Single cell charger - where to buy?

[manfred59]

Hello to everybody here in this nice board!
I am from Austria in Europe, and I have already read some topics which are very interesting to me. I built a small golf cart to step on it to go around the golf course. Two hub-motors 400W each power up the cart. My battery is a pack with 72 a123 cells with 2,3AH of capacity. So the problem for me is the cheap charging this batterypack. I use a 12s6p pack. So I thought the cheapest would be a single cell charging solution as GGoodrum shows. My problem is ordering the singlecell charging units from Voltfreaks because he only has 11 items (some days before) in stock and the costs have gone up 60% on the next order. Does anybody know another shop for 2A single cell chargers or would somebody even sell used or new ones to me?
manfred

 

[green hornet]

Why single cell chargers..?
Why not use a 43.8V, 4Amp regular LiFePO4 charger from FalconEV ?

 

[GGoodrum]

Why single cell chargers..?
Why not use a 43.8V, 4Amp regular LiFePO4 charger from FalconEV ?

If you used something like this, which only bulk charges the whole pack, you would also need to monitor each block of cells, just to make sure they are staying reasonabley balanced. If the cells do start to drift apart, you could either use an RC-styled auto balancer, or maybe just buy one single cell charger to bring up the level for the low cells.

Bob Mcree and I are working on a new "Charge Management System" (CMS) board that will be able to be used with bulk chargers, like the FalconEV unit, and have individual outputs for each cell/block of cells in series. As each cell hits 3.65V, the circuit will individually let each cell gradually lower the current it accepts, while still passing on whatever current the lower voltage cells need in order to "catch up". This way each cell gets what it needs, which won't be the cse with a bulk charger, if you have some cells that are lower than the "fullest" ones. What happens is that the high cell voltages will quickly start to rise, when they are full, which will put the charger into the CV mode too soon. You could have the extreme case, for instance, where some cells are still at like 3.3V and some are rising to as high as 4V. Combined together, the total can be at the 43.8V point, which causes the charger to limit the voltage. This in turn, causes the current to drop. Since all the current has to go through all the cells, you can end up with the low cells never receiving enough current to reach the 3.65V "full" point.

With a shunt-type voltage regulator on each cell, what happens is that the high cells will start reducing the amount of current they can accept, down to the point they are completely full, but whatever current they don't use is "passed on" to the next cell, so that if it needs the full current in order to catch up,it can. This allows each cell to "get full" at its own rate. Once they are all at the cutoff, the bulk charger will see the 43.8V total, which it will limit. Eventually the current will drop down close to zero, which means all cells are completey full.

In bigger vehicle full-blown BMS units, these regulators are resident in the pack. These BMS units also usuall include over-current protection, and low-voltage protection. The controllers we use already have the current limit function, which can be done at the pack level, as all the current has to flow through all the cells. Low-voltage protection, however, needs to be done at the cell/block level, which is why that's all we are making "pack-resident". Further, most "big boy" BMS units do absolute pack cutoff if the LVC or over-current circuits trip. Again, with our ebike controllers, which have convenient "brake inhibit" inputs, we can eliminate the big power switches that have to be able to switch the total current on an off, and let the controller do it. It is very simple, if the the LVC circuit for any channels trips, it tells the controller to cut the throttle.

What is left out of what would normally be in a full-blown BMS is the veltage regulator circuits for balanced charging. This is what we are putting into this CMS board. It does mean that we need to bring out the cell junctions, out of the pack, but this can be done in one cable bundle that terminates in a multipin Molex connector. Still one charge plug and one cable, but it just has more wires. For typical 12s and 16s setups, this is certainly manageable.

-- Gary

 

[recumbent]

Bob Mcree and I are working on a new "Charge Management System" (CMS) board that will be able to be used with bulk chargers, -- Gary

Oh yeah,That would be very convenient, and give our battery pack a longer life. Hope you have those boards available for us this summer. Nice to hear these things developing.

 

[Ypedal]

What are the specs on this charger ? ( How many amps )

The casing looks exactly like my soneil 1A 12v SLA charger. :wink:

 

[EMF]

Any way , Yesa Battery is always ready to help people to slove problem .

Great! Did you see this thread? http://endless-sphere.com/forums/viewtopic.php?f=14&t=3079

 

[recumbent]

The single cell charger output: 2A

I think the Yesa chargers are a cost effective alternative to others that cost twice as much.
The 24-V, 3-amp was about $50, the 48-V, 3-Amp charger was approx, $70, according to my quote a month ago, but no price on the single cell charger. I think my order will be all three at once when I order 32 "Lifebatts" as well, Oh yeah man can't wait for the fun to begin

 

[manfred59]

Last week I have got these YESA single cell chargers, due to the New Year delay in China.
As I checked the voltage I was a bit surprised output 3,9-4,0V ! and current 2 A. Charging 1 cell it could be more than 2A at beginning of charge!
My question:could that voltage for A123 LiFEPO4 be a problem?
How could this voltage easily reduced to 3,7V?

 

[Ypedal]

The voltphreak chargers do the same thing.. in a way.

The red light ( 2 amp ) starts to turn orange at 3.6 to 3.7v then goes green within 5 minutes.. over the next few hours the voltage drifts up to 3.80 to 3.99v, i have not seen them go as high as 4.0 + yet tho..

The voltage will go up quickly after 3.650v with little current on the 3 types of LiFe cells i've testes so far.. none of them A123....

as long as the 2 amp charge stops at 3.6v it's not much of a problem as far as i can tell, one cell per charger regulates this well.. if you had a bulk charger that allowed 3.99v per cell and one was low then it would be a different story.

 

[fechter]

How hard is it to open the case? Sometimes those things are glued pretty good.

 

[Doctorbass]

Hey guys, why dont you all consider to buying this power supply as charger?:

10 for 12.60$each !! same price than voltfreak chjarger but 8A

It can hold 12A until it reach around 3.5V after that it stabilyse to 8A and keep the 3.63V for the end of the charge

I have one of these!

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

8A 3.3V adjustable to 3.63V using the +/- 10% pot

120V input isolated in/out! so you can without any problem wire them in serie!

spec:
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


They also have the 20A model for 26$

Doc

 

[Doctorbass]

They could be great, but you could need to put a serie resistor between the cell and the power supply to limit current from going into protection mode at the begining of charge.. but maybe not.. that worked great for me for 2.3Ah test (one A123 cell) but at 40Ah, bayme the voltage will keep lower at the begining of charge.

I would suggest you to order one first and to test . they also have a 20A 3.3V in limited quantity for 21$ instead of 26 check that with circuit specialist saler.

Doc :wink:

 

[A1234LIFE]

I second the power supply suggestion. I have been using three of the 20A - 100W models for about a month to charge 60 cells. Only takes about two hours to get the packs full after an 80% discharge.

I updated my build thread to include pictures of my charging setup. Just go to the last post.

http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=3171&st=0&sk=t&sd=a

 

[RLT]

FOR LiION and 'old school' LiPO batteries:

Decided to try this single cell charger idea myself, due to bad luck with my BMS boards

Ordered 11 of these 2A CC/CV 4.2V LiIon chargers

Here is a professional RC charger for single Li-ion application. It features sharp auto charging cut-off when battery reaches 4.19V-4.2V, no trickle charge. This is a CC/CV charger, meaning it charges with constant current at 2.0A in the beginning. When battery voltage is close to 4.2V, it changes to constant voltage mode to top the battery capacity up to whatever the battery can hold (before reaching 4.2V), without using trickle charge. I have been using this charger to charge my 32650 5000mAh Li-ion and shows very good result. Charging time is about two to three hours (battery measures 2.75V at the start).

http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=4001

They cost me US$8.99 each, shipping included for 11 of them in a single order (without the individual cell holders mentioned in the item description page).
Never have tried the chargers before, so I can't actually recommend them yet. But they are cheaper (in quantity) than the single cell 1.5A LiIon chargers from batteryspace...
(Although I'm not sure that everyone else would be able to get the same price, as I also ordered $1300 worth of batteries at the same time, so that may have affected my charger price... or not.).

Anyway, if you are interested, email Amy at: wholesale@kaidomain.com to see what kind of deal she can give you in quantity. They are $14.99 each individually, shipped.
I can recommend the company; I've been doing business with them pretty regularly for a couple of years.... Tell 'em Robert sent you