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Small Cabin Forum / Off-Grid Living / Li Battery Charging
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paulz
Member
# Posted: 9 Nov 2021 11:42 - Edited by: paulz
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Yesterday at the cabin I unplugged my solar panels to test charging the battery bank (4 140ah 12v Lfp in parallel) with a 1000w generator and one of the 40 amp Meanwell power supplies I got, set at 14.6v.

With the batteries sitting at 13.1 or 13.2v, I was only getting about 1 amp of charge current. I've used this same charger and batteries at my house before I had solar, and it would give me up to 10 amps of charge. As they got up towards 14.6 volts the amperage would taper off to near zero. The voltage yesterday at the cabin only rose about .1v after an hour on the charger, and amperage stayed at 1.

I'm trying to understand the low charge rate

Steve_S
Member
# Posted: 9 Nov 2021 12:06
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Make & Model is prebuilt batteries, also a link to the product is helpful.

140AH LFP can typically take a Max of 70A Charge Rate. (0.5C) the EndAmps/TailCurrent should be 7A (0.05C)

LFP Generic Working Voltage is 3.000-3.400 Volts per cell or 12.0 - 13.6 Volts and really, the highest charge would be 3.500Vpc or 14.0V, simply because that is the Cliff Climb of the voltage curve and the cells will never stay there.

Please set the Meanwell to 14.0V and dial the Amps out to max. The odds are, because the batteries are already p-airly full, you may be triggering runner cells (weaker cells) that reach High Volt Disconnect (when cell reaches 3.650) and the BMS is cutting off charge.

If these have a Smart-BMS with a PC or Android app, that would be Most Helpful. Most "Dumb" BMS' have terrible settings as they use very broad generic settings.

paulz
Member
# Posted: 9 Nov 2021 12:51
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They are the Valence u27-12xp with built in BMS.

https://www.celltech.se/fileadmin/user_upload/Celltech/Products/Litium_laddningsbara/ Valence_Modules/XP_Module_Datasheet.pdf

The Meanwell power supply has no amperage setting, just a voltage adjustment. But it's advertised as 40 amp, and as I said has shown as much as 10 in the past at home when my batteries were just getting depleted at the cabin (no solar).

You may be right though. I was running two batteries, with a third on the shelf, for the last year or two. Recently I bought a fourth used battery from another source, maybe it's not up to snuff. They all blink the 'good' green led every 20 seconds and never go to yellow or red. But I did make up a cable and have the software to get cell by cell breakdown and history, I need to do that. If I can just find that darn cable.

gcrank1
Member
# Posted: 9 Nov 2021 13:25
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Ahhh, thanx Steve, Ive been thinking 14.2 for a setting; not too far out of line, but 14.0 will be my target now.

Steve_S
Member
# Posted: 9 Nov 2021 16:51
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many folks as you know bought & still buy these Valence Batteries and one very common thing between them is to be "reasonable" and stick close to "Working Voltages" for charge / discharge and as such I'd put the Low Volt Cutoff @ 11.0V @ Battery terminals which is 2.750Vpc.

Do correct for Voltage Differential from the battery terminals, the common DC BUS and finally at SCC & Inverter...

FYI the differentials will appear differently during Charge & Discharge.

- The inverter should be voltage corrected for the difference in voltage during "Typical discharge". (No charging coming from any source)

- The Solar Controller should be voltage corrected during Medium Charge rate being supplied. (No major discharge by inverter OTHER THAN the average "typical discharge". So you'll need to practice your DVOM Skills

BTW, as I recall the Meanwells are simply Fixed Voltage Variable Current with a max limit. I believe some have an adjustment pot and that there are interface kits which makes them into "smarter chargers".

paulz
Member
# Posted: 11 Nov 2021 11:40
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Thanks Steve.

Here's the spec sheet on the Meanwell I'm using. Gcrank1 has one too, if he ever gets LFP.

https://www.mouser.com/datasheet/2/260/scn-600-spec-1180098.pdf

I have my voltage cutoff set at 12. Yesterday after sunset my bank measured 13.23 right at the battery terminals. This morning, with the router, fridge, laptop chargers plugged in all night it measures 13.20. I know it's not a good way to determine SOC but good to know I'm nowhere near danger.

What may be happening is that when I ran just two batteries, they became more drained after a few days and charge amperage was higher. With four batteries sitting at over 13 volts they just don't need that much.

The DROK meter I have hooked up does have a SOC function but you're supposed to either charge or discharged the batteries all the way the enter the AH rating of the bank. Haven't figured out how to do that.

If you have and abundance of solar power at a given time, how does the SCC determine how much to give to the batteries? Strictly by voltage?

ICC
Member
# Posted: 11 Nov 2021 13:04 - Edited by: ICC
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Quoting: paulz
The DROK meter I have hooked up does have a SOC function but you're supposed to either charge or discharged the batteries all the way the enter the AH rating of the bank. Haven't figured out how to do that


I am not following that. It sounds like you are saying that DROK is saying to either fully charge or fully discharge the batteries. ??? Then enter the rated AH? You don-t want to discharge to 0%.

There should be a user setup menu that allows the rated data to be entered into the meter. Then the meter uses that base point to add or subtract as the batteries are charged and discharged. That is how the simple Whizbang Junior SOC system sold by Midnite Solar work, for example.


Have you a link to a user manual you can post?


Quoting: paulz
If you have and abundance of solar power at a given time, how does the SCC determine how much to give to the batteries? Strictly by voltage?


The user enters voltage set points and the charge controller uses that to figure it out.

gcrank1
Member
# Posted: 11 Nov 2021 14:01
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Im takin' notes Paul

paulz
Member
# Posted: 11 Nov 2021 17:03 - Edited by: paulz
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I'm mistaken, it's the Aili meter I have hooked up, the Drok is on the shelf. They do about the same thing. Can't find the Aili instructions (found the Drok though..). Here is an online capture but almost too fuzzy to read.

The part about draining the battery is on the lower left of the second page.

I did have this hooked up for SOC when the batteries were in my truck, I believe I just charged them 100%, hooked it up and entered the rated AH. But now with the batteries on solar I don't really know when they might be at 100%, probably not at all now in October sun.

Wait, found better images.
Screenshot_2021111.png
Screenshot_2021111.png
Screenshot_2021111.png
Screenshot_2021111.png


ICC
Member
# Posted: 11 Nov 2021 19:30
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Well, telling the user to fully discharge might work with lead-acid without too much if any noticeable harm, but it would be best to NOT do that with lithium.

gcrank1
Member
# Posted: 11 Nov 2021 22:38
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With either I wouldnt want to drop to bottom to get a baseline though the LFP would probably survive with less detriment.
It shouldnt be too hard to find a 'reasonable' top charge to set at if the bat-bank hasnt been hard cycled in a few days and had good solar days to recharge. Use that as the 100% soc and test it out.

paulz
Member
# Posted: 12 Nov 2021 17:26
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Been mucking with generator charging again today, can't seem to get more than a half amp out of the solar in total shade, thought it did better last winter.

1. Hooked up the Meanwell again same as yesterday, still only one amp charge, and my battery bank drained some over night.

2. Took the Meanwell down to the shop and tried it on a weak car battery. Still only 1.2amp max charge.

3. Dug out a regular 10 amp auto battery charger and tried it, 6-8 amps tapering down as it charged. At least it proves the little 900w generator is capable.

4. Brought the auto charger up to the cabin and hooked it too the LFPs, been cruising along at 2.2 amps.

Results confusing as usual. I don't know what's up with the 40 amp Meanwell, I guess I could hook it to a 12v 40 amp something or other and see if it takes it. But for some reason it doesn't seem to want to charge batteries much.

The auto charger is probably only doing a couple amps because the LFP bank is above what a FLA battery would be.

The battery bank is still at 13.2 so no immediate worry, but my usual draw is about 3-4 amps so it wouldn't go on forever. From the graphs I've seen the SOC is pretty constant at 13.2, the drops quickly.

Steve_S
Member
# Posted: 13 Nov 2021 07:29
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Ummm Sounds like the Meanwell has an issue. What do you have that is a respectable 12V Load that you could connect to the PS ? Even a Car Headlamp will do as the High Beam can draw some pretty respectable amperages. This is just to see IF the Meanwell can deliver the amperage. Per the specs you posted the 12V Model 600 will output a max of 50A, so it should certainly handle a High Beam Bulb....

paulz
Member
# Posted: 14 Nov 2021 15:14
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Quoting: Steve_S
Ummm Sounds like the Meanwell has an issue.


While I still had the car charger on the Valence bank, I noticed it has an 'engine start' switch. I turned that on, kicked the charge up to 4 amps, ran it for about half an hour. So I know the batts will take it.

Brought the Meanwell to the city, was just getting ready to test it when I notice the 110/220 switch was in 220! I don't know when it got switched, might have been the problem, going to get some tape over it. Anyway got a car ammeter and a couple of headlights, only got up to about 10 amps but the Meanwell powered them fine.

More to follow.

gcrank1
Member
# Posted: 14 Nov 2021 17:27
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Boy, I hate it when that (switch move thing) happens!
Bet it works fine now

Steve_S
Member
# Posted: 14 Nov 2021 18:57
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Quoting: paulz
I notice the 110/220 switch was in 220!

Damn, well sounds like the meanwell is working now.

paulz
Member
# Posted: 18 Nov 2021 11:44
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Welcome to the Small Cabin/Solar forum.

Maybe we need a Solar category.

So, I've got the Meanwell on 115v input now. ,doubled the output to the battery bank but still only 2+amps. Batteries were at 12.10 this morning. I hooked up the auto charger too so now I've got 6 amps going in. That charger is on the 50 amp jump start setting. So why am I not getting more charging, it's a mystery.

And my solar stinks right now. I would go cut down some trees but it's the clouds and fog at the moment. I measured amperage at each of my parallel strings, about .01a each, so I'm getting a half amp charge there.

Oh well, it was a great summer... 4 of these 140ah Valence LFP batteries should take a whopping charge. Maybe the internal BMS is limiting?

At least the little 900w inverter generator is humming away and not giving any grief.

travellerw
Member
# Posted: 18 Nov 2021 12:20
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Quoting: paulz
So, I've got the Meanwell on 115v input now. ,doubled the output to the battery bank but still only 2+amps. Batteries were at 12.10 this morning. I hooked up the auto charger too so now I've got 6 amps going in. That charger is on the 50 amp jump start setting. So why am I not getting more charging, it's a mystery


Whoa.. 12.1 is "knees" territory.. You are way down at the bottom and need to be careful. I never took my LiFePo4 cells that low. My disconnect was higher than that.

There is definitely something wrong. With the cells that low you should be able to pour in max amps. Since you have 2 chargers that seem to be behaving similar, I would guess its the batteries. However, if you have access to a power supply, I would set it to 13.8v and see if you can max its current.

I know nothing about those batteries or BMS.. but a BMS should not limit the in current unless its gone into disconnect mode.

gcrank1
Member
# Posted: 18 Nov 2021 12:32
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My understanding of the '50amp boost' chargers is that that do the high amps for a short time then kick back to whatever the charger's regular high setting is so they arent blowing up batteries.
Never checked one out to know.....
I agree that with multiple 'chargers' giving similar low results the issue isnt the chargers.
Even so, as a 'control' Id test the chargers with a drawn down FLA bat (ol' reliable fall back tech?).

travellerw
Member
# Posted: 18 Nov 2021 12:56
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Quoting: gcrank1
My understanding of the '50amp boost' chargers is that that do the high amps for a short time then kick back to whatever the charger's regular high setting is so they arent blowing up batteries.


Good Catch GC.. You are probably right.. Its a 6A charger with a 50A boost.

Steve_S
Member
# Posted: 18 Nov 2021 15:20
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Get your Digital Multimeter out, Hook it to that Boost Charger, measure the Voltage during "Boost Mode" and the Amperage (hopefully you have a clamp meter for it).

A Schumacker Boost Charger was used by a well-known YT Video Guy, he ended up roasting 16 Cells (Massive Bloat) and they were trashed quite quickly... It pushed harder than if doing a DeSulphate Run which CANNOT ever be done to LFP.

The Valence BMS' I believe will throttle charge below 10C/50F as LFP will charge from 0C but only limited till 10C/50F.

If at all possible get the software for the BMS' and monitor them when attempting to charge to see what the state of the cells etc are in Real Time.

For those that forget... These Valence Batteries come up all the time from Medical Equipment and similar. They are USED and in various states of wear, some terribly abused and others rarely cycled (which can be bad too if sat discharged too long). They are typically replaced under the service agreements that vary but typically I think it is 36 Months as this is flagged as Critical Equipment, but likely depends on the service contracts.

paulz
Member
# Posted: 18 Nov 2021 15:32
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Quoting: travellerw
Whoa.. 12.1 is "knees" territory.


WHoops, typo. 13.1. Sorry. Yeah, 12.1 I'd be in panic mode. I think my cutout is 12.5.

Good point on the start mode kickout, probably the case. It is a 2/10/50 charger though, so ought to do 10 continuous.

Well all is better in mudville now. I went down and worked in the shop all morning, the overcast gave way quite a bit, came back to an 8 amp charge at the cabin. Bank at 13.25 with the wife watching the boob tube.

paulz
Member
# Posted: 19 Nov 2021 23:23
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This is so confusing! Overnight my batteries dropped to 13.0. We were leaving for the city so I pulled two of the four batteries and brought them along. I found the cable to hook them up to the computer and read the diagnostic data before charging. As you can see, voltage is 13.05. The cells are fairly even, but look at the Cell Limits, they appear to be very low but the SOC is 98%. The other battery is virtually the same. What am I missing?

Now, back to charging. Before I left the cabin I fired up the genny and auto charger. This time it went up to 6 amps instead of the 4 amps previously when the bank was at 13.1. So, as expected, the lower the battery voltage the more amps the charger will give it. But it's not getting near the 10 amp output of the charger.

I found in the Valence literature they do say charger at c/2, 70 amps. But if I get a higher amp charger is it going to work or still only charge at a few amps? I have both batteries on Meawell power supplies now and again about 2 amps going in, the Meanwell being a 40amp model. I just don't understand..

It would be fantastic if I could recharge them in a couple of hours generator time this winter instead of dragging them home again until the sun shines.
v17.JPG
v17.JPG


Steve_S
Member
# Posted: 20 Nov 2021 01:39
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CELL LIMITS ! That is what is clobbering you !

Cell Spread to 5
Cell Min mV is at 3261 set that at 2750
Cell Max mV is at 3263 set that to 3500

Battery thinks it is FULL at 3.263 which is 55% is Real World.

paulz
Member
# Posted: 20 Nov 2021 05:20 - Edited by: paulz
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Wow, thanks Steve! I didn't know I could change any parameters, but it is letting me enter values in those fields, and I guess they will take affect. But before I do:

Who would have put those values that are in there already? And, oddly, these two used batteries I am working with at the moment I got from different sources over a year apart, yet those cell limits are set the same. Default? And these cell limits are more than just information, they actually control how much they can be charged?

I don't see anything about setting the cell limits in the manual, would you please have a look? I just don't want to do anything I am not supposed to.

http://dicksbluebirdbus.x10host.com/Valence%20XP-Power-System-User-Manual-Rev-4-8.pdf

paulz
Member
# Posted: 20 Nov 2021 08:36
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I was poking around on the DIYSolar forum, found a thread that mentioned trying to change the cell limits, by a member named Morth:

I played around with the numbers in the limits section and it looks like those can't really be changed. I changed the values, but the red boxes still turned on based on what the old values were, not the ones I had set. These may need to be set using the Valence external BMS.

Also, there are some other screen captures in that thread that show the same cell limits as mine shows, so perhaps they come that way.

https://diysolarforum.com/threads/valence-software.249/

Steve_S
Member
# Posted: 20 Nov 2021 08:52
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The guys at DIY talking about the Valence Batteries know a Boatload more about those than I do....

I saw those number and it just leaped out at me, but the images on DIY have similar settings, so what the heck do I know.

I read that there was issues with software versions versus BMS hardware or something but that was quite some time ago.

paulz
Member
# Posted: 20 Nov 2021 08:58
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I just found the 'Valence XP Super Thread' on DIY. Just finished page 1 of 21 pages! So I have some reading to do..

Geez FLAs are simple..

gcrank1
Member
# Posted: 20 Nov 2021 09:37
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Like anything new there is a learning curve, remember when you tried to learn the violin!

paulz
Member
# Posted: 20 Nov 2021 09:43
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Well I just joined the DIY forum and posted my charging issue. Hope they go easy on me..

At least it lessens the burden on you guys.

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