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 [ Parent ]
Sorry to drift off topic.
Cheers.
TomW
"Education consists mainly of what we have unlearned."--Mark Twain[ Parent ]
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 :)[ Parent ]
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[ Parent ]
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 [ Parent ]
