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Hey you know what time it is yeah. Let's talk about batteries. Well, actually, not batteries, but power supplies. Let's talk about variable power supplies and why you should have one if you're messing around with batteries, sometimes when you're harvesting cells, either from a scooter pack sort of like this one here or a medical pack sort of like this one here or the modem packs.

Sometimes you're gon na get cells that are low, voltage right that are like at one volt or below two and a half volts or something, and so you could do one of two things you could put them aside and then try to see if you can recover Them right, so, if you can slowly charge them back up, if they haven't spent a lot of time down there in the low voltage region, a lot of these batteries will just wake up and they just you, there's nothing wrong with them right. They didn't degrade enough for them for you to be considered them useless right now. You have the choice to do that or you have a choice to just you know: get rid of them, not use them, not attempt to salvage them, and - and i wouldn't fault anyone for taking one of those decisions right. But if you want to check them, then you're going to need a way to slowly bring those cells back up.

Here's another scenario - and i will use this one as uh as a prime example of why you also need to do this. This battery is made out of brand new cells lg m36s right, so these are really expensive. Batteries really cool. There are 3 500 milliamp hours, so they have a lot of energy density in them.

So i built this battery to use it for a video as a demonstration, and then i just forgot about it. I just you know, i'm busy life, you know other videos, other projects and that thing just sat there, but the mistake that i did. I left the bms connected right, so the bms is there see those lights so that screen uses energy and it just drove the battery low, and so this brand new this this battery pack with brand new cells right now, is sitting at a low state of voltage. I just measured it and it has eight volts in here right.

So that is another reason. Sometimes you might want to try to bring up a battery pack, because it's brand new and you spend quite a bit of money and work and effort to get it there. But you made a mistake or you were careless and you just let it get below the safe voltage right now. If it didn't spend a lot of time down there or if it got there really slow, then sometimes this batteries are recoverable without much um.

You know without without much degradation. Another reason why you might want to get a variable power supply is because, even if you have the charger, some of these chargers come in a variety of uh voltages and the way they do that is sometimes they'll detect. They have a range of voltage right. Uh, like the 12 volt it'll, be like from 10 to 13 right.

But if it's below that, then, if this charger will not come on and it will not start charging your 12 volt battery, if it's below you know 20 volts for a 24 volt or something like that, maybe this will not trigger on and so even though you Have the the charger to to save this battery right because you just forgot last night or you know a few days ago to turn off the thing and you let this discharge over discharge, then you know that you can bring it up, but maybe your equipment, your Charger that you usually use to charge that battery will not work, and so those are scenarios why you need a variable voltage power supply. These are you know these are the new breed of them, but traditionally they were. A bench tops power supply. They were like little white boxes with knobs and dials right, but now they're they're coming up like this there's a new version.

These are the new versions and you need them. Let me show you: i will try to wake this one up using this guy. Okay. So here's the game plan we're gon na attempt to charge it through the bms and see if that works.

If that doesn't work, then we'll have to connect directly into the uh the terminals of the actual battery right, so bypassing the bms, but because this is already connected right. It's got an input right here. This is the load, so we'll have to go through this one right here, the small one, all right. So first, i'm going to connect the power supply.

What voltages we need to be somewhere around 29 volts, that's the max that 24 volt battery will want. So then, we'll turn off all this is the power right. This is the the the amperage so we'll turn it off and then it it goes down to zero the voltage right, because, if you're not pushing any amperage, then so here's the the connector right um, i'm gon na connect it in here. So first we're gon na connect the battery and it just has enough power to to wake up the the bms, so we might be in good shape here.

Okay, so now i just connected the thing i'm gon na raise up the here. We go okay, so it's not putting any in there. Why? Let's see all right, so no, we can't charge it see the that the battery keeps now. It went below uh the voltage that it can even power the bms right, so we're gon na have to bypass the bms, unfortunately, to wake this up, and that is gon na be a lot of the cases.

What you will have to do right, you'll have to just go straight into the terminals of the battery. So let's let me connect that cable here and then we'll try it again all right. I have now connected uh this connector right on the terminals. We're going to connect it now and see what i've done here is i put both male and female so that i don't have to worry about finding the right.

You know gender on the cables right um. Here we go there, we go so we know that that battery is even lower than eight it's at five right, so we'll start bringing up the amperage okay. So it's like look at that. So a hundred milliamps 200 milliamps going into the battery and the battery very quickly is coming up in voltage right, but you're just doing it slowly right.

That is the reason why you need this, because you need to do it slowly. You can't just pump a bunch of amperage in there, like your normal charger will do um. That way. If there's a problem, then on any of these batteries, not waking up, then you know you will see it rather slowly.

Uh, as opposed to you know fast and so 13, we're supposed to be somewhere around what 21 and we're going to be able to check this by connecting it here and then we'll be able to see the voltages of each each battery group right. But of course, if your bms is not smart like this, that has that feature then you can use. You know always one of these things right where you can plug it in here and then just check it out. Uh, let's see does this one say where we're at it's probably going to say: oh they're, all low, so they're all at 1 2.2.

Is there a difference? What's the difference? Oh there's a difference of one volt, oh yeah. These are way out of balance at the bottom. There right all right. What we're gon na do here now is just gon na keep charging this battery and we're gon na.

We can increase the the rate a little bit right, don't go too crazy, uh! Let that number six group kind of try to recover it's lagging behind right. Now that's about a quarter of a volt 234 millivolts difference right as it gets higher and higher it's gon na even out uh and then maybe at the top it'll be fully uh balanced right, because if this was a fully balanced pack at the top, then maybe That's at the bottom is where it's going to show any differences right. So maybe group six has a few cells that are lower capacity and that's why you see uh the the the imbalance in the bottom right and so that that's the case then we'll see them get balanced at the very top right. So there we go we'll just increase the rate there.

We go five and by the way, it's five amps being uh, spread between one two, three, four five uh cells right, so each cell is getting about one amp see all this stuff would not be possible without this right without the variable power supply. It allows you to do this sort of stuff and to diagnose batteries and to see if you can bring them up uh and do all that stuff and by the way these are available in all kinds of sizes. Right here is uh, like the one that i'm using over. There is zero to 48 volts this one right here that goes zero to 120 volts.

So there you go if you work with batteries regularly. This is a must and your arsenal tools that you got ta have either this type or the other type you just got. Ta have apply, variable voltage and current power supply. I wan na.

Thank you for watching this video we'll see you guys on the next one. Bye, you.

12 thoughts on “All DIY Battery builders Need a Variable Power Supply”
  1. Avataaar/Circle Created with python_avatars Tone Ault says:

    hi. can you tell me please. WHAT IS THE VOLTAGE on your 48v and 100v power supply.. dose it go over the stated.. and by how much if any.. ?? please. and thank you in advance. tone uk

  2. Avataaar/Circle Created with python_avatars Jeff Wallace says:

    I keep thinking I want to build a Jehu project. So far I made a couple of ebikes.

    Now I’m thinking solar & batteries. I like starting small, with an ultimate goal of a huge power wall & solar. What is one of your starter battery kits that can be expanded?

  3. Avataaar/Circle Created with python_avatars Pia says:

    A solar panel and cheap solar charge controller on my lead acid car battery will charge at just one volt above whatever voltage the battery is holding at the moment and is the best way I have found to save a dead car battery. It will desulfate after about a week of controllerized solar. I wonder how that would translate to lifepo4 and li ion.

  4. Avataaar/Circle Created with python_avatars Scott Baker says:

    Just charge them as a 3 series NiCd at .2A and they will come up to 3.3v in 5 minutes. Then about 50% will be 'good enough' which for my projects is 2Ah per cell.

  5. Avataaar/Circle Created with python_avatars Kswis says:

    I let the magic smoke out of my Dr meter benchtop and it's now cobbled together so I can use it haha. Every time I click a link for Ali express it takes me to clothes or in this case a remote for $68 though the similar items down below are power supplies… freakin Ali express

  6. Avataaar/Circle Created with python_avatars Andreas Wanner says:

    Thats the way , i wake up low-voltage Batterys. Slow charging directly without BMS. At 2,6V per Cell, you can load it correctly by bms and the right charger 😉 Sorry, for my rusty english

  7. Avataaar/Circle Created with python_avatars swicked86 says:

    You just gave me a great idea for 18650 in packs that need to me recovered. I haven't tried finding out if CC or CV is proper or if both are required.

    Anyhow use neodymium magnets attached to the power wires to connect to the single cell. The nickel plating is a great conductor and will make a strong connection. I've seen magnets that take a counter sunk screw, a ring terminal screw and nut your golden.

    Thanks for innovating and getting me thinking as well!

  8. Avataaar/Circle Created with python_avatars xmtxx2 says:

    Wow, thanks for the info!
    I was looking into some bench power supply for a friend.
    Paid my crappy bench one 0-60V 3A (180W) for 70E 2 years ago. And I had a hard time finding it, most of them were 0-48V.
    Those are 0-80V 8A (500W). For 50E, that's a no brainer.

  9. Avataaar/Circle Created with python_avatars Gold63Beast says:

    Me: calling a friend at 2am
    Friend: hey, do you know what time it is????
    Me: let’s talk about batteries! Have you seen the new lithium battery pack Jehu got is awesome.
    Me: hello?
    Lol Oo well. JK love you bro. Keep up the great work.

  10. Avataaar/Circle Created with python_avatars Gold63Beast says:

    This is the best option for something on the low price range. Definitely. But everything Jehu says. 100%agree. I like the Riden Power Supply but it is expensive but WOW! What an amazing power supply. A bit more complicated but worth it. I have maybe 3. It’s always good to have a few. A cheap one and a really good precise one. Awesome video Jehu.

  11. Avataaar/Circle Created with python_avatars Stevenc22 says:

    I had one of the variable power supplies, but it never quite worked right. Eventually i just bought a bench power supply off amazon and its great and the price was about the same!

  12. Avataaar/Circle Created with python_avatars Jose Arrasola says:

    Good morning sir , was just watching some of your old videos ! On the 3.5jw pack I still can’t get the BMS to turn on ! Which BMS can I put on take off the original one off ?

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