[Review] Folomov A4 Charger

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Virisenox_'s picture
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Location: Central Indiana
[Review] Folomov A4 Charger

Folomov A4

MSRP: $35 - $40

Manufacturer page: http://www.folomov.com/en/content/?125.html

Store link: https://www.amazon.com/Folomov-A4-Charger-Charging-Current/dp/B07BQC3KKH

I was sent this charger to review free of charge but, as always, I've tried to be as unbiased as possible.


The Folomov A4 is a very fast 4 bay charger. It's capable of charging four cells at 2A each simultaneously. It can charge Li-ion, LiFePO4, NIMH, and NiCad cells. Besides overcharging Li-ion cells by 0.04V, it's great!

Album link: https://imgur.com/a/N0Jbk6G


The Folomov A4 comes in a black and orange cardboard box. A photo of the charger is on the front, and detailed info about the charger is on the back. This box is good enough to be put on a shelf.


The box contains:

  • A Folomov A4 charger
  • An adapter
  • A cable for the adapter
  • A manual





The Folomov A4 is a 4 bay charger with pretty typical construction. It's made of black ABS plastic and has 4 bays consisting of fixed positive contacts and sliders for the negative contacts. The sliders were a bit sticky on mine. They weren't bad, but they were pretty hard to move compared to the sliders on my XTAR chargers. A bit of lube on rails fixed that.


A common problem that I've run into with chargers like this that can charge any battery size is that sometimes they won't reliably make contact with AAAs or flat top cells. The A4 doesn't seem to have that problem.
There are fins on the sides of the charger by the screen. These look like heat fins, but I'm not sure how well they'd actually dissapate heat. Folomov chose a barrel plug as the connection type for the power cable. That's a good decision. In my experience barrel plugs make good connections, and they're robust. Not to mention that this lets Folomov use whatever voltage and current they want rather than having to use a 5V USB connection. The screen is a backlit LCD, with a black background and white images. This makes the information easy to read without putting out a blinding amount of light when in a dark room.


On the bottom of the charger, there's a table of recommended charging currents and a list of supported sizes and chemistries. The charging current table isn't quite correct, as discussed in the performance section, but the other information is correct, barring one typo. It says that the A4 can charge "163401735517500" cells (bonus points to anyone who can tell me what that cell would look like). I think that was supposed to say "16340 17355 (I don't think that's a real size) 17500".


Inside the charger, there are two main PCBs: the one for the screen, and the one for the charging.

There are 4 sections on this PCB that all have the same components, and a bit in the middle with a bunch of resistors, capacitors, and an IC.

I'm not HKJ, so I can't really tell you what's going on electrically. I also don't have a digital microscope, or a camera that's good at macro photography, so you can't really make out the chips. But I do have a great pair of eyes, so I've written down all of numbers on all of the important looking components. Here are the important looking bits:

  • nuvoTon N77E003AT20: A microcontroller. The brain of the charger, as I understand it.
  • U34 GP 731: I can't find *any* info on this one.
  • DTU 15P03 DH25: I was only able to find one page on this. I'm not sure if it's relevant, or what it says. If anyone can read Chinese, go for it. This is "a CC/CV buck converter for the microcontroller, stepping down 36V to lower voltages from 3V to 5V." Thanks /u/BlueSwordM!
  • DTM9926: This is a dual channel MOSFET.

If anyone needs more info values or model numbers let me know.


When you first put a cell in that slot's screen flashes. During this time you can single press that slot's button to change the charge current. If it's a LiFePO4 cell, you'll need to press and hold the button until you see the LiFePO4 indicator turn on. While the cells are charging, the voltage is displayed by default. Single pressing the button shows the charging current, and double pressing lets you adjust the charge current and chemistry settings, like when the screen flashes when you first put a cell in.


When the cell is done charging, that slot says 100%, and the charging indicator stops moving.

This UI is great. It's not difficult to understand, and the screen shows everything that's going on. The only improvement I can think of is to format the manual better. The thing's a nightmare to read.



The A4 can charge cells at a maximum of 8A total, but only with two configurations. You can do 3A on the sides and 2A in one of the center slots, or 2A on all slots. If there is a cell in all 4 slots, the max current for any slot is limited to 2A. Because this has 4 electrically separate slots, you can charge multiple chemistries at once.

The A4 performs pretty well. It's very fast, obviously, and it's pretty versatile. It can handle cells up to 71mm long. The ability to charge 4 cells at high currents is fantastic. Mine overcharges li-ion cells a little bit to 4.24V (which is within the 1% tolerance mentioned on the back). Someone can correct me if I'm wrong, but I don't think this does any significant damage to the cells. The termination voltage for NiMH cells is 1.45V.
On the bottom of the charger, there's a little table that tells you at what currents you should charge things. It's not quite right. It doesn't factor in what sort of cell you're charging, or how high drain the cells are. For instance, it says that you're fine charging a 3000mAh cell at 3A. This is probably fine for Sony VTC6s, but not for Panasonic NCR18650Bs. I'd just ignore the chart.
Charging fast is great, but I also love how that A4 is capable of charging cells slowly too. The 250mA setting is great for 10440s.

Power Source

The Folomov is a fast 4 bay charger, so USB isn't enough. It gets its power from an adapter that plugs into mains and puts out 12V at a maximum of 8A.

Abuse Testing

The manual says the A4 has reverse polarity protection, as it should, but I decided to test a couple other things as well. First I tested the RPP. It worked fine on all four ports, displaying "Er" when the cell was in backwards. Next I tested shorting the contacts out. This also displayed "Er". Putting too much voltage (6V in this case) across the contacts didn't do anything, not even display an "Er".

Edit: It's been brought to my attention that putting two CR123As in a charger in series was stupid and dangerous. To that I say, 'yeah probably'.

Bottom line:


  • Relatively cheap
  • Very fast
  • Lots of charge current options
  • Protection against user error


  • Overcharges li-ion cells ever so slightly
  • Inaccurate chart on the bottom
  • Sliders need lubed


Thanks for reading my review! If you have any questions about this charger, I'd be more than happy to answer them.

Reviewer for ThorFire, Olight, Sofirn, and Folomov.

Edited by: Virisenox_ on 05/30/2018 - 02:51
Last seen: 14 hours 42 min ago
Joined: 10/10/2012 - 15:55
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Location: Ohio

Thanks for the review. Did you happen to run any tests charging cells at 3A? Just curious as to how warm they got and how long it took to fully charge.

Virisenox_'s picture
Last seen: 1 day 14 hours ago
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I did not, but I can. I’ll test a VTC6. Give me a few hours.

Reviewer for ThorFire, Olight, Sofirn, and Folomov.

Pete7874's picture
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Location: USA

Mine overcharges li-ion cells a little bit to 4.24V
Is this value reported by the charger or measured with a DMM after you’ve removed the cell from the charger?
Virisenox_'s picture
Last seen: 1 day 14 hours ago
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DMM once off the charger. The actual final voltage depends on the charging current. The VTC6 I just tested at 3A ended up at 4.22V.

Reviewer for ThorFire, Olight, Sofirn, and Folomov.

Virisenox_'s picture
Last seen: 1 day 14 hours ago
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Location: Central Indiana
WillyD wrote:
Thanks for the review. Did you happen to run any tests charging cells at 3A? Just curious as to how warm they got and how long it took to fully charge.

I charged a Sony VTC6 at 3A. It took an a hour and ten minutes, it got up to 107 degrees F, and the end voltage was 4.22V.

Reviewer for ThorFire, Olight, Sofirn, and Folomov.

Last seen: 4 days 20 hours ago
Joined: 09/04/2012 - 16:03
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Location: NorCal

Makes me want to get this for my BLF Q8 batteries (3000 mAh samsung 30Q’s )… it took all night (11:30 pm to 6 am) charging newly purchased cells that were about 3.65 volts out of the shipping bag on a Nitecore D4 (375 mA per channel when all four were in). The first hour and a half (10-11:30pm), the cells didn’t even charge and the charger and cells were hot… I pulled them out and reinserted them and ran a fan to keep them cool.
So yes it took a while… Time to break out the wallet for this fast charger…

If I can get it for less than $30 I’ll get one to replace the D4 as my primary charger (D4 will be for charging extra batteries)…

I’ve got a thrower, a flooder, and an EDC too. Still looking for a bigger thrower, flooder, and a new EDC, give or take a few. I’m a flashaholic.

wolfdog1226's picture
Last seen: 4 days 13 hours ago
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Location: Acquasanta,Italia/ Valley Forge, Pa. USA

Thanks for the review!

I just got it a few hours ago. It is Worth the $25 I paid for it. I still love my Fenix ARE-C2[I have 3 of them] but they are outdated a bit. Will always love my Opus BT-C3100 2.2.

I charged a few batteries @ 3A

Battery: Orbtronic 26650 5750mAh[Brand new]
Starting Vol..=3.62V
Finishing Vol.=4.21V
Time=1h 24m

Battery: VTC6[2 Years old]
Starting Vol.=3.58V
Finishing Vol.=4.17V

The end voltages were w/ my DMM which pretty much lines up w/ the chargers voltages.

I am estimating the charging is ~ twice as fast as the Opus charges at 2V

Now we will see how durable it is. Two of my Fenix ARE-C2 chargers are almost 4.5 years old. Thumbs Up

Early in the game for Mr. Folomov,,,,,,,,,but I like it so far

You mentioned the sliders were stiff . Mine are perfect. Just about every charger I have had , I needed to put some lubricant on them. Mine do not need it.

I LIKE the fact that it gives the batteries a FULL charge,,,my Fenix chargers certainly do that w/ voltages of 4.22/23/24 very common.

The VTC6 only charged to 4.17V. I expected that as most chargers will not charge older batteries to 4.20V.

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