Bulk Charging ...

[OCMike]

Hello ... long time ... cheers everyone

I have 3 old laptop power supplies. Each one is approximately ~20V and they range in amps from 4 to 6. I'm thinking to cut the cord to the laptop connector and wire them in series. This would give me ~60V at ~5amps I think?? I run 15 cell lipo for my e-bike.

Is this a good idea? Or is there some danger I'm not aware of?

I'm no electrical guy - I'm just a guy fiddling around with stuff - but I don't want to burn my house down or electricute(sp) myself!

I'll monitor the cells of the 15 cell battery while charging to make sure the balance doesn't get wacky.

Thank You

 

[Skalabala]

Yes it will work. Does your battery pack have a BMS?

 

[OCMike]

Yes it will work. Does your battery pack have a BMS?

No BMS. I just do it manually. I have a volt meter on my bike. Until now, or after I put this bulk charger together, I balance charge every time I charge. I prefer to not let my resting voltage drop below 54V (3.6v per cell) before I recharge. I always store my batts at 3.85V per cell. I frequently use voltage checkers. I will attach voltage checkers to the balance leads of every battery undergoing a bulk charge - I will also monitor. All my batts are zippy 8amp batts. I have 6 six cell zippy's and 3 three cell zippy's in my collection of batteries.

Thanks for you reply - any concerns with what I just explained?

 

[Ykick]

I've assembled bulk charging power supplies like that in a pinch. I currently have a 48V Meanwell and a 12V Meanwell series wired delivering 66.5V for 16S RC Lipo. I never, ever initiate a charge without 1st confirming supply voltage and checking each cell to be sure nothing is too wonky. And on top of that - 'don't leave the room until finished.

Knowing your cells is more important than you can ever imagine and learning IR and capacity testing will help. This can be very dangerous method of charge, be very careful or look into the charge BMS stuff.

 

[OCMike]

Thanks Ykick.

My understanding of IR is that when IR of a particular cell is high that cells voltage will go up quicker - so that cell must be monitored even more than other cells.

I like this bulk charger because I can actually carry it with the bike. My range with my 15S2P is about 35 miles. It would be GREAT to be able to re-charge at destination. I can easily carry this bulk charger and several cell checkers with me on the bike.

Heck, I even have the ability to discharge a single cell if needed (as long as I remember to bring that equipment with me - a paraelling balance lead with andersons on one side and some christmas icicle lights.

Thanks for the warning! I'm a strong believer in "you can't be too careful". Because, for me, even as careful as I am, I still F up once in a while.

 

[mcintyretj]

Good to see you Mike,

I have had trouble paralleling as well as serializing laptop power supplies, one always seems to shut off. I know that a diode can fix a paralleled shutoff. Not sure about series setups. Here is a failed setup.



One power supply is off but the green LED is powered by the one working supply. When in series, one shuts off so these will not work as is for a 60v setup.

You can get a cheap power supply on ebay or aliexpress. I might get this one:

http://www.aliexpress.com/item/400W-60V-6-6A-Single-Output-Switching-power-supply-AC-to-DC-SMPS-CNC/1667637251.html

I have several broken chargers and one simi-working power supply you are welcome to if you want to ride over this summer.

Bulk charging works well for me. The more plugging and un-plugging, (black to red, red to red, black to black) the more chances you will make a mistake.

 

[OCMike]

Thanks TJ!

Wow - that seems like a really good price for a 60V power supply. I may have to pick one up just because!

I'll series the laptop power supplies I have and see what happens ... seems like it will work ... I hope any of the three don't switch off by itself.

Riding up to your place sounds like a good plan.

Cheers.

 

[dnmun]

Hello ... long time ... cheers everyone

I have 3 old laptop power supplies. Each one is approximately ~20V and they range in amps from 4 to 6. I'm thinking to cut the cord to the laptop connector and wire them in series. This would give me ~60V at ~5amps I think?? I run 15 cell lipo for my e-bike.

Is this a good idea? Or is there some danger I'm not aware of?

I'm no electrical guy - I'm just a guy fiddling around with stuff - but I don't want to burn my house down or electricute(sp) myself!

I'll monitor the cells of the 15 cell battery while charging to make sure the balance doesn't get wacky.

Thank You

yes there can be a problem. the earth ground of the power supply may be tied to the negative output of the charger. or power supply. using approximate numbers for voltage is cause for concern. it indicates there is a much better chance of you having a short by poor execution than from overvolting though. all the lipo fires so far we have had reported here were caused by shorts. except for floont. he used power supplies in series without a BMS to charge his home made lipo pack too. we never heard from him again so no way to know what caused his fire. or ZapPat either.

 

[OCMike]

Thanks for the replies!

Thanks dmnum. It was silly of me to use approximate numbers for voltage. 2 of the power supplies are 19.5V @ ~4.5 amps and the other is 20V @ ~3.3 amps. I think what I could expect from that is 59V @ ~3.3 amps. But like you alluded to - there are things I just don't understand well enough to be tinkering like this! Result: Scrap idea!

Thanks Ykick. Verifying output voltage each and every time of use seems like a GREAT idea! I know TJ puts a volt meter in line with his bulk charger - I think that's important too in that (I think) if the voltage on the volt meter drops below the battery pack voltage at time of connection, that indicates at least one of the power supplies has switched off and you're now draining your battery pack. Is that correct?

Thanks TJ. That price for a 60V power supply is awesome! Makes my choice EASY! Hopefully power supplies travel well? I don't think my balance charger would travel well and it's too expensive to be replacing on a whim. I'll probably just monitor voltage at the cell level with cell checkers on all batteries undergoing bulk charge. That's actually probably more safe than monitoring battery pack voltage even though it's a little more time consuming. I'll just stop charging whenever one of the cells reaches 4.1V.

As an aside - I like the extra power I get by running 15S. I don't like having a balance charger only capable of balance charging a 12 cell battery. Even with 15S it's still not quick but it is fast ~37mph when fully charged. Another thing I'm not liking is not having disc brakes! I think 37mph is tooooo fast for a bicycle but 25 mph is not too fast - and brake failure would just SUCK!

Thanks all!

 

[dnmun]

i have a 15S D126 lipo BMS that you can use a 48V lifepo4 charger with to charge to 63V. it will pull 22A for a relatively long period, rated at 15A continuous and 25A surge. i did burn one up at 25A continuous and then rebuilt the output mosfets by adding 3 more so it will now handle 30A continuous. no longer using it if you are interested in it and a charger.

 

[OCMike]

I decided on 5 of these:

http://www.amazon.com/gp/product/B003TUMDWG/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1

Don't have to worry about one switching off as they're just always on. I'm also having fun with LED lights around the house - so these actually serve an additional purpose. That's pretty cool!

Cheers

 

[Ykick]

Please update how those work, isolated, etc? If they're anywhere close to 5-6A output that's only $40 shipped for 60V using Amazon Prime. Hmm?

Gonna guess unloaded voltage will be closer to 15V than 12V but with a little fussing around (or BMS) they could be useful for bulk charging.

 

[OCMike]

Power supplies in hand

They're kind of smaller than I expected ... but that's good with regard to carrying them with me on the bike.

I have a watt meter. I've only tested one. It draws 0.4 watts just plugged in with no load .

Here's a pic of my volt meter testing the voltage:



12.62 volts unloaded. I didn't even think loaded vs. unloaded until you said something Ykick.

I will test the voltage of each power supply individually before hooking them in series. I expect, in the end, to get 12.62v * 5 = 63.1v as a bulk charger. I will also check the polarity of each one before attaching them in series together. This is likely not necessary but I imagine over time everything happens and I don't want it to happen to me! It being that for some reason red is negative and black is positive on one of them <--- assuming output wires are red and black.

My plan is to cut the output wire and put andersons on both sides. That way I can reconnect the stock connector and use them to power LED's whenever I need/want to. But where should I cut the output lead? There's a round cylinder thing in the output wire between the power supply box and the output connector - here's a close up pic of what I'm talking about:



Anyone know what that is and what it's purpose is? Should I cut between the black cylinder and the output connector OR between the power supply box and the black cylinder? There's not much wire between the output connector and the black cylinder - you can see this in the first pic.

Or should my plan be to NOT cut anything and buy female connectors to attach to the male output connector and attach andersons to the other side of the newly purchased female connectors? May be the power supplies don't even have two wires inside the output wire - maybe negative is carried by a wire mesh which surrounds an insulated positive wire - if that's the case buying female connectors is obviously the way to go.

Any input from you guys would be appreciated.

Thanks!

 

[cal3thousand]

That thing is a ferrite. It cuts out the electric interference using a magnet.

I would cut it between the ferrite and the connector, keeping it in the circuit to cut noise out.

 

[dnmun]

did you think of what will happen if one of the chargers shorts out while attached to the battery?

 

[OCMike]

Thanks cal3thousand ... That's what I'll do ... I've done one so far No rush here.

dnmun ... that's a good question. No, I didn't think about it until now. Can that be simulated by simply unplugging one of power supplies during charge? I think the charge process would just halt? I wouldn't expect the battery to start draining. My plan is to keep watch over the cell voltages by keeping cell voltage checkers attached to the balance leads during bulk charge and staying on top of it. The whole thing should be about 360 watts. I'm certainly not thinking instant disaster will ensue should that happen. I'm really not sure how long the bulk charge will take. The plan is to stop bulk charge when any one cell reaches 4.1 volts. I always stop using battery power on the bike when average cell voltage is at 3.6v under no load. I think 3.6 volts is well above any danger level. If cell voltage starts to drop during bulk charge, I'll take that as a sign that something is wrong ... and halt the process.

Seems like it should work OK? But I'm interested in what you all think about the idea and what I should look for. Both in setup - what should I check before connecting everything and turning the power on? - and during charge - what should I look for as a sign that the process is going wrong?

My balance charger gives me IR for each cell so I know my batts are healthy. I have a good balance charger so I plan to balance charge somewhat frequently even though it's a pain because my balance charger does only 12 cell batts max - so I have to disassemble and do 12 cells and then 3 cells and then reassemble the 15 cell battery.

Essentially bulk charging will allow me to ride 40 miles to a friends house and bring the bulk charger with me to charge while I'm there so I can ride home with battery power.

Thanks!

 

[dnmun]

use fuses for sure in the charging leads, at least next to one end or the other.

 

[OCMike]

Sort of a plea for input

I think everyone here enjoys being helpful - and that's always a two way street - you just never know what somebody's going to think of. I also think it's natural for us to point out problems others haven't thought of. It's just human nature for some reason - I do it too - somehow I just love to explain.

But I also think I've noticed that people are a little reserved here and I think that stems from the fact that what we do is both deceptively complicated and dangerous. I mean it's really easy to know enough to be dangerous - to ourselves and others. I would hate to hear that disaster occurred to somebody I gave advice to. I assume you all are the same.

I just want you all to know that I own my actions. I also know I know enough to be dangerous AND I don't know enough - knowing enough takes years and years - it's just not easy. The learn never stops. I make every attempt to think critically about what I'm doing before I do it - that doesn't mean I'm immune to making mistakes. But it does mean I'm constantly trying to learn and when I do make a mistake I REALLY REALLY want to figure out what happened - I'm not apt to just let it go as some anomaly.

With that said please jump on anything that concerns you, the reader of this thread, about what I'm doing. The more information I have the better equipped I am to stay safe. I'll always seek clarification when I don't understand. And when my understanding is in conflict with observed reality, I'll seek a better understanding.

Thanks! I really do appreciate you all. I wish I could contribute more - but I'm, more often than not, just the seeing impaired leading the blind when I try to help.

 

[OCMike]

use fuses for sure in the charging leads, at least next to one end or the other.

Thanks. I think of fuses as surge protectors. I'm not sure what fuses would be protecting against in this situation. I know I'm just a numbskull with regard to this - fuses probably serve a multitude of functions.

I could see installing something that ensure electricity flows in one direction only - is that what a diode does? Should I just be scrapping the whole idea?

Sitting here thinking about this post before I submit. Now I see - a short, by definition, creates free flow of electricity. Putting a 7 amp fuse on one end of the bulk charger would ensure the battery doesn't just discharge should a short occur. I think that's right? Would it be better to put a one way only circuit in-line? That's probably the beginnings of a BMS I guess?

The power supplies have a CE emblem on them. Doesn't that mean they meet some sort of safety standard - like shutting down on short?

Thanks ...

 

[dnmun]

i still do not have a clue why you decided to do this though. why you did not just use a regular charger so you can set the output voltage and have a charger that would last a long time and operate efficiently too.

 

[OCMike]

I think there's just more than one way to skin a cat. And we all skin cats from within our comfort level and do it the way we want to. I don't know what's best.

I know there are lengthy BMS vs no BMS debates here. Part of what I enjoy is being the BMS and my e-bike is for pleasure only. I use my car for most of my travel activities.

I also know that power supplies and charging are an issue for all of us. And many people just want to plug it in and forget about it. That's probably a smarter way of doing it. But it eliminates a large part of the pleasure I get from fiddling with this stuff.

It's cool to have an idea, execute the idea, and then watch it work. And then you get to refine your idea and make it better - version1, version2, version3, etc. I think maybe 7 amp fuses between all power supplies and one on either end is a good idea - after all I am using these power supplies in a way that is likely not within the scope of their intended use.

Thanks!

 

[cal3thousand]

I think there's just more than one way to skin a cat. And we all skin cats from within our comfort level and do it the way we want to. I don't know what's best.

I know there are lengthy BMS vs no BMS debates here. Part of what I enjoy is being the BMS and my e-bike is for pleasure only. I use my car for most of my travel activities.

I also know that power supplies and charging are an issue for all of us. And many people just want to plug it in and forget about it. That's probably a smarter way of doing it. But it eliminates a large part of the pleasure I get from fiddling with this stuff.

It's cool to have an idea, execute the idea, and then watch it work. And then you get to refine your idea and make it better - version1, version2, version3, etc. I think maybe 7 amp fuses between all power supplies and one on either end is a good idea - after all I am using these power supplies in a way that is likely not within the scope of their intended use.

Thanks!

I really don't know why you're doing it, but I really don't care why. That's not my business. I'm here to learn and help if I can.

Keep it up dude. And if you make a mistake, hopefully (you and) someone else can learn from that. I think that's the reason to this board, no? :wink:

 

[Ykick]

Sure, it's probably a convoluted scheme but not if you've blown-up a "real" charger and need to McGyver something to keep rolling until replacement can be found. That's where I've done this before. Cobbling a bunch of various supplies together.

12.6V will always come in handy someplace. You could run a small RC Charger off that too?

Don't need to explain to me. As long as a man uses good judgement and respects the life & property of others' I don't give a shit "why" you may or may not do something. If you enjoy it, DO IT...

I do all of this because I basically love to RIDE. Staying a little up on the tech keeps me up on 2 wheels. Good luck...

 

[OCMike]

Sadness ensues

I put andersons on my third power supply and decided to bulk charge one of my 3 cell zippy 8ah lipos. It started at 3.81v, 3.82v, and 3.83v. When I connected the charger which tested at 12.45v, the cells jumped to 3.85v, 3.86v, and 3.86v. It charged for about two minutes and the cells went up to 3.87v, 3.88v, and 3.88v. Then I heard a little pop and all cells were at 3.83v. The light on the power supply was still illuminated. I sat there and looked at it for a couple minutes with confusion in my brain. Then I decided to unplug the lipo from the power supply. When I did, the power supply light went out - the charger was still plugged into the house AC - and I saddened a little more. The power supply was hot but not too hot. I tested the power supply with my multi-meter - 0.00v ... CRAP! I guess it's not going to work

Anyone have an idea of what happened? I want to crack the power supply open and look inside. But I'm pretty sure I'd just be looking inside the black box and have no idea what I'm looking at - may as well still be an opaque black box when I look inside.

But I'd like to fix the one that failed ... I'm sure it can be fixed by somebody with skill ... not me with my current knowledge base right now though

Damn safety features - getting in the way of me doing what I want to do! Or may be saving my life and/or the integrity of my dwelling?

Luckily I do have another use for the power supplies - they power my LED light strips .

 

[dnmun]

so that is the reason. the pop may have been a fuse inside the charger so look under the feet to see if there are screws to open the case and see. do you have a voltmeter? know how to use an ohmeter to measure continuity?