I’ve been re-reading HKJ’s article on Measurements , specifically, checking battery voltage under load. For alkaline cells, he adds a resistor to simulate load condition. I get that. But for Li-Ion he specifically states:
Why is that? Is it considered unsafe to measure Li-Ion cell voltage under load presented by a resistor? I guess you would need a fairly high current to see voltage dip on a Li-Ion cell? Is it just not necessary to check voltage under load for Li-Ion cells?
He’s saying if you want to estimate remaining capacity, then you have to check the lithium-ion resting voltage. A voltage under load won’t give you much information about capacity.
While we are talking lithium-ion , is it alright to fast charge 18650 at 3 amps ?
WalkIntoTheLight is correct. However, measuring the voltage of a LiIon under load can be useful. You can tell something about remaining capacity if the cell is near no capacity remaining. The voltage will begin to drop off very quickly down to 3V and below. If you see this, then you should remove the load and charge the battery back up again. If the voltage drops much below 3V, (below 2.8 maybe, 2.5 definitely) then it would be wise to understand more about the specific battery chemistry being tested prior to recharging the battery. Discharging a LiIon battery to too low a voltage can be dangerous.
That is because the remaining capacity tables are based on no-load measurements.
It would be a lot more work to make a table based on a specific load for a specific cell chemistry and wear of the cell.
Yes, most modern cells (INR, IMR chemistries) should be able to handle a charging current of around 1C.
Though, before doing anything you should try looking at the manufacturer’s specifications.
Thank you .
Thanks all!
Well, okay, but given nothing other than a “lithium-ion” battery description, I think HKJ is correct in saying measure it at rest. It won’t give you a perfect measure of capacity, but it will be better than trying to guess what the discharge curve looks like under a specific load.
Besides, if you’re going to go to all the trouble of measuring it under load, and having to know all the variables involved, you may as well just do a discharge test and measure its capacity with 100% accuracy.
But then why measure alkalines under load? How is that more useful if we don’t know their discharge curves either?
But he does do discharge curves under loads.
Those are (i.m.o.) the most useful of the graphs
(or am i missing something?)
It is not only me that is doing that, but just about everyone in the world.
For some batteries it is easier to get an estimate of remaining capacity when they are measured under load.
Yes, that’s a good point. I don’t know the answer as to why he uses a load-method for alkalines.
IMO, you can easily tell if an alkaline has full capacity: it measures 1.6 volts. Empty, it measures 1.0v or less. In-between is tougher, but most devices use a linear approximation between those values. It might not be highly accurate, but it seems good-enough for most purposes.
Well, it’s probably most accurate in low-drain applications. Maybe it doesn’t scale well to higher-drain applications like flashlights.
Yeah, I don’t know why he’d use a load for alkalines and not for lithium-ion, or vici-versa.
The majority of manufacturer that make battery testers may know something about the chemistry.
If you have a “logical (scientific) explanation” then post it, instead of hunting me.
If you believe you know something, why not post it, instead of you silly antics.
Since you do not post the answers, it must be you that do not know why (If you know why it is “silly antics” from you).
What is up HKJ?
It’s quite unfortunate that gauss163 does not contribute to this topic. It really does look like he just wants to attack you.
Scientists do not attack pseudo science.
Scientists conduct science (so why aren’t you sharing your thoughts about this topic?)
HKJ is not a pseudo scientist because he does not answer your questions.
Following protocols is part of science. Following protocols is not the same as “simply blindly following” something.
While no-load voltage is needed to estimate the remaining capacity, voltage under load would still be useful information, as it relates to the battery’s performance under load. Voltage sag is often talked about when comparing similar batteries, and lower voltage sag is one of the reasons people prefer the Sony VTC6 over the Samsung 30Q, and the 30Q over the LG HG2. But people always talk about it in a general sense, without much in the way of data to back it up.
I have no idea how you would collect or display the data, but hard information about the voltage under, say, 5, 10, 15, and 20A loads would be useful for comparing similar batteries, particularly high drain batteries intended for demanding applications.
HKJ already does all that in his reviews.