November 22, 2021
Alrighty! Time for my review. As a techie, I always like to do a bunch of research before I buy a product, and then share what I learn with the community via the review process! That way I can save y'all some time in finding such information yourselves. =) First, let's talk about advertised capacity. Don't believe what those other reviewers are telling you. Who knows what standards they are using! According to my handy dandy (and highly trusted) load meter, my 300AH batteries are each offering just over their rated capacities (see attached picture for an example of one particular battery). So no issues here! Quite the technological leap forward when compared to lead acid battery capacities, I must say, which can't be safely discharged past a pathetic 50% SOC! Next, let's talk about battery longevity. Unlike lead acid batteries that must be kept topped off at all times (or they'll sulfate and die) lithium batteries don't suffer from any negative side effects when partially charging/discharging them (and in fact, PREFER to be partially charged/discharged). Thus, I have decided to charge my new LiFePO4 batteries daily to about 80% or so. You see, research has shown that by only partially charging/discharging LiFePO4 batteries, their lifespan can be extended to between two and three times their advertised rating. So for example, if one only regularly cycles their LiFePO4 batteries up/down by no more than 50% at a time (by going back and forth between, say, 75% SOC and 25% SOC) than said batteries can theoretically be charged/discharged a total of 8000+ times rather of 4000! Of course, like all batteries, calendar age has its limits. But nevertheless, the point is, partial charging/discharging LiFePO4 batteries can SIGNIFICANTLY increase their lifespan. So, to achieve this, all one has to do is overprovision their battery bank accordingly, and set the proper charging algorithms as explained next... Now, let's talk about ideal charging parameters. My batteries are housed in an RV, with a solar system charging them, but the principal is the pretty much the same regardless of battery application. To achieve any particular SOC, I have learned that all one has to do is lower their charger's boost voltage accordingly. So for me, I have found that setting a boost voltage of 13.6V yields me that 80% SOC to which I prefer, once I hit that voltage. Actually, let me just go ahead and bust out all my charging parameters for y'all, so you can see exactly what I mean: 15.0V = Over Voltage Disconnect Voltage 14.6V = Charging Limit Voltage 14.2V = Over Voltage Reconnect Voltage 14.6V = Boost Voltage (To Achieve 100% SOC) * * One day a month I set my boost voltage to 14.6V to ensure that proper internal cell balancing takes place, which evidently doesn't start occurring until cells reach 14.2V or so. 14.4V = Boost Voltage (To Also Achieve 100% SOC) 14.2V = Boost Voltage (To Also Achieve 100% SOC) * * Technically, to achieve 100% charge capacity, 14.2V is good enough, and is theoretically a safer setting to use than 14.6V so as to ensure that any imbalanced cells in the mix don't get as easily overcharged (while still allowing internal cell balancing to occur). In the end, I may indeed settle on 14.2V once a month rather than 14.6V. I'm still on the fence about this one. Maybe I'll settle on 14.4V and call it good? 14.0V = Boost Voltage (To Achieve 90% SOC) 13.6V = Boost Voltage (To Achieve 80% SOC) > MY IDEAL SETTING 13.5V = Boost Voltage (To Achieve 75% SOC) 13.4V = Boost Voltage (To Achieve 70% SOC) 13.6V = Equalization Voltage (Ultimately Irrelevant, But Must Nevertheless Be Set To ≥ Boost Voltage) 13.8V = Float Voltage (To Hold 100% SOC) 13.4V = Float Voltage (To Hold 80% SOC) > MY IDEAL SETTING 13.2V = Boost Reconnect Voltage 12.4V = Low Voltage Reconnect Voltage 12.0V = Under Voltage Warning Reconnect Voltage 11.6V = Under Voltage Warning Voltage 11.6V = Over Discharge Reconnect Voltage 10.8V = Low Voltage Disconnect Voltage 10.4V = Discharging Limit Voltage 10.4V = Over Discharge Disconnect Voltage 0.8 Secs = Over Discharge Delay Time Equalization Duration = 0 Mins (LiFePO4 Batteries Are Not Supposed To Be Equalized, EVER) Boost Duration = 10 Mins * * Boost duration is not really needed when charging LiFePO4 batteries, but my charge controller needs something, and it offers a minimum of 10 minutes, so I took it. I mean, technically, one COULD set a longer boost time in conjunction with a lower (safer) boost voltage, so as to still achieve 100% SOC if one so wishes (but whereby getting to that 100% SOC will simply take more time to accomplish). So maybe 40 minutes using a boost voltage of 14.0V, 30 minutes for 14.2V, or 20 minutes for 14.4V. Ultimately, the only thing one needs to avoid doing is holding their batteries at 14.6V for ANY amount of time, so setting the absolute minimum boost duration for that particular voltage is most ideal. Low Temperature Charging Cutoff = 5°C * * This will be the most ideal (and safest) low temperature cutoff for most people, but can nevertheless be modified accordingly based on information presented in the next section... Time for the fun part! Let's talk about charging near freezing temperatures. It's actually not a "hard cliff" as a lot of technical literature (and reviews) seem to claim it is. Indeed, one day I finally came across the perfect table to explain precisely how fast, and at what temperatures, one can safely charge their LiFePO4 batteries at! [Please now refer to the charging table I have attached to this review.] So, in my particular circumstance, I was quite surprised to learn that I can still safely charge my 1200AH battery bank in, for example -10°C temperatures, by using a charge rate of no more than 120 amps/hr to 60% SOC, 96 amps/hr to 80% SOC, 72 amps/hr to 90% SOC, and 60 amps/hr to 100% SOC! Of course, I'll never see those charging rates come out of my particular solar panel setup, as I top out at roughly 80 amps/hr in the summer, and 40 amps/hr in the winter. So I'm more than set here! The important thing to understand is that, contrary to popular belief on the subject, one CAN -- and quite safely so -- charge their LiFePO4 batteries near, at, OR EVEN BELOW freezing temperatures, as long as they don't exceed the specified charging speed per AH capacity as presented in the table. Pretty stellar, huh! Of course, for extra-super-overkill safety, I went ahead and installed individual water tank heating pads under each of my batteries anyways, which were then wired to four independently controlled external thermostats, all so as to ensure than I never even come close to risking damaging my batteries throughout the course of winter. Important to note here is that going the external heating pad route is actually quite superior to using internally-heated LiFePO4 batteries that several vendors now offer. For one, my batteries can start being heated long before the sun comes up (thereby rendering them ready to accept a charge right at sunrise rather than several hours after). And two, my four paralleled batteries stay 100% in balance to each other 100% of the time (because of how they don't draw power from themselves on an individual basis in order to heat themselves, but rather cumulatively draw power as a whole from the bank as a whole, via my 12v bus). And so, with my handy heating pads, used in conjunction with my handy overall bank temperature sensor offered by my EPEVER charge controller (which is set to disable charging at 5°C or less), I have achieved cold-temperature-charging nirvana that those internally-heated LiFePO4 batteries surprisingly can't compete with! Anyways, time for a summary of all my ideal charging/discharging and best maintenance practices: - Do not be concerned that charging "sits" at 13.2V or so for an extended period of time. This is normal, and NOT an indication that a battery is "failing to take a charge." Indeed, as long as it is consistently absorbing the specified current given to it (as objectively measured via shunt or the like) the battery is acting normally. You see, LiFePO4 batteries have an extremely flat charging (and discharging) curve, so when charging, they'll absorb at 13.2V from, say, 20% SOC to 60% SOC, then slowly move to 13.5V at 75% SOC, then quicker to 13.8V at 85% SOC, then quickly to 14.0V at 93% SOC, then very quickly to 14.2V at 97% SOC, then almost immediately to 14.4V at 99% SOC, then instantly to 14.6V at 100% SOC. Indeed, as one can see, that last 15% of charging is the "steepest," only occurring over a span of 15 to 30 minutes as I have observed (and depending on the strength of the applied current, of course). - Avoid using lead acid chargers (unless you know what you are doing). This is because lead acid chargers tend to operate in stages, which LiFePO4 batteries do not require (especially the float stage). Also, lead acid chargers usually charge at lower than ideal voltages (which CAN be acceptable, depending on what final SOC you want, as mentioned above). But generally, they're worth avoiding. Also especially worth avoiding is charging via direct wire to a typical vehicle alternator, as most alternators don't know how to limit their charging current in this type of situation, and thus, will QUICKLY burn themselves out! Of course, one can still safely charge via alternator, though, as long as they use a "DC to DC" charger to accomplish the task with. - When paralleling, first charge each battery separately to full, then parallel each to each other for a day, one by one, until all are paralleled, then start using them. - Also when paralleling, ensure that all batteries are balanced to between 0.02V and 0.05V of each other. - When combining (either via parallel and/or series) it's best to combine products of substantially similar (if not identical) brand, age, condition (cycle use), and capacity. This ensures that all batteries uniformly accept the same charge across the board (otherwise, some batteries will surely get overcharged, while others undercharged). - Keep battery temperatures between 5°C and 45°C (20°C ~ 30°C if possible). - Keep charging/discharging rates under 0.5C (0.2C if possible). - Fully charge (to 100%) and discharge (to 0%) once a month (to allow for proper cell/battery balancing to occur). - Avoid regularly cycling below 10-15% SOC unless absolutely necessary. - Avoid regularly cycling above 85-90% SOC unless absolutely necessary. - Avoid leaving in a highly charged (>90% SOC) or highly discharged state (<10% SOC) for very long. - Avoid floating at 100% SOC no matter what, as this will KILL LiFePO4 batteries quicker than anything else! But, if one must float at 100% SOC (as some converters invariably require), at least float at a voltage of 13.8V or less. LITERALLY NEVER FLOAT LIFEPO4 BATTERIES AT 14.6V, EVER!!! And now for my finalized SOC table, according to voltage, that I have built based on multiple sources: VOLTAGE / SOC 13.50V = 100% 13.40V = 99% 13.30V = 90% 13.25V = 80% 13.20V = 70% 13.16V = 60% 13.13V = 50% 13.10V = 40% 13.00V = 30% 12.90V = 20% 12.80V = 10% 12.50V = 7% 12.00V = 4% 10.80V = 1% 9.50V = 0% Of course, don't forget to add 0.1V ~ 0.2V to each parameter to account for voltage drop, depending on how far away you're measuring from. And the above table is for resting voltages, too, by the way, so subtract 0.2V ~ 0.4V from each parameter based on how recently (and/or strong) a charge was applied to the battery (i.e. account for surface charge), OR add 0.2V ~ 0.4V to each parameter based on how recently (and/or strong) a load was applied to it (i.e. account for surface discharge). Also, I should note that I did test my batteries for low-voltage cutoff, and they DID each cutoff at around 9.8V, which I was told by the manufacturer is within spec. So no worries here, either! Also important to note is that 9.8V was measured at the terminals, meaning if one takes "surface discharge" into account, the actual voltage to which the BMS boards cut out (at the cell level) was likely a true 10.0V, which is indeed the official lowest voltage LiFePO4 batteries can safely be taken to without permanently damaging them. Well that's pretty much it, for now! Overall, I am 100% pleased with my super major four 300AH LiFePO4 battery purchase, of which I have had running for a couple of months now without a single hiccup, and to which I plan on running for the next 10-20 years without issue as well. In more ways than I have fingers to count with, LiFePO4 batteries are simply orders of magnitude better than their lead acid counterparts. I'm so glad the cost for them has come down over the years, and is now within reach for most of us off-gridders! As long as you treat them well, I strongly believe they will return the favor. =) PS- Ampere Time tech support has been great, for the few questions I have had for them. They also honored several 2% off coupon codes that I got from them, one for each purchase. Honestly, one of the better companies I have had the pleasure of doing business with! Go Ampere Time! PPS- Don't forget to buy a few DC meters w/ shunts, and install them accordingly so that you can keep track of precisely how many watts you're putting into / taking out of your battery bank! Absolutely priceless information can be gleamed with such tools. Indeed, I have four hooked up right now so that I can know, at all times, a) what's coming in from my solar system, b) what's going to my battery bank, c) what's coming from my battery bank, and d) what's going to my 12V system. UPDATE: Well it's been about a year since I bought these bad boys, and I am delighted to say that they are still going as strong as ever! I honestly can't tell a single difference in them now compared to the day I bought them. They still hold the exact same capacity, and still read accurately both voltage and watt wise. Glory hallelujah! My deep cycle RV battery woes are finally over. Thank you Ampere time for making such a downright excellent product! SECOND UPDATE: Still going strong another year later! In fact, I have now purchased several more of the 300AH variety for use in my second rig. =)
August 17, 2023
Put these in a razor crazy cart. So much better. Last forever charge much quicker. Wish we would have bought these sooner.