Use hobby charger for capacity test?

[johnnydoe]

Hi,

Lately I have been wanting to test my batteries capacity more and more and have been looking for a solution to do it.
Since I don't want to spend too much attention to it, and love my maha c9000 for AA's and AAA's I was looking for something similar for my 18650/14500/16340 3/3.6V batteries (most protected, some unprotected, so I hope this is no problem)

During my search I came to the conclusion a hobby charger would be the best option, but if something has a better option please do mention.
I've also read contradicting claims and didn't find a full answer to all of my questions, so I decided to spill my thoughts and hope some of you can help me decide.

First I need to mention that I will most likely only will use it to discharge and determine the capacity. To charge my batteries I have other dedicated chargers. Although the idea of an all in one charger does sound good and I do own several types of batteries, a quadcopter and a RC car I don't really need another charging device.

Looking at this I was wondering if I could do with a fake imax b6? I've read all sort of stuff about not being to accurate with charging and bad balancing, but those would not be an issue for me. The cheapest (and from a reliable source) genuine would cost me around 45$ and a fake one can be found for under 20$
The price of a charger is not calculated into this. I do have an old laptop power supply that put's out 12V 4A. Looking at the specs it looks to me that I can use this power supply without problems since the max discharge current is 1A. Even for charging it could be used I guess but in that case I wouldn't go over 3A I think.
I've also looked at the b6ac+ which would cost me 65$

Well, now you guys have some background info I hope you can help me with my decision.
In short I'll summarize my questions.
1: Is a hobby charger the best option for me?
2: Will it safely discharge my batteries, even the unprotected ones?
3: Will a fake imax b6 do for me or is it too unreliable even for discharging and capacity testing only?
4: Is my 12V 4A PSU sufficient?

If there is anything else you want to know, feel free to ask. If you have other usefull idea's or tips, please tell.

Thanks for taking the time to read this and already a big thanks for those that will try to help me :thumbsup:

 

[torukmakto4]

1. I would get one if you don't have one already - with all those pack-equipped things to charge as well. Others here may have a better idea (CBA type device?) purely for discharge testing.

2. As long as it cuts off somewhere near manufacturer rated cutoff voltage, yes.

3. There is no reason ANYONE should buy or use a fake IMAX B6 or any other clone, ripoff, fake or Chinese house branded hobby charger. Sketchy Li-ion equipment is not to be messed with. You can get a genuine (but still admittedly low-end) Turnigy Accucell 6 from HK for the same price or less and it has a better reputation than the real IMAX which is also known to be somewhat inaccurate. It doesn't make any sense to intentionally buy a crappy charger knowing full well that it is junk, even if it will only be used to measure capacity.

4. Yes, and it's done all the time, but I would use a bigger PSU such as a 12v 6A on a 50 watt (maximum output power rating) charger, for the same reason that you don't install a 5 amp breaker and 20 AWG conductors to an electrical outlet that you only intend to use for a lamp.

I guess what I am trying to say here: Hobby chargers are versatile pieces of equipment that can really earn their keep. Make the effort (and maybe spend a few dollars more) and set up right the first time.

 

[malow]

i have a turnigy accucell 6, great charger, not too powerful, but great for the price.

but for capacity test, i recommend another charger. the voltage difference when discharging is high and progressive worst depending on the voltage. (measuring on the charger connector)

now i got a Turnigy Smart6, and discharging is much more precise.

also, these cheap chargers do not have much discharge power (5w only)

my opinion on your questions:

1: Is a hobby charger the best option for me?
not the best, but a good one (also depend on what hobby charger)

2: Will it safely discharge my batteries, even the unprotected ones?
yes.
3: Will a fake imax b6 do for me or is it too unreliable even for discharging and capacity testing only?
cheap products are already a lottery sometimes, fake ones are even worst.
you can buy a "reputable" charger, like the iCharger, or some "cheapy" ones, like Turnigy's. you choose the quality with your wallet

4: Is my 12V 4A PSU sufficient?
for discharging, yes. for charging, recommend something better. for a accucell 6 for example, a 15v 5A notebook power supply is sufficient. depend on the charge "power" you will use. the Turnigy Smart6 im using now is 80Watts, so i got a 105Watt power supply (a more powerful power supply is always a good choice)

 

[johnnydoe]

Thanks for the input!

Well, won't be buying a fake imax. Couldn't find much about the quality when discharging, but since that's also very shady, I won't be risking it and better buy something of more quality that can also be used to charge if I decide to do that.

I did some more research and found I made a calculating error. Real imax on HK is 25$, but with 10$ shipping it would be 35$. I used this 35$ to calculate what I had to pay for taxes and that would have added 25$. But since the original item is under tax free import limit, I don't have to add the shipping costs. (Although when the item is above the import limit, shipping costs do count, kinda confusing)
So a real imax or accucel is an option again.

Seeing as both of you recommend the accucel over the imax I think I'll go with the accucel.
I do understand it's still a low end charger, but as a starter it should do I guess.
Will lookout for a more powerfull PSU also.

Thanks to the both of you for helping me! Made my decision much easier!

 

[tatasal]

Have you considered iCharger's entry-level 106B+ hobby charger? It has no reported counterfeits, can discharge up to 7A, charge to 10A, and very accurate. ( I have one, btw )

 

[johnnydoe]

Thanks for your suggestion.
It does sound very promising, and I like the usb output, but, it's way over my budget. 95$ with shipping + 37$ taxes and administration fee. 50$ total would be the max and is actually already stretching it. But since 29$ is the max tax free import limit, and everything above that will get minimum 18.5$ administration fee, there's not much room to play with.
Or something has to be found within europe. I also checked hobbykings europe warehouse, but the turnigy smart6 for example is around 62$ with shipping. Looking at the accucel 6 which is 23$+10$ shipping, would it really be worth it to spend almost double?
And maybe it's just not the right time for me to buy a hobby charger. I do want quality, and more important safety, but budget is kind of an issue.

 

[tatasal]

Sent you PM

 

[Serenity]

I liked the capacity test of NiMH cells as well, and was thinking a hobby charger would be great for Li-ion as well, preferably with USB connection for logging etc. But when the XTAR VP1 was released and got good reviews, I decided that the voltage display (for checking charging progress) and ease of use was probably more important for me, and I got that.

But I'm still thinking about options to measure capacity. One of the easier ways with standard components would be to just use a power resistor and multi-meter with PC connection. A more recent thought has been use the light sensor of a smartphone or tablet to log the lux over time, and derive it from that. Making a fixed current discharge circuit with low voltage cut off, shouldn't be too hard either, would just need a way to easily clock the discharge time. Could still use the light sensor of my phone for that.

There is some more information about checking capacity in this topic as well: http://www.candlepowerforums.com/vb/showthread.php?344432-battery-capacity&p=4026463

 

[johnnydoe]

Alrighty.

Wanted to give everybody some feedback about my final decision and how it worked out. Always hate it when threads end without feedback from the original poster.

After thinking some more about it I decided to go with the accucel 6 from hobbyking.
HK did declare the real value, but without shipping costs so there was no problem with customs for me.

After receiving it I immediatly put it to the test and started with some old nimh rechargables to get to know the device a little better and still be on a more safer side.
Afther this I started testing some 18650's capacity and a powerbank and are satisfied with my results.
Although the device might not be 100% accurate for now it gives me good enough data.

Only thing I noticed is that my multimeter that I also have attached gives a 0.08-0.12V higher voltage during discharge, but this might have to do with the used cables, or the multimeter itself. In the calibration menu the values are the same so I guess it's alright and if not at least it does not cuts off charging lower than 3V.

All in all I'm happy with the purchase and want to thank you guys again for your advice. Without your advice I might have bought some useless device.