Build your own charger

ElectricGod

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Hi Endless-Sphere...

I thought this might interest some folks. I've built quite a few chargers and thought it was time to share my charger projects.

I want to talk about two different kinds of chargers I have built.
1. PSU only based chargers
2. PSU + DC-DC converter based chargers

PSU only based chargers have the advantage of whatever is the current output of any one of the PSU's, is what the output max current will be. If you have multiple identical PSU's and the outputs are 100% isolated from frame ground, earth ground, line an neutral, then you can "stack" them in series and get just about any voltage you can imagine. I've built 3 and 4 PSU's in series and they work fine. There is no reason you couldn't put 10 fully isolated PSU's in series. I've also used laptop power supplies and put 4 of them is series to get 81 volts. Isolated outputs are the rule!!! Decent PSU's (Meanwell) that have overload protection will cost $40-180 or more each depending on the specific voltage and amperage you are wanting. This option gets expensive quickly, but it's a great option.

PSU + DC-DC converters allows you to have an output voltage that can be adjusted a LOT. Many DC-DC converters will up convert from 24 to 90 volts out from a source voltage of 12-60 volts. As you can imagine, the DC-DC converters make for a very flexible option. You are limited by a couple of things. You can build one from a single PSU so that cost is fairly minimal and converters can be quite inexpensive. The DC-DC converter is not 100% efficient and so some of the total wattage of the PSU is used in the converter. Also to gain voltage, you lose amperage. If you are using a 24 volt, 30 amp PSU and up converting to 80 volts, don't expect to get 30 amps out. You are limited by the DC-DC converters current handling ability and the fact that you lose current to get more voltage. Transformers work the same way. In building this type of charger, I've used several converters in parallel and then doubled up the mosfets on them to enhance their individual current output to maximize the current usage of the PSU. All converters tend to be rated in watts. If you have a 500 watt converter, that means at higher output voltage you can output less current. At lower output voltage, more current all the while staying under 500 watts.

The next few posts will be specifics about PSU only chargers and PSU + DC-DC converter chargers.
 
I've built 3 PSU only chargers. This is my preferred method of building a charger for a few reasons. You get to utilize the maximum current limits of the PSU's and the only losses are from the switching power supply which can be pretty low. Also, isolated output PSU's are readily available in various voltages so creating a charger out of them is pretty straight forward and can cover a wide range of voltages and current levels. The important detail is that the outputs must be 100% isolated from the case or any of the 3 prongs coming from the outlet.

This was my first PSU based charger. It is made from 4 meanwell 30 amp, 24 volt PSU's. The output is adjustable down to about 18 volts and up to about 30 volts. As a result, each PSU is set to 20.5 volts. The fact that the PSU's are overload protected, is a really good thing. A few times, I have plugged in the charger and forgotten to open the current limiter switch and over loaded the PSU's. They just shut off harmlessly. Since input and output voltage is the same, there is no need to have a second meter on it as compared to a DC-DC converter based charger. I've been running this charger for more than a year now. The only thing I would do differently is use 6 ohm 100 watt resistors and then use 2X as many so that current load is split between more resistors so that they all stay cooler. As it is right now, the existing 3 ohm resistors get pretty hot, but they have not ever failed after many many charge cycles.

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This was my second PSU based charger. It's just 4 laptop power supplies in series and outputs 81.5 volts. From time to time, I would run low on charge on the way into work and I had this charger at work for those eventualities. Since it is 100% silent, it was perfect for an office environment. If I plugged it in when I got to work, usually by battery was fully charged 8 hours later. These are 20 volt, 9 amp power supplies. I guess I've used it 20 times or so. The individual PSU's are current limited so I didn't bother adding an external current limiter.

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This is my latest PSU based charger. I had 3 cheap 24 volt, 20 amp PSU's sitting around. I think I paid $30 each for them. They have no overload protection which means the bipolar transistors blow if you over load the PSU. I should add an inline fuses or breaker so that I can't fry anything. I've doubled up the transistors inside so that will help too. I had 50 or so 100 ohm 10 watt resistors so I attempted to use them as the current limiter, but the total resistance was still too high and they limited the output current to around 4 amps. Later I got some 8 ohm 10 watt resistors and that did the trick to get me to around 18 amps. As you can see there are quite a lot of resistors on this charger, but they barely get warm so this is a much better current limiter than in the first charger. It is set to output 65.6 volts or 16S.

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This is a couple of crappy 48 volt chargers I had laying around. both are good for 1.2 amps so I connected them in parallel to up the total output current. It works, but I have nothing that runs at 48 volts at the moment.

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This was my first few attempts at using DC-DC converters to up convert.

I scrounged a cheap ATX 350 watt power supply from an old computer and wired this up. It was good for 50 volts and about 1.5 amps. The DC-DC converters didn't have big enough heat sinks on them and they constantly got too hot and the mosfets would burn out. I replaced them and put fans on top of the converters and that helped a good bit. The small LED display is a volt meter for showing PSU output voltage. The RC watt meter measures output voltage and current loading. I forget what the wattage of these converters is, but it was something like 150 watts. The power supply was pretty small and low amperage so between the 2 converters and a weak PSU, it wasn't going to do much.

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Later, I scrounged this 500 watt ATX power supply. This isn't the final version which had 6 DC-DC converters on it. That allowed me a staggering 5 amps out at 73 volts. The fans were absolutely necessary to keep the converters cool enough to keep running.

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This was my third attempt at using DC-DC converters and was IMHO a success. I made 2 of them of which one went to a friend in California. He's been using it for about a year now. The one I built for myself worked great, but I really wanted more amperage for quicker charging and I had used an expensive PSU to build it, so I ended up pulling it apart and reusing the PSU for another charger project. The DC-DC converters are 1200 watts each and at 82 volts, that should have been something like 14 amps max, but it was more like 6 amps. I think much of the current disadvantage was due to up converting 24 volts to 82 volts or a 3.4:1 disadvantage. The fan at either end of the converters kept them cool and in the middle between the converters was a few current limiting resistors to keep charge current to a safe level. The first picture is the converter. If I ever built another converter based charger, I would double up the mosfets and then use at least an IRF4110 instead of the crappy Chinese mosfets. The irony is that the board has additional solder pads for more mosfets, but they are unpopulated. It would be easy to upgrade this converter for lots more current. These converters can adjust output voltage and do output current limiting. They also have overload protection so they shut off if load is too high. The meters worked like the previous version. Both of the converters were isolated from each other by diodes so that they could never impact each other if there was a failure.

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Please do a search for similar projects before you repeat something that may have been posted a few times previously.
There have been many threads on the sourcing, conversion, use , dangers etc etc of using PSU's, and converters as chargers.
 
Hillhater said:
Please do a search for similar projects before you repeat something that may have been posted a few times previously.
There have been many threads on the sourcing, conversion, use , dangers etc etc of using PSU's, and converters as chargers.

I think you spoke too soon. I was in the middle of posting more information when you posted prematurely. I think if you review the above additions, you will see that this is a worthwhile thread to keep. Also, I had already done a search and what I found was lots of information in lots of sources, but nothing as complete as what I intend to put together all in one place.

No one else has bothered to put together this large of a list of chargers all in one place that they built. The next step is to post up some schematics and parts lists so that more than just the finished product of my efforts can be used by others. If you look at any of my threads about specific topics, there is invariably someone else somewhere that has posted similar information. The thing is, I post nice pretty pictures, give lots of detailed steps to follow and explain what I am doing and why. If there is specific technical information that is needed, I find out what it is and post it and probably test it out too. Most threads that cover similar things don't put the level of detail into their threads that I do. This thread is partly done right now, but I haven't done the "how to" steps for them yet. You probably don't know this because most of the time new people to building EV's contact me directly with their questions. I spend a good bit of time with them on various subjects via PM and email. I invariably point them in the direction of my threads on different subjects I have worked on.

Here's my current list of "how to" threads.

My excellent adventure through some battery builds: https://endless-sphere.com/forums/viewtopic.php?f=14&t=76013
Testing Hall sensors: https://endless-sphere.com/forums/viewtopic.php?f=2&t=83802
Adding halls to motors: https://endless-sphere.com/forums/viewtopic.php?f=30&t=84112
Lightning Rods big block WYE/DELTA project: https://endless-sphere.com/forums/viewtopic.php?f=30&t=86152
Testing hall sensors: https://endless-sphere.com/forums/viewtopic.php?f=2&t=83802&hilit=hall+testing
Reinforcing motor bell to shaft on outrunners: https://endless-sphere.com/forums/viewtopic.php?f=30&t=90264
Build your own charger: https://endless-sphere.com/forums/viewtopic.php?f=14&t=90292&p=1316096#p1316096

I'm sure I will make more as I see the need.
 
sendler2112 said:
I thought that meanwells are already current limited internally. Why the resistors?

Mine are overload protected so I guess you could call that "current limited". However, when they are over loaded, they shut off. If they limited themselves to 30 amps and kept running, well that would be cool, bu they don't. IE: I needed current limiting resistors to use for the first part of the charge cycle, until total current draw without them was below 30 amps. When I reach that point, there is a small switch right next to the resistors that either bypasses or engages them, I flip the switch to bypass the resistors for the remainder of the charge cycle.

Something I have considered doing and not gotten around to doing is to build a small current sensing circuit. It would detect charge current. It is easy to figure out what amount of current draw is low enough to bypass the resistors. The circuit would look for that amount of load and bypass the resistors with some mosfets. 4 IRF4110's would do the trick for anything up to 100 volts and 30 amps. If you need more current handling, add a couple more mosfets in parallel.

This is the schematic for a board that Fecter made a while back. It would be easy to modify it for my purposes. His circuit monitors current and then lowers the output voltage of the PSU's if a threshold is reached. This effectively slows down charging and therefore current draw. It's just another way to skin the cat so to speak. I'm doing it for the entire charger and not at the individual PSU level like Fecters solution does. The end result is the same.

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Ok. Thanks. I use those (much less strenuously) in audio amp projects and always assumed they would just limit at the max current and continue operating in a constant current mode.
 
sendler2112 said:
Ok. Thanks. I use those (much less strenuously) in audio amp projects and always assumed they would just limit at the max current and continue operating in a constant current mode.

Meanwell makes various options in power supplies. It may be there is a model that does current limiting. I just know mine don't and shut off if over loaded. IE: you may not be wrong about a specific model of PSU.
 
Most Meanwells, and their various clones, LED power supplies etc, ....that i have used...all have a CC/CV output profile.
The main difference between them and a "charger" is the lack of a full power shut off at end of cycle.
They ramp down the current to a minimum preset , and then maintain it until manually powered off.
 
ElectricGod said:
Meanwell makes various options in power supplies. It may be there is a model that does current limiting.
There are some series that do, and some that just have "hiccup mode" limiting (really just overload protection), where they shut off, then turn back on, and if the load is still present, shut off, and repeat the cycle (hiccuping) until the load is removed or becomes less, enough to not trigger the overload protection.

Their main site:
http://meanwell.com
has a number of sub categories of different types of PSUs, from open-frame to weather-sealed, AC/DC, DC/DC, and DC/AC, etc.

They used to have a simple way to tell on their product listings which ones were hiccup mode and which were current-limiting but they have moved that data into the individual PDF spec sheets now. :(

These are LED supplies so they probably all have current limiting, but you'd have to look at their individual spec sheets.
http://www.meanwell.com/product/display/product.html


I like the outdoor-rated LED ones
http://www.meanwell.com/product/led/LED.html
but they're more expesnive because they are sealed and weatherproof, and significantly heavier (and unserviceable), but also are fanless even at max power. The ones I use as chargers are all limiting rather than hiccup (the HLG-600-54A, IIRC).
 
Thanks for posting this, it's nice seeing what other folks are doing and what types of products they're inventing that may not already have a good off the shelf counterpart.

Doing the current limiting resistors definitely means you're not doing a proper CC phase for the LiOns -- any thoughts on the long term effects of this?

And you've never seen any issues with doubling up (series) laptop power supplies like this? I see that as a theoretic voltage source, ok, this is feasible - but in reality?
 
My meanwells are not "hiccup" type PSU's. When they shut off, they stay off. I have to cut power to get them running again. They are 25 amp PSU's, but I regularly run them at well over that...just a tiny bit sort of 30 amps. The watt meter reads 30 amps when the PSU's kick out. I also have another of these meters on the EV and it too is reading 30 amps when the PSU's shut off. They never turn back on if they go into overload. You may have noticed that I refer to this charger as a 30 amp charger. That's because it will do 30 amps...not 25 like the label says. It's been going strong for a couple of years now. All I can say is meanwell makes solid built PSU's!

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The new Meanwell SE-600-24 PSU's arrived on Thursday. Last night I got around to putting together a new charger out of them. As expected Meanwells are well built and they held up to charging just fine. The current watt meter maxes out at 20 amps so it won't display what the actual charge current is. I'll replace it with a higher capacity meter later. This meter was sufficient for the crappy PSU's I was attempting to use previously. The charger never shut off even without the current limiters.

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I have 7 Meanwell SE-600-24 PSU's. They are rated for 24 volts, 25 amps and 600 watts. They have worked super well for a couple of years now set up as 82v (1900w) and 66v (1600w) chargers. I'm about to take them apart and get 1 more PSU so that I can make a Super Charger.

Learning the charger will be fairly straight forward for someone new.
1. Close the breaker if needed.
2. Set the current limiting for the AC circuit limits.
2. Turn on output isolation.
3. Turn off the current limiting bypass.
4. Select the correct output voltage.
5. Confirm the output voltage is correct for this EV.
6. Plug the charger into the EV.
8. Turn off output isolation.
9. Sometime later when charge current drops sufficiently, close the current bypass switch.

The Super Charger will be 8 SE-600-24 PSU's put together in a 2 wide by 4 tall "stack" or 3 wide by 3 tall stack with an open corner spot for the added hardware (switch, watt meter and resistor bank). It will be quite large, but at the same time I know that these PSU's can do just short of 30 amps or about 4200 watts at 147 volts. It will be a beast and be able to charge anything I'm likely to build.

This is the PSU on Jameco's site. They are super reliable and take over loads without damage. The output voltage is typically adjustable down to about 16 volts and up to about 30 volts. This makes them fairly ideal for the Super Charger voltage increments I will want.

https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&freeText=SE-600-24&langId=-1&storeId=10001&productId=295902&krypto=yK0Gw9oH%2BZAbBFiTrqodZOLfnCbBJgtE4nboVoli2TL4JGzPPfFPNHmm0yih1gBeTUnmwKtMEhZjQtPy8o%2Fs1XlDUGkMoHXtPU6K1RUp15o%3D&ddkey=https%3AStoreCatalogDrillDownView

There are 2 design limits that I will always need to think about: (Warning label)

1. Select the correct output voltage needed for the EV BEFORE plugging it into the charger.
2. Unplug the charger from the EV BEFORE turning off the charger.


Super Charger design goals:

1. Stack all 8 PSU's in series so I can have a maximum of 36S or 147.6v of charging ability.
2. Tap power for 12S (49.2v), 16S (65.6v), 20S (82v), 24S (98.4v), 28S (114.8v), 32S (131.2v) and 36S (147.6v).
3. Via a single rotary switch, power only the PSU's needed for a specific output voltage.
4. Via a single rotary switch, select the output voltage.
5. Via a single rotary switch, select the correct current limiting for that voltage.
6. Via a secondary switch (DPDT), select 13 amps or 28 amps out.
7. Via a secondary switch (DPDT), bypass all current limiting resistors.
8. Use a single watt meter.
9. Use a single resistor/current limiter bank that has resistances in it for each output voltage.
10. Use an AC chord with a 30amp twist lock plug. Adapt that to standard 15 amp plug for standard outlets.
11. Add a mosfet switch to the output. This provides another level of isolation between the EV and the charger in case the wrong voltage is selected. It also eliminates any current surge and spark when connecting the charger to the EV.
12. Use a master AC cut-off switch (40 amp breaker).

Numbers 2 to 5 are solved via a 4 pole, 8 position rotary switch. One position will be OFF and the other 7 for selecting the correct PSU's AC inputs, DC outputs and resistor bank.

I need a pole for applying AC to the PSU's, but I haven't worked out the exact details on how to power them incrementally yet. That's just some 40 amp TRIAC's and 8 diodes or some 150 volt mosfets. The switch pole for selecting AC power will probably never see more than .5 amps...oh well.

I need more or less resistance depending on the output voltage to limit current. I'll be buying quite a lot of 50 watt resistors soon. This will allow me to limit current to what the house circuit breaker can handle or what the PSU's can handle. In my old house, I ran a 30 amp 110v circuit just for charging at 30 amps. I may have to do something like that for the Super Charger as well. I think I will make 15 amps and 30 amps select-able so that I can plug into any standard outlet or something capable of handling what the charger can deliver.

I found a 3 pole, 8 position, 40 amp rotary switch, but nothing in 4 poles. I really only need 30 amps MAX, so the extra "beef" in the switch contacts will be a good thing. I also found a 2 pole version so I'll take it apart and add onto the 3 pole switch to get a 4th pole.

https://www.ebay.com/itm/KDH3-8-AC-380V-40A-8-Section-18P-Welding-Machine-Combination-Changeover-Switch/253065347029?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

KDH3-8%20380V%2040A%208%20position%20switch%20_.png


I'll be disassembling these chargers to reuse the PSU's. The resistors and watt meters wont get reused. Both watt meters max out at 90 volts and I really need at least a 150 volt watt meter.

This resistor bank is all 10 watt, 10 ohm resistors. It takes quite a lot of them soldered in parallel to get the current limiting right. They never warm up, but that's a lot of resistors!

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These are 3 ohm, 50 watt resistors and they get quite hot...too hot to touch. They have worked reliably since 2015 and hundreds of charge cycles. I want to use a lot more resistors to share the current load more and don't have this heating issue.

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Further design ideas:

1. Bypassing the current limiters is easy to do. Automating it is only slightly harder. Some smart watt meters support this already and provide a relay or relay control signal that can be used for this purpose. When output current drops below a threshold I want to bypass current limiting such that I always stay under 15 amps charge current. No matter what AC circuit I'm plugged into, I can't blow the breaker or overload the AC circuit. I can build this with a hall current sensor, op-amp and a few other minor parts that drive some mosfets on or off.

2. Powering off the charger at some low current limit is easy to do. When charge current drops to like .1 amps, cut AC power to the PSU's. There's no point running the charger after full charge is reached. This circuit is bypassed if output isolation is used since you can't measure charge current when there's no way to charge anything. It will also require a small secondary 5v PSU that can run all the time to power this circuit. A 2 amp USB charger would work well for enabling the mosfets or triacs. A triac or mosfet would be triggered off to cut AC right after the breaker. This would power off all the PSU's. Turning on output isolation will apply voltage to the triac/mosfet gate to turn it on again. This will then provide AC to the PSU's. The charge current sensing circuit will also reset at the same time and hold the triac/mosfet on once output isolation is turned off. I would need a hall current sensor, op-amp and a few other minor parts for this.
 
Is there a reason you want to use a giant resistor for current limiting rather than controlling the PWM in the supplies?
 
fechter said:
Is there a reason you want to use a giant resistor for current limiting rather than controlling the PWM in the supplies?

I'm assuming you are posting about the Super Charger...

Yes...this is a giant stack of PSU's...8 of them in series. Controlling PWM is something done inside each PSU and messes with the overall voltage of the entire stack. A resistor bank does not. I have a bunch of the boards you did for this sort of thing for current limiting, but chose to NOT go that route due to the added complexity and implications they create. IF I was making a single output charger, then yes tracking output voltage to charge voltage is a reasonable approach.
 
Progress...sort of...

I got the rotary switches, but they sent me the 2 pole version instead of the 3 pole version. Another switch is on it's way. This thing is huge. The mounting flange is about 2.5" x 2.5" and the switch is currently 3" long. I don't doubt it's current handling ability!

KDH2-8.jpg
 
MeanWells, typically, do have current regulation.
Unfortunately, it is at 130% of rated amps, which allows overheat and "burn up".
Adjusting to ≤ 75% of rated voltage allows continuous operation and supplies current limiting to all power supplies used in series.

Alternatively, the S-150-xxx series allows simple current and voltage regulation mods and are well documented.
S-150-xx Mods
S-350-xx similarly modable but regulation is not as "smooth", also well documented.
S-350xx Mods
Oh crap! Looks like HD pics got disappeared? Linked to full articles on ES Wiki that is down ... permanently?
Will try to repair with backup pics.
 
DrkAngel said:
MeanWells, typically, do have current regulation.
Unfortunately, it is at 130% of rated amps, which allows overheat and "burn up".
And the LED version of the Meanwell supplies have a current adjust as well.
 
Meanwell (and their cloners) makes a LOT of supplies, and they are by no means all designed the same way. Some are suitable as-is for battery charging with built in current regulation (many of the LED supplies, for example), whereas others are not, and will hiccup, shut down, or burn up, depending on the supply and the situation.

A useful thing to add to this thread would be links to other threads that cover various specific types of setups in greater detail. Reference other work and avoid duplicating it. Discuss the alternate methods of regulating the supplies, and how the resistor technique is simpler but wastes energy. In today's green environment it would be important to show how much energy is lost in the resistors.

Here's one of my charger threads utilizing the LED supplies: https://endless-sphere.com/forums/viewtopic.php?t=42169

There are also some threads on bad-boy chargers, the ultimate in simplicity. :)
 
There are many Meanwell modification threads. It would be nice to have a page of links to them all. Even for a given model number, there are different versions of layout depending on when it was made. I have mod diagrams for many of them.
 
All good points...of course I already have 7 of the SE-600 series so guess what I'm going to use?

It would be cool to have adjustable current limiting. I would use it if did something other than just shut off the PSU's. If it really limited current to 25 amps and never allowed more than that...well that would be pretty nice! But the SE-600's don't seem to work that way. Go over current and they shut off instead. Oh well...at least nothing burns out.

I had several clone meanwells...4 to be exact...absolute garbage! They looked like my legit SE-600's, but came from China. They were rated for 25 amps and burned out at more than 10 amps. I got my money back!

Buy real meanwell PSU's or just don't bother.
 
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