# Review of / Measurement on 4Sevens Single Bay Charger V1



## HKJ (Mar 10, 2011)

[SIZE=+3]Charger 4Sevens Single Bay V1[/SIZE]

[SIZE=+1]This charger has been recalled[/SIZE]

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









This charger was introduced in 2011 together with a new battery from 4Sevens. 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 can be charged.






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 have a very short travel without any click.
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 can not 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 most flat top cells, short batteries (16340/18350) are a bit loose in the charger, more tension on the spring would have been nice.


[SIZE=+2]Measurements[/SIZE]

The charger does not start charging below 2.0 volt, i.e. it cannot turn tripped protection on again.
Between 2.0 volt and 3.0 volt it charges with 160 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 4.2 volt is reached it uses a constant voltage charge.
The charger stops when the current has dropped to about 80mA.
When the battery goes above 3.6/4.2 volt or the charge stops the current is turned off (discharges with below 15 uA current).
The charger will not restart charging before the battery has been removed, the power cycled or the battery voltage goes below 2.5 volt.
When charger is disconnected from power, but with a battery in, it will draw below 20 uA from the battery.






Charging a 2000mAh cell with 0.5A takes about 5 hours, first 2½ hour with constant current and then 2½ hour with constant voltage.






Increasing the current to 1A reduces the charge time to a bit above 3 hours. Both CC and CV 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 0.5A setting. This charge rate uses the same termination current as the 1A setting, but here it is a bit high, especially when charging 16340 cells. The cells will be charged fast, but with a bit lower capacity than possible.






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 5½ 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.



[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 ought to make this charger a very good charger, with only a few small detail, that could have been better. 
*But* that does not include the first series (i.e. all shipped before 2 Marts 2011) of the chargers, they has a problem that can lead to over current. 4Sevens is aware of the problem and will replace them.



[SIZE=+3]Notes[/SIZE]

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

When using the charger on USB I have not see the over current problem.


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## SoCal5150 (Mar 10, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Thank you for the great/informative review HKJ. I have mainly used AA/CR123 for my flashlights. Since I wanted to try the Maelstrom S12, this ended up being my first jump into the rechargable Li-ion realm. I have already purchased some AW 18650/16340/14500 and Readilast 18650 to use with the 4Sevens charger. I bought the S12 first day it was available so I assume it is from the first batch you mentioned that has problems. Is there any thing specific I should be watching out for? I do not have a DMM (I guess I need to get one now) so should I not use this charger until I can get it replaced? Thanks again HKJ!lovecpf


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## HKJ (Mar 10, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



SoCal5150 said:


> I bought the S12 first day it was available so I assume it is from the first batch you mentioned that has problems. Is there any thing specific I should be watching out for? I do not have a DMM (I guess I need to get one now) so should I not use this charger until I can get it replaced?



4Sevens does not have the fixed charger yet, i.e. it is the defect one you have.

The safest way to use the charger is with a usb power supply. I could not trigger the fault when using a usb power supply, but with a 12 volt power supply I could very easily trigger it.
With the supplied power supply the fault gives about 2 ampere charger current, but I do not know if the charger will stop when the cell is full. I have always stopped my tests after 5 to 10 seconds with over current.


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## mrlysle (Mar 10, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Thanks for the info! I think I remember a thread about this charger before the forums went down. It's good to know the charger is better now. I thought about getting one, but I really want a Pila IBC unit. What's your opinion of one versus the other besides the Pila having two bays? I really can't see me having the NEED to be charging two cells at a time but you never know. You think the cost savings over the Pila would be worth buying this unit instead? Thanks again for investing the time to review this charger!


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## HKJ (Mar 10, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



mrlysle said:


> What's your opinion of one versus the other besides the Pila having two bays? I really can't see me having the NEED to be charging two cells at a time but you never know. You think the cost savings over the Pila would be worth buying this unit instead?



I a not tested the Pila, but I like the 4Sevens charger. The two current settings, a bay that can handle many sizes of cell makes and that it follows the recommended charging algorithm makes this look like a good buy. Now I just need to test the new version and see that it really is fixed, without reducing performance in any way (I believe that will be the case).
The next thing that is needed is that many people uses the charger for some time, this is the only way to prove that it is as good as it looks and measures. The Pila has passed this.


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## jonnyfgroove (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



HKJ said:


> 4Sevens is aware of the problem and will replace them.



I guess they are not very concerned as I see zero mention of this on their sub forum in the MP.


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## HKJ (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



jonnyfgroove said:


> I guess they are not very concerned as I see zero mention of this on their sub forum in the MP.


 
I believe that he is very concerned with it, but are waiting on the fixed series, before initiating a replacement.


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## tandem (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Could the over current condition be triggered when charging any capacity cell? On either current setting?


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## HKJ (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



tandem said:


> Could the over current condition be triggered when charging any capacity cell? On either current setting?


 
Yes, what triggers it is a short interruption of the connection to the battery. I have also see it when power on the charger, but only once.

You can see it on this move clip, the charger start by using 0.55 ampere, but a short interruption of the battery connection increases the current to 2 ampere (With the supplied charger the current is limited to around 1 ampere).


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## srfreddy (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Should I be concerned, if I ordered mine on the 22nd? also, isn't 2 amps safe for 18650s?


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## gflite (Mar 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I am waiting on my order too and now concerned about the charger


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## HKJ (Mar 12, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



srfreddy said:


> Should I be concerned, if I ordered mine on the 22nd? also, isn't 2 amps safe for 18650s?



If the charger is shipped, it is one of the faulty ones. 2A might be safe enough for a 18650, but the charger can also do RCR123. I have not checked if the termination works when the charger goes haywire. 
The 2A is only when using the supplied power supply, with the car adapter the current can be higher.



gflite said:


> I am waiting on my order too and now concerned about the charger



As long as it is not shipped yet, I believe you will get a fixed one. If you get one of the early ones, just use it on usb power, until 4Sevens get the fixed ones out.


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## KiwiMark (Mar 12, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I like the idea of this charger - simple but versatile. I kinda wonder though why they didn't suspend sales as soon as they learned of the fault - it seems a bit risky to keep selling a product with a known fault that could be a safety issue.

For many more technically minded people I would tend to recommend the Turnigy Accucell 6 as a better product - it does work out a bit dearer once you add shipping and you do need to have a power supply to run it from mains (some people would already have something suitable, some can modify a PC power supply and some would have to spend another $10 to buy one). Of the 2 I would consider the Accucell to be the safer product - you can see on the display if you have the settings right (and the actual amps & volts). With the 4Sevens charger you would want to be VERY careful with checking the switch positions to be sure you are always on the right settings, mainly with smaller cells that shouldn't be charged at 1A and with LiFePO4 cells that will have their life shortened by charging to 4.2V.

I'd be interested to see the results of testing on the fixed product when available - for a small and easy charger this could be a worthwhile product, especially for people that don't want to be confused by the hundreds of options on a hobby charger.


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## sirimaxi (Mar 12, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I hope new version solves the 2A issue, tighten the spring to better hold the 16340, mark the positive and negative side, 3.6/4.2V and 0.5/1A switches have a longer travel with a click (to let us be sure we are on the setting we want)...with that things solved I think it´s a perfect charger and a very cost effective one....Hope David hear us as always.


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## HKJ (Mar 13, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



sirimaxi said:


> I hope new version solves the 2A issue, tighten the spring to better hold the 16340, mark the positive and negative side, 3.6/4.2V and 0.5/1A switches have a longer travel with a click (to let us be sure we are on the setting we want)...with that things solved I think it´s a perfect charger and a very cost effective one....Hope David hear us as always.


 
I would not expect any physical changes to the charger, this fix had to made fast and would not leave any time to change the design.


4Sevens has posted a official note in the charger thread on cpfmarketplace.


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## KLowD9x (Mar 27, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I almost ordered one of these but then I saw this thread.

Question: the wall charger, what is the amperage rating? If it is one amp, I would feel a lot better about ordering this charger as that should prevent the overcharge issue you have found.


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## srfreddy (Mar 27, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



KLowD9x said:


> I almost ordered one of these but then I saw this thread.
> 
> Question: the wall charger, what is the amperage rating? If it is one amp, I would feel a lot better about ordering this charger as that should prevent the overcharge issue you have found.


 
They are waiting on their fixed ones, whose shipment got delayed.


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## HKJ (Mar 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



KLowD9x said:


> Question: the wall charger, what is the amperage rating? If it is one amp, I would feel a lot better about ordering this charger as that should prevent the overcharge issue you have found.



The wall power supply is 1 A, this limits the cell current to around 2 A. But 4Sevens are working on fixing the problem.


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## HKJ (Mar 31, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Added charger curves for a LiFePO4 18650 and 4Sevens 26650.


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## badtziscool (Apr 5, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



HKJ said:


> Yes, what triggers it is a short interruption of the connection to the battery. I have also see it when power on the charger, but only once.
> 
> You can see it on this move clip, the charger start by using 0.55 ampere, but a short interruption of the battery connection increases the current to 2 ampere (*With the supplied charger the current is limited to around 1 ampere*).


 


HKJ said:


> If the charger is shipped, it is one of the faulty ones. 2A might be safe enough for a 18650, but the charger can also do RCR123. I have not checked if the termination works when the charger goes haywire.
> *The 2A is only when using the supplied power supply, with the car adapter the current can be higher.*
> 
> 
> ...



I'm kind of confused. So the over current charge can happen when using the included AC plug or does it only happen when using the car adapter?


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## HKJ (Apr 6, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



badtziscool said:


> I'm kind of confused. So the over current charge can happen when using the included AC plug or does it only happen when using the car adapter?


 
With either of them, but USB is probably safe.


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## BoarHunter (Apr 6, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



HKJ said:


> With either of them, but USB is probably safe.



Did you open this charger to get an idea of its circuit, identify the components ? No need to draw a detailed circuit diagram but from the main component, one get get a good idea. Does it use a microcontroller or special CC/CV chips ?


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## badtziscool (Apr 6, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



HKJ said:


> With either of them, but USB is probably safe.



So even though the wall adaptor is rated at 1A, it can put out more current than that?


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## HKJ (Apr 6, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



BoarHunter said:


> Did you open this charger to get an idea of its circuit, identify the components ? No need to draw a detailed circuit diagram but from the main component, one get get a good idea. Does it use a microcontroller or special CC/CV chips ?


 
No, there are no visible screws (They are probably under the rubber feets). I am convinced that it uses a microcontroller, both because of the saw tooth in the charge curve, but also because the lockup looks like something a microcontroller would do.



badtziscool said:


> So even though the wall adaptor is rated at 1A, it can put out more current than that?


 
The charger has a buck converter to reduce the 12V to charge current/voltage, this will just about double the current.

I also has a unconfirmed guess that this converter is some of the reason for the lockup. When the battery is disconnected the charge voltage will for a short period increase to 12 volt, this may disturb the microprocessor enough to cause the lockup.


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## sirimaxi (Apr 7, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

HKJ: Beeing you the one who discovered the issue...Are you in touch with 4Sevens to try the new version charger? Any clue of when this will happen? Thanks!


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## HKJ (Apr 8, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



sirimaxi said:


> HKJ: Beeing you the one who discovered the issue...Are you in touch with 4Sevens to try the new version charger? Any clue of when this will happen? Thanks!


 
I told 4Sevens about the problem with the charger a few weeks before publishing this review, but I do not have any agreement about testing the fixed version.
When I get the fixed version, due to the general replacement of the chargers, I plan on verifying the above data and update the review.

I have no idea when the fixed charger will be available or when I will receive it.


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## Battery Guy (Apr 8, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

HKJ

Very nice review. Thank you!

I like the concept of this charger, but would really like something that could charge more cells simultaneously. Is anyone aware of a multi-bay lithium-ion charger that has similar capabilities?

Cheers,
BG


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## Got Lumens? (Apr 9, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I've had mine open several times. Gimme a minute and I'll check the chips.

Its a 14 leg IC chip, ID on bottom, or MFG no writing. There is a load coil.




HKJ said:


> No, there are no visible screws (They are probably under the rubber feets). I am convinced that it uses a microcontroller, both because of the saw tooth in the charge curve, but also because the lockup looks like something a microcontroller would do.
> 
> 
> 
> ...


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## trooplewis (Apr 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

After spending the morning looking at Li-on chargers on ebay and getting confused, now I am more confused than ever. Should I just wait for the new version 4Sevens?


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## HKJ (Apr 11, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



trooplewis said:


> After spending the morning looking at Li-on chargers on ebay and getting confused, now I am more confused than ever. Should I just wait for the new version 4Sevens?


 
This is difficult to know before I have tested it, but I believe that it will be a very good charger.
A hobby charger can also be used, but if more difficult to work with. Pile has a very good charger, but I have not tested it.
CottonPickers are selling some charges here and they also works well, but does not include a cradle.


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## sirimaxi (Jun 25, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

HKJ: Do you have V2 in your hands to test it? If yes, can you please tell me your first impressions? Thanks!!!!!


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## HKJ (Jun 25, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



sirimaxi said:


> HKJ: Do you have V2 in your hands to test it? If yes, can you please tell me your first impressions? Thanks!!!!!


 
Not yet, shipping does take time.


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## Bolster (Jun 27, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I was about to ask if the new charger was identifiably different, but looking at this post says 

"...it now has markings for negative and positive. Also there are two other noticeable improvements. The first is the larger sized battery contact indents, and the second is they have upgraded the sliding negative post to include a metal slide rail instead of plastic eliminating the wire that was required on version1. This change allows easier sliding of the post, helps eliminate binding, and assists in the loading and unloading of long cells..."

Also says v2 on the back label.


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## HKJ (Jun 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

Added a text saying charger recalled (I will post a V2 review in a new thread).

Added a link to a list of external differences between V1 and V2 charger.


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## sirimaxi (Jun 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

HKJ: So this means you received V2, no?


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## HKJ (Jun 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



sirimaxi said:


> HKJ: So this means you received V2, no?


 
Exactly, you can see it if you follow the link to the comparison.

I plan on doing a full range of test on it, this will take some days.


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## KLowD9x (Jun 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

I received my charger on Monday and I have a question:

Both of my 18650s (AW IMR and AW 2900mAh) get warm when charging at either 1A or .5A charge rates. I never noticed any change in temperature using the DSD charger. Should I be worried? They both come off of the charger at 4.19 volts.


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## JA(me)S (Jun 28, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



HKJ said:


> I plan on doing a full range of test on it, this will take some days.


Thanks HKJ for being so thorough, I eagerly await the results...

- Jas.


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## HKJ (Jun 29, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*



KLowD9x said:


> Both of my 18650s (AW IMR and AW 2900mAh) get warm when charging at either 1A or .5A charge rates. I never noticed any change in temperature using the DSD charger. Should I be worried? They both come off of the charger at 4.19 volts.


 
The 4Sevens is using a higher charger current than the DSD, this might be the reason.


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## HKJ (Jun 30, 2011)

*Re: Review of / Measurement on 4Sevens Single Bay Charger*

The V2 review is up.


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