DC generator vs DC Converter

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Solar Flare wrote:

...This is like charging and discharging your bank 120 times per second. Much wear and tear on the battery bank.

How much is too much?
Nick

"danny burstein" wrote in message

In "RoughRider" Reply@ThisNewsGroup.com> writes:
The hybrid car (and even hybrid railway switch yard locomotives) are great for stop and go applications where large amounts of power are required to get moving, then power requirements taper off. Hybrid cars are excellent for city, but limited by the engine horsepower at highway speeds.
Those of us driving the hybrids (such as the Honda Insight) have no trouble whatsoever keeping up with highway traffic speeds.

In your rush to defend hybrids at all costs, (even though he never said that hybrids can't maintain highway speeds) you seem to have missed RF Dude's main point. It is a shame because it was a good one.
Vaughn

In "RoughRider" writes:

The hybrid car (and even hybrid railway switch yard locomotives) are great for stop and go applications where large amounts of power are required to get moving, then power requirements taper off. Hybrid cars are excellent for city, but limited by the engine horsepower at highway speeds.

Those of us driving the hybrids (such as the Honda Insight) have no trouble whatsoever keeping up with highway traffic speeds.
(can't speak for all the different models out there, of course).

-- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded]

"Plan B" wrote in message

I think efficiency could be improved with a "hybrid" system that uses an engine and a battery, similar to the systems used in cars like the Toyota Prius or Honda Insight.
The design idea I was thinking of was to use a generator together with an interactive type UPS (Uninterruptible Power Supply)http://en.wikipedia.org/wiki/Uninterruptible_power_supply. Suppose you selected a generator that was slightly small for the application, such that the peak power output could not supply enough power to drive a peak load directly. Then during a time of peak loading, the generator output voltage would sag. In this case, the UPS would draw supplemental power from the batteries to meet the peak load.
This is plug-and-play with the Xantrex SW+ series of inverters.

In "Vaughn" writes:

get moving, then power requirements taper off. Hybrid cars are excellent for city, but limited by the engine horsepower at highway speeds.
Those of us driving the hybrids (such as the Honda Insight) have no trouble whatsoever keeping up with highway traffic speeds.
In your rush to defend hybrids at all costs, (even though he never said that hybrids can't maintain highway speeds) you seem to have missed RF Dude's main point. It is a shame because it was a good one.

Looks like I missed it. I can tell you flat out that Insight (and most others.. can't swear to all) hybrid cars are _not_ "limited by the engine horsepower at highway speeds" - at least any more than any other car is similarly limited.
Can I do 150 mph? No. But very few other cars can either.
Can I maintain standard (not necessarily speed limit...) speeds and even pass as necessary? Absolutely.
The deal with hybrids (oversimplified a bit here...) is that "regular" cars have engines that are way, way, larger than needed for cruising highway use. This gives you plenty of extra horsepower when pulling onto the highway, but otherwise wastes plenty of fuel.
The hybrids have engines that are more than adequate for highway cruising (that is, smaller than regular cars but still quite good) and get extra acceleration horspower (for that "on ramp") courtesy of the battery pack and integrated electri motor assist.
Presumably if you're on a long mountain upgrade where that extra 25 horsepower might be needed for a half hour... you'll have some issues with the smaller hybrid gasoline engine, but that's a pretty rare situation.
-- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded]

"Solar Flare" wrote in message

Engine driven automobile alternators are usually 3 or more phases and the ripple from fullwave rectified 3 phase is next to nothing.
I have a NATO 2KW 28VDC field generator. The rating is 5% ripple.

wrote in message

Solar Flare wrote:
...This is like charging and discharging your bank 120 times per second. Much wear and tear on the battery bank.
How much is too much?
Nick
The battery manufacturers want perfect DC, like that provided by a regulated

power supply. As Solar Flare remarks, they want it that way with the battery disconnected. The battery will level it, but at the cost of constant erosion of the plates.

Robert Morein wrote:

I have a NATO 2KW 28VDC field generator. The rating is 5% ripple.

Is that too much?
Nick

Robert Morein wrote:

How much is too much?
The battery manufacturers want perfect DC...

Ah. So 1 microvolt is too much.
Nick

"George Ghio" wrote in message

JoeSixPack wrote: nicksanspam@ece.villanova.edu> wrote in message
Robert Morein wrote:
Ripple current will kill a battery.
Because of the heating effect?
An engine driven alternator has too much ripple to float a battery...
How much is too much?
Nick

That's a bit confusing, because it's my understanding that a storage battery does a fine job of leveling off the peaks and troughs in any circuit connected to it.

The danger here is just too much bad advice. Now from your post:
"None of those concerns are mine for this application. My intention is to supplement the charging of the photovoltaics when they can't keep up."
You can do this. You will need a regulator to control the charge.
You have three choices:
1) The reg built into the alt. Only if you are desperate.
2) A purpose built reg. Better control, better charging.
3) The reg you have between your ears. Works well, runs on full logic but requires you to stay awake.
I believe you said 4 225Ah batteries. If that is in fact 500Ah all up (4 T105s series/parallel) then a 30 amp alt will be fine, 60A would be pushing the friendship a bit. C10 would be 50A. But you want to bring your batteries up faster than ten hours.This means you need a charging regime to suit your needs.
My charger:
5hp motor, 35A Bosch alt(external reg type, reg not used) Rheostat for field control. This is the famous 150A rated ceramic Rheostat scrounged from a spot welder.

When using the rheostat what exactly is happening? Are you able to control both the voltage and current or just the current and shutting down when the voltage reaches it's peak?

Take the state of charge in your batteries. Yes it is important that you not let them remain at a low state of charge for long periods, on the other hand they do not need to reach 100% charge every single day either. I will run the little generator to charge my batteries if they drop to 12 Volts (but like the fine print says �Conditions Apply�)

This is a very good point concerning effeciency--the batteries do not necessarily have to reach a 100% charge every day. I do not know how to tell the difference between, say, a 90% and 100% charge. My hydrometer will read "full charge" but my Vector charger may still be charging at 5 amps or so. I would go so far as to say that the hydrometer's reading is probably a good enough indicator and if it says full then the batteries are adequately charged. About every few days, however, I do let my Vector run until it shuts down and says "full."

Condition: Batteries read 12 volts at four o�clock in the afternoon
Condition: I know the sun won�t be out tomorrow.
Condition: I need to use the computer for several hours that night. (This condition has been negated due to better computer.)
Condition: There will be three hours of Red Dwarf on TV that night.
It takes at least two of these conditions to warrant the running of the generator. It may be that your "required" conditions will be different.
And when it comes to charging the batteries I am not trying to bring them up to 100%. I am doing what I call �Maintenance Charging� which is to say that I only require that they be in the top twenty per cent of their capacity. The sun usually does the rest.
When required I run the gen for less three hours. This is for a battery set of 840Ah. During winter this may be as much as 3 hours a week or as little as 1-2 hours/month.
Will this harm your batteries, only if you're stupid and don't pay attention to what you are doing.
Oh, I also run a logger on my system so I know what is going on, at all times.
George

Yet another is emissions. Mostlikely making it illegal to sell it. Also indicating, generally, lower overall efficiency than for stoves mfg after '90.
Anyhow, BTU ratings for woodstoves are often totally bs, primarily because it's possible with most to get short-term output that can't be sustained. As important as any fictitious #s: how much wood can be loaded into it for a clean, slow burn, and how long can that be.
Stay warm, J

In article , hchickpeaREMOVEME@hotmail.com (Harry Chickpea) wrote:

snipped for brevity

Where I'm going is the idea of a system where an engine/alternator operates for the peak 2 to 4 hours per day, also supplying hot water and heat as co-gen, but then the battery/inverter system coasts the lighting and less energy intensive appliances through the rest of the day - but (and this is the big but) the system can operate in this mode indefinitely.
Is something like this feasible?

This is basically how I use my system. I have twin 20Kw Gensets that I run for a totall of 10 hours a day. (7Am to noon, and 5Pm to 10Pm) That takes care of the main High Power Loadings of Breakfast and Dinner and the charging of all the battery banks for the twin inverter systems connected. It also keeps the four freezers at better than -10F on a 24/7 basis, and the telco equipment battery bank charged. I have had really good luck with both a 1200Amp/hour 24Vdc L16HD bank, as well as a 800Amp/hour 24Vdc Absolyte II AGM battery bank. These are on the inverter systems. L16 bank is over 4 years old, and replaced a 800Amp/hour bank that was 12 years old. The Absolyte II bank is 8 years old now and still has 95% of the new capacity.
Bruce in alaska -- add a <2> before @

On Mon, 17 Oct 2005 08:03:40 -0700, "Ulysses" wrote:

When using the rheostat what exactly is happening? Are you able to control both the voltage and current or just the current and shutting down when the voltage reaches it's peak?

The latter. But if you *know* how many Amp-hrs you want to replace and the charge rate of the generator, then a spring-wound timer can be used to somewhat automate the process. Ideally the timer would shut off the field current, and then shut down the engine after a short delay to allow some unloaded cool-down time. This outfit http://www.ifg.thomasregister.com/ supplies affordable timers with custom contact arrangements and delays.

Take the state of charge in your batteries. Yes it is important that you not let them remain at a low state of charge for long periods, on the other hand they do not need to reach 100% charge every single day either. I will run the little generator to charge my batteries if they drop to 12 Volts (but like the fine print says �Conditions Apply�)
This is a very good point concerning effeciency--the batteries do not necessarily have to reach a 100% charge every day. I do not know how to tell the difference between, say, a 90% and 100% charge. My hydrometer will read "full charge" but my Vector charger may still be charging at 5 amps or so. I would go so far as to say that the hydrometer's reading is probably a good enough indicator and if it says full then the batteries are adequately charged. About every few days, however, I do let my Vector run until it shuts down and says "full."

You might consider adding a Trimetric, Link 10, etc. It will keep track of Amps in and out, and automatically take Peukert's equation into account. Here's a link to the user manual for the Link 10, see page 40. http://www.xantrex.com/web/id/72/docserve.asp
Wayne

You missed this: "They depend on slowing down or idling to be able to charge the battery."
Especially the regenerative braking part. Kinda hard to get that from powering house.
Relax, J