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So the BMS. I count 4 options for any starter battery system: 1. Spend more than the cells on a massive BMS rated for the peak current. 2. Get a underspeced BMS and hope your starter finishes before the disconnect timer (usually 5 to 10 s) AND you don’t fry your transistors. 3. Skip the BMS...

Little bit of a odd thread. First someone wants to see a CCA rating on an LFP data sheet, which is not a great sign for someone seeking to design a new high current application from the ground up. If you’re seriously considering this you really need to know how CCA is calculated and be able...

Could be. The website doesn't say "new" so can't really even get mad unless there's a capacity issue. Personally I have very little concern about used LTO in this application. Do you have a link to the specs? I struggled to find much more than that one site. Agreed, plus the risk of an...

These advertise 75C peak discharge: https://srikobatteries.com/product/2-3v-20ah-25c-lto-cell/ And these are rated for 75C continuous: https://srikobatteries.com/product/2-3v-10ah-75c-prismatic-cell/ Impossible to know for sure without more details on the alternator and the LiFePO4 profile...

I don’t think he has either, but he does have two batteries and a desire for more capacity. How should he use them? Parallel? He was hesitant to do that, are we advising that parallel is fine?

Those are good points. I didn't mean to suggest that your comment was a guess - I was referring to the fact that I had to guess what the concern was from the mention of a BMS. He could mitigate the imbalance issue by occasionally recharging the batteries separately with a 12V charger. Kind of...

Can somebody verbalize these problems we’re being warned about? I keep hearing about them, but it’s like they’re a mythical creature that will haunt you forever if you speak their name and we have to guess what they are from context. One such guess based on the BMS comment is the risk of cell...

Sorry for over extending your point. It was a bit hard to parse what you were trying to say. Still, that thread in no way shows which type of water is a more dangerous place to bathe with electricity. And I renew my assertion that fresh water is the much more dangerous place to do that...

Whether or not you think this scenario is dangerous (I agree, probably not a problem) it's a perfectly reasonable question to ask before climbing into a kayak and paddling away from shore with a battery. The consequences of getting it wrong are extremely serious. Sorry you find this a waste...

One of the interesting things about electricity and water is that salt makes it much less likely to hurt you. Fresh water is dangerous because it is somewhat conductive, but not as conductive as your body with all those electrolytes. So the water gets the electricity to your body, then it...

It seems like this guy is just getting started and still feeling out what he needs. Nothing approaching a production system @ 2.4kWh. He wants to know if his experiment is dangerous, which it is not. rmaddy went a bit further than "recommending" best practice. He was quite unequivocal. I...

Looks sweet. That inverter is funny next to everything else though. :) Second Redneck's comment and add that it's nice to see an upgrade approach once in a while rather than throwing multiple thousands at a problem from the start. What's your long term goal? Do you have a particular...

I can't confirm or deny your source's assertion about LiFePO4 specifically arcing but can maybe clear up the terminology. An "arc" occurs when a strong electric field causes a non conductive medium (like air) to break down into plasma, which then acts as a current carrying conduit through the...

That's a bit absolutist. There are quite a few threads about building banks from different brand cells in series: https://diysolarforum.com/search/678241/?q=mixing+eve+lishen&o=relevance And all of those that I've opened have people saying it's OK to do so, even when discussing different...

I'm looking at how to replace the neglected LA batteries in a bass boat with LFP. Currently it has a 12v starting battery that also drives all of the small loads like pumps, depthfinder etc. Then it has two completely separate deep cycle's that both run up to the trolling motor to give it two...

https://www.victronenergy.com/upload/documents/SmartShunt/Manual_-_SmartShunt-en.pdf The voltage in the screenshot is configured for 26.4V, and the battery graph shows the voltage crossing that threshold briefly after charging started. But current was still below the 16 Amp threshold implied...

I'm all for margin if it is possible and cost effective. And it seems like the field reports for 6S show that it is so I'm increasingly leaning that way. The voltage curves are just lines on paper after all. But your destruction occurred because of a dead battery, NOT because of alternator...

Yeah, if 600W won't keep a Dometic running... Then you know why they sold for $0.50 per Watt. On the subject of the thread, CIGS are fascinating and a superior product in many respects as the OP pointed out. But the cost is approaching insane unless you very strongly NEED one or more of the...

The "best" value option I know of is this...

The confusing part though is the charge vs discharge relationship is backwards. Normally, when the battery is charging at a given voltage it is at a lower SOC than if it is at the same voltage discharging. But the charts I found show the opposite - the charge curve is 75%, the discharge curve...

Jesus. When you said you oversized it you weren’t kidding. That could do 4000A. What kind of balancing/management solution are you planning?

Has anyone actually reported trying Yinlong in a 5S config? At this point we can only say Yinglong works well with 6S, but we don’t know if that’s the best. So you’re using the house battery for “headlights and dash”? Or are you getting 80ah LTO cells somewhere? If not, what size cells are...

A bit more research found a research paper showing 3.2V/cell as the point where damage occurs. https://www.researchgate.net/publication/327993928_Overcharge_durability_of_Li4Ti5O12_based_lithium-ion_batteries_at_low_temperature Which is 16v in a 5S configuration, and typical alternators...

Super interesting thread. I'd be really stoked to go LTO for my vehicles, and I've got a truck that needs a replacement right now. But after looking into LTO voltage curves I'm getting pretty confused. For example on a 6S configuration a typical alternator charge voltage of 14.2V would be...

Remember Kirchoves current law... the sum of the currents entering and leaving a node is equal to zero. What this means in real terms is that it is not possible for 2x8 amps to flow into the Y and 12 amps to flow out of it. It violates the laws of physics as surely as free energy. Current is a...

Could you elaborate on those "few reasons"?

I'm not sure if there's some phrasing in Carson's post that would indicate a single BMS in contradiction of the pictures, but all the pictures that show the top of the pack clearly have two 120A BMS's.

Love the build. Very clean! Inspiration for sure as I'm considering a build to fit under the seats of my 4 Runner. The hacked up plastic cutting board is a great material source. I think it's a shame the space savings of a DIY battery isn't discussed more. It's probably because most are...

Man, that's rough. I guess your shed is straight up in the middle of the woods or something? Are you thinking you can get some sun to the panels, or is it a lost cause? I'll try to check Voc next time I get a chance.

Thanks for the input everybody! MPPT = 20% is a useful figure to work off. And I didn't realize they had higher idle draw which is important in a low power system like mine. Sounds like replacing a PWM with MPPT only makes sense when you're around 500 watts and/or needing a series connection...

I have an offgrid network repeater box between my house and ISP, and currently it requires regular battery swaps to maintain. The solar setup is just a 100W panel connected to a Renogy PWM charge controller. It produces 180 Wh on a clear day near winter solstice, mostly because it's right up...

No, those are "off grid" systems as far as I can tell. What you're looking for is a "grid tie" system which can pull from the grid when solar is not enough or push power back into the grid when you have excess power. These require special equipment and permitting because it's possible to...

1. No, you do not need solar, and if you imagine that you will regularly be running the generator anyway there is no reason to have it at all. BUT - you might pause and consider the joy of leaving the generator at home when you don't need AC. The good news: solar is just as easy to add after...

Yeah, you caught it in time and they're completely fine. As far as the cells are concerned nothing ever happened because they never saw high voltage. Sounds like the top balance is progressing as expected now.

Perhaps you sense 'judgement' when I mention emotions? That's your own values speaking not mine. 90% of the world is driven by emotions, and I've long ago foregone condemning people for it. But some people behave emotionally yet highly value rationality, and when someone calls attention to...