Search results

I'm just getting my dataloggers up and running, but I've noticed that through a couple of sweep tests (discharge to inverter cutout at ~10.6v and then recharge back to full) the battery reported SoC values are all over the place. I have no idea what algorithm the internal BMS uses to compute...

Well that's sufficiently vague as to be not-terribly-useful. I (obviously) have no idea how this works, but responding to a helpful comment saying "well that's one way but might not be a great idea" without any supporting detail doesn't seem particularly beginner-friendly :)

Does the figure below meet the criteria / recommendation for the total length of positive and negative cables being the same length? I **think** that it does, but I'm hoping someone can confirm or refute my understanding ;-) Note - not drawn to scale...

Yeah I've been wrestling with windows drivers and trying to find the software and all the .NET stuff.

Hmm. This thing is killing me. I have wired up a connector with what I'm pretty sure is the correct pinout. I have a USB<->RS485 converter that I know works, because I can send/receive data from my battery monitor with it. But when I plug this thing into the Valence battery, nothing happens...

yeah I would love this functionality as well...

SIGH. So searching for things like "Read all pages of a thread" somehow didn't show me this result, but as soon as I posted it, this popped up. Sorry for the noise... https://diysolarforum.com/threads/possible-to-view-all-pages-of-a-thread-on-one-page-for-printing-archiving.53523/

Does the forum infrastructure have some way to look at an entire thread at once? I'm particularly interested in the Valence battery superthread at the moment, but the question applies equally to others I've found. It's really cumbersome if I'm looking for certain things to not be able to...

I've got a raspberry pi dedicated to this build -- is there an easy enough way to have it do whatever needs to be done to keep the internal BMS awake enough to not cause trouble?

I've read through this, wow this is a lot of great info. I came across a pair of U27-XP's that I'm planning on using in parallel with an inverter/charger to function as essentially a high-capacity UPS. I'm trying to figure out how much of the "non existent BMS" functionality I actually need to...

In my case I’m talking about bolting lugs to bus bars or lugs to M8 terminals on assembled batteries

Confused by part of that reply- Aluminum is harder than copper...(?)

Today’s possibly-stupid question. What combination of metal and other materials do people use to bolt down lugs to battery terminals? Knowing nothing, I would think a regular stainless steel bolt, with a lock washer.. but since I just said I know nothing, I’m asking. I haven’t tried to...

So the whole point was to figure out whether or not I was correctly understanding the physics, not whether the application has any actual relevant value. I don't know much, but I know putting two lugs/posts a foot apart makes a lot less sense than putting them 1" apart on a much thicker busbar...

Yep that all makes sense but I guess I still dont understand how the length of the bus bar isn't a part of the ampacity calculation? When I find specs like "195A @ 50° rise" or whatever, how is the length of the bar assumed to impact that?

I was thinking about bus bar sizing and this occurred to me... when we size wires, we care about the cross section (i.e. diameter/radius) of the wire. For busbars all the ampacity tables are ALSO a function of cross section, a 2mm x 10mm busbar is 20mm2 or 40kcmils, and so on. But if one of...

I have a few questions related to charge voltages for LFP batteries... note that these are all somewhat abstract and theoretical based on what little I know and what lot I don't know ;-) -- (assume all numbers here refer to a 12.8v nominal 4s LFP battery) 1. Charge an LFP battery at lower...

wouldn't you want to mount to something nonconductive? Did you drill holes and use bolts/nuts or did you have screws that were sufficiently sharp/strong to just run them through the aluminum?

Cool. If I have to cut off 1/4” of wire every few iterations that‘s way easier than throwing away $4 lugs and however much effort it takes me to get them on there :)

As I'm thinking about what I want to end up doing (for me this is a much a science project/learning experience as an actual use case) I realize that it would be super useful to have a large handful of cables, with lugs, of all different lengths and connector/lug sizes. However, I quickly...

Ok so I'm (sort of?) following that ... but what happens if the charger leaves the absorption voltage too high for too long? Isn't it the case that once you're at the cutoff voltage on the battery side the BMS simply stops accepting charge? Or am I (still!) missing things here? :) And if one of...

There are several all-in-one inverter/chargers that all look shockingly similar in how they're constructed, wired, the manuals, etc etc etc. If I had to bet they are likely all sourced from the same or a small set of base suppliers and then have some various seasoning applied in terms of things...

Oh cool - makes perfect sense now. Thanks.

Don't think anyone has mentioned, but tap off busbars to feed inverter from opposite ends, or otherwise balance current draw. Sorry I'll have to fess up here, I have absolutely no idea what this sentence means...?

So this thread is great, thanks. My question is what happens if/when you have multiple chargers that are set for different battery types or profiles? One of the chargers I have the manual for has two "AGM" battery settings, "AGM1" is 14.1/13.4v, and "AGM2" is 14.6/13.7v. If I were to wire up...

Super useful. My application (at least for the forseeable future) is substantially over-engineered for a 1500W inverter: I literally can't come up with a use case that consumes more than 1000W, and even that is a stretch. But the process of learning what values matter and where is quite...

Super useful. A couple followups: let's assume the valence batteries are all treated as separate batteries - totally ignore the fact that they have some #additionalValenceMagic that we might use... I'll just ignore that for argument. If they're "just plan normal parallel 12v LFP batteries"...

I'm working on basically a homebuilt UPS, this is by far the best forum I've been able to find so thanks to everyone who's already helped (and how much stuff I've read already)... I've got a line on some half-used Valence LFP batteries and they're cheap enough to justify playing around with for...

Anyone know if there are spectacular failure modes I need to worry about? "It quit working" is a lot less of a concern than "it burned the house down..."

My use case is something along the lines of: "I want to be able to have a KWh or two available as backup power, with a load that won't exceed more than 400W sustained with peaks of 700W for a couple of seconds." If I really really stretch my brain out, I guess I could see maybe needing to run...

So this is fantastic - one of my philosophies (thanks, Dad!) is "buy good tools and you'll never regret them" ... I guess this question in my head was more about "tools" in the sense of crimpers, power supplies, soldering irons, stuff like that... as opposed to any "active" components like the...

I'm in a very similar spot - I'm trying to build something that's bigger and more expandable than a "big UPS" but not ready to drop several grand on a full powerwall-type system. From my limited learning so far.... I don't think there are any (many?) inverters where you can easily change the...

OK, that makes sense that one might have cut out before the other… I keep forgetting that each of these individual lifepo4’s has it’s own logic (unlike stupid SLAs which just do whatever the physics in their heads tells them to do)… How would one go about “watching the charging profile of the...

I need some help with the last part... if you can't determine SOC from the resting/open voltage how CAN you determine if these things are charged? The meter I've got is accurate to a hundredth of a volt, so it's hard for me to understand how that's not a valid metric. And if it's NOT a valid...

So after a year of farting around watching youtube and lurking forums I've sort of decided to do a nerd project and see if I can progress through some combination of "hack an existing UPS for longer runtime where I don't have to replace stupid lead-acid batteries every year" and eventually end...