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Battle Born LFP impressions

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  • Ampster
    replied
    Originally posted by PNjunction View Post
    ........
    Why?

    Aging and use of say a single battery, and two years later you tack on a new one ... the more "mature" battery with cycles on it will take more of the brunt of the load from cycle to cycle. And affect the new one. Just because it is LFP doesn't make it significantly different than lead acid in this regard.
    ......
    I understand how this is a killer with lead acid, because lead acid doesn't tolerate partial charging. Lithium doesn't care if it is partially charged.

    On the other hand with the BMS on each pack if the weaker battery gets full before the stronger one and the charger keeps going won't the BMS on the fully charged weak battery take it off line? I can see how that might put unnecessary wear and tear on the BMS. If it were to fail to open the HVD, then I can see how the older weaker battery could get over charged.

    I agree with your premise that it is not a good idea to put batteries of different vintages in parallel. I am just wondering if these batteries might be a little more tolerant than Lead acid?
    Last edited by Ampster; 03-06-2020, 01:52 AM.

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  • PNjunction
    replied
    Incrementally expand like lego's as time goes on? Not recommended. Best to do a power-budget and build accordingly at the outset. Maybe ask them if a particular application in mind would be ok for that.

    Why?

    Aging and use of say a single battery, and two years later you tack on a new one ... the more "mature" battery with cycles on it will take more of the brunt of the load from cycle to cycle. And affect the new one. Just because it is LFP doesn't make it significantly different than lead acid in this regard.

    Can you get away with it? Sure - depends on the application. And what sneaks up on you here is the flat discharge curve where you think things are rosy - unlike lead-acid where voltage drop differences are more accute when you do this.

    Since most of us can't determine internal resistance, IF one is going to do this, then be sure to watch terminal temperatures if nothing else. Get one of those temperature guns with a laser-pointer in it. Welcome to more maintenance beyond the usual. Entering *very* diy territory.

    I do love how they supply the bolts and adapters, and are adamant about using specific torque! Not just finger tight. Assuming one has those tight, even so, it is just not good engineering to mix and match old and new. From AA's to 48v monster banks. Unless you are prepared (and your wallet can take the hit) of replacing the weak-link (older affecting the newer) over and over.

    Sadly, that's a utopian vision. Nobody in the industry does this, unless it is for emergency temporary restoral. Long term -not good - but some find out the hard / expensive way.

    So now the smaller 50ah "learner battery" they have is still just that. An auxiliary if you will. Might come in handy.
    Last edited by PNjunction; 03-05-2020, 10:15 PM.

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  • Ampster
    replied
    Isn't one of the advantages of these drop in batteries that you can incrementally expand your pack with more parallel batteries without worrying about the same imbalance issues you would have with Lead Acid chemistries.?
    Last edited by Ampster; 03-06-2020, 02:26 AM.

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  • PNjunction
    replied
    Good points!

    To actually make a dent in the lead-acid game, LFP, the easiest of lithium cells to make, should be much lower in price compared to non-lfp types. But that's not going to happen - the consumer doesn't really know the difference between nominal 3.2v lfp cells, and nominal 3.7v (non-lfp) types. Lowering the price of LFP would require an across-the-board industry sea-change.

    So what's left is the usual capacity vs cycles which consumers can understand.

    Which leads us to: We all know that merely doing cycles "sausage-factory" style cycling over and over during testing is not really accurate as Prof Jeffrey Dahn has pointed out. Especially if one is going to demonstrate a warranty like after 8 years. But at least it seems these guys UNDER-spec their cells, which tends to help if one is going to be a battery-hoarder. Not that I recommend that.

    My own years long testing of my prismatics showed that despite meticulous care, sure enough batteries age. Even LFP. So it would not be reasonable to say purchase one now, store it for 8 years - even properly - and then expect the 3000 cycle life span immediately afterwards. Ie, only buy a battery when you actually need it.

    But overall, I think that there is much less of a chance of your average punter not properly maintaining one of these, as compared to undercharging and sulfating a lead-acid battery. I know I get the most out of my lead-acid purchases, but my neighbor - not so much.

    High upfront cost - I see something similar to say how Enersys products are handled. Kind of a filter to prevent a casual person ignorant of the very basics of batteries trying to power his air-conditioner with a 12v inverter that he got from the auto-parts store - and wired up with finger tight random bolts. The warranty guidelines are similar.

    It's hard for me - mr "no bms", fully cognizant of how mosfets can fail closed and all the balancing issues can rear their heads - to be cool with this on a consumer basis.

    In other words, for the average Joe who has a life beyond battery mainenance, maybe their smaller 50ah battery would make a good "learner battery" for solar use. If you can swing that (upfront costs of course), then maybe you'd be ready for a larger series / parallel bank down the line.

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  • SunEagle
    replied
    It looks like those batteries are not as expensive as other Li chemistry.

    I guess my big question is will they provide 3000 cycles with a 100% DOD?

    If so that 100Ah 12V battery can get you a source that will provide power for its life at less than $0.28/kWh.

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  • PNjunction
    started a topic Battle Born LFP impressions

    Battle Born LFP impressions

    Just some impressions from what I've seen online. I like what I see, but I am not an owner. I am only evaluating it from a "stand alone" drop-in, NOT from a series/parallel standpoint.

    After reviewing several teardowns, and interviews online, I must say I like what I see. It's what I do from a diy LFP-ninja standpoint.

    Up front: Look, a BMS is a fact of life. *I* can do without, but for normal people who have neither the time, energy, or skill to deal with lfp battery systems, and subject it to any weird load under the sun, it's mandatory. It protects the user, the product, and most importantly, the WARRANTY. I've read it, and it is reasonable. The BMS is intended to keep the product usable in unskilled hands, and perhaps cut down on the reprehensible battery-scammer who wants "free batteries for life" with purposeful abuse.

    A future owner should read the manual and warranty. Basically these guys just want you to enjoy the system, and oh yeah, STAY in business. Standard stuff.

    Cylindrical cells that are matched. I certainly get it here. Unlike a prismatic where a bunch of flat-packs are connected internally, there is no way to QC that unless you are the actual manufacturer. It is easy for a poorly performing flat-pack cell to "hide". And sometimes, puff-up under abuse and take out neighboring cells. Cylindricals with their inherent already tight-compression, tend to just die on the vine. And now it is much easier to do your OWN QC and matching to reject outliers so they can't hide amongst the others.

    Under-spec's: I love how they are not cutting things so close to the edge in stated capacity. One thing we as solar guys know is not to cut things too close. Give yourself an edge to accomodate errors in power-budgets, component aging, and so forth. Think about how the system will perform years from now, not just at initial startup. The system is obviously top-balanced, and by under-specifying capacity, this gives you a little breathing room for a little ragged balance down below so as not to hurt the cells - despite the bms lvd. I get it - I understand.

    Proprietary wrappers - if they want to stay in business they won't be using junk. BUT, by not specifically identifying the cells, this allows them not to be locked into a single supplier. I get it - I'd like to know from an enthusiast standpoint, but then there's the "I want to stay in business" standpoint too, and not get hoodwinked by supplier / chain issues. From seeing what they are doing, it certainly doesn't look like they are going to bet the farm on junk cells and shoot themselves in the foot.

    Solid engineering: Something that I mentioned many years ago - these aren't some guys just tossing cells rattling around inside the box, wired up with speaker wire and calling it a day.

    Temp sensor - I love seeing the temp sensor that will allow for sub-freezing DIScharge, but stop you from trying to CHARGE under freezing conditions. Again, protecting the product from possible user abuse - accidental or otherwise.

    Common Sense Tips: Overall LFP knowledge is evident. Simple warnings like if you hit the bms self-protect, don't let it sit around like that or further discharge (internally beyond the bms cutoff) will hurt them. Solar - tip about not letting the system go into total bms disconnect, otherwise your solar system may disconnect and not reconnect properly seeing what it thinks is a battery removal.

    Obviously, here the thing to do is not use your bms-disconnect as your SOLE LVD all the time.

    I've reached kind of a real-world middle ground here regarding drop-in's. I can do it myself, but if my Uncle were to need a 100ah LFP, I wouldn't feel guilty recommending a Battle Born.

    I could go on, but basically from a drop-in standpoint, from what I've seen - I'm impressed. It's how I would build it if I had to give one to someone who is not a diy-maven.
    Last edited by PNjunction; 03-05-2020, 05:03 PM.
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