Current Sharing Experiment: 25kWh LiFePO4 w/ Diagonal Wire Configuration
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- čas přidán 7. 02. 2022
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Every video includes some form of paid promotion or sponsorship. Some links on this youtube channel may be affiliate links. We may get paid if you buy something or take an action after clicking one of these. My videos are for educational purposes only. Information is subject to change/update at any time. Electricity is DANGEROUS and can kill. Be smart and use common sense :)
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Some are saying that this configuration should allow for equal charge and discharge. Not true. One of our forum members did the math! Check it out here. It shows why I got the results I got:
diysolarforum.com/threads/some-modeling-to-go-with-wills-current-sharing-videos.35121/#post-439794
Beginners should check out the free PDF from Victron called Wiring Unlimited. It is a fantastic resource if you do not understand what is going on in this video: diysolarforum.com/resources/wiring-unlimited.2/
Part 1 of this current sharing series: czcams.com/video/oXBT8lSC25M/video.html
Server rack batteries: www.mobile-solarpower.com/server-rack-lifepo4.html
All in one systems: www.mobile-solarpower.com/all-in-one-122448v-packages.html
~~~~~~~~~~~~~~~~~~~~~~~~~~
Does off-grid solar confuse you? Check out my DIY friendly website for solar system packages and product recommendations, and so much more! www.mobile-solarpower.com
Join our DIY solar community! #1 largest solar forum on the internet for beginners and professionals alike: www.diysolarforum.com
Check out my best-selling, beginner-friendly 12V off-grid solar book (affiliate link):
amzn.to/2Aj4dX4
If DIY is not for you, but you love solar and need an offgrid system, check out Tesla Solar. Low prices and great warranty, and they can take your entire house offgrid with their new Powerwalls: ts.la/william57509
~~~~~~~~~~~~~~~~~~~~~~~~~
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Join the forum at diysolarforum.com/ if you wish to hang out with myself and others and talk about solar
FTC Disclosure Statement and Disclaimers:
Every video includes some form of paid promotion or sponsorship. Some links on this youtube channel may be affiliate links. We may get paid if you buy something or take an action after clicking one of these. My videos are for educational purposes only. Information is subject to change/update at any time. Electricity is DANGEROUS and can kill. Be smart and use common sense :)
DIY Solar Power with Will Prowse is a participant in the Amazon Services LLC Associates Program,
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Could you cut/drill some small copper bars, very short, that fit the width of terminals, then bolt your larger lugs onto on the other end? Sufficient thickness to handle the currents involved? Sort of like an extension.
I have the hard copy of Victron's "Wiring Unlimited", so I recognized your diagrams. But again, the conductors are different lengths in that example. I'm thinking the important lengths are the jumpers connecting battery to battery and not the lengths to the load. Would you agree?
Can you do a video on how to size bus bars?
@@jimsjacob yes, exactly.
@@MYCHANNELWITHMYSTUFF find a table of wire gauges and resistance for pure copper wire, pick the gauge you want, then calculate the cross section of that gauge (pi*R^2). a bus bar thats X wide and Y thick has X*Y cross section. example, 2/0 is 0.365" diameter, so thats R=0.1825, pi*R^2 is 0.10 square inches. so if your bus bar was made from 1/4 inch thick copper it would need to be 0.4 wide (0.10 square inches / 0.25 inch thick == 0.4 inches wide) to have the same cross section and DC resistance as 2/0 wire.
Hi Will I'm 56 single female and at 55 because of watching your videos I felt confident enough to design and build a off grid solar system. It worked perfectly from the very beginning and has worked since... its going on 2 years. Your videos are so informative and you are such a good teacher...Thank you for all of the thrilling opportunities. Tammy Halcomb
Would be interesting to a thermal camera to your tool kit. Would be cool to ‘see’ the cables warming up. It would also be handy to help identify bad crimps or bad connections too.
@willprowse I can't remember what video started me on the youtube rabbit hole but when I cam across your's (looking for opinion videos on RV batteries) your information, presentation, detail, proper procedures,etc , the first 2-3 seconds I thought you were a high schooler but then quickly realized no way could someone that young be this knowledgable. I'm a micosoft sys eng... but your channel got me binging and finind a new hobby Batteries!.
I absolutely love these battery tests! I spend do much time wondering about the best ways to wire batteries like I going to reinvent the wheel, then will not only does the tests but explains everything in great detail.. thank you @DIY Solar with Will Prowse
It’s actually quite simple. When the batteries are at the top or bottom of the curve, the large batteries will supply more power (amps) as they’ll stay in the steep curve longer than smaller ones (they’ll be both supplying the power and pulling up/charging the smaller batteries). Once they are in the flat curve all will contribute the same as all will be around the same voltage. Once they reach the bottom curve, the large batteries will supply more power again as they will still be in the flat area - they will “prohibit” the small batteries from dropping - keeping the voltage at the flat area.
Bottom line, if you want to use this type of setup, especially with LiFePo4, just keep the voltages very close to the flat area. Then 99% of the time, all batteries will be contributing the same as they will have limited voltage differences.
Exactly!
@@WillProwse in future can you do some ebike battery testing and budget ebike testing please PLEASE
@@richardhobbs7107 I just received a Ancheer Hummer model ebike and I want to modify . I do love it so far but 22 mph in full electric mode is to slow and replacement battery packs just have me scratching my head I can't tell good ones from ripoff junk
It would be useful to know how much of these SOC differences are due to their curve characteristics and how much is actually due to voltage drop.
Will, I really liked this hands on example of a practical system. This is the best of the internet.
Awesome video as always Will.
One of the things I really appreciate, is the fact that you stay on real world topic. And Don't drift off into minutiae that nobody really cares about. Not to mention the fact it over complicates. I consider myself a novice at best. Please keep them coming big guy!
I have read (and heard of) all the different things that were demonstrated in this video, but this is the 1st time I've actually seen it. Outstanding video, Will!
Fascinating results, thanks for the additional testing!
Good to see it working well. I have 12x 100A lofepo4 connected the way you showed at the video!
Man, this is top notch. Nothings like a visual demonstration like this
Awesome and useful test and proof points. It also shows how well the MPP LV6548's handle large loads!
Hello Will. I just want to say thanks for all of your videos. You have the coolest job and I really appreciate the information and tutorials. Keep it going! You’ve inspired me to put together a 12V 600Ah system for my RV and I’m in the midst of building it now. This battery test video reassures me that I should be okay to use 4/0 cable and hookup my six 100Ah Lithium batteries in the same diagonal wiring configuration you have demonstrated here. I hope to be finished with it in a few weeks.
You have alot of effort put into this channel , you are the boss on this topic !
Thank You Will, every one of your videos are a learning experience of eminence value. Amazing you give it away. You are a good man.
i bought the book -mobile solar power - made easy thank you for writing this - very easy to understand
I use a bussbar with opposite connections and have no issues and highly recommend it, well worth the investment
Great test example Will. Well done 👏
In the Army we wired the batteries diagonally. This was something I learned in AIT Electrical Engineering, to balance the charge and the load and get longer battery life. Those were lead acid batteries on trucks though. Glad to know it works even on LiPO batteries for when I convert over from lead acid. Right now, living alone they work for me and are less expensive up front.
sadly, the dual batteries on virtually all diesel pickups like my ford f250 are NOT wired diagonally. each has its own chassis ground wire, and the loads are all connected to one, which has a fat wire over to the other.
Watching this again because as I mentioned elsewhere I'm playing with a lithion and lifepo4 parallel packs connected to the same inverter. It really I testing how the two act differently but the major item I'm noticing is how they share current. It is really I trusting. I've got a pile of wire from changing lengths, guage, and I've ven recently changed the connection location. The lifepo4 likes to dump current but the lithion shines on low current constant load situations. Best way to thoroughly learn is with your hands. Personally anyway
It always good seeing you do your thing, great job. Thanks 👍
Thanks for sharing your results. Much to be considered...
Pulling current like that in an experiment is just fun. thankyou for the real world example
Excellent demonstration. My system uses equal length conductor paths which I prefer although in a larger system that would entail buying a lot of copper. Your diagram called it Post pattern.
Can't wait to see the busbar version of this experiment. nice video
This was a great understandable video Will! Thanks for sharing!!
Love how detailed your vid's are great job as always. I can't stop looking at the screwdriver sitting on top of the batteries tho lol
Thanks for the tests and knowledge.
I am so grateful for your content Will. Thank you so much! A++ work sir.
Very informative. Thanks Will, keep them coming!!!
Always appreciate the knowledge that you share with us. PS I miss your informal live streams too I’m just saying.
Awesome Content. These videos are very helpful learning material.
Thanks!
I was thinking this last night when watching your video on top balancing lifepo batteries.
Oh my word that load test was just insane!!!
Right!! So fun 😁
Heh...in grad school I had a high-current, low voltage experimental rig that used 5000 watts at 12 volts. 0000 cables, brass connections, and they still got hot enough to melt lead solder. Had to use silver solder. Rig was, of course, water cooled, even near the connections...but that was a LOTTA current. Of course, we were heating carbon tubes up to 2500 C.
Really nice example!
These last two videos have a dress questions that I have had for a long time. I’m still re-watching them to make sure I understand everything and I just ordered some appropriately sized fuses so that I have my batteries properly protected. I keep learning from you but like someone else said earlier I am especially admirable of your focus on safety. I have a neighbor who is trying to learn about solar and he is putting one into his RV. He’s been watching your videos but I don’t think he’s listening closely as he had four 100watt panels in 2s2p connected to a controller with a 50 foot piece of extension cord with the ends cut off, all feeding into a 3000 W inverter. Think it was 16 gauge. The inverter came with cables which were intended to be paired but he only had single cables on them. His components were correct per your plans but the wiring itself was downright scary. I think I’ve got them straightened out. A bit more focus on correct and appropriate wire size would be helpful for the newbies. Otherwise I’m always really loving your videos.
Interesting results. It looks like it depend on battery itself. I didn't expect it will be like that.. It might be good lesson for ppl who got a lot of parallels cells or systems..
Great job explaining.
Very nice presentation
Thank you for the video report .
I think that answered my question perfectly. Better, but not best.
I love how excited this guy gets by some batteries.
You need 5 rack units of the exact same brand put in an actual rack. Then do the following tests. Wire it 3 ways: Bus bar, same side, opposite side. Cycle each method and record each battery for % of total amp draw at 100/75/50/25% state of charge. This is a lot of work but would fully prove how each one performs. I agree that it will most likely level out once you pass the first 10-15% of a battery charge.
Yes I plan to do that soon. I don't have that many packs but will soon.
Bus bar is only method I've found to work every time.
consider use one DC current clamp to capture the current as each battery and make consumption calculation be good.because each battery inside meter not the same reading sir.
Excellent Demo.
Hey man, this was a pretty cool experiment. I noticed you didn't measure the voltage drop across each length. That would've really helped explain the variation and show how much the diagonal configuration is normalizing C rate along the chemistry's discharge curve compared to the daisy-chained configuration. Then, when you mention how bigger batteries have lower internal resistance, it will actually provide context towards the experiment you're running. In addition to calling out current and SoC, please call out the pack voltage and if it isn't too much trouble, the voltage drop across the cable segments.
Thanks for the vid.
just great information on this channel
Thank you for this video
Wow that is what I thought would happen, but it is always awesome to see it in action!
I think the best way to connect the batteries is Posts or functionally identical short Bussbars, what I mean is that you have equal lengths wires either stacked directly on top of each other in the Posts configuration (but that would require alot of torque) or alternatively use the exact same wires to connect everything to a copper bussbar that is only spaced apart enough to fit the lugs next to each other. That way you have the advantage of Posts but you have much more surface area touching each lug, because a lug to lug connection is never perfect.
that is why I have a copper pipe 1/2" flattened and drilled hole to equally distanced batteries. There is only one screw in point. And opposite take off +ve and-ve 3x200 ah 12vdc in parallel
@@leopoldpoppenberger8692 copper pipe is a good cheap way to get started. May I ask how you attach your lugs to the pipe? Is it bolts and nuts sandwiching the lug to the pipe or is the pipe threaded and you are tightening down to that?
If you were to ever upgrade your inverter you should definitely increase your system's voltage. Get a 4th battery and wire them all in series to get 48v that would certainly increase your efficiency. If you are also using 12v appliances then just use a 48v to 12v DC-DC converter.
only thing left to do is show us the bus bar setup with these packs! :D great video Will
Great info as always, thx
Will it would be nice to do a video using copper buss bars and comparing the results to your other videos and seeing the different numbers.
Hi, love your vids
Nice video … would have loved to see you measure the voltage drop across the conductors to make your point with numbers.
I think using large gauge wire with the correct size lugs for your terminals and figuring out the best order for the packs would work great. If the lugs are too wide trim problem side or sides and hook it up.
@Jason Morgan
Exactly- I’d have just trimmed the terminals on the grinder.
I tried that and it still pulls more from batteries closer to the load. As Will mentioned in the first video on this, it’s when you start pushing towards the output limits of the batteries that this issue arises. In that case the cost/size of the wires needed gets excessive. I’m going with the Victron image (third one) with the “posts” configuration, as I don’t have rack mount batteries. I’m using small free standing bus bars from Amazon to hook the batteries to the inverter, and the same for the charge controller. The bus bars are going where the big dots are where the four leads come together in the diagram. And of course, a much larger cable between the bus bars and the inverter and charge controller.
Keep it up!! I love it. Thanks Alot!!
Another great vid!
put the terminals on the two middle packs surrounding the center pack for peak cheap balancing :P
I've done just that before, now I see its actually beneficial somehow, all I cared about was symmetry, turns out its also functional! I'd put the two newer packs between the 3 old ones also
Thanks
Very informative
I have to get my electrian to watch this vid before the install of my batteries on my boat. Thanks Will...!
cool video, thanks
Years ago when I worked in car audio, a common problem was large stereo systems that would call for 200 to 300 amps of sustained current draw, but working with 2/0 wires wasn't always practical. We would instead use 2 2-gauge wires in parallel. Looking at these server rack batterys' terminals, it would seem that if you can stack terminals, this would do the trick. That being said, by the time you bought, cut, and crimped all those cable, it probably would have been cheaper to buy copper bars and drill/file them to fit.
Nice Test !
I’ve never had an issue with diagonal as long as all the capacities are the same. I just ran a test on a 2P X 16 620ah battery. Did you know that 175 amps on 2/0 cable for a few hours makes a nice hand warmer?
Try using the diagonal configuration, take the power leads to the inverters out of the batteries 1 battery from each end. This will reduce the current from the jumpers that got hot and may allow the batteries to discharge more equally.
After what I can see and also what he is saying this IS diagonal configuration...
A nice wee torque wrench is needed for uniform tightening of the terminals, takes out the guess work. Split bus bars are the way to go for high current discharge/charge. Nice copper 3/8" thick from the BMS would sort out any resistance issues. With the energy prices going through the roof in the UK 50% INCREASE in April, I think the return of investment would pay for itself in half the time.
Awesome experience thanks. Since the hotter cables have greater resistance, could this have played a role in the current leveling(ish) out?
Please tell us that you are now doing the same experiment with buss bars for us to see!?!? Great video!
It would be nice to see you do the same test with the bus bars.
Treasure trove dude, thanx.
Bus-bars are the same as a diagonal configuration but essentially with a larger conductor. At some point a battery bank grows large enough that you would need really thick and long bus bars, so it becomes more economical just to have equal length conductors from each battery to much smaller bars (length wise).
Yes very true!
A very interesting episode. Maybe next time you will show experiments with connecting batteries in series ...
If you look at the charging curve on a TESLA MODEL 3 with LFP what was called the SR+ especially in colder weather, it starts out building the kW quite slowly then ramps up later but for longer than NCM etc on an LR or Performance.
Will, how about doing a video on specific bus bars?
Well done, Will. A very clear picture of the issues of parallel battery design.
Someday, we'll get away from these ridiculous low voltage batteries for home power. I think 120V should be the practical minimum, with 350VDC for larger applications per many server farm power/battery systems (230VAC switching supplies work at that DC voltage). My own custom off grid system is 120 VDC; no need for parallel batteries or big wire. It's been serving me well for over 12 years now.
Dc voltage above 60v is considered dangerous, and then you need protection for the build which makes it harder in other regards, but yes you also could simply not care.
My comment was about the future of higher voltages for battery banks, but really that is already here.
The Tesla powerwall is already 350-450V. So are their car batteries. I assume they care about safety, as do I. So do Server Farms, who use 350V battery/DC distribution systems.
Many people has been seriously injured by accidental shorts of batteries even at low voltages. There is no magic voltage where safety is assured in spite of unsafe practices and ignorance. 120VAC kills people but is in common use. DC has 4x the shock safety of the same AC voltage; this is a well proven fact. I suggest that 120VDC is a good next step for off grid battery voltage because I use it myself, and 110VDC has a long history of relative safety for home power from back in the Edison days, with bare uninsulated wires on ceramic posts and tubes. As I write this, my computer and rear projection display system with stock power supplies are running directly off of my unregulated battery bank DC voltage; 133V at present. My lighting and daytime cooking are also direct 120VDC, zero conversion loss.
The same safety concern should apply is your typical high voltage PV array, even if feeding a 48V system. Someone with less power safety training than an electrician should not work with higher voltages. I was commenting about the obvious technical future for off grid battery bank voltages. 120VDC is a good, relatively safe next step, in my experience of over 12 years with it. I'm a retired EE and designed and built my own power system. I should probably avoid commenting on public forums for the obvious reasons as illustrated here.
Will does a good job of mentioning safety, and perhaps he should do a separate safety training video. I'm very impressed with the quality of his technical content and presentations. Bravo, Will.
@@brucemccreary769 Anything above 60V is considered dangerous in most countries. DC is not less dangerous than AC, actually it is more dangerous because if you get hit by it, the chance that you muscle keep contracted is much higher than with 50Hz AC where you can still let loose the connection you grabbed, as it is not constantly flowing current but alternating. There are for sure ready build powerbanks which have much higher voltages because of efficency but then they are closed products and not like on this channel, DIY solutions. So if you are talking about finished products, yes there will be higher voltages. If you are talking about DIY you will not get much more than now, this is voltage of 48V LiFePO4 which fully charged is nearly 60V is not just an accident. It easy to raise the voltage, put more cells in series, but the danger of serious injury also raises. This does not mean that you cannot simply do it if you feel yourself comfortable with, but i think you should not expect a public youtube channel which has thousends of viewers present possible dangerous solutions.
Alas, your information on the ""can't release"" safety of AC vs DC is absolutely wrong.
You can easily confirm this at any reputable engineering or physics web site. Try AC vs DC safety in google. DC is 3-5 times safer at any given voltage, and the "can't release" voltage is higher with DC, not lower. You might want to actually learn something about electrical safety before further posting.
The difference in currents between the rack batteries in parallel are because of the difference in capacity. The larger the batteri the more amps needed to get same SOC . Discharge same pattern where the larger ones deliver more amps becuase of the larger capacity
Appreciate your analytics. Ever consider explaining high output alternator charging of lifepo4? I’m considering installing a Nations secondary alternator for my Battleborn bank. But the internal BMS seems to be an issue allowing a complete charge even with a Wakespeed regulator.
Well, thank God for Will Prowse and his NBS (No BullShit) Channel. Here in Puerto Rico the neoliberals are privatizing the grid with LUMA Energy, and we need to migrate, not out of the islands, but to Solar. This is good, practical info. ¡FUERA LUMA!
Nice video again bro & those wiring looks so massive & is it really necessary to use the high gauge wires or it depends on the what metal we're using?! Just for clarification.
Grat video. I think that the size of the wires in between the packs is important. In here we have thicker cables on each end of the string but thinker cables between the individual banks. If all the wiring was done with the thicker cables we would have more balanced results ( proportional to the capacity) as the resistance on the hotter thin wires would be smaller.
But we cant. Did you see the video? The max you can add on this terminal is 2 gauge. These batteries come with 6 gauge wires. That's a huge reason I made this video.
@@WillProwse yes I've seen it and I understand why you have done it this way. You can do this by filing the connectors so it fits. I didn't see the surface too close so can't calculate exactly how big the connection surface is there and whether enough for 230 amps of current but I think it was worth asking. I know that it is never good to tamper with the connections but you are wire enough to do it safely ;)
At the 6 min mark, when feeling the cables. Visual thermal imager would be cool screenshot of the pack and cables.
Yeah that would have been awesome. Should have used my thermal camera.
Thanks for the video Will. I was interested to see what happens when you get to 0% SOC on this setup.
Do all of the server rack batteries shut down at the same time or,
do they shut down individually till only one is left to supply the whole load and it shuts down because of added voltage drop or overcurrent protection.
Question: Do the positive and negative wire lengths from the battery to the system need to be the same length? I see in the diagram, and also in the video, that they appear to be different lengths. I'm asking since it seems to be important for the cables connecting the batteries together to be the same length. Why not so in connecting batteries to the system?
Brilliant
Please note the the current is additive, so the interconnect wires closest to the output is pulling all the current. That is why they are hotter then the other upstream wires.
If you connect the output wires in the middle of the pack, then no single interconnect will take the full current.
Yep that's right
so entertaining... mind blown
You talked about the wires coming from the inverter needing to be equal links going to your distributing block. What about the wires from the distributor box to each battery bank do they need to be the same length as well.
Great test, too bad you stopped at 60% (?) SOC.
Draining them till the first low voltage protection kicked in will show how it would perform in a real setup.
Charge with solar, discharge at night.
Especially as it's a mix and match pack, that's useful information!
Many of us upgrade their system as they discover to have not enough storage.
Seldom the same configuration can be bought.
Busbars work always best for me :-)
Instead of using a busbar, I use thicker cables as needed to equalize the batteries. Seems to be working well for my installation.
Appreciate the lesson on options. I wonder how the battery balance would turn out if the main cables were connected to the middle (lower volt reading) battery. ... That might be worth a test on that specific battery set. ... just some thoughts
This is awesome! I'm about to rewire a sailboat and this info is what I was thinking about. Bus bar for sure. I'm just curious, with cells is series, is there a difference in the amperage drawn from each between the end and inner batteries?
you could always grind or file the sides down slightly on the ring terminals to fit on the battery terminal strips...
Interesting experiment but I think a lot of people would say the difference in internal resistance and the difference in capacity would also throw off your numbers at the rate of discharge.
Unless the batteries were all from the same year make model manufactures date of production line then you could be confirmed of accurate numbers
Yes that is what I said in the video
Nice video Will. In the long run it would be best to use a copper buss bars using a bar that is 3/8" x 2 1/2"?(the width of the terminal block) this will balance out all five batteries outputs. Also you can eliminate the cables just by mounting the buss bar to the top of the batteries using some copper spacers larger O.D. the best, you can also use both terminals to connect to the buss bar to increase the DOD and charging capacity.
Should have mentioned you should use heat shrink on the buss bars between the batteries terminals, then use a liquid rubber paste to cover the exposed terminals or install a hinged plexiglass cover for safety.
Will...you need a bench grinder, so you can fit your cables in narrower terminals when needed.
I would like to see a test with the bus bars.
As long as the conductors are large enough to avoid voltage drop across the batteries it doesn't mater which way you wire it.
You would get more stable charging/discharge with connecting main wiring to the center battery versus an end one.
Not necessarily- the length of equal gage conductors is the factor in play
Thanks Will. That's really useful. Is there any chance you could do a test with the halfway configuration? Also, should the power take off be on the same terminals as the charging leads, or different ones? I ask for practical reasons, as I have 4 domestic 12v batteries on my boat. (Currently agm. When they die, I want to go lithium.)