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Oh, well, then there's that! LOL! Good thing I posted in the beginner's corner! ;) PHEW! So, I guess the only thing I can do is charge them in series, disconnect the series connection, then discharge them individually or in parallel?

I appreciate all the help and feedback! I ended up just going with the Renogy 100Ah AGM. Here's my setup so far (it's a mess, but still just testing everything before I fully commit). I've got the power-supply unplugged to just test the 12v outlet. I've got a 12v plug (a 3D printed a...

I'm powering this APC Back-UPS XS1500 with two "FULLRIVER 60-CELL LIFEPO4 PACK 18650 12.8V 22500MAH 288WH" batteries. The UPS keeps the LFP batteries at 26.5 volts. I did a test-run with it running my PC setup. The draw was 70 watts average It ran for 130 minutes until I stopped the...

I'm glad to see this discussion here (came looking specifically for it). My main question: Why does it seem there is ZERO discussion on charge cycles with Tesla using LFP? Is it just a function of it being a moot-point because the rest of the car will be dead by then? Also, I don't think I've...

Thanks @kernel for the reply and thoughts! Yeah, that's exactly what I was thinking too. I'm still considering the idea since the likelihood is high that I'll need to replace my SMA inverter soon anyway, and having the entire system on new Enphase inverters would help guarantee I don't need to...

Great stuff, thanks for all that! So, I guess I need to really forget al the LFP hype (at least for this application) and go with AGM sitting at a float around 13.8?

This is SUPER helpful, thanks! It sure would be GREAT if this was clearly spelled-out / written somewhere official that customers could review and reference! So, it's pretty clear that going from NEM 1 to NEM 2 (especially extending for another 20 years) is ideal when compared to NEM 3?

The Renogy AGM battery came today and it was sitting at a nice 12.7 volts. I set the power supply at 13.4v and connected it with a volt and ammeter and (as expected) saw the voltage drop down a little and the current started "high" at about 5 amps, and quickly dropped down lower and lower and...

OH! weird... thanks for pointing that out. is it showing now?

Unfortunately the manual says max solar input for 12V battery is 23V, and my panels are 34.5V :(

For charging I think I'm going to get one of those cheap 12V 10A DC Power Supply Universal Regulated Switching AC to DC Converters: ... and hope I can adjust it as high as 13.8V. If not, maybe I'll just stick with one of the simple adjustable wall-wart AC adapters that is around 2-3 amps.

Thanks for finding / pointing out those graphs! Yup, and this is why you've got me about 91.25432% convinced that I should shift-gears to AGM. My girlfriend (again, this is a project she gave me for her Grandpa) is expecting maybe 2-5 outages a YEAR... and of those, most being only about 1-2...

@Steve_S it's always a pleasure to read your fun and informative posts and replies. GREATLY appreciated! Wow, this is part of the value-proposition I hadn't even considered... in the case our entire property goes down in power (which can happen from time to time in California), I could... in...

OH! I totally get it now!!! DUH! The AC200P has an internal 48v lifepo4 battery pack in it, so it would make sense that the AC charger that came with the unit would also safely / properly charge an external 48v battery pack! VERY interesting and awesome!!! So, while it would be a lot of...

I'm really enjoying this thread! I have a UPS running on a LFP battery and it's been working great. I haven't dove into the charge profile (current, volts, upper/lower limits, trickle, etc.) but from what I've read, it *should* be fine swapping SLA battery with LFP. If y'all have links to...

Thanks! Yeah, I'm thinking more and more about just getting one of Will's suggested "all-in-one" MPP units off ebay.

Long thread, lots of interesting discussion but this sounds pretty solid and dead-simple to me, so I'm sticking with it! :D

@feo here are some posts that help me think that I *might* be ok: (bold is my doing):

All this discussion got me in the mood to search craigslist for UPS, so I'm spending a few minutes on Thanksgiving to pick up this unit for $25 (in the listing he even said "could use new SLA batteries":

Sounds awesome! I've been reluctant to use it on a daily basis since I have no idea on the longevity of the various bits and would hate to burn something out / use something up when I don't really "need" the unit... but then not have it available for the rare times that I do. That said, I...

I love when people take the time to revisit their purchases / experiences over time! All these capacity tests people do are great, but when it comes to proving the claims regarding # of cycles, that's an entirely different challenge all together! I mean, if you're paying xy% more for a battery...

You've got me thinking I might do the same since: 1) I don't really need all that "extra" power 2) The "over paneling" only seems to really work if the entire array is in equal sun, and having 4 panels is increasing the likelihood of one of them getting shade, and pulling everything down with...

The Solar Gods have shined down upon me!!!!!! I don't love the low-wattage old panels my friend was going to give me. Just too many would be required (9 in a 3x3 arrangement), so I was feeling inspired to purses craigslist for some better solar panels. Well, I struck GOLD! Someone was...

Thanks for the quick reply! Have you used it as a kind of 24/7 passthrough / UPS for your CPAP... meaning that you can leave it plugged-in and charging 24/7, while keeping the AC and/or DC on all the time? From what I understand, the Bluetti's will power-off if no current is being consumed...

Surely you know by now the answer to this questions in always "YES!" ;)

Brilliant, thanks for the quick replies guys!!! Since I'm (probably overly) worried about cell longevity, I thought keeping the LFP battery at around 3.3V (which *should* be about 90% full) would be a great way to go... and if I'm using a 100Ah battery, then 90% is PLENTY for Grandpa's needs...

Ya, that's where I'm confused. Most lithium based battery items say to avoid charging to 100% (like e-vehicles, etc.), but the manual for the Bluetti clearly says to charge to full before storing. Maybe that's less about battery longevity and more about self-discharge issues?

Thanks for the replies guys! Sorry I didn't get notifications of them sooner! Wow, that's a REALLY interesting idea! I always just assumed tracking / adjustments would be all-or-nothing. Hadn't even considered a 3x a year approach! Yup, VERY true! I just read that after the annual true-up that...

I'm doing lots of digging! ;) To toss back some love to the owner of this site... Will makes this look so easy! He makes it look SOOOO EASY! ;) I mean... it's pretty tempting to put a few of these Growatt all-in-one systems together (like you mentioned in your post above @Steve_S ) with...

I know Will wasn't really a proponent of this battery, but it's almost too interesting not to try! Also, I just want to say, this was TOO funny and (unfortunately?) is what gets me into a ton of projects that are fun, but completely useless to me. LOL!