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 Post subject: Re: Power question
PostPosted: Tue Aug 27, 2013 6:41 pm 
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Todd, Chris, Bobby...thanks!!!! This makes a whole lot more sense now.

And Alan, I'd like to know that as well. I've been wanting to convert a power supply that I have from an old computer but I think it's only about 200W so I'm not sure if the effort is worth it.

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 Post subject: Re: Power question
PostPosted: Tue Aug 27, 2013 11:26 pm 
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TheBum wrote:
I was mainly wondering if 1500W of power supply wattage would be enough to drive 1100W of charging power.

Revolectrix has a great power supplycalculators for their Powerlab 8 and 6. Fooling around with the calculator: a 7S battery charging at 37.4A is 1100W of output power, and according to the calculator it would require 54A at 24vdc (1296watts). It looks like they are using a 85% efficiency factor.


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 Post subject: Re: Power question
PostPosted: Wed Aug 28, 2013 6:50 am 
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tgiencke wrote:
TheBum wrote:
I was mainly wondering if 1500W of power supply wattage would be enough to drive 1100W of charging power.

Revolectrix has a great power supplycalculators for their Powerlab 8 and 6. Fooling around with the calculator: a 7S battery charging at 37.4A is 1100W of output power, and according to the calculator it would require 54A at 24vdc (1296watts). It looks like they are using a 85% efficiency factor.

Good to know. Thanks.

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 Post subject: Re: Power question
PostPosted: Tue Sep 03, 2013 10:27 pm 
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tgiencke wrote:
[1344watts / 25.2vdc = 53.33amps (I'm limited to 40 amps at 25.2vdc)

40A / (2 batteries x (5Ah x 0.8)) = 5C maximum charge rate.


With the less expensive $140 Powerlab 6 doing the same charging:

1000watts /25.2vdc = 39.68amps (limited to 33A by the 24vdc power source)

33A / (2 batteries x (5Ah x 0.8)) = 4.13C maximum charge rate.


Todd, I like your direction there. Here's a few minor updates to the math above. Both the Powerlab6 and Powerlab8 are capped at 40 amps of output. For the Powelab8 that means the maximum output is 25.2v X 40 = 1008 watts. The Powerlab6 is slightly different in that it has an input current limit of 40 amps. My measured results show the charger performing at 90% efficiency, which works out to be 860 watts to a 6s pack when used with a 24v source. Check out my test (including graphs) here http://www.rcgroups.com/forums/showthre ... st20578347

I'm currently testing the new Dual Powerlab8 (2688 watts) which is due out soon. It has an input current limit of 40 amps per channel (80 amps combined). However it's input voltage is significantly higher at 48v. During the beta I used two 48v server supplies running in parallel (using the load sharing function). Current draw is much less at about 23 amps per channel putting out 1008 watts to the packs. More details about the charger.

http://www.usastore.revolectrix.com/Pro ... PowerLab_8

Image

My Dual Powerlab setup http://www.rcgroups.com/forums/member.php?u=171800


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 Post subject: Re: Power question
PostPosted: Wed Sep 04, 2013 7:44 am 
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railfan1975 wrote:
I've been wanting to convert a power supply that I have from an old computer but I think it's only about 200W so I'm not sure if the effort is worth it.

(Sorry for the late reply)

Sure, give it a try. Do you know the specs for the 12vdc output of the PC power supply?

Just to be safe, I would place the power supply on concrete outside, then increase the rate you are charging while checking how hot the power supply is getting. If the power supply goes up in smoke no damage is done.

This is another good thing about the Powerlab chargers, you can set the maximum input current for use with smaller power supplies.


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 Post subject: Re: Power question
PostPosted: Wed Sep 04, 2013 9:45 am 
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Gregor99 wrote:
The Powerlab6 is slightly different in that it has an input current limit of 40 amps. My measured results show the charger performing at 90% efficiency, which works out to be 860 watts to a 6s pack when used with a 24v source...

I'm currently testing the new Dual Powerlab8 (2688 watts) which is due out soon. It has an input current limit of 40 amps per channel (80 amps combined). However it's input voltage is significantly higher at 48v. During the beta I used two 48v server supplies running in parallel (using the load sharing function). Current draw is much less at about 23 amps per channel putting out 1008 watts to the packs.

It is interesting that the Dual Powerlab 8x2 ("The Dual") is also limited to 40A input; I'm sure they made this decision to keep the price reasonable (less than the iCharger 4010 Duo).

The really significant thing about The Dual & 4010 Duo is not the output current, it is the 48vdc input. Because of Peukert's Law four 50Ah deep cell batteries (48vdc) will have much more capacity then a two 100Ah deep cell batteries (24vdc) system because the current draw will be ~1/2. Again being able to use cheaper deep cell batteries or getting much more usable capacity.

The only advantage the Powerlab 8 v2 60 amp input has is with 24vdc or less input sources where the input current can go >40A.

Also be careful with >30vdc, it can kill you. (The nurse made me say it).

What is the efficiency of The Dual while using a 48vdc source and charging a 6S battery?

At what voltage does The Dual give an input over voltage warning? Four fully charged deep cell batteries is 50-54vdc without a load.

Where I see The Dual or 4010 Duo really being significant is the club field that doesn't have AC. Either charger with two paralleling boards and four 100Ah deep cell batteries at 48vdc can support 4 fliers with a full day of flying. Then bring the deep cells home and wire them in parallel and charge them with a cheap car battery charger during the night. Because the decreased amp draw @ 48vdc the deep cells will last a long time.


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 Post subject: Re: Power question
PostPosted: Wed Sep 04, 2013 6:35 pm 
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The really significant thing about The Dual & 4010 Duo is not the output current, it is the 48vdc input. Because of Peukert's Law four 50Ah deep cell batteries (48vdc) will have much more capacity then a two 100Ah deep cell batteries (24vdc) system because the current draw will be ~1/2. Again being able to use cheaper deep cell batteries or getting much more usable capacity.

That and it completely eliminates the buck/boost transitions. http://www.helifreak.com/showthread.php?t=546537&page=2


Also be careful with >30vdc, it can kill you. (The nurse made me say it).

Definitely worth repeating. This one of the reasons the two 6s packs in my 12s models are never wired in series until they are connected to the model and the model is "live". During the beta testing I was careful to insulate the output of the two server supplies. I know some leave them open, but those are only 12v. No need to take chances.

What is the efficiency of The Dual while using a 48vdc source and charging a 6S battery?
Same as the Powerlab8. My test results show approximately 90%-91%. Note that the FMA calculators use 85% efficiency. However I've never been able to get my Powerlabs to do anything less than 90%. That includes charging a 3s with a 24v source as well as 6s using a 12v source.

At what voltage does The Dual give an input over voltage warning? Four fully charged deep cell batteries is 50-54vdc without a load.
That's still under review by the FMA engineers.

Where I see The Dual or 4010 Duo really being significant is the club field that doesn't have AC.
Decreased amp draw and operating out of the buck/boost transition range are other huge advantages which apply to running off generators as well. If you've ever heard a Honda running in ECO mode when the transitions hit, you'll know what I am talking about. Sounds like the poor thing is about to die. All that is gone.


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 Post subject: Re: Power question
PostPosted: Sat Sep 07, 2013 7:07 pm 
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Ok, so I've got a quick question. Probably simple really... I have this charging cable --> http://www.progressiverc.com/parallel-6x-jst-charge-cable.html and I have this parallel board --> http://www.progressiverc.com/universal-parallel-charge-board-for-jst-xh.html with bullet connectors on it. Can I charge my 3 2S packs with this JST cable plugged into only one of these connectors while the balance leads are each connected to three different ports? Or does each battery's main charge lead need to be on it's own separate power connector?

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 Post subject: Re: Power question
PostPosted: Sat Sep 07, 2013 7:40 pm 
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You can charge just like that without a problem. That is basically how they are connected in the parallel board anyway.

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 Post subject: Re: Power question
PostPosted: Sat Sep 07, 2013 8:23 pm 
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That's pretty much what I thought, but wanted to ask for sure.

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