BZ MPPT250 and other controllers

System

I wonder if some of the solar experts could help me diagnose the problem with my charge controller. I have talked to Manufacture and the retailer and they both claim the problem must be with my system.

I recently purchased BZ's MPPT250 controller. I really wanted to get one made in the USA and the write up from the retailer, a company called Go Electric in Alhambra California, made it seem like a good choice. Well, after I started having problems with it not performing as promised (I was actually get less amperage out of the controller than the solar array was producing), I asked if I could exchange it for a PWM controller. They gave me the run around and told me no one has ever complained so the poor performance in my system must be due to some other problem and would not do an exchange. Now that I have read about BZ's products on the various forums, I know I'm not the only one having a bad experience. Some experienced solar techs have even called BZ's controllers junk.

This is how my system was configured. There are 2 Kyocera 120 watt panels on the roof of my RV. the run from the panels to the controller is 12 feet of stranded 6 AWG. From the controller to the 12V battery bank the run is 13 feet of 6 AWG, for of 25 feet total. the panels were originally wired in series (per BZ's recommendation) and the batteries are brand new. On an average day in November at 11am, the panels produce 39v at 3.9 amps (readings taken at the back of the controller). The output from the MPPT250 to the battery bank varies from 2.8 to 5.7 amps at 12.5 to 13 volts. The manufacture had me check the voltage drop to the battery (they said the had to be the problem) which was 0.0 on the negative side and 0.03 on the positive side.

I thought MPPT controllers were supposed to have a 30% gain, that's why they cost so much. I really don't see how there can be a problem with my system as the retailer tried to infer because I was taking all the readings at the controller. I also told them that if the panels were wired in parallel, I felt I would be getting close to 8 amps from the array (which is why I wanted to switch to a PWM controller).

I have now rewired the array in parallel and it is producing 8.9 amps at 19 volts, but the MPPT250 is still only sending about 5amps to the batteries at 12.6 volts. Does this right? I thought the problem might be that the batteries cannot take more than 5 or 6 amps when their charged to 12.6 or 12.7 volts but no ones ever mentioned that. Also, there is a constant load on the batteries from the radio, water pump, and gas refrigerator that draws a small amount of current everyday.

Anybody have any ideas about the cause of my problem or was I expecting to much from the controller? Since a PWM controller is just a pass through device, I would at least get what the solar panels are producing. Right now, I think I'm losing half my capacity. BZ said there is no way the problem is with the controller,so I think I'll just have to wright it off as a loss (they never got back to me after the last call).

niel

Re: BZ MPPT250 and other controllers

bob b,
i didn't even read the whole post because that controller is junk and you should get your money back. you want an american product, then try this for size, http://store.solar-electric.com/mosumpsochco.html
if you plan on expanding your pvs much in the future then i'd suggest getting either 2 of those or go with outback's flexmax series. do know there is a fine line to made in america as the parts are certainly foreign and some may be assembled in other countries. i say this because you're eliminating any xantrex products and their xw mppt 60 cc is very nice too. you will find there are many straight pwm controllers out there as well, any of which will do better than something from bz. i am also mentioning appollo controllers and bluesky as being good too. here's our forum sponcer's link to controllers they sell and you can check them out. http://store.solar-electric.com/chco.html

n3qik

Re: BZ MPPT250 and other controllers

bob b,
The next sunny day when the sun is at its peak you need to turn on as many 12V loads as possible, especially the water pump. The battery voltage should drop to about 12-12.4VDC. Then note the current at the BZ control. The problem with any battery base system is you will never get to use 100% of the panel power.

icarus

Re: BZ MPPT250 and other controllers

Sorry to say,,BZ=BS=Junk!!

Do a search on this site for some technical analysis that someone (solarguppy maybe) has done with theses controllers.

I have one that Phil sent me for testing and I won't put it on anything!

Sorry, but DEMAND your money back.

If you don't want to spend the big money on the Outback MX, consider the Bluesky 2512 series. They are priced about the same as the BZ, but without the problems. I gain ~20% on mine over my pwm controllers.

Tony

Moe

Re: BZ MPPT250 and other controllers

BZ Controller thread

Windsun

Re: BZ MPPT250 and other controllers

If you bought those panels around the end of 2000 or early 2001, you might want to check the panels themselves. There were some bad KC-120's manufactured at about that time period.

BB.

Re: BZ MPPT250 and other controllers

To clarify with n3qik said--a battery charge controller will only output maximum current if the panels are:

A) pointing at the sun on a clear day (many RV's have the panels flat and the panels have shadows from an A/C, railing, antenna, etc. which can dramatically reduce their output)
if the battery voltage is low (battery needs charging and/or there are lots of 12 volt loads on the system)

During this time of year (and you are in the northern hemisphere), if it is warm and your panels are flat, you may get only 2/3'rds (or a bit less) of your panel's rated output on a typical day.

In your case, the panels produced:

39V * 3.9A = 152 watts
19V * 8.9A = 169 watts

Those numbers are certainly within the realm of good panels (depending on where you live, tilt of the panels, and current weather conditions).

With those input conditions, (and assuming ~90% efficient solar charge controller), the charge current going to your batteries should be (if the MPPT controller is working correctly):

152 watts * 0.90 / 13 volts = 10.5 amps into the battery
169 watts * 0.90 / 13 volts = 11.7 amps into the battery

Depending on the temperature of the battery, and settings on the solar charge controller, you will typically see around 14.2-15.0 volts (maximum--depends on how much solar power is available and current state of charge of the battery) at the battery while it is charging and around 13.8 volts if the battery is charged and the controller is "floating" the battery.

Read through the battery FAQ to and measure the battery voltage (after the battery has sat for a few hours without load/charging) and/or use a hydrometer (if flooded cell battery) to determine the current state of charge for your battery bank... If you are consistently undercharging your battery (which it sounds like you might be from the relatively low charging voltages), the battery will not last very long.

Your charger is charging, and the input power (Vin*Iin) seems sort of close to reasonable (depending on your local setup and conditions), but the output does not. Is the BZ controller pretty warm? Assuming those meter readings are correct--you are losing energy somewhere from the input to output.

The 30% power increase of using a MPPT controller over a properly installed PWM controller is typically a best case senario in cold conditions.

In any case, the equations above of calculating input panel power to output battery current/power should always be pretty accurate (if everything else is working correctly).

(and the BZ controller is not very good).

-Bill

System2

Re: BZ MPPT250 and other controllers

Thanks for the replys everybody.
BB pretty much confirmed how I thought the controller should be performing and Niel confirmed what I experiencing with the MPPT250's performance. I wish I had read about BZ products before spending 2 months trying to get it to work (and taking daily readings throughout the system). The retailer "Go Electric" wont even offer an exchange so I guess I will need to suck up the loss and get a new controller (obviously from a more reputable retailer than Go Electric).
I really think anyone that says these BZ controllers are performing well just hasn't bothered to take any Voltage and amperage readings to confirm what's going on in their system. I was an electronic equipment installer/tester with Verizon for 25 Years, so I really wanted to confirm my 30% increase.
The experience had made me a little leery of MPPT type controllers, but Icarus' post gave me some hope, so I'll probably go with his recommendation.

Isn't there some way to blacklist BZ with the retailers? I don't see how they can continue to recommend these products given their performance history. If you install a system and don't bother to take any readings to confirm how it's performing, you'll never know you've got a crappy controller (of course, as they say, sometimes ignorance is bliss).
Anyway, thanks again to all.

BB.

Re: BZ MPPT250 and other controllers

Bob B,

You are doing the best you can... Like a few others here who started with questions, found understanding, and shared the results+knowledge thoughtfully about this controller.

Since this site is hosted by a solar wholesaler/retailer itself--we try not to go off the deep end with recriminations that reflect badly on us all here.

We are all sorry for the experience and thank you for the information.

-Bill

Windsun

Re: BZ MPPT250 and other controllers

Bob B wrote: »

Isn't there some way to blacklist BZ with the retailers? I don't see how they can continue to recommend these products given their performance history.

Who is recommending them?

Not us.

We have never carried or sold any BZ products. On the other hand, we do not make up a list of products that we think are not good enough for us to sell, other than to say that if we don't sell it, there is probably a good reason.

BB.

Re: BZ MPPT250 and other controllers

Regarding retailers/websites carrying BZ controllers... Some of us here pretty much have come to the conclusion if somebody offers BZ controllers for sale, they are a scammer business/website.

-Bill

PhilS

Re: BZ MPPT250 and other controllers

BB. wrote: »

Regarding retailers/websites carrying BZ controllers... Some of us here pretty much have come to the conclusion if somebody offers BZ controllers for sale, they are a scammer business/website.-Bill

The retailer whose salesperson talked me into buying the BZ controllers I considered a reputable company. I've purchased from them a few times when something wasn't available from W-S... of course, that might be a good indication to not buy a particular product. Another indication might be if there is a constant turnover of salespeople, which has always been the case there too.

But I learn as I live. Sorry Bob B didn't learn about BZ from my mistake instead of learning for himself.

Merry Christmas to you all!!

Phil

Windsun

Re: BZ MPPT250 and other controllers

BB. wrote: »

Regarding retailers/websites carrying BZ controllers... Some of us here pretty much have come to the conclusion if somebody offers BZ controllers for sale, they are a scammer business/website.

-Bill

Not always - with all the solar hype going on nowadays, there are a lot of startup solar companies that quite frankly, don't have a clue.

Just for the record, a few of the brands we will not sell are:

Sunfrost
Staber
BZ
Any Chinese made wind generator
any Power-Save products

rplarry

Re: BZ MPPT250 and other controllers

Bob b
Your 30% expectation may not be realistic also. I know thats what they advertise, but in reality 10% is more like it. If you are in a cold, sunny climate then you can get more, but most of the time is less. Sorry,
Larry

icarus

Re: BZ MPPT250 and other controllers

Cold weather, AND low battery voltage will give you better mppt yield. On the other hand, it doesn't make any sense to over draw your battery just to 'increase' the mppt yield.

Merry Christmas,,,Tony