Turnergang
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Nope I lied. I meant to say marine something or other. lol that will tell ya how new I am
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highwaypirate
New Member
Lol that's quite alright! When I first started out, I went through batteries on a monthly basis... just to realize I needed a 'deep cycle', not a 'marine hybrid'.
Turnergang
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Ya these are trash. I didn’t help them at all by running to zero. Multiple times. I’ve learned that’s not good for lead acid. lol
Those existing batteries have about 1.7kwh of 'theory' storage- but any L/A battery, only about half that is actually available (unless you want to be replacing batteries monthly lol)- depending on your location, where I am in N/E Australia- that 50w panel on a PWM charge controller would only make about 180 watthours a day, but those existing batteries if run 'flat' ie 50% DOD) need over 900Wh to recharge them- so it would take at least 5 days to recharge them...
:-O
See what I mean about 'decorative'...
:-O
See what I mean about 'decorative'...
highwaypirate
New Member
On a FLA/SLA battery, I wouldn't even go down to 50% SOC. My golden rule for those chemistries is 12.2V at rest is dead enough lol.
Turnergang
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Absolutely see. I live in Las Vegas. I’ve been watching Will and have purchased 2 375 panels. Just making small purchases at a time. But going full lithium over til me
Turnergang
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Ya it’s been 11.5v at least twice. I’ll be junking them soon.
seneysolar
Solar Addict
I did an inexpensive upgrade to a camper a few years ago. Golf cart 6V's will fit in the boxes and I did an Anderson connector for a portable solar panel setup (200watt) - under $500 all in
The owner camped off grid full time an entire summer like this. (No air conditioning)
Golf cart batteries are available everywhere and be cycled heavy. Good "beginner" batteries to learn on and screw up a few times without spending too much.
The owner camped off grid full time an entire summer like this. (No air conditioning)
Golf cart batteries are available everywhere and be cycled heavy. Good "beginner" batteries to learn on and screw up a few times without spending too much.
Turnergang
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Great info. Thank you. That’s kinda what I’m thinking to start with.
highwaypirate
New Member
I absolutely agree. When I do 'back-yard' builds for testing, I always use a small AGM battery over a LiFePO4. In case something should go wrong, a FLA/SLA will be a lot more forgiving and cheaper to replace. I call these 'learner batteries'. They are also good to have around in case a LiFePO4 needs to be 'jump started' from over discharge.
The number of charge cycles for L/A (well all batteries actually) increases the shallower the discharge- L/A is about 800-1200 at 50% DOD, about 1500-2000 for 25% DOD, and about 2500-3000 at 10% DOD (but then you functionally only have a battery bank capacity 1/10th of the 'label' capacity...)
That's why LFP makes better economic sense- yes they cost about twice the price of L/A, but because they can handle an 80% DOD and still get 5000 charge cycles, reduce it to 70% DOD and you are looking at 7000 cycles- you pay twice as much initially, but get 30% more actual capacity, and 800-1200 cycles against 5000... reduce both down and you get 7 times more actual capacity, and twice the number of cycles (3000 against 7000)
Plus for mobile use like campers- they are far smaller, and a lot lighter- important in a camper...
highwaypirate
New Member
Hence why I use Mini 100AH LiFePO4 batteries in my already-tiny CR-V. Though for testing small projects or other devices, I would be a little hesitant to use an expensive battery. That's why I still like to have an AGM battery under 18-22AH.
Another thing to look at is your charge controller- ye old fashioned PWM will make 30% less total power generated per day than a MPPT- and thats with well matched panels, buying the wrong panels (say ones with a 44v Voc) will see the output plummet on a PWM- that combination on a 12v battery bank could see your panels making less than HALF their rated power!!! (panel wattage gives no clue to the Voc, they can be anything from 18v Voc to up over 70v Voc...)
eg these two are only 10w difference, yet look at the difference in the Voc ratings!!!
Put the 200w on a PWM on a 12v battery, and it will make about 150w under STC, put the 190w one on a PWM on 12v and it's output is a tiny 70W- from a 190w panel!!!
Put either on a MPPT charge controller and they will make their rated output to within a 1/10th of a watt in STC conditions (thats them up the top right- 25C cell temps on the panel, 1000w/m^2 and 1.5 atmospheric mass (ie this varies according to your latitude (further from the equator it increases, higher up in altitude it decreases...)
See why a PWM really is a bad choice???
eg these two are only 10w difference, yet look at the difference in the Voc ratings!!!
Put the 200w on a PWM on a 12v battery, and it will make about 150w under STC, put the 190w one on a PWM on 12v and it's output is a tiny 70W- from a 190w panel!!!
Put either on a MPPT charge controller and they will make their rated output to within a 1/10th of a watt in STC conditions (thats them up the top right- 25C cell temps on the panel, 1000w/m^2 and 1.5 atmospheric mass (ie this varies according to your latitude (further from the equator it increases, higher up in altitude it decreases...)
See why a PWM really is a bad choice???
seneysolar
Solar Addict
Well yes, LFP is great BUT..... most budget LFP can't be put in a wet environment like the existing plastic box out on the hitch. So you might be building a new weather tight box or taking up storage inside. If moving inside, now you're rewiring battery cable. Then you need to consider the factory charger/converter, most have really high constant charge voltages, not a multi stage charge algorithm.
So, its not a simple one for one battery swap in many cases.
Price of L/A batteries these days- I wouldn't be leaving them in a plastic box on the drawbar anyway lol
They'd need replacing long before they were 'worn out'...
highwaypirate
New Member
While I agree with your post on the differing voc, both of my 175 watt Renogys run very well on my PWMs. If your panels are identical, I can't think of any reaosn why a PWM would not work (it's been powering my life for 4 years)... but if you mis-match your panels, you WILL find you aren't utilizing the full potentials of your panels.
For me, I am wasting a few watts, I'll admit that my Renogy panels despite being the same wattage and models are different in size and voc, but its not insanely noticeable where I would need to switch over to MPPT. And if I felt those missing watts (maybe 5 or 6) would be needed, I have 10 more PWM controllers of the same kind. It all depends on what your needs and situation requires; a Victron was not satisfactory enough for mine.
As I said- it depends entirely on the Voc of the panel concerned- they vary hugely...
With a PWM, they have to be 'voltage matched' to the battery voltage- looking at those two panels above- only the 200w ones would be a good match to a 12v battery bank- and even then they would make a lot less than a MPPT would in the same lighting conditions...
The 200w has a Imp of 11.12A, and with a PWM charging the battery at 13.8v, thats a maximum of 153.4W- from a 200w panel...
The 190W one is much worse- its Imp is only 5.2A, so again charging at 13.8v through a PWM controller, thats only 71.7W!!!
Replacing the PWM with a MPPT and changing nothing else, the 200W panel increases from 153.4W up to 200.16W (25% improvement), and the 190W panel increases massively from that tiny 71.7W up to 190.32W (a 250% improvement...)
So panel selection is critical with PWM- of these four panels below, only one (the 200w) is suitable for use with a PWM on a 12v battery bank...
His new 375W panels could have a Voc of anywhere from about 22V up to well over 70v
(here's a 410W panel with a Voc of 81.4V!!!)
Putting just a single one of those on his PWM charge controller onto a 12v battery will result in dismal performance to say the least- 13.8V x 5.82A = 80W... from a 410W panel!!!
Putting a MPPT controller on the same panel, feeding the same battery, will give you 70.4V x 5.82A = 409.73W- over 400% more power from the same panel...
Many people assume that 'all panels are the same'- far from it... and a mismatched system can cripple your output power...
Something many newbies are unaware of...
(especially in something like a camper, where mounting space is extremely limited- even that 25% loss using a PWM instead of a MPPT can mean the difference between having power at night, or sitting in the dark...)
highwaypirate
New Member
My system has been kept as basic as possible, since I've had a difficult time finding controllers that use ring terminals (my SUV goes down some of the worst roads in Canada.. and other fields). Not to go off the topic, but I am curious about something: wouldn't a panel with such a high voltage ruin a PWM the second it got power flowing through? I haven't seen too many PWM controllers capable of handling 40V+ panels (mine are limited to 38V arrays).
seneysolar
Solar Addict
This article from victron is a great read, they produce both types pwm and mppt. You really cant make a generalization of "30% less".
Edit : "cant"
I currently have a Midnite Brat hooked up to 2 parallel Trina 335w panels that have a Vmp of 34v. Voc is not as important as Vmp as noted on the power curve. Match Vmp as close as possible to your charge voltage and you design your own efficiency into the setup. On my 24v system, (charging at 28.8v) its very efficient. I haven't noticed a difference from my Victron 100/30 that I removed. (Just an experiment)
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