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Old Apr 02, 2013, 06:19 AM
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i wished that they keep the 100w discharge on PL6 i dont mind a bigger sized PL6.
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Old Mar 02, 2014, 07:36 AM
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Quote:
Originally Posted by Gregor99 View Post
On the commonly available server supplies running 24v, the Powerlab6 will give you 860 watts. 
hello Gregor,
i was wondering how to do this calculation.
what i currently do is to disregard 10% of the PS output current. so, if my PS is said to provide 40a, i consider for practical use only 36a (due to heat and other sort of losses). Is it what you call efficiency?
thanks.
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Old Mar 02, 2014, 11:28 AM
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Quote:
Originally Posted by Can'tFly View Post
hello Gregor,
i was wondering how to do this calculation.
what i currently do is to disregard 10% of the PS output current. so, if my PS is said to provide 40a, i consider for practical use only 36a (due to heat and other sort of losses). Is it what you call efficiency?
thanks.
The 860 number in the first post was measured, not calculated. Test results and more details are in this thread.

http://www.rcgroups.com/forums/showp...&postcount=251

To calculate efficiency, convert the input and output to watts, then compare the difference. For the PL6 on 24v its 24v X 40a or 960 watts. The efficiency losses occur inside the charger. So if the charger is consuming 960 watts from the power supply, the charger output will be about 90% of that value, or 864 watts. The actual value in my test was a tad lower than that, likely because the supply voltage may dropped slightly below 24v under load.
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Old Mar 02, 2014, 04:58 PM
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Originally Posted by Gregor99 View Post
The 860 number in the first post was measured, not calculated. Test results and more details are in this thread.

http://www.rcgroups.com/forums/showp...&postcount=251

To calculate efficiency, convert the input and output to watts, then compare the difference. For the PL6 on 24v its 24v X 40a or 960 watts. The efficiency losses occur inside the charger. So if the charger is consuming 960 watts from the power supply, the charger output will be about 90% of that value, or 864 watts. The actual value in my test was a tad lower than that, likely because the supply voltage may dropped slightly below 24v under load.
hello Gregor,

i never bothered about those numbers before, but now that i have an fma charger i'm interested in knowing more about the charging/balancing procedure. i've been reading about this subject for a few weeks now. the graphics showed in the link above were produced by the pl8 software, right? i'd like to do a test like yours on my own. all i have to do is to charge a battery with the charger hooked to the pc?

i have another question, please. the manual says:

At the Supply Current Limit? screen, press INC or DEC to specify the current limit appropriate for your DC power supply, then press ENTER. (Cutoff current should be slightly less than the power source’s maximum output current capability. To protect your power supply from damage, PowerLab 8 will never draw more current than you specify here, but charge current may not reach the preset or manually set value.)

what would be "slightly less" on a 41a-24v (meanwell-1000-24) PS? how about a 50a-27v PS?

thanks.
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Old Mar 02, 2014, 06:12 PM
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Most of the graphs were created with the CCS. With the PC connected to the charger and the CCS operation start the charge. Either from the console of the charger or the CCS on the CELLs tab. The CCS will prompt you for a filename. You can watch it live as well as open it later. Open the graphs from the View Menu.

There is one graph in that post that was created in Excel. Within the CCS you can export the charge log to CSV or West Mountain format. From there you can import multiple charge logs into Excel and overlay the results. The West Mountain software is free and worth at trying at least one. Export a charge log then import it into the West Mountain tool. It has a slightly different view of the data which I like.

Set the charger's input current limit to the max value you want to pull from the supplies. I'm running server supplies which are very hearty and inexpensive. So won't feel bad if I push them and they fail. For a Meanwell, I'd feel differently and perhaps set the current limit a little lower. Leave the low voltage value at the default (11v I believe).

But its also important to know how its going to impact your charging scenarios. For instance, charging 6s packs from a 24v source you'll max out at about 46 amps from the supply. Setting the limit to 46 then would have no impact on your charging scenario. However on the 1000 Meanwell, the same scenario (6s packs) is already going to be constrained by the supply. Setting the limit 41 amps the Powerlab8 will not be able to reach the full 40 amps of output. Lowering to the high 30s further impacts the total charge available.

The "right" setting is often the product of a bit of negotiation with yourself, and involves the details of your charging scenario and desires to protect the supply. In an ideal world, you would leave roughly 10% overhead on the supply. But in some cases that's not practical or desirable.
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