Sunfunkits show their true color

[chess-equality]

So what is the net? Never been arrested, safe to order from SFK?
What about speeding tickets, bankruptcy, or jay walking?

Just unfortunate, their kits are quite a novel product.

 

[houseofancients]

Just unfortunate, their kits are quite a novel product.

beg to differ , they are simply 3d printed enclosures bundled with bms and cells as kits

 

[wattmatters]

Just unfortunate, their kits are quite a novel product.

Seplos have kits as well.

 

[Just John]

1. He claims that the Ah measurements from the EBC-A40L is not accurate because there is some loss in the alligator clips. Wrong. The current is the current. All of the current is going through the entire circuit, even if there is some heat loss in the wire or the clips. There are watts lost because there is a voltage drop, but the current is the current. Basic circuit theory, and he doesn't seem to get that.
2. He tries to say that what matters is the Wh, and then he gets to whatever Ah he wants by dividing the Wh by whatever voltage he wants. The reason we measure capacity in Ah is because the voltage changes during the entire discharge. Ah is the only way to get a repeatable comparison between cells. Again, basic.

I can't speak for your knowledge, but watt hours is indeed how you would measure the amount of work that can be performed.

280 amp hours at 1 volt is not the same as 280 amp hours at 3.2 volts, not by a long shot. (280 watt hours versus 896 watt hours)

Fortunately, the tester measures both, and does all the calculations for you. The only difficult thing about measuring watt hours is keeping track of both voltage and current. If your tester doesn't have sense leads, it won't accurately measure watt hours.

That said, I gave up trying to understand where he was pulling these numbers and "nominal voltage" figures from.

 

[Horsefly]

I can't speak for your knowledge, but watt hours is indeed how you would measure the amount of work that can be performed.

Read again what I said. I agree that Wh is the correct measurement of energy. Ah is not really a measure of energy at all. The problem is, there is not a repeatable way to measure Wh when testing a cell, because the voltage varies during the entire test. Granted you can, by measuring the voltage during the whole test and apply some linear algebra, but none of the tools we have do that. So we measure Ah. That's why ALL cells are sold by Ah rating. The only way to compare two cells that are both nominal 3.2V cells is to measure Ah. Full stop. That is a fact.

 

[Horsefly]

That said, I gave up trying to understand where he was pulling these numbers and "nominal voltage" figures from.

And there you have the crux of it. Someone who doesn't understand how this works (for example, Mr. SunFunKits) believes they can get to the Wh by just multiplying the Ah by a "nominal" (average?) voltage. Not true. The voltage was not constant, and and average is only partially accurate in the middle / flat part of the curve, and completely wrong for the rest.

 

[Ampster]

The only way to compare two cells that are both nominal 3.2V cells is to measure Ah. Full stop. That is a fact.

I think that is an opinion unless I am unaware of the facts to which you refer? I will presume it is a strongly held opinion. I prefer to think in terms of Watt hours because that is how I am charged by my utility and how I measure my solar generation. Fortunately both my BMS and Inverter/charger report in kWhrs, my EVs consume kWhs and I often monitor miles per kWh.

 

[chess-equality]

Seplos have kits as well.

Yes I 've watched Andy review it.

 

[wattmatters]

The problem is, there is not a repeatable way to measure Wh when testing a cell, because the voltage varies during the entire test. Granted you can, by measuring the voltage during the whole test and apply some linear algebra, but none of the tools we have do that.

Any half decent energy meter does exactly this, reliably, consistently and accurately.

 

[wattmatters]

Yes I 've watched Andy review it.

I have a DIY friend who has ordered the larger one but will be using his own cells.

It will be a heavy bugger.

 

[Just John]

I think that is an opinion unless I am unaware of the facts to which you refer? I will presume it is a strongly held opinion. I prefer to think in terms of Watt hours because that is how I am chargedby my utility and how I measure my solar generation. Fortunately both my BMS and Inverter/charger report in kWhrs, my EVs consume kWhs and I often monitor miles per kWh.

The tester in question measures both, and even writes a nice data file if you wish to do your own calculations.

I have attached an example. Different chemistries can have different voltages, and the only accurate way to compare is via watt hours.
Certainly amp hours gives an indication if the chemistry is identical, but each vendor does tend to have their own "secret sauce".

 

[Horsefly]

The tester in question measures both, and even writes a nice data file if you wish to do your own calculations.

I have attached an example. Different chemistries can have different voltages, and the only accurate way to compare is via watt hours.
Certainly amp hours gives an indication if the chemistry is identical, but each vendor does tend to have their own "secret sauce".

I also use the EBC-40L. Yes, it does report watts, but anytime you insert voltage into a test of a battery (which you must to get Wh) you introduce some nuances because the sense leads may have a better contact in one case than another. A higher discharge current will result in a lower voltage at the same capacity, as the discharge curve changes with amps. Meanwhile, the amps will be the amps. The tester normally is used for constant current discharge, and the time it takes gives you a repeatable measure of the capacity of the cell. I've already said that when sizing a battery for a system, you should use nominal Wh, as it is the representation of the energy available (at a nominal discharge curve) in the system. It is different when you are trying to compare cells.

I'm not sure why you would talk about different chemistries, since the topic here is SFK cooking the results of tests to argue against Ray's tests of the same cell (in Ah, using the same EBC-40L). But, yes, if you are trying to compare LiFePO4 capacity to lead acid capacity (which will be subject to Peukert and so will be harder to compare anyway), then Ah are not appropriate.

But we are talking about LiFePO4 cells here, and in the case of SFK vs Ray, we are talking about the exact same cells. The manufacturers spec these cells in Ah, not Wh, and they test the cells in Ah capacity. I received EVE test results from Amy Wan on one of my orders, and there was no Wh discussed.

Anyway, I fear that some folks here are - perhaps inadvertently - giving credence to SFK's twisted argument about Wh. It's completely wrong, and the way to compare Ray's tests to SFK's test is with Ah.

 

[Just John]

I also use the EBC-40L. Yes, it does report watts, but anytime you insert voltage into a test of a battery (which you must to get Wh) you introduce some nuances because the sense leads may have a better contact in one case than another. A higher discharge current will result in a lower voltage at the same capacity, as the discharge curve changes with amps. Meanwhile, the amps will be the amps. The tester normally is used for constant current discharge, and the time it takes gives you a repeatable measure of the capacity of the cell. I've already said that when sizing a battery for a system, you should use nominal Wh, as it is the representation of the energy available (at a nominal discharge curve) in the system. It is different when you are trying to compare cells.

I'm not sure why you would talk about different chemistries, since the topic here is SFK cooking the results of tests to argue against Ray's tests of the same cell (in Ah, using the same EBC-40L). But, yes, if you are trying to compare LiFePO4 capacity to lead acid capacity (which will be subject to Peukert and so will be harder to compare anyway), then Ah are not appropriate.

But we are talking about LiFePO4 cells here, and in the case of SFK vs Ray, we are talking about the exact same cells. The manufacturers spec these cells in Ah, not Wh, and they test the cells in Ah capacity. I received EVE test results from Amy Wan on one of my orders, and there was no Wh discussed.

Anyway, I fear that some folks here are - perhaps inadvertently - giving credence to SFK's twisted argument about Wh. It's completely wrong, and the way to compare Ray's tests to SFK's test is with Ah.

I actually looked at the (few and sparse) data sheets available, and it is confusing.

The first cell result of my grade B cells (all I have in the 280 series) gives interesting results:

*1-5

D-CC

277​

896.08​

I.E. 277 amp hours, and 896 watt hours. The 896 watt hours is printed on the label. Which is the "rated capacity", the amp hours or the watt hours?

This is the spec sheet for the grade B cells I have:

EVE LF280 (3.2V 280Ah) Product Specification (Version E)-2019.7.5

Most recent Spec Sheet for the 280 LFP cells as provided directly by EVE March-14-2020.

diysolarforum.com

For a newer model:

Eve LF280K data sheet

This is the latest version of the Eve 280 amp hour cell. March 23, 2021

diysolarforum.com

Since everyone knows watt hours is the true capacity you should use to measure how a battery cell performs, it is interesting and confusing to me that battery manufacturers use amp hours. If the curve changes in the slightest, you can be short on amp hours, but have the same watt hours.

Attached is a grade B cell tested (one of the best, it was just the first datafile I opened). 277 amp hours, and 896 watt hours. I find it odd the cell manufacturers use amp hours rather than watt hours.

 

[Just John]

Anyway, I fear that some folks here are - perhaps inadvertently - giving credence to SFK's twisted argument about Wh. It's completely wrong, and the way to compare Ray's tests to SFK's test is with Ah.

I should also point out that every single grade A cell I own (32 total) measured above their rated amp hours (as well as watt hours). Using the same (or close enough) testing methodology as Ray.

 

[michael d]

To all following this thread,.
Speaking as one of "the Old Timers" who has contributed quite a bit here for everyone's benefit since this forum started.

I watched Andy from the start when he started 'Im sharing this learning experience ' shtick evolve into what it is now. He's a great talker/entertainer but that's the real limit. I and others "who Really know what's what" have replied with corrections,credible verifiable irrefutable FACTS to have it pushed off, ignored etc.

Wisdom is to realize when your faced with a polyester clad used car shlock dealer & RUN.

I CALLED HIM OUT HARD result was threats & repercussions even from here.

I Will Most Likely get smacked for THIS post as well.

Steve

i agree Andy is in it for entertainment and now to get the youtube revenue....i also got into it with andy on his mistakes where he had to admit it was done on purpose>>>supposedly so info tainment at its worse on some of the videos >>>>not at all a reliable source on some of the videos>>>

 

[Butcher]

At some point, being entertained while learning is probably the easiest way to take on all this information. I could not imagine reading a bunch of tech literature and having it mostly go over my head.

I don't blindly believe anyone and I research to find out what I believe is true. No matter what anyone thinks, this internet, YouTube, forums, etc is sure better than researching it in the library. Flaws and all, pressing buttons on this thing called a laptop is worth all the flaws I may get on my screen.

No one is perfect and if you do not like something or find someone is truly flawed, you really do not need to follow them. Something tells me that people do because they like finding flaws in others.

 

[Skypower]

What I like about Andy is that he always starts off with an optimistic first impression, wanting the product to be a success. By the end of the evaluation, and that may take an episode or four, he’s generally work out a valuable opinion that I trust. The good and bad can take time to be brought up to the surface. Would I buy a SunFun kit? No and not because of any YouTube pro or con evaluation. I just don’t like the build.

 

[turbo6bar]

At some point, being entertained while learning is probably the easiest way to take on all this information. I could not imagine reading a bunch of tech literature and having it mostly go over my head.

I don't blindly believe anyone and I research to find out what I believe is true. No matter what anyone thinks, this internet, YouTube, forums, etc is sure better than researching it in the library. Flaws and all, pressing buttons on this thing called a laptop is worth all the flaws I may get on my screen.

No one is perfect and if you do not like something or find someone is truly flawed, you really do not need to follow them. Something tells me that people do because they like finding flaws in others.

So how do you research to find out what you believe it true? If we cannot trust YouTubers, then why listen to them?

 

[turbo6bar]

It really is the wild west in DIY solar industry if you're not going with off-the-shelf goods, and once-trustworthy companies like SFK make things even tougher.

So how do we know server rack batteries use Grade A cells? Is that battery segment trustworthy?

 

[wattmatters]

So how do you research to find out what you believe it true?

Just like any profession or complex task it takes years of training to learn how to read and interpret research, and to be able to understand what is and is not valid on the basis of the data presented and the methodologies used. This is a skill requiring a career-like focus, including relevant review and feedback from reliable sources and is built up over a lifetime.

If we cannot trust YouTubers, then why listen to them?

If you start out with the understanding that YouTube is merely another form of entertainment designed to promote what is popular, not what is correct/right, then you'll be better placed.

YouTube is entertainment first and foremost. Anything useful one might glean is a bonus but the signal to noise ratio is very low.

Occasionally entertainment media does occasionally provide useful or helpful information, but as a source of reliable data on matters which really require detailed analysis and sufficient expertise to understand, in general it's no better than cable news or newspapers or other mass media.

The skill of dedicated researchers, scientists and engineers is way under valued.