diy solar

diy solar

This guy claims lead acid is superior to Lithium Iron Phosphate in solar applications

harpo

Good at many things, master of none
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PA, FL

I have followed this guy for some time. He appears to be an engineer of some sort.

He presents a case as the title indicates that for the money, lead acid is superior to Lithium Iron Phosphate. I am not expert enough to put holes in his theory so I am asking all you guys what is wrong with his experimental design?
 
For off the shelf he may have a point, especially if he's using Battleborn. But if you're making your own banks using prismatic cells then it's going to be much cheaper to go LiFePo4.

For example, I replaced 2 Lifeline AGMs 100AH with 4 271AH prismatic cells and ended up paying about the same for more energy storage in a smaller space* with less weight.

Another thing to consider is that with faster charging of Lithium you are potentially able to harvest more energy.

*Also when using prismatic cells, the volume figures he's citing change a lot.
 
Define "better". If you have the battery indoors where lead acid batteries are venting into your living space then no, they are not better. If you need a battery that requires little to no maintenance or where weight is an issue, lead acid is not better.
If up front cost is an issue, lead acid is better.

Is pecan pie better than pumpkin pie for Thanksgiving?
 
I didn't hear him mention sulfation. That's the common failure for a LAB. LABs require a greater than 100% charge to prevent sulfation. That's virtually never done in a RV environment. My LABs usually lasted 4 years before needing replacement.
 
Agree with all the above assertions... "better" is relative for your individual use case.
The video tee's this up as a comparison of the "3 most popular options" (by his definition), so already his video scope is extremely narrow.
I'm in the Lithium vs. the Lead-Acid camp, personally.
 
More Ah in a smaller footprint, less weight, less maintenance, more cycles. I'll take LiFePO4, even with the low temp charging limitation.
 
I made a comment on the video with multiple points. Battleborns are heavy and expensive (but are still cheaper than lead acid). And yeah, even if you baby a lead acid, you will have some shorted cells.

He made the argument that lead acid can last 4500 cycles at 20% dod. Which would require buying 5X more lead acid batteries. Which would make it cost much more than even the most expensive lithium packs (simpliphi for example).

He has some other videos that are good. But I don't think he has used lithium batteries before. I don't think he understands how they work, or the current market of the packs.
 
He made the argument that lead acid can last 4500 cycles at 20% dod. Which would require buying 5X more lead acid batteries.
I'm afraid you did not get it. In most cases of off-grid use, 20% dod is just the regular daily cycling when you get a sun-charge the next day.
You MUST dimension your battery much larger anyway so that you can bridge a week of snow, really bad weather, or whatever mishap...
Since that do not happen every time, a few deeper discharges in a year (which may happen) will not impact the lifetime that much.
Telecom companies are still on lead-acid. For a reason.

Of course, if you use your battery just to buffer a few hours of day usage and discharge it to 70% each time, you get another picture.

But the average usage in off-grid MUST include a lot of safety margin, just due to the unpredictable nature of the weather, so yo need to purchase this capacity anyway.
 
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Here is a link to the data sheet for the SIND 06 610, since it is the one that looked superior in his video.
https://www.trojanbattery.com/pdf/datasheets/SIND_06_610_DS.pdf

Couple of things that jump out right away that he didn't talk about.

First, the Peukert effect, ie loss of capacity due to internal resistance. He gives this battery's capacity as 6 volt and 610 amp hour, which would imply that it can supply about 3.5 kwh of energy. However, that rating only applies if you slowly discharge at 6.1 amps for 100 hours. If you want to draw energy from the battery at 30.5 amps, the capacity drops to 2.8 kwh and at 60 amps 2.5 kwh. So if you take his recommendation that you discharge it to only 25%, at a 30 amp rate, its capacity is only going to be 0.7 kwh.

This compares with the lithium cells, which are often rated at discharge rates of 1 C, which means that the battery is completely discharge within the hour. This would mean that the Battleborn could provide 1.2 kwh or energy even if you discharged it at 100 amps.

Then there's the charge current. The Trojan SIND 06 610 data sheet says the maximum charge current is 13% of the C20 discharge rate. The battery nominal capacity is 610 ah, so C20 is 30.5 Amps, and 13% of that is about 4 amps. THIS SEEMS RIDICULOUSLY LOW. Can someone tell me if I'm misunderstanding something or doing this wrong? I assume at higher rates it begins to off-gas or lose water more rapidly.

This compares with LiFePO4 cells that are often allowed to be charged at 0.5 to 1 C. So you could probably charge the Battleborn at 50 amps. (the spec sheet on their website is really light on data compared to the cell datasheets)

Finally on cycle life. The Trojan's datasheet says they can get 7000 cycles if you only discharge them to 25% capacity. However, in the foot notes, there is a big caveat to this. This is only true if you operate the battery at 77° or below. If you operate the battery at 95° F each cycle counts as two cycles, so the battery life is only 3500 cycles. The interesting catch is that the temperature chart says that the battery capacity is reduced below about 83° F. At 70° F the capacity is 90% of nominal.

This compares to the LiFePO4 batteries that are usually rated at their 3500 cycle lifespan going to 90% to 100% of their discharge capacity. The video really short changes lithium here by saying he would only use 60% of the capacity.

So what does this mean? If you have a system in place to cover an occasional outage where your current draw will be within the capability of the Trojans and you will have days to recharge, and otherwise it just sits there on a float charge, then the SIND 06 610 batteries might be a great deal. There is a reason why they exist. However, if you want to come home in the evening and crank on the AC and induction cooktop at your off grid home every night and then have your massive solar array fully charge the batteries even if you only get two hours of sun the next day, then you will be very disappointed in the Trojans, and a LiFePO4 pack will be much better suited to your use.
 
Oivey I just watched this guy's video and I hear such Pre-conceived and ill-informed notions OM !
Clearly he has not done Due Dilligence in his research and his opinons are a tad off kilter...

Wo WHO paid him for this ? I mean, seriously ? There is a sponsor lurking or maybe he is sponsor shopping.
 
So what does this mean? If you have a system in place to cover an occasional outage where your current draw will be within the capability of the Trojans and you will have days to recharge, and otherwise it just sits there on a float charge, then the SIND 06 610 batteries might be a great deal. There is a reason why they exist. However, if you want to come home in the evening and crank on the AC and induction cooktop at your off grid home every night and then have your massive solar array fully charge the batteries even if you only get two hours of sun the next day, then you will be very disappointed in the Trojans, and a LiFePO4 pack will be much better suited to your use.
Yes, it all depends on what usage you intend to make of the installation.
But if you dimension your off-grid system such as discharging the battery at C/5, it will run dry after less than 5 hours and you will surely get into trouble if you get a full week of bad weather days.
Excepted, of course, if it is used at a cabinet where you just come for the week-end and will not come at all, if the weather is bad.
 
@rin67630, you make a good point about how an off grid system would be sized. I'm looking at battery specs a lot lately because I want a system where, at my most conservative power use, I can go four days without sun. So, in that case, the C rate on discharge wouldn't be a problem, and I did evaluate some lead-acid options.

Where things fell apart was on summer night use and winter recharging. In the summer when I know I'm way over paneled, I want to be able to run the air conditioner all night and use my appliances like I don't care and then have a full charge in 24 hours. While in the winter I'll have to be conservative, when I get that one sunny day during the week, I want to have a high enough charge rate to restore the system so that I'm ready for more clouds.

I also have to admit that its all hypothetical for me at this point. I've purchased about everything I need except the battery system but I don't have the real world experience yet so people should take my thoughts with a grain of salt.
 
The Trojan SIND 06 610 data sheet says the maximum charge current is 13% of the C20 discharge rate.
I multiply the C20 rate by .13 to see the max current.

I have Trojan Solar SPRE 06 255. Each has six volts with 255 amps at 100 hour rate. At the 20 hour rate that drops to 229 amps. I have four of these batteries, two in series two in parallel. This comes to 458 AH at 12 volts. This means the max current I can push is 59.4 amps.

I have not been able to push that many amps because my 1000 watts of panels has maxed out at 612 watts of production, which means if I was in the absorb phase at 14.7 volts, the batteries received 41.6 amps, if the entire amount went to charging the batteries, and not pushing the other 300 watts of loads I had hooked up.
 
I multiply the C20 rate by .13 to see the max current.

I have Trojan Solar SPRE 06 255. Each has six volts with 255 amps at 100 hour rate. At the 20 hour rate that drops to 229 amps. I have four of these batteries, two in series two in parallel. This comes to 458 AH at 12 volts. This means the max current I can push is 59.4 amps.

I have not been able to push that many amps because my 1000 watts of panels has maxed out at 612 watts of production, which means if I was in the absorb phase at 14.7 volts, the batteries received 41.6 amps, if the entire amount went to charging the batteries, and not pushing the other 300 watts of loads I had hooked up.
So you're saying that they mean to say that the maximum charging rate is 13% of the capacity listed for the C20 discharge rate?

That yields a more reasonable charging limit, but if that is the case, Trojan has a really poorly worded data sheet.
Thanks for letting me know how you calculate it.
 
That yields a more reasonable charging limit, but if that is the case, Trojan has a really poorly worded data sheet.
I have really noticed a lot of bad or missing documentation with other products. Trojan is not nearly as bad as others. A PWM charge controller I have has nearly no documentation and my solar panels say the female MC4 plug leaving the panel is positive or negative, depending on which of the company's documents you use.

I do use 13% of the capacity of the listed C20 rate.
 
@rin67630, you make a good point about how an off grid system would be sized. I'm looking at battery specs a lot lately because I want a system where, at my most conservative power use, I can go four days without sun. So, in that case, the C rate on discharge wouldn't be a problem, and I did evaluate some lead-acid options.

Where things fell apart was on summer night use and winter recharging. In the summer when I know I'm way over paneled, I want to be able to run the air conditioner all night and use my appliances like I don't care and then have a full charge in 24 hours. While in the winter I'll have to be conservative, when I get that one sunny day during the week, I want to have a high enough charge rate to restore the system so that I'm ready for more clouds.

I also have to admit that its all hypothetical for me at this point. I've purchased about everything I need except the battery system but I don't have the real world experience yet so people should take my thoughts with a grain of salt.
Even if you are ot in Europe, the european PVGIS is an incredible tool for planning off-grid systems.
PVGIS it does not permit deep links, so select your location and off-grid.
You enter your configuration and you get a lot of information amongst others the probability to run off battery per month.

Running 4 cloudy winter days off-grid is tough... you need a LOT of batteries or a really microscopic consumption.
 
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I'm afraid not. 13% of the C/20 current is correct. The Trojans are back-up batteries. Their design does not emphasis a fast charge.
I think you and I are saying the same thing. I can charge my 458 AH of Trojan's at 59.4 Amps. This is not a fast rate. If I discharged these batteries 50% and charged them it would take 4 hours at the full rate to charge them. I do not consider this a fast rate.

Other places say in general to recharge Flooded lead acid at no more than the 10% rate. Trojan gets a little more specific with theirs and recommends 13%
 
Even if you are ot in Europe, the european PVGIS is an incredible tool for planning off-grid systems.
PVGIS it does not permit deep links, so select your location and off-grid.
You enter your configuration and you get a lot of information amongst others the probability to run off battery per month.

Running 4 cloudy winter days off-grid is tough... you need a LOT of batteries or a really microscopic consumption.
Very cool tool! I gave it a quick try and it does have data for my area.

I'll have to compare it to PVWatts from NREL.
 
I have Trojan Solar SPRE 06 255. Each has six volts with 255 amps at 100 hour rate. At the 20 hour rate that drops to 229 amps. I have four of these batteries, two in series two in parallel. This comes to 458 AH at 12 volts.
C/100 is just the right rate to run for 4 days off batteries.
With 458 AH at 12 volts and max 50% DOD you can feed... ~28W for 4 days!

If you have 1KW of panels, you may get on a heavy cloudy winter day 60 Ah additionally, so you could push your mean power consumption to a whoppy 33W! Youpeee! :p
 
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I remember watching this guy's videos a long time ago when I blew up my first Xantrex 2000w Hi-Freq inverter and trying to learn a thing or two. I saw this video come across my subscription feed and only watched about a minute before realizing it's probably not worth my time. Felt more like a preaching video as compared to much of an educational one.
 
PVWatt does not seem to provide anything to evaluate off grid systems, does it?
Not to my knowledge.

It does incorporate weather data to help provide realistic daily production figures in the table it produces for a given PV array at a given location. I'm guessing that PVGIS does the same, so I am curious to see if they calculate similar production expectations.
 
Not to my knowledge.

It does incorporate weather data to help provide realistic daily production figures in the table it produces for a given PV array at a given location. I'm guessing that PVGIS does the same, so I am curious to see if they calculate similar production expectations.
Take a look at it, does much more, provides extremely detailed results, and use powerful databases, down to integrating the influence of mountain's shadows. Anyhow here in Germany, the previsions for days with empty batteries were fairly accurate.
 
Knurlgnar is back?!?! what? I was a regular watcher of him but he had a 5 year gap in posting videos.

I was ready to dismiss it as a shill video with a non-listed paid-for-by-trogan but he had informative good videos 5-7 years ago...
 
I'd like to point out that FLA companies are far & few between, many are now owned by holding companies which retained the "brand" label.

I've replaced my FLA (now a backup bank) wih LFP which cost e less than if I was going to replicate the FLA installation again. With LFP though I got DOUBLE the storage capacity. 428AH FLA versus 910AH of LFP. LFP charges Faster and requires no watering, babysitting or extra care like FLA. The old adage that everyone always "kills" their first set of FLA is very true, are you willing to chuck big bucks away in < 5 years ?

Compare costs and lifespan plus useable capacity and it really is a no brainer.
If buying Full ON commercial LFP like SimpliPhi, Relion, BatleBorn, Rolls Surette or Trojan LFP your in deep dollar country BUT that is giving you a min of 10 years warranty and properly fully Matched, Batched, Binned identical cells.

Tesla 24V Packs are even selling for around the $1500-$1900 mark but I would not use an EV battery for an ESS, voltage curves just don;t quite cut it with regular equipment.

IF considering options, I very strongly urge you to do due diligence & research your options and consider / weigh them out. It is your wallet to do whatever you want to do but a happy spouse when you do not throw away good money is VERY VALUABLE ! and can make your life so much easier...

PS: FLA offgasses, must be in a vented cabinet and not within a residential space. Some folks ignore or go around it and later regret it...
 
I’ve set up dozens of fully off grid systems, you size your batteries to cover one nights useage - and run a generator if your batteries aren’t fully charged at sundown.

This is by far the cheapest (and most reliable) method for power off grid.

Average power use where i live is 20kwh/day, most of my systems are sized for 10kwh overnight. I haven’t seen an off-grid system capable of doing this for less than 100k without a generator. My system is less than 30kAUD.

LiFePO4 is a fraction of the price of Pb.
 
I’ve set up dozens of fully off grid systems, you size your batteries to cover one nights usage - and run a generator if your batteries aren’t fully charged at sundown.
I design unattended off grid instruments. Running a generator is not an option.
LiFePO4 is a fraction of the price of Pb.
For that usage, being discharged every night, there is no alternative to LiFePO4.
 
It totally depends on your situation, what you are comparing, and how. For my particular situation, the maths indicated there was no other choice than lead-acid, but depending on what my goals were and how I'm comparing it the answer would have been different.

For example, are you comparing x dollar vs x dollar, x Ah vs x Ah, or something entirely different like x Lb vs x Lb when specifying the battery(s) to compare... and then there is usage. So many variables, what is best for me probably won't be best for you, and if it IS probably for an unrelated reason. A comparison between a lead-acid and a LiFoPE battery bank will be very different if with the same usage you are comparing $20,000 worth of each, than comparing 1000Ah of each, or 1000# of each. Your mileage may vary.
 
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On the data sheet they say: if charging time is limited, contact us...
You may charge faster for a couple of hours.
I know the RV world fairly well. Despite the documented 10% or 13% charge rate, most RV'ers consider 30% of C20 the max charge rate for LAB.
 
After having to haul four 12V 220AH AGM batteries out of the basement my back thanks me for replacing them with LiFePO4.

I just don't get how you can justify the high maintenance of a FLA compared to LiFePO4. Even an AGM I consider dangerous since mine died by filling the basement with hydrogen gas.
 
After having to haul four 12V 220AH AGM batteries out of the basement my back thanks me for replacing them with LiFePO4.

I just don't get how you can justify the high maintenance of a FLA compared to LiFePO4. Even an AGM I consider dangerous since mine died by filling the basement with hydrogen gas.
Just speaking for myself, the difference in delivered price between the FLA and the LiFePO4 paid for the rest of my system. If I was rich I'd have looked at it differently... maybe.
 
When I bought my FLA, anything Lithium was Insane to Lunacy cost wise. Now with LFP at PARITY.. it's a no brainer.

Pssst.... some of us, who live in regions which can be 40C in Summer & -30C in Winter and can make do very nicely with < 4kWh usage a day even with short sun hours in winter may have a slightly different view / opinion. Rule One of Offgriding, conservation is far cheaper than generation & storage.

Weight example.
8 280AH cells @ 5kg each = 40kg/88.1lbs. That is one 24V/280AH/7.168 kWh battery pack.
X2 of above is 560AH, 80Kg/176.2lbs.

8 Rolls Surette S6 L16-HC, (formerly S-550) 55.5 kg (122 lbs) = 444kg/976 lbs. for 24V/956AH gross / 428AH net @ C20.

That says a heap on it's own with price parity for 16 LFP cells vs 8 Heavy Leads.
 
When I bought my FLA, anything Lithium was Insane to Lunacy cost wise. Now with LFP at PARITY.. it's a no brainer.

Pssst.... some of us, who live in regions which can be 40C in Summer & -30C in Winter and can make do very nicely with < 4kWh usage a day even with short sun hours in winter may have a slightly different view / opinion. Rule One of Offgriding, conservation is far cheaper than generation & storage.

Weight example.
8 280AH cells @ 5kg each = 40kg/88.1lbs. That is one 24V/280AH/7.168 kWh battery pack.
X2 of above is 560AH, 80Kg/176.2lbs.

8 Rolls Surette S6 L16-HC, (formerly S-550) 55.5 kg (122 lbs) = 444kg/976 lbs. for 24V/956AH gross / 428AH net @ C20.

That says a heap on it's own with price parity for 16 LFP cells vs 8 Heavy Leads.
At parity with what? Seriously I could have had 986Ah @ 48V delivered to my rural location with California sales taxes paid for less than $5000? I had no Earthly idea. Please point me to deals like that.
 
At parity with what? Seriously I could have had 986Ah @ 48V delivered to my rural location with California sales taxes paid for less than $5000? I had no Earthly idea. Please point me to deals like that.

270-280ah cells drop shipped from china, with support from a US member. ~$1700 per 48v set. 3 sets and all the benfits of LFP vs FLA
 
Pssst.... some of us, who live in regions which can be 40C in Summer & -30C in Winter and can make do very nicely with < 4kWh usage a day even with short sun hours in winter
How do you deal with -30C and LiFePo?
With FLA you can refrigerate the shaded and insulated batteries since you have excess energy anyhow.
But in the winter with only scarce energy available, I can't afford to warm up the LiFePo batteries > 0C.
 
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