Update. Replacement BMS? What's next?

Hedges

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I will write a much more detailed reply later when I have the time. Daly has some bad defaults for voltage settings (3.75 and 2.1) that you really should change before you use your new cells and BMS too much.

Short term, you just want to change the default protection values, but just don't overcharge or over discharge the battery until you do.

OP - do you know what maximum voltage your charge controller charges to, and what minimum voltage your inverter discharges to before disconnecting?

BMS is meant to be your last-ditch protection mechanism to save battery from damage. Settings of 3.65V and 2.5V would be good for that. The defaults of 3.75V and 2.1V are pushing it too far, more chance of damage (and vanishingly small additional amp-hours made available with those wider voltage settings.) You should adjust BMS settings ASAP for your new battery and for the new BMS you're putting on the old cells.

Your charge controller and inverter should stop/disconnect at even tighter limits. It is best they never try to reach the point where BMS disconnects. Sometimes you have to figure out how to reset BMS if that happens. Maybe something like 3.35V charge and 2.8V (per cell) discharge would be good? The other guys can better recommend settings. It seems likely (from your 13.45V measurement) that the charge controller already does that. But lots of inverters discharge too low, so see if its low-voltage cutout is adjustable.
 

Hedges

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It may be that on the discharge side, if BMS is to be set for 2.5V per cell (10V for 4s battery), then inverter low-voltage disconnect ought to be closer to that voltage. If 2.8V per cell (11.2V for 4s battery) as I suggested, the inverter might shut off when driving a heavy load.

BMS has sense wires right on busbars, including battery +/- terminals. But inverter is at the end of longer cables, maybe also with fuse/breaker and other components. When it is drawing 100A or more, the voltage it sees includes IR drop through those things. So a voltage barely above 10V might be good. Unlike lead-acid, there is a distinct knee to the voltage curve. The goal is to set voltage low enough that most capacity is available, but not cause BMS to disconnect.

Anybody here have a good recommendation for low-voltage shutdown of inverter?
 

jesfl

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OK, that explains the 120A part. I am placing the Overkill order. While I do not yet know how to use it, I do like the idea of monitoring via BMS.

So you are saying any 4S BMS with 120A (or temporarily 100A) output would work? So maybe I could buy a cheapie BMS, get some brass sheet, solder the leads, and work through that undoubtedly problematic for me process before I try it the first time on an Overkill BMS and damage it somehow? I am guessing it will be well past 1-month before the Overkill arrives. Further complicating the problem is that I am full-timing in my RV which means there is no easy ship-to address. So, I will have to ship it to my mail forwarding service for reshipment to me after it finally arrives. Slow, elongated process.

I believe you are correct about the "used" part. When I was tearing the first battery apart, I noticed a magic-marker notation of 140.4 with a following Chinese symbol. That caused me to question if that was the tested voltage. I now bet it was. BtrPower sells tons of e-bike batteries, apparently. Now I am guessing they appropriated some e-Bike cells and made the "150Ah" battery to sell into the RV market (per their eBay listing). When I get past this hump, I think I will contact eBay and see if I can get my money back from eBay because of that fraud. Worth a try!

Thank you, again.

in order should measure 3.35V, 6.7V, 10.05V, 13.4V.

I checked and got exactly the voltage readings you expected. Then, just to double-check, "in order" means 3.35V is cell #1, 6.7V is cell #2, etc. Correct?

Thank you for that suggestion and informattion.
Sorry, "internal resistance" and "knee" of the charge curve would be more difficult concepts.

Just John pointed out your old BMS says 3.65 and 2.5 volts (everything else is Chinese) so those are the max and min voltage settings you want your new BMS to have. Whether it comes pre-set or is programmable I don't know; someone who has used the recommended BMS can tell you.

"DMM" Digital Multi Meter is just a volt meter. You have four, approximately 3.35V cells wired in series. Checking voltage between terminals, with black DMM wired o negative terminal and the other terminals in order should measure 3.35V, 6.7V, 10.05V, 13.4V. I think the order starts at one ends of the battery and zig-zags back and forth to the other end, but voltages will tell.

If voltages are out of order then figure out what order the cells are in. If voltages are negative then either you started at the positive end or have meter wires backwards. You can label terminals with a felt pen. It will be important to connect BMS wires in the correct order; it would be damaged if wired incorrectly. I think the BMS has a connector for its balance leads, so unplug connector while soldering wires and double-check their order before plugging in connector.

Remove rings or other jewelry. Wrap electrical tape around any wrenches or screwdrivers so no piece of metal is long enough to connect between two terminals. Wear safety goggles. These batteries put out several times as much current as a car battery, melt things faster.

Since voltage looks good, I think the cells are fine. If battery worked correctly and had sufficient capacity right up until it suddenly stopped working, it still has capacity.

That is incredibly helpful. Thanks again. I think I may be beginning to understand the bigger picture of Battery + BMS.
 

jesfl

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Those are pretty standard voltages for LiFePO4 cells. The packaging is large pouch cells. The setup looks to be 4S of 3P sections. The stack has 24 plastic "plates". It looks like each cell is sandwiched between two of the plates. The cell tabs are bent over at 90 degrees and bolted to the buss bar plates on top. Two tabs fold towards each other and share the bolts. So each of the buss bars with 6 bolts have 6 tabs clamped to it. The 3P from the previous group to the 3P of the following group. The end bars just have 3 tabs, two sharing a pair of bolts, and the third with 2 bolts. The construction is actually pretty good. 50 amp hour pouch cells in a fairly robust package. Much nicer than a pile of spot welded 18650's. The cut off ring terminals are a bit interesting. It looks like the supplier you got it from already replaced the BMS and did a sloppy job of it.

I agree there is no reason at all to pull it apart any further. The buss bar setup looks solid and should handle the current without a problem. For a short term test, you can try pulling some power from the cells off the end 4 bolt buss bars for a few minutes and make sure the cells put out power before you spend much money on replacing the BMS etc. Just don't run the cells below 2.5 volts. I would actually stay above 2.8 volts. If the cells prove worthy, it should not be a big deal to wire on a BMS. You just have the negative side high current cable and the 5 voltage sensing/balance leads. Any 4S LFP BMS should work just fine. 100 amp units are getting cheap now. As long as your charger and load stay between 2.8 volts and 3.6 volts, you don't need a fancy BMS. It is just there to shut off if something goes wrong. If a single cell does go above 3.65 or below 2.5 it just turns off until you can correct the situation. Being able to set the parameters and remote monitor it are nice, but each feature you add will increase the price. Even a non adjustable that has wider shut off is fine as long as you don't run the full capacity. If you get all 3 back running, along with your new 200 amp hours, you will have 650 amp hours, so you should be good to go.

Do you know what your maximum current draw should be? And how many amp hours you will actually use each day?

You could wire all 3 of the failed batteries in parallel with a single BMS. Maybe use Will's trick of using a small cheap BMS to operate a relay to handle the load. Use heavy cable to parallel the main positive and negative buss bars and run through the contactor to the load. Use 3 more cables, of about #8 awg or so to jump together the matching 3 bolt buss bars to force the cells to stay in balance from pack to pack. Then just wire up one BMS to the 5 balance leads of the middle pack. Now you have a single 4S 450 amp hour battery.

WOW! OK, I am trying to absorb all of that.

Paragraph #1 -- I need to read it another half-dozen times, but beginning to understand.

Paragraph #2 -- Again, re- re-read required. Not sure how to "pull power" for a test. But, do I even need to do so? I'm OK just buying a BMS, wiring it in, and seeing what I get. Very simple is best for me.

The disconnected, torn-apart battery has been holding exactly the same voltage since I first tested it yesterday. But, I think I understand that that is not a test with "load" which I believe is what you are suggesting?

Paragraph #3 -- Yes, I think so? When running completely from batteries (previously 450Ah) with the inverter off and all other "little" things off, I have a parasitic draw of less than 1 amp, which I think is pretty good. I went through the process of turning everything off and running appliances one-by-one and watching my interior voltmeter. TV/soundbar = 8-9 amps, at night with darker screen an amp less. Laptop computer+printer+Google Nest Hub+LED smart light bulbs = less than 10 amps, Icemaker = 8 amps max when making ice. Once or twice a month I use an Instant Pot and I never checked the amperage use when it was running because it ran without any problem whatsoever. I also did not check the 1200 watt microwave, but it is by far the biggest power user I have and use.

Now, I did not add up everything, but I do know during the perfect months of heavenly operation of the solar+batteries, normal usage was 10-12 percent, or around 50 Ah per day. Correct? One time as a test, I turned on and left everything on for a full day (6 am-10 pm). The best I could do was use 23% of my previous 450Ah battery capacity. All smiles. I thought I was golden. Even on worst-case cloudy winter days after normal use I was getting a 100% recharge by 2-3 pm. Then the battery/BMS failure.

I also have an Onan propane genset that recharges the batteries pretty quickly too in my tests (when exercising it). I bought and installed a PD lithium converter in the WFCO power panel. But, I never used it . . . except twice over 4-5 months when desperate for air conditioning.

Note: earlier today I tried running the microwave for the first time on my single 200Ah battery. It caused a fault with my inverter, but I kinda' expected that because not knowing any better I bought a 3000W inverter. I do understand it is a power hog and with the single battery, it creates a "loading problem" as it was previously explained to me. Not a big deal for now, because I use a microwave so little.

I spelled that out because I want to be sure my thinking is correct. If I am way off course, please give me a kick-in-the-butt and correct me.

Paragraph #4 -- Not a chance, except in desperation, chuckle, chuckle. I'm OK ultimately buying 3 new BMS units over time, one for each battery . . . IF the first one works OK? That would give me 350Ah of battery for now, which probably is more than I need, except for the bloody larger-than-necessary inverter.

Thank you, thank you, THANK YOU. I continue to be awed by the gracious assistance offered by everyone on this website. Clearly, everyone is saving my butt big time.
 

jesfl

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It may be that on the discharge side, if BMS is to be set for 2.5V per cell (10V for 4s battery), then inverter low-voltage disconnect ought to be closer to that voltage. If 2.8V per cell (11.2V for 4s battery) as I suggested, the inverter might shut off when driving a heavy load.

BMS has sense wires right on busbars, including battery +/- terminals. But inverter is at the end of longer cables, maybe also with fuse/breaker and other components. When it is drawing 100A or more, the voltage it sees includes IR drop through those things. So a voltage barely above 10V might be good. Unlike lead-acid, there is a distinct knee to the voltage curve. The goal is to set voltage low enough that most capacity is available, but not cause BMS to disconnect.

Anybody here have a good recommendation for low-voltage shutdown of inverter?

Well, those two posts are a big curveball to me.

So, first, I need to figure out how to connect to the Daly Bluetooth? No instructions came with the battery & BMS. Is there an app? How does that work, if anyone knows. I will now start searching for Daly BMS user information. Supposedly the BMS was "preset" specifically for the cells to which it came connected. So, I didn't take it further with everything else.

Thanks for the heads-up.

I have not digested to anywhere near a point of understanding the discussion about BMS settings and inverter settings. Another re- re-read.
 

Hedges

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Yeah, I'm an EE so thinking about voltage drops due to current draw is second nature to me. But I've never used any kind of lithium except in yard tools and electronic gadgets.
Short, fat wires from battery to inverter is good. A suitable fuse (probably "class T") in the positive cable close to the battery is a good idea in the event you ever drop a screwdriver in the wrong place or wire insulation gets abraded.

You'd rather the inverter didn't shut off when you were microwaving dinner or something like that, so ideally the low-voltage cutoff is set carefully.
Test is often better than analysis, and having a volt meter across the battery and another across the inverter battery terminals, while drawing a heavy load, will tell a lot. Try it with fully charged battery, and with relatively low battery. Then you'll have a good idea what the BMS sees vs. what the inverter sees. (also record the voltages with no load.)
 

jesfl

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I think I am OK on the short fat wires. I have 4/0 AWG (previously connecting the three failed batteries/BMS, 9" there) and 4/0 AWG from the battery (one for the moment) to the inverter, about 18" total with an on/off switch and a 175 amp breaker inline from the battery to the inverter. Correct? (I was told the 4/0 was overkill, but it was just $20 more than 2/0 so since I think I know bigger is better when carrying current, I went big.)

However, the BMS negative connection is the weak spot, as it appears to be 6 AWG. Probably cannot change that.

"Class T fuse" is beyond me. Does the 175 amp breaker work OK? Do I need to change that to something else? After buying and installing it (per one of Will Prowse's basic system videos), I have read that breakers are not always dependable.

As to two voltmeters for testing, I have one very basic multimeter with six settings and I use only two -- DC voltage and amps. Real, real beginner here. I hope to learn more about testing with a meter, but right now it ios all I can handle trying to get the system back up and running so I can live! Honestly, I'm kinda' surprised I've gotten as far as I have without blowing something up or causing a fire.

I'll try to think through what you are suggesting for the inverter test.

Many thanks for the new knowledge. I infer from your suggestion that there is probably a low voltage cutoff setting in the inverter that can be changed? I didn't know that, of course. I'll see what I can find in the inverter manual on that point.

Thank you.
 

Just John

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Well, those two posts are a big curveball to me.

So, first, I need to figure out how to connect to the Daly Bluetooth? No instructions came with the battery & BMS. Is there an app? How does that work, if anyone knows. I will now start searching for Daly BMS user information. Supposedly the BMS was "preset" specifically for the cells to which it came connected. So, I didn't take it further with everything else.

Thanks for the heads-up.

I have not digested to anywhere near a point of understanding the discussion about BMS settings and inverter settings. Another re- re-read.
Play store, search for smartbms by dalybms. Daly uses terrible defaults, that is why I mentioned it.

Edit to add, when changing some settings, the password is 123456.
 
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Just John

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It may be that on the discharge side, if BMS is to be set for 2.5V per cell (10V for 4s battery), then inverter low-voltage disconnect ought to be closer to that voltage. If 2.8V per cell (11.2V for 4s battery) as I suggested, the inverter might shut off when driving a heavy load.

BMS has sense wires right on busbars, including battery +/- terminals. But inverter is at the end of longer cables, maybe also with fuse/breaker and other components. When it is drawing 100A or more, the voltage it sees includes IR drop through those things. So a voltage barely above 10V might be good. Unlike lead-acid, there is a distinct knee to the voltage curve. The goal is to set voltage low enough that most capacity is available, but not cause BMS to disconnect.

Anybody here have a good recommendation for low-voltage shutdown of inverter?
I would actually recommend 12 volts (adjusted for real voltage drop). That's 3 volts per cell, and somewhere around 5 to 10% from empty (closer to 5 than 10). On my 280AH cells, that is about 5 to 10 amp hours from 2.5v. He can set charge controller with a float of 13.6v, that will keep his battery charged about 95% until the sun goes down.
 

Hedges

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Your "175A" breaker is probably good. Midnight sells one rated to interrupt an incredible 50,000A worth of short-circuit. (Although I find that hard to believe). A car battery can deliver 3000A. I think a typical 100 Ah or 280 Ah lithium battery can deliver 20,000A into a short, which lesser fuses and breakers can't interrupt, could just sit there burning. "Class T" fuse is tested (destructively, in development and UL listing) to interrupt 20,000A at 125VDC.

With just one meter, while running a heavy load (like an oil-filled radiator space heater), measure voltage at battery and voltage at inverter a couple times (reading may or may not change quickly.) See how much lower voltage is at inverter.

John - you recommend 12V low-voltage disconnect at inverter? Or what do you mean by "adjusted for real voltage drop"?
I figured that if battery was at 12V and inverter was drawing 100A or 200A, voltage at inverter would be noticeably lower.
 

Just John

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Your "175A" breaker is probably good. Midnight sells one rated to interrupt an incredible 50,000A worth of short-circuit. (Although I find that hard to believe). A car battery can deliver 3000A. I think a typical 100 Ah or 280 Ah lithium battery can deliver 20,000A into a short, which lesser fuses and breakers can't interrupt, could just sit there burning. "Class T" fuse is tested (destructively, in development and UL listing) to interrupt 20,000A at 125VDC.

With just one meter, while running a heavy load (like an oil-filled radiator space heater), measure voltage at battery and voltage at inverter a couple times (reading may or may not change quickly.) See how much lower voltage is at inverter.

John - you recommend 12V low-voltage disconnect at inverter? Or what do you mean by "adjusted for real voltage drop"?
I figured that if battery was at 12V and inverter was drawing 100A or 200A, voltage at inverter would be noticeably lower.

Real voltage drop means, when drawing a heavy load, inverter might read 11.8 volts, but battery is at 12 volts. So just what you are talking about.

You really shouldn't need to take the cells below 3 volts, that's way down in the knee. 90% of the power is between 3 volts to 3.4 volts.
 

jesfl

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Play store, search for smartbms by dalybms. Daly uses terrible defaults, that is why I mentioned it.

Edit to add, when changing some settings, the password is 123456.

I found the DALY Smart BMS app, but it would not load from the Android Play Store onto my Samsung S10? Tried and tried. Finally decided it must be blocked by some setting in the S10?

I then pulled out a 6-year-old LG phone and loaded the app there with no problem, finally. Got it connected.

The current settings of the BMS - which again were supposed to be "preset" for the cells I bought -- are:

Protection Parameters
- cell volt high protect, 3.65 volts
- cell volt low protect, 2.50 volts
- sum volt high protect, 14.60 volts
- sum volt low protect, 10.00 volts
- diff volt protect, 0.26 volts (whatever that is?)

Cell Characteristics
- type of battery, LFP/liFePO4
- rated capacity, 206.0Ah
- cell reference volt, 3,20 volt
- sleep waiting time, 3600S
- SOC set, 100.0%

Collect Board Settings
- boards num, Machine 1
- board 1 cell num, Machine 4
- board 2 cell num, Machine 0
- board 3 cell num, Machine 0
- board 1 temp num, Machine 1

Temp Protection
- chg high temp protect, 55 degrees C
- chg low temp protect, 5 degrees C
- disChg high temp protect, 70 degrees C
- disChg low temp protect, -40 degrees C
- diff Temp protect, 255 degrees C

Parameter Settings
- Chg switch, ON
- Dischg switch, ON
- then a series of reset buttons, system, factory, zero drift current, password.

Where are those setting not the best, please? I have no idea what most of them are about.

What would you change if was your DALY BMS?

It was somewhat curious to me that the "charge low-temperature protection" was set to 41 degrees F. I was under the (beginners) impression that just above freezing -- like 33-34 degrees F was supposed to be the cutoff temp? I hit 40 degrees F and below numerous times overnight in the southernmost Arizona desert this past January and February. (But that was nighttime and there was no PV charging anyway. Is the 41 degrees F cutoff for charging just erring on the side of caution, or is that really as low as it should go . . . if I ever hit a very cold snap in the daytime with the solar charging active?

The other settings, I do not have any understanding of . . . yet. Hope to learn. But, I will go back and read your previous post to try to understand better.

Thank you for helping me find these. It is an incredible learning experience every baby step I take.
 

Just John

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I found the DALY Smart BMS app, but it would not load from the Android Play Store onto my Samsung S10? Tried and tried. Finally decided it must be blocked by some setting in the S10?

I then pulled out a 6-year-old LG phone and loaded the app there with no problem, finally. Got it connected.

The current settings of the BMS - which again were supposed to be "preset" for the cells I bought -- are:

Protection Parameters
- cell volt high protect, 3.65 volts
- cell volt low protect, 2.50 volts
- sum volt high protect, 14.60 volts
- sum volt low protect, 10.00 volts
- diff volt protect, 0.26 volts (whatever that is?)

Cell Characteristics
- type of battery, LFP/liFePO4
- rated capacity, 206.0Ah
- cell reference volt, 3,20 volt
- sleep waiting time, 3600S
- SOC set, 100.0%

Collect Board Settings
- boards num, Machine 1
- board 1 cell num, Machine 4
- board 2 cell num, Machine 0
- board 3 cell num, Machine 0
- board 1 temp num, Machine 1

Temp Protection
- chg high temp protect, 55 degrees C
- chg low temp protect, 5 degrees C
- disChg high temp protect, 70 degrees C
- disChg low temp protect, -40 degrees C
- diff Temp protect, 255 degrees C

Parameter Settings
- Chg switch, ON
- Dischg switch, ON
- then a series of reset buttons, system, factory, zero drift current, password.

Where are those setting not the best, please? I have no idea what most of them are about.

What would you change if was your DALY BMS?

It was somewhat curious to me that the "charge low-temperature protection" was set to 41 degrees F. I was under the (beginners) impression that just above freezing -- like 33-34 degrees F was supposed to be the cutoff temp? I hit 40 degrees F and below numerous times overnight in the southernmost Arizona desert this past January and February. (But that was nighttime and there was no PV charging anyway. Is the 41 degrees F cutoff for charging just erring on the side of caution, or is that really as low as it should go . . . if I ever hit a very cold snap in the daytime with the solar charging active?

The other settings, I do not have any understanding of . . . yet. Hope to learn. But, I will go back and read your previous post to try to understand better.

Thank you for helping me find these. It is an incredible learning experience every baby step I take.
No, those are good settings. I am very surprised, someone set it up properly, Daly doesn't. My Daly came set to allow charging to -40.

The temperature charging cutoff is conservative, it is what I use. The closer you get to freezing, the lower the amps in. In other words, at freezing stay below a couple of amps in, at 40, limit to 10 amps, etc. Freezing or below, best not to charge at all. The cells like the same temperature you do, about 75 to 80 is just right.

FYI, whoever you bought the battery from did a good job.
 
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Hedges

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Temp Protection
- chg high temp protect, 55 degrees C
- chg low temp protect, 5 degrees C
- disChg high temp protect, 70 degrees C
- disChg low temp protect, -40 degrees C
- diff Temp protect, 255 degrees C

It was somewhat curious to me that the "charge low-temperature protection" was set to 41 degrees F. I was under the (beginners) impression that just above freezing -- like 33-34 degrees F was supposed to be the cutoff temp? I hit 40 degrees F and below numerous times overnight in the southernmost Arizona desert this past January and February. (But that was nighttime and there was no PV charging anyway. Is the 41 degrees F cutoff for charging just erring on the side of caution, or is that really as low as it should go . . . if I ever hit a very cold snap in the daytime with the solar charging active?

That's partly erring on the side of caution, but I think it is useful protection too.

Is your battery exposed to the 40 degree F environment? It has mass, will store heat soaked up in the day so may not reach ambient temperatures at night. You can put it in an insulated box. Under some conditions that might cause it to become too hot, but unlike lead-acid it doesn't generate much heat (except at high charge rates.)

I've seen tables of allowed charge current vs. temperature and vs. state of charge. The allowed current tapered off as temperature approached zero degrees C. If you had a battery specified for 0.5C or 1.0C and a PV array capable of delivering that much, such charging just above zero C would degrade it. Ideally the charge controller would have settings to taper of charge current at low and high settings, but I'm not sure any do (other than EV chargers, which also integrate active heating and cooling.) So having charge protection set higher than zero could be beneficial.

If you have much PV, you could compare charge rate with battery specs, and adjust the BMS protect temperatures based on tables given for other cells in this link. I interpret them as indicating that at 5 degrees C, charge current should be limited to 0.12 times what can be accepted at room temperature.

 

jesfl

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No, those are good settings. I am very surprised, someone set it up properly, Daly doesn't. My Daly came set to allow charging to -40.

The temperature charging cutoff is conservative, it is what I use. The closer you get to freezing, the lower the amps in. In other words, at freezing stay below a couple of amps in, at 40, limit to 10 amps, etc. Freezing or below, best not to charge at all. The cells like the same temperature you do, about 75 to 80 is just right.

FYI, whoever you bought the battery from did a good job.

Thank you. I will leave everything as is. Your help is exceedingly helpful and reassuring.

But, a curiosity. I'm looking at the Bluetooth settings right now, and my mind cannot quite grasp how to set up " . . . at freezing stay below a couple of amps in, at 40, limit to 10 amps, etc."? That is if I ever wanted to change anything? I infer there is a way to connect the shutoff temp with an absolute max amperage charge?

And, then, my wondering mind asks why no one ever seems to mention the high temp cutoff? Does that not matter, even if the temp reaches the preset 131 degrees F cutoff? Will charging at 125 degrees F damage the battery?

FYI, I bought a Lynx Battery package. New company, on Amazon and eBay. U.S. inventory of cells & BMS in Seattle. They started selling cells + Daly BMS + incidental parts as "kits." Must not have gone that well? But, as a beginner, I absolutely would not have bought the kit or cells/BMS separately. Too overwhelming. Now selling them assembled and tested, supposedly, it made a great
 

jesfl

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. . . (from previous post) . . . it made a great buy for me because of the 4-day UPS shipping (when UPS doesn't screw up). I was desperate and I had to have a U.S. inventory battery. The price for the Lynx package was very competitive with others (stocked in U.S.) -- $550/100Ah, $1050/200Ah, I thought.

Because of everyone's incredible help here on the Forum, I now would buy cells and BMS and assemble confidently, if I ever had to do so because I can't get the failed batteries/BMS working again. It looks to me, without shopping, I could buy U.S. stock cells and BMS for a 100Ah battery for a little over $400. If waiting for AliExpress stuff, it might be closer to $325, I think.

Again and again, THANK YOU to you and every one of the generous, giving and extraordinarily helpful human beings on this Forum. I continue to be absolutely flabbergasted at the magnanimous responses.

Thank you, thank you, thank you.
 

Hedges

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Most people here don't live in Death Valley, but many have homes, cabins, or RVs that experience freezing weather. Charging in hotter or colder conditions will accelerate damage to the battery. Below freezing, apparently quite rapidly.

I don't think most if any BMS and charge controllers do anything at high/low temperatures except disable charging.
All you get is on/off control. You can determine what max charge rate (percentage of battery capacity) your PV array could deliver.
Then adjust high/low temperature cutoff to something where that charge rate is acceptable.

From the table in the link I gave, if battery can accept 1.0C, that is only OK between 20 degrees C and 45 degrees C. So if your PV array wattage equals battery watt-hours, set high/low temperature disconnects to those values.

If your PV array wattage is 0.3C compared to battery capacity, set it for 7 degrees C and 55 degrees C.

Or a bit tighter to be cautious.
If you orient PV strings with multiple angles (peak at different times of the day) that will reduce peak charge current and give more hours charging, so you can capture more watt-hours into the battery and set the temperature limits wider.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,434
"Class T fuse" is beyond me. Does the 175 amp breaker work OK? Do I need to change that to something else? After buying and installing it (per one of Will Prowse's basic system videos), I have read that breakers are not always dependable.

Your "175A" breaker is probably good. Midnight sells one rated to interrupt an incredible 50,000A worth of short-circuit. (Although I find that hard to believe).


Depends on the breaker.

I would trust this one: https://www.amazon.com/Outback-PNL-175-DC-175-Panel-Mount-Breaker/dp/B007IABLIK

But not this one: https://www.amazon.com/GLOSO-Breaker-Extended-Diagonal-Waterproof/dp/B08LKG4MYR/ref=sr_1_4

Only a known good name brand, and hopefully not counterfeit.
 

jesfl

Solar Enthusiast
Joined
May 17, 2020
Messages
80
Thank you again, very, very much. But . . .

. . . If it is not one thing . . .

This morning, I blew the 175 amp breaker on the main 4/0 cable from the battery to the inverter? That never happened (with my old 450Ah battery array before failure)? I decided to try my small electric coffee pot (easier, faster coffee). It worked fine previously, used daily. So, something has changed, somehow? I know from my previous testing that the coffee pot draws 60 amps +/- for 5.5 minutes to make a small pot.

Therefore, your response about breakers is especially timely. But raises further questions . . .

(1) What might I look for to diagnose what changed and caused the breaker to trip?

(2) Before I invest $100+ on a new breaker, can I safely increase the size to 200 amps to solve this problem?

(3) Is a fuse holder + ANL fuse (200 amp) a suitable replacement for a breaker?https://www.amazon.com/gp/product/B004ZJ0WEQ/ref=ox_sc_act_title_2?smid=ATVPDKIKX0DER&psc=1
Most of my components are Blue Sea because I knew it to be a quality brand from my previous sailing years. I suppose there is a quality difference in ANL fuses, too?

How the heck is a beginner supposed to know all this stuff?
 

Just John

Photon Sorcerer
Joined
Aug 15, 2020
Messages
2,390
They are of course now out of stock, but I have been using a high quality circuit breaker (200 amp) for a 150 amp load.
The circuit breaker and/or fuse is used to protect the wires and the battery. With the 4/0 cables you are using, there should be no problem stepping up a size larger. Random trips are common (as well as random "it didn't trip") with cheap Chinese circuit breakers. Circuit breakers and fuses are things you don't want to be cheap with.


I see the panel mount 200 amp breakers are in stock, panel mount means the lugs are on the back rather than the front.

Not sure about this brand, but they are in stock, and made in USA.

I've also installed a 200 amp class T fuse, but they are really not cheap (especially if you blow a fuse often, so far I haven't).

I mainly use the circuit breaker as a "this is now off" type of switch. The fuse is installed before anything else for me.
You can of course just continue to use a high quality breaker, just don't get a cheap chinese copy. You want it to work when it should.
 
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