Deceptive Marketing With Goal Zero Yetti 1250

SolarPowered
SolarPowered Solar Expert Posts: 626 ✭✭✭
in Solar Product Reviews & Opinions #1
Alright so I don't know if anyone has used the Goal Zero product line, but I am under the impression that this company is on the "hard selling" of a over rated product with false performance results, and deceptive marketing ploys.

So I haven't purchased the yetti myself, since I can build units myself, however I've had a few people in my line of work purchase the device. Some tests were ran and none of us to say the least were happy or impressed with the end result.

Here are the list of concerns. Which I believe mostly leads to false market advertising.

-Goal zero claims the yetti 1250 produces 1250watt hour of power. This is some what true, some what false. The battery AH rated at 100AH delivers 1250 watt DC power, after DC to AC conversion its only 1125watt hour of " possible"delivered power. That is de-rated further as the inverter wont operate below 11 volts and at 10% depth of discharge meaning nearing 0% that would mean voltage is close to 10.8volts discharge from the battery, which now brings the watt hour closer to 1012.5 watt hour, (I guess we will just say 1000 watt hour is what this system can perform and actually produce to a full depth of discharge).
-Second concern is that its a lead acid AGM battery. How low do consumers think they can drain this battery's DOD before it performs much lower than 1125 watts? @ 80% full charge after a full drain cycle that would mean the voltage is discharged at 12.35~12.4volts, rather than 13.9volts @ 100% full charge.

Is it just me or is this deceptive marketing to consumers thinking that they can fully utilize 1250watts? When I calculate the average usage and maintain battery cycle life the unit should only be performing to 680watt hours not 1250watts. For longevity of this system I would suggest not using more than 400watts, in order to get full use of the battery and its life cycles.

From my professional experience the math doesn't add up per watt, or for the reliability of this system. If under full DOD's the generator life span I am calculating is roughly 6.5 months at an average of using 680watts per charged cycle. I'm also concerned with the life of the inverters which run hot having to maintain a higher amper VS less voltage discharge to the bussing terminals and what effects that may pose to the internal capacitors, and internal circuitry of the inverter. What is that unknown life expectancy?

I've been considering testing hummless goal zero's competitor for performance, as I see some issues with this portable unit as well. Such as small AH capacity of 55AH but its a LiPo4, and no where does the company mention whether or not their inverter is pure sin wave.

Suggestions comments would be nice. I would like to know what products there are to test that may offer a good bang for the buck for consumers.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    Which is why we always suggest the people do a paper design based on rules of thumbs for a starting point.

    To say that a system is deceptively marketed is easy--Because almost nobody will run a system at its marketing numbers anyway--whether they are real or not.

    I don't know the details, but if it is an AGM battery, it is possible to discharge them at C/1 hour rate or even C*4 hour rate (discharge dead in 15 minutes). It makes for some very "impressive" power numbers in a small/"inexpensive" box. But then you start figuring out what you would do with 1 hour of 1,200 watts (or 1,100 watt, etc.)...

    Almost everyone wants to run their refrigerator in an outage. Which is around 130 watts at 50% duty cycle. That would run on such a system for ~10 to 20 hours and then the battery would be near dead (and such operation would probably kill the long term life of the battery). And then, at the end of the usage, you still need to recharge it with what? A generator, a 1,000 watt solar array?

    In any case, backing to rules of thumbs... We start with a design of 2 days of battery storage with 50% maximum discharge (or ~4 days of storage in an emergency if a dead battery bank is OK at the end--For emergency usage, such as a telephone central office, that is a typical specification, hardware is expected to operate to death in emergencies--i.e., backup genset fails/runs of out of fuel). That is a battery bank that is 4x the daily load. Or 4-8x larger than the Goal Zero unit just to run a refrigerator.

    Add on some sort of charging source--around 5% to 13% or so for solar, 5% to 25% or so for generator/AC power. Need to get at least a minimum 5% rate of charge to most batteries for proper/quick recharging (setting below ~75% State of Charge for weeks/months will kill a battery bank in a year +/-). So a 10% rate of charge on a 800 AH 12 volt battery bank would be ~80 amps or a ~1,500 watt solar array (or backup AC battery charger). That would run a ~2,000 WH (2 kWH) per day (based on battery bank, or ~3,000 WH per day based on 4 hours of sun per day--about 9 months of the year minimum for much of North America), or a refrigerator plus a few lights--Reliably, for years.

    A 3.3 kWH per day (100 kWH per month) is probably a good aim point for a very efficient off grid home with a nice/modern electrical life (fridge, lights, washing machine, well pump, laptop computer/radio/TV). Not a lot of power to waste--But a comfortable life.

    All of a sudden, a "generic" reliable/off grid power system starts looking quite large and not cheap. And nothing like the marketing numbers for many units out there.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    #3
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    My big problem is the misconception goal zero yetti is better than a gasoline generator because its zero emission. At the rate people use excessive loads on gasoline generators compared to the light duty loads of battery generator is moot in argument.

    The battery powered goal zero yetti doesn't suffice for even 1/12 (120%) of the high loads that gasoline generators demand. Even on a scale of bio diesel generation goal zero yetti is 1/18 (180%) away of that load demand.
    So in the large spectrum of energy generation it doesn't even offset environmental impact by .00001%. All it does is clog our landfills with chemical contamination, because its a horrible use in delivering power via battery with the short life expectancy for "high load" demand applications. Sure you can recycle batteries, but not everyone recycles. In this case gasoline and bio-diesel applications are still better for the environment. At the battery's cycle life of replacement, it would still be cheaper to source fuel based on the load demand.

    The only technology at the moment that has an equal price match to equivalent of fuel delivered energy and its demand is the use of lithium phosphate which would deliver thousands more charge cycles with no memory effect VS AGM which would be considered to have only a few 100 charge cycles and diminishing returns per charge cycle.

    Take into account goal zero builds and manufacturers these units in china they could essentially sell them for much less than what they are going for at the moment.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    The two things which are specifically misleading about this are:

    1). 100 Amp hours of 12.5 Volts equaling 1250 Watt hours. That assumes two things which are totally wrong; that the battery Voltage remains at 12.5 Volts throughout discharge and that the battery can be taken down to 100% discharged. In reality this battery would only supply about 600 Watt hours DC. That is also not the same as its AC capacity because of the inverter consumption and efficiency conversion loss.

    2). That you would be able to discharge the battery 100% without the inverter shutting down due to low Voltage and that if you could the battery would recharge again. That is the "ideal" battery which does not exist.

    This sort of thing leads to frustrated, disappointed consumers who then stop believing any info given them because they suspect it all to be lies. Once bitten, twice shy.
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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    #5
    Re: Deceptive Marketing With Goal Zero Yetti 1250
    Cariboocoot wrote: »
    The two things which are specifically misleading about this are:

    1). 100 Amp hours of 12.5 Volts equaling 1250 Watt hours. That assumes two things which are totally wrong; that the battery Voltage remains at 12.5 Volts throughout discharge and that the battery can be taken down to 100% discharged. In reality this battery would only supply about 600 Watt hours DC. That is also not the same as its AC capacity because of the inverter consumption and efficiency conversion loss.

    2). That you would be able to discharge the battery 100% without the inverter shutting down due to low Voltage and that if you could the battery would recharge again. That is the "ideal" battery which does not exist.

    This sort of thing leads to frustrated, disappointed consumers who then stop believing any info given them because they suspect it all to be lies. Once bitten, twice shy.

    I believe Goal Zero tried to calculate the operating range of the inverter which the math for that would be (13.95V X100Ah)+(11V X100Ah)/2= 1250 watt hours, which is still wrong because after the first charge cycle that higher voltage number becomes diminishing in return, and no where reflects an hourly operational figure along with temperature factors.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    bill is right on the agms, but that applies to concorde agms as most other agms cannot have that high of a charge/discharge rate.

    if they used a 100ah battery with any claims of using all of that power that would be deceptive in my book as normal operations cannot use huge amounts of power for long being the voltage will drop and the ah capacity will also be in a different perspective due to the peukert effect lowering the effective watt hours due to a higher discharge rate. a 100ah battery is normally based at about a 20hr rate. what that means is 5a drawn for 20hrs and it would be at 0% soc. this does not mean that you can draw 50a for 2 hrs as that isn't happening. you would hit 0% soc long before that 2hrs is reached if the voltage drop from the peukert effect does not kick off the inverter due to too low of voltage which would effectively shorten the useable time even further.
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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    #7
    Re: Deceptive Marketing With Goal Zero Yetti 1250
    niel wrote: »
    bill is right on the agms, but that applies to concorde agms as most other agms cannot have that high of a charge/discharge rate.

    if they used a 100ah battery with any claims of using all of that power that would be deceptive in my book as normal operations cannot use huge amounts of power for long being the voltage will drop and the ah capacity will also be in a different perspective due to the peukert effect lowering the effective watt hours due to a higher discharge rate. a 100ah battery is normally based at about a 20hr rate. what that means is 5a drawn for 20hrs and it would be at 0% soc. this does not mean that you can draw 50a for 2 hrs as that isn't happening. you would hit 0% soc long before that 2hrs is reached if the voltage drop from the peukert effect does not kick off the inverter due to too low of voltage which would effectively shorten the useable time even further.

    I believe when you say peukert effect, I believe you are stating ampacity discharge rate @1 hour rate. Correct? Peukert calculation It=(C/IH)k-1 does not have any relative information to temperature variation among AGMS to that discharge either which significantly impacts (I) discharge relative to 1 ampere, as the discharge or demand becomes greater within that rate temperature elevates and amperes tend to bleed off or be lost in that chemical reaction is my understanding. (IF) the demand of discharge is requiring its full potential then the battery temperature exponentially rises to a point to where capacity for discharge is lost. I would assume a demand of 1250 watts (in 1 hour) would elevate the temprature of an AGM battery close to 115*F which would mean 45% of that discharge capacity would essentially be lost or what I came out with an average yield of 680 watts of production use per cycle.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    Peukart effect is the power curve of the battery. It applies to all rates of discharge and charge. Technically it is affected by temperature, but that's not particularly relevant as the company's power claims seem to ignore it completely.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #9
    Re: Deceptive Marketing With Goal Zero Yetti 1250
    Cariboocoot wrote: »
    Peukart effect is the power curve of the battery. It applies to all rates of discharge and charge. Technically it is affected by temperature, but that's not particularly relevant as the company's power claims seem to ignore it completely.
    And to apply the equation properly you need to start off with the number for the battery's 20 hour rate capacity, C20.
    SMA SB 3000, old BP panels.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    it does not refer to the 1hr rating of a battery and as coot said it is a curve. it basically holds that below the 20hr rating time that you will not get as many ahs overall and if you go longer than the 20hr time that you will gain more in overall ahs. it does however show what the current draw is if you divide the ah rating by the time factor. the base is 20hrs, but some batteries are rated at 24hrs and some are at 10hrs or even 8hrs. look over this from concorde as it shows the ah rating of the batteries changing with the different times drawn upon them. to gain the extra ah the current draw upon the battery must be lower.
    http://www.solar-electric.com/cosuagmba.html

    what they show is the total until the death of the battery or 0% soc. take the first battery you see in the list for example, pvx340t.
    at 2hrs draw it shows a capacity of 27ah. this means the battery can deliver 27/2=13.5a for 2hrs to bring it to 0% soc.
    at 24hrs (it is concorde's standard rate for their batteries) it shows 24hrs for the draw and an ah rating of 34ah. this means the same battery can deliver 34/24=1.4167a for 24hrs before reaching 0% soc. anybody can figure out the watt hours delivered by the same battery increased with the lower draw for a longer period of time by multiplying the volts x the amp hours. the decrease in wh does not reflect that the voltage drops lower than you think and could actually not be high enough to run some things that require a minimum voltage such as inverters.

    for reference the 13% max charge rate we often cite is a bit over the c/8 rate (8hr rate) which is more accurately depicted as 12.5%. also for reference the 5% minimum charge rate we often refer to is the c/20 rate (20hr rate).

    i hope this clears it up for you.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #11
    Re: Deceptive Marketing With Goal Zero Yetti 1250
    SolarPowered wrote: »
    Is it just me or is this deceptive marketing to consumers thinking that they can fully utilize 1250watts? When I calculate the average usage and maintain battery cycle life the unit should only be performing to 680watt hours not 1250watts. For longevity of this system I would suggest not using more than 400watts, in order to get full use of the battery and its life cycles.

    To us, it might be deceptive. For the guy that wants to just turn on the blender a few times at a party maybe not. Most consumers are going to murder the battery anyway regardless of how in/accurate the power rating is. The Tech support responses in their review section go into more detail about taking it easy with lower current draw devices.

    For those who just don't know, at least it contains an MPPT charge controller, pure-sine-wave inverter, internal AC charger, metering, Anderson Powerpole connectors - at least they are trying. The #31 size 100ah agm battery is user-replaceable at least. I'd imagine it is a general purpose ups-style agm. There are some handy hints for consumers that want to take good care of the thing by monitoring the metering.

    I'm not saying this is the best bargain in the world nor the best quality. But mom-n-pop can handle it safely.
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  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    #12
    Re: Deceptive Marketing With Goal Zero Yetti 1250
    PNjunction wrote: »
    The Tech support responses in their review section go into more detail about taking it easy with lower current draw devices.


    Why couple the package with a 1100watt inverter? Why not design it for something milder like a 500watt? Atleast it would prevent the significant rapid drain and death of the battery.
    Just doesn't make sense a powerful inverter and not enough capacity to supply for it.
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  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    #13
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    I agree totally, but I think that it is mainly for short spike current demands. Users will find out quick enough what "continuous" really means. :)

    Thing is, the target market for this thing is not likely to pick up a Kill-A-Watt meter and figure out their power load beforehand. Nor will they calculate their solar-insolation and then find out what only having 60w of panels means when they are 80% DOD. They are just going to throw devices at it and hope that it works.

    One thing not mentioned is that the battery is due for replacement in 4-5 years even if treated well. This is something GZ should mention as I imagine some will park this thing in the garage on float for 10 years, and then wonder why it doesn't have the capacity when they need it. To their credit, the specs mention that the battery only has a few hundred cycles in it, so I imagine that they envision people taking this thing down to 50% DOD or more pretty regularly by either accident or design.

    GZ is approachable, and tech support has answered a few of my questions for some smaller devices that I wasn't happy with from a QC standpoint. Maybe send them an email and see what they say about why they chose a 1200watt inverter spec. A long time ago, I sent in some suggestions for AGM maintenance on one of their earlier products, and they incorporated some of it in the docs. I could have sent in a 5 page long power-load calculation manifesto, or go the KISS route in hopes that the average buyer who isn't going to read a manual, might adopt some very simple tips.
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  • DarkStar
    DarkStar Registered Users Posts: 12 ✭✭
    #14
    Re: Deceptive Marketing With Goal Zero Yetti 1250

    The whole time I thought Goal Zero called it the Yetti 1250 because it used a 1250 watt inverter (that's how most companies tend to label these products). Checking the specifications though, it is only a 1200 watt inverter and they rate the battery at 1250 watt-hours.

    Yes, calling a 12.5 volt, 100 amp battery a 1250 watt-hour power source is an inaccurate statement, but since most of these Power Packs usually have other substandard equipment, the battery alone is the least of my concerns. I would be looking at the inverter capabilities and battery charger circuitry before looking at the battery.
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