been awhile, checkin in

[bob g]

and decided to check back in.

been working on other offgrid components mainly because i have no place currently to do a windgenerator.

in the process of developing a couple of micro co and trigenerators, that are about to the assembly stage.

we have been testing both the outback mx60 and the morningstar ts60

and have come up with some issues with the outback.

what we find in testing is well below what is shown on the screen of the mx60 which

ends up giving an efficiency of around 83% instead of the indicated 95% efficiency.

so i am looking to see who else might be running one of these so i can compare some output amperage numbers.

if there is anyone here that has an outback mx60 running, and has an amp meter, i would dearly love to see if you would mind checking the output current of your mx60 with an external amp meter and let me know how it compares with what the screen says.

my system needs over 240 amps of charge controllers, so i would need 4 of the mx60's and at around 600 bucks each retail, you can see why i am going to want to verify not only the companies claims, but the products screen reports.

there is a huge difference in 83% efficiency and the near 100% efficiency that is calculated and reported on the screen.

should others test confirm the mx60 being defficient, i will be looking to build my own pwm controller, and yes i realize this is a large project that won't be cheap

but ,,, four mx60's ain't cheap either.

keep up the good work fella's,, looks like some very interesting things have been going on here.

bob g

[boB]

Hi bob, boB here...

I'm wondering what's up with yhour MX60.  You didn't post your input/output voltages

and currents (real currents), which is very important.  Is it that the OUTPUT Ammeter of this particular MX60 is wrong, and are you using some external monitoring ?

The MX60 will have a lower efficiency at low output power/voltage/current.

83% is very low for medium to high power outputs, even 12V systems.

boB

K7IQ

[Volvo farmer]

Hmmm, I've been using an MX60 for about a year now, and never noticed much of a difference between the number on the screen and the number on my tri-metric. Are you using it with solar panels? I do not know what a micro co or a trigenerator is.

Outback has a user forum on their website with some pretty experienced installers and users. I've been browsing it for some time and have never heard of your complaint before. Maybe post a message over there and see what those folks say.

Street price on an MX60 is as low as $460 now. Don't pay list, you can get them much cheaper.

 

[bob g]

no i didnt post all the test results, basically just to reduce the word count

but here they are

input voltage       mx60 indicated     meter one       meter two

.                          60.0               60.0            60.0

input current            3.9                 3.9             3.9

output voltage        13.2                13.2           13.2

output amperage     * 6.9 *                 5.7            5.7

as you can see the two external test meters agree with outbacks screen on input and output voltage and input current,, but disagree significantly on output current.

when we called outback we were told they compute the output current and do not actually measure it!  so... how do you get accurate efficiency computations if you compute one of the variables and it is so far off of reality?

this is why i would like to see someone else check their output current externally and compare it with the screen indicated current.

volvo farmer:

yes i am aware that they can be had for about 450, but even at that level

i want to see better efficiencies (actual) not calculated based on some fuzzy math.

yes these are being tested on a solar array, we tested them with various panels of various wattage input and from 30 volts input to 80 volts input,, and got very near the same results in efficiency with actual readings. and coincidentally the screen still computed mid to high 90 efficiency, which is apparently a flawed result.

thank you both

anyone got one they can test the output on?

bob g

[DamonHD]

Is it at all possible that the pulsed output current that the MX60 will be producing is causing the external meters to misread?  (It would be less likely to cause the same misreading in different brands of meter, I think.)

Rgds

Damon

[DanG]

MX60 through TM500 into AGMs shows no difference over many weeks time...

The TM500 logs in/out amperage differences; Could losses of the battery be showing?

[boB]

I see most of your problem, bob.  One reason the DC to DC conversion efficiency is

low is because you are using a higher input voltage.  It may be lower by just

1 or 2 percent because of that BUT the BIGGIE is that you are outputting such

a LOW output power that the power losses are a BIG percentage of the output power.

For instance, the MX (and any controller) takes some power just to operate

the relay and the DC-DC converter. Also, the higher the voltage at the input

terminals... the higher the "idle" or "tare" losses are.  Now, if you measure

your output power vs. the input power, it can be extremely low. Say, you

were putting out ONE (1) amp to the battery... The efficiency will be

extremely low.  I'd say 85% is pretty good in your case.  If it were a 24V

and even better yet, a 48 V battery system, and the SAME output current,

you would have twice or 4 times the output power you have now, and those

idle losses would be less of a portion of the total output power and the measured

efficiency would come up.

You notice how manufactures never seem to publish efficiency at low output

powers ?  Especially inverters.  You will notice the efficiency curve dropping

at a very steep slope at the left hand side (lower power side) of the power

vs. efficiency graph.

And SOMEBODY has the wrong information on the MX60 meter !  The MX measures

the OUTPUT, NOT the input current.  It's the INPUT current that is calculated,

so the output current should read closer. Maybe it got mis-adjusted somehow ??

The current is averaged in hardware and software so shouldn't make a lot of difference if there is output current ripple or smooth DC current.

Most inverters will cause 120 Hz current ripple on the DC line at higher output powers.

Hope this helps shed some light.

boB

[(unknown)]

Hi Bob

Sorry but I didn't understand your efficiency readings.

When calculating the Energy efficiency i get

MX60 result 13,2*6,9/(60*3,9)= only 38,92%

Meter result 13,2*5,7/(60*3,9)= only 32,15%

Do I totally misunderstand something here?

Where comes your 83% from?

I have been working a lot with the designing of switched DC/DC converters.

and the result you are describing is a Waste.

To be honest I have newer seen any switching application that gives as high real world efficiency as

stated 98% by the MX60, but then again the MX60 is probably not switching then.

Reading the "MX60_a.pdf" it tells that the

Power Conversion Efficiency Typical

98% at 60amps with a 48V battery and a nominal 48V Solar array.

(Probably working linear at the time displaying the internal loss in RDSon.)

This really tells U nothing of the product.

A coversion table would be nice though.

/

[bob g]

thanks for your comments Bob

however the info about the output amps being calculated and the input amps being actually measured was from outbacks technical support.

they told us the unit measures input voltage and amperage

and also the output voltage

but the output amperage is calculated and not actually measured.

bob g

[bob g]

Swede:

those number i posted were only one shot, where we were trying to figure out

why there was a difference in output amps indicated and what was measured.

i did not mean to infer that it was at 83% efficient at that test point,

we only saw it get up to 83% efficient at the highest point as measured with two other meters, which agree'd with the measured amperage.

i am not real thrilled either with the published spec's on this product, it boarders on ... well ,,, you know!

bob g

[boB]

>>... the info about the output amps being calculated and the input amps being actually measured was from outbacks technical support.

bob, can you check something for me ??  Remove the wiring compartment

cover to you MX60 and look to see if you find 4 loops of wire looking thingies

behind the terminal block.  Look or measure with an Ohm-meter to see if they

connect directly to the battery output terminal or to the PV input terminal.

These loops would be the current measuring shunts.

Maybe OB changed it in the last few months ??  The first 20,000 or so MX60s were connected to the battery terminal.

Thanks,

boB

[TomW]

Gee, guys, not to go off topic here but we seem to have a lot of gentlemen named "Bob" in this thread. Not that it is a bad thing, just confusing a bit.

Sorry to drift off topic.

Cheers.

TomW

[bob g]

about 20 years ago i worked for a good size truck dealership in seattle as the day

shift foreman,,

my favorite was

"bob!,,, line one"

we had 7 or 8 bobs working there,, and you could hear all of use screaming back,,

two of us at the front counter, 2 or 3 in the parts dept, and another 2 or so in sales all bellowing...

"WHICH ONE!"

LOL

bob g

also known in the old forum days a R Gayle

[bob g]

Bob:

i will check for you

there are 4 loops or half loops as you say near the terminal posts or rather just above it, i didn't however look to see what they did, but that make sense.

however

today my partner while testing again on a 24 volt battery bank, disconnect the battery output and the screen still read .5 amp output,

my parnter called to ask how this was happening,,, i told him not to stand between the mx60 and the battery bank,, he might get zapped.... lmao

i had him for about a second or two...

we both had a good laugh

late last night i went to the outback forum and found that those that install these things, don't pay much attention to the screen except for programming, they use their own test meters to establish what is actually happening.

evidentally those that install these things know that the reading reported  are a bit .. how should i say?  off?

also after doing much research on buck converters, it takes a very well engineered and specifically applied buck converter to get to 95% efficiency, so the reported 98% is likely something that is never going to be reality in the real world for any appreciable amount of time. which is ok by me i guess.

it would appear to me after doing some tests that perhaps one could see about 93% with the system (peak)if one was to input maybe 90 to 120 volts dc into a 48 volt battery bank, but even still i would expect the average to be around 90% in real world applications.

according to our tests ~ 85 to 88% for a 24 volt system being fed around 50 volts

and around 83% for a 12 volt system fed by 20 volts or so.

as opposed to the morningstar pwm controller fed with 17 volt panels into a 12 volt bank its efficiency hovers at 97 to 98 percent (actual), but it does not have a buck converter.

so if one is looking for the max efficiency it would appear that the morningstar has an advantage if, and only if the panels can be matched nominally to the batteries and are close enough to limit line losses.

at least this is what seems to be the reality so far

bob g

[boB]

First, I ~try~ to avoid confusion between all the Bob's and myself by spelling

my name backwards.   boB   as opposed to Bob.  Now, you're name appears to

be spelled bob, which is even different.  We still have room for a bOb here

too, which is sort of spelled inside-out.

You are right that you won't get 98% efficiency with a 12 Volt battery system.

that 98% number for the MX60 was measured at 3000 Watts output on a 48 Volt

battery and a 48 volt PV input (about 64 volts input).  It can actually be

better than that.  Now, one thing you cannot do with a typical PWM controller

is to connect a 48 volt PV array to charge a 12V or 24 volt battery.  Or,

a 60v or 72 volt array to charge a 48 volt battery.  There are pretty much

2 basic advantages to doing this.  1 is when there is a long PV wire connection

to the controller, say, 75 feet or more.  2 is when there is a partially

shaded array when the max power point voltage can be below the battery voltage.

Another is when the panels are hot and the MPP voltage is at or below the

battery voltage.  It's better to wire it for a higher voltage usually.

Not always the highest voltage, but one or 2 nominal voltages higher.

So, bob, how many Watts of PV do you have hooked up ??  The use of an MPPT

controller might be questionable with say, 250 Watts of PV or less.

On the 0.5 Amps out when the battery was disconnected...   What that is, is

an offset in the current sense circuit because it got warm.  It would come

back down to around 0 after a while I think.

This is one reason why the MX "opens up" once in a while to reset that offset.

The newer units should be better than the real old ones, like over serial number

6000 or so as I seem to remember.

boB

[Seth7]

Your not the only one gone for some time and stopping by ...

My MX60 is still working (the replacement one) ....

its been a couple years now...

Iv ahd to replace the berrings in my solar tracker one more time since i last stoped by... and i figure it will probably freeze up this winter... hope im wrong.. but even so .. its easy to replace....

[Seth7]

used to ahve the user name MikeD ...

[Nando]

Now that everyone on this earth has giving an opinion.

The MX60 and all converters have high efficiency when the input voltage is close to the output voltage.

98 % efficiency means that the converter is having a high duty cycle, like 96 + % which allows the power MosFets to be most of the time ON, looking , ALMOST, like a charger controller like the C60, which is a DC switch with a very low ( around 200 Hz) modulation frequency that starts to switch when the battery voltage is reaching the controller limits.

The use of a converter with high input voltage to bring down to low voltage, is an erroneous decision.

One should and ought to do a design consideration of the conversion to attain high conversion efficiencies and these efficiencies will run around 83 to 92 %.

To attain high efficiencies when converting from a high voltage to a low voltage, like in this case, the converter should have a transformer conversion to increase the efficiency.

Since you need a high current( 240 amps) then what I suggest is a full bridge feeding a synchronous dual current rectifier.

Go to www.ti.com and down load the UCC3895 device and the : slua107.pdf; slua121.pdf; slua275.pdf; slua287.pdf; slua323.pdf; slua189.pdf -- that may teach you what the best procedure to follow for this project.

You are looking for a charger system that is around 3.5 KW, a major project, INDEED,that unless you are quite familiar with high power design procedures, my suggestion is to look for other alternative solutions, like several in parallel with sequential ON-OFF sections for higher efficiencies ( a multi phase system with ON-OFF capabilities ) and with MPPT control to maximize the charging efficiency.

Do not trust the currrent display of these converter, they are relative and many times not very accurate since the do not need accurate calibration for external display, but relative current levels for internal limiting conditions.

If tests aree neded, then proper current meters are needed, for accurate determination of the needed parameters.

In this case the design should have a push-pull or a full bridge feeding a transformer with efficient rectifiers this way one may obtain around 89 to 94 % conversion efficiency.

LASTLY: since you have such high KW conversion to a low voltage, one should examine the system and see how to improve it overall, for one, a much higher BATTERY voltage is suggested being 48 volts which that may give you and additional 5 to 8 % higher efficiency overall in usage up DC/AC conversion.

Then a more reasonable charge controller can be used which in this case a single MX60 may do the job -- or one a bit bigger like what Midnite Solar may be putting in to the market soon.

Nando

[Seth7]

And again .... Im MikeD AKA Seth7 .... stopping by to say hello !!!!

I see the Board has changed again !!!!