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Proper load for zb2l3 module
#1
Hi Guys
I'm going to receive 15 zb2l3 modules with two 7,5 ohm 5w resistors. What is the proper load for this module to get 1.0A discharge rate?
I guess 2 R in parallel to get 3,75 ohm? Am I correct?
Thanx
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#2
U=I*R

You have voltage of 3.7 and want I to be 1. => 3.7/1 = 3.7Ohm So yes you need to parallel those to so you will get the 1A load.
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#3
Thank you so much
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#4
Check them as the ones I got were above rated Ohms by quite a bit. I ended up changing them out for 2x 7 Ohm measured and i get 1.1A at 4.2 down to .9 at the end
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#5
I have to agree with jdeadman: check the resistors for their values. Mine have ranged from 7.1 - 7.9 ohms. If you have a bunch of mixed values, try to match them up so that each Zb2l3 has basically the same load.

It is also good to calibrate the ZB2L3's before you start using them. They can give fairly different voltage readings straight from factory.
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#6
Hi guys I built 10 discharge modules and I was very happy by them, especially the test speed, but after checking the same cells with my Foxnovo (to check the accuracy) I found zb2l3 are missing an average of 150mAh and in some cases 350mAh. So I had to recharge and restart the slow test with Foxnovo. I checked the Resistors and they are quite accurate to 3.7-3.75. The Voltmeter seems legit and all fine, but the weird thing is that the results lack consistency. I start all tests with full voltage 4.21 4.22. Should I start a calibration? That looks complicated. All modules behavior are the same and all readings are the same. Should I drop and keep going with foxnovo (and next week with opus) or these modules need just tuning and then they are accurate?
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#7
It's not about tuning. They don't do a CC discharge, current will change together with the dropping voltage while discharging. No matter what you do, you should stick to one method and one device to get consistent results. Ideally it should be a device that does CC, like the Opus. And the Foxnovo possibly as well, don't know. But don't use them both, use either and stick with it.
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#8
As DarkRaven said they just test differently. Stick to one and use that as the number you want.


There is really no cheap unit like those that fully get accurate numbers in my world. You get what you pay for Tongue
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#9
DAmn it! Well they are cheap individually but to get those I had to buy 15 and with shipping and customs more than 100€ in total. I'm still waiting the 2 opus. Live and learn.
Thanx Guys
G
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#10
And your mAh ratings are just base lines. If they are consistently 150mAh off, then I think that's pretty darned good. Unless you mean 150mAh off from each other, then not so good.
If it's the former, that means that the cell is just being discharged under a different curve, as mentioned my DarkRaven, by not being a CC discharge. Personally I think this is ok as you aren't going to be constantly discharging your packs at the same amperage draw until they are flat line anyways. So the non-CC may be closer to a real world discharge.
However, it does not show a worse case scenario, which CC discharge does show. So take that to mind as well.

If the zb chargers are staying consistent, and they work as expected, use them as a guideline just like using the opus as guideline. We know the opus isn't 100% accurate and is actually slightly generous in its readings. So if the zb charger is lower than the Opus, maybe it's closer to the actual mAh rating. But still, this is a baseline. I would always round down when taking measurements to get safer readings.
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