Learn with me; iCharger X8 - How to build a 48v Lifepo4 battery (Ep. 9) 

Fun history lesson. When I was in highschool, admin would not allow me to take the electronics course because it was just for boys. I got to take typing though! Turned out real useful when I started programming in the 70's and was one of the very few programmers who could type.

@@denisebrooks4513 nice story good to heard you still got to do what you wanted to do

It's one of the reasons I wanted to show everything, in detail and good and bad. I knew it'd likely limit how many people might want to watch, but it was a way of documenting that I'd not really seen elsewhere before, so I figured that's the "niche" I could try and fill. :)

@@TheDigitalMermaid dead right - i'm never sure about these clinical videos and since you are learning as you go, the progress is very interesting - i often comment on people doing stuff and never doing the final video of what to buy and how to put together, the ultimate manual if you like, that will be great to see when it happens

That's good to know. It'll have been about a month by the time I spark up the quattro. I did go through and top balance each cell individually after the parallel video. It'd be easy to do it again, so I'll do that before firing up the quattro for the first time. Thanks for that, solid advice!

Honestly, they're the best weekends

I couldn't have done it without the help of others. That's what I hope for the most with this channel, to build a community that helps each other figure stuff out. ^_^

Thank you :)

yes i got that charger it can do everything i used also isdt q8 max charger but many things is limited discharge is limited to 3a and lower voltages is for li ion is limited too so only the icharger x8 can make full tests of battery capacity.

This PSU was indeed chassis ground common. I'm curious how you would have configured the charging in a 2P/8S configuration. Do you mean treating the charger as a sort of BMS with the 8 voltage lines connected and let the charger do the top balancing? In any case, yes, "slow but steady wins the race" is very much a mantra of mine. :)

@@TheDigitalMermaid That charger has the ability to "balance charge" in series. It will monitor the 8 cells via the balance leads, restrict charging to whatever current keeps the highest cell at 3.65V and will bleed off excess current @ 2A for balancing. You would have had to buy/fabricate an 8S balance lead. Essentially, you could have paralleled 8 groups of two cells and then put those 8 groups in series. With a 12V power supply, you likely would have been limited to about 360W of charging power (unit has a 30A DC current limit). Even so, you would have been able to charge at 12-15A, but at up to 29.2V. Since these cells ship at about 50% SoC, you needed to put about 140Ah * 16 = 2240Ah total input. @ 30A, that's about 75 hours, thus your 100 hour time frame makes sense. However, a 2P8S configuration only needs 140Ah * 2 = 280Ah. Assuming you can only do 12A, that's still 280Ah/12A = 23 hours.

@@snoobler It actually took me a while when starting out with "large" cells that "Balance chargers" don't seem to exist. I had lots of questions like What? Wait, how? Why? How does the charger know a cell is hitting max volts when the pack voltage isn't "full" yet? How does it know to back off the current? I suppose the answer is... it doesn't. The chargers are dumb and have no cell voltage awareness. At least it means you don't have the slow, torturous tapering to sit through while you wait on your 5Ah LiPo 30C discharge pack finally absorbing to 4.20V across all cells. Seriously! 10-80% 20 amps, 10 minutes. The next 18%.... another 10 minutes. The last 2% of you want it, another 10 minutes. However. I am not giving up that easily. First. With care, attention and a bit of luck, you can get the chargers/MPPTs configured (in lead acid mode!) in such a way that they will be tapering current and the load the balancer is able to place on the cell-delta asborbs that tapering current. At the moment, the BMS is set for 3.650V per cell HVC. However the MPPT is set to 14.40V. It seems, further testing to be conducted, that on my system that tiny headroom is enough to mean the balancer has got the ability to take full control of the taper current of the pack as the MPPT tries to taper off at 14.40V. It also adds grace for the MPPT being a little sloppy coming out of shade and occasionally overrunning it's MAX charge voltage by 100mV or so, rarely, but happens. The MPPT over-volt dissconenct is set to 15V, but the BMS will go first. I am pondering that changing the order of that might be preferential, such that the MPPT controls any such disconnect from inside, first and then backed up by a slightly higher setting on the battery. Secondly. I am going to do some research using smaller cells and a way to "tamper" with the chargers feedback loop to force it to see the max cell voltage. Well maybe not see it, but have a cell voltage monitor which based on it's max cell figure begins to introduce a very small voltage drop just past the BMS. Say a 50mV drop. The charger sees the pack as "14.40V", but it is in fact only at 14.35V, the MPPT current tapers for 14.40V allowing the balancer more time with it's limited power to fix the situation. It would mean some "bled power" by that voltage dropper mosfet and it's heat sink, but if it saves HVCs and allows you to trickle absorb right up to, say, 0.05%C current. It might be worth it.

Another feature of true balance chargers is that in full "Balance Charge" mode, they don't just top balance. I charged an old LiPo yesterday that has a weak cell. It started out at 3.10V, 3.45V, 3.55V I set the charger to 5 Amps for a 5Ah pack. It started charging at 0.1A. It took it 10 minutes before it began to slowly ramp up the current. It uses a "current -> cell-delta" relationship, so that it won't hit the pack will full current until the cells are within a certain tolerance, does it interatively though, smoothly ramping up as soon as the resistive balancer can hold the max cell delta. Compared with the "Fast Charge" mode, which is pretty much what half the MPPT setups I have seen do. Immediately to full current, to hell with balance. Then taper based on MAX cell voltage and MAX pack voltage to 10% original charge current and then stop. Even then it is aware of the max cell voltage and if it is the one which brings the charge current down to termination current, then the pack is left not fully charged and not balanced. If you are using and fast charging them all day like this, it really hurts them (LiPo RC high discharge packs). It seems that is how most solar charge controllers treat batteries, only leaving it up to the BMS to disconnect completely and almost PWM the last phase.

I appreciate all advice (kindly) given. So please never feel a need to apologise. I mentioned elsewhere, but I'll say again here; I would rather get information I already know ten times, if it means I don't miss good information that might not otherwise be shared once. Ya, I've been thinking about how the X8 doesn't really do absorption, and I know it's a topic Andy has spoken on often. I've been planning to return to this topic once I get the Quattro working. Part of me is hoping I can use the BMS to hand absorption and that the cells will be close enough that the BMS's small top balancing capabilities will make up the difference. I think this is possible (maybe) only because the X8's 30A is still just over 0.1C. We'll see. If it's a problem, then I'll dig into the X8's configuration options to see if I can somehow configure absorption.

@@TheDigitalMermaid not sure if you have seen this yet, but if not, it is time.... ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-QlDd3jkcxoQ.html

I'm not sure if there's a specific thing you're interested in, but the design I am building for is to drive a motor that has a maximum continuous draw of 600A at 48v. So the bank of 6x 100A constant, 280Ah capacity batteries will drive the motor at max speed for just under 3 hours. In practice, I never expect to run at 100% load, so I am hoping to have over three hours, minimum, of real-world pure battery drive. The same bank of batteries will provide the house power as well, as I plan to have induction cook tops, electric over and a clothes washer onboard (not used when motoring, obviously).

I'll need to order some longer bus bars, but I was thinking of doing that anyway. Giving time to let all the cells balance with each other at rest is probably smart.

@@TheDigitalMermaid I just used ring terminals and 12AWG wire to balance at rest. Unless you are pulling an Andy, it will easily handle the amp movement.

@@thomash7573 Honestly, a couple copper bars would be a lot cheaper. Those ring terminals and marine grade wire are not cheap. :)

@@TheDigitalMermaid I had it on hand. Cheap wire though. I look forward to your next videos!

As I hinted at in the intro, covid has caused my plans to be messed up. I have put a lot of thought into the boat type I want to buy, and the system I am designing can be adapted to a set of different electric motors / boats. So while building the battery / power system first isn't ideal, I know the corner I've painted myself into, and it's a nice corner. :)

@@TheDigitalMermaid i prefer to use the QS 138 3000w motor + votol em200 controller that is great and big power this can pull about 11kw in max

@@automoto95 I'm happy to hear you found a good motor and controller for your use case. In my case, I'll need something a fair but larger. Since I released this video, I've more or less settled on the Torqueedo Cruise 12.

Sure; rotorquest.com/icharger-x8-new-1100w-30a-charger

I may well have a generator for times when I really need it, but I'll do all I can to never use it. My hope is that the times that I drain the battery completely will be rare... I want to sail, not motor, so I'll only motor when I need to. So that's part of the strategy, but also, I don't expect to motor every day. If the batteries get drained a bit on one day, they likely it'll be several days before I use it again, so the slow charge rate will be enough. I also plan to have a regenerative motor so that, while sailing, the prop spin will help charge the batteries as well.

The BMS has limited capacity to balance cells. The X8 is used to do the initial charge to get all the cells to the same (near) level. Then switch over to the BMS to (hopefully) keep things balanced.

@@TheDigitalMermaid Why would the BMS have "limited" capacity to balance the cells? That is what it is designed to do. Why bother with another monitor (X8) that is treating 8 cells as if they were one cell when the BMS monitors each cell individually?

@@silverleapers I did a video explaining this - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3qoU5kohtjw.html

It could be the source power supply charging it, but I'm not sure. What's the 12v amperage supply capacity of the PSU that you're feeding into your x8?

@@TheDigitalMermaid thank you very much for your quick reply!!! I don´t have a 12v Power supply but just ordered one for a final Test. 12V/40A. I hope, that will deliver more then 6A with the x8.

@@MVbubblemaker 12v at 40A is 480w (12*40). 3.65v at 30A is 109.5w. So even factoring for inefficiencies, that 12v / 40A supply should easily allow full power delivery on the x8. Best of luck!

@@TheDigitalMermaid Thank You! But all of the power supplies I've tested also had much more Watts then normally needed...

That's annoying... overheating, or limitations on the source power?

@@TheDigitalMermaid I replaced my leads with heavier gauge wire and now its been charging at 20amps. my 16 280ah cells finally got over 3.334 volts lol. While in series I had one cell hit 3.60 while the others were still at 3.3 so I put them in parallel and top balancing with this x8. Hopefully it wont take too many days to top balance the cells.