Review of / Measurement on 4Sevens Single Bay Charger V2

[HKJ]

[size=+3]Charger 4Sevens Single Bay V2[/size]

This charger was introduced in 2011 together with a new battery from 4Sevens, but due to a problem with the V1, it was recalled and later this V2 introduced. The charger has one bay and can only charge a single cell at a time, because the charge rate and voltage can be adjusted it can charge a large selection of different sizes cells.

I have listed the differences between the recalled charger and the new charger

The charger arrives in a white unmarked card board box.

Here the two switches can be seen. The voltage switch is used to select the correct charge voltage depending on chemistry, the current switch is used to select current, depending on cell size/capacity. The switches has a very short travel.
The charger has connectors for 12 volt DC and for USB power.

The charger is supplied with leads for 3 different power sources. The mains power supply is universal voltage (100-240 VAC, 50/60 Hz). The car adapter needs a socket with 21 to 24 mm diameter. Using the usb power adapter the charger cannot charge at 1 ampere, but at a lower rate.
The led is red when charging, both with 160 mA and 0.5A/1A and green at all other times.

The charger can handle 70 mm long batteries, and both button and flat top cells. Due to the design of the slider it is possible to place a battery in the charger without it getting a connection, this is not a real problem, just check the led changes to red, if not move the battery a bit.


[size=+2]Measurements[/size]

At low voltages the charger will try a short pulse each second, this will reset any tripped protection.
Between 1.0 volt and 3.0 volt it charges with 170 mA.
Between 3.0 volt and 3.6/4.2 volt the charger is applying regular charge current with constant current (either 500 mA or 1 A), when 3.6/4.2 volt is reached it uses a constant voltage charge.
The charger stops when the current has dropped to about 160mA.
When the battery goes above 3.6/4.2 volt or the charge stops the current is turned off (discharges with up to 35 uA current).
The charger will restart if the battery voltage goes below 3.45/4.11 volt, the power has been interrupted or the battery is replaced.
When charger is disconnected from power, but with a battery in, it will draw below 35 uA from the battery.

Charging a 2000mAh cell with 0.5A takes about 4 hours, first 3 hour with constant current and then 1 hour with constant voltage. The high termination current makes the CV part faster.

Increasing the current to 1A reduces the charge time to a bit below 3 hours. The CC phase is faster. Here it can also be seen that the CC/CV regulation is done by a microprocessor and not with a analog chip. The steps is the processor adjusting, analog would have been smooth.

My old IMR cell is fast to charge on the 1A setting, but is not filled completely due to the high termination current.

Here I am using USB power to charge a cell, the current switch is in the 1A position. The charger starts with a charging current of 700mA and uses a little bit more from USB. After 10 to 15 minutes the current is down to 500mA. If I had uses the 0.5A ampere setting, the current would have started at 500mA.

The 4Sevens 26650 battery takes about 5 hour to charge.

When charging a LiFePO4 cell with 3.6 volt termination voltage the charger also does a very fine CC/CV profile. It starts slowly, until the battery is raised to 3 volt, then it goes to full charge current. BUT it cannot handle the termination, it will terminate at 3.6 volt, but because LiFePO4 cell drops in voltage when charging is stopped, the charger will restart charging again.

The pulses that will reset a protection circuit, measured without a battery in the charger. These pulses are limited to a peek current of around 180 mA.



[size=+2]Conclusion[/size]

This charger follows a CC/CV charging profile and also supports long 18650 cells and a lot of other cell types. This makes this charger a good charger, with only a few small detail, that could have been better. The high termination current does spoil it for cells with smaller capacity and LiFePo4 cells must be removed when they are charged.
For cells with more than 2000mAh capacity it is a very good charger, for cells with smaller capacity the high termination current will cost a few % in charged capacity, but give the cells a longer lifetime.


[size=+3]Notes[/size]

Here is an explanation on how I did the above charge curves: How do I test a charger

Some of the photos are from the V1 review, because I got the replacement charger without accessories.

 

[45/70]

I read through the entire review quickly. I think most people could live with the minor problems you mention. With the exception of the LiFePO4 "recharging" problem, I'd say it looks pretty good to me.:thumbsup:

EDIT: Almost forgot! Another fine job HKJ, nice work!

Dave

 

[jasonck08]

Nice job! Looks like a pretty decent charger, probably #2 behind the Pila.

It would have been nice to see the termination current be about 10% of the start current, as recommended by most Li-ion cell companies.

Also the graphs done using USB power look goofy and not really CC/CV.

 

[HKJ]

It would have been nice to see the termination current be about 10% of the start current, as recommended by most Li-ion cell companies.

I would say 2% to 5% of rated cell capacity.

Also the graphs done using USB power look goofy and not really CC/CV.

That is correct, but the curve is within the CC/CV envelope, i.e. it is slower than possible, but does not go outside any recommendation.

 

[45/70]

......Also the graphs done using USB power look goofy and not really CC/CV.

That is correct, but the curve is within the CC/CV envelope, i.e. it is slower than possible, but does not go outside any recommendation.

I was assuming that this was because the cell was nearly fully charged to start with. If so, this would likely represent part, or all, of the CV stage, only.:shrug:

Dave

 

[HKJ]

I was assuming that this was because the cell was nearly fully charged to start with. If so, this would likely represent part, or all, of the CV stage, only.:shrug:

Look at the mAh scale, I do fill in just about the same amount of mAh as in the other curves. You can also see the V scale, I start below 3.6 volt.
The reason for this curve is probably because the current generator needs a bit more than 5 volt to generate full current up to 4.2 volt.

 

[sirimaxi]

Great review!!! Thanks!

 

[45/70]

Look at the mAh scale, I do fill in just about the same amount of mAh as in the other curves. You can also see the V scale, I start below 3.6 volt.

Ah yes, of course. That's what I get for commenting without looking at the graph again. For some reason, the first time I skimmed through your review, the numbers at the bottom (time) for that particular set, stuck in my head as mAh, perhaps because my CBA II is setup that way. Of course, it may actually be that it is my head, that is the problem. At any rate, I was multitasking at the time, so I'll just use that as my excuse.

Dave

 

[brightnorm]

HJK,

Thank you for this helpful and useful review.

Brightnorm

 

[Got Lumens?]

HJK,
Nice review. Thank You.

I have a question, were any comparisons of the two versions done using the same battery?
I have a 18650 that comes off Version1 charger at 4.19V. When charged using the Version2 it comes off the charger at 4.14V.
I have done two charging cycles from 3.8V-Full charge on each. Does anyone else have a simular experience?
Thanks
GL

 

[HKJ]

I have a question, were any comparisons of the two versions done using the same battery?
I have a 18650 that comes off Version1 charger at 4.19V. When charged using the Version2 it comes off the charger at 4.14V.
I have done two charging cycles from 3.8V-Full charge on each. Does anyone else have a simular experience?

The AW18650-22 and the AW16340-IMR are the same cells in both tests (These cells are a bit old).
It is no surprise that the final voltage is a bit lower, this is because the V2 stops charging at a higher current.

 

[StillRC]

Just curious - if any one else has noticed the charge time for an 18650 in the V2 charger is any longer in USB mode. I was surprised, it seemed to take allot longer than my V1. I didn't do any state of charge, it just took over a day and a half, the 1st time I used the (v1 charger) it took 5 hrs, in USB mode again.

 

[JA(me)S]

It is time to replace my Wf-139. The new charger will be used to charge protected 18650s almost exclusively (AW & Redilast 2900). If cost isn't a concern, what is the concensus recommendation between Pila and 4Sevens?

Excellent review HKJ - as usual!

- Jas.

 

[purduephotog]

Sigh, so even my hopes of a well branded single cell LiFePO4 charger are dashed.

Are there *any* alternatives out there that don't rhyme with 'hobby charger' ?

 

[45/70]

Sigh, so even my hopes of a well branded single cell LiFePO4 charger are dashed.

Are there *any* alternatives out there that don't rhyme with 'hobby charger' ?

purdue, LiFePO4 cells are so much more forgiving when it comes to charging, that I wouldn't worry too much about what charger you use. Most of the "crap" chargers out there that have LiFe capability will work, OK.

I've been known to use a WF-138 from time to time myself, for 15266 and 17340 LiFe cells, as it's pretty much "plug and play". The only drawback with it, is that it approximates a "Fast Charge" using a hobby charger, that is, it is similar to stopping the charge at C/5 vs. C/10, when the LED(s) turn solid green. This results in a somewhat less fully charged cell, but other than that it works fine. I do not however, charge LiCo cells with it very often, only in a pinch.

Dave

 

[samgab]

Excellent review, as are all of your reviews HKJ. As a result I've just gone and purchased one of these 4Sevens chargers from their website; and despite saying it was going to be on back order, they dispatched it right away. I think it uses a better charging method (CC/CV) than the stop-gap Cytac I have been using for my 14500's and 18650's and at a better price than the Pila, especially when shipping is factored in to New Zealand for a Pila ($40 for the Pila, $30 for the shipping).
Also, I want to thank you for the info about DMM use in your sig-line. It's very informative. I use my DMM a lot anyway, but there were a few uses explained in there that I hadn't thought of.

 

[pblanch]

Anyone else had the extended time taken to recharge via USB. I intended to use in conjuction with a USB battery pack that recharges at 5.5V (3000mah) as per http://www.voltaicsystems.com/amp.shtml when away from power supply and just to do top up charges with my AW2900. And had gotten the 47s vertion as it could do USB. As I havent recieved the charger yet (has shipped) I am now starting to think will it work, and if it draws a higher that 5.5V initailly will it damage the voltaic battery. Any advice/experiance will be welcome.

Thanks for the great review and update.

 

[JA(me)S]

Instead of asking this question in a review thread, should I have posted the query as a separate thread?

- Jas.

 

[Got Lumens?]

Yes. Proper CandlePower etiquette helps everyone:thumbsup:

Instead of asking this question in a review thread, should I have posted the query as a separate thread?

- Jas.

 

[45/70]

Yes. Proper CandlePower etiquette helps everyone:thumbsup:

Oh, I don't know that there's been any violation of etiquette here. JA(me)S question is, at least in part, about the 4Sevens charger. I suppose it would be up to HKJ to determine.

As Far as his original question,

If cost isn't a concern, what is the concensus recommendation between Pila and 4Sevens?

As I said before, from HKJ's excellent and very detailed (as usual) review, the 4Sevens charger is looking pretty good. That said, it's only been out for a couple weeks or so, and there aren't many people that have them yet.

Also, the Pila has withstood the test of time. I remember when the Yugo was considered as a potential replacement for the VW Beetle, in each and every way, when first introduced. Unfortunately, it failed the test of time. I seriously doubt this will be the case here, but nonetheless, it's a bit early for any long term evaluation.

If I needed a "consumer type, plug and play" Li-Ion charger, I think I would definitely consider this one anyway. The only drawback for me is that it is only a single bay charger, therefore I'd probably be looking at buying two. In this case, for about the same investment, the Pila IBC would appear more attractive to me, due to it's proven track record.

Dave