 Hi, I'm MPI. Hi, Annapri. Brought to you by Digikey. This week it's ST. Lady Aida, what is the new product introduction of the week this week? OK, I'm glad you asked. This week from ST, we've got this awesome battery monitoring system based on the part number. It's the L9963E, which is the new generation of their more popular L9963 battery monitor and balancer. And this is an automotive grade battery pack management system. And I don't know how many people who are watching the show are creating their own cars, but there's definitely people who are doing e-scooter projects or goat carts or micro mobility, or they're working on hacking or modding wheelchairs or other devices that use big battery packs. And so having a really good quality battery management system, something that normally would be only sold directly to automotive companies, you can now get it from Digikey. So this is the chip, the L9963E. But we're also going to be talking about the eval board because the eval board makes it a lot easier to use this chip because there's a lot of pins, a lot of components that you need. So first up, the battery in the car that you have if you have an internal combustion engine is just something that drives like the stereo and the headlights and the blinkers and stuff. It isn't something that actually runs the car itself. And these batteries are basically usually 12 volts lead acid batteries. They're big, they're heavy, they last like a decade almost. They're big lugs and they provide just the positive and negative terminals that you connect to your battery. Your internal combustion engine charges the battery and then that's why if you let it sit and it eventually self-discharges, you need something to give you a jump to get started. But if you have an electric vehicle, there is no internal combustion engine because instead you have this gigantic battery pack. And the battery pack is what drives the motors that are connected to the wheels. There's no engine, there's an electric motor instead. And you can't use a lead acid battery because it would be way, way, way too heavy and it's not energy dense enough. Instead you're going to use lithium ion battery cells much like this. This is kind of a standard 18650 cell. This one has like a blue plastic coating and a cable connected to it because we stock it. And then this is kind of a standard size, often made by companies like Panasonic and Sony. In fact, when we went with DigiKey to visit Panasonic, they're like, yeah, a huge amount of our business is selling electric vehicle batteries. And you can put these in packs. In this case, this is a parallel pack where you have three cells and you can kind of see the three cells, parallel connected to give you larger capacity with the same voltage. And in an EV, you're going to have strings of batteries that are then parallelized. So you put a bunch of cells, one after the other to give you about like 48 volts, although that number may vary. And then those strings are parallelized to give you a lot of current and then the battery packs are just like enormous. The thing to deal with these batteries is, first off, the energy density is very, very high. And so you have to safely charge them and discharge them. And you also have to manage the battery life. The batteries are, when they're fresh, they have a huge amount of capacity and then they solely have less and less capacity. But ironically, you don't want people to think that you have more capacity than you've got. Like you want to kind of have the capacity be like some standardized. You also don't want to overcharge the battery. And so as I was reading about this, I learned like, oh, you actually like charge the battery in a different way based on the aging of it. And that's one of the things in the battery management system will help you with. So most important thing is to manage the current going in, current going out and the voltage across each cell. Unlike the lead acid batteries that are used in internal combustion engines, you have to monitor individual cells because you want to make sure that they, there isn't one battery that is charged or discharged at a different rate. And as the batteries age, I mean, when they're first made, the packs, they try to test each cell and match them all up. But just over time, temperature, variations, each individual cell, the one of the thousands in a battery pack is going to act a little bit differently. And so to do that, to manage safely having a battery pack, you have to make sure that each one doesn't get overcharged. And so you have to balance them to make sure they all have the exact same state of charge and same voltage across them. So, you know, this is like a diagram from the presentation that ST has. You can see as the batteries get discharged and the cycles keep going, the more they're disbalanced, the more the capacity is affected. So you really want to make sure like, you don't overcharge the good batteries, you don't undercharge the bad batteries. And to do that, we have a passive discharging balancing system. So it's active and passive. Active is a lot more expensive. Passive basically just means that when it's charging, a little bit of current is drawn off of the charge rate. And that makes it so when you monitor the battery, just making sure that as it gets close to the 4.2 or 4.4 volts, you know, the high voltage for the constant current, you know, max charge voltage, you might activate one of these internal FETs that will drain off current and slow down the charge rate of the really good battery so that matches the worst battery. So basically this means that when you're charging the charge rate is going to be as slow as the worst battery in the pack, but in the end, you get like a perfectly balanced. Cell and you have better battery life overall at the cost of slightly longer charging. Chip is kind of complicated. You know, I didn't read every register. Basically you need to connect to every individual cell. So on the left-hand side, there's all these like internal FETs and connections. And you need a bunch of passes to sort of carefully monitor each battery cell. There's also a bunch of temperature monitors you can connect, which is important. You want to make sure that when you're charging you monitor every other battery or cell. So you don't overcharge based on if it's too cold or too hot, you have to change the charge rate. And then you can see like it's pretty complicated board. Just why actually you recommend the eval board because for like 40 bucks or so, you get everything and it's ready to go. And another thing that's interesting, oh, this one is, yes, you'll do eval board. So at the bottom there's a port you can connect to up to 14 in, they're parallelized here but they should be serialized. And the isolated communication is interesting. So obviously you've got this very high voltage battery monitoring system and you want to make sure that you charge the batteries safely, but also you want to make sure that that 48 plus volts doesn't feed back by accident into your low voltage electronics. And also, there's a lot of current moving around a lot of EMI to make sure that the battery protect the battery management system is protected from itself and your microjones present from it. They use this as isolated SPI interface. And so what you see USB ports up there, they're not truly USB, it's a USB mechanical connection, but it really is using a differential isolated communication protocol that uses SPI over this differential set. And there's a separate board that you'll have to get to use this eval board that will convert your standard for wire SPI into the ISO SPI, just FYI. And this just shows the interface. So yeah, you have fully isolated communication between each board and they can be daisy changed. So if you have multiple battery packs, you just chain them together over this four wire isolated interface and you can address each one. We did find a library that chip is fairly complicated, but we found that there's a cool student electric vehicle group that published a library on GitHub for STM32 chips. So check it out if you want to get started with this chip and this board. Again, I recommend getting the eval board, but you can quickly query it, ask it about like the state of charge, tell it how much you want to balance or do balance. Everything is like CRC and isolated and protected. So it's like, again, it's an automotive grade solution, but you can use it for making your e-scooter. Available at Digikey. It's in stock. Yeah, so that means you can buy it. You can actually buy it. All right, that is a quick sign-up, yeah. Hi, I'm a PR.