Lipo bulk charger not stopping. (help)

[saiyan]

hey guys,
Need a lil help here. i purchased a bms charger not too long ago and now it doesnt stop charging until i pull the plug.
this is what happend. couple weeks back when i was charging as per usual, just b4 the charger would stop by itself i would disconnect the battery as i did not want it to charge anymore. instead of letting it charge all my cells to 4.2v each, id disconnect it at bout 4.18 or so...
now what happend was when i disconnected it, it made a loud hissing noise......

i didnt know what it was so i just switched it off....
next day came to charging again i turned the charger on and the hissing noise was still there. didnt think much of it, i tried to plug the battery in, as soon as it connected it made a loud pop and i new something had blown. after that day it doesnt slow down or stop charging anymore.

my guess would be the part that blew was the thing that slows the charging down and to a stop.
my being noobness i do not know what that part is called nor do i know what it is. if some1 can point me in the right direction, maybe i can buy it and replace it.

btw, its a 20s lipo bulk charger from bms battery. this is my 2nd charger from them as the 1st 1 blew up and didnt even work at the start. :/

cheers

bruce

 

[dnmun]

can you open the charger and take pictures of the inside. is it possible the hissing sounds was similar to the sounds an electric arc welder would make while welding? was there a burning smell when it stopped?

 

[saiyan]

i havent opened the charger yet cause im still using my ebike to get to work....
will open it up soon though......i get a little nervous each time i charge when i charge. even though i have 2 alarms to remind me.......
with the hissing sound, it was pretty loud and distinct at the time. i dunno if it sounds like an arc welder. :0
hissing is no longer there, after the part blew.....

 

[saiyan]

ok guys, i opened it up and found the problem.
can some1 please tell me exacty what this is and where to get it?
i couldnt find it at the electronics warehouse near my area.
the guy said it was 300v, 6amps?

 

[dnmun]

you checked the diode forward bias from both sides and it was shorted?

there are lots of diodes you can choose from. what voltage do you charge to and how much current does your charger push?

are you sure this is the problem or did it blow up along with the part that was hissing? if this schottky diode had blown up then it would not work as a charger and you said it would not stop charging.

 

[saiyan]

i have just googled the part no. came up as an "ultra fast rectifier diode."

once i pulled the diode out i tried to charge it again. with the diode out the light on the charger keeps alternating green and red every 30 secs or so. so now it doesnt really charge anymore.

like i said before it would not stop charging.....even as the cells are almost at peak it did not slow down as it should.

this was the only part that blew in the charger. you can see in the pics and a piece of it blew off.
my charger is for a 20s lipo charger. 75v nominal at 84v max charge at 9 amps

im pretty confident that this is the cause of my charger not working problem.
ive already ordered a replacement part for it. though im not exactly sure if it will work. cause its not the exact same thing.
guess we will find out when it arrives. lol

no more chargers from the bms batterys guys....... this is my 2nd charger from them. 1st 1 i plugged it in a it blew straight away. :/

 

[heathyoung]

Yep they are garbage chargers unfortunatly - poorly designed, I have fixed a few, fixed one recently, and it worked for about 10 minutes, made a strange noise and a capacitor turned itself inside out. That one hit the bin (I was working on something else next to it and it startled the crap out of me).

The idea of a bulk charger is that its open circuit voltage is the voltage you wish to terminate at.

So you need to adjust its output to the 20S termination voltage ie. 83V if you charge to 4.15V per cell. If it is higher, it will keep charging to its open circuit voltage. This is a bad thing.

The purpose of the shottky diode on these is to rectify the output of the transformer - so they are a pretty neccesary part. If it was rated at 6A, it is under specced!

 

[dnmun]

nope, it is a 600V 20A Sanken product:

http://www.datasheetcatalog.org/datasheet/Sanken/mXwqzxx.pdf

what did you order to replace it with and from where?

 

[amberwolf]

Another thing that could be failed is a capacitor. Hissing could be venting from one. If one failed that should be smoothing spikes on that diode's circuit, perhaps it began getting spikes higher than it's rated voltage, which took it out.

So you may want to check out all the electrolytic caps in that end of the charger.

 

[saiyan]

i ordered a 16amp 600v fast recovery rectifier diode.....ordered it off ebay.
with regards to the charger itself. i opened it up having no clue what is what. i still dont know all the techy stuff.
i just find what is broken and try to replace it with something else...lol

lets just hope its the diode in the end. cause if its not, looks like another charger in the bin. :/

thanks for the help guys, much appreciated once again.

 

[heathyoung]

Good luck - I collect these for bits, happy to pay postage if its getting binned - only in Newcastle.

 

[dnmun]

that will work, i figured you could use a lower voltage even, i have seen 60V schottky diodes on some lower voltage chargers. but i realize now that the reason they want the ultra fast action is to reduce the forward current spike that heats up the diode. so that is why they put the big choke on the output from the schottky diode.

and the snubber eats up the high frequency ringing from the switching of the diode. i could see how the big low value resistor in series with the capacitor across the diode will just eat up the noise. they seem to get hotter on some chargers than on others too and i wondered if that has something to do with how fast the diode is.

 

[shock]

My solution would be to throw the BMS charger in the garbage, or perhaps use it for target practice and buy myself a good LiPo balance charger

 

[saiyan]

hheheeh will keep you posted with the charger.....

i have a turnigy lipo charger already as i am into rc cars. but charging 20s3p on that takes a while.
thats what im doing now since i gotta wait for the diode to arrive maybe in a couple weeks.

ive got 12, 5000mah, 5s batterys on the bike. and 8 of them are right under my sack. ive always wondered how fast id have to jump off if 1 were to fail on me, lol.

does any1 know where to get quality bulk chargers? not that im going to buy anytime soon since i will be selling my bike and building a 25kw ebike. but just for future reference so i know where to look.

 

[dnmun]

you only really have to worry about them shorting on you, from ian's experience i may take a few minutes even if that happens. but arrange the pack so you can take it apart in a hurry to protect the other packs.

but you could use a combination of bulk charger and balance charger.

the bulk charger to fill the pack and the balance charger would be adding charge during this period too but you could even turn off the bulk charger when the balancing charger finally got to full voltage on one cell.

there are opto triacs you could use for the AC power on the bulk charger. take a signal off the balance charger to drive the opto and after the bulk charger is turned off then the balance charger can finish.

 

[heathyoung]

A serious bulk charger? Stay away from the likes of BMS battery and such.

Chennic / Elcon are proper chargers that are made to be mobile and last. If you want to go the DIY and cheap route with some serious power, you can't go past server power supplies. I figured out how to make a 24V, 40A charger, but you could scale this to 84V @ 40A if you had three phase power. Even at 25-30A, that isn't exactly a slouch.

Makes a good stationary charger, too bulky to be mobile.

 

[saiyan]

That sounds very interesting. Server poeer supplys. U definitely gotta show me how to do that some time.
My next build will have 40ah of battery power so a 20-30 amp 72v charger would b awsome.......

 

[dnmun]

found this ebay source too for 200V 20A diode, cheapest i could find, but there are some on mouser for less except shipping costs a lot from mouser:

http://www.ebay.com/itm/251125884772?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

 

[Gregor]

I'm sure this has been covered in other threads, but can server power supplies or meanwell power supplies be used in series (eg. a 48v and a 36v to get 84v)? I would assume that you could split up the battery into the 36 and 48v segments and do it that way, but could you do it just as a 84v bulk charge?

 

[heathyoung]

Yep series is fine. Current limiting these supplies gets complicated though, as a few people have found the meanwells have a safe voltage window - out of that, they get unstable and die.

The server power supplies are all put in series, and they all are voltage controlled at a single point. I use this to charge a 48V pack as 2 24V packs @ 40A (until I smoked the charge mosfet - oops)

 

[dnmun]

you can hook them in series, but the power supply may stutter when pushing the maximum current. they call it hiccup mode, so you have to do something to control the current. i use a charger in series with a meanwell clone. to get 80.6V i use a 48v clone set to 53V and the charger puts out the rest, 27.6V. the charger has built in current regulation so the power supply cannot be asked for more than the charger will allow to flow. i did adjust it up from 4 amps to 6.5A though since the power supply was 350W so it could produce almost 7A at the 53V. it really worked out well, i bolted the charger to the top of the power supply and made the wiring connections internal in the charger so that i have the regular charging cord going out to the BMS.

 

[heathyoung]

The server power supplies I used just shut down and need to be power cycled if you don't current limit them somehow. Main problem is you need to be able to adjust the output voltage to adjust the current, so you need the range to do this. I get the range through controlling all of the supplies together (ie. they are all producing 10V if I need 20V, or 11V if 22 and so on). A single supply can be used, but it needs a high level of adjustability, and the meanwells (unless you use higher voltage ones) just don't have it.

Main problem is that forward converters have a narrow efficiency window - buck converters don't, but they are not isolated and so are no suitable for mains connection where you may contact the battery terminals or the battery is not floated - they negative reference is actually at half rectified mains potential (ouch!).

 

[dnmun]

yep, my meanwell clone will only go from 42 to 54V. the charger is a 24V kingpan charger so i could adjust the voltage down a little to make it work, which gave me more space to push the current up since it is normally a 4A charger and i pushed it to 6.5A. i think it is a better way to do it than using the feedback circuit to the power supply to limit the current.

 

[diggler]

Have any of you guy's looked at these? http://www.ebay.com/itm/NEW-500W-0-80VDC-Output-Adjustable-Switching-Power-Supply-CNC-WITH-CE/171801553780?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3D4f20a319f77d4175988e69d9e83f61e1%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D171791276753&rt=nc
I think they're new to the market and the company is making in 500, 800, 1000 watts. You can get them 0 to whatever voltage you want, adjustable, but the current is not adjustable. I originally wanted the 500w 0-120v one, but the seller said the max amp output is only 4 amps, witch at 120v is not even the full 500w.
So when I'm charging my 15s lipo this will only do 250w.
I have a 15s system and a 18s right now, but will soon be playing with 21s and 24s. And eventually go up to 28s.
What I needs is a 1500w 60-120v 0-20amp adjustable, portable bulk charger, without having to concoct something out of a bunch of server power supplies and a meanwell or whatever.

Any thoughts?

I'm just brain storming.
I know what I want just doesn't exist right now, but just trying to find anything close.

I talked to bms battery.
I wanted to order a 900w charger at 117v-?amps. Then get 2 of them because I know they only really put out about 750w.
I asked them to tell me which pots did what and if they would use better fets so the charger could put out more current when I adjusted the volts down to 62. But they simply just told me the charger is not adjustable.
I'd like to order one anyway and just play with it but the shipping is highway robbery!

Idk most likely I'll just get one from that ebay seller. The 800w 0-80v will probably do at least 9 amps, and that good enough.
Then I'll just have to get two for when I go higher than 18s lipo.

Maybe I can get them to make me a 1500w 0-120v one I'd be happy with 12 amps max charge all the way down.