-- THE SINGLE CELL CHARGER POST --

[Doctorbass]

Today, i bought this power supply at ALL ELECTRONICS.com

5V/8A,

3.3V/4A,

2.5V/2A

I will let you know how it is and if it's possible to increase the V Adjust tolerence to drop the 5V to 4.2 and also to boost the 3.3V output to 3.6

If i can, that power supply will be able to charge both A123 and Konion!!

Probably that the potentiometer have some serie resistors with it that i can modify to increase teh range of the V adjust. i will test if it oscillate in these conditions.

maybe i wil ltry ti use some diodes to drop the excess of voltage if it become harder... 0.3 to 0.6V should be ok.

Anyway.. at 5.50$... if it blow, i will not need to border with that...


Doc

 

[EMF]

Good find. If you could adjust the voltage, this would be a great A123 charger! $5.50 wow! 8) I already see one pot on there. *drools*

 

[Doctorbass]

I just come from our Quebec bigger Electronic store: MADISSON also called ACCES ELECTRONIC, and i found a great DC-DC power supply!

MOdel: SD-25B-5
Manufactur: Mean Well
price: 5.99$
Out: 5V 5A adjustable, IN and OUT isolated to 1500V
In: 19-36VDC 1.6A
Eff 72%

Very small!! 4" x 4" x 1.3"

http://www.power-factor-1st.com/shop/dc-dc-converter/on-board/sd-25.html

I had not been able to resist to modify it to increase the +/-10% of the V adjust

I located the potentiometer and i noted that i have a srie 1K resistor connected to it so i plugged it to test it with my 20V power supply at input and i measured the output. I got 5.05V... I turned fully counteclockwise the pot and i got 4.32V... not bad.... but it have 120mV too high for me...

I put a resistor in parallel with the 1K and i observec that the voltage increased... That mean i need to put a higher ohm resistpr to decrease the 4.32V. I put a 1.5K instead of the 1K and i finally got 3.9V

Then i carefully adjusted it to 4.200V

I have now a power supply capable to charge any 3.7V li-ion/lipo cells!

What is great with it is that it is isolated I/O so i can use the exact same power source to supply many of those DC-DC units... !

Let say 24V 16A coming to 10x 4.2V 5A independent output!!

total cost: 5.99 x 10=59.90+ + tax = 70$ for a 42V (4.2V x 10) 5A balancer charger!!

not bad! 8)

On the website of MeanWell, they also have modular multiple isolated output of 3.3V adjustable+/-10% perfect for the A123!!!
just click the link below and open the popup (the PFD)

http://www.meanwell.com/search/MP-1K0/default.htm



Next step.. increasing the resistor to lower the output to 3.7V for the A123

:wink:

Doc

 

[EMF]

Yes I agree this is the next step! :lol:

 

[EMF]

I attach the Single LiFePO4 cell Charger picture below for people to refer to .

Charging voltage: 3.5V
Charging current: 2A

Can you open that thing up with a screwdriver? Or would you have to cut it open?

Also, What is the price and availability?

Other members have already found a single cell 2 amp charger that is quite inexpensive, readily available, that can ship to our door in a few days. But, you cannot open them up they have to be dremeled open. (Although I have bought a hot knife that attaches to a soldering iron that might slice into these puppies)

What we really need is a CHEAP single cell charger like that with about 10 amps! So we can parallel charge 4-5 cells in one hour. I guess the leads would be a tad thicker though.

 

[Deepkimchi]

I attach :wink: for your reference http://hobbycity.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=6301

 

[Doctorbass]

I've bought 13 Artesyn DC-DC converter on ebay. Total 157$

They are the one that Bob talked before. I really think that is teh best and flexible charging solution for me.

-5V 60% to 110% adj (3V to 5.5V)
-30A !!
-36-75V input
-Isolated in/out (i will be able to use the same input power supply for all unit in serie)

Imagine 30A charging per parallel cell groupe !
and ADJUSTABLE !! ex 3.6V AND 4.2V.. I will be able to charge both cell type with those!

See the exemple with 72 A123 cells:

30min full charge time at 5A per cells!

 

[fechter]

That's a great setup! Fully isolated outputs too. Very modular and expandable to any number of cells.

I just hope they don't run out of stock on those converters.

 

[Deepkimchi]

How much would it pull from the AC wall outlet ?

DK

 

[magudaman]

It looks like if he were running full out putting out 30amps at 3.6v that would be 108w a unit plus the inefficienties of the units. On 12 cells that like 1300 watts at the outlet if not more. His power supply will output 1440 watts.

 

[Doctorbass]

these power supply are 82% efficient so if i use 30A for each block, with the A123 cells, that would be 3.6V*30=108W *(1/0.82) =132W

http://www.artesyn.com/media/pdfs/bxb150s.pdf

they are normally between 125 and 150$ each at digikey BUT on ebay they are 10$



15A * 120V =1800* so with that i would be able to charge at full power 1800W/132= 13.6s 3p serie cells (let say 3p 13s cells)



if you charge at the max C rate the A123 that is 4.4C (10A) each parallel group would have 3cells so i would be able to charge fully at max charge rate 3x13cells =39cells in 15minutes !!!

so 15 minutes of charge for 39x6.8Wh per cell=265Wh

At 15Wh (at 35kph) per km that would be possible to travel 18km = 30min of ride for 15 min of charge.. not bad at all :wink:

Doc

 

[fechter]

You might get a lot of heat with all those running at the same time.
The dc-dc units have a heat sink on the bottom. I'm not sure if you can run them full power without additional heat sinking. For sure you'll have to leave some space between them and use some fans.

On the other hand, since the batteries will charge up so fast, they might not have time to overheat

 

[tailwind]

I was hunting around on the web and found this single output power supply.
http://www.snaptec.com.au/acdc/acdc.htm#GT50

Universal Input 100-264VAC.
Custom Voltages from 3.3V to 48V in 0.1V increments available upon request.
Constant Current versions available for battery charging applicaions

Example unit, 3.6V and 0 - 6.0A output.

Problem is you might have to order a minimum number and I dont have any idea about price.

http://www.ferret.com.au/articles/z1/view.asp?id=2272

Greg

 

[flip_normal]

Could those Artesyn BXB150-48S05 5V 150W DC/DC Converters also be used somehow for regen with a 3 phase rectifier thingymabob on the motor phase wires and a large smoothing capacitor. They're good for quite a wide input voltage range and can certainly handle the current. They have auto reset (non latching) for over and under voltage conditions and when they're off excess current could be dumped into a high power resistor. Maybe?

Also if these are good for 150W then at 3.6V wouldn't the current be ~42A. Have you received yours yet Doc? if so then have you had a chance to test this?

 

[Doctorbass]

Could those Artesyn BXB150-48S05 5V 150W DC/DC Converters also be used somehow for regen with a 3 phase rectifier thingymabob on the motor phase wires and a large smoothing capacitor. They're good for quite a wide input voltage range and can certainly handle the current. They have auto reset (non latching) for over and under voltage conditions and when they're off excess current could be dumped into a high power resistor. Maybe?

Also if these are good for 150W then at 3.6V wouldn't the current be ~42A. Have you received yours yet Doc? if so then have you had a chance to test this?

No, i dont.

i live in Canada and they ship only to the US so GGoodrum will relay those to me (thanks GG ! ) and he have not received those.

I wil test those of course! :wink: .. you know me!

the idea for regen is great!.. maybe i will try that next summer. regen in winter is not very reliable!...

 

[vanilla ice]

That'd be sweet for regen. Theres gotta be a way to smooth out the braking effect at over/under v. This might cause stepiness but you could run several with different ratings to cover a wider range of voltages.

 

[flip_normal]

Ok, I just spent the Xmas fund on 24 Artesyn BXB150-48S05 5V 150W DC/DC Converters. Cost me US$360 shipped to UK from ebay (The seller says they have many in stock). This should put me on track for a 20 series single cell charger/balancer rated at ~3kW (20*150W) which is the max a single 240V 13 Amp UK socket can handle. 8)

Hopefully I (we) can manage to connect these up without letting the magic smoke out! I may well need a little help with this one. I'll have to wait to find out tho' as I've still to buy the LiFePO4 (looking to get 1.5 to 3 kWh) and I can't afford that 'till the spring.

Doctorbass wrote:
regen in winter is not very reliable!...

isn't that what those Studded Snow Tires are for??

 

[Malcolm]

Hi flip,

I'm curious. You're obviously putting together a 72V system, but a 3 kWh pack is pretty big. Is this for a motorcycle?

Those Artesyn chargers look like a really good choice to me. I'll be interested to see how they work out.

 

[flip_normal]

Hi Malcolm,

I'm planning to upgrade the moped. Picture on this page.

At the moment it's running on 48V silicone batts. I'm planning to go for 20 series LiFePO4 which should bring it up to 64V under load. It will be a squeeze to get 3kWh in there but I do have a top box I could add and I'm planning to strip it down completely, if I go for A123 M1 cells then there's lots of unused internal space where I should be able to cram in at least 1.5 kWh.

If I use the top box for the charger then that would mean I could attach/detach it as necessary.

 

[Malcolm]

Nice-looking scooter. Should make a big difference to the feel of it when you replace the lead with LiFePO4. 3kWh of A123 is around 400 cells though. Do you have some friends at a DeWalt service centre?

 

[flip_normal]

Do you have some friends at a DeWalt service centre?

Sadly not. I'm watching/waiting to see if the price and availability of quality LFP is going to improve next year.

Have you tried UK DeWalt service centres? I'm not sure what the take up for the 36V cordless is in the UK, the hammer drill kit costs £474 from Screwfix. :?

 

[Malcolm]

Yes, I've tried, but was told that they were so good that they never got any returns. It was a young lad I talked to and he was taking his job a bit too seriously methinks. I'll try again in a couple of months.

 

[flip_normal]

Me too.

 

[Doctorbass]

show them your ebike project and suggest them to try it! :wink:

After activating the throttle they usually : !!

and they return in the backstore and comeback with many deffective pack.

that worked for me! :wink:

Doc

 

[flip_normal]

Hi Doc,

Unfortunately my only ebike (apart from the moped) at the moment is a stock 24V Bliss bike like the one ES member nemo showed us a while back. I've got two Dewalt a123 packs which I'll be hooking up to it over the weekend. Nemo reported the controller could handle the 36V when he tried it tho' I seem to remember someone else saying it couldn't take it. We'll see. Either way I don't see it really wowing the guys at the service centre. My local quality hardware store which sells Dewalt tools don't even stock any of the 36V cordless stuff and I really do think too many people over here really do take their jobs way too seriously. That said I will give it a go, nothing to loose.