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Small Cabin Forum / Off-Grid Living / Li Battery Charging
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paulz
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# Posted: 7 Dec 2021 11:00 - Edited by: paulz
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They had a saying back when I was employed at a large company, RTFM, Read The Fing Manual.

Connecting the two Parallel jumper terminals on the MWs did the trick, both units putting out equal power. Didn't boost the total output much though, each is putting out about 20A. Cells are at 3350.

Might be I need even thicker cables. A couple of these I've got jury rigged may only be 6awg, can't tell with the insulation. So next step is a proper rack and cabling. At least I know it works.

paulz
Member
# Posted: 7 Dec 2021 12:02
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Upon closer inspection all my cables are 4awg. There's a thousand amp charts online, 4awg maybe 60-70?
20211207_084559.jpg
20211207_084559.jpg


gcrank1
Member
# Posted: 7 Dec 2021 12:08
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Gauge....a start
Then length, and ends, quality of crimps, etc


paulz
Member
# Posted: 11 Dec 2021 16:40 - Edited by: paulz
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After testing and getting a nice sine wave out of my Onan generator, I felt confident to plug in two MW power supplies and connect to the battery bank, sitting at 3319 per cell this morning. I had also connected the two MWs together with solid copper bars and eliminated the ammeter, so they were connected straight to the bank via 3' 4awg welding cables. MWs set at 14.1 volts.

The results were again unimpressive at first, about 7A per battery, 28A total. I unplugged one MW and amps dropped to about 20.

I then turned up the one MW to 14.6 volts and amps went up over 10 (40 total), even tripped the 50A breaker. I stopped there.

So I'm wondering, could I charge at 14.6, which is what the Valence battery spec sheet says, and just shut off the charging or dial it down when they get to 14.1?

gcrank1
Member
# Posted: 11 Dec 2021 17:28
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Over on diysolar I keep seeing 14.4 bulk, 13.6 absorb but not for too long, with no float or eq. Iirc the 14.4/13.6 is BattleBorn specs?
That isnt supposed to get to 100% quickly but close enough, like 95% and be easy on the bats. Sounds good to me.
Lower voltage will finally get there and be easy on the bats too.
Some are saying bat charger agm setting are working ok but dont use gel or fla settings.

paulz
Member
# Posted: 12 Dec 2021 06:55
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Thanks. Yep, Battleborn says this:

The bulk and absorption voltages typically vary between 14.0 and 14.8 V, and the float can vary between 13.2 and 13.8 V. The 12V Battle Born Batteries sit comfortably right in the middle of these ranges. We recommend a bulk and absorption voltage of 14.4 V.

https://battlebornbatteries.com › Battle Born Blog

paulz
Member
# Posted: 27 Dec 2021 08:29
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Was just reading about Li battery life expectancy. 10 years the most stated average, but possibly more with 'proper care'.

Nissan Leafs and Chevy Volts have been out around 10 years, I wonder if they are replacing batteries in them. Or guys that are using them in solar.

My Valence batteries are same age..

Steve_S
Member
# Posted: 27 Dec 2021 09:13
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Leaf Batteries have always had their issues because of the design and no active thermal management (cooling). Your Valence are LFP (LiFePO) and that chemistry has a good long term rep in general.

GM stopped making the Volt a while back. The Bolt well not gonna touch that... we've all seen the news eh.

EV Lithium NMC, NCA etc are also not the best for standard ESS use and most "PowerWall / PowerBlock" manufacturers are either coming out with LFP based systems or are converting to (even Tesla). Not only because it is a safer chemistry but a lot cheaper to make & sell.

gcrank1
Member
# Posted: 27 Dec 2021 09:58
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Steve, have you any thoughts on the 'start-up company with the Mango Power Station?

Steve_S
Member
# Posted: 27 Dec 2021 11:05
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I learned long ago to NOT touch any beta stuff. Indiegogo and such are "to be debugged" products and too much of a gamble.

Something that has gone past a couple of full revisions and is debugged & working to spec "commercially" I would consider.

There are crap loads of reviews on these but also the critical reviews. For example, you can see Bluetti evolve from when it started with lots of quirks, foibles & issues way back when, the lessons learned & improvements made with new versions, to what they are putting out now. But any "new" product line has to evolve.

I hate wasting money, too easy to do, especially these days...

paulz
Member
# Posted: 28 Dec 2021 11:55 - Edited by: paulz
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Thanks Steve, I did not realize EV batteries were not LFP.

So yesterday I made toast off the battery bank, first time. 1,000 watt draw. I usually just toast with LP but it takes awhile for the pan to warm up. Maybe they have LP toasters..

First thing it did was trip the 50a breaker to the inverter. Replaced it with 100a breaker. It's probably time to seriously consider a reconfig to 24vdc and a transformer to run the all the 12v stuff.

Anyway I glanced at the SCC meter while the toaster was going, I think the amps jumped up a couple. Would that be an indication that the battery bank had a sufficient charge, more power was available from the panels but not being used, and when the toaster took a draw the SCC upped the amps? Do they work like that? If not, it was probably just the constant sunlight changes I deal with.

Steve_S
Member
# Posted: 28 Dec 2021 13:52
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@Paulz LFP is used in EV's as well but up until recently mostly only in China. As the chemistry has evolved over the past few years it's become suitable for Heavy to light vehicles now.

Sounds like your SCC just upped to it's maximum input while you were toasting and only the balance was made up from the battery.

That is typical, I see that all the time. ON a good sunny day with batts charged and taking a couple of amps and I turn on the nuke which pulls 75A, my solar will step up to power it IF it can, if not the balance get's pulled from the battery and once thats done the SCC will switch into Bulk Charge usually to top off if needed.

paulz
Member
# Posted: 28 Dec 2021 15:23
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Ah OK, makes sense. Thanks Steve. This is first time I've drawn more than about 100 watts from my bank, other than running a miter saw for a couple seconds, so I never noticed it before.

I, like others I read about here, started of with "I'll just have a couple LEDs and phone chargers..", and next thing you know it's inverters, appliances, fans.. Also read the warnings from those who've been there to plan ahead.

gcrank1
Member
# Posted: 29 Dec 2021 14:44 - Edited by: gcrank1
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Well, Ive entered 'the brave new world'.....
A Rhino-Volz 50ah lfp came in my Christmas stocking (a 50 isnt much but the 40ah net is equal to a 120ah 'marine bat' at 30% dod so its my 'lfp starter kit'). It has an integral dig voltmeter that reads .1 less than my hand-held, that should be a good safety measure on the critical low end.
Iirc 13.5 would be a good resting top voltage for class A cells, 13.4 for 'used' cells? Im thinking of doing a 13.0-13.3 'window of usage'.
Time to get the Meanwell ps up and running. What did you use for an AC power cord?

paulz
Member
# Posted: 29 Dec 2021 15:14 - Edited by: paulz
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Congrats! I just use old desktop computer power cord. Should only be about 5a on the AC side. Yeah when I get to my cabin my bank is usually at 13.5 from sitting with solar charging and no load. It goes down to 13.2 shortly after powering up the cabin, then sits there, and sits there. I have seen it drop down into the high 13.1s on occasion. I have been using 3.275 per cell (13.1) as my sort of 'get concerned' number. Moving my panels to a better location has kept me from generator charging with the Meanwell lately, touch wood.

Make sure you put the Meanwell in 120v and put tape over the switch. I think I blew my spare one by having it on 240.

gcrank1
Member
# Posted: 29 Dec 2021 17:20 - Edited by: gcrank1
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Ive a swatch of Gorilla Tape ready to go on @115
Just to be sure....
ac input:
L=hot, N=neutral, FG=grd
LED probably comes on when plugged in.
I'll try the dc output +/- with my short set of battery cables c/w ring terminals.
Looks like the Voltage is adjusted with that little V-Adj screw. Spec says 15v output, in your experience with these what do you expect the default setting to be? Voc is going to read high, if its hooked up to the bat as load will bring it down but I dont want to spike it while looking for 14.1.

gcrank1
Member
# Posted: 2 Jan 2022 19:51 - Edited by: gcrank1
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Im giving the RhinoVoltz lfp 50ah a load test tonight.
Had its built in voltmeter bouncing between 13.3 and 13.4 and stable there for days.
Hooked it to my truck-stop travel mini-fridge that is supposed to draw just under 5amps.
Figuring I want to stay in the 'middle 80%' the math gives me 40ah's to use leaving the bottom and top 5ah's each for 10% either end in 'the knees'.
So at 5ah's per hour it should run 8 hours and stay above 12.4v that Rhino says is 14% capacity.
*Update: 11:40pm, 10 hrs and sitting at 12.6v, unplugged from the fridge and the meter jumped to 12.7v. For all practical purposes this seems to indicate this '50ah' battery has an honest 50a usable between the knees and is still running well above my prev self imposed bottom limit.
*Update: As of 7:50 this morning after it sat all night with no load came up to 12.8. As expected, within seconds of plugging in the mini-fridge it dropped to 12.7. There is no real 'bounce'recovery' like lead-acid when load is removed.
I know voltage is not a viable way to track soc of lfp but my interest is hours of use at x load from my est 90-95% top and a safe bottom, not tracking in between.
Next test will be recharge after this 10hr load.

gcrank1
Member
# Posted: 4 Jan 2022 23:55
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Thanx for the Meanwell, Paul! I got it running tonight and set it to 14.1v hooked up to the bat. All an easy do. Just gave it a short run with my dig-vom hooked up at the bat terminals.
Will look for my old auto amp-meter to hook in, dial the MW down to 14.0 (per Steve S.) and go for a recharge, monitoring closely. My target is 13.4v

paulz
Member
# Posted: 5 Jan 2022 13:45
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From what I have seen, charging amperage goes up as you turn up the voltage. You are probably in no hurry to charge though. When I was trying to get the full 40A capability into my bank I had to turn the voltage up to 14.6. I know 14.6 is listed as the charging voltage for my batts.

Some of my FLA chargers will show around 16 volts when not connected to a battery. So the question is, can the Meanwell voltage be turned up past 14.6 disconnected voltage, as long as the battery voltage while charging stays within parameters?

gcrank1
Member
# Posted: 5 Jan 2022 20:39 - Edited by: gcrank1
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I think it would, but likely be a bit dangerous; ie, once the bat hit top end it would spike the bms hvd? That isnt considerate of the lowly bms which is our last-ditch safety valve.
With my vom attached to the MW terminals while unattached/open voltage compared to having the bat attached and charging I only got a diff of about .1 less on charge at my target 14.0v.
The MW 15v as received had the adj turned full up, the voc maxed just over 16v so I turned it down to 14.5 (1/2 turn?) expecting when hooked up it would drop closer to my target voltage. It dropped but not much and I tweaked it in.
My Rhino Voltz battery is spec'ed to take up to 14.6 also. From info over at DIYsolarforum.com I determined that 14.6 to be well into the high knee, and too much for my comfort, so I backed off to Steve's recommendation. Seems that the consensus is we get 95% of the flat curve of LFP at a charge rate of 14.0-14.1 as the battery will settle out to 13.4-13.5 anyway, it justs takes a bit longer to charge than if the MW were up at 14.6, with its higher amps aggressive output.
However, that MAY be something to start at after a deep discharge; ie, crank it up for 15min?
I will give that a try next go-round

paulz
Member
# Posted: 7 Feb 2022 22:15
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Well it's night 4 in the cabin. I was using the juice pretty good today, and tonight we thought we'd fire up the big (45") TV and watch Crocodile Dundee. Noticed the LFPs were at 13.19, direct on the terminals, lower than usual. Seemed like a good time to try out the new 1000i Sportsman generator (peak watts, 800 continuous). So I hooked up the Meanwell to it and got an immediate overload and shutdown. Turned down the volts on the Meanwell until the generator would run without the red overload light. Turned on the Valence LFP software, they are getting right at 4 amps each, 16 total. So that's all this little generator is good for charging my bank. Does that compute? 16A x 13V? Plus the Meanwell using some too I guess.

gcrank1
Member
# Posted: 7 Feb 2022 22:53
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I guess the proof of the pudding for you is that the genny will only support X load at a given soc; a variable depending upon usage.
I am curious how my Lil-Champ 1750/2000 inv-gen will run the MW when my Rhino is at maybe 30% soc.
Fwiw, after running my mini-fridge load I let the bat sit a day? then hooked up the MW on the grid. At 14.0v my old automotive 'hold on the wire' ammeter read about 26a. That isnt the 40a 'rated' but the MW isnt turned all the way up either; I expect it may peak at the 40a if the setting is at the 16v? Im resolved to leave it set at Steve's suggested 14.0 (for the wise) and just take whatever amps it puts out.

paulz
Member
# Posted: 7 Feb 2022 23:16 - Edited by: paulz
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Yes, the MW will only put out 40A at or near full voltage in my experience. I think I got about 30 at 14.6.

Well I just shut down the genny. Got the bank up to 13.3. I was able to crank up the MW a bit before the red light kicked on but I don't want to overtax it. It's so quiet and fuel sipping I don't mind running it for a longer period.

I was getting 7-10A from the solar today at peak time but also ran the shop lights, sawed some wood, took a long shower, plus the usual draws of the fridge, wifi, cabin lights, USB stuff.. I'm sure the bank would have been fine tonight but it's hard to sleep thinking about it.

Steve_S
Member
# Posted: 8 Feb 2022 07:02 - Edited by: Steve_S
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There is a new Thread started last week on DIYSolarForum which may be of interest to some of you. It grew very quickly with a Gold Mine of Answers and a lot of things people rarely consider that should be.

Best LifePo4 charge controller settings known to man for Maximum Service life and Minimum battery stress!!! 5,000-10,000+ cycles?

gcrank1
Member
# Posted: 8 Feb 2022 17:00 - Edited by: gcrank1
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Boy, did that grow quickly!
My takeaway is:
3.5v per cell / 14.0v for a 12v is safe for the bat and efficient for usage.
.2C to .4C amps for recharging wont stress the bat(s), and you can charge at a higher rate if you have to.
Ie, 100ah at .25C will be 25amps. If you have 2 bats in parallel they split the recharge amps.
When it is Cold; ie, near to freezing and below dont recharge until the battery has had time enough to get saturated warm up. You can draw off it, just keep it gentle.
Some bats have an honest number of amp hours and some dont; ie, if labeled as 100ah and built with 120ah of cells you can pull that 100ah's out and still be 'between the knees'/that 10% above and below the mainline. Just try that with a FLA!
Even a less than optimum LFP is better than a good FLA, ah's to ah's total.
When you are getting down toward the bottom pay attention and maybe keep the heavy loads off. The LVD of the inverter, if using one, may trip out before the bat BMS does, or not, but staying above the BMS cutout is a good idea. Even if you dont and it shuts the bat off it is likely to recover (not a disaster) just dont make a habit of it. Going 'too low' is better than going 'too high' on the recharge! (thus the 14.0v top setting, it will still get you 95%+)
Storage is better cool than hot. Store at 50ish% soc. Plan ahead from storage for use and top up recharge as needed, it wont take long, LFP is far faster than FLA.

paulz
Member
# Posted: 9 Feb 2022 09:31
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Quoting: gcrank1
Boy, did that grow quickly!
My takeaway is:
3.5v per cell / 14.0v for a 12v is safe for the bat and efficient for usage.
.2C to .4C amps for recharging wont stress the bat(s), and you can charge at a higher rate if you have to.


Yes, and many varied opinions.

Is the 14.0 the max voltage the battery should read? In other words, if the MW is set to 14.6, and your batt is at 13.2, it will take some time for the batt to read 14.0, at which time you disconnect, or is the 14.0 what you set your MW to?

Steve_S
Member
# Posted: 9 Feb 2022 11:28
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Quoting: gcrank1
Some bats have an honest number of amp hours and some dont; ie, if labeled as 100ah and built with 120ah of cells you can pull that 100ah's out and still be 'between the knees'/that 10% above and below the mainline. Just try that with a FLA!


Going to expand a wee bit on this.
Most BMS' have a Delay for LowVoltDisconnect, this is to allow for a Load Sag when the battery pack is low. The default delay is usually 10 Seconds, which allows the cell voltage to drop below the setpoint (usually 2.500Vpc) without disconnecting. Think of your fridge starting the start load is only a second or two. In such a case the cells will typical recover and keep going "UNLESS" they are already really close to LVD anyways.

There are numerous teardown vids where the LFP Battery pack guts are shown. I would like to point out that all the "Quality" Prebuilts & assembled packs most typically will build their ##Volt/100AH Batteries with 105AH cells. This pretty much guarantees that the customer will get their 100AH without fail and will operate within the Specs & Parameters they provide. The cost difference between 100AH & 105AH is a Pittance when buying volume, really it's very little.

The Little Zekret LOL byproduct.
In Cold Temps there is reduced Gross Capacity and the colder they get the less retained (not huge but it does add up) A Compensation to ensure full DRAW Capacity @ 0C is to up the Gross Capacity by 5% ! So the 105's serve that purpose as well and fulfills specification requirements.

Commercial Companies like Battleborn, Relion, EnerWatt, Volthium* and several others of "that" level have always done so, even those using the Cylindrical LFP. *Volthium uses Canadian components. I believe so does Rolls Surette with their fleet of LFP Offerings (Kaching ! BTW)

Now companies like SOK and similar are also doing so and with considerably improved design, materials and at better pricing no less.

In that thread, I also discuss the cells & charging in Real World Cold and how even 1 Celsius Temp Differences between packs has an effect on charge & discharge rates. If people are unawares of these points they may think they have a fault or problem, when it is the temp conditions that are at hand.

I felt that was a Good Thread to link here because there is a Good Overall Coverage of several things that come into play with charging/discharging.

BUT I NEED TO BE CLEAR !
Every system is unique & different and has its own "Personality". This even boils down to the Brand & Model of the Cells. While they may all be LFP, every company has its own "Special Recipes" and while the cells may appear identical on the outside, how they are wrapped/rolled and the quality of the materials between varies. It's just like everything else. Therefore it is best to always defer to the Manufacturer's Docs/Specs for the batteries/cells you are using, even minor differences can create "peculiarities".

What are the chemistry & manufacturing differences between say Energizer Brand & Duracell AA Batteries? Both are AA, both same voltage etc but inside they are slightly different.

ICC
Member
# Posted: 9 Feb 2022 11:48
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Quoting: paulz
Is the 14.0 the max voltage the battery should read? In other words, if the MW is set to 14.6, and your batt is at 13.2, it will take some time for the batt to read 14.0, at which time you disconnect, or is the 14.0 what you set your MW to?


If 3.5 volts per LFP cell is the maximum you want the cell voltage to be then you set the charging controller to that limit, in the case of a nominal 12 volt LFP battery that is the 14 volt figure.

One could set the controller higher but then we become the ultimate controller and what's the point in that? Part of the idea of solar is to be independent of the power grid, but at the same time have the system safely run itself so we can be concerned about other stuff or just have fun. Why trade watching the electrolyte levels of an FLA for having to watch voltage?

paulz
Member
# Posted: 9 Feb 2022 12:13
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Quoting: ICC
If 3.5 volts per LFP cell is the maximum you want the cell voltage to be then you set the charging controller to that limit, in the case of a nominal 12 volt LFP battery that is the 14 volt figure.


Yes, very true. The MW I was referring to is an AC to DC adjustable power supply we have been using for grid or generator charging. I, and gcrank I'm sure, closely monitor voltage while charging this way. But is it OK to set the unloaded voltage of the unit higher, say 14.6, and disconnect the battery once it reaches 14.0?

I turned down the limits on my SCC yesterday after reading that link above.

ICC
Member
# Posted: 9 Feb 2022 13:06
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I believe you could but, if it was me, I would not trust myself to remember. Or the constant worry about missing the cutoff point would drive me nuts.

But then I believe our battery bank is larger than anyone else's here and an error could cost me more than I care to think about.

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