Don't Waste Your Money On Batteries - The Shocking Truth I Discovered When Testing RV Batteries

agm batteries flooded lead acid lithium which one is best well i had an opportunity to test all of these batteries under laboratory controlled conditions even at different temperatures to figure out which is most cost effective and which provides the most power stick around because the data and the answer will shock you so this is not the original video that i intended to make when we visited battleborn batteries in reno nevada we were there to interview dr dennis ferris the ceo of battleborn batteries and ceo sean nichols about primarily a cold weather charging experiment that they had run comparing their lithium ion batteries to lead acid alternatives now i did a video and blog post analysis all about this study already and i'll put a link in the description below but a lot of questions were asked about it still and this was an opportunity for me to ask these questions directly to battleborn batteries could you explain a little bit about what it was you did in the study well this was really a head-to-head comparison between a lithium-ion battery bank and a lead acid battery bank and we did go to cold temperatures but we also did the experiments at room temperature we did basically a discharge charge discharge um repeatedly at room temperature and then we kept decreasing the temperature down to about 15 degrees fahrenheit now the interview i think was pretty good and i'll upload the whole interview in a separate video but we started talking about battery capacities a bit and sean said this people don't understand it like a person who just buys a regular rv is not going to take the time to research it what they hear is this is a lead acid battery i can use 50 of the power you cannot use 50 of that power unless you're under certain recommended really stringent circumstances of you discharge this battery in 20 hours at this temperature then you can get 50 percent and take it down to 12.2 why'd you do the study at 12.2 because we have two very reputable manuals from lead acid battery companies agm battery companies that say 12.2 is a 50 depth of discharge it's pretty hard to argue with those facts we're only going on the information that they give us and i hate to say it's a lie but for years they've been telling everyone you go buy a lead acid battery they tell you yeah you can use 50 of the power in there all right prove it show me under what circumstances a family living in an rv for a weekend can do that can discharge a battery over 20 hours i've never seen it happen this was a pretty bold statement i thought so i asked a few more questions and i asked if i could see their testing setup and their data and this is where the video took a 90 degree turn not only did they offer for me to see their setup but they offered for me to reconstruct the experiment they would pay for the experiment but allow me to have full control over it including whatever parameters i wanted to test naturally as an electrical engineer this piqued my interest so we extended our stay in reno and we went about setting up a whole new test now i have a background in power systems and i've built large battery banks for both industrial and residential applications but i've never really done much load testing of the batteries so i was very interested to see what i could learn from these experiments we built a set of two identical test benches with fully programmable charging capabilities to charge the batteries per the manufacturer's recommendations as well as a set of low variant high power resistors for a static load to discharge the batteries into we set up an automatic voltage cut out system with a relay powered from an external power supply as not to impact our experiment and recorded all the data into a national instruments dac using a set of accu-amp current transducers and high-accuracy voltage divider resistors to log the data directly into a computer now as for the batteries we got six different sets we got two sets of battleborn lithium batteries two 100 amp hour standard batteries and two of their brand new heated batteries to test out in the cold weather environments now these heat batteries are really neat and something that i wanted to talk with sean and dennis about in the original interview primarily because they solve all the problems of cold weather applications for lithium-ion batteries these are awesome batteries with the latest and greatest technology and if you want a chance to win a set of these batteries you're gonna have to stick around to the end of this video as we are giving away two of these awesome batteries to one lucky winner now for the lithium batteries we only tested a set of two of these batteries or 200 amp hours capacity but for all of the lead acid batteries that we acquired we got a set of four of the batteries usually around 400 to 450 amp hours of capacity now battleborn's original study only used two lead acid batteries which is still a fair comparison because this is what most rvs come with but i wanted to do something a little different we're testing a larger lead acid bank against a smaller lithium bank it's really going to be a little bit closer to apples to apples and give the lead acid batteries the benefit of the doubt as for the lead acid batteries we acquired three sets of agm batteries we got two sets of what are considered some of the highest quality and really the most expensive agm batteries that are commonly used in rvs and boats and also one much less expensive agm battery that can be purchased at most retailers across the country we also got a set of very inexpensive 6 volt flooded lead acid batteries that are a pretty common choice for backup power systems because of their cost and we wired two of them in series to create a 12 volt battery bank now because of some of the data that we got from these batteries i'm not going to disclose the actual brands of these batteries we're just going to call them agm 1 2 and 3 and flooded for our 6 volt flooded set now we are sharing the cost of each of these battery systems along with the manufacturer's rated amp hour capacities and what the recommended cutoff voltages for 50 and 80 percent were respectively also we're sharing what the manufacturers expected life cycle for these batteries are all of the battery information and in fact all of the information that we acquired from this experiment is going to be available over on the accompanying blog post along with a full detailed analysis of all the data if you want to get access to the actual data that we recorded i'm going to make it available over on this blog post i warn you it's millions of cells of data and a lot of computers hate even opening these excel spreadsheets but if you want to run your own analysis i'm going to make the data available to you as well now i'll get into a little bit of an analysis of all the data here and the tests that we ran in a minute but a lot of you are here to find out what we discovered so here are the main takeaways from our experiment the first and one of the most interesting things that we got out of this experiment is that none of the lead acid batteries we tested were able to make their rated capacities at the stated voltages per the manufacturer this means that at a 12.2 or 11.8 volt cutoff the capacity that the manufacturers said the batteries should make was not what we got at all even with an extremely low discharge at 2 amps per battery well beyond the 20 hour discharge that the manufacturers state is what you should be able to get out of the batteries this truthfully shocked me i expected the batteries to perform much better than they did and it seems that sean is right we're buying batteries saying that we can get x capacity out of them but we're not this data was room temperature tests and interestingly the lithium batteries that we tested at room temperature actually exceeded the capacities that they are rated for now a lot of you might say well why don't you completely kill the batteries discharge them all the way down and see how much capacity you get out of them well you're not supposed to do that with lead acid batteries but we did we took our two best performing cost effective batteries and we discharged them down to nine volts and amazingly they still didn't make their ratings this is an unreasonable test however and we're really curious about what you can get when you set a cutoff at a recommended limit and none of them could provide the power that they said they should now i'm talking power here but what i'm really interested in seeing is what hour or how much energy the batteries could actually deliver watt hours and amp hours are not the same watt hours is actually a measurement of energy whereas amp hours is a measurement of charge and they're not apples to apples another interesting thing we discovered from this experiment was comparing the amp hour capacity of the lithium batteries to the amp hour capacity of the lead acid batteries when we actually integrated out a watt hour capacity or how much they delivered the lithium batteries produced more energy this was because the voltage of the lead acid batteries sagged or sat lower than the lithium batteries so we actually got more energy out of the lithium batteries for the same amp hour capacity this is one of the reasons i'd love to see batteries rated in watt hours instead of amp hours because then we could really have an apples to apples comparison and it's more useful to know how much energy we can get out then how long we can run an amp for now because i integrated out watt hours for each of the batteries that we tested we were able to take the cost of the batteries and divide it by the watt hours they provided to get a dollar per watt hour cost this revealed even more interesting data about the batteries primarily that the more expensive the agm batteries the worse they performed cost wise these batteries perform so poorly that at a 12.2 volt 50 cutout the lithium batteries were cheaper than the expensive agm batteries up front dollar per watt hour equivalent if you were to use the full capacity of the lithium-ion battery this was at the best case low discharge rate but if we increase the discharge say at 80 amp discharge or 20 amps per lead-acid battery the lithium-ion batteries performed cheaper than almost all of the lead acid alternatives up front no life cycle cost considered this is because of the puket effect that the lithium ion batteries don't suffer from as much so if you want to use high load applications like we're doing in this rv everything that you see including the camera and the computer here are being powered by lithium ion batteries right now they are going to be more cost effective than trying to run a heavy load on a lead acid battery bank the only way to get around this is to way oversize the lead acid battery bank but then you're just throwing away even more money looking at the dollar per watt hour cost it turns out that the cheaper the lead acid batteries the better they perform the more money you're getting for the energy you're getting out of them in fact the flooded lead acid batteries were by far the cheapest option off the shelf per the energy they could deliver now this all changes once again once we start to look at the life cycle cost because we have real world data of how much energy we could get out of the batteries we were able to take a look at how much energy we should be able to get out of the batteries over the lifetime of the batteries or per how many cycles the battery per the manufacturer should be able to perform we took the energy that the battery provided at its stated cutoff and multiplied it by the number of cycles that the battery was supposed to get at that stated cutoff to get a life cycle dollars per kilowatt hour cost this is very telling information because the cost of the lithium-ion batteries turned out to be two to six times cheaper than any of the lead acid alternatives this is per the life cycle or how much energy you can get out of these batteries but it doesn't even include replacement costs of the batteries or labor so the battleborn lithium batteries over the entire time of owning them are going to be way cheaper for the amount of energy that you can actually get out of them compared to pretty much any lead acid counterpart now in our cold weather tests we found out that the lead acid batteries had such a low voltage sag because of the cold weather that we had to lower our cutoff voltages to even get any reasonable amount of energy out of them specifically at high loads we ran some real world tests that i'll show you in a little bit here we plugged in a microwave and coffee pot to cold batteries to see how they would perform and we had to significantly lower the cutoff well below what's recommended to actually get any significant amount of performance out of them we also found out that we really needed to change the charging parameters of the batteries to the manufacturer's cold weather charging specs to get them to perform at this rate at all so it's very important if you do want to run lead acid batteries in the cold that you change your charging parameters which is a bit of a pain and then charge them change them back once the temperature warms up we also tested out the battleborn heat battery which performed amazing in the cold it performed as if it was warm because well it was the one drawback that we discovered from this battery is that it does self-consume some of its energy we ran the batteries test at 10 degrees fahrenheit completely uninsulated really worst case scenario for this battery and while it performed well it didn't provide as much energy because it's self-consumed to keep itself warm so if you want to run heated lithium batteries i recommend you add insulation to give them the best case scenario give them a chance to retain that heat a little bit better now those are the main takeaways of the experiment but let's dive into the data a little bit here and take a look at each individual experiment first we ran the tests at room temperature we discharged the lithium ion batteries down to their 11.8 cutoff and we were able to see that we provided 108 percent of their rated amp hour capacity at a 8 amp discharge or 4 amps per battery or 102 amp hours of their rated capacity at an 80 amp discharge or 40 amps per battery the lower discharge is due to the pukert effect that we talked about more in the cold weather charging video now for the agm batteries we first cut them out at 12.2 volts and this is where we were able to see that none of them made their 50 capacity they made about 30 to 40 percent of their rated capacity at the very low discharge eight amps divided by four batteries two amps per battery they should have performed better than this but at the 80 amp discharge they only made about 15 to 20 percent of their rated capacity and this is partially due to the pukert effect where they're not going to provide as much energy and secondly due to the fact that they have a larger voltage sag which is going to hit that cutoff sooner we did record before and after the test to see where the voltage ended up and we were able to see that with the low discharge current we had very very little voltage recovery only about 0.1 to 0.2 volts max whereas at the 80 amp discharge it could be upwards of a volt recovered so we didn't get as much capacity out of the batteries at that 80 amp as we would expect anyway but if you have your inverter set to cut off at 12.2 this is what you're actually going to get next we lowered the cutoff voltage to 11.8 or what the manufacturers considered the 80 discharge once again they didn't make their 80 percent in fact we only got about 60 at the very low discharge and 30 to 40 percent at the 80 amp discharge now due to the time that all these tests took some of these tests were extrapolated data and you'll see that in my chart here extrapolated means that we ran it down to a lower voltage cutout and we integrated the data to get what we should have seen if we cut the voltage out at say 12.2 or a higher voltage cutout in addition to the amp hour capacity we calculated out the watt hour capacity for each of the batteries at this room temperature and then calculated out the dollar per watt hour cost we were able to see that the battleborn batteries with a full discharge would cost us about 57 cents per watt hour delivered per run and the agm's the most expensive agms cost us about 78 cents at a 50 percent discharge and 42 cents at that 80 percent or 11.8 volt cutout so not a whole lot better than the lithium batteries interestingly if you compare just the agm batteries it's interesting to see that the agm3 or the cheapest agm we purchased actually performed almost as well if not better than agm-1 the most expensive and supposedly the best performing at least you would assume so it's also clear when we look at the dollars per watt hour that the flooded lead acid batteries are by far the cheapest option so if you really can't afford the lithium going with the really cheap flooded lead acid six volts is still not a bad option if you want to save money truthfully however you'd really want to save that money until you could afford lithium for the next time because when we take a look at the life cycle cost per kilowatt hour things really get interesting whereas the battleborns cost only 9 cents per kilowatt hour if we extrapolate a 50 discharge the cheapest even the flooded lead acid at a 12 volt cut out because their voltage cutout is lower cost us 19 cents per kilowatt hour delivered over their life cycle the agms came in much more expensive at 65 cents 52 cents and 39 cents per kilowatt hour delivered that's four to six times more expensive than the lithium batteries and that's if you can trust this manufacturer cut out data when digging around trying to get some real world life cycle data i was able to get some charts that battleborn had run early on when testing out their batteries to figure out what their life cycles were and they actually tested it against the same agm2 battery manufacturer they were cycling these batteries over and over and over to see what their capacity degradation was and they compared agm2 to their lithium battery and interestingly granted they used a much higher discharge about 25 amp versus we only ran at 20 ampere battery max the battery had a discharge to 80 of its capacity in only slightly over 100 cycles so if you're using these batteries hard this kilowatt hour per life cycle cost is going to look even worse for lead acid batteries this is really best case scenarios under very light load conditions laboratory conditions when they get fully and properly recharged every time if you're using it on a solar system that's not getting it all the way through that absorption cycle every time you're gonna see results more like this and they're gonna cost you a lot more truly wasting your money whereas the lithium batteries really should not matter they shouldn't care how charged they get and they should perform very stable to these numbers over their life cycle one last thing of interest in the warm weather data is that when we extrapolated out the watt hours or how much energy the battery produced and this is the amp times the volts per second and we integrated that out over time we're able to figure out how much energy the batteries delivered per amp hour and when we compared 216 amp hours of agm3 compared to the 216 amp hours delivered by the lithium-ion batteries we got 2808 watt hours delivered by the lithium compared to watt hours delivered by the agm at the same exact amp hour capacity and that is because the voltage stays up on the lithium so much longer this actually took the lithium all the way down to where the voltage tailed off so again kind of worst case scenario for the lithium so interesting to see that amp hours to amp hours is not apples to apples we really can't compare them together we're truly getting more energy out of the lithium than the agm batteries now for the cold temperature testing we tested all the batteries in an 11.8 volt cutout and this is because primarily the voltage will sag so much higher we could extrapolate out what a 12.2 volt cutout would look like we first tested the battleborn lithium-ion 100 amp hour standard battery and then the new battleborn 100 amp hour heated battery we can expect a capacity loss in cold weather because the chemical reaction in the battery slowed down but it was interesting to see that the lithium-ion batteries had a very similar capacity loss to the lead acid batteries compared to their original capacity all of them were around 75 to 79 of their original capacity so they lost about 20 at 10 degrees fahrenheit this was at the low discharge however looking at the high current discharge the lead acid batteries lost considerably more capacity only providing 40 and 60 of their original rated capacity the already derated capacity that they produced from their original capacity whereas the battleborn produced about the same 78 of their original rated capacity this is due to the pukert effect how it accelerates in cold weather applications i talked about this phenomenon in my original cold weather charging video but since then i've also discussed it with a friend of mine matt knight who runs a blog called adventurous way he did a great analysis of this cold weather phenomenon over on his blog and he actually charted out the usable capacity of the lithium ion batteries versus the agm batteries at different discharge characteristics in the temperature and you can clearly see that the pukurt effect is much much more pronounced in cold weather for lead acid batteries versus lithium ions so it's not that unexpected that we see the capacity of the lead acid batteries decrease so much further when we try to put a load on them compared to the lithium an interesting thing to note about the lithium is that the heated lithium battery provided less capacity than the regular battery at the low discharge current the reason for this is that we turned on the heat of the battery eight hours before we discharged it so it was actually providing energy into the battery to heat itself up and actually use some of its own capacity and then the 8 amp discharge was a very long run so it was heating itself over a long period of time consuming some of that energy it only produced about 68 of its rated capacity for that long run however at the 80 amp discharge when we're using it much much higher it produced almost 90 percent of its rated capacity why well first of all because it was a much shorter run so it wasn't running for as long not consuming its energy for as long and also because it kept the temperature of the battery so much warmer it was able to provide more power than if it were cooler again over that shorter period of time going to give us more capacity while the battleborn heated batteries do not require insulation and will perform well down to below zero degrees fahrenheit adding insulation or at least keeping them in an enclosed compartment will help them perform the best possible in cold weather environments for the agm batteries we then warmed the temperature up to 25 degrees because we wanted to test a more reasonable cold weather application to see how they performed we also changed the charging parameters to compensate for the cold weather let acid batteries need charging parameter compensation which we didn't do at the original 10 degrees fahrenheit to get best performance in cold weather applications and this is basically a higher voltage charge you kind of overcharge the battery if you will because it's not going to provide as much current and have a much larger voltage sag when we ran these tests at 25 degrees we saw something very interesting we didn't really see any capacity benefit from the 10 degree test at the low discharge however when we did the high capacity discharge and we compensated for the cold weather we actually got very similar to performance to how the batteries originally performed at room temperature what this means is to use lead acid batteries in the cold you really need to have temperature compensation enabled on the charger you need to go in and manually change the charging parameters for the temperature that the batteries are at if you don't do this the batteries are going to perform a lot worse with the batteries in this cold state we also wanted to see how they would perform in a real world condition so we've already learned a lot about how these batteries perform at different temperatures room temperature cold but what about a real world scenario so we went out and got a microwave we've also got a coffee maker back there the batteries are cold they're at 25 degrees let's plug these in and see if we can heat something up on a cold morning off these batteries now we didn't use the inverters for a load most of the time but we did put a plug in so that we could plug a coffee maker and a microwave into the batteries and run them at the 25 degree state of charge and this was with the compens the cold weather compensation for the charging application on the battery so really best case scenario in how the batteries would perform so that's about eleven two yes yeah that's the eleven two area that's the way we're cutting off beforehand yeah but i think that initial initial heating caused us to go why'd you kill why'd you die i didn't i didn't kill it i didn't kill it what happened we hit 7.8 i'm sorry all right so this cutoff was 11.8 yes technically 80 of our battery capacity we got half a cup of coffee so the 11 8 could only make half a cup of coffee now that's a setting that would probably be pretty common to really get that cut off so you're not taking the batteries too low but we dropped the voltage to 10.5 cut off on the inverter now and we're going to see how long we can run it for i expect that it'll work but the question is going to be what does the voltage do and how low have we actually taken the batteries after it runs no four minutes well i have one very hot cup of coffee here so we were able to get the agms to work only if we lowered the voltage to about 10 five on the cutoff of the inverter however this is something that i guess you'd really have to keep in mind if you want to use agms under a high load you really need to figure out i'm gonna go below the recommended 50 or 80 cutoff voltage but you need to if you want to get that energy capacity because once the load is removed we see the voltage come considerably back up still above what they consider the 50 cutoff thinking about it you could probably program a voltage alarm or something to give you an alarm over time on like a bmv voltage meter or something you can set up an alarm and it would be it would beep every time you have a high load but basically it's okay to exceed that but you don't want to have it exceeded at a steady state and if we set the inverter to cut off at 10.5 and it's running overnight you're not monitoring it and it goes down to that you have significantly damaged these batteries so i think we learned a lot from this real world uh test it's very interesting the data that we got out of it though they had no idea that a microwave would vary so much in its current and the coffee maker too it cuts off cuts on it's a big heavy load that really isn't steady at all when we removed the load the voltage did bounce back considerably up to about 12.3 12.4 volts even though we had been running a heavy load for about seven minutes but again the voltage was sitting way below that 11.8 volt like 11.2 or so so how you would actually manage that low voltage cut off without damaging the batteries and making sure that they're still bounced back to a good steady state i'm not exactly sure how you do that but if you want to run lead acid in the cold that's really what you need to do for high load applications now after a month and a half of testing we were running out of time but there was one final test that we wanted to run before we left so we have got some really interesting data so far and these tests have taken us a long time to run and i'm almost out of time i have time for one more test and what i want to do is i want to take our best performing lead acid batteries we're going to do the cheaper agms and the flooded lead acids we're gonna run them at room temperature as far down as we can go we're gonna take them down to nine volts i don't ever recommend doing this with a battery because it's terrible for the battery itself it's terrible for the electronics in the coach but for the sake of testing we're gonna run these way down and then i'll be able to take a look at the data and figure out where the true fifty percent should be on that data and if they can even make their capacity i'm curious to see at what voltage they make their capacity 100 capacity on the agm should be around 11.6 to 11.5 volts and on the flooded's a little bit lower more like 11.2 we'll see if they can make their capacities at those voltages and where that 50 should be we had determined that agm3 and the flooded lead acid batteries were the most cost effective batteries to own so these are the batteries that we wanted to do the kill it test that we called it where we took it all the way down to 9 volts now amazingly the agm3 rated at 105 amp hours per battery provided us with almost 100 percent of its capacity when we dropped it all the way down to nine volts and we recorded the entire voltage and where it dropped off in this chart interestingly the flooded lead acid batteries the voltage tanked off a lot faster and it provided us less current but you can see that the voltage bounced back so much higher than with the agm batteries we also calculated where the 50 discharge point was for each of these batteries with the agm batteries it was at 12.0 volts whereas with the flooded lead acid batteries it was at 11.9 volts this is where we would have had to cut the batteries out to get that 50 discharge now this was done at the 8 amp very low discharge rate so again really should be best case scenario and they should have provided their rated capacity while it may sound good that the battery got almost its rated capacity at this 9 volts again you really don't want to run the batteries this low because it's so bad for the batteries you will lower their life cycles even more and their costs per life will be even lower and also electronics hate running at that really low voltage it's not good for the systems they'll draw higher currents not good for anything in the coach or boat so this was all a lot of data and if you really want to dive into it over on our blog post i'm going to have the full analysis and the data for you to peruse through the biggest takeaway of all this for me is that buying a lead acid battery is really a waste of money if you want to get the most energy possible out of the batteries yes the lithium may seem like an expensive upfront cost but especially if you compare it to thinking about an expensive agm battery there's no sense in wasting your money on those batteries lead acid batteries are so susceptible to environmental conditions to temperatures to charging profiles to discharging profiles that they're just not reliable to be used in a power application these were laboratory control conditions where we made sure to meet all of the manufacturer specifications for each of the batteries and this frequently doesn't happen in real world environments so the batteries are going to be damaged or their life cycle is going to be limited even faster in a real world scenario i was truthfully surprised to see that lead acid batteries did not meet their ratings and i think from this data i can conclusively say that there is no situation in which a lead acid battery would outperform an equivalent lithium-ion battery in a power storage application and i truthfully can't recommend any lead acid battery over lithium-ion either for the sake of use or even cost now you may ask if there's any situation in which a lead acid battery should be used and there is one that i can think of lead acid batteries are great at providing very high discharge currents for very short periods of time and as long as they are recharged through their absorption cycle very quickly they have pretty good life cycles an application that works like this is a starting battery in a car all you need is a very high current to turn that engine over and then they are immediately recharged don't rely on the starting battery in the vehicle however to provide auxiliary power for any significant loads if you need additional loads in the vehicle install a separate lithium-ion battery bank to provide that house power one last thing to consider with lithium ion batteries you can get away with a lot less the two battleborns that we compared in all these tests to the four lead acid batteries they truthfully perform very comparably so we can really consider half the lithium and look at the cost in that regards instead of having four lithium ion batteries to four lead acid batteries now as i mentioned earlier if you're interested in a chance to win a set of the new battleborn lithium-ion heated batteries you're gonna have to head over to our website at mortonsonthemove.com backslash giveaway and enter your information before january 15th for your chance to win this is an incredible setup that's going to provide lots of power in all temperature conditions and we're not just giving away two batteries it's always important to have a means to figure out what capacity those batteries have so we are going to include a victron shunt with the batteries that you can install to figure out exactly how much capacity they have in them i'm super excited about this giveaway there are multiple different ways that you can earn entries and i hope to see you all over on the website as always thank you so much for joining us if you liked this video give us a thumbs up and hit that subscribe button also head over to ourmortonsonthemove.com website to get access to all this data learn more about this experiment and lots of other solar battery and rv topics

Channel: Mortons on the Move

Views: 703,184

Rating: 4.8254638 out of 5

Keywords: Full Time RV Living, RVlife, mortons on the move, rv solar, rv battery, best rv battery, lead acid vs lithium, battery testing, rv electrical, off grid solar, solar power battery, best solar power battery, off grid power, rv solar power, energy storage, how to install rv battery, how to rv solar, rv information, best boat battery, batteries for boats, boat battery

Id: iy3hga_P5YY

Length: 36min 57sec (2217 seconds)

Published: Sun Jan 03 2021