Hi there, so I've been getting by for the past 6 years on my small system which consists of a 24v 225 (Trojan T105re) bank, a pair of Canadian solar 250w panels, a classic 150, a Samlex 600sa and a Solinba 3kw LF psw inverter, and an iota dls 2724. The batteries are giving up the ghost now, and being my first battery bank, I'm fairly satisfied with what I've squeezed out of them. But it's time to move on, and do a little upgrade while I'm at it.
So I'm thinking I want to move up to the Trojan 6v 375ah premiums to make a 24v 375ah bank this time. I'm going to want more panels. I have the midnite combiner box, and have been running those two csp panels in series. My question here is, looking at the panels available now, the numbers don't match well in either voltage or amperage. I'm looking at some ~ 350+w modules from Alt-E (as they are close enough for me to go pick them up at their warehouse).
The current panels in use:
VMP: 30.1
Imp: 8.30a
VoC: 37.2
Isc: 8.87a
The ones I'm looking at: seraphim 375w
VMP: 39.1
IMP: 9.6
VOC: 48v
ISC: 9.96a
I would like to pick up 4 such panels.
Is there a way that all six of these panels will work together through the classic 150? Could I pace 2 each of the new panels in series, and run the 3 strings (CSPs (x2 in series), Seraphim (x2 in series) and seraphim (x2 in series) into the combiner box? Or how should I do this?
Quote from: BlackwaterPark on March 10, 2020, 09:03:56 AM
Hi there, so I've been getting by for the past 6 years on my small system which consists of a 24v 225 (Trojan T105re) bank, a pair of Canadian solar 250w panels, a classic 150, a Samlex 600sa and a Solinba 3kw LF psw inverter, and an iota dls 2724. The batteries are giving up the ghost now, and being my first battery bank, I'm fairly satisfied with what I've squeezed out of them. But it's time to move on, and do a little upgrade while I'm at it.
So I'm thinking I want to move up to the Trojan 6v 375ah premiums to make a 24v 375ah bank this time. I'm going to want more panels. I have the midnite combiner box, and have been running those two csp panels in series. My question here is, looking at the panels available now, the numbers don't match well in either voltage or amperage. I'm looking at some ~ 350+w modules from Alt-E (as they are close enough for me to go pick them up at their warehouse).
The current panels in use:
VMP: 30.1
Imp: 8.30a
VoC: 37.2
Isc: 8.87a
The ones I'm looking at: seraphim 375w
VMP: 39.1
IMP: 9.6
VOC: 48v
ISC: 9.96a
I would like to pick up 4 such panels.
Is there a way that all six of these panels will work together through the classic 150? Could I pace 2 each of the new panels in series, and run the 3 strings (CSPs (x2 in series), Seraphim (x2 in series) and seraphim (x2 in series) into the combiner box? Or how should I do this?
I would go after new panels that match (or at least are very close) the specifications of the older ones. The only way this would work would be if you use solaredge optimizers or emphases inverters to match the two odd power levels in a gird tie system. Of course you're battery based.
When you combine the lower power panel to the higher power ones, they won't play well together. The lower wattage panels will get their voltage raised to match the new panels, and in the process you'll lose some current.
Wonder if there was (is) a reason why you chose the premium Trojan battery over the L16?
If you had the $$$ I'd add more panels. The biggest killer of lead acid batteries is not getting them fully charged.
Just my opinion, take it for what you paid for it.
mike
Those premium 377ah batteries are L16s.
It's doable to simply get the new panels and just use those, and repurpose the old panels to some other system and task. I'm trying to find the appropriate panel wattage input to strike the best charge rate to the new battery bank. As I understand it, different batteries have ideal charge rates, and with FLA, a rate of 5-10% works well for longevity, all things being equal. I'm not sure how off base I am here. I was toying with the idea of getting a 3.6kw Simpliphi 24v battery, but at $3k, that still seems a bit exorbitant, even considering the charging and discharging efficiency gains over FLA.
You want your battery strings to be within 10% voltage of each other otherwise the MPPT won't work right.
So it doesn't sound like you can do it with your new and old PV. Midnite has a string calculator on their site to help in determining PV options for how many pv in series and strings.
The best option I could think of would be to get another mppt controller and use that on the two odd pv panels. But that might cost as much as just spending the $ for two more new matching pv panels ?
For the lead acid batteries the rule of thumb is that if you want your batteries to last the longest you don't want to use more than 20% of their capacity - the more deeper cycles you do that less cycles you will get in their lifetime. Of course proper maintenance for flooded lead acid batteries is also important - monitoring the water levels, specific gravity , and equalizing on a schedule or when needed.
The battery manufacturer will have the specs on maximum charge current, how many cycles you get based on depth of discharge, and all the proper charging setpoints. Vic on this group has written a lot in the past on flooded lead acid batteries - go to the first home page of the forum and do a search for his good advice. ( search only works for home page )
Larry
Thanks CC. Looking at your end tag, I couldn't help but notice your lead crystal batteries, something I had not hitherto heard of. Intrigued, I did a light search to look for basic merits, specs, and pricing. At your leisure, I would like to hear about your experiences with them, where you got them, and what the cost was. It looks like they are far cheaper than LiFePo4, but with many advantages over them.
Quote from: BlackwaterPark on March 10, 2020, 02:47:22 PM
Thanks CC. Looking at your end tag, I couldn't help but notice your lead crystal batteries, something I had not hitherto heard of. Intrigued, I did a light search to look for basic merits, specs, and pricing. At your leisure, I would like to hear about your experiences with them, where you got them, and what the cost was. It looks like they are far cheaper than LiFePo4, but with many advantages over them.
I got them because my battery dealer had them in stock when I needed them and also they have pretty good performance in cold weather - my batteries are in unheated area. They are pretty much just the same a gel battery but they make all those claims about the special gel means that they won't ever sulphate even if drawn down low and left there for awhile. Some of their claims about extra capacity are not that valid because no one is going to draw their batteries down to zero volts. If you look at their specs they are similar to lead acid in that you get longer life if you don't cycle them too deep . So far in the few years I have had them they seem to perform okay . No way of telling exactly what is going on with the chemistry inside a sealed battery since you can't take specific gravity readings.
I guess the proof will be in longevity of lifespan which I won't know for a long time. When I got them they were at a price comparable to other lead acid batteries . One thing I didn't like was no support from the Soneil - they have never responded to any of my email questions or even for more documentation. I gained some of my info from other battery names - if you look up Lead Crystal other places have more details. The best thing about them is I don't have to mess around with watering. Also it was easy to move them around when I picked them up since they were sealed. Other than that who knows if they are worth it or not. At the time I got them I never was able to find many discussions of experience from other uses. My battery dealer said at the time they used this type of battery in Africa a lot and they were having good success with them.
If I had a warm place for the batteries I would probably consider lithiums . Look in the battery section of the forums here - someone recently posted some lithium cells at a decent price and a bms controller for them that has lots of features and monitoring .
Larry
Thanks for taking the time to respond in depth. Very much appreciated. I've thought about building my own batteries, as I'm a real diy kinda dude, but I've got my fingers in more pies right now than I care for, and for the first time in my life, I've got more money than time. So I'm still seriously considering getting one or two of the Simpliphis...2 would run up to $6k, for a 24v 302ah bank, which I realize could get me a whole lot of lead acid. My back is in my house, and it's not like my house gets that cold. Being in Maine, off grid, I'm usually tethered to my dwelling for the winter months anyway. They claim 10k cycles at 80% did, and it would be nice to not have to care about whether my batteries are spending enough time in absorb or not, and all those other benefits of LiFePo4. I even my array could be smaller, as the batteries make much more efficient use of the incoming power.
So I'm looking at some Peimar 310w monos, and looking at the sizing tool, it looks like I can run 8 of them from the classic 150.
310w monos
VMP: 32.6
VOC: 40.7
Imp:9.51
ISC: 9.8
For a 24v battery bank, what's the optimal configuration for these panels to go in? As I'm redoing my bank as well, I have some leeway with what my new bank can be, and I would like to optimize it for the panel wattage from this new array... So if I stay with FLA (which I'm pretty sure I'm going to do), what's a good size bank for this pv array? I was thinking of either 4- 6v 375ah or 8- 6v 225ah.
Hi BlackwaterPark,,
With 8 of those PVs, and FLA batteries with an MPPT CC, there is really only one PV configuration -- Four strings of two PVs.
It looks like you are quite committed to a 24V system, due to inverters and a charger, so thinking about a 48 V battery bank, seems a bit leap.
Have not run the Classic Sizer, but, 8 of these PVs on a 24V system would essentially fully-utilize the Classic's charging capabilities.
The nominal maximum charge current at solar noon on a bright sunny day, of about 68 Amps would exceed most guidelines for most FLAs, in the target capacities that you are considering. With the WbJr accessory to the CC, you should be able to limit the charge current into the battery to the maximum amount you desire, for good battery health. And still have any excess current available for other loads (on the inverter).
The maximum PV output will depend on the Azimuth, and elevation angle of the PVs, shading, etc, as you know. So, the above guess of current may be incorrect.
System sizing really flows from the required loads on the system, when they occur, number of days with poor recharge power, etc. Am unfamiliar with the PVs that you are considering. You also know this.
But, IMO, you have done quite well with this original system. Six years, off-grid with your GC FLAs is quite good, especially if this is your first such system.
More later, Vic
Vic,
I think he was asking if 4 L16 batteries at 24v are better than having 8 golf cart type batteries at 24v - with 2 parallel of 4 in series for 24v.
The 4 L16 batteries would be better if that is what you are asking about since it is hard to have balanced parallel and can have charge discharge favoring one set .
Larry
Thanks for the input, Vic. Was hoping you'd jump in actually, being a very knowledgeable FLA guy. Strange as it may sound, I'm more of the thought, and position I suppose, to work my lifestyle around the power available rather than the other way around. For whatever reason, I've come to actually prefer that. Nonetheless, we've done ok here with the modest system we have been running, but I'm just ready to add some more without changing much in the way of my usage...I feel that in this way I can gain more system autonomy (using generator less) while possibly improving longevity overall.
I'm wondering now about the batteries. Now that I have a decent handle on how to maintain them (more or less), I'm looking at these two Trojan premium options;
Eight 6v 229ah (GCs) which would yeild 460ah for about $1600.
Then, there's four 6v 377ah (L16) , giving me 377 ah for virtually the same money.
Is there some inherent advantage to running the L16s? I'm guessing that running a single string in series has better charging characteristics than 2 parallel strings in series, but other than that?
Also, one thing I've noticed when only running 500w of panel into that 225a bank, equalization was rarely possible. I've heard that a lower charge rate, between 5-10% is preferable for lead acid longevity, but I found that it often took too long to get through bulk and into absorb, that getting into equalize territory was... Actually, I think I got through it a single time in all of six years. So is this to say it's perhaps better to go bigger on the bank and simply not discharge it as much? Even after six years, with all the accumulated experience, it still gets a little confusing when redesigning a system.
Again, thanks for your input sir.
If you want your batteries to last the longest you should only discharge them to 80% full ( take out 20% of capacity) .
What you need to evaluate is if the 20% is enough to run all your loads.
You can take more out of the batteries but then you have less total cycles so less lifetime of the batteries.
Trojan should have charts showing this and they should say in their specs what the maximum charge rate is.
My guess is you don't have to limit the input charge - once it gets to absorb the controller will be cutting back the current going to the batteries.
Larry
I suspect I'll be in the 30% discharge rate... Though I don't mind going lower really... I'd like to get another 6 years out of the new batteries, hedging my bets that LiFePo4 or carbon (or some other tech) will be more economical by then.
Looking at these panels, (with a Vmp of 32.6, VOC 40.7) it looks like they can work with my existing modules (Vmp 30.1, VOC 37.2), so if this is the case, would 2 strings of 4 (with 3 new ones and one old one per each string) work ok? I can't input that data into the classic tool on account of the two different sets of numbers.
Looks like you can do the different PV - you will probably pull the current down to the lowest panel ( old ones) and loose some power from the new pv .
Alt E did video series of hooking up different combinations of PV that were mismatched .
Take a look
https://www.youtube.com/user/AltEStore/search?query=mismatched+solar+panels
also look here
https://solarpanelsvenue.com/mixing-solar-panels/
If you do the math on the LiFePO4 you might find that it is just as economical if you consider you can use more of the capacity of the batteries so have small overall amphour rating pack. Of course you need to look at other considerations like how much surge you can pull at any time for inverter motor startups, etc. The lithium hold the voltage steady over their capacity instead of dropping down like lead acid do . I understand choices - lead acid is a known and lithium is not something many people have experience with. Lead acid are forgiving to higher and lower voltages where lithium isn't so a bms is needed. Anyway I am not saying lithium is the better choice but seems like prices these days are something to consider.
Larry
Hi Black..,
Two things:
1. When using different PVs in a series string, you want the Imp of each PV to be within 10%, maximum 5%, ideally.
2. Also, you need to watch the Voc of the strings. IIRC, you have a Classic 150. With three new, and one old PVs per string, the Voc at 25 degrees C, is about 152-ish V. In the Winter, a Cl 150, might never come out of HyperVoc (in Maine, IIRC).
3. AND, with that very large voltage ratio ( String Vmp vs battery V), the CC will loose some efficiency.
Forget the details of Imp of these two PVs, will check your earlier Post.
More later, FWIW, (Hi Larry). FWIW, Vic
Many thanks to both of you for weighing in on this.
Larry, I was looking at some LiFePo4 companies, and have dinner some basic math. Even considering the upfront cost, I would not have an issue going with the LiFePo4s, but for the fact that they only warranty their batteries of you have certain inverters, which are neither of mine. The ones that they do approve are all the big expensive ones that I just don't need, which would also add another $1500+ to the deal. I can't see spending $6k on batteries that do not come with a warranty, unfortunately. (This was in an ongoing email with Simpliphi, anyway...I haven't checked in with any others like Battleborn. Maybe I should). Additionally, because I'm still confused about what I've heard... I'm to understand that LiFePo4 doesn't like to be charged above 90%? Leaving the capacity gap a little less dramatic of that's the case. THREE times, dusting email exchanges, I asked Simpliphi to explain to me whether or not this was indeed the case, and the question went competely unaddressed. So I still don't know, but it kinda left a bad taste in my mouth.
VIC,
Perhaps a better question to pose to you would be to ask what I should be looking for to take maximum advantage of a single classic 150 in Maine? Then I can rebuild the bank around that array? I'm hoping to go to the AltE store (3 hours from me) and pick all this up by Friday...or civilisation collapses, whichever comes first, lol. I'm not worried about factoring in for my loads, I will work around what I end up building. I've been getting by just fine on less than what I'm upgrading to anyway.
yeah i wasn't talking about those expensive lithium batteries - more about ordering lithiums direct from China and installing your own BMS.
Look in the battery section of the forums here for a recent post. Everything is always a bit of gamble with lithiums.
Larry
Quote from: BlackwaterPark on March 16, 2020, 08:53:46 PM
Many thanks to both of you for weighing in on this ...
VIC,
Perhaps a better question to pose to you would be to ask what I should be looking for to take maximum advantage of a single classic 150 in Maine? Then I can rebuild the bank around that array? I'm hoping to go to the AltE store (3 hours from me) and pick all this up by Friday...or civilisation collapses, whichever comes first, lol. I'm not worried about factoring in for my loads, I will work around what I end up building. I've been getting by just fine on less than what I'm upgrading to anyway.
Hi Black..,
For a 24 V system, running PV String Vmps around 60-ish Volts should be close to ideal. For 60 cell PVs, like your targets for the panel upgrade, strings of two should be fine, and you will have no worry about excessive Voc. Also this is a good operating point for CC efficiency.
You could get some benefit in trying to use the two existing PVs on a PWM controller. This would give some charge, into the Absorb stage, but not contribute much with cold batteries in Absorb, and probably nothing contributed in EQE
EDIT: Should have mentioned, above, that if a PWM CC was chosen, the two PVs should be in parallel.<
This is my drive-by opinion, FWIW. Good Luck, Vic
Thanks Vic. I just ordered 4 of the Trojan premium 377ah L16s, supposedly optimized to be and to run in partial SoC better than typical FLAs, so I'll size up from there with the panels.
Looking at this Peimar panels, if I went with 3 strings of 2 panels, the sizing tool yeilds:
Rated pv power: 1860w
Pv array current: 28.53
Battery charging current@28.8v: 64.6
VMP: 65.2v
VOC: 81.4v
If I'm trying to stay within Trojans recommended 10-13% charging current, is this to say that the "pv array current" should be 37-49a?
The battery charging current at 28.8v goes way beyond that though.
With 4 strings of 2 panels:
Pv array current: 38.4a
Battery charging @28.8v: 86.1a
VMP: 65.2v
VOC: 81.4
Is the 8 panel scenario better than the 6 for this bank? If we are going by the "pv array current" metric, that looks to fit neatly into the 10% charge rate, of this is how that is supposed to be factored.
Hi BwP,
WIth 8 of the target PVs, would consider that the Cl 150 is maxed out.
Did not use the Sizer, just used the total STC power from 8 PVs, derated that to 80% of that total (at solar noow, PVs produce about 77% of STC in nominal WX conditions, in full sun). Divided that number by 29 V. 8X310=2489W. 80% of that is 1984W. At 29V this is approximately 68 Amps. This is just a simple rule-of-thumb.
There is an ability to limit the battery charge current in the Classic, using the WbJR. This is described in the Classic Knowledge-Base, here:
http://www.midniteftp.com/support/kb/faq.php?id=37
On my computer the this info seems very sluggish to access, and at times, the access simply fails. This may be some bottleneck, just now, or perhaps with my Win 10 system.
Believe that this battery charge current limit function will work with a single Classic.
Will look at the Sizer data for 8 310 W PVs.
Good idea, on the L-16s. Failed to comment earlier … Avoiding multiple strings of batteries is almost always better than trying to get Capacity with parallel battery strings.
Later, Vic
Quote from: BlackwaterPark on March 16, 2020, 08:53:46 PM
VIC,
Perhaps a better question to pose to you would be to ask what I should be looking for to take maximum advantage of a single classic 150 in Maine? Then I can rebuild the bank around that array? I'm hoping to go to the AltE store (3 hours from me) and pick all this up by Friday...or civilisation collapses, whichever comes first, lol. I'm not worried about factoring in for my loads, I will work around what I end up building. I've been getting by just fine on less than what I'm upgrading to anyway.
You better call Alt E before you drive down there - they just sent an email saying their customer pickup is closed now.
Larry
BwP,
Looking at four strings of two 310 W PV, shows that one Cl 150 is fully-utilized. Result Attached.
FWIW. Good luck, Vic
Yeah, I called them this morning and they had the warehouse pickup open. They must have changed that at some point today. Hopefully, they can still ship them to me in time, before even shipping is shut down, if that ends up happening.
I don't understand why it would bother them to have people call first and then come so they could bring the order outside for them to load ! Anyway hope you get your new PV and stuff to play with before you get shut in for awhile !
Larry
Thanks Larry. I'll at least have the batteries, though my 500 existing
watts will be rather meager for the bigger bank. But at least I've got the charger and lots of gas to keep them charged until I can get the panels anyway.