Got a new charger-Miboxer C4-12, 4 slot X 3A/slot, total 12A output

Today my C4-12 decided to die…

I plugged it in and put two AAA cells to charge and it just went off.
Power supply is good.

Any suggestion what to look for on board?

:cry: . :frowning: … If you can’t revive it, may it RIP. :+1:

Good luck fixing it. :slight_smile:

I hope I will be able to do it.

It only charged batteries 20-30 times before it died…so almost new.

/\ …. :+1:

I just opened it up and I can say I’m lost…I don’t know what to look for.

Looks like it will rest in peace (or pieces).

It died after little use so I’m not sure about buying another, but I need charger like that.

Since you opened it up, I guess you heard back from Miboxer and they said it’s out of warranty?

I bought it over aliexpress, and I think I can’t get warranty.

Or if I can get it but I have to return charger that cost me more than buying new one.

:+1: :+1: :+1: for choices. Always.

If I had choice I would go for something far more simple. No displays with settings. Just one button to set the current and that’s it. Just like the little LiitoKala and Basen chargers.

That brings me to another point. I’ve also bought a simple USB tester that shows me the current draw when charging. I learned something I knew for a long time but never got trough my thick skull.
A 2A (Basen) charger isn’t twice as fast as an 1A (LiitoKala) charger.
Sure 2A goes full throttle when the cell is (nearly) empty, but the more full it gets the lower the current.

I’m not saying that’s bad, or shouldn’t be that way, just that those high currents only matter in the beginning of the charging process. And when the cell isn’t completely empty, you won’t see high currents at all.
I have no way of doing an honest test but as a way to explain using fictive numbers I expect something like this.

3A: 15 minutes at 3A, 15 minutes at 2A, 1 hour at 1A and below. (90 mins)
2A: 45 minutes at 2A, 1 hour at 1A and below. (105 mins)
1A: 2:15 hour at 1A and below. (135 mins)

So 3A isn’t 3x faster than 1A.

Your numbers are way off. Most Liion chargers use 2 main phases. The CC phase which is constant current and the CV phase which is the contact voltage.

The vast majority of time spent charging a battery (let’s say from 3.0 volt) is spent in the CC phase. Maybe 75% of the time.

Once the battery is charged up to around 4.1v or so the charger will shift to the CV phase. The voltage holds at 4.2 and the current starts to ramp down slowly.

The CV phase is always very slow for the amount of power it puts into the battery. This is why you see cell phones say they charge from dead to 80% in one hour. That is the CC phase. It might take another 30 to 40 minutes to get that last 20%.

Lithium tool battery packs usually only charge them up to 4v. This makes them charge faster and the battery life longer.

Same for electronic cars. Tesla only charges their battery packs to roughly 4.0 volt. Definitely not to 4.2v. That just adds charge time and reduces battery life.

You can see these charge cycles by checking out battery charger reviews. Here is a good source.
http://www.lygte-info.dk/info/indexBatteriesAndChargers%20UK.html

In my experience, I weekly tend to run my 26650 cells down to around 3.7 volt. With my old 1A charger I’d be waiting about 5 hours. With a 2A charger it went down to about 3 hours. With a 3A charger it’s usually under 2 hours. So yeah, from 1A to 3A is not exactly 3 times faster, but it saves me over 3 hours of having to sit next to the charger either reading or watching tv, etc… which is huge. I get impatient. I’ll gladly pay more money for a faster charger. Lol

5 to 2 hours is indeed worth the trouble. And I pay extra for more speed too. Don’t get me wrong on that. I even decided to not to buy anything below 2A.
Do you really babysit your cells being charged? If yes, then extra time really counts. I just fill my chargers and leave for the day/night. So often I don’t need extreme speed. But there are times I do and need as much as I can.

What’s most informative in your post is the part about CC and CV.
Say I need to charge 8 cells asap, but I only have one 3A MiBoxer. Then it would be best to charge until about 75% and top the remaining 25% of in one of my slower chargers while the MiBoxer charges the remaining 4 cells at full speed.
Something like that?

You are not supposed to leave charging cells unattended. That’s one of the rules of Liion batteries. The few people I’ve heard that charge unattended put the charger in a metal pan and put it outside or in their garage in case it catches on fire. There have been people whose house have burned down because they left it charging unattended.

Maybe I’m being a bit too precautious, but it’s easy for me to babysit them. It’s usually charge all my main cells once a week. I’ve got the one C4-12 and 2 Xtar SV2 Rocket chargers. So if I need to charge 4 x 26650 at 3A and 4 x 26350 at 1A I can do it all in one setting.

If you need to charge 8 x 18650, your idea from above sounds good and should reduce the overall charge times. Can your particular 18650 take a 3A charge? Not all can. You can look up your particular battery models data sheet to see all its specs.

Here is quick guide Mooch did.

.

I have no clue…
On this forum I’ve read 1C is ok, and 0.8C advisable.
All my 18650 cells are 3500 mAh, so with that in mind I bought 2A and 3A chargers.
My LiitoKala 35A 3500 mAh cells aren’t in the list.

Thanks for the nice overview chart JasonWW! May I correct you i.a.w. the Samsung 29E? This one is specified to 8.2A instead of 2.75A.
Cheers, Thomas

Generally speaking, high capacity cells tend to not have very high discharge or recharge rates. What particular battery models do you have?

All praise goes to Mooch. This is his chart. He and HKJ are great resources for the battery community.

BTW, I have never heard of any 18650 being safe to charge at 8.2A. Are you sure about that? Maybe you are thinking of the output?

Sorry for the confusion JasonWW. Of course, I meant the output and not the charge rate. :wink:

Click

They are claimed to be a “NCR 18650ga” rewarp. 10A discharge.

Sharing the charging of the Lii-402 (charged a fully-discharged Sony VTC4, discharged to around or a bit below 3.0v) and then set 2A charge rate in Lii-402. Using EBD-USB+ meter to graph the charging:

Same graph (one shows charging time and the other shows mAh charged — it is measuring the Lii-402 charger, which may not exactly correspond to the charged capacity of the 18650 battery, but should correlate).

(Lii-402 appears to have a high charge terminating current (around 0.45A) when set to 2A charge rate. Although when I checked the battery voltage right after charging, I got a quite exact 4.20-4.21v.

Hmm, a bit odd Liitokala is rewrapping Panny GA’s. So if we assume it’s accurate we can look up the data sheet for that cell.

I found a more detailed data sheet here.

What is odd is that it doesn’t list a max safe charging rate like other brands. Other brands will list a low charge current rate for max battery life, a standard charge current and a max charge current.

For the Panasonic NCR19650GA it appears the highest they recommend is 1.67A. If we look at the Samsung 35E it shows a similar standard charge rate of 1.7A and a max of 2A. If we look at the LG MJ1 it shows a similar standard charge rate 1.7A, but a max of 3.4A. So it really does depend on the specific model and it’s chemistry.

You might be able to charge those GA’s at 2A and be fine, but 1.5A looks like the safest rate.

Also, I did a bit of digging and it is not known if the Liitokala lii-35A is actually a Panasonic GA. It may be a 35E or even an independent cell that has similar characteristics. Thread is here.

Have you ever discharged them to about 2.8v and then measured the capacity? We’re they close to about 3200-3300mah?

Sorry I have no way to do an accurate test of any sort.

But even if the cells are really Panasonic NCR19650GA the wrapping is wrong because it states 3500 instead of 3350.
And IF the cell is genuine charging at 3A with my MiBoxer isn’t a smart thing to do, because that’s almost double of what’s safest. While I don’t babysit cells all the time, I do sometimes. On a few occasions I touched them and they weren’t hot, not even warm. So that’s a little good news I think.

Anyway, when time is no issue I’ll charge at 1A. And I must say often time is no issue at all. Even less now because I bought 7 more cells. That vastly reduces the need for quick recharge during the day. But the babysitting them remains a problem.
Is it so that charging at 1A reduces the risk of fire? Or is it more an age related problem? I don’t remember which one but when looking for a charger one description stated the charger shuts down after X minutes no matter how far the battery is charged because of safety reasons.