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gcrank1
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# Posted: 20 Feb 2022 17:02 - Edited by: gcrank1
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To clarify, I have 24vdc incoming to the MPPT SCC that has its own transforming to 12 for my bat-bank (it can also feed a 24v bank if I had it). Dont most all MPPT SCC sense the incoming voltage or have a user set voltage to define the bank?
The only advantage I know of is the 24v allows me smaller ga. wire and/or longer runs. It would work the same if I had a 24v bank to run to whatever, but the wire size for max scc output to the bank would still be big.
At one time I thought if I started new or over Id go 24v but then Id surely be locked into buying a 24v bat or bank at 2x the price of my 12. And I can always find an affordable 12v battery in an emergency!
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paulz
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# Posted: 20 Feb 2022 17:10
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The other advantage to 24v is it doubles the charging wattage limit.
Yes my CC have three options, 12v, 24v and Auto. I've always used Auto but changed it the other day after travellerw said the Epevers sometimes switch on their own.
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ICC
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# Posted: 20 Feb 2022 17:21
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Charge controllers usually auto sense the battery voltage. That is why the instructions normally tell you to connect the CC to the batteries first.
And the manual should have a section, maybe a table, that shows the maximum PV panel wattage that can be used. That should increase as the battery bank voltage is increased. Moving from a 12 volt battery bank to a 24 volt battery should double the PV panel wattage as paulz noted.
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gcrank1
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# Posted: 20 Feb 2022 18:58 - Edited by: gcrank1
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But since Amps x Volts = Watts on a given array the diff between 12v and 24v is 1/2 the Amps at 24v (thats why we can use smaller ga. wires and/or go farther).
A 24v array into the SCC set to feed a 12v bat-bank will have those '1/2 the Amps' bumped up for the 12v bank but there will be some little losses through the process, yes?
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paulz
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# Posted: 20 Feb 2022 19:17 - Edited by: paulz
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Here's the page from the Epever manual. Dunno what all the reverse polarity means, why anyone would do it
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ICC
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# Posted: 20 Feb 2022 21:23
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The amperage rating on a MPPT charge controller is the maximum amps the CC can put OUT.
The table paulz uploaded shows that for the 10 amp model the charging power is rated to be a max of 130 watts at 12 volts (battery) and double that for a 24 volt battery. Most CC will be using the charging voltage for the battery and will most often round off that voltage figure. Some mfg, like Victron will use 14.5 volts for a 12 volt battery system. The Epever table uses 13 volts for some reason. (130 watts / 10 amps = 13 volts).
Using the 10 amp Epever model as an example if we were to connect 200 watts of panels to its input and it was in bright fll sunshine the unit would only put out 10 amps. The watts from the PV panels that were not used would be wasted as heat.
The maximum PV array column lists 390 watts on a 12 volt battery. If that was exceeded the CC would probably be damaged by overheating. All that assumes the CC has adequate air flow to provide the needed cooling.
If the CC was connected to a 24 volt battery instead of the 12 volt, the table shows that it could now be connected to more panels. 260 watts worth of panels in bright sun should put out 10 amps into the 24 volt battery.
Sometimes you have to search the manual to find these panel limits but they should be there.
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ICC
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# Posted: 20 Feb 2022 21:26
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Quoting: paulz Dunno what all the reverse polarity means, why anyone would do it
People make errors, sometimes in an honest accidental way, sometimes in ignorance or carelessness. The mfg might build in some protection against reverse polarity hookup. Then again they might not.
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gcrank1
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# Posted: 20 Feb 2022 23:45 - Edited by: gcrank1
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Imo 13.0v to charge a fla 12v battery is horrible; I doubt a typical fla battery or agm could get fully charged on a day to day basis. Maybe if not deeply cycled and/or lots of days between use it could finally get there?
Isnt 13.0 basically a trickle charge or float voltage? Fine if you get bulk and absorb first but Id want more, especially for LFP; ie, the prev mentioned 14.0 is desired, at 13.0 LFP will settle out well below getting to the knee leaving a lot of capacity/potential untapped.
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paulz
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# Posted: 22 Feb 2022 10:24 - Edited by: paulz
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Quoting: ICC People make errors, sometimes in an honest accidental way, sometimes in ignorance or carelessness. The mfg might build in some protection against reverse polarity hookup. Then again they might not.
Yes, thank goodness. I have yet to make the mistake on my solar but have done it many times on my FLA battery charging bench, where I switch the charger from batt to batt every day. The charger just shuts off, not even a spark. The Epever verbiage though, giving a reverse polarity wattage spec, makes it sound like some kind of option.
Last night, again after day 3 of moderate usage, I noticed my bank had dipped under 13.20V, actually 3.29x per cell, verified by plugging in the Valence software.
Still figuring on 3.275 as the 'must charge' figure, I resisted the urge to charge via generator before going to sleep, and left the usual 2-4A draw going all night. Surprising this morning they are still at 3.29x per cell, so apparently there is still quite a bit of life left under 13.20V, my previous 'get concerned' voltage. Jibes with this SOC chart, showing 13.10-13.20 being in the 40-70% range.
The indications though are that my system is still not able to cope with day to day moderate usage, at least not in February. Time to play around more with panel orientation, tree cutting.. I do have the array down at the shop charging better and should be able to cut down on using the cabin bank down there.
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gcrank1
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# Posted: 22 Feb 2022 10:43 - Edited by: gcrank1
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Ive seen a line graph of LFP that I like much better.
And yes, ime brief experience with LFP being at 13.2 there is Nothing to worry about, especially if that is an active use time voltage (under load) rather than a resting voltage. You will be reading the voltage sag while active even with LFP.
There is a lot of available power between 13.2 and 13.0. and even more to go.
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paulz
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# Posted: 22 Feb 2022 11:15
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I have my voltage disconnect set at 12.5, I should probably up it. Although under a temporary heavy load I guess it could see 12.5. The Valence internal BMS will shut them down at some point, I think even lower.
It's one thing to kill a $100 car battery by leaving the lights on, another with a couple grand of LFPs. 
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gcrank1
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# Posted: 22 Feb 2022 11:28
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Do you know where your BMS is set to trip?
Id want at least a couple 10ths volt above that to not be making it trip (wear out prematurely).
I dont expect to be regularly 'going that deep' so that would be my 1st level safety valve in the redundant system.
For our recreational cabin use we could probably go deep discharge and not really hurt the life cycle of the LfP for the next 10yrs. But Im not the kind to take my bikes to redline all the time either (just once in a while to know if they have any issues or not  )
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Steve_S
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# Posted: 22 Feb 2022 11:53
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You will NOT KILL LFP by allowing them to reach 0% SOC or 2.500Vpc - This is Lithium Iron Phosphate,
Welcome to the New Reality !
BTW I do it occasionally "On Purpose" without ill effect. I will allow them to reach "My Disconnect point - 0% SOC" which is 2.750Vpc / 22.0V (I'm 24V)" and then use a combo of Solar & Genset to Hard Push Charging the bank to my 100%SOC which is 3.425Vpc /27.4V.
2) The Internal BMS will CUT OFF Output once 0% or programmed Threshold is reached, that's its job.
3) The AH Delivered comes from the "Working Voltage Range" which is 3.000-3.400 and not the Full Range from 2.50-3.65Vpc. and yeah, the batts can sit at 3.2## for days LOL, takes some getting used to.
4) IF you are really nervous, then set CUT OFF on the Inverter to 11.0V (2.750Vpc) and call it a Happy Day.
Damage related to "Charge State" occurs WHEN:
- If Cells are below 0C/32F and being charged.
- If they are discharged to BELOW 2.500Vpc
- If they are charged ABOVE 3.650Vpc
As long as these conditions do not exist, you will not encounter problems or issues.
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paulz
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# Posted: 22 Feb 2022 12:02 - Edited by: paulz
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The internal Valence BMS shuts the battery down at 8v  Not programmable. They do have LEDs that turn from green to yellow as a warning, if you happen to be looking at them.
I left the power on for a couple days once, had only one battery connected, no solar yet, got back and it had shut down. Talk about a sinking feeling. But it recharged and doesn't read any different that the other 3 now. I didn't have the Victron shutdown dingus back then. It's really my first line of defense. Think I'll kick it up to 12.8.
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gcrank1
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# Posted: 22 Feb 2022 14:21
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Thanx Steve! 
Working voltage range, Great way to put it; for us with 12v LFP thats:
12.0 to 13.6 volts; That is Lots of Hours/loads.
We can be set free of the old FLA constraints on DoD/SoC IF we let ourselves be.
For me, only using some 30% of my FLA capacity to get max lifespan from the bank the liberation to LFP means 3x as much, the 100ah LFP is equal to 300ah of FLA. The math is easy.
So Steve, with LFP is it 'go deep or why bother'? ()
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paulz
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# Posted: 22 Feb 2022 14:28
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Yes thanks Steve. My previous post, with the Valence pic, I thought I posted prior to yours. I've noticed this before, sometimes I'll post, then notice a new to me post just above it. Changes the flow of info sometimes.
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Steve_S
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# Posted: 22 Feb 2022 16:22
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What I love about LFP is the Lack of worry about DOD ! That just does not factor in really. Running between 2.750 to 3.400 Vpc gives you the Full Meal Deal with Appetizer & Desert included.
Paulz, I cant tell you much about the Valence Software but from what you say they can customize them so they likely have software that will "write" setting to the flash ram on the BMS. I Highly doubt that regular folks can get their hands on that BUT Ya Never Know.
Valence though does ONLY USE Grade A+ Cells due to their intended functions (Hospital Equipment & the like) and if memory serves they are indeed premium cells.
Yes some LFP can drop to 2.0V BUT they cannot stay there for any length of time. They can also take up to 3.9V as well... BUT if folks attempted such with "any old LFP" there'd be hard costly lessons learned.
LFP is a Generic Term in a sense for Lithium Iron Phosphate which is a "Family" of chemistries with various differences but are still LFP Chemistry... Example like the Winston Yttrium Doped Cells, still LFP but LYFP and they have different (wider) voltage range & can be charged even at -20C and can discharge up to 3C or 5C pending on version.
You know guys, this is a LOT of info and there is a crap load more but is it relevant ? Not so much really. but does fill in some of those quirky questions.
I do the Deep Discharge & Hard charge process to reset all of my battery packs & their BMS' (each has a Shunt for measurements) and it also helps to sync things up and balance out.
This is ALL About to change as well, as the whole enchilada is being reconfigured with new BMS' and much more for everything. Once done I am gonna have a Heck of a Fire Sale on goodies for the DIYer.
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paulz
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# Posted: 5 Mar 2022 10:30 - Edited by: paulz
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More charging calamity, this time the other way! Got to the cabin yesterday, MT50 showing 13.7v. Cool. Powered up the cabin, went outside to work on something for a couple hours, came back in, the red light on the MT50 is on! Battery Over Voltage! First time that has happened. Showing 14.7v. Yipes! Turned on the inverter (my new power killer), that turned the light off and voltage down.
How could this happen, I had just turned the over voltage cutoff down from 14.6 to 14.4. Went into the parameters, back at 14.6, in fact all parameters were back at default.
I have the Epever Windows software working and played with it the other day but didn't go into the set parameters menu. Maybe somehow by disconnecting the MT50 and plugging in the laptop several times it got confused and went back to default?
Anyway I set everything back down to the values I posted a few posts ago, doesn't seem to have done any damage, except my nerves. Probably be awhile before I plug in the laptop again..
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gcrank1
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# Posted: 5 Mar 2022 19:51 - Edited by: gcrank1
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Thats scary, maybe when it hiccups it defaults?
The bms should save the bats, that is what its for, right?
Im wondering when I will get to charge my new 100ah LFP, lol.....been just taking it to the cabin when we go (solar is currently (pun intended) disconnected), hooking it up to inverter inside and running whatever I want; led lights, ceiling fan all the time, usb and tool chargers, even the 750w toaster. Weve been there 4 times that amount to about 18hrs total and the bat that started at 13.3 maybe just edging 13.4 is still at 13.1 (resting) after today's visit!
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paulz
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# Posted: 7 Mar 2022 09:59 - Edited by: paulz
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Quoting: gcrank1 Thats scary, maybe when it hiccups it defaults?
Maybe. I have to unplug the MT50 meter to plug in the Laptop software, which I did a dozen times to get it working, maybe that goofed it up. Hmm, maybe a Y connector would work for both simultaneously..
Before I got solar I had my LFP behind the seat of my pickup, with an attached cord and connector. The cabin had a 20' 10g cord coming out I would plug in when we got there, and back at the grid same going to the charger. Worked quite well, except when I drove away and forgot to unplug..
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paulz
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# Posted: 16 Jan 2024 10:46 - Edited by: paulz
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Whew, old thread.. I went through it again because recently when adjusting the output voltage on the two Meanwells I have connected (parallel), I noticed I had wired the two PAR terminals together. In all the documentation I have seen it does not explain what that does, make the output voltages equal (even though they are still adjustable by the screw) or something else? Hoping Steve or Traveler might know.
Also, one has the GND/INH and VCI/VCO terminals connected as shown in the photo, other one not. Probably left over from how I got them.
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Steve_S
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# Posted: 16 Jan 2024 10:56
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Here is the diagram for my PAIRED 600-12's which provides 50A @ 24V charging.
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paulz
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# Posted: 16 Jan 2024 12:15 - Edited by: paulz
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Hmm, mine are labeled just as in the post above yours, PAR, GND, INH, etc., not like your diagram.
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Steve_S
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# Posted: 17 Jan 2024 06:56
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I don't know why they would be that different but I think there are so many Meanwell Knock Offs let alone all their different versions (Genuine Meanwell's) it's likely.
I found that I had to adjust each one as "12V" not combined and then paired them and rechecked the output voltage to ensure they were correct. I can tell you that the adjustment pots are twitchy (on mine anyways)
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paulz
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# Posted: 18 Jan 2024 07:32 - Edited by: paulz
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Quoting: Steve_S 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
I tried to change to your recommendation. The Valence software lets me change the numbers but as soon as I reload the software it jumps back to the old numbers. No ‘save’ icon I can find. Maybe Valance decided that’s what they should be..,
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