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resistor 1% or 5%
#1
As the title says, what kind of resistor is best for the zb2l3.
Cous the 1% are...a bit.....more expensive.
Now i don't have a problem to buy those 1% resistors, BUT are the worth?
Its a one time investment, that will do a lot for ya, so what are we talking about, or am i missing the point?

So stick to the 5% or is it better for more accuracy to buy 1% resistors?
Is it worth, does it add something?

Thanks in advance, best

ps i go from 6.8ohm to 5 ish, probably 4.7 ish.
Advice is welcome and very appreciated, before i finish my second (out of 10)1400 cell batch, thanks
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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#2
1%, 5%, 10% that's the variance of the rated resistor.

So if it's rated for 100-Ohm with a 1%, then it could be as low as 99-Ohm or as high as 101-Ohms. If it's the 10%, it could have a range of 95-Ohms to 105-Ohms.

This means, not that the resistor changes over time, but during the manufacturing process there could be that much variance. Just check with an Ohm meter to find out exactly what Ohm reading your resistor has and allow for it, or calibrate your hardware for the change.

Personally, I don't think there's much difference between 1% and 5% when doing a capacity test. The variance won't change the end result that much. 10% I'd be a little more leery about, or if I was using ADC's or making a current monitor. Then the 1% ones are a must.
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#3
I don't think it really matters. However, if you are fussy buy all the resistors you need at the same time from the same place. They will most likely be identical.
100kwh-hunter and Korishan like this post
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#4
(07-10-2019, 05:36 PM)100kwh-hunter Wrote: So stick to the 5% or is it better for more accuracy to buy 1% resistors?
Is it worth, does it add something?
Do you need 1% accuracy?  Then use 1% resistors.  Do you not care?  Then use 5%.
100kwh-hunter likes this post
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#5
(07-11-2019, 02:35 AM)billvon Wrote:
(07-10-2019, 05:36 PM)100kwh-hunter Wrote: So stick to the 5% or is it better for more accuracy to buy 1% resistors?
Is it worth, does it add something?
Do you need 1% accuracy?  Then use 1% resistors.  Do you not care?  Then use 5%.

Personally I think that the ZB2L3 would be more of a source for inaccuracy than the resisitor used. In fact if you really want a proper capacity test, you want to test watt hours, not in amp hours.

In fact given the context, I believe that it would be more important to have resistors that were identical, not necessarily of an exact value.
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#6
It does not matter on the accuracy of the discharge resistors as it has an onboard shunt resistor that it measures the voltage drop that measures the current. I use 3.3ohm for an average of 1a discharge.
Geek likes this post
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#7
(07-11-2019, 07:42 AM)brettwatty Wrote: It does not matter on the accuracy of the discharge resistors as it has an onboard shunt resistor that it measures the voltage drop that measures the current. I use 3.3ohm for an average of 1a discharge.

As per usual - we overlooked the obvious! Well spotted.
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#8
A honest question, probably a stupid one, but what is the obvious?, i think i don't get it.
I spent some time to get those zb in the same order with ten of the same resistors, check them of course.

Its logical that when you buy ten or 40 resistors that they are in one range of deviation.
Within factory limits.
So 5% on those numbers of 3.3 or 5.6 ohm is almost nothing, 1% is nothing, as long as they are all the same.
I get that one, the same is important for a good end result and the same end result.

But Frankly speaking i think i miss a point here, i hope you are willing to explain it to me:

It does not matter on the accuracy of the discharge resistors as it has an onboard shunt resistor that it measures the voltage drop that measures the current. I use 3.3ohm for an average of 1a discharge.

As per usual - we overlooked the obvious! Well spot.

Thanks in advance
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
Reply
#9
(07-13-2019, 06:57 PM)100kwh-hunter Wrote: ...

But Frankly speaking i think i miss a point here, i hope you are willing to explain it to me:

It does not matter on the accuracy of the discharge resistors as it has an onboard shunt resistor that it measures the voltage drop that measures the current. I use 3.3ohm for an average of 1a discharge.

...

That is exactly the case. The ZB measures this discharge current. And counts the amps over time. So unless your discharge currents are vastly different they will give sufficiently accurate readings.
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#10
Generally, even the 10% tolerance one is good, but not in your case.

The ZB tester is a precision instrument, therefore if you want to replace one of it's resistors you will need as good accuracy as possible.

If you're talking about the discharge resistor used for testing, it's actually the same thing, you need precision.
But here you have 2 options:

- relay on the quality / good tolerance of the resistor and do you measurements like that
or
- get any resistor, measure it with a precise instrument and adapt your calculations given it's exact value (add a multiplier to your calculations like .98 or 1.02 depending on the actual value of the resistor)
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