Power inverter question for the EE's here.

beeman458 · April 24, 2004

I've ordered or have on order a couple of modified square wave power

inverters and several deep cycle batteries.

My simple question; Will the efficiency of a power inverter, stand

alone battery power supply combination be enhanced by the addition of

a high volume capacitor?

The reason for the question has to do with the initial draw on the

battery after a flash head is triggered. This draw can last for up

to three seconds and then straight line down (according to Speedotron

engineer) until the power pack capacitor is fully charged and ready

for the next triggering event.

Power inverter and battery choice;

<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?

ViewItem&category=32814&item=3093066635&rd=1">Cobra 2500w/5000w,

modified sine wave power inverter</a>

<a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?

ViewItem&item=2475544238&category=31284">Deep cycle marine gel cell

battery</a>

The above combination has enough umph, 80 amp hours, to drive two

Speedotron Brown Line, D1204 power packs, with a 10 amp demand each,

with 150w modeling lights (M11's) with power to spare for over two

hours of constant on usage before it's necessary to swap the battery

out for the spare back up battery.

My thinking is that by putting a 3 farad capacitor in-between the

battery and a 2500w/5000w power inverter, it will make the inverter

more efficient as it won't have to work so hard (resistance) to suck

the power out of the battery as the energy will be stored and at the

ready in the additional capacitor for use after each triggering

event.

I'm further thinking that the less strain (demand) that's put on the

battery, the more juice one will be able to be suck out of the

battery; One hour draw, 50% of capacity as opposed to twenty hour

draw, 100% capacity. This based upon battery demand efficiency

charts. In layman's terms, the harder you beat on a battery, the

less you'll get out of it:)

<a

href="http://www.majorpower.com/inverters/battery_sizing_faq.pdf">Batt

ery sizing chart</a>

Capacitors being considered;

<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?

ViewItem&item=3093256476">Capacitor 1, example</a>

<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?

ViewItem&item=3092866977&ssPageName=MERC_VI">Capacitor 2,

example</a>

Not being an electrical engineer, I'm prevailing upon those here that

are to help me with my ignorance about the benefits of adding and

additional capacitor such as those listed above.

Details:

The pair of deep cycle batteries, cases and individual chargers have

been received and the linked power inverter has been ordered. The

battery, capacitor and power inverter will be wired together with

4AWG multistrand battery/welding cable such as one might find at a

auto sound supply outlet. All cables will be as short as reasonably

possible and the capacitor will expectedly be wired to the power

inverter with the shortest wires possible.

Thanks in advance for your valuable input.

bruce_rubenstein___nyc · April 24, 2004

I don't see any benefit to using a large capacitor in this application. In an automotive sound system the battery is located some distance from the amp (which uses DC power directly). There is resistance in the wires running from the battery to the amp, and this limits the peak current flow. By placing a large capacitor close to the amp, and using large gauge, low resistance wire to connect them, high, short duration current peaks can be delivered to the amp. In your application, there is very little wiring resistance on the DC side, and the current draw is: 1) for a much longer duration and 2) the current draw is probably limited by the input impedance of the converter and not the internal resistance of the battery/DC power source.

stephen_ratzlaff · April 24, 2004

Make very sure, because most strobe gear requires pure sine wave.

I know that's what I'm looking to build.

In fact, I asked questions regarding building a battery system for my Acute2 gear at the Profoto USA forum and my post disappeared after a couple of days. I guess they don't want to answer those types of questions.

Anyhow, the inverter's I'm looking at are the Xantrex Prosine 2.0 2000w pure sine wave inverter/charger. The AIMS branded inverter at 1500w and the Samlex inverters (Cotek 1500w). I think the Cotek 1500w is made by Rich Electric ( www.rich-electric.com ). They also have 2500w and 3000w pure sine wave inverters but they are quite heavy.

The Prosine 2.0 with built-in charger isn't cheap, but does weigh 24lbs, and this includes a built-in charger so the only other weight would be the battery. I too am looking at the Optima blue-top or yellow-top 34M batteries since they are sealed.

beeman458 · April 24, 2004

Bruce wrote

2) the current draw is probably limited by the input impedance of the converter and not the internal resistance of the battery/DC power source.

Bummer! I'm so looking forward to attaching one of those fancy pants capacitors to the battery case:)

The benefit that I'm looking forward to is a less aggressive attack on the energy draw that's stored up in the battery. The harder one attacks or draws on the energy stored up in a battery, the less it's willing to give back out. Sort of like a teenager's attituded:)

I agree with your comment about the benefit of a capacitor being at the end of a long run. Utility companies gain efficiency from a system where a capacitor is placed at the end of a T&D (Transmission & Distribution) run.

Thanks for your insightful comments.

Now the question, to add or not to add? To make the system look cool or make it look utilitarian? :)

beeman458 · April 24, 2004

Stephen wrote

Make very sure, because most strobe gear requires pure sine wave.

I lucked out as the Speedotron Brown Line power packs can use a modified square wave A/C signal.

In fact, I asked questions regarding building a battery system for my Acute2 gear at the Profoto USA forum and my post disappeared after a couple of days. I guess they don't want to answer those types of questions.

I'd have ta agree with you on that one sport. A deep cycle battery with case and charger is two hundred bucks (US) and an AIMS 1500w pure sine wave power inverter can be had on e-Bay for about $450.00 (US). You'd get about four times as much for about one third the price. I can see why Profoto would want to shut a simple question like that down. :)

<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=41980&item=3189873794&rd=1">Pure sine wave power inverter @ e-Bay auction</a>

Anyhow, the inverter's I'm looking at are the Xantrex Prosine 2.0 2000w pure sine wave inverter/charger. The AIMS branded inverter at 1500w and the Samlex inverters (Cotek 1500w). I think the Cotek 1500w is made by Rich Electric ( www.rich-electric.com ). They also have 2500w and 3000w pure sine wave inverters but they are quite heavy.

The Xantrex prosine units are just way too pricey for my hobbyist budget. If the green were there, I'd pick the Prosine 2.5 up in a heart beat. Since I can get by with a modified square wave, I'm good with what I listed. If I wasn't, I'd probably pick up a pair of the AIMS 1500w pure sine wave power inverters. Why? By splitting the system over two inverters and batteries, one is able to get more energy out of the batteries.

The Prosine 2.0 with built-in charger isn't cheap, but does weigh 24lbs, and this includes a built-in charger so the only other weight would be the battery. I too am looking at the Optima blue-top or yellow-top 34M batteries since they are sealed.

As I posted, I've picked up a pair of the Optima blue-top batteries. They are rated at 80 amp hours. I have a yellow top 34M on order and should have it in the next week or so.

I'm down to the capacitor question. Once that question is settled in my mind, I'll be able to wire the battery and inverters together and run some tests but I'm still a couple two or three weeks off from being about to run any usage tests. Darn! :)

Thanks for the questions. They're very helpful and keep me on my toes:) This is a good thing.

phi_pham · April 25, 2004

you may also consider putting a welding arc stabilizer in series between the battery and the capacitor. its basically a really big choke(inductor). this will isolate the battery from the current spikes and allow the inverter to draw from the capacitor.

beeman458 · April 25, 2004

Thanks Phi!

I'll do some research and see if this will help stabilize the power supply that's being cobbled together:)

I did a quick web search but all I could come up with was some arc starters, as the choke you decribed, helps one start a welding arc without need of striking the rod. Not going to be doing any welding although the amount of energy I'll have at my disposal would allow me to weld some mighty thick plate:) I'll look further into your suggestion and see what I come up with.

I'm going to give the manufacture of the power inverter, Cobra, a call in the morning and see if I can get some insightful information from their tech support people in regard to the question I posted.

The answers I've received so far from others has left me with no real answer other then a resounding "Maybe!" Being pretty much clueless, I need an answer from an experienced person to give me some guidence on the subject matter/question.

stephen_ratzlaff · April 27, 2004

Kinda figured that anyhow, so no surprise. The contact said I'd be fine with a 2000-3000w pure sine wave inverter. The Acute2 packs require 10 amps at 120v on slow charge. I probably won't be able to power two packs on slow charge of the Xantrex Prosine 2.0 though. Drats!

Keep me posted on how your battery solution works, I'll keep you posted on mine.

BR

SR

beeman458 · April 27, 2004

Stephen wrote

Keep me posted on how your battery solution works, I'll keep you posted on mine.

I have about another week or two ta go before I can give preliminary test results. I have the 80 amp hour batteries with chargers. I'm just waiting for the power inverter to arrive so I can get some 4AWG cable to hook the two items together.

Sorry to read that you're stuck with a pure sine wave situation as pure sine wave inverters are a bunch more pricey:(

Does anybody know of a converter that will convert a modified sine wave signal into a pure sine wave signal. I'd bet there's something out there at Radio Shack that costs only fifty bucks. :)

I'll post a new thread when I have some data to post.

stephen_ratzlaff · April 30, 2004

Will receive the Prosine 2.0 next week and will try it out.

Hoping to be able to use modeling lights and strobe for at least 3/4 of an hour to 1 hour with this setup. If not, will add another D31M in parallel to add a few more Ah to the mix.

Without modeling lights hope to get at least 300-400 pops at full power 2400ws off of one pack. We'll see.

BR

beeman458 · April 30, 2004

Stephen wrote

Will receive the Prosine 2.0 next week and will try it out.

Hoping to be able to use modeling lights and strobe for at least 3/4 of an hour to 1 hour with this setup. If not, will add another D31M in parallel to add a few more Ah to the mix.

Without modeling lights hope to get at least 300-400 pops at full power 2400ws off of one pack. We'll see.

Oh my! A prosine 2.0. Aren't we the spoiled one:)

One thought about running a pair of D31M's in parallel..... a hundred and twenty plus pounds! :)

The power inverter is ordered, I'm still waiting for it to come in.

I have a pair of those puppies with a D34/78 for a spare (Yellow Top with a 55 amp hour reserve). I think it would be easier just to switch over to the next battery as opposed to trying to haul in a second battery and then marrying the two together in parallel.

How many pops do you expect to do in one session? Oh! And what's the amp draw of the 2400ws power pack that you're gonna plug into your fancy pants, "pure sine wave", Prosine 2.0 power inverter? :)

stephen_ratzlaff · May 1, 2004

Gonna get one of those carts (kind of a dolly) where the big wheels turn sideways to allow for packing up into real small footprint. Walmart has one for $39+.

Then gonna get a largish rubber/plastic type tool box and mount the battery(ies) in the bottom of the toolbox with the inverter/charger mounted above the batteries. Probably put some plywood in the bottom of the toolbox and mount this semi-permanently to the cart. I want the inverter and battery(ies) separated by plastic so no shorts. Want the whole thing to be fairly weather proof also.

Gotta find a way to make a door in the bottom toolbox where I can access and remove the battery(ies) pretty easy. Time for the Dremel tool and some cutoff disks, I suppose. Trying to figure a way to make the battery(ies) slide out on a shelf or something which locks when I close the door. Want the battery(ies) help pretty tight while in the unit, but also want plenty of room for air to circulate.

Main thing is I want to be able to remove the battery(ies) easily when loading into a vehicle, then once on site put the battery(ies) into the toolbox/cart and wheel it wherever I want. Then the 150+ lbs arrangement won't be so bad to handle. Can't wait till fuel-cells are widely available at cheap prices. The the only weight to consider will be water.

beeman458 · May 1, 2004

Stephen wrote

Can't wait till fuel-cells are widely available at cheap prices.

Couple of short comings with fuel cell technology besides how to get rid of the water. Aquiring the H2 and then recharging the H2 bottle once you've depleated your bottle as opposed to plugging into the wall and recharging your batteries.

Your setup, when completed, may be a monster weight wise, but it's probably the most efficent and convenient method for portable, non-generator created power you'll be able to put together over the next twenty or thirty years. I truly don't see technology, in the portable power supply department, advancing any over the next few decades. We may both be surprised with fuel cell technology but I just don't see it in the near future. I'd be happy to find out I'm wrong.

As to your power consumption, I think you're gonna be pleasantly surprised. The fifteen amp draw is only momentary during the time the power packs capacitors are being charged. Then the power demand of the power pack will drop down to an idle draw of forty watts or so. Your biggest draw is going to be your modeling lamps.

With two batteries, in parallel, of the type you have, you should be able to easily get an hour of constant usage of modeling lights and pops out of the combination. Your limiting factor will be how hard you draw on the battery. The harder or faster you draw on the battery reserve, the less stored energy you'll get out the little sucker; one hour draw Vs twenty hour draw.

Good luck with your cart construction as the WalMart cart idea is an excellent idea. Hadn't given portability much thought other then lugging it about:) Looking forward to posted images of your completed setup. One of those small Rubber Maid, gardening carts may be the ticket for a one battery system. Battery inside, wire access holes drilled into the side, with room inside for electric drop cords and the charger with the inverter mounted on the top lid.

watchin · May 1, 2004

I've considered this a couple of times but the budget was just too tight. Well, the budget hasn't gotten any better but I'm considering again. The references mentioned above will help if I decide to do it

myself.

Please let us know how it all works out !

A couple of additional questions:

1) Can someone give me an estimate on the total cost for a project like this?

2) Am I better off buying a completed system? I'm competent with DIY component assembly, soldering, cabling, packaging, and such.

3) I've got Alien Bee lights which have thier own battery system (a full sine wave system I believe). Would the less expensive suggestions above be compatible?

beeman458 · May 1, 2004

Total cost for a system, pure sine wave, will be about $800.00 (US)

<a href="http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=41980&item=3189873794&rd=1">Pure sine wave power inverter</a>

A decent, Optima battery, shipped, runs in the $150.00 to $200.00 (US) range, depending on what amp hour you choose to go with. It's advised to go with the marine, blue top, as this is the best constructed and has the 5/16ths inch threaded lugs.

<a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2476688702&category=31284&sspagename=WDVW">Optima D31M blue top battery</a>

I purchased my battery, case and charger (two ea) from these folks listed in the link above, shipped for about $210.00 per set. (US).

With a small amount of 4 AWG cabling and a plastic rubber maid case from WalMart, you'll be in gear.

If the budget is seriously constrained, by piece by piece as the budget/credit cards allow.

Hope this helps.

watchin · May 1, 2004

Thomas - thanks for the info.

Oh my - I was angsting about $500 White Lightning power pack...

This will give about 3 times the capacity though, WL is 15Ah this

is 53Ah (if I read it right). Another Big difference is 15 lbs versus 60 lbs..

Well I'll just have to see how it goes.

john_riedel · May 1, 2004

Somewhere in this post utility companies and capacitors were talked about.

From a an old EE that used to work for a power company...

The reason for the capacitor in AC utility power is different than using a capacitor in DC applications.

In the real AC world not all loads are purely resistive, in fact most like motors, balasts for lamps and such make the load on the system reactive, in this case mainly inductive. This results in a difference in KWatts, and KVoltAmps. KW, KVA, KVAR, and power factor (pf) are all related numbers. If you know any two you can compute the others. The goal is to get the power factor as close to 1.0, a pure resistive load has a pf of 1.0. The way to counter an inductive load is to balance it with either a capacitor bank, or by using more syncro AC motors in the system. A power company bills by one, but you get the use of the other, so the closer you can the pf of your equipment closer to 1.0, the lower your power bill. One the other hand, I've seen an over corrected system on a drilling rig in the Gulf of Mexico, the design pushed the load to be too capacitive when usage was low. They kept tripping generators by having the power factor too low. It's not a goog idea to leave 200 people in the dark 30 miles out at sea.

The other thing is that in AC power you can not longer think of a bunch of wires. The long lines become comparable to the wavelength of 60Hz, so now you have to also worry about the problems you have with RF and transmittion line effects.

Bottom line, just because the power company uses big capactior banks on transmition lines (AC), doesn't mean that in battery (DC) systems it's going to do the same thing.

beeman458 · May 1, 2004

G J Moody wrote

This will give about 3 times the capacity though, WL is 15Ah this is 53Ah (if I read it right). Another Big difference is 15 lbs versus 60 lbs..

I agree, for the big price, the capacity sure is small:)

Just for the record, the yellow top D34/78 battery has 55 amp hours of stored energy and the blue top D31M have 80 amp hours stamped on the pair that I just recently received.

As to the weight factor, rubber maid has some nice gardening carts that should fit the battery. Will be checking the measurments out the next time I stop in the local hardware shop.

stephen_ratzlaff · May 2, 2004

Inverter was $1472 and battery (D31M) was $208.

Cart and all the other stuff like cables and tool box, etc. will probably be another $100-125 or so depending on what I decide to use.

Anyhow, I look at it this way. The Profoto battery pack system is over $3000 and I could only use it for taking pictures.

The setup I'm building here, I can use for a variety of things. Computer backup (albeit quite expensive one) or as AC power source during electrical power outages, etc. for T.V or the refrigerator.

I've even thought that maybe I'll purchase another Prosince 2.0 inverter in the future sometime if this setup works out well and use them in series to run 240VAC appliances, if the need arises.

Anyhow, for about the same price as the Profoto 7B setup with a couple of heads I can have two complete 2000watt pure sine wave systems which can be used for a variety of things.

Also, I'm thinking my system will give more bang for the buck, so to speak, in that I should be able to get several hundred pops of the strobe at full power (2400ws) compared to the Profoto 7B.

BR

watchin · May 2, 2004

I thought you guys were looking at building a Hyundai on steroids.

Ya know - cheap with lots of power. Actually these are Hummers and

a Hummer with an M1 Abrams engine (and maybe the gun too)!

However when compaired to the high end battery systems(you did it, I'm now in research mode...;{)...

These have just about every aspect beat for half the price, except for

the size/weight. I can deal with the wieght issue though, that's why I have a pickup (right). I'm a little put off by the fact that I'll need a ramp to load the pickup now.....

Oh well, gonna do some more research.

Thanks guys! I'm learning...

beeman458 · May 2, 2004

Stephen wrote

The setup I'm building here, I can use for a variety of things. Computer backup (albeit quite expensive one) or as AC power source during electrical power outages, etc. for T.V or the refrigerator.

You forgot to list the most important usage for a setup like you're creating..... welding battleships. You never know when you'll need to do this sort of welding and it's important to always be prepared. Do you know where your battleship is? :)

stephen_ratzlaff · May 16, 2004

Now charging the battery for the first time with the Prosine 2.0.

Already went through the start-up procedures listed in the manual and everything checks out fine.

Have tested the inverter function with a lamp and works fine.

Will test the inverter with one of my PC systems tomorrow to see if the 16ms switch over time works fine and doesn't cause the PC to reboot.

The after a really good charge will torture test the inverter and battery by running T.V. and sound system to listen for bad harmonics or RFI/EMI (there shouldn't be any with pure sine wave), but want to be sure.

Next, will have to find an enclosure for everything; this is the last step and then I'll have portability.

Once I have the battery and unit safely mounted into its home on wheels, it'll be time for the strobe test, hehehe!

I'll keep you apprised.

BR

SR

beeman458 · May 16, 2004

Stephen

I've gotten a bit closer to the final testing of the cobbled together system on this end of the monitor.

I currently have chargers, cases, batteries and inverter in hand. Finally received the Cobra CPI 2500 on Thursday. On Saturday (yesterday) I started picking up 4awg cables to do a connect. Hopefully, today, I'll be able to hook the battery and inverter together to run a few low amp tests.

A problem I've noticed is, the charges are limited out at 12v. This is not good as it will limit the amount of juice one can pump back into a battery. A car alternator/voltage regulator combination puts out up to some 14.3 volts and I'd be happier to see the battery chargers limited out at 13.5v to 14.5v.

Any suggestions in regard to the 12v limitations placed on available battery chargers???

I won't be doing any fancy harmonic tests as I'm using a modified square wave RMS. Fortunately the Speedotron, Brown Line power packs are suppose to be quite happy with this due to Speedotron's choice of transformers that are used in the construction of the Brown Line power pack.

Currently, I'll be a bit amp limited as the auto supply house that I picked the cables up at had only a pair of 4awg cables of the type that I chose and the set up calls for a pair of 4awg cables running from the battery post to a pair of cable connects on the inverter. Why they couldn't have used a single 2awg connect is beyond my limited brand of EE thinking:)

I've been so busy, I forgot about picking up the Rubber Maid cart:) Cool, a new toy to go shopping for:)

beeman458 · May 16, 2004

Well. I hooked up the wires and it works like a champ:)

With the 150w modeling light on and a 400ws flash head, the inverter amp gauge comes on for about three, maybe four seconds and the fan comes on for all of one second, like it was cycling:) The battery, power inverter system rocks! Now I just need to pick up a cart w/wheels to drag it around in:)

Woo Hoo!

watchin · May 16, 2004

Saw a nice little cart today in a Staples Stationary store. (don't know if you have those where you are)

It's a milk crate on wheels with a retractable handle (kinda like a

carry-on airline bag) It's speced for 70 lbs carry weight and 1.7 cubic ft capacity...

bought one to haul around lighting gear in/on ... sale price $10 (well 9.94 + tax) .. Just found out you can order it on-line.

440122 Staples® Expanding Folding Crate on Wheels

at <form><input type="BUTTON" value="Staples Catalog Page" onclick=" href='http://www.staples.com/Catalog/Browse/Sku.asp?PageType=1&Sku=440122'">

</form>

Might want to look in the stationary stores near you.

Just a thought..

Glad to hear it's all coming together! Let us know what kind of

usage you are seeing when you get a chance to whack at it for a bit..

Best of luck, Greg<div></div>

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