Just so you know, this page contains affiliate links. My solar charge controller already measures battery voltage. I generally use this voltage reading just to make sure my battery isnt close to being fully discharged. Then we used our appliances for a couple of hours, ran the lights, watched a movie, and the battery was at 13.2, which read 90%. For example, recall that when I checked my batterys voltage with a multimeter at the battery terminals, I got a voltage reading of 13.23 volts. Battery monitors track the amount of amp hours consumed to accurately estimate the state of charge. A voltage sensor gives the controller a more accurate voltage reading, especially in solar power systems with long wire runs. If a picture is worth a thousand words, then a solid graph or chart ought to be worth more. But when I connected my battery to an MPPT charge controller, the controller measured 13.0 volts. The normal operating range is between 12.7V and 12.06V. I can just use it to check battery capacity.. Other appliances that have to have 12V will simply stop operating, like the inverter. It also didnt help that the solar panels, which came with the van, werent functioning properly (as they discovered later). I say this because there are some lifepo4 batteries (e.g Battle Born Batteries) that enter low voltage disconnect (LVD) to protect the battery from over-discharge. The new 24v chart has a typo No biggie.. It is the upper limit the Controller will allow before calling a fault(I understand this is common practice). Also, it may be helpful to know some brands call the boost stage the absorption stage. Once a battery enters sleep mode, it needs to be woken up. Many LiFePO4 batteries can discharge 100% of their rated capacity every time with no ill effects. But they hadnt really mentally calibrated the previous energy expenditure with their available charge and projected use for the night. Battery voltage changes depending on charge and discharge rates. There dont seem to be many folks doing this. Looking back at the State of Charge chart above, the battery only dips below 12V below 9% capacity. Thanks for the heads up Monty. float needs to be set low or turned off if possible. Within their first night, they uncovered a disconnect between what they expected and what they got. I have two x 200AH Amperetime Plus batteries. But, being easy to read doesnt necessarily make it easy to understand. Sometime in the middle of the night, our fan just quit running all together, full stop. endobj Id check your batterys manual for its recommended settings. most of us are either recreational or 3kw or less so 12 volt systems are sweet spot for value? No, they hadnt done anything wrong with their installation, nor with their choice of appliances or equipment. Will a jump start from a 12 v battery reset it or should I open the battery and disconnect the BMS then reconnect? It should have instructions for waking up the battery if it has gone into sleep mode. Thanks for the resting voltages at various levels of charge. But beware that it can be quite inaccurate. A batterys voltage drops when connected to a load. Note: For more about solar battery chemistry and a full cost-benefit analysis of the 4 most common deep cycle solar batteries, check out our blog from December 2020. Why did it go down so quickly, did we do something wrong? Your solar charger will put out 14.6 but you will not see it till the battery is charged as you will see battery volt plus charge volt influence. That's worse than a lead acid battery, and it doesn't at all match (to my eye) the SOC discharge rate on the Spec sheet. Required fields are marked *. Now, with our Lead Acid battery, under similar conditions, the fan would just slow down, sometimes to a comically low level, but it never quit. My current obsession is DIY solar power projects, which I've been building since 2020. (Dont forget to disconnect your solar panels from your charge controller first!). Hi there, thanks for the article! Now I need some clarification, as to how the float state works, on the Rover MPPT CC. www.renogy.com/content/files/Specifications/BATT-LFP-12-100.pdf. Yeah I think its pretty much what you said 12v and 24v batteries are the sweet spot for a lot of small-scale / recreational solar power systems. Hi, I'm Alex. their affordability over the short term and their installation options. Only two months but so far so good. They are made by connecting eight 3.2V LiFePO4 cells in series. Maybe the data collect will reveal something useful. Hi Will. The reason being exactly what you said in PV systems, output is always changing and can drop to zero during cloudy, rainy days (not to mention nighttime!). j6^}[$quN_ZjcSH` qi0XW[U-Q05WqjV( W'~R Glad to hear you found the page helpful, John! Not really. Your Victron should already have a preset charging profile for your battery that you could use. Getting familiar with YOUR system, YOUR appliances, and YOUR lifestyle takes some time and a good deal of practice. Ps boost or bulk is 14.6. float is 13.6/8, Hi, Love your charts.. How are you measuring the voltage? What is Boost Time for a LiFePo4 battery ?.should it be zero? So, lets return to Sarah & Marks van. <>/Metadata 569 0 R/ViewerPreferences 570 0 R>> So I am not sure how it will ever get to 14.6 unless I set one of those stages to 14.6. LiFePO4 batteries dont need to be float charged because they dont leak charge the way lead acid batteries do. % It suffers from all of the problems mentioned above, plus its done while the battery is connected to loads and chargers. Am wondering about using 12 volt vs 48 volt batteries. %PDF-1.7 Hello Alex However, many manufacturers recommend discharging only 80% to maximize battery life. Deep cycle batteries just dont go from full charge 100% at 12V to 0% charge at 0V, giving off a consistent rate of discharge in an even amount of time. Agree, it happened to me (LVD) and I simply connected my 12v portable car jumper battery box to the dead Battleborn battery for a bit. Im soon going to upgrade my mobility scooter from AGM to LiFePo4 batteries. To get an accurate estimate of battery capacity based on voltage, you first need to disconnect any loads and chargers from the battery. I started Footprint Hero to help people reduce their environmental impact. Note: Your battery monitor or smartphone app might give you a slightly different reading depending upon its calibration and the temperature of the battery. So the limit in your battery manual may not be exactly 10V. It usually involves jump starting it with another 12V battery. Ive seen some brands recommend 30 minutes, Ive seen some recommend 0, and in the photo above the brand recommends 120 minutes. They are made by connecting four 3.2V LiFePO4 cells in series. It is not accepting charge and I suspect the BMS is asleep. I find that this helps reinforce the connection between what we expect and what we experience. I brought it out of storage and measured its voltage with a multimeter. You can buy individual LiFePO4 battery cells online. The lesson here is not let your battery get that low Hi prizfindr, so what resting voltage does your renogy Li measure as any know SoC? They rarely make sense for small-scale projects. Is that high enough to call it fully charged? So a 12V 100Ah LFP battery has as much usable capacity as a 12V 200Ah lead acid battery. Theyre a drop-in replacement for 12V lead acid batteries, and a great upgrade. Heres a printable version of the above chart: 12V 100Ah LiFePO4 batteries are currently some of the most popular for off-grid solar power systems. This morning the battery is at 13.3v. 48V is more popular for larger solar systems. But a Lead Acid battery dips below 12V at just under 50% capacity. I set my Solar controller to the setting in the manual (the page in your photo). They left home with a full LiFePo battery (14.2V, 100%) that very shortly became 13.6V, also 100%. Check the battery manual. That would be nice, but the laws of Physics (or at least those who interpret them and make voltage scales) did not have the average consumer in mind. It displays a lot of information at a glance, including a nice percentage of charge on the battery. Plus, LiFePO4 batteries have a relatively flat discharge curve from around 99% to 20% capacity. That correlates to a roughly 80% state of charge. When the sun rose, the fan would speed up as soon as the light hit the solar panel. In the meantime, you can click, Your All-in-One Energy Monitoring and Off-grid Smart Living Center, * Shop Renogy ONE and related accessories. x=ioF4hW4L:l D[Bld_n{uHVQ>AYwunwX_4Cfj/_gw7z^^W3dI')~O,H.^b0,KX""52%}?~,+9W UY*4dnrv9?gwsVw^OGv0gjh$s&cP"K9~h[d(5b_;I}rMRY cQT9tL2#24US%3A=EZS1oP@xJW '`UreKfhD". h:ZaaRzJ0D\~INOHD10Sp2OYdmt+gbc%]*\J'&|r1uwIOck[n)OB5A=a;oIkDR" )hxq:A+ny, R/u*Nwrd8[uXkcyoR~}l> That correlates to a roughly 30% state of charge a difference of 50%! You may think that the battery is dead, but really its just sleeping. The normal operating range is between 13.0V and 12.05. Thanks! Is this true? Compared to both FLA and SLA batteries, the range and depth of discharge are much greater, allowing for significantly more available watt-hours per cycle. Alex endobj Of course, if youre building an off-grid system or something or similar scale, it may make sense to use a 48v battery bank. And weve all likely driven that car in which the first half of the tank seems to last forever, but the final quarter evaporates in an instant -- leaving us desperately searching for a gas station. After all, voltage drops under load. They are made by connecting 16 3.2V LiFePO4 cells in series. Low-voltage cutoff is also called low-voltage disconnect, which youll sometimes see abbreviated LVD. The difference between 70% capacity and 40% is a mere tenth of a volt. With PV systems, the output from an inverter charger could vary appreciably hence the current presented to the battery would fall (sudden cloud cover etc). They are fully charged at 3.65 volts and fully discharged at 2.5 volts. Thanks for all the good info. I.e. Before they knew it, they were at 12.8V and heading toward the low voltage cut-off of their inverter. stream Dont freak at the beep! They simply needed to get some real-life experience with their system and battery so they could align their expectations with their experiences. If they had run the water heater while driving or while they had full sun on their panels (giving the battery a chance to charge back up), they wouldnt have had any problems. Because their app showed 90% when they started the movie (and probably also plugged in a smartphone to charge), they thought they had plenty of power. Remember those? But, when I was looking at the collected data, from the 'Solar Station Monitor' program, I never saw it go into an idle state while the solar panels are active. They had done all the calculations, ordered the solar equipment, and even completed phase 1 of their solar upgrade. Alex, found this page very helpful in understanding our newly installed LFP batteries, that replaced our Lead Acid batteries after 8 years of reliable use. I just installed in my RV a single 300AH Ampere time battery and replaced my converter with a new lithium charge converter. We cant wait to attend one. The reason this happens is that the LiFePo battery is designed to deliver its nominal charge of 12V throughout its entire discharge cycle. For some real-life strategies on how to maximize a small solar powered system, see tip #3 in this blog. So a 12V motor, like the fan, will simply slow down if its getting less than its nominal voltage. As it slows, it slows the rate of discharge on the battery until it's simply turning like an unenthusiastic sign spinner at a sleepy intersection. It was when they decided to run their water heater that became the real problem. Usually it involves a jump start from another 12V battery. But if SOC did mean something how much voltage would you expect a battery that was allowed to run down to 30% have? Welcome Guest. The Forum has been moved to support.renogy.com. Hardly constant current but does this really worry the battery? I believe the manual says that the Charge Voltage is 14.6V and later User 14.6V lithium charger and Recommended Charging Voltage: Between 14.2V to 14.6V. Ampere Time 12V 100Ah LiFePO4 Deep Cycle Battery, How to Wake Up a Sleeping LiFePO4 Battery. That is useful info. Whether Lithium Iron Phosphate (LFP or LiFePo) batteries, AGM, or Flooded Lead Acid, the battery's internal chemistry will determine the voltage status range between full and empty, as well as the depth of discharge (DoD) available for each type. Copyright 2022 Footprint Hero LLC. Because of these factors, it can be hard to estimate their state of charge from voltage alone. DIY lithium battery builders will also measure the voltage of used (and new) battery cells such as LFP cells and 18650 lithium batteries to see which are good and which are duds. Compare your measurement to the right voltage curve above, or the state of charge chart in your battery manual. When we refer to 12 volts, we are referring to the batterys nominal charge -- this is a fancy way of saying that these batteries operate within certain parameters, around approximately 12V. As the battery charges a higher volt will be see until 14.6v is achieved then the controller will go into float mode. Note: These charts are all for a single battery at 0A. Is it a problem that they ran their water heater? Some connect via Bluetooth to your phone so you can check your LiFePO4 batterys capacity in a mobile app. Based on the charts, Id estimate my batterys state of charge was somewhere around 80%. Though when the time comes, Ill use the voltage chart from whatever brand batteries I get. Hey Stephen, there is no minimum charge rate for LiFePO4 batteries. My 200Ah LiFeP04 battery has discharged to 11.5v when shown on Bluetooth BMS screen. 24V lithium iron phosphate batteries are another popular option for solar power projects. endobj So my 100ah 12v lifepo4 battery says the charged voltage is 14.6v and nominal is 12.8v. I keep reading that once a lithium battery is drained that low, it is very unsafe to recharge. The DC Home App, through the BT-2 Module, is an awesome tool. A fully charged 12V LiFePO4 battery will have a charging voltage of around 14.6 volts and a resting voltage of around 13.6 volts. If this is the case, the process for waking your battery up will probably be included in the manual. The BMS should detect when the battery voltage falls below 10 volts and enter a sleep mode to protect the battery cells from over discharge. Havent had mine for too long either (3-4 months) but so far so good. When we thought our LFP batteries were losing too much charge too quickly, we are according to the tables provided. Of course, this was music to the ears of some Battle Born owners on the forum I was on, Renogy only produces a discharge curve, and not a chart (like Battle Born), so it's difficult to do an apples to apples comparison. In fact, some brands state the cycle life of their batteries based on 80% depth of discharge (DoD). But, keep on, keepin 'on because the benefits of solar freedom are worth the workand youll have some awesome fodder for that next dinner party. 1 0 obj ~Sarah & Mark. For Flooded and AGM, this is 50% (50% of capacity); for LiFePo, this is 80% (20% of capacity). Charging limit is not charging voltage. Shari Galiardi & David Hutchison have turned their higher education backgrounds, desire for life-long learning, and thirst for adventure travel into writing, photography, video production, and public speaking tours from coast to coast. And a charge controller is a load. Here are LiFePO4 battery voltage charts showing state of charge based on voltage for 12V, 24V and 48V batteries as well as 3.2V LiFePO4 cells. As an Amazon Associate I earn from qualifying purchases. Doing this will help you get your head around what these numbers mean for YOU. 12 volt units are very common is it a scale issue? Your email address will not be published. LFP batteries in sleep mode can have very low voltage readings, usually less than 5 volts. For the rest of the weekend, they left the water heater off and managed to run all of their other appliances without any further problems. Let the battery rest for a little while I usually wait 15 minutes and then measure its voltage with a multimeter. When we upgraded to our new Renogy 50 Ah LiFePo battery back in 2019, we had one strange experience. <> To any new user of solar batteries, this learning curve is all too common, as is the familiar panic that youve hooked up something wrong when the jolting sound of your low voltage alarm goes off -- believe me, weve been there. Then 30 minutes later, the inverter gave us the low voltage alarm, and everything kicked off. The battery is already at rest and not connected to anything. But doesnt say what charging voltage I should use, what would you recommend for setting the charging voltage? If you make a purchase after clicking on one, at no extra cost to you I may earn a small commission. Just minutes before, it had been running full speed, and then nothing. Known to their friends as simply Shari & Hutch, you can learn more about their full-time, solar-powered adventures on their website at freedominacan.com. Whats with the 14.3 I read about? If you use this method and want to make sure its as accurate as possible, you can buy a battery voltage sensor, such as the Renogy Battery Voltage Sensor or Victron Smart Battery Sense. Hooked it all up and let it charge overnight. Sign up for exclusive offers, original stories, events and more. Id look in your batterys manual. My MPPT charge controller failed and my lifepo4 lithium 100ah battery now reads 3.7 volts. They are fully charged at 29.2 volts and fully discharged at 20 volts. Your email address will not be published. Pardon my French, but WTF? The low-voltage cutoff of many 12V LiFePO4 batteries is around 10 volts. And do you still have loads connected to the battery? Nice job on solar systems advice. The real benefit of these batteries is their affordability over the short term and their installation options. But it does not charge at 14.6 volts. so `nO"5x7{ C2K'. If I were to connect a solar panel and start solar charging the battery, its voltage would instantly jump. This chart, which weve combined together from many online sources, will help you understand the differences between battery types and their appropriate voltage range and percentage of charge. Note: Some batteries have higher cutoffs, such as 10.6V. But dont rely too heavily on the percentage of charge. The next day they drove to their friend's house, which charged their battery back to 13.2V via their Dual Input DC to DC On-Board Charger and then plugged in to finish charging with their AC to DC charger. Would like to store energy to cover power outage. Cons: Must disconnect all loads and chargers and let battery rest. This will save you research time with deciphering terminology, understanding chemistry, and making an intelligent battery decision that may save you big money down the road -- not to mention the headache. You can either buy an off-the-shelf 24V battery or pick up two 12V batteries and connect them in series to make a 24V battery bank. I have a Victron smartsolar 100|20 mppt charging it at the moment. For example, I own the Ampere Time 12V 100Ah LiFePO4 Deep Cycle Battery. This plea for understanding came to us in an email a few weeks ago from some friends who had just taken their (new to them) van out on the road for the very first time. When we see our battery status go from 100% to 80% over 2 hours of use, we might expect to have 8 more hours at the same usage rate, but thats not the way deep cycle batteries work, nor how they discharge. Note: Consult your batterys manual for its recommended charging parameters. 3.6 volts for lithium iron phosphate. Can you tell me what a minimum charge rate for LiFePO4 would be? I find it too inconvenient to disconnect everything once the battery is in use. 3 0 obj Individual LiFePO4 cells have a nominal voltage of 3.2 volts. I then compared this number to the 12V LiFePO4 state of charge chart above, as well as the one in the battery manual. All of this info is great, but what we all really want to know is, how long can I run my instant pot, laptop, TV, whatever before I run out of juice? Our best advice is to make some notes about how long it takes your battery bank to drop from 100% to 75% to 50% (or 20% if you have LFP) under normal daily usage. You can connect cells in series and parallel to make LFP batteries with your desired voltage and capacity combinations. For those who really want to nerd out, a 500A Battery Monitor may be the way to go. Create an account with us and you'll be able to: We will be upgrading chatbot's functionality to provide you with a better experience.

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