High current tester modding

Overmind

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Jan 16, 2019
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Did anyone attempt to mod a tester like the Lii500 or Opus or anything like that to make it support higher discharge test current, like 2A or even more ?

Most of the chargers on the market only test on all slots at 0.5A; Opus needs extra cooling for 1A across all slots.
It would be nice to be able to mod them.

Any thoughts ?
What would happen if we would replace the discharge resistor with another to allow higher current ?
Could it work on any of the currently available chargers or is that a too complex matter to to other charger internal construction limitations ?
 

daromer

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Its easier to just buy a high current tester to be honest. Like the ZBl3 or what not.
 

Overmind

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ZB2L3 is not currently available anywhere near me (as in my country).

Guess I could build a multi-slot out of these, but I'd prefer something already manufactured for now.
 

daromer

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Hook up several Ichargers then :) Then you can get up to 40A testing current per cell ;) Or run the duo and get 70A ;)
 

Korishan

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it would be very difficult to modify the opus or liitokala to do higher amp discharge because of the programming and circuitry and traces. It was designed with 1A in mind and trying to modify it could make it act all wonky.

It would be much easier and probably far more accurate to use an MCU (arduino or such) to toggle a relay to a load and count how long it takes for the voltage go from A to B.
 

Generic

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You can test cells at 4 Amps Discharge on the Opus. Take 3 dummy cells (CID cells are great for this), put electrical tape on the terminals of the cells, and then use a busbar or nickel strip on the top terminal (positive) of the Opus along with the cell you are testing. The Opus will think it is 4 cells and do a 1 Amp discharge on each slot. Somehow, they are all isolated. If you get 500mAh per slot, that means the battery capacity is 2,000 mAh @ 4 Amps. Credit to OffGridInTheCity for this one!
 

gauss163

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Jun 28, 2020
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At some point it makes sense to consider getting a real electronic load. For about $25 you can get a great quality 150W 60v/10A load that can handle muchmore than any multifunction charger. Doing many discharges usually greatly shortens the life of chargers (e.g. a common problem even on higher-endJunsi iChargers), not to mention common design problems (e.g. early versions of the Opus BT-C3100 had power supplies and fans too weakto handle the full 15W).

It's a good deal at $25.I have two units so I can vouch thatthe quoted specs are accurate andthe factory calibration is spot-on(it can be user calibrated too, but mine have remained very accurate over the past few years after heavy use).

According to recentreviews thelatest version also does internalresistancetests, but I don't have it so I can't comment on that. They also added an (undocumented) computer interface, which has been reverse engineered - see here for the serial port commands - which allows complete control.

You can get an idea of the features and UI from this YouTube review of a clone(and there you can see how similar the fakes look as well as their many shortcomings).

Beware that there are many extremely poor quality clones of the linked 150W load so it is risky buying from other places (the linked Aliexpress seller "Good idea store" has a long history of selling only genuine units, as you can see from the many rave reviews there).

image_rpxhdl.jpg
 

gauss163

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^^^ Update: the PC serial communication protocol for the above load has been reverse engineered - see the link above.
 

gauss163

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Yes, the discharge stop voltage ("sv") featureworks perfectly and - crucially -the load supports 4-wire measurement (unlike the DL24 you lamented in another thread here), so it stops at the actual battery voltage measured through the dedicated voltage sense wires, not the end-of-load-wire voltage (with 2-wires). I've used it manytimes without issue.

For example, here's a test I did just now using 4-wire hookup. I discharged a NiMH cell at 1A with 1.20V stop voltage and my DMM claimsit stopped at1.2013V (= min battery voltage measured by DMM in min/max mode, 5 measurements/sec). As I said, the factory calibration is greaton these units - a pleasant surprise at a $25 price point.
 
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