Internal resistance?

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how crazy is this
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Internal resistance?

This experience was interesting to me. Perhaps someone who knows more will shed further light on it.

My Ti3 is always in my pocket and I use it to go to bed without disturbing my SO. The other night it was in what I assume is some sort of “limp mode”. This alone brings up questions that I have about lights, drivers, and batteries. I know that I have seen things like this with other lights. I don’t understand it. At some low power point the light actually will not go into its moonlight mode. It is in a single mode that is brighter than moonlight but lower than low and does not change modes. Why wouldn’t it default to moonlight?

Thought the battery was just near dead so I put it on the charger. Surprised that it only took about 130 mAh or so. Noticed that even fully charged it was showing 999 for internal resistance. This was odd as usually even if they start out that high they will drop to something more reasonable and I even have a few cells that finish <100 that may start at 999 when depleted. Is there a point where the IR is so high that even when much charge is left the light thinks that it is near depleted? This appears to be what happened.

The next part is really odd to me. I put the fully charged battery back in the Ti3 and it cycled through the modes fine so I put it in the mid mode and left it figuring that it needed to be fully depleted and hope that the IR will drop after a full discharge recharge cycle or two. Left it there for 10 hrs or so — certainly way more used than before when it went into “limp mode” yet it was cycling modes just fine. Clearly the battery was able to deliver a significant amount of energy and this time working normally. What changed?

Left it run until the light went out and it is on the charger now. Looks like it will end up close to the 900 mAh capacity it should be but the IR is still hight. This time it is dropping but sure it will end up being way more than any of the other cells from that pack.

I have some AA Japan Amazon basics that have IR over 250 or so that put out stated capacity on lower modes but won’t hold up under max. Great batteries for having a lot of energy but not so great to get a lot of lumens.

Is there anything a person can do to lower IR?

pepinfaxera
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how crazy is this wrote:
Is there anything a person can do to lower IR?

Oh yes! Read (check) the IR with an IR meter.

Do not measure IR with a charger.

The IR data given by a charger is only indicative and in some cases with a lot of error.

Sorry for my bad English
(google translator) , (https://www.deepl.com/translator)

Barkuti
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Geez!

 

First of all numbers are just numbers, they mean nothing without units of measurement.

Then, there's no single analyzing charger in the market which does a proper job in determining cell or battery internal resistance (some people may say the Opus BT-C3100 bla bla bla, but still it is wrong). Batteries/cells in good condition behave like practical voltage sources and have very low internal resistances. To measure the internal resistance of a cell, voltage variations need to be measured or sensed right at the cell terminals with a varying regulated current load. Analyzing chargers do this in some way. However, they do not sense or measure voltage variations at the battery or cell terminals, but somewhere in the circuit board at the leg of some integrated circuit. Between this and any battery terminals there are circuit board tracks, the cell rail and the very contacts between the cell and the rail. Compared to the internal resistance of a healthy cell the resistance of its rail and contacts is huge and unsteady.

Some analyzing chargers measure internal resistance pumping some short pulse current into the cells; because this raises cell voltage and cell voltage cannot go above maximum charge voltage, when cell voltages are high or close to fully charged the internal resistance measurements will be even more bogus than normal, completely failing with super low values with fully charged cells.

You also didn't say which charger you are speaking of, this is important because we could address it better by taking a look at some proper review (like at lygte-info.dk).

Enough for now. 

Fri, 06/26/2020 - 03:27

The Light Innocent I am

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Zappaman
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As much as I agree with Barkuti here on ALL points he is making, I will say that testing different cells in any said charger CAN at LEAST give you a “delta” to compare several different cells by. I KNOW my Q30 authentic cells have very LOW IR. And when I put them in my ZanFlare C4 charger they will read somewhere between 10-30 IR. Accurate… no.

But… then I’ll take some run of the mill stuff out there like the Sofirn 18650 3000mAh batteries (I end up with buying “kit” deals” and such) and they will register between 30-60 IR. So there is a “general” idea that can be inferred from our basic chargers even though they can’t give a “spot-on” reading.

I have some super el-cheapo (pure garbage) 18650s from a few years back that came with an outdoor LED light for my garage. Immediately pulled them and replaced with decent cells on hand— but I remember TRYING to charge them (they wouldn’t get to 4.2V… even overnight). But after about six (re)inserts into the charger— they NEVER measured UNDER 350 IR! And in some cases they measure in the 500-600 range.

As they say… you mileage may vary. Blushing

ZappaMan

NeutralFan
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I don’t think there is a way to improve the IR with batteries. Maybe with NiCad batteries of the past, you could discharge and charge them numerous times to remove the memory effect, but I’m not sure that lowered the IR.

It seems with NiMH and Li-ion batteries thankfully, age is the determining factor for when they go bad (ie. high IR) unless they’ve been used excessively or abused.

I’d rather use my flashlight around the house than turn on the lights.

how crazy is this
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I have had a couple of NiMH batteries that seemed to come back somewhat from high IR. Certainly I don’t trust my charger to give accurate numbers whatever they may be. My Miboxer C4 does seem to be pretty good at adapting the charge rate according to what the battery can handle. Batteries with higher IR charge slower. Does not warm the battery and the final charge value appears rather accurate to me based on run time tests. The percent charge when you put the batteries in is a joke but termination has been solid.

I’m not sure that I would consider all of my high IR batteries junk though — at least not with the NiMh. Now I might consider them junk in that they certainly won’t deliver max lumens. However, when they discharge the stated capacity, at a moderate discharge rate at least, they aren’t exactly junk batteries. I have some older enleoops that have both high IR and lower capacity. That seems normal age to me. Not sure what to make of the cells that have high IR and high capacity.

Have some junk Lion cells that have low IR and put out great light but the capacity is only about 25% of what they should be. I consider those junk.

What I would really like to understand is just how the high IR cells throw off the drivers so bad. Is that voltage sag?

Barkuti
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how crazy is this wrote:
… Not sure what to make of the cells that have high IR and high capacity.

Cells with high internal resistance still are able to hold a load, if only a smaller load. To accurately know how much load they can hold it is very useful to have a battery tester with discharge curve plotting software. ZKE Tech has some (with PC software), their EBD-M05 is nice for the price. A 4-wire battery holder is also required (like one of these from ZKE too). The EBD-M05 can be calibrated and is super consistent giving out internal resistance readings, and although in my experience I also wouldn't take these as gospel, they can be easily corrected multiplying them by a constant.

In my experience, one of the most accurate methods to calculate DC internal resistance of batteries is substracting the voltage delta between two discharge curves, and dividing it by their current ratio delta. Discharge curves of the same cell at different rates match perfectly, however since the performance of a battery increases with temperature (which raises as the discarge progresses, and raises quickly with higher discharge rates) I advice you to use voltage values just a bit after the discharge curve has started (after the initial sharp voltage drop passes).

However cells with perceptibly high internal resistance may be worn-down for some reason, and a waste of time in the long run.

how crazy is this wrote:

Have some junk Lion cells that have low IR and put out great light but the capacity is only about 25% of what they should be. I consider those junk.

What is the brand name in the wraps of these? They could be good low capacity cells which have been spuriously rewrapped by some unscrupulous company.

how crazy is this wrote:

What I would really like to understand is just how the high IR cells throw off the drivers so bad. Is that voltage sag?

Yes.

The Light Innocent I am

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