AC to DC, why are amps very low?

[abwillingham]

I bought this DROK 20amp AC to DC charger that Will P mentioned in his video to charge my new 200AH lifepo4 pack.

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I am doing a top balance charge and this charger is only charging at around 3 amps at 3.65v. The voltage on the battery is currently around 3.3v. Its been charging for a couple of days now.

Why is it not charging at the rated 20amps?

Thanks
Tony

 

[houseofancients]

I bought this DROK 20amp AC to DC charger that Will P mentioned in his video to charge my new 200AH lifepo4 pack.

Amazon.com: Adjustable Voltage DC Power Supply, DROK AC 110V-220V to DC Output 0-24V, LED Digital Display 12V 24V 20A 480W Switching Power Supply Regulated Converter Step Down Transformer Built in Cooling Fan : Electronics

Buy Adjustable Voltage DC Power Supply, DROK AC 110V-220V to DC Output 0-24V, LED Digital Display 12V 24V 20A 480W Switching Power Supply Regulated Converter Step Down Transformer Built in Cooling Fan: Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I am doing a top balance charge and this charger is only charging at around 3 amps at 3.65v. The voltage on the battery is currently around 3.3v. Its been charging for a couple of days now.

Why is it not charging at the rated 20amps?

Thanks
Tony

did you put on proper size cabling and ring terminals ?

 

[abwillingham]

Perhaps. What is the proper size cabling and rings terminals?

 

[houseofancients]

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

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and ring terminal that go with the wire size

as you have a 20A charger your minimum should be 12 AWG, but i'd recommend 10 AWG

 

[abwillingham]

I am only using 18 AWG. Would that really cause the amps to decrease from 20 to 3? The terminals on the charger are tiny. I don’t think a 10/12 AWG wire terminal will fit on them.

 

[Pierre]

You cannot adjust the current on this charger , therefor it is not a constant current device as required for charging during the bulk charge stage of the charge cycle. The current will be solely determined by the load resistance i.e. the cell voltage and cable / clamp loop resistance. You will be better off with a CC/CV device. One would expect the current to start tailing off as the cell gets fuller. The only way to increase the current will be to increase the supply voltage which is NOT ADVISABLE.

 

[John Frum]

Here is a calculator that will let you explore how voltage drop is effected by voltage, amperage and round trip circuit length.

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[Theo74]

The basic formula for currents tells: I (amps) = U (volt) / R (resistance)
So the higher your (cable) resistance is, the lower the current will be.

Thin wires have a bigger cable resistance then thick wires, when looking to the bigger currents.
Like the bottle-neck effect. A lot of water needs to run through a small hole, so it's slowed down.

When using thicker cables, you also should use bigger wire terminals, to avoid the slow-down there also.

 

[John Frum]

This is an FAQ.

 

[abwillingham]

You cannot adjust the current on this charger , therefor it is not a constant current device as required for charging during the bulk charge stage of the charge cycle. The current will be solely determined by the load resistance i.e. the cell voltage and cable / clamp loop resistance. You will be better off with a CC/CV device. One would expect the current to start tailing off as the cell gets fuller. The only way to increase the current will be to increase the supply voltage which is NOT ADVISABLE.

Pierre, would this work well for bulk charging? https://www.amazon.com/dp/B08TRPJKNP/ref=cm_sw_em_r_mt_dp_WW0G5Q45DP2R6TS0AEVS?_encoding=UTF8&psc=1

 

[John Frum]

Pierre, would this work well for bulk charging? https://www.amazon.com/dp/B08TRPJKNP/ref=cm_sw_em_r_mt_dp_WW0G5Q45DP2R6TS0AEVS?_encoding=UTF8&psc=1

I will answer for Pierre as he is probably offline now.
That is a 12 volt charger.
For top balancing you need one that can deliver 3.65 volts constant current, constant voltage.

 

[Pierre]

I will answer for Pierre as he is probably offline now.
That is a 12 volt charger.
For top balancing you need one that can deliver 3.65 volts constant current, constant voltage.

Thanks Joey. The Victron units are expensive and is great for charging a complete pack. But for individual cell charging rather invest in a good quality 0-30v , 10 or 20 amp CC/CV bench top power supply. You will always use it for other projects as well.

 

[Pierre]

Pierre, would this work well for bulk charging? https://www.amazon.com/dp/B08TRPJKNP/ref=cm_sw_em_r_mt_dp_WW0G5Q45DP2R6TS0AEVS?_encoding=UTF8&psc=1

Lovely unit - I use it in my lab. See my earlier comment though.

 

[abwillingham]

I hate to buy a larger cv/cc device just for this one time event. I do have a 5amp cc/cv power supply. I guess I will use that and be patient.

 

[John Frum]

I hate to buy a larger cv/cc device just for this one time event. I do have a 5amp cc/cv power supply. I guess I will use that and be patient.

Read this doco.

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

After you have read it and found the shortcut feel free to ask more questions.

 

[mikefitz]

this DROK 20amp AC to DC charger

Do not use this unit to charge batteries or cells.

Mike

 

[John Frum]

Do not use this unit to charge batteries or cells.

Mike

Why not?
Just saying don't without explaining why is not as helpful as explaining why.
Less chance your warning will be headed as well.

 

[abwillingham]

Do not use this unit to charge batteries or cells.

Mike

Yes, please explain why.

 

[abwillingham]

Read this doco.

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

After you have read it and found the shortcut feel free to ask more questions.

Thank Smooth. I figured out my CC/CV power supply is actually 3A, not 10A, which explains why its charging at 3A.

 

[John Frum]

Thank Smooth. I figured out my CC/CV power supply is actually 3A, not 10A, which explains why its charging at 3A.

Ok you claim 3 amps not 10 amps and the product description is 20 amps.
What gives?