Modified HP194989-001 PSU's for series 24v ++ lipo charging

Please forgive my quoting myself. I just thought it would be best to replace this thread from its initial location with a title which better reflects the progress and specific needs of my project.

whereswally606 said:

To aid in helping me to do this ive opened up one of the powersupplies to take a few snaps so that the DC ground isolation method can be better shown. If you have done this before please show me your pictures or anotate mine.

All the pictures were taken and resized to 600 pixels to help uploading hope that they are clear enough.

Thanks to anyone in advance for help on this.

Click to expand...

The original thread is here.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=33551

There are 4 screws that fasten the PCB to the chassis. Isolating the 2 (nearest the fan) from the board should provide the DC isolation you are seeking. When done, be sure to check with multimeter to verify isolation!

Thanks Psycholist, you were half right exactly. I took apart on of the power supplies last night after doing the 2nd interlock solderings, Now they both output 12V. There was no need to connect together all 4 grounds cause they are interconnected anyway tested with a continuity multimeter setting. BUT the DC ground goes through all 4 screws connecting the PCB to the case. I basically cut some bit of rubber ie an eraser into 4 small pieces. Then used 8 cable ties instead of 4 metal screws to hold down the pcb inside the PSU. tested the 2 series'd supplie last night and was getting 24.24volts DC on my GT powermeter. Now im thinking about a bulk charger since ive got a proof of concept. But also need to look into some methods boards for my converted 3s to 6s zippys.

all made my own phat wire from copper speaker cable for the job. this was way more trouble than it was worth and im knackered after my very over busy weekend. had a theory about soldering bullet connectors which is that a syringe or vacuum pump might be a very useful tool.

Anyway in summary thanks for the help Psycholist and GaryJS Its a win for these power supplies.

whereswally, Without the paralleled grounds, you may experience voltage sag under load.

I was thinking the a/c and d/c grounds were separately isolated on the board, thereby only needing to isolate the 2 screws.
Thanks for verifying that they are not.

I was going to suggest plastic screws and washers for isolating, but enjoy learning from other's creative ideas?
Cable ties and erasers--I like it Pics please!

Not sure if I understand you correctly, but you cannot use this PSU as bulk charger, as it is not current limiting.
That requires something like a Meanwell.

Congrats on a successful mod! Keep us posted on how it performs under load.

Sorry Psycholist, was going to do some photos when doing the mods but it was late at night and the girlfriend was getting silently more and more peeved at my tinkering and I just wanted to get it finished. Now they are reboxed and the ungrounded one is wrapped in red leccy tape the grounded in black and they are both physically isolated temporarily using cardboard (idea from TJinDC) and its what i had to hand.

Wondering about the current limiting idea cause first i didnt know it was an issue. could fecters boards for the meanwells be modified to work with these? anyway perhaps i should ask him.

They are currently in manchester and im stuck in Bangor, wales during the week as im at uni there. Can actually wait to get some real time to finish off my 2nd bike, a norco team race with a huatong 72v controller. Going to go look up meanwell limiting now cause where there is a will there is a way.

wally, I just isolated mine last night. I used your cable tie idea (worked great! thanks!), and made some plastic washers.
I only needed to isolate the 2 screws I suggested previously. Don't understand why yours would be different.
Sorry, haven't looked into any current limiting mods. I think I'll be getting a Hyperion 1420i.

Have you seen the good website with instructions for putting PSUs in series? He uses two similar server supplies, isolating AC ground and DC ground between the two.


I cant find it right now, but if you don't know what I'm talking about- I'll look for it again in the morning? It seemed useful to me, but maybe you're beyond that level.

Tjintech does a great website, but I think I've exhausted the knowledge for my problem there as I emailed him directly. Aura slips site is really useful too.

Ac isolation is not necessary and is a bad idea. Don't want 230 volts mains floating on the case

Hmm, he installed a neon lightbulb to be able to see if the case was charged suddenly.

I think he chose AC isolation because is was the easier method of a few possible options. I now assume you know the website, since you refer to a few (it was very neatly written and presented).

So this weekend I finally go these PSU's charging my lipo via a hyperion net3 chargers 12s at a time. Had 16 3s packs zippy flight max 40C 4aH batterys. made a vid on my iphone will upload to here later. each set of 4 took 30mins except for one, my 10th pack which was in string 9 10 11 12 caused the charge to last about 80 mins. From this i expected I had a problem and so checked at the cell level and the last cell in battery 10 wouldnt charge over 3.91 volts whereas the other two happilly sat at 4.2volts.

I have filled in a warranty form with hobby king but it appears i have to send it back to china which i estimate 3 weeks min to get there and then they decide whether its broke and replace or not. Problem is my charging setup was not working till this weekend so i am probably outside of the warranty period. Will try to contact their help desk today but im not holding my breath. Out of the 16 batteries only having one duffer feels like ive faired the lipo lottery ok. Its a bit frustrating as i had more options with the extra pack than i do without it. guess i should have ordered overs just in case.

any suggestions on what is wrong with this pack? visibly there were no defects.

OK so just bought 18 more PSUs.

My aim build two bulk chargers 8 x psu for 24s charging.
or
three 6 x psu for 18s
or
four 4 x psu for 12s

plus they are hotswapable and its nice to have spares.

I have a plan for an adapter to quickly ground the correct pins instead of lots of soldering.

need now to source some meanwell type chargers for the current limiting.

My plan is keep the bulky server PSU at my main charge places (ie start and end of commute) and carry the more expensive current limiting charger with me. since i cant afford many meanwells.

after spending 2 hrs min on the balance charge i think that the sooner i get this bulk charging understood and functioning then the more sensible my charging situation will be.

Thanks to cohberg for his reply in his genesis thread.
Really need to look into other safeties like methods kit.

[youtube]NY9HLpwOrFY[/youtube]

just to show the progress and spark some interest I thought Id show a quick video. Probably nothing somebody hasnt done before but its still progress for me and I hope it helps someone else out. please check out my other thread to get these server supplies to bulk charge.

http://endless-sphere.com/forums/viewtopic.php?f=2&t=37296

and here is a snapshot of how im thinking of modifying the rest for bulk charging



if you are wondering why etch the pcb, that was my first idea, though annoyingly you need to apply too much pressure to hold the pcbs together to get a good enough electrical connection. Since i had the pcb etched and it provided a good no wire solution i used it anyway.



this is the reverse which shows a nice glowing green led to show 12v out.