Battery Load Tester Question

[rg12]

I have bought this capacity tester:
https://www.aliexpress.com/item/32495202056.html?spm=a2g0s.9042311.0.0.16b64c4dGIMtgC

and I have opened it and found out that it has two of those large green resistors inside.
Now from what I know is that in order to have variable current with resistors you have to connect more or less resistors in series and that the current can't be changed as it's not based on mosfets that can do that.

So, how is it possible?
I have a huge load tester I build from 10 1500w resistors and I have made a fancy relay switch box to turn 1-10 resistors in order to controller only to find out that it's possible with some arduino style thingy and the same resistors I use.

*I have seen about 4 large resistors with a heat sink in there but it's obvious they don't take the actual load as this device is built for constant current of 20A at 72V

 

[john61ct]

Is that the same as

https://m.aliexpress.com/item/32495202056.html

?

I believe the maker is TZT, aka Shenzhen Tianzhongtian Trading Co., Ltd.

also brand ZKEtech http://zketech.m.icoc.in

They have a good rep.

Personally I am trying to identify their highest current dummy load designed to CC test single cells, so voltage range from 1V to say 4.5V

Why are you trying to figure out how they work internally? afaic as long as they do work correctly, I'm happy

 

[rg12]

Is that the same as

https://m.aliexpress.com/item/32495202056.html

?

I believe the maker is TZT, aka Shenzhen Tianzhongtian Trading Co., Ltd.

also brand ZKEtech http://zketech.m.icoc.in

They have a good rep.

Personally I am trying to identify their highest current dummy load designed to CC test single cells, so voltage range from 1V to say 4.5V

Why are you trying to figure out how they work internally? afaic as long as they do work correctly, I'm happy

Because I thought it isn't possible to have variating current instead of just analog on off for each resistor in parallel.
As I mentioned, I have a setup of a control box I built for x10 1500w resistors and used relays while I would be happier just having an LCD that enables me to type in any current I want up to the max limit.
With a 72V I can pull around 160A since I have x10 5ohm resistors in parallel

 

[Pajda]

So you basically did not try if it works? I think it deserves a chance. :wink:

 

[rg12]

So you basically did not try if it works? I think it deserves a chance. :wink:

The device I bought from the link works but I'm not big electronics wiz but do know that there is a reason why most of those resistors banks are controlled with dumb AC switches instead of a small circuit to control it.

I guess they used a mix of fets and resistors while the fets control the resistors insted of dissipate the heat themselves.
but still, pretty good idea to save on having a million large resistors and a mega expensive device.

 

[batteryGOLD]

I have bought this capacity tester:
https://www.aliexpress.com/item/32495202056.html?spm=a2g0s.9042311.0.0.16b64c4dGIMtgC

U just did a perfect bought!
That is the right tool you need including PC software

This Chinese stuff do work great!

How much total cost to your country including tax's?

Do you have picture inside equipment?

 

[DogDipstick]

and I have opened it and found out that it has two of those large green resistors inside.



I have a huge load tester I build from 10 1500w resistors and I have made a fancy relay switch box to turn 1-10 resistors in order to controller only to find out that it's possible with some arduino style thingy and the same resistors I use.

*I have seen about 4 large resistors with a heat sink in there but it's obvious they don't take the actual load as this device is built for constant current of 20A at 72V

Good to see some straightforward testing here. Thats the way to do it, Roy. I got tht same (10) 1400w resitor bank... Plus now I got some more.. I could datalog up to 30kW and I use a Cycle analyst ( no Arduino). 125$, and all the data I need neatly laid out. Tells me everythign, including IR. Thts the way, I'm telling you. Invest in your custom datalogger bank, with your resistance math.

I hardwired the bank for any particular test voltage and current. For that particular test that day.


Just do the math, Rg.

That is the right tool you need including PC software

This Chinese stuff do work great!


Do you have picture inside equipment?

BAHAHAHAHA
Its a wimpy tester. Lol. 20A aint nothing.

I can datalog on my Powerlabs up to 32s and 40A over four channels. Lol. Or the homemade resistor bank, up to 30kW and upwards of 250v. Datalogged. Or spreadsheet. Rips that lil testing machine out the competition.

Dammit, Revolectric is out of business. They were good.. They had a hard time.. Staying.. in stock. I Sooooo wish China would start cloning them, and selling to the world. 4 channels, 40A, 6000w. Datalog.


yeah lets see the pics of the inside.

 

[DogDipstick]

They have a good rep.

Personally I am trying to identify their highest current dummy load designed to CC test single cells, so voltage range from 1V to say 4.5V

Cause its fun to reverse engineer circuits to see how they work, Ya know?

I could build you a helluva load bank. I use a server rack.... Predrilled, strong, excellent base, on casters, with threaded holes for mounting the loads... Its filled with .. Red hot things (1.1kW-3.300kW resistances, 20+ of them) and fans.


Single cell? Dont need more than ~1kW CC load @ 3.7v. Not many cells can do 1000w or greater, alone, for long.

Sitting over there a crackling and a pingin as she heats up.... You can feel it ( the heat) from 10 feet away. Lol.

 

[john61ct]

Portability more my style, fit for #vanlife

 

[rg12]

and I have opened it and found out that it has two of those large green resistors inside.



I have a huge load tester I build from 10 1500w resistors and I have made a fancy relay switch box to turn 1-10 resistors in order to controller only to find out that it's possible with some arduino style thingy and the same resistors I use.

*I have seen about 4 large resistors with a heat sink in there but it's obvious they don't take the actual load as this device is built for constant current of 20A at 72V

Good to see some straightforward testing here. Thats the way to do it, Roy. I got tht same (10) 1400w resitor bank... Plus now I got some more.. I could datalog up to 30kW and I use a Cycle analyst ( no Arduino). 125$, and all the data I need neatly laid out. Tells me everythign, including IR. Thts the way, I'm telling you. Invest in your custom datalogger bank, with your resistance math.

I hardwired the bank for any particular test voltage and current. For that particular test that day.


Just do the math, Rg.

That is the right tool you need including PC software

This Chinese stuff do work great!


Do you have picture inside equipment?

BAHAHAHAHA
Its a wimpy tester. Lol. 20A aint nothing.

I can datalog on my Powerlabs up to 32s and 40A over four channels. Lol. Or the homemade resistor bank, up to 30kW and upwards of 250v. Datalogged. Or spreadsheet. Rips that lil testing machine out the competition.

Dammit, Revolectric is out of business. They were good.. They had a hard time.. Staying.. in stock. I Sooooo wish China would start cloning them, and selling to the world. 4 channels, 40A, 6000w. Datalog.


yeah lets see the pics of the inside.

I guess a CA is a better option than my aliexpress watt meter I mounted since no data logging.

but if we are here, any idea on how can it be done to achieve variable current like the unit I bought that also uses resistors but has digital variable voltage?
I think it's a PWM using the resistors to turn the resistors on an off instead of having the fets take the load so they only switch the load which is the resistors.
If that's the case, how complex is it to plan a circuit and an arduino code for this?