 amps or so before kicking down.
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Old 30-10-2011, 19:40   #32
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Re: Charge Cycle Generator

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Originally Posted by foggysail View Post
Interesting! Don't want to re-engineer the wheel although some things I do wonder about when comparing an alternator against a well designed inverter/charger.

One that come to mind is the copper wiring resistance that has a positive temperature coefficient that means the hotter the wire gets, the higher its resistance becomes.

Balmar reduces their high current alternators as a the alternator temperatures increase.......so for example, a 200 ampere alternator is 200 ampere only when the alternator temperatures are not high. Just increasing the circular mils of the wire may not be the answer. Larger diameter (circular mils) is compromised by skin effect which forces current to flow nearer the outer surfaces of the wire. Skin effect is caused by the magnetizing field at a distance from the center of the wire.

Then there is the temperature in the bilge that governs how well the alternator can be cooled.

Hey, if it works for you, that is all that really matters.

Foggy
Good Points...not all products are equal.

My alternator is rated at 275 amps cold, cold = 75f, but when I tested this on a growler at 75 F, with full field, that amp out was well over 300 amps.

The manufacture hot rating on this alt is 250 amp at 90C.

BC the Balmar controller logs a lot of info, I know that after 20 min of run time my shunt meter reads 250 amps out and the Alt, temp is 80C, bat temp. is 21C.

I also know the manufacture rates my alt at continuous 113C or 235F, so I am well below.

I also spin my alt at 6000 rpm during bulk, and it's continuous speed rate is 10,000 rpm. My engine room temp. after 1.5 hrs run time is 98 F, I believe I can increase efficiency, and plan to add a sea water charge air cooler to the sound shield first ducted to the alternator, which should lower the the temp rise of the alt, as well as lower the air charge temp to the intake air for combustion.

The skin effect is a bigger issue on High HZ transmission, as opposed to the dc side, as there isn't time for saturation.

Lloyd
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Old 31-10-2011, 07:20   #33
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Re: Charge Cycle Generator

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Originally Posted by FlyingCloud1937 View Post
Good Points...not all products are equal.

The skin effect is a bigger issue on High HZ transmission, as opposed to the dc side, as there isn't time for saturation.

Lloyd
Well you got me on High HZ transmission. Are you referring to high impedance transmission lines? But the reason I mentioned the skin effect was for the ac found in the stator. Obviously, a DC condition has no skin effect loses.

But like I said, if it works for you, that is all that matters.

Foggy
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Old 31-10-2011, 10:59   #34
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Re: Charge Cycle Generator

Quote:
Originally Posted by foggysail View Post
Well you got me on High HZ transmission. Are you referring to high impedance transmission lines? But the reason I mentioned the skin effect was for the ac found in the stator. Obviously, a DC condition has no skin effect loses.

But like I said, if it works for you, that is all that matters.

Foggy
Hi Foggy, Yes

I was confused...but I think I get your point now. The current alternator is not in theoretical mode, as it is installed and has 20 hrs run time, so we are dealing with real numbers.

I thought you were referring to my earlier post.

Quote:
Originally Posted by FlyingCloud1937 View Post
Hi David,

I have version 2 in testing right now, it uses the same alternator, but with custom wound stator, that put's out 240v 3 phase, which goes to a torrid buck transformer, and then into a rectifier. In this configuration it runs close 90% at the alt, with the associated transformer losses, and rectifier it should be north of 80% end to end. It does about 5kw cold.
Now this alternator has only run on the test stand. The design purpose of this is threefold.
1. Higher output from the same form factor, it operates at close to 90% eff.
2. it gives the option of Inverter/generator/Charger as the alt output goes to a remote mounted transformer/Rectifier.
3. The biggest reason, is the generator can be mounted up to 50 feet from the battery bank, the power is transmitted on the 3 #6 cables as opposed to 4 4/0 cables. The skin effects on transmission is a result of the alternator running at 600 Hz, if it was 50/60 Hz it could be #8 cables.


Now I did have to learn something about the skin-effect for the cable issues. But the skin-effect for both the Alternator, and the Buck Torrid's belonged to the manufacture to design around.

Now, I'm trained monkey, not an EE. So I depend on the manufactures for the heavy lifting of design. I did speak with Victron and their universal voltage inverters will work with my system to convert it to a Inv/generator.

But that's never been my goal, at least so far. This design came about as a result of need, for an efficient high amp charging of large battery banks, located a longer distance from the gen/charger that I am comfortable with. More then half of the boats that I have done design/build on require upto 50 feet.

One boat in particular has 3 12v banks 1400 amp hr, 1200 amp hr, and a 800 amp hr. They each have their own inverter charger running. He has two AC prime gens both Northernlights 16kw and a 8 kw. He can run his gens 24/7 and has to just to keep up on the bats. The boat is 90 feet, and the generators can't run at night. So the bats and inverters do the job. The boat leaves Seattle in April for Alaska every year, and almost never touches a dockside shore power, until she lands back in Seattle in October.

This year the bats are 3 years old and are sulfated so bad that they will have to be replaced. That's getting ready to happen, along with the removal of the 8 Kw, and replace with the DC CCG.

Lloyd

If you like rectifiers http://www.powersystemsdesign.com/po...er-?a=1&c=1195
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Old 12-05-2012, 23:28   #35
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Re: Charge Cycle Generator

well, i thought i would post an up date.

So this week after nine years I had to replace my 6 Trojan T-125's, with the same. I kind of kicked the old ladies when they were down 2 winters ago, my old Trace MS2512(it's older then the bats.) is temp compensated in a way. That is as long as the operator remembers to change the settings for winter and summer.

I always say KARMA is real...so the week I ordered the the new bats, I stop by the boat to do some prep work. I open the door...and the first thing I smell is magic smoke. My sniffer leads me to the inverter cabinet, after a quick check of the bat monitor.

Yep...as my noses gets closer to the inverter, the stronger the pungent smell of magic smoke. After I pop the top on the inverter I find a smoked resistor, and capacitor, along with a couple of diodes, the trace on the fet board looks ok...but it's likely the end of life for this inverter. I found another fet board used...but at 12 years old this inverter isn't fit for sea duty anymore. I think I"ll replace the fet board and make it my bench top charger for bat maintenance.

So now I have to do a final bone up on a new inverter for my own use. I installed about 10 inverters last year, of just about every brand except Magnum. As it turns out Magnum is a company which includes a number of EE's from Heart, and Trace. I like Outback, have had good experience with them, I won't even consider a Xantrex, and I have installed a number of Victron Products so far so good...the one thing I don't like about Victron is all of their equipment is built to only a 20 degree temp rise.

So I started doing some research on the Magnum. Turns out they are built like a tank much like the old Hearts, and the early Trace's. The magnum was almost a direct bolt in with no modification needed to the inverter cabinet, both the Outback, and the Victron would have required a major job removing and rebuilding the inverter cabinet. I was willing to do it for the Outback but not the Victron, in the end I couldn't make the Outback fit.

So I ended up with the Magnum MS2812 Pure Sine, for 2 reasons. (1.) it fit no mods, and (2.) it's built to a 60 degree temp rise. So with that I needed to bone up on the Magnum associate parts, which included a networked version bat monitor, Inverter Remote Control, and Auto Gen Start. I decided that I didn't need the BatMon. as I already have what I think is the best in the industry My "perky\cat/volvo" DC bat charger. But I did do the networked auto gen start, and the Remote Inverter Control Panel.

The Magnum like the Victron has a shore power boost capability, and with the triggers from the BatMon. and Auto Start, the little DC charger can operate as a hybrid. (1.) as a dc bat charger/cogen, (2.) as an inverter gen, that backs up shore power in boost mode....and the Icing on the Cake is the ability to auto increase/decrease gen speed based on load demand. That final key was from Precision Governors PG Engineered Control Solutions > Products > SV Linear Actuators for Caterpillar C (3000) and Perkins 400 Series Engines

So now she starts up from manual or auto, goes through warm up, then into bulk charge at 2450 rpm, and as soon as the amperage drops from high to low the gen slows 1600 rpm to match the output, then a simple load call speeds her back up until the demand drops again, or she auto shuts down. I can set the quiet time so the auto start is in hibernation, and wakes up during programmed hours of OK to run gen time.

Wee we're having fun


I completed the 2nd commission cycle on the new bat bank, which consisted of drawing 325 AmpHrs from the bank at about a 20 to 25 amp draw, over the course of about 24 hours. Then I switched back on the new magnum inverter to charge mode. It put a steady 125 amps into the bank for almost 3 hours before the absorption stage was reached and started folding back the current.

A couple of features on the Magnum I really like, the remote gives you the temp of the bats; never exceeded 68 F, and it also gives you the temp of the transformer which was at 120 -130 F during the bulk charge cycle, as well as the temp of the fet's, which were stable at about 115 F. After 3 more hrs the bats reach 100% and the Magnum kicked into float charge. Now one thing that I really like is this unit is it's PF corrected, which is why it was able to put out it's rated 125 amps for the 3 hours. My dock power is a little wanky, and the the old Trace that was not PF corrected could only muster about 80 amps out of it's 120 amp rating.

Now that the bats were in float I proceeded with my next round of testing. I started up the perky/cat with the Balmar 614 controller, let the engine come up to temp. Then I turned on a 750 watt load, for 10 mins. then added another 2k watts for a total of 2750 watts running off the inverter, then I added 20 amps of DC loads to the bats....Now the the Perky/Cat is producing a stabilized amp output of right at 250 amps. A check of the BatMon. shows plus 5 amps which at 14/7 V which is what the absorption voltage/amperes were when it switched to float. Now for the real test the freezer and the frige 2 separate units start cycling on and off(these are inverter loads). I run this load for 1 hour straight. Now that's an inverter/generator.

I am really impressed with the Balmar 614 controller, each time the refer or the frig cycled on I watched the BatMon, and the no loads coming from the bats, the Balmar was able to ramp up and down to maintain each cycle which was on average about 10 minutes each, sometimes together, sometimes 1, then both.

After the 1 hr run the temps were as follows Bats 58F, fet's 112 F, transformer 132 F, the bridge rectifier on the Leese Neville 82 C, and the Perky temp is stable at 190 F.

Now that boys is an inverter generator operating at peek efficiency across the board. I am so pleased that my plan came together.

Next test up are the shore side boost, and the gen auto start.

wooohhhhooooo


Lloyd
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