DIY 24v LiFePO4 Solar Battery Bank! Beginner Friendly, 2.4 kWh, Cheap, Full Tutorial!

so in a previous video we built two do-it-yourself lithium iron phosphate 12-volt battery and these are awesome because they're super cheap they're cheaper than a sealed lead-acid and they work with standard 12 volt equipment and we made our own busbars we learned how to balance the cells it was really fun and a lot of you guys sent me pictures of your setups and you guys did a great job I was amazed at how well you guys did on today's video we're gonna build an eight cell 24 volt lithium iron phosphate battery in this video will be geared for beginners almost anybody could attempt it there's not much that you have to put together and it's very safe it's a non combustible battery it's very cheap to buy these cells off of ebay and they store a lot of power so for this many batteries it cost me $600 and that's the equivalent about two thousand dollars in a drop-in lead acid replacement so it's cheaper than a sealed lead acid it's cheaper than lithium options and these have a very large charge cycle life because their lithium iron phosphate so we're talking at least two thousand to five thousand charge cycles no matter what it's so easy to build you guys are gonna love this so for six hundred dollars being at 2.4 kilowatt hours of power the discharging charge rates are extremely high and this battery works really well with my new 24 volt 1000 to 2000 watt solar array system so if you build that thing for $600 and then you buy this with $600 for $1,200 you have a system that beats everything on the market for a fraction of the price like it's insane this is the only time it's worth it to do a do-it-yourself battery and in the previous one we used electrical tape in copper pipe that I smashed is busbars but in this one we're gonna make it look nice and pretty we even have nice bus bars we have terminal covers and we're gonna make it look really good even though this battery is geared for being built by beginners we still need to talk about some safety considerations because this is still a lithium-ion chemistry so first of all you cannot have an over-voltage situation or you cannot overcharge it if you're using standard equipment 12 and 24 volt equipment that works with a sealed lead-acid battery it will work with lithium iron phosphate they have the same exact charge profile so it's very hard to do but understand that if you use some weird high voltage charger it will damage these the next consideration is that you cannot over discharge these batteries unless they will be permanently damaged and you cannot use them anymore and the best way to protect from this besides having a dedicated BMS board is to have what's called a low voltage disconnect and I always recommend people buy the Victor on energy battery protect because it's programmable and it works for 12 and 24 volt systems it works perfectly for lithium iron phosphate so if you're attempting to build this please buy a battery protect they are very easy to use and very cheap the next consideration is you cannot store these in a hot ambient temperature environment so if you have a battery compartment and it's ventilated and nice and cool throughout the summer months you're okay if you're using a storage compartment in our V or a shed that's really hot these cannot be stored in there unless the charge cycle life will be drastically reduced so you want these around 70 degrees Fahrenheit and they will be very happy the next thing is that you cannot charge these batteries when the internal cell temperature is below freezing if you try to charge these batteries when they are frozen or 32 degrees Fahrenheit or zero degrees Celsius they will be internally damaged and again you can't use them anymore but if you live in a cold environment you can easily make an insulated battery compartment input a 12 volt or 24 volt on heater pad and I talked about that on the website so check that out if you need to know more if you are building this for a very cold temperature environment in the final consideration is cell balancing so these lithium iron phosphate cells when use for solar at low seer ratings will not go out of balance that easily but you have to initially balance the cells and what does that mean so each cell has its own voltage when you buy it right now all of these are around 3.3 volts each if I connect all of these cells in a in series string where the positive is connected to the negative and this positive is connected to the negative where we have a daisy-chain types some of the batteries will have a slightly higher or lower voltage over time this is because each cell has a different internal resistance and when you put heavy loads through the whole battery as a system one of the cells will start to take more of the grunt work than the other cells and it can slowly go out of balance to the other cells and the best way to balance lithium ion phosphate cells is to bottom balance that means that you make all the battery cells the same voltage when they are in a low state of charge and this is very important with lithium iron phosphate because if one of them is a little bit lower than the other ones and both of them are charging and discharging together as a battery bank one of them will dip too low and there will be an over discharge situation so you'll check the voltage of your entire battery bank and you'll be like Oh everything's fine but one of the batteries could be low and you don't even know it so you need to check the balance at a low state of charge it's also recommended to check the balance at a high and a low but with lithium iron phosphate it's more important to bottom balance and we're going to talk about how to do that in this video but once they're all in balance in a low state of charge they will be fine for months if not years I have friends that have been using theirs for three or four years now and they have not gone out of balance at all so if you do a good initial balancing of the cells you don't really need to worry about it I like to check all of the cells in my batteries every four to six months I connect the cell balancer and I make sure everything's good so it seems like a lot but it's super simple once you have this thing hooked up in your system you don't really have to do anything you just build it balance it and throw it in your system so the first thing you want to do when you buy used batteries off of ebay is check them for damage make sure there are no leaks or weird cracks and then you check the voltage of each cell so first one is three point three three point three three point three three point three three point three three point three three point three three point three so if one of these cells was really low and one was really high you need to connect them in parallel so they equalize in voltage if all of the cells that you buy are a different voltage you need to connect them all in parallel and let them sit for about a day and the way we do that is with the bus bars and some screws so let's say this battery is too high and this one's too low what we will do is connect these two batteries with bus bars and let them sit for about a day this is what it would look like if you were parallel connecting four cells if you have eight cells you preferably want him to connect them all in parallel for at least a couple hours so that they can equalize a little bit and after you connect them in parallel for a while check the voltage of each cell and make sure that they are all the same voltage before you connect them in series but in my case these are all the same exact voltage so I'm totally fine just wiring up in series no problem so now that we know that all of these cells are the same voltage we can connect the batteries together and put them in a way that is easy to connect them in a series so for this battery we're gonna put a pack like this and you can see brass and then silver brass and then silver and then for this one we're gonna put it like this and we have silver brass silver brass and this way we have two 12-volt batteries and we can put these two in series for a 24 volt battery I like to build them in packs of four because this is about 30 pounds if you connect them it's 60 pounds and 60 pounds is way harder to lift than 30 pounds and if your batteries do not have silver and brass color look at the positive and make sure it's positive positive positive positive negative negative negative negative you want to have a zigzag so today we're going to use VHB tape and we have pose clamps so wash the sides of your battery cells with rubbing alcohol in a small rag or paper towel and before you connect them make sure that you have them aligned in this zigzag fashion and then cut small strips of VHB tape and put them on the battery cell make sure your hands are clean when you mess with this stuff all right we have our first two cells that we're gonna connect together and make sure that you have brass and then silver and then put them together just like this and then put them on their side and then press down now these battery cells are connected it's actually a pretty strong bond these are like frickin solid this is what our hose clamp looks like you just have to fit it over the whole thing I took a bunch of cheap ones and put them together also keep in mind that these hose clamps obstruct the cells being close to each other and I want to have these cells next to this one if we're building a 24 volt battery so I made a long hose clamp on this side so it can sit flush so that these cells can press up against each other now we have our first 12-volt battery cell bank look at that it's pretty cool now these two batteries are complete so we can connect them with busbars so we need to put these in series and I have them connected side by side so I could put a bus bar between them like this so check this out guys we have 1 2 3 4 in series for 12 volts 1 2 3 4 in series for 12 volts and to create a 24 volt battery we have a positive and a negative we're gonna connect them with a bus bar and then these terminals will be positive 24 volts negative 24 volts so these will be the main terminals of this battery make sure that you hand tighten them for the last little bit you do not want to strip out one of these terminals it will be permanently damaged and you'll have to buy another battery cell and now we're gonna check the voltage of this battery bank we've got 26.5 so this is good if it's another number not around 24 if it's not between like 30 and 24 you have a problem so this battery is almost done but we need to add a balance plug cable and this will connect to our balancer and we will be able to see the voltage of every while we charge and discharge it we'll also be able to bottom balance this battery and this may seem kind of confusing please buy the cable on my website so you don't have to make this yourself like I did because this takes a lot of time to solder all of these little things but what you do is you put the negative on the main negative of the battery bank and then you have the first cell positive second cell positive third cell positive fourths l+ 5th cell positive 6th 7th and then 8th cell and those connect to all of these and on your balancer you're gonna have a negative and then first cell positive second cell positive 3rd cell all the way to 8 and you need to use an 8 s or 8 cell balance lead you can actually buy them already built at a hobby shop and then connect them to your battery bank and this is really easy you just need to make sure that each wire is going to the right one so on mine we will put the black the negative on the main black and then we will see the color is orange and the orange is the first cell positive so we will put it on the first cell positive yellow is second cell positive so we'll put on the second cell positive so you guys get the idea there's also a schematic on my website if this is confusing I know a lot of people get really scared about this but it's really easy to do so first we need to strip these wires so we can put our little connectors on it and because this is the battery terminal bolt we're gonna use these to connect our balance lead to the terminals and this is what it will look like when it's done before I heat up the heat shrink this is the most painstaking process of this whole battery it's such a pain in the butt to do this so be sure to buy the balance lead so you don't have to do all this craziness so start with the negative and put it on the main terminal of the battery that shows negative okay now we have the negative now we need to put the first positive on the first positive of the cell so it's orange so orange is gonna go right here this is the first battery so we've got the negative on the black we've got first cell positive second cell positive third cell positive and fourth cell positive very simple but I know a lot of you guys are going to be intimidated by this part so we're going over it a lot this is what it looks like when all of the battery cells are connected to the balanced lead now we can connected to a balancer and this is an eight-cell balance or most are six or seven cells so you have to get an eight cell for a 24 volt battery just make sure that the negative is in the proper position and then plug in all the other cells okay this is an exciting part so we have 26 volts total and then 3.29 is the first 3.29 a second third fourth fifth six seven eight so we can balance it right now but they're pretty much the same voltage so what we're gonna do is discharge this battery in bottom balance with this balancer but how are we going to discharge this battery now we can discharge this battery I just connected my main inverter for my house system to this and now we're gonna plug in this heat gun also understand if you're not used to 24 volt inverters they make a big spark when you connect them so watch out for that it's totally normal and safe but just watch out they'll probably scare the crap out of you so yeah let's load test this system so these battery cells are almost to the depleted State for bottom balancing we're at three point one three point one three point one three point one three point one three point one three point one so we want to get this down to three volts in three times eight is 24 volts it'll be the total voltage so right now it's at 25 and we need to drop it down to 24 volts when it's resting and there are no loads on it then we will balance the cells and as it gets closer to depletion you want to check the cell voltages to make sure that none of the cells are dropping too low right now all of them are going down together and that's what we want so now I'm gonna deplete it down to 3 volts and then we will do a balance something to understand is wait it's under load you will see the different internal resistance of the battery because there will be a different voltage drop across each cell and that's because they're all different you can see it happen when there's a large load all right now these cells are around 3 volts each so we can do a balance so check this out this is kind of difficult the instructions are really difficult to understand so I'm gonna teach you how to set up a balance mode with this so first we need to hold down the setup menu and then this is the discharge voltage you need to make sure that this is around two point eight to two point nine volts so for me I put it to two point eight but you need to use these buttons to drop the voltage down or up and then once you get it on the good voltage press the setup menu button to leave this setting but it needs to be at least two point eight because it will not balance the cells because these are lower than most other lithium batteries so make sure it's a two point eight volt and then just get out of this menu by pressing setup menu until you get back onto the main screen now this is the main screen now we go to mode discharge and you have to hold this button to enter the discharge mode and then press the button again and it will say max and min and now let it go just don't touch it and it will balance itself right now and you will fill the back start to get a little bit warm and it might take like an hour or something but it will start beeping when it's done and for most people that buy batteries they're similar it should balance in a couple hours but if your batteries are not balancing and one of the cells is really high one of them is really low what you might want to consider doing at this point is taking them all apart and putting them in parallel and then wait till all of the voltages equalize over a day and then put them back together for me because these cells are really close it will only take about an hour for it to balance these and right now you can see the max and the min symbol that means that it's balancing so this is good this is what you want to see when it's balancing and if you're impatient like me you can buy these resistors and put it across the battery cells that have a high voltage because it takes a while and it took like three hours for me to balance and there's still a couple that are too high so I'm going to manually do it this is a big resistor compared to the resistors inside here so you can manually balance this thing very fast let's say my fourth cell is too high of a voltage all you do is put a resistor across the two battery terminals and it will discharge this battery slowly and the best moment for doing this with these three point two volts cells is a 25 watt two point seven ohm resistor and they're only one dollar each so this is very easy and everybody could try this it will start feeling warm and that means it's doing its job watch the balance while it's doing it until they're all balanced so I'm very impatient so I built a little resistor bank that I can connect to each cell and it discharges it very quickly because this is taking a lot longer than I anticipated these are some big cells now this battery is balanced within point zero five volts of each other so that's fine you can sit there and balance it all the way out it doesn't really matter that is plenty good for this size of a battery so a lot of you guys can leave this cable on or you can remove it so it looks nicer it's a pain in the butt to put the cable on so a lot of people leave them on but I don't really have to check it except for every six months or so so I'm gonna remove all of these wires and look at that it looks so much better and now all we have to do is add these little covers to the top and here's the finished product we have the main positive and the main negative and every four to six months use a multimeter and check the voltage of all of the cells and make sure they're within spec so this battery works well with the settings for a sealed lead-acid battery but you can make some modifications to that charge profile so what I recommend is making the charge limit 14 point 4 volts making the temperature coefficient compensation 0 putting float voltage to 13 point 6 volts and then put equalized function to zero minutes another useful thing to note about the lithium iron phosphate cells is they run into higher in a wider voltage range than a lead acid and there's a steeper curve to the discharge so what you want to do is look up one of these charts it will tell you if 14 point 4 volts it's 100% 13 point 4 volts it's 99% and then at 12 point 9 it's 20% so if I want this battery to last a really really long time I would charge and discharge between 90 percent and then down to about 14 percent or 12 point 5 volts so set your battery protect to as close to this as you can and then set your charge limit to thirteen point three volts this is lithium iron phosphate so it should last a really really long time but if you want it to last like decades you could do that manual charge profile as well a lot of people ask me if this will work with the alternator in their RV or van and technically it will if your alternator outputs 14 point 5 volts this will be charged by your alternator but it's a bad idea it's a bad idea to use lithium or sealed or flooded lead-acid with an alternator in a car because that charging system is designed to charge a starting battery and that is not a deeply discharged battery you can damage the alternator in parts of the charging system if you try to charge a big deeply discharged battery because if this or another LED acid is at a low voltage and you're starting battery is at a high voltage the alternator will compensate at the voltage that's in between it's not designed to do that so if you do want to charge this with an alternator and you're really desperate to have that system in your vehicle what you want to do is go to a shop that can install dedicated alternators and find boat alternators that are made for charging deeply discharged batteries if those alternators cost a lot of money but it is possible to do that and it's very Porton with lithium batteries with alternators because they have a lower resistance so whatever your alternator can produce this thing will soak up so maybe you're sealed in flooded lead-acid batteries lasted a while with your alternator and you didn't experience any problems even though it's not smart to do anyways it's a lot less smarter to do it with this because this will just soak all the power that your alternator makes and it will get hot so again use only an alternator that is designed to charge batteries do not use your vehicle's charging system it's not designed for that another thing is people are scared about freezing these batteries and it is something to worry about but it's very easy to make an insulated battery compartment with a black water tank 12 volt or 24 volt heater these things are thermostatically-controlled and self regulated and you literally just put it under the batteries or between the batteries and then you insulate around it and you connect it to power and it will warm up the batteries whenever you need it you can do a low temperature disconnect those ones are a little harder because you have to build them yourself but honestly you could easily build a insulated compartment and it will handle very cold temperatures just fine also short power charging these so if you plug in your RV to an RV park and you get 50 or 30 amp supply and you have a converter if that converter is made to charge a sealed lead-acid battery you can charge for this just fine don't even worry about it at all they also understand that with those Shore power chargers they can charge at a very high C rate and this will just absorb it if you have some flooded lead-acid batteries put a 50 or 100 amp charger to it and the internal resistance is so high that you can't use all of that power with the lithium ion phosphate or any other lithium-ion chemistry battery it will absorb all of it and the lithium iron phosphate typically with the charge cycle life they last a really long time but if you charge them quickly they do not last as long in battleborn actually published some interesting data on it they said if you have a very high C rate charge with their lithium iron phosphate cells which is the same chemistry as these the charge life was pretty much in half or something and then if you're below point 4 C or 40 amps charge rate for their 100 amp hour battery I believe it was in lasted 5,000 cycles so if you wanted to last a long time get a smaller charger and allow it to charge slowly now let's talk about the discharge rate of this battery each of these cells can handle 300 amps continuous discharge so for this whole battery bank at 24 volts and 300 amps it's like 7,000 something watt inverter that this thing can power it's incredible it's really really good so you don't really have to worry about that but you do need to put a fuse on all lithium batteries and in this battery though these terminals are pretty close to each other so I would be very worried if you have any vibrations in the vehicle make sure that these will not touch together over time because that could very well happen if they're that close don't have these cables hugging each other or wrapped around each other have them free have some extra insulation wire wrap something to protect these also make sure that when you're putting the main battery cables to this terminal it's flush with the terminal of the battery you do not want to have any washers underneath it if any of you guys are professionals and you caught me there are a couple washers underneath this if I was building this system for long-term use which I'm going to I'm gonna put some copper washers they can actually handle the current because this bolt on fuse if I were to bolt it straight down it would break it so I had to lift it up a little bit with the washers but what you wanted to look like is this copper on copper the screw and the washers on top don't matter that much because currents not going really through those it's where it's flush between the terminal and the battery lug you need that to be clean you want it to be flat and flush so then all the current can go right into the battery and right out also if you're building this battery you can put these in series as much as you want you can make a 48 volt battery any day but putting them in parallel is not preferred if you have two batteries in parallel you'll probably be okay but if you have more than three or three strings in parallel you're asking for problems because when batteries are in parallel the one with the lowest resistance will take the grunt work it will charge and discharge faster than the other ones so that one will fail first and if you have like four or five in parallel the lowest is going to take the groundwork for the whole battery bank because it's the path of least resistance that's why it's smart with lithium parallel strings to put a fuse on each individual one like the Tesla battery pack that is smart to do because if it does short you don't want all the other batteries damaged because there's this because one string has a short so yet don't put your batteries in more than two parallel strings if you have this one in another one that's okay you can parallel those and you'll probably be just fine especially with the charge and discharge rates but anything more than that I would not do instead you should buy bigger battery cells get those 200 amp power cells and then put those in series instead that is smarter to do with this this is perfect all of them are in series I can check the voltage of all these this will last a very long time so yeah guys let me know what you think there was a lot in this video I was thinking about making a quick fast video but it turned out to be very long so yeah I think we're done here and I'll talk to you guys later please check out the website lots of good information on there about this stuff step-by-step with nice pictures and yeah I'll talk to you later bye

Channel: DIY Solar Power with Will Prowse

Views: 1,343,000

Keywords: will prowse lithium battery, lithium 24v battery, diy lithium battery, offgrid solar battery, #vanlife, lifepo4 diy, diy battleborn

Id: E4pN4DVPOcY

Length: 26min 16sec (1576 seconds)

Published: Wed Mar 06 2019