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question on charging batteries

Old 05-02-2021, 03:08 AM
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orthobird
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Default question on charging batteries

Question here

lets say I have 5s LIPO batteries, 5000 MAH

and I have 8 of them.

If I charge only one pack at 5C, the charger can charge it at 45 minutes from 30% to 100%

lets say, my power supply is 12 volts and it states 20 amps

what if???

i put 4 packs to charge at same time, 5s batteries, each one is 5000 mah

will my power supply be able to charge all 4 packs at 5C with the rating of 20 Amps?

and, how long will it take?


What if, I have 8 packs I want to charge at same time
but this time, the power supply is 24 volts at 60 Amps?
how long will it take?

Old 05-02-2021, 04:37 AM
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A. J. Clark
 
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None of your 3 examples will work.
A 12v supply couldn't raise the voltage high enough to charge a 5 cell battery.
A 12v 20a supply wouldn't have the voltage or current capacity to charge 4 5cell batteries at one time.
A 24v 60a supply wouldn't have the current capacity to charge 8 batteries at one time. And 24v would be marginal.
Old 05-02-2021, 04:53 AM
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orthobird
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Originally Posted by A. J. Clark View Post
None of your 3 examples will work.
A 12v supply couldn't raise the voltage high enough to charge a 5 cell battery.
A 12v 20a supply wouldn't have the voltage or current capacity to charge 4 5cell batteries at one time.
A 24v 60a supply wouldn't have the current capacity to charge 8 batteries at one time. And 24v would be marginal.
very interesting you say that.

I wonder what others will say. With all due respect to you.

I have charged, many times, 4 packs of 5s batteries, at 5000 mah packs each, with a 12 volt power supply. it took about 1:30 hours.

using this: 12 volt supply, 20 A
Old 05-02-2021, 05:28 AM
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A. J. Clark
 
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Originally Posted by orthobird View Post
very interesting you say that.

I wonder what others will say. With all due respect to you.

I have charged, many times, 4 packs of 5s batteries, at 5000 mah packs each, with a 12 volt power supply. it took about 1:30 hours.

using this: 12 volt supply, 20 A

Well that's very amazing to me and you were charging 4 5000 mah batteries at a 5c rate (100amp initial charge) and reaching 21 volts at final charge per battery on a 12v 20a supply???
Old 05-02-2021, 05:44 AM
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orthobird
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Originally Posted by A. J. Clark View Post
Well that's very amazing to me and you were charging 4 5000 mah batteries at a 5c rate (100amp initial charge) and reaching 21 volts at final charge per battery on a 12v 20a supply???
yes sir.

I know. I do not know how either, but it does it.

the batteries are 100% charged, using the Powerlab 8 charger. and the voltage is 21 volts per 5s pack.
Old 05-02-2021, 05:49 AM
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Well what can I say if it's working for you you are getting your monies worth from that supply. If it's working carry on I guess.

Last edited by A. J. Clark; 05-02-2021 at 08:34 AM.
Old 05-02-2021, 05:54 AM
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orthobird
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thank you Clark. My question, however, remains unanswered. I have a new power supply and a new charger. And I would like to know if by using the 60 amp / 24 volt power supply, i could charge 8 packs or 6 pack or 4 packs or even 1 packs, and because it is 60 amp, the charge rate would remain same??

I am not an electrician or an engineer, although I play one on TV. Just kidding. I really am not an electrician or an engineer. And I am definitely not an actor. But, and I do not know the answer, does using a 60 amp power supply make a difference, as opposed to using a 20 amp charger?

If i try to charge 4 packs with the 20 amp 12 volt PS, it takes 4 ever.

So would using the 60 amp PS, charge 8 packs the same as 1 pack??
Old 05-02-2021, 06:05 AM
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Other than my first reply I don't have any other answers. I am sure there other members here that that have a better understanding of batteries and chargers that will be able to help you.
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Old 05-02-2021, 12:01 PM
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The charger must have a DC - DC converter to step up the voltage for the higher voltage packs. From there it is just a matter of how much total wattage your charger can handle and how much wattage your power supply can supply. I haven't done the mate to comment further.
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Old 05-03-2021, 04:57 AM
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By charging at a 5c rating your overloading the power supply. You could try charging at a 1c rate. You might find that at 1c it will change faster.
Old 05-03-2021, 02:01 PM
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I hope you read all of this.
Assuming the the bench-top power supply is providing 13.8v @ 20A, it is rated at 276W (watt) maximum.
Using "Watts" allows you to compare apples to apples between the power supply and the load (the "load" is the Changer and the batteries).

Any modern changer (Junsi, Powerlabs - etc) use a Constant Current (CC) charge mode for the first part of the change and then switches to Constant Voltage (CV) for the last part.
This allows the charger to provide the programmed current until one or more of the cells in the pack reaches the maximum voltage (typically 4.2v) and then it switches to CV mode until all the cells reach the same maximum voltage (4.2v) as measured and controlled by the balancer circuits and the voltage measured at the main discharge lead.
During CV mode, you will see the current dropping as the cells in the pack start to reach the programmed max voltage and the pack's total voltage (21v for 5S1P) is approached.

Assuming you are charging one (not five) 5S1P 5000mAh pack at "5C", the charger would be trying to put out 25A starting at around 19V (CC mode) and ramping up over time until it changes to CV mode (when 1 cell reached 4.2v). Then it starts dropping the charge current.
With 5C on a 5000mA pack, that's 475 Watts at the start and then ramping up to around 525W when it shifts to CV mode.
That is not possible with only a 276W power supply as the input to the Powerlabs 8 charger.
The best rate you could charge one 5S1P 5000mAh LiPo is about 2C with that power supply (about 12A charge rate (2C) at 21v)

So, you are not really charging a 5S 5000mAh LiPo at "5C". You think you are, but you are not.
Even you said it yourself: "If I charge only one pack at 5C, the charger can charge it at 45 minutes from 30% to 100%".
Assuming you start at 30%, the 5000mAh pack was discharged to 1,500mA remaining (70% of 5000mA). To go from 1,500mA to 5000mA, you have to add 3,500mA.

Charging one 5S1P 5000mA LiPo at a true rate of 5C (25A (aka: 25,000mA)) would take about 8.4 minutes (3,500 / 25,000 x 60 = 8.4 min).
Assuming your actual true charge rate is closer to 2C (10A) - the maximum the power supply can provide - then it would take you around 21 minutes to put back 3,500mA into the pack (3,500 / 10,000 x 60 = 21 min)
But, it is taking 45 minutes to recharge the 5S1P 5000mAh LiPo from 30% (1,500mA remaining) to 100% (5,000mA). That implies it is really charging at around 1C (3,500 / 5,000 x 60 = 42 min)
Besides...
Labels on almost every consumer grade RC LiPo are 100% BS.
If they say its a 5C discharge rate, it may only deliver 1C or 2C in real-life (get yourself an ESR / IR meter and measure it).
And there are no labels that say you can charge their LiPo packs at anything greater than 3C - and even that's a lie.
If you actually tried to charge a 5S1P LiPo at 5C, it would quickly overheat and burst into flames.

I have an iCharger 308 Duo with a pair of Dell server AC to DC power supplies.
Each power supply is rated at 12v @ 65A. In series, they provide 24V at 65A. Effectively, they are a 24v 1500 Watt power supply.
The reason I chose these two power supplies is that the typical 120v AC outlet in a residential house it rated at 15A. At 12VAC and 15A, that's 1800Watts (about as much as your wife / girlfriend / daughter's blow dryer from Walmart).
That means my iCharger 308 Duo will charge both channels at is full rated output of 1300W (30A per channel and 50A max).
My iCharger 308 Duo cannot change five 5S LiPo in parallel.
Theoretically, an iCharger (Junsi) 308 Duo could charge a single 5S1P 5000mAh pack at 5C on each channel - so that would be 2 packs at a time (30A per channel).
Of course, I wouldn't have a garage to come back to after the batteries exploded and burned the house down.

You may want to read the Powerlabs 8's user manual:
Power supplies PowerLab 8 is one of the highest power RC battery maintenance devices available. Running full power, it can deliver 1344W to batteries during charge. To achieve this, even on an 8 cell Li battery, it must boost the input voltage. This means the PowerLab 8 may draw up to 1600W from the input power supply. To take advantage of PowerLab 8ís full power capability, the power source should be 26.35V DC (higher voltage does not improve output power), and capable of delivering a minimum of 60A to PowerLab 8ís input. Per Ohmís law, 26.35V x 60A = 1581W. However, it is generally not advisable to pull 100% of available power from a DC power supply. Therefore, if you want to attain 1344W of output power to an 8s Li battery, the power supply should be capable of 1700W or higher for best results. Likewise, if you donít need PowerLab 8ís full output power, it can operate from much lower power sources. Use the steps outlined in Set Smart Power Management to configure PowerLab 8 to never exceed the maximum capabilities of your input source(s), whether DC power supply or Lead Acid battery. For more information about power supply selection, please download the PowerLab 8 Power Calculator spreadsheet found at the PL8 Resources tab on the REVOLECTRIX website

Last edited by ticedoff8; 05-03-2021 at 02:08 PM.
Old 05-03-2021, 02:32 PM
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orthobird
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thank you for the excellent explanation. I knew someone on here would know the answer.

SO i now have this power supply and this charger:





Sounds to me like I can only charge one pack at a time, in order to get it to charge quickly.

Old 05-03-2021, 05:05 PM
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The iCharger 4010 Duo is rated at 2000W - slightly higher capacity than my iCharger 308 Duo (1300W).
There is no way for me to tell (from the picture) what that power supply is rated at.
But, if that power supply is using a 120v AC 3-prong plug, it most likely is rated at less than 1800W - how much less, I can't say. Regardless, you won't get the full capacity of the 4010 Duo.
To get a 2000W AC / DC power supply, it will need to be able to plug into a 220V outlet (like your clothes dryer or stove's plug)

The PowerLab 8 is as good as the iChanger 4010 Duo and better than iChanger 308 Duo and should be up to the task for anything you want as long as it has a power supply to match.
But, as I said, trying to charge any hobby-grade LiPo pack at 5C is a bad idea.
Sounds to me like I can only charge one pack at a time, in order to get it to charge quickly.

Assuming you were thinking of trying to charge one pack at a time at 5C, it would still take about 9 minutes per battery (assuming one or two of the batteries didn't burst into flames).
Or.... you could it a safer and well supported way.
If that power supply connected to the iCharger 4010 Duo is up to the task (1800W or better), you can charge four 5S1P 5000mAh LiPo at the same time.
Hook 2 packs up in parallel (using Y-cable balancer leads and Y-cable main leads) on each channel at the same time.
With the 2 packs connected to the Y-cables balancer balancer and main leads, it is effectively 5S2P and you would charge them like a 5S1P 10,000mAh pack.
Charge each channel at 2C to 3C based on the 5000mAh capacity (effectively 1C to 1.5C for a 10,000mAh pack) and it would take about 40 minutes per channel.
Using this configuration, the effective throughput is still around 10 minutes per pack and you'd have four 5S1P LiPo fully charged in about 40 minutes with a much lower risk of catastrophic failures.

I don't know what your application is, but I fly helicopters with two 6S1P LiPo packs (effectively 12S1P).
If I am at the field, I take 3 sets of batteries and rotate them on to the charger after every flight. I have less than 15 minutes between flights all day long as I fly & charge.

Last edited by ticedoff8; 05-03-2021 at 05:34 PM.
Old 05-03-2021, 05:12 PM
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orthobird
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thank you so much

the PS is 65 amps at 24 volts output
input is 110 V

but all the information is very helpful to me and I appreciate you, as now I understand better.

best regards,

Cam

Old 05-03-2021, 06:05 PM
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Originally Posted by orthobird View Post
the PS is 65 amps at 24 volts output
input is 110 V
24v x 65A = 1,560W
Not quite equal to the iCharger 4010 Duo's 2000W requirements.
But, you should still be able to charge four 5S LiPo using the setup I outlined above.
Old Yesterday, 07:43 PM
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i went to the field today, using my setup, it took about 3 hours to charge 4 battery packs, at 5C rate, from 20% to 100%
each pack is 5100 MaH
5S packs

I understand it does not actually charge at 5C, but that is the setting i programmed it at.

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