BZ MPPT 500 Solar Charge Controller

[Tom in NH]

I just got one of these units and am quite impressed with the way it packs current into my batteries. But the front panel voltage/current display seems to be wacko. The numbers jump all over and I can't get a stable reading of anything. Still, the controller seems to be working in all other respects. Has anyone else tried one of these solar charge controllers? I'd like to find out what the display is "supposed" to look like. I wrote the manufacturer, but did not get an immediate reply. So I thought I'd write to the Otherpower panel of experts. --tom

[Dreadstar]

I have a new outback mx60 which is basically the same thing. It does the same thing. Watts bounce around but that is normal with haze/junk in the air affecting the amount of impact on the panels. it also recals itself every 3 minutes for optimum output. I did however get an increase of 50% over the course of a day into the batts. went from 50ah to 75ah from a 220watt array. not to shabby. Me likes MPPT .

Not cheap but well worth the $500 imho.

Now just need to find out where i have to move to once they eminent domain me.

So i can see if i can put my panels back up and if so. Make it bigger. More RE less to edison. works for me.

[ghurd]

I have no experience with the recent more advanced BZ products, but their previous products did not exactally impress me.

They seemed a little more idiot proof than some other products, but they lacked any percision at all.  Maybe designed and geared more for a consumer than someone who actually understands what it is supposed to be doing.  I recall one in particular where all kinds of pecular, totally unpredicatble, things happened with relatively slight temperature changes (10'F?).  And it wasn't temperature compensation!

Maybe the display is correct, and something else is goofy? That'd be my first guess.

I'd send it back to the retailer for replacement. Quick.

G-

[pyrocasto]

http://www.discountpv.com/chargecontrollers/

I was thinking of getting one from here. IMO it will be worth it with the extra power, and less loss as I will probably go like 60-80 volts with it.

I just wish they had a dump load setting as well, but I guess I can wire that up later somehow. I like to squeeze out every watt I can.

[halfcrazy]

i know on the solar boost 50 amp controllers the cable would be bad or just have to wiggle the conection and the display would calm down we would see real far off numbers and they would jump all around

[henjulfox]

Got one last week. Went to hook it up this last weekend. On attaching the battery cables got the magic puff of smoke and nothing from the display. Checked the obvious and no, I didn't wire it backwards. Contacted the seller who suggested contacting the manufacturer. Sent them an E-mail yesterday, no reply yet.

I look forward to testing the output against a C-40 and testing the claim that it's cheaper to buy a MPPT than another panel or two.

-Henry

[Nando]

Tom in NH:

You got it right.

MPPT will shows a wild dance since it goes around looking for every bit of watts that are available in the Dancing wind or Flickering Solar energy shadowed by the white clouds covering the big red solar disk.

Some MPPT circuits go every few minutes to look for the peak power and some have a bit better set up and vary the circuit more often, like many times a second -- this is the type I prefer and the type I have designed in my charge controllers -- they are not microprocessor manipulated but low frequency varied following the power curve of the power source.

For Solar Panels,if one have a good solar tracker and a MPPT charge controller there is a power harvesting gain of about 30 to 40 % with both arrangements depending on the latitude of the site.

Regards

Nando

[geoffd]

Nando,  did you design your own MPPT Charge Controller, if so any chance of emailing me the design.  I am currently using a hand built 24 volt version of Forrest G Cook's SCC3.  It works well, due to lack of money I only have 300 watts of panels instead of 600 watts, so any little improvement I can make will help!

Cheers

geoff at professionalhosts dot com

[pyrocasto]

Wow that is really not encouraging. O_O I may still try one, but maybe I'll wait and see if there is good service with the manufacturer.

[Tom in NH]

I was thinking along the same lines, Chris. I wired up four panels in series for 48v, which actually measures OC 66v. That helps me because I moved my batteries inside away from the winter cold, but it's a 130 foot run. I don't know if a dump load is even possible with MPPT, but it is nice to contemplate. --tom

[Tom in NH]

Hi Nando. I can imagine the wild dance as you put it, but the display has a battery voltage indicator that jumps around like crazy. At the same time, my inverter is also displaying the battery voltage and it is like the rock of Gibraltar, by comparison.

I do feel kind of foolish though. This morning I discovered a blown fuse on the PV input line. I took out a section of panel and replaced the fuse. The numbers still jump around, but they look more believeable now.

Actually it's kinda cool to think my PVs actually blew a fuse! I never used to get much more than 420 watts out of them when they were hooked up to my C40. Now I blew a 10 amp fuse at 50 volts. That's more than 80 watts greater. Impressive!

It looks like I'm going to need a second one to handle the extra current though. --tom

[aogden]

Has anyone sucessfully applied a MPPT charge controller to a small wind turbine? If so I would like to hear about it. I don't know if it would even be feasable as the wind is so dynamic.

[Flux]

I haven't tried a constantly tracking scheme, that is a job for the young digital wizards, but I have used buck converters with an analog tracking circuit to alter the alternator characteristics to keep the prop at optimum tsr.

It does not sort itself out, but once set up does the same thing. I am doubtful if you can constantly track the wind. You may be able to slowly learn the characteristics like an engine management system and once stored you have the same results as the analog control.

Here is a set of results from an experimental 6ft machine.

The low curve is with the alternator connected direct ( badly stalled). The middle is is with the usual resistance matching to keep the prop out of stall. The top curve is with the tracker and no series resistance.

Flux

[henjulfox]

Heard from the manufacturer. Short note saying to send them the controller. Seems to imply they will repair/replace with a minimum of hassle. I'm hopeful.

-Henry

[Nando]

The battery voltage may be shown as steady value ( very low voltage variation ~~~ around 50 to 100 millivolts ~~ depending on the internal impedance of the whole battery bank ~~ ), but the MPPT circuit does vary the output voltage of the controller to vary the charging current depending on the power source power availability.

The equivalent is the matching of load impedance to the variable power source impedance.

You may see the input voltage vary wildly which reflects as a variable output current -- that is done by varying the controller output voltage.

Ideally the input voltage should be several volts higher than the battery voltage for easier MPPT work.

For wind mills, the voltage at peak upper power the voltage should be 2 to 4 times the battery voltage, this way, when the wind is low, producing low power, the MPPT control may be able to supply low charging power where others mills without MPPT may not be close to supply charging current.

Same things goes for small hydro systems.

Regards

Nando

[Nando]

I will send to you an article that has the MPPT circuit feeding a 2 amps charger.

Notice: that even though it is a 2 amps, the MPPT section can be separated and used with mostly any PWM charge controller.

If you have problems, send the schematic you are talking about, I do not have it, to indicate you what to do and where to 'GRAFT' the MPPT circuit if such controller accepts the "graft".

Regards

Nando

[Nando]

I do not know your name, which is ?

I tried to send the schematic and did bounce as not existing.

Permanent Failure: 550-"The_recipient_cannot_be_verified.__Please_check_all_recipients_of_this

Delivery last attempted at Thu,  6 Oct 2005 18:02:48 -0000

Nando

nando37-at-comocast-dot-net

[geoffd]

Sorry Nando that should be geoffd not geoff.  That's what I get for reading this late at night  

I tried to send you a message but got:

A message that you sent could not be delivered to one or more of its

recipients. This is a permanent error. The following address(es) failed:

 xxxxx37@comocast.net

   unrouteable mail domain "comocast.net"

Strange?

Geoff

[Tom in NH]

Hey, Nando. That spliced-in MPPT sounds pretty cool. Could I get a copy of the article too?. Contact me off line if you wish, woodsnh at isp dot com.

I finally broke down and called BZ. I shoulda done that first. They were just so good at troubleshooting it. We clipped a capacitor that eliminated some noise that was causing the flaky readings. Now the display is stabalized and the unit works like a champ. I feel so positively rich with extra electrons I think I'm going to run a new line to my refrigertator and see if I can run that off of solar. Maybe a couple new livingroom lights too. --tom

[pyrocasto]

Something I didnt think about, is they say they must have a minimum of 68 watts for the 250 version, and minimum of 100 watts for the 500 version. Do you really have to have 100 watts before it will charge your batteries? Doesnt that seem kind of rediculas?

I may have the wrong mindset, so someone help set me right.

[henjulfox]

Follow-up. BZ sent me a new controller, no question asked. Will fire it up this weekend.

[pyrocasto]

Cool. Let us know how it works out. ;-)

[(unknown)]

I am presently installing my second BZ mppt 500 controller.  The first one

had the fluctuating voltage readout as you described then after several weeks the entire display went blank.  BZ sent a new front panel but the unit died before I had a chance to install the new front panel.  The second unit displaya 17.7 volts (fairly solid, not jumping around but this could be because of the low input power) when there is actually 12.7 volts at the batteries which are 8 ft. away connected with 4 awg. finely stranded welders wire.  There was heavy overcast so I was only getting 1.5 amps from my panels.  The meter also read 1.5 amps output to the batteries.  I am guessing that the "boosting" does not kick in until there are 100 watts present at the input. Comments?  The previous mppt 500 also indicated much higher voltage on the display vs. actual voltage at the batteries.  It almost seems that the controller is "boosting" the voltage before being displayed  I am also wondering that if when then input power reaches 100 watts and the amperage "boosting" kicks in and the display indicates this....will the correct battery voltage be displayed then?

Frank at BZ has ignored my calls and email.  This has been a particularly tough problem for me since my system is 300 miles from where I live.  So when I go there, I need to fix it THEN.  I am running 6ea. 75 watt panels with 10ea. Trojan T-105's.  Peak power in (for a limited amount of time) is 33 amps.  Mostly it is 24-28 amps.

Prior to the mppt 500, I had the M20 and M20+ both of which ran OK but I needed to add more panels and upgrade the controller.

[(unknown)]

don't know if anybody is still into this discussion, but i'm currently considering purchase of a bz mppt and have some concerns about lightning

not necessarily direct hits, but hits in the neighborhood that might spike voltages enough to destroy a microprocessor circuit

i notice the bz warranty does not include lightning --i've had one inverter that got knocked out in this way and possibly two other controllers,  

 better grounding would help some, but i've heard of similar problems with inverters from others more diligent than myself with grounding details

any thoughts?

bob