diy solar

diy solar

New here, looking for battery recommendations

flyinglotus1983

New Member
Joined
May 15, 2020
Messages
10
Hi,

I'm building my first solar power system, and I'm looking for battery recommendations.

My use-case is hurricane preparation, at my house which is on the Florida east coast (not an RV or mobile setup, but the solar panels will be mobile, not permanent). We have plenty of sun, no trees, and a huge lawn to throw solar panels down on the ground, if the need arises. My wife and I hate gasoline generators, and we're ready to make the jump to solar, and hopefully never look back.

So yea, this is my first solar power system. I'm starting out with a Renogy 100 watt monocrystalline panel, their suitcase model with the built-in stands. I'll buy another one in a month or so, and might double that to a total of 400W before next season. For now though, just having 100 watts is better than nothing, it's a start. I'm hooking this one panel up to a Victron 100/15 MPPT. Now I need a battery. I'd like to start with 100 amp hours, because anything less seems pointless, and anything more is unaffordable. As far as what I'll be powering, I've got two main use-cases. Low-power (<50 watt), for long durations, for up to 24 hours, stuff like fans, portable refrigerators, lights... The second use-case is high-power (1500 watts) for a minute or two, to make coffee in the morning. Most everything will be DC except for the coffee which would be through a large inverter.

My preference for batteries would be DIY LiFEPO4. I can't afford a Battle Born or similar brands, I'd greatly prefer the DIY approach. I've got about 20 years of experience with battery systems and electronics, so no issues there. I'm really just looking for recommendations on a battery supplier for this specific application.

I'm currently looking at four of the blue 100Ah Fortune cells that Will Prowse recommends, but after shipping, they're $600. And I'd still need a BMS, and at that point, they don't really seem that cheap to me. Are there any comparable cells out there, possibly on Aliexpress, that will sell in this quantity range? Or any group buys or other sites I should look at? One store in particular looked promising, Orient Power (Zhuhai OTE Electronic Technology), but most of their items are minimum quantity of 10, or just as expensive as the Fortune batteries above, but longer lead-times.

As alternatives to new LiFePO4, I'd also be OK with used batteries, in any size or shape, as long as they're cheap. $600 would be my absolute limit, but $400 or $500 would be much easier on my financial situation. Any suggestions would be appreciated.

Thanks!
 
I got a quote from Amy at Xuba for four 280Ahr LFP batteries for just under $600 delivered to my doorstep in Northern California. I am sure you can find something less expensive but the freight might be the same because a box is a box even though it might vary in weight. The quote was shipping by sea, which was going to take 30 to 40 days.
 
I got a quote from Amy at Xuba for four 280Ahr LFP batteries for just under $600 delivered to my doorstep in Northern California.

I googled a bit, I came across the Shenzhen Xuba store on Alibaba, and a 48-page thread on this forum. They've got smaller batteries as well, but my god, that's a sweet deal. I'm still reading through the thread.. But I assume these are legit?

And one other question, never thought I'd be asking this one.. is it possible that 280Ah would be too big for my setup? Is there such a thing as too big? I assume they'll just take longer to charge, and should last longer, right?
 
My use-case is hurricane preparation, at my house which is on the Florida east coast (not an RV or mobile setup, but the solar panels will be mobile, not permanent)
If this is a drag out of the damaged house, emergency power setup, you probably don't NEED a BMS. In this type of situation (and this is largely a empathetic guess, i know), i would think you'd be managing your batteries yourself pretty closely.

Also, I am wondering why you are buying tiny solar panels. Sure they are easy to store and pull out of the garage, but they are expensive on a watt basis, require more wiring and in the case of the suitcase models, not very robust or efficient.

There have been a number of folks from florida that have found huge panels in the 300 watt+ range for what i recall as costing in the $150 range. One or two of these big panels, a SCC like you describe (i love the Victrons), the battery setup like you describe (but maybe closer to 200ah) and you have a solid emergency system to keep your refrigerator and other electronics alive indefinitely.

Good luck, you are way ahead of most in your preparations!
 
If this is a drag out of the damaged house, emergency power setup, you probably don't NEED a BMS. In this type of situation (and this is largely a empathetic guess, i know), i would think you'd be managing your batteries yourself pretty closely.

That's a good point, I'm going to be keeping a close eye on them the whole time. If they get low, I'm able to power everything off to save them. I don't think they'd ever be operated in freezing weather. And for balancing, I do have a really nice CellPro RC charger with balancing adapter, if they get really out of whack. I think this means that I should prioritize getting a decent battery and inverter, and then get the BMS last. I do eventually want to have one, for peace of mind. The one I'm looking at is the OverkillSolarBMS, it's $109 on Amazon, or cheaper direct from China.

Also, I am wondering why you are buying tiny solar panels. Sure they are easy to store and pull out of the garage, but they are expensive on a watt basis, require more wiring and in the case of the suitcase models, not very robust or efficient.

Lol, I guess it's really relative, the 100W panel seems huge to me, but I just started researching this a week ago. I guess it's a starter panel, but I do really like the portability, we do tailgating a few times a year (well we did before the covid lockdown of 2020), and would like to bring it camping sometime as well. That's really a secondary priority though. But I think I've already been bitten by the bug, so there's no doubt I'll end up with larger panels down the road. I'd cover my whole roof if I could afford it. I drive an electric car, my heart's in the right place. In time, I suppose.
 
And one other question, never thought I'd be asking this one.. is it possible that 280Ah would be too big for my setup? Is there such a thing as too big? I assume they'll just take longer to charge, and should last longer, right?
That is a good question that highlights the advantage of Lithium batteries over Lead Acid technology. Lead Acid batteries need to be fully charged all the time and they self discharge so they need to constantly be trickle charged. The last part of the charge cycle is inefficient with Lead Acid and it is important to match solar output or charging capacity to the size of the battery.
That is not the case with Lithium so there is no such thing as too big for a particular setup in the same way it is with Lead Acid. As mentioned above you may want to match your generating capacity to your expected minimum loads. Then the size of the Lithium battery just becomes a reserve that can be maintained at a reasonable level.
 
I guess it's a starter panel, but I do really like the portability, we do tailgating a few times a year
Great, things like this are things to consider going forward. For your tailgating, will you actually need solar or just your batteries? If camping, what will your power needs be daily?

I drive an electric car, my heart's in the right place.
Yea, this is the dream we all have, to drive with free energy. But in reality, will your car be near your solar panels when the sun is shining? If not, then you store in batteries and transfer the charge in the evening (lots of levels of inefficiencies here).

Sounds like you are a smart guy. Think this out to the physical level of how and when these things are actually used (like your drag out emergency power setup).

Lastly, you did not mention an inverter. I assume your emergency setup (this is my primary use at home, not including the RV), is to keep your refrigerator going and your phones/computers running. You will need a pure sine wave inverter in the 1000w-1500w range. Knowing your refrigerator startup surge current is handled by your inverter and actually testing it BEFORE the emergency will be the key to this all working out for you.
 
Great, things like this are things to consider going forward. For your tailgating, will you actually need solar or just your batteries? If camping, what will your power needs be daily?

Lol, that completely depends on how many batteries I end up with. My first LiFEPo4 was 15Ah, that would last me a day, maybe? One thing I find that you run into, the more power you have, the more you end up using it. So even if I had 300 amp hours of batteries, I'd probably still need some panels, for long trips. Some of the road races I go to, you get there on a Monday or Tuesday, and the race is on a Saturday, and you leave Sunday. The older I get, the less I want to rough it in a tent with minimal supplies. Camping turns into glamping. Our neighbors at these races, that have been doing it longer than us, they bring everything. I mean, kitchen sinks, PA systems, above-ground swimming pools... Things get elaborate. Think of it like a redneck Burning Man. Used to be all generators, but a lot of the RV guys are doing solar now.

Yea, this is the dream we all have, to drive with free energy. But in reality, will your car be near your solar panels when the sun is shining? If not, then you store in batteries and transfer the charge in the evening (lots of levels of inefficiencies here).

At the risk of de-railing my own thread, here goes... Long-term? Tesla power wall, solar roof, or equivalent. Whether the car gets charged from the panels or not doesn't really matter to me, it's 6 bucks of grid-electricity to charge it. I could throw $25,000 at it and probably not be 100% off-grid, for me it's more about trying to be more sustainable, not 100% off-grid. I expect battery prices to come down in a few years, and I will patiently wait it out before I retrofit my house, I'm in no hurry. In the meantime I'd be happy with a few hundred watts of panels and a DIY battery array. That's an improvement from having zero. I will also say that the research I've done makes be more prepared to make those decisions down the road.

Lastly, you did not mention an inverter. I assume your emergency setup (this is my primary use at home, not including the RV), is to keep your refrigerator going and your phones/computers running. You will need a pure sine wave inverter in the 1000w-1500w range. Knowing your refrigerator startup surge current is handled by your inverter and actually testing it BEFORE the emergency will be the key to this all working out for you.

I plan to get a pure-sine inverter, somewhere around 1500W to 2000W. Didn't mention it because that seems really easy, just pick a decent brand and plug it in. No questions there. My refrigerator is a power-hog, it's one of those huge stainless steel ones, 6 amps on the nameplate, but I haven't gotten around to measuring the kWh for a whole day.. But it was already my list of things to do! :) I have a small-ish 12 volt, 50 watt plug-in cooler that will go down to freezing, that's what i would want to be plugged in 24 hours a day. All the perishables go in there, and the beer and drinks can go in a regular 5-day cooler with some ice. So basically it's perma-tailgating until the power comes back on. Which reminds me.. I need to buy a second propane tank before they all disappear..
 
I got a quote from Amy at Xuba for four 280Ahr LFP batteries for just under $600 delivered to my doorstep in Northern California. I am sure you can find something less expensive but the freight might be the same because a box is a box even though it might vary in weight. The quote was shipping by sea, which was going to take 30 to 40 days.
I ended up going with the Xuba 280ah batteries, hopefully no regrets! They ended up being just over $500 shipped to the east coast. That's half as much as a BattleBorn 100Ah, and still cheaper than the Fortune 100Ah batteries that I was looking at. I'm excited. My wife, less so, but I'll take this as a win.

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