PL6 - For highest output 20v w/ 40a or 30v with 25A ?

[phranticness]

Sorry if my question seems silly and long winded. I only know enough about electrical and electronics to get myself into trouble, so please bear with me. I'm also familiar with iCharger operation, FMA is new to me.

I have two HP 400w power supplies. They are adjustable and rated for 400w each. They have the capability of 0-25v and 0-25a, but for a max constant and stable wattage of 400w. They can be connected in Series or Parallel, which should offer a wattage of about 800w, I can push them a little harder, only a very little.

But - there is something I'm unclear on with PL6 operation. In the manual I read that at 12v, the PL6 is limited to something like 408w. I read that peak output needs a 30v input @ something like 40A. Is the peak output in between proportional to the input, meaning if my supplies are set at 20v with 40a available, can I expect the PL6 to charge at 600-700w? (considering some loss is to be expected) Or is output limited unless a specified voltage is supplied?

Another way to put this, should I setup my power supplies in parallel for 20v and 40a or should I set them up for 30v and 25a. (yes, those numbers are right, read above if you don't think so) Obviously it makes more sense to set up in parallel, unless a specified voltage must me reached to increase output.


Thank you, Steve J.

[Gregor99]

The input current limit is 40 amps. The output wattage is approximately 90% of the input wattage. For instance if you have a 12v, 50 amp supply, the maximum the charger could draw is 40 amps. 40x12 is 480. Take out the 10% losses and available at the pack is 432.

Also output wattage is relative to your pack's cell count. The higher the cell count the higher the wattage required to reach the charger's 40 amp maximum output. For instance, a 3s is 12.6v. 12.6x40 is 504 watts. A 6s is 25.2 or 1008 watts at 40 amps output.

Depending on your pack's cell count, the supplies you have may not be enough to power the charger. At 400 watts each, you could run them in parallel at 25v. That would give you about 16 amps per supply (32 total).

[phranticness]

Thanks Greg.

So I take it that input voltage does not matter, in that the charger will use the maximum wattage available to it, as long as it's below 40a, above 10 volts, and below 32 volts?

The most logical choice is to run the two power supplies in parallel since I'll get the biggest gains that way. ( in series I'd have to run the power supply voltage below the 50v max(31.9v), but in parallel I'll be able to run maximum available amperage (up to 40a)



Part of the reason I asked, when using just a single power supply in the same fashion I do with an Icharger, I was only able to charge at roughly 10A. The charger was only pulling 10a or so when set to 25v. That's only 250w. I wasn't sure if it was a voltage requirement to the charger, or the way I had the power supplies working. I'm going to set up the remote sensing function and wire them in parallel. They are pretty cool power supplies for other uses as well. (My buddy repairs them for a living - his work let me borrow them for as long as I need, I can't afford to buy them, they're like $2k each. )
Manual - http://cp.literature.agilent.com/lit.../5950-1765.pdf

[Gregor99]

So I take it that input voltage does not matter, in that the charger will use the maximum wattage available to it, as long as it's below 40a, above 10 volts, and below 32 volts?

Correct. The charger has DC-DC converter. It will take any voltage within the operational range and convert it up or down depending on voltage of the pack being charged and the requested charge current. As you can imagine, that limits the output on 12v, which is why 24v is more desirable. One other thing to note, if helpful if the input and output voltage are not close. For instance charging a 6s pack which is close to a 24v supply.


The most logical choice is to run the two power supplies in parallel since I'll get the biggest gains that way. ( in series I'd have to run the power supply voltage below the 50v max(31.9v), but in parallel I'll be able to run maximum available amperage (up to 40a)

Agreed.


Part of the reason I asked, when using just a single power supply in the same fashion I do with an Icharger, I was only able to charge at roughly 10A. The charger was only pulling 10a or so when set to 25v. That's only 250w.

You may have hit the wattage limit on the charger.

[phranticness]

Thanks again Greg.

I read up in the HP manual about connecting the two power supplies in parallel, and making one the slave and one the master. It only took a few minutes, made a couple jumper leads and now I have essentially one large power supply.

Since according to the HP manual, voltage at 20 or below is optimal (for the power supply) I set voltage to 20. I set the Amperage to max, the power suppy has over current protection and will shut itself off, plus the PL6 can be set to a max (I left a large margin for error. I set the PL6 to 20 amps for my 6s packs and wow, freaking AWESOME! A 4000mah pack is at 100% in under 10 minutes.


Now I just need to familiarize myself with the FMA software. Specifically the presets and library, I don't fully comprehend how they interact, but I'm sure the manual will help.,

[RedOctobyr]

These sound like pretty wild power supplies I wasn't aware of ones with such a large voltage range. You had me intrigued, until you got to the $2k part

What's the model number of them, for curiosity?

And I'm a bit confused. You said you connected them in series, for one big PS. But that you set the voltages to 20V, since that's the best voltage for the PS. But if those were series, that would be 40V, which would blow the PL8. Was that just a typo, and you meant you connected them in parallel?

And I'm sure you know this, but a 5C charge (20A on 4000mAh) is fairly aggressive. It'll be easier on the packs if you charge a few at once, in parallel. That same 20A spread across 3 packs is 1.7C, but you'd only have to manage a single charge (vs 3 in a row), and you'd be done in about the same total amount of time (maybe quicker, due to only 1 CV/balancing phase?) vs charging 3 packs at 5C one after the other.

Enjoy the setup, it sounds awesome!

[phranticness]

Originally Posted by RedOctobyr

These sound like pretty wild power supplies I wasn't aware of ones with such a large voltage range. You had me intrigued, until you got to the $2k part ( I asked what it would take to buy them from by buddies boss, he said about 2k each, but that's what they do, sell rebuilt power supplies and test equipment. I'm honestly not even sure he know which units I was loaned. . I bet they could be found for much much cheaper on eBay. You an I probably don't need accuracy to .001 volts. I'm being facetious, but they do spend quite a bit of time and money to make their rebuilt equipment work perfectly, and they charge for that)

What's the model number of them, for curiosity? 6264B (by Hewlett Packard) They are large, look similar to what you see in Audio racks, they can be stacked like that too. Here is a link to the manual cp.literature.agilent.com/litweb/pdf/5950-1765.pdf They weight about 50 lbs each Even though they are large and heavy, I feel absolutely safe with them. They are commercial grade and have nice safe guards. I still charge on cement though.

And I'm a bit confused. You said you connected them in series, for one big PS. But that you set the voltages to 20V, since that's the best voltage for the PS. But if those were series, that would be 40V, which would blow the PL8. Was that just a typo, and you meant you connected them in parallel? Sorry, typo, I meant Parallel

And I'm sure you know this, but a 5C charge (20A on 4000mAh) is fairly aggressive. It'll be easier on the packs if you charge a few at once, in parallel. That same 20A spread across 3 packs is 1.7C, but you'd only have to manage a single charge (vs 3 in a row), and you'd be done in about the same total amount of time (maybe quicker, due to only 1 CV/balancing phase?) vs charging 3 packs at 5C one after the other. Thank you for the tip, I'm aware that it's easier on packs to charge with less amperage, most the time it's not necessary for me to charge fast, I just wanted the ability. It allows me to only need a couple packs at any one time. Most the time I only fly a couple packs in my yard, but sometimes on the weekend I'd like to be able to charge quicker. I'm also curious to see how my 25c GensAce packs hold up to 5c charging. I'm willing to sacrifice one to see how it effects the life expectancy. Previously I've charged them at 2.5c and had fantastic results. Lastly - I think it's safest to charge one pack at a time - parallel charging is good, and when done in the relm of .5c-1c per pack I think it's pretty safe as long as the condition of all the packs are similar and there are no weak cells. I do own a parallel board and use it occasionally., but I feel the safest charging is balance charging a single pack at a time, safer yet is at 50% of a manufacturers max rate. I do agree though, it's rough on a pack to use it at it's maximum rating of discharge or charge.

Enjoy the setup, it sounds awesome!

Thanks!

[phranticness]

Originally Posted by RedOctobyr

These sound like pretty wild power supplies I wasn't aware of ones with such a large voltage range. You had me intrigued, until you got to the $2k part

I found them on ebay for about $200

They can be stacked up to 3 in parallel or series with one as the master controlling the other two.

[ame]http://www.ebay.com/itm/HP-6264B-DC-Power-Supply-/251209286967?pt=LH_DefaultDomain_0&hash=item3a7d3d 8537[/ame]


Now I'm looking at all the power supplies on eBay. I got sucked into the eBay vortex.