I need a non-balancing charger...

[donn_]

My requirements:

AC powered
Able to deliver charge current variable up to at least 10A
Selectable cut-off for a variety of chemistries
LED status indicators

I don't need balancing
I don't need computer connectivity
I don't need more than one output port

The charger will be used with a 6-bay parallel cradle , and will be used with LiFePO4s, Li-Ions (protected AWs, Emolis and IMRs) and odd-sized NiMH cells like 4/3As.

Can anyone point me to such a thing, or advise on who could build one for me?

 

[clintb]

Will you always be charging LiIon / LiPo in parallel?

And, for what it's worth, most of the balancing chargers can charge without the balance leads being connected.

That said, check out the iCharger line, specifically the 106B+.

I have two of the 208B chargers and love 'em. More power than just about anything on the market, and configurable for even the biggest bit head.

edit: Oops, just re-read the AC requirement. That will jack up the price a bit. Honestly, after doing the R/C thing for 12 or so years, go with a DC powered charger and external power supply.

 

[donn_]

I'll be using the parallel charger/cradle to do larger quantities of cells at once. I have several different 1 and 2-place chargers when I only need to do a couple cells.

I know the balancing units can be run without the balance circuitry, but if I don't need it, why have it? Same with PC connectivity and such.

 

[rmteo]

I am not aware of any chargers that are AC powered that will charge at a 10A rate. Most require an external 12V DC power source - I use a 12V/35A supply with my charger. This is the one I have ($155):
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPYT8&P=ML

There is a slightly lower spec one ($115) here:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHDJ1&P=ML

Unfortunately, neither has LiFePO4 capability for now - perhaps a future software update will change that. The graphic LCD is very useful during both charge and discharge phases. It will highlight trends that are just not seen when looking at a text only display.

 

[clintb]

I know the balancing units can be run without the balance circuitry, but if I don't need it, why have it? Same with PC connectivity and such.

Because that's the way the industry is going. You're very much in the minority for NOT wanting an integrated balancing circuit. Fact is, the hobby chargers are driven by the R/C world, and they want integrated balancing circuits.

Ok, here ya go:
10A charging: check
AC / DC powered: check
Multi-chemistry, including LiFePo4: check

Swallow any liquids before clicking the link below.

http://www.rcaccessory.com/index.asp?PageAction=VIEWPROD&ProdID=459

Check the "Specifications:" table, first column, second row down. See the limitation of being on the built-in power supply? I'll let you decide if that's a factor.

 

[lolzertank]

It'd be cheaper to just get a DC charger and a computer power supply instead of a AC charger. A decent computer power supply can be had for $30, and can supply 30A+ on the 12V line. Now you can get any charger. :naughty:

 

[clintb]

It'd be cheaper to just get a DC charger and a computer power supply instead of a AC charger. A decent computer power supply can be had for $30, and can supply 30A+ on the 12V line. Now you can get any charger. :naughty:

I agree 100%! No, wait, 105%!!

Let's check the pro's and con's of an integrated AC power supply.

Positives:
- Convenient
- Cleaner (less cables, less equipment)

Negatives:
- Less power, depending on your choice of external power supply
- If the internal PS fails, you lose the charger when you send it back for repair.
- You can't share the integrated PS with another charger.
- Charger is physically larger to accommodate the PS.
- Price
- Much smaller selection of chargers.

That's all I'll say on that subject. I'll continue to help with options though.

 

[donn_]

Alright alright. I'm convinced. I'll consider a DC charger and a PS.

 

[clintb]

Cool. With the original requirements in mind, less the built-in AC power, let's move onto the others:

LiFePo4
10A charge
Charge protected cells (not all chargers can do this)
Multi-chemistry (LiIon, LiFePo4, NiMh)

The iCharger 106B+ meets all requirements. It's incredibly powerful under the hood, but also very simple to operate. Just about everything has an adjustable cut-off, so you can undercharge cells, if that's your preference. Or, you can hit 4.20V right on the money for that extra bit of run time.

For power supply requirements, here's a great read:
About power supplies

I have this power supply:
iCharger P350 Admittedly, it's kind of expensive when compared with a DIY server power supply, but it's quiet and small; both important for indoor use.

There's tons of choices in power supplies; some cheap, some expensive, some DIY computer gear, most ready-to-go.

Info for the DIY power supply route:
IBM 235 Server Power Supply

Some information on parallel charging:
About parallel charging of Lixx / PB packs

That should have you reading for a bit.

 

[donn_]

I've been reading about power supplies, which of course brings up even more questions.

Couldn't I do what I need to do with a power supply alone?

A variable PS, which allows control of both voltage and current output, seems like it could function as a charger.

No? Something like this? If I went this route, I could always add a charger later if I decided I needed to charge series packs.

 

[lolzertank]

I've been reading about power supplies, which of course brings up even more questions.

Couldn't I do what I need to do with a power supply alone?

A variable PS, which allows control of both voltage and current output, seems like it could function as a charger.

No? Something like this? If I went this route, I could always add a charger later if I decided I needed to charge series packs.

You could do the CC and CV stages, but you would need to monitor it so you can shut off the charge once the current drops below 1/10th your original charging current. A good Li ion charger will do that automatically. Also, you'll need to charge at a lower rate if your cells are below some threshold (3V for LiCo, don't ask me for LiFePO4). It's a lot of work and there are many ways you could mess it up.

One last thing. Keep in mind that it is practically impossible to fast charge NiMH or NiCD this way in case you ever need to.

 

[jchoo]

You could always build your own.

http://shdesigns.org/lionchg.html

I've used this basic design to charge 2x14500 in series with great results. I'm sure you can up-rate the components to handle the current you need, and calculate out the appropriate resistor values. Remember, you're basically looking for a cutoff of 4.2v for a single cell, and a charge rate of about .7C. With this design, as the battery voltage reaches the programmed maximum, the current drops off toward 0. It will never overcharge a li-ion cell because of this - so you can, without fear, leave stuff hooked up/plugged in for days/weeks/months at a time. I really am not sure how you would use something like this to charge multiple, different cells in parallel... you would have to figure out what value you would have for C based on each configuration you could charge at a time. Maybe you can add switches/jumpers that you can turn on for each cell you put in - say if you have 3 18650s and an rcr123, connect jumpers/rotate selector to put the appropriate resistors in line for each cell type.

I can see something like that being one heck of a bird's nest, though...

 

[donn_]

Monitoring the charging process is not a problem. I've gotten into the habit of doing this whenever I charge Li-whatever cells.

If I can maximize the charge time, there will be less time to have to monitor it.

75% of the cells I have in use are A123, so that will be the chemistry I charge the most, and I need to develop the best system for fast-charging them.

I just found another interesting PS. 3 output channels with quite a few potential configurations.

Another question to throw into this issue:

A123 cells can be safely charged at 4C (although some say more than that). On a single 26650, C= 2.3aH, so safe charging maximum is 9.2A.

My parallel cradle, filled with 6x 26650 cells has a C of 13.8aH. Does that mean I can run 55A into it safely?

 

[lolzertank]

Monitoring the charging process is not a problem. I've gotten into the habit of doing this whenever I charge Li-whatever cells.

If I can maximize the charge time, there will be less time to have to monitor it.

75% of the cells I have in use are A123, so that will be the chemistry I charge the most, and I need to develop the best system for fast-charging them.

I just found another interesting PS. 3 output channels with quite a few potential configurations.

Another question to throw into this issue:

A123 cells can be safely charged at 4C (although some say more than that). On a single 26650, C= 2.3aH, so safe charging maximum is 9.2A.

My parallel cradle, filled with 6x 26650 cells has a C of 13.8aH. Does that mean I can run 55A into it safely?

Uh... yes. I think you should look into purchasing an extra set of car jumper cables for hooking the cradle to the power supply.

 

[rmteo]

How about this one (I use it as my bench supply), 0-40V, 0-30A:

http://www.valuetronics.com/Details.aspx?Prodid=53

 

[donn_]

$1500 stripped?!?

 

[Raoul_Duke]

If you do monitor your cells, and want to charge your A123's ( M1's) real fast you should read into ( google) "Zip charging".....looks crazy ...but the data behind it ( that I read on RC forums) shows that there is negligible or no cell degredation compared to normal charging....A123 are tough cells...but it still looks bonker though :huh: :duh2:

 

[45/70]

You'll be fine for the lithium ion chemistries, I Just thought I'd bring up that NiCd and NiMH cells don't take kindly to parallel charging. If you do charge them in parallel, as clintb mentioned, you'll have to charge at a slow rate. Charging a single cell of course, wouldn't be a problem.

I'm presently investigating hobby chargers myself, something I've really needed for a while. I have a 4 bay parallel cradle conversion in progress, but am still trying to figure out what charger to get. I'm leaning towards something like a Thunder AC6 which is AC/DC powered, but hadn't considered what would happen if the internal PS fried. Since I'm a ham, I have available several adequate PS's, but I'd like to keep the cluster xxxx around here to a minimum. If the internal PS fries on one of these, can you still run it with an external ~12 Volt PS? Or would other components be effected and the damage already done?

Oh, and donn_, while I find your cradle to be a marvelous creation, if it were me, I'd figure out a way to solder every "loose" connection you can. I can't imagine the total combined resistance in that setup. Those springs (that appear to be "spring steel") for instance. I would solder a bare multi strand 18 gauge copper wire from the bottom, or negative "runner" to the pipe cap that makes contact with the negative end of the cell. This will effectively bypass that resistance problem. That alone would make a big difference. If you do nothing else, you'll have to keep all the copper/brass contact areas bright and shiny (don't use Brasso, it has wax in it), or you'll be running into very high resistance figures.

It would probably work, as is. You might as well make it better though, right?

Dave