what size generator?

BB.

Re: what size generator?

Good Find Jim and Niel!

From the Xantrex Products link by Niel:

• Auto-ranging universal input voltage (100-260 VAC, 47-63Hz) is also compatible with generator or other low quality power sources...
• Power Factor Corrected for efficient charging

The "Wide Range" or "Universal Input" AC input (not Auto-ranging as Xantrex sales states) of 100-260 volts with no "dead zone" (rated not to run between~140-180 VAC, or a spec that reads something like voltage range: 100-135, 187-264 VAC 50/60 Hz), is another indication of a power factor corrected supply.

"Auto Ranging" and power supplies with a 120/240 VAC switch are typically diode bridge front ends with a voltage doubler at 120 VAC, and non-voltage doubling at 240 VAC setting. Auto Ranging just makes the voltage switch detection automatic (switching between voltage doubler or non-doubler).

Also statements like these (again from the product specs pages):

• In addition to meeting global safety and emission standards...
• CE marked, meeting LVD and EMC directives

Also are indication that the unit in question may have power factor correction.

Kevin, that was a great question you originally asked. It had been so many years since I had to worry about PFC, that I had forgotten to even look for it in battery chargers--I just assumed that all presently shipping product would have this feature--except for the very cheap stuff (i.e., the $29.95 special auto battery charger).

Obviously, there is still a lot of this non-PFC product out there... The PFC requirement was first a European requirement for larger devices (more than a few 10's of or hundred watts). Actually, I don't remember at this point if the US/NRTL's made PFC a US requirement or not (been years since I did regulator work)...

And yes, having a PF corrected battery charger is a very worthwhile investment--especially if you are running off of a generator or using larger battery chargers.

You can have a 120 VAC only rated PFC power supply--but it is usually a 100-264 VAC 50/60 Hz rated power supply because it was originally a European requirement and the universal input was one of the basic requirements that allowed you to pretty much ship anywhere in the world with one product.

-Bill

System2

Re: what size generator?

Hi Bill,
I've been told that my generator does not even have a voltage regulator?
So how does that effect my choice of battery charger (power rectified or not?)
Also someone was stunned at my decision to operate a 2.5KW inverter from 12volts. They say 2.5KW load at 12Volts may warp the battery plates.?
Can you help me?
I have a Xantrex Prosine2000 in mind or a Xantrex Freedom 428 Combi 2.5KW unit but they are both 12V units. Prosine 2000 is powerfactored.
My only loads are a 1HP table saw and/or a circular saw whilst I am running the charger at the same time. (daytime)
Lights and stereo from the batts in the evening!
12V system adequate?
Kevin

BB.

Re: what size generator?

Kevin,

Your generator may or may not have what you would recognize as a voltage regulator... It is possible to wind generators and/or add a few passive components to create a reasonably accurate output voltages and not have a "regulator box"...

The problem is that a "old style" battery charger (or even computer power supply) draws very short, high current spikes--and any limited sized power source (generator or inverter) has problems supplying the spikes--and instead will typically chop off the voltage crest of the sine wave.

If you want to use more than 25%-50% of your generator's capacity to charge the batteries, then you would want to get the power factor corrected charger (or inverter/charger).

I don't have a battery/generator system--so I cannot give you the exact numbers--perhaps somebody else can give you more exact recommendations for charging capacity vs generator capacity...

Regarding 12 volts for a 2.5kW inverter... Current wise, you will need to account for peak amps of:

2,500 watts / (0.8 eff * 10.5 VDCmin) = 298 amps at "12 volts"...

Problem is to supply that load you will need large diameter copper cables from the inverter to the bus bar/central distribution area..

Connection your batteries in series/parallel, that would, ideally divide the load by 1/10 or about 30 amps per battery pair.

I don't remember the ratings of your batteries--but that is a pretty hefty load. Hopefully, the saw will only draw a 1,000 watts or so under load, so that will cut the continuous current 1/2 (or a bit more).

A higher voltage inverter will cut the current in your wiring (24 VDC cuts it in half, 48 VDC cuts it by 1/4--vs a 12 VDC inverter)... Wiring up a multiple hundred amp circuit is not something that people would like to do--if it can be avoided.

But, if you are going to be doing a lot of cutting at one time--it is probably worth firing up your generator to power the saw--more efficient and friendlier for your batteries.

-Bill

System2

Re: what size generator?

Hi Bill,
Thanks for indulging me with this discussion.
Yep, you are right the generator operates the table saw.
.....and the batt charger at the same time!!.

These batts are only 'on site' because they were given to me.
The batts are 10 years old and were originally connected to the grid and installed in a 120Vdc array and were used to operate and run 120vdc equipment.

So the bus bars and 00 welding cables are all supplied for a 120Vdc@ 160a/h array (there is no 120Vdc charger however).

I have been told 120Vdc is nasty......is it?
and a 12Vdc system a little too small.?
Do you agree? Where is 206amp load? for how long?

What is your system? experience?

kevin

BB.

Re: what size generator?

Kevin,

My system is a 3kW Xantrex 3.0 Grid Tied inverter a little over two years old.

My other experiences are as a design engineer that included one project designing a large voice mail system to run off of 48-60 VDC battery banks at the phone company...

The problem I have with predicting your system performance is that we don't have the average power required by the saw or know the details about the batteries.

In theory, you should find a chart from your batteries that show Amp*Hour rating vs load curves...

A load on a lead acid storage battery that is 1/10 or 1/20 of capacity is pretty normal and that is why you see 20 hour ratings (1/20 * C). If you batteries are around 100 AH, and run them at 30 amps, you are around a 1/3 rating--For the typical Lead Acid storage battery, that is quite a load--it will tend to heat them up and also have issues with the rate at which the chemical transformation can occur--all leading to an apparent loss in battery capacity.

In theory, you could run your saw about 2-3 hours to 100% dead battery--but you don't want that, so--just as a guess if all was running well, you could run it for about 1 hour of heavy use.

Of course, if you know you are going to run your saw for an hour straight--you should probably using your generator at this point--both for fuel economy and avoiding strain on your batteries.

But, if you are typically using your saw for a 1/2 minute at a time every 5-10 minutes like most people just working around the site--I am sure that you could probably go all day without needing to recharge--the blessings of a battery backed hybrid generating system...

However, if you end up running the generator for 5-10 hours to recharge the bank (0.1C charging a 50% discharged battery string)--you might as well as just run the generator for your work loads anyway.

Once you have solar (probably a couple kW array--depending on your loads), that will allow you to cut way back on your generator/noise machine usage.

The 200 amp load is from the input of your inverter to the battery bus/combiner bar/connection... If the battery wiring and batteries are all balanced that each battery will supply 1/n portion of the parallel load (10 parallel connections then 200/10=20 amps). The problem is that it is difficult to achieve good balanced current flow in multiple parallel connections and there will be some batteries supplying more current and some less.

Some final thoughts... You should look up the model number for your batteries on the web. If these were for battery back systems--may are specialized storage batteries that were for emergency use and not designed for daily deep cycle usage. Some only achieved long life by limiting discharge to only 20% or so--not the 50%-80% normally spec'ed for a solar deep cycle battery.

And yes, 120 VDC from a storage battery can provide "more excitement" in terms of arcs, short circuit current, and melting of wires vs a typical home wiring circuit. Batteries supply huge amounts of surge current vs the pole transformer and DC sustains Arcs much better than AC. However, DC is slightly safer than AC in terms of electrocution (AC causes your muscles to contract and you can't let go of an electrified wire).

I am sorry that I am more or less dancing around your questions...

-Bill

PS: I should also add that storage battery systems actually have quite a wide range of operational voltages... For your "120 VDC" system this would range from ~105 to ~155 volts DC (dead to equalization voltages). Most 120 VAC items would start to have "issues" with voltages over about 132 Volts. Trying to run your tools and such from a DC battery bank would probably require you to carefully monitor/control your charging voltage while using your 120 VDC...

System2

Re: what size generator?

Hi Bill,

Exide storage batteries info.

Exide CA-9's 6V@160 a/h each.

Discharge rating. TO (reach) 1.75VPC is:
8hr @ 25.0 amps, 5hr @ 35.2 amps, 4hr @ 41.4 amps.

The table saw is not an issue because I just won't run it or other large loads from batts. I will run generator.

My hand tools ie; typical circular saws is 120V@12amps and some LED's or flourescent lights and stereo at night time.

These batts are deep and weigh 150lbs each.

Bill, there is a prosine 2000 on Ebay right now and I am quite interested because I believe it might actually solve my charging needs at least - and operate some cabin needs. I believe it will plug into my 5.0KW generator which is fine with me!

Any comments? anyone?