Just received a free charger I was asked to review as part of a promotion. I’m 100% NOT charger savvy!
With that said…
It’s a dual slot smart charger from an unknown brand.
I placed a 16340 in one slot, manually set the charging current for the lowest setting 0.5A, and let it charge. I started getting nervous that at around 98-99% the voltage displayed was 4.24 volts, but I wanted to see when it would terminate the charge so I let it go.
After removing the 16340 and placing it aside, I then followed up by placing a 21700 in the charger, forgetting I had it set to manual 0.5A charging current, but I left it anyway, as what could it hurt…
At 98 to 99% the voltage was showing 4.24, and sometimes bouncing to 4.25V. It finally shut off after about 2.5 hours (battery was at about 3.7V IIRC at start of charge).
About 30 minutes after the 2nd battery finished, I was able to get out my multimeter and checked the voltage on both batteries. The 16340 read 4.19V and the 21700 read 4.20V, both which AFAIK are good, and safe.
Should I be worried that while changing, the chargers display is showing 4.24 - 4.25V before termination? Is this normal? Is this dangerous? Is it possibly just a wonky voltage sensor in the charger? My multimeter, which I know to be accurate tells me the charge on the batteries (after sitting for a bit, if that makes any difference) is safe.
Any thoughts on what I’m seeing?
Specs on Li-ion cells usually state charge termination 4.2V +/-0.05.
Theoretically, cell longevity will be better if charged to 4.195V Vs 4.25V.
Chargers are not precision calibrated instruments, could be either (or both) the charging chip or the display.
You can (carefully) measure voltage while charging by inserting paperclips (or strips of aluminium can with the coating removed), between the cell and the terminal and clipping the multimeter leads to these “adaptors”. If you’ve a DMM with long needle-like probe, you might be able to just measure the voltage directly.
Once charged and removed from a charger, cells will typically “relax” in voltage a little. Resting voltage over time is a useful measurement to give an indication of cell health, but not for testing a charger.
Just wanna jump on the bandwagon here.Definitely check the final voltage of your charger. It seems high. As previously stated a slightly lower final charging voltage can help preserve the lifespan of your batteries. also, charging at a lower current Will help the lifespan. I almost always charge my Liions at 1/2 amp.
Is it this one? It says D2 upper right above the screen.
I got this almost a month ago from Amazon for about $11. You can find them from a few different sellers with different names but none of them have names on them other than that D2. Some sellers also sell a D4 four slot. Both are type C.
I haven’t used it a lot but I’ve been doing some voltage testing. The screen reads a little higher than the actual voltage going into the battery and the terminals on the charger read slightly higher then the voltage on the terminals on the battery. Not quite as much of a difference if you’re on the 0.5 amp setting vs the 1A or 2A setting. The half amp and one amp setting are accurate as far as amperage but I’ve never seen more than 1.5 amps on the two amp setting.
When you first insert the battery OR if you break contact at any point and then reengage the terminals, the screen reading does measure very accurately the battery voltage for about 4 seconds before it starts charging.
So bottom line is the battery is not going above 4.2v on mine. I’ve let a few batteries go to full and the screen was showing probably around 4.25v before terminating but the terminals I don’t believe got above 4.2v. Once it stops charging it continues to show you the battery voltage and it’s very accurate. The few I’ve seen were about 4.16v.
I have to do a little more testing with it but I think it’s pretty good.
Yes PCB might have a difference (though should be very small).
I was questioning whether one could measure a voltage difference between cell terminals and charger contacts - what’s the voltage drop on a thin (assume nickel) plated surface at c.3.7V and 1A?
I suspect the original post was measuring during charging and comparing to the resting cell voltage, but wanted to clarify.
The terminals do appear to be nickel plated or ”mostly" nickel-plated. I looked at things with a good light and a loupe. They scored the positive protrusion before they plated it. I can’t tell for sure but I don’t think they scored it perfectly flat. I don’t think that’s making a major difference.
I went back and got some hard numbers while charging. I cleaned the terminals of the charger and the 18350 button top sofirn battery.
The starting voltage was somewhere around 4.05v. I let it charge for about five or so minutes before testing.
The amperage based on a USB tester was 0.2 amps.
The display was showing 4.20/4.21v.
The terminals on the charger were 4.16v.
The battery terminals were 4.08v.
I believe the differences were greater at one amp when the batteries were down at 3.7v, but I’ll have to go back another day and test that again.
I don’t think this difference between terminals of the charger and terminals on the battery are going to be much different on any other charger.
A longer battery will put more pressure on the terminals but the spring is not really weak so I don’t think that’s a big issue. Maximum battery length is probably about 73 mm. I only have flat top 21700’s.
I’m not promoting it and I’m not done testing but here is the link. I purchased it after stumbling on it.
18650 Battery Charger, 2 Bay Battery Charger with Smart LCD Display Fast Charge for Rechargeable Batteries Li-ion LiFePO4 NI-MH NI-Cd AA AAA C 21700 26650 13650 16340 18350 18700 RCR123 Amazon.com
Yep! Pretty much the identical charger, but mine is Swanlake branded. What I’ve noticed is if I check the voltage of an empty slot, it reads about 5.5 volts. If I use some tin foil between the battery and positive terminal, I still get a reading on the display…If I then put a meter across the tin foil and negative terminal slider, the voltage on the charger display dips a few 10ths, and then slowly goes back up. At charge termination, the battery is always a bit less than what the charger’s display shows
