-- THE SINGLE CELL CHARGER POST --

Well, the coolest thing to do with the 2 - 10s4p packs that I hope to configure, would be 20. That way, I would not have to unhook anything ever, plus cut the charge time in half. I just might be able to cram this all in my rear bag if I put some thought into it. Can't wait to plug in at work and use thier electricity ! :twisted: :oops:
 
Like many here, I think individual cell charging is the best way to ensure that the cells are always well-balanced. The only problem is that the little 2A chargers take forever if you have a a lot to put back in the pack. To get around this problem, if I'm in a hurry, I usually use a big Zivan NG1 SLA charger to get the pack to the point where it first hits the cutoff, where it would switch to the CV mode, and then I unplug it, and let the individual chargers take over and finish "topping off" and balancing the pack.

This process works, but it is a bit cumbersome. I decided to try and figure out a way to make this easier. What I came up with is to use a "booster" power supply that is connected to the main power leads on the pack, while the individual chargers are also connected. I used a modified version of the LVC circuit to detect when any one of the cells first hits 3.7V. When that happens, a solid state relay, which is used to control power to the booster supply, drops out, which cuts power to the booster PS. The supply for the relay control is also connected through the relay, so once the relay drops out, it stays off.

Here's what he functional diagram looks like:

10-Cell%20Boost%20Charger%20Circuit.png


This is not the "ultimate" solution, but it does allow unattended fast charging, with full balancing. I will prototype this, and post my progresss here.

Thanks to Rchard and Bob, for helping me get some circuit issues sorted out. :)

-- Gary
 
mobile phone chargers i've been using are just for single cells,
max voltage varies depending on charger can go up to about 5volts,
but the ones ypedal has at 7.2v sounds quite high for one cell, but too low for two cells in series?
but when charging the battery pulls that voltage down anyhow,
batteries seem to get up to about 4.3v or a bit higher ( from memory) chargers just standard mobile phone type chargers, the voltage drops down to around 4.2v after taking off charger. Strangely enough after discharging some cells and leaving to sit for a while they come back up to around 3.7volts, I thought would stay at lower voltage.
 
Good idea Ggoodrum, It seems to be safe and fast.

About the cell charger, i've been watching my 3 cellphone cahrger few hour and wondering if i can do something with those.. but apparently not... they have 5V around 1A but 1A would charge too slow and todrop from 5V to 3.6-3.7V we would need to add some 1N4007Doide in serie to lower the voltage... that seem stoo complicated for the performances...

Now, what do you think about that:
cheap_multicell_charger_125.jpg


The critical job would be to precisly adjust the number of turn of each secondary to get around 3.6V and not blow the zenner. The bulb would act as a current limiter for the CC step.

Doc
 
5v switching power supplies, like cell phone chargers, are becoming very inexpensive these days. Some of them have very ample output currents.
A 5v supply with a 16.8 amp output for $6.00 from MECI can't be beat.
http://www.meci.com/product_info.php/cPath/465_112/products_id/5002001

Old computer power supplies are in the same range.

If we figure out an easy way to turn a 5v supply into a single cell charger, you'd have it made. I'm sure if you reverse engineered the circuit, you could just change a resistor to get 3.7v or whatever.
 
fechter said:
If we figure out an easy way to turn a 5v supply into a single cell charger, you'd have it made. I'm sure if you reverse engineered the circuit, you could just change a resistor to get 3.7v or whatever.
Click to expand...

Great idea if it could be done easily!
 
I like your idea for cuttoff of the bulk charge. You might employ a timer for this, just making sure you know the limits and the depletion?
Jeff K.
 
has anyone got a link to the single cell charger group buy? i can't find the link now :S

i'm in for a dozen...
 
Just came across this item at All Electronics ...

A 5-volt 3.7amp `wall wart' switching power supply.

http://tinyurl.com/2vlkdf
 
Ypedal said:
2 amp charge per cell = 2 ah per hour..

So 10 ah pack fully dis-charged = 5 hrs.

20 ah = 10 hrs !!!!
Click to expand...

Is the full 2 amps the chargers are supplying actually getting to the cells? I thought there were charging losses, so only 1 amp - 1.5 amps were actually storing as charge...

-JD
 
Ypedal said:
Good question, i just finished draining exactly 2ah from the pack for this reason.. !
Click to expand...

Gaston, you and I keep going down similar paths :D I think your experiment above will show how long it takes to put the LAST 2ah on your pack - and I expect that to be much longer than the FIRST 2ah.

In the past, I was content to just slap a pack on the charger and grab a different one, so I didn't pay much attention to it. I have been messing with Flintstones chargers, I got them working but of course the 'charged' indicator light is useless. Armed with what I learned along the way I have been trying to find out how long they need to get fully charged.

First I balanced the pack, discharged it to 35.5v (under load) using my CBA-II. Then I charged it for 1 hour, and discharged again at 2.37a to 35.5v, pulling 2.8ah from the pack on the CBA-II. Then I charged it for 4 hours/45 minutes, and got 10+ah before it reached 35.5v. Finally, I charged it for 18 hours, and got 11.x ah to 35.5v.

This says to me that at the most optimum (mostly discharged) rate the cells are accepting 2.8ah of the 5a the charger (allegedly) supplies. Since the pack was not fully charged after 4.75 hours, then it isn't accepting 2.8a through the whole cycle. Do to this right I should do a series of charges in 1/2 hour increments and graph the resultant ah discharge.

-JD
 
I would ditch those chargers personally.. they scare me.

If for some reason the breaker/fuse goes out, that charger's fan will keep turning ( powered by the pack ) and keep on draining until it stops. On a full charge that would take a long time.. but if you hook it up in a discharged state .etc.......

took aprox 12 hrs to charge 23.3ah worth with the VP chargers.. was done in 2 charge sessions so i have to repeat it taking note of the time.
 
Ypedal, Have you a capacity/internal resistor meter for battery? or a RC charger that allow you to measure that?

It is VERY usefull :wink: The one i bought is the best cell testing tool i have!.. it discharge 50W and CHARGE 180W.. the CBA is good too but can't cahrge and give the capacity on charge to compare with discharge capacity.. a great clue of the state of the cell!

My charger (the 960sr from mega power (a copy of the robbe infinity III) is also compatible with logview:http://http://www.logview.info/cms/d_screenshots.phtml with rs232.

I like it!.. 8)

if you couls test each 1p cluster with that, that could probably match with your green light charger comparing time vs capacity to charge...
 
rf said:
Just came across this item at All Electronics ...

A 5-volt 3.7amp `wall wart' switching power supply.

http://tinyurl.com/2vlkdf
Click to expand...


I found the jackpot: 3.3V +/-10%adjustable =3.63V at 8A switching for 12$ :wink:

http://www.web-tronics.com/253siouposup.html

webtronics_1976_23425157


Complies with RoHS Directive
AC Input Voltage Range: 85-264VAC (120-370VDC)
Input Frequency: 47-63Hz
Inrush Current: Cold Start, 20A/115V, 40A/230V
Input Leakage Current: <0.7mA/230V
Line Regulation (Full Load): <± 0.5%
Output Voltage Adj. Range: ± 10%
Output Overload Protection: 110-150%
Output Over Voltage Protection: 115-150%
Withstand Voltage: I/P-O/P: 3.0KVAC/1min; I/P-F/G: 1.5KVAC/1min; O/P-F/G: 0.5KVAC/1min
Rise Time: 50ms@full load (typical)
Hold Up Time: 20ms@full load (typical)
Operating temp.& humidity: -10°C to 50°C (14°F - 122°F), 20%-93%RH (non-condensing)
Storage temp.& humidity: -20°C to 85°C (-4°F - 185°F), 20%-93%RH (non-condensing)
UL Ref. Number: E258719

Safety Standards: GB4943, UL80950, EN60950
EMC Standards: GB9254, EN55022 classB, EN55024, EN61000-3-2,3, EN61000-4-2,3,4,5,6,8,11
Cooling Method: Convection
Dimensions: 3.94 x 3.28 x 1.4"

The best we can find i think!

1+ $14.90ea.
10+ $12.60ea.
100+ $10.78ea

8A at a great 3.63V would be perfect to charge a:

- 1p pack in 15min
- 4p pack in an hour

140$ for a 288Watts 10s 36V charger that charge 8A !!

Doc
 
20 for me

20s 210$ ---= half KILOWATT FAST SAFE BALANCER CHARGER=-----

8)

who's next?



(the 20A model is also availlable for 26$each .. think about a:
1.4 KILOWATT ...20s :twisted: 20min to completly charge your ride :shock: http://www.web-tronics.com/103siouposup.html
 
I also found this baby:
PS-637.jpg


MULTI VOLTAGE !!! imagine having 4.2V AND 3.6V out on the same!!! to allow you to charge lipo-regular 18650 and LiFe !!!! I just hope the pot is to adjsut the voltage tolrrence... to drop 5V to 4.2V and to also be able to boost the 3.3 to 3.6V like the previous one on webtronic...

the price: 5.50 for 14+ !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :shock:

5V/8A, 3.3V/4A, 2.5V/2A POWER SUPPLY

HERE ---- http://www.allelectronics.com/cgi-bin/item/PS-637/480/5V_8A,_3.3V_4A,_2.5V_2A_POWER_SUPPLY_.html

it's my pleasure!...

Doc
 
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