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Nov 20, 2017, 07:46 PM
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Discussion

Chargers


I own a LOT of chargers. 13...
From the starting days of the 50W/5A "4 button" chargers, to the next levels of 150W/10A... 200W/7A... (still "4 button" type)... and then onto the LEMON Radiolink CP620 750W/30A (and has 6A balancing!!!) capable!!

50W chargers can't charge many battery capacities very fast at all....

Some Charger Info:
The Watts rating sets the MAXIMUM POWER the charger can pass. But it also has a Voltage maximum and a Current (Amps) maximum.
So they will most often list Voltage as "2S to 6S" etc (2S to 8S). So then you know how many cells it can charge at most.
And they will list the maximum Current it can pass. eg say 5 Amps.
"Up to 6S at 50W/5A"

Then for any given cell count, thus Voltage, you can derive what it could charge that battery at the most.
So let's use 6S to make it tough for the charger (because it is the highest Voltage it can do).... 6S peak voltage is 6 x 4.2v = 25.2v
To see what maximum Current is POSSIBLE at that Voltage, divide the POWER by the Voltage. 50W / 25.2v = 1.98 Amps
This is because no matter what, the POWER is the top limit of the charger.

There are the THREE limits - Voltage, Current and Power... and NONE can be exceeded. (eg not even just one). The charger itself will stop at its limits.
So the MOST you could feed into a 6S battery with a 50W charger is 1.98Amps....
If it was a 2200mAH battery then that 1.98A max is almost 1C (0.9C). If it was a 5000mAH battery then it is 0.4 C only!

If you charge a battery at 1C - any battery of ANY Capacity - it will take ONE HOUR.
1000mAH then 1C is 1 Amps
5000mAH then 1C is 5 Amps
So this 50W/5A charger, into a 6S 5000mAH battery will take 2.5 hours to charge that!

Even 150W and 200W chargers can't do 5000mAH batteries 'FAST'. That is because they are typically a maximum Current ability of 7Amps or 10Amps.
In my case the 150W can do 10 amps, but the 200W can only do 7Amps!!
If you use 10Amps, on a 150W maximum charger, then the Voltage can only be 15volts (15v x 10a = 150W). But a 4S battery charges at 17volts... so the Current (Amps) cannot even be 10 amps then.... typically you can only get 8 Amps maximum if charging a 4S battery. For 5000mAH that is 1.6C.
1 hour divided by 1.6C = 0.625 hrs = 37.5 minutes
On a 6S... 25.2v... it is 150 / 25.2 = 5.95 Amps = 1.2 C thus 50 minutes.

The Radiolink CP620 can feed up to 30Amps! At 750W, 6S is.... 750w / 25.2v = 29.8Amps.... so it COULD feed 30Amps into any Capacity of 6S battery.
So 5000 (which is 5A) can be charge at up to 6C !!! (30A / 5A = 6)
Technically this is a fantastic HIGH Power charger.... too bad its FIRMWARE (software) has BUGS!!
Last edited by PeterVRC; Nov 20, 2017 at 09:45 PM.
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Nov 20, 2017, 08:24 PM
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Balance charging


Balancing:
A big 'problem' with many chargers is BALANCING the batteries!
Chargers have a Fast Charge mode, where they only charge the whole battery - via its main power leads - until its 'overall' Voltage is 'charged' .Then you just go and use the battery.
But because a Lipo is likely to have MANY cells, this does not charge them all EQUALLY. There can be variation from cell to cell... some lower voltage.. some higher voltage. So the lower charged ones will go flat BEFORE the higher charged ones! And can go 'too flat' and damage them.
A Telemetry system could tell you the VOLTAGE of a 4S battery is "14.9v".... but three cells could be 4.0v and the other 2.9v !! Flatter and being damaged now! (that is a bit of an extreme example... the variations will likely be small, but still do matter)

Balance charging makes the cells ALL the same. (though this does not guarantee they will DEPLETE EQUALLY when used!)
To do this, 'cheaper' chargers charge all the cells, and monitor them ALL and when one or any are fully charged, and others NOT, they stop charging and DEPLETE the full ones to bring them back down to the lower one. Then they resume charging.... to attempt to bring them ALL up to fully charged at the same time.
But some cells charge 'slower'.. so this cycle can be repeated any number of times. With that aim to EVENTUALLY get them all to the same fully charged state.
This process SLOWS DOWN the charging process.... often by a LOT.

Charging at 1C.... should be 1 hour (60 minutes)... but the balancing portion could ADD another 30mins... 50 mins!!
It is relative to the imbalances... and what Current (Amps) the charger can DO the balancing process at.
"Better" chargers can deplete at higher Currents. eg 1A of the ISDT SC-620
Most cheaper "4 button" chargers can only do 100mA, 150mA, 200mA.... thus are SLOW at balancing.

The Radiolink CP620 does a far better system!!
It stops charging FULL cells, and KEEPS charging the not completed ones! At up to 6A per cell !!
Only ever Charging cells, rather than DEPLETING them, is far faster..... plus the high current it can do (6A per cell still).... and means less wear, due to not charging THEN depleting cells over and over!
"GOOD" chargers do this method - though even many costly 'good' ones still do not do it this way!
The CP620 would be an AWESOME charger... if not for its firmware bugs...
It is still very usable anyway really, and no other charger of its capability range is anywhere near as CHEAP!!
Last edited by PeterVRC; Nov 20, 2017 at 09:47 PM.
Nov 20, 2017, 08:25 PM
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Thread OP

Powering a Charger..... a DC Charger


You might get a charger with an INBUILT AC power source to drive it. But they are quite costly, and also limiting in choices.
These are called "AC chargers" - as they can be powered by an AC source.... a power point.

"DC Chargers" means they are powered from a DC source. A DC power supply.
And that power supply would be powered from the AC power point.
This has benefits, and also 'nuisance factors'.
A benefit is that you have more choices.... and can use one large DC supply to power multiple DC chargers. But then will use up more space generally.

A charger takes the DC Voltage and converts that to whatever Voltage it needs to charge the battery at. 3S 12.6v.... 6s 25.2v..... even if the charger was only a 12v source!
Most chargers can accept a RANGE of DC input Voltages. eg 10v to 18v.... or 10v to 30v etc.
So a common supply source used is 12v.
But there are various output types around too.... 15v... 18v...

Because the charger MULTIPLIES the input Voltage, if required, it becomes inefficient if that multiplication is large. So you will find that even though a 12v SOURCE can provide the 6S, or 8S, battery Voltage the CHARGER will not allow its full capability in POWER/Amps because the inefficiency will make it overheat.
So many higher power chargers - say 300W upwards - need a HIGHER DC input Voltage if you want to be able to HAVE the 300W. eg maybe only 200W at 12v, but 300W at 24v
You really want a 24v DC power supply for HIGH power chargers.

The main factor/spec to know about a DC Power Supply is the WATTAGE. You only really need to know that part as the Voltage 'doesn't matter' to the charger - except to be 24v for high power chargers. If the Power Supply is 500W then it will supply 24v of X Amps which will be what the charger needs to charge at 500W.
eg if 6S 5000mAH... '500W'.... that is 500w / 24v = 21 Amps from the power supply. That 500w means the battery, charging at 25.2v is drawing 500w / 25.2v = 19.8a
So you might see the LINK in Watts going IN and OUT of the charger - that is equal..... but the CURRENTS (Amps), in and out, is relative to the VOLTAGE charging the battery.

Here are some very good value DC power Supplies:

480W 24v 20a
https://www.ebay.com.au/itm/DC-1A-3A...72.m2749.l2649

600W 12V 50A
https://www.ebay.com.au/itm/DC-1A-3A...72.m2749.l2649

Remembering the 600W 12v version will NOT be able to drive a 300W CHARGER to its maximum abilities!!
But it could drive THREE 200W chargers all to their maximums.
You sort of need to THINK a bit about how you will set up your charger and supply 'balances'.

I nice twin setup is:
The 480w 24v 20A supply into TWO ISDT SC-620 chargers. Or into ONE Radiolink CP-620 charger.
This allows charging at the maximums of the two ISDT's, or still WAY UP in the scale of what the Radiolink can potentially do.
The Radiolink at 750W capability is almost TOO powerful and you would rarely - if ever - use that!
Last edited by PeterVRC; Nov 20, 2017 at 10:12 PM.


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