Solar Boost 3024i - Marine application

System

I have been tasked to locate two suitable Smart Regulators (MPPT types). The units will be used in two large sailing catamarans and the yachts will be moored in remote hot climates. Their systems are all 12V with one each small pure sine wave inverters for AC laptop power. After much searching the one that interest us are the Blue Sky Solar Boost 3024i with:
> Battery sensor, and
> IPN Pro-remotes

I have done the sums and numbers and believe the units to fit the job perfectly but, before purchase would like anyones thoughts on suitability and any additional considerations we should assess or include. On both yachts:
> The PV array will be made up of four (12v – 90W) SunPower monocrystalline panels,
> The units will be placed in series pairs, providing 24V - 10.2A lmp (or 11.0A lsc),
> Each panels rated voltage is 17.7V (Vmp) and an Open Circuit Voltage of 21.2V (Voc),

40A branch circuit protection will be built into the electrical.

Cabling will be with 4AWG at 8.5m (this includes cabling length from the controller to the battery) and we believe this should keep the Voltage Drop to around 1.5%.

The unit is to be wired outside the US however, in choosing the MPPT unit, we have used the US regulatory safety factor of 1.56 as a guide and came up with a maximum PV array current of 17.16A (using the 11.0A lsc), this places us well under the Blue Sky Solar Boost 3024i - 30A maximum. However, in their Installation and Operations Manual under ‘24V INPUT / 12V OUTPUT’, they state PV array current input should be limited to 12A (as this produces roughly 24A output). My calculations bring our normal PV array current input fairly close at 11.0A lsc (or 10.2A lmp). Are we playing it safe enough? Not sure. :?

Batteries to be charged/maintained:
Main Battery bank:

• 2 x 210 Ahr LIFELINE AGM batteries (12V, 210Ahr, 390min with 25A reserve)

If any wizards could cast their eyes over these figures and share any guidance or thoughts, it would be greatly appreciated.

James

niel

Re: Solar Boost 3024i - Marine application

you do have to go by the output current the controller would have as downconverting does double the currents outputted in addition to an average 10% gain on top of that for the mppt action. you may wish to go to another controller that higher up the output scale. the sb50 can output 50amps, but the sb50 as well as the 3024 can only take a max voltage around 57v so caution must be used in having the pvs in series as many have blown out at lower voltages. the mx60 is an option too that has lots of headroom for expansion or placing in series, but as the capacities and options go up so do the prices so that'll be your call. in any case use the remote temp sensor for it.
on another note, you are the first i've heard chime in here with sunpower modules. i've heard they are having output problems with their pvs in time so please tell us how they are doing and track their outputs over time for possible problems later. these are the ones with the power connections to each cell on the backs of the cells and are said to be around 22% efficiency. also tell who sold it to you as i am not aware of anybody in the us selling them to the public and at what prices they'd go for.

System2

Re: Solar Boost 3024i - Marine application

Niel

Thank you very much for helping me out.  :-D

I am now in the throws of finding data on the Solar Boost 50 for the reasons given and I appreciate the guidance.

Regarding the solar panels, they are sold in Australia from a group called Sun and Power. They were happy to forward data to me from this contact info@solar.net.au. The contact person was Ilya and his 90W units are currently retailing for A$700. The panels have been derated from 95W, are 1038mm x 527mm in size and weigh only 7.4kg each.

There efficiency factor is one of the reasons we went with the 3024i as this data can be downloaded to a laptop and analysed which is one of the questions I have about the Solar Boost 50. I have been unable to locate any information regarding the downloading of panel performance data (past and present).

I will hound you a little later with some more queries as they arise and keep you updated on their efficiency/inefficiency of the panels.

System2

Re: Solar Boost 3024i - Marine application

i have a question on this as this is an area im interested in, using the panels from this example can an mppt regulator connected to a panel that has a imp of 5.1 ever see more than the 5.1 amps the panel is rated for? ie will it ever see 6-7 amps
sean

crewzer

Re: Solar Boost 3024i - Marine application

will it ever see 6-7 amps

This depends on many factors, but promarily temperature. If the 90 W module was clean and correctly aligned under full insolation, if the charging voltage to the battery was ~14 V in bulk stage, if the charge controller and the wiring was 100% efficienct, if there was a light breeze, and if the ambient temperature was ~-10 C (module temp + ~25 C), the charge current could be 90 W / 14 V = ~6.43 A.

HTH,
Jim / crewzer

mike95490

Re: Solar Boost 3024i - Marine application

puremajek wrote:

Regarding the solar panels, they are sold in Australia from a group called Sun and Power. They were happy to forward data to me from this contact info@solar.net.au. The contact person was Ilya and his 90W units are currently retailing for A$700. The panels have been derated from 95W, are 1038mm x 527mm in size and weigh only 7.4kg each.

Are these the type of panels that loose power in the first few months of use (amorphous)
What's the guaranteed power output in 5 years?

System2

Re: Solar Boost 3024i - Marine application

no these are monocrystalline panels and the out put will be 17.9v and 5.1 a, i b also bought these panels
sean

System2

Re: Solar Boost 3024i - Marine application

will it ever see 6-7 amps

That's a good question. I've been wrestling whether to get a MPPT controller for a 130W RV solar system I'm planning on building. It theory, they sound great. However after understanding the details, I don't believe MPPT will work for me.

Take for example the 90W panel. It is specified at a cell temperature of 25C. A typical application may see 35C higher temp. The panel's power reduces by 0.49% per deg.C. The 90W panel now is reduced to (1-(.0049*35))*90W = 75W. The MPPT DC/DC converter will consume about 10W. That leaves you with 65W to power the battery (neglecting cable losses and assuming the panel is directly facing the sun).

The other option is to go with a standard converter. Your charging current is 5.1 A. The power delivered into the battery is 13V * 5.1A = 66W. The interesting thing is that this controller's power loss doesn't enter into the equation until the battery's charging voltage can't be met. The MPPT controller provides no benefit in this example. It may even reduce the charging capability.

Cal

System2

Re: Solar Boost 3024i - Marine application

Cal and all the others

Thank you for the input.

Thanks to this Forum, I located some other challenges. boB (a guru in this area) believes that MPPT technology

may not be suitable for arrays less than 200W.

This appears to be the case with many shops stating just this, but they can’t say why.

An additional issue I face is shadowing (by sails, masts etc), resulting in the MPPT internal wizardry working inefficiently (negating the reason for purchasing this technology in the first place). Depending on the MPPT controller, they use 15-minute electronic ‘checks’ and others use ‘inbuilt- tables’ for assessing their optimum power generation settings. In the Blue-Sky controller 3024 and 50 cases, it is apparently very simple as they use a percentage of the voltage on power-up to guess at the voltage maximum power (Vmp) point.

My scenario could be, sailing with the boom, sail or mast causing a shadow each time you tack. If the MPPT controller is adjusting its internal wizardry at that time, charging rates would be very inefficient or well below that normally expected. Other examples include:
> The keeling of the boat as it rocks,
> Tidal swing, and even
> Partly cloudy days with moving cloud.

I am undecided now and would appreciate any more thoughts

System2

Re: Solar Boost 3024i - Marine application

actually using your calculations but the correct cell loss figures of .38% we get (1-(.0038*35))*90 = 78.03w from the panel now if we assume a max bulk charge voltage of 14.4 we get ((78.03*.99)-1)/14.4v = 5.29 amps now solar boost claim a 1 watt overhead for the running of this controller now if we assume minimal voltage drops to the regulator im working on 1% we get  a .19a increase. this i would assume to be at the hottest part of the day with the gains being better in the earlier parts of the day due to lower temps, even if it was only .19a an hour this would mean an extra 100 odd watts a week which doesnt sound much but it beats a kick in the teeth and for an extra 200 up front expense sounds reasonable to me
now are there any major problems with these calculations are they 2 generous 2 cautious???
sean

crewzer

Re: Solar Boost 3024i - Marine application

The extra 100 Wh/week may not the best return on your AU$200 (~US$157) investment. Assuming an average of 5 hours of full Sun per day and 85% effective operational efficiency, a PV module rated at ~3-1/2 W would supply 100 Wh/week. In other words, how many additional PV module Watts could you buy for AU$200? For example, a 20 W module could supply 20 W X 5 hrs/day x 7 days/week x 85% = 595 Wh/week.

Seems to me that that would be better than ~six kicks in the head!

HTH,
Jim / crewzer

System2

Re: Solar Boost 3024i - Marine application

are there any major problems with these calculations?

Yes there are. You decided to reduce the controller's losses from 10W to 1W. Take a look at the specification. I chose this one. But they are all similar.

http://www.blueskyenergyinc.com/pdf/SB2000Edatasheet.pdf

There's a Charge On Power Consumpution = 70 mA typ

AND

Power Conversion Efficiency = 95% @ 15A output.

The TOTAL power loss of the controller is: 15mA * 13V + 15A * 17V * 0.05 = 14.7W

I used 10W because the charging current is less.

That's the reason PV systems less than 200W are not suited for MPPT. The MPPT controller eats up 15W/200W = 7.5% of your total power.

BTW, I didn't have the spec for this panel. I used a power loss of 0.49%/C taken from Evergreen specification. You used 0.38%/C. Is that a voltage reduction or power reduction?

You know, if you're hell-bent on using a MPPT controller, I would consider pumping sea water on the panels to keep their temp down. Now you'll see some power gains. ;-)

Cal

BB.

Re: Solar Boost 3024i - Marine application

Regarding why sub 200 watt panels should not use MPPT controllers... It depends on the size and design of the controller and how much "overhead power" is required to run the switching down converter (part of the losses are fixed--i.e., the MX-60 consumes around 9-10 watts before the first watt is generated for the battery).

For the Outback MX-60, you can download their manual and see where the efficiency goes to heck with lower power panels. Look at page 33 of the PDF file, and you will see some quite dramatic effects of efficiency vs panel size and voltage (controller is much more efficient at lower panel wattages at lower voltages... i.e., for a 24 volt battery bank and 240 watts of panels, 40 volt input is about 95 % efficient and 95 volt connected panels the MX-60 is about 90% efficient).

http://www.outbackpower.com/manuals.htm suggest downloading (right click/save) PDF file for MX60 SN5500+ from here
http://www.outbackpower.com/pdfs_manuals/MX60_Manual_6_2.pdf direct link to large PDF file may hang browser

And below 250 watts, the efficiencies (because of fixed overhead, and at higher Solar Panel voltages, FET switching losses) go all to heck (for the MX-60). I have not found similar charts for the SB-3024i (or a 12volt battery charging MX-60).

Based on real-life experience with my home array (3.5 kW STC rating), a 360 watt array would be spending much of its life generating at 200-250 watts where an MPPT controller (the size of MX-60) is not very efficient. And this is why a simple PWM controller may actually end up generating as much (if not slightly more) power than a very expensive MPPT for much of the year.

Again, this is not a hit against the Outback unit--from what I have read it is a very reliable and highly functional unit. However, it (like all equipment) does have its limits.

Poster "Puremajek" has confirmed the MPPT issues with Solar Guppy on this thread:

http://www.solar-guppy.com/forum/viewtopic.php?t=488

And Solar Guppy has pointed to this thread:

http://www.xantrex.com/forum/forum_posts.asp?TID=327&PN=1,

Hi Nigel, We expect to have our new solar charge controller available in Europe by Spring 2007. The price will be competitive with the MX60. The maximum charge rate of the XW Solar Charge Controller is 60Amps. It can be connected to arrays configured in paralleled strings up to 150V (open circuit).
The key benefits of this charge controller over the MX60 are:
1) True dynamic maximum power point tracking. The MX60 stops harvesting energy from the array every 7 minutes in order to do a mini-sweep to find the maximum power point voltage (Vmp). It then holds this Vmp for the next 7 minutes, missing any transient conditions. Our charge controller is more like a grid-tie inverter that continually tracks Vmp and is always maximimizing the energy it harvests from the solar array, even in quickly changing solar conditions.
2) Convection cooled - no fan. The XW Solar Charge Controller has a die-cast aluminum heatsink that effectively dissipates heat allowing it to operate at full current up to 45 degrees Celcius.
3) Integrated PV ground fault protection.
4) 5 year standard warranty.
I do have a few beta testers already lined up in Spain...

-Bill

niel

Re: Solar Boost 3024i - Marine application

the mx60 was designed for larger systems in mind so it does fall shy on the low wattage end. i have an sb50 with 2 us64s and the sb50 does not draw off more than a watt or two. if it were a case of 10-15w i'd drain my battery in no time. my battery is doing quite well btw. the bluesky stuff is at this time more suitable for mppting in the lower power pv ranges because it doesn't draw more than a watt or 2. there most certainly is a crossover point though because many straight pwm controllers are in the 10-25ma range for their operating requirements. do i gain through the mppt function on my sb50? i would say yes, but it is marginal or close to breaking even unless i'd disconnect the meter portion of my controller which is about half of the controller's consumption. my guess would be no less than 75 or 80w of pv for mppting with bluesky controllers(no meter) and depending on the circumstances it could go higher. now if you plan on expanding higher in power with more pvs then go for it. if you want to use a 75w pv in a basic configuration i'd really question the extra cost of that controller being you are close to the very best bottom breakeven point for power delivered. most times the breakeven point will be higher as in the example for my system. i intend on getting more pvs for my system, but just haven't been able to swing it lately.
A NOTE to any bluesky and other controller engineers is that you may gain by placing a switch on the meter in order to shut down the draw from it when it's not being read or temporarily not needed(which is most of the time).

System2

Re: Solar Boost 3024i - Marine application

specifically bluesky claim a 1 w overhead while producing power and .35w while on standby, part of my question earlier is do they include this figure in the efficiency claims of the unit and if not is this figure just 1 watt used when power is produced or do you have to multiply it as cal has by the output of the panel which blows the power used by the mppt out by quite a bit . as for being hell bent on using it, im not really i just dont mind spending an extra 200$ now on a controller and some dollars on the wiring to get the maximum effiecency as i just dont have the option of adding on extra panels later.
sigh i think that with every bit of understanding i gain my confusion doubles but i do really appreciate all the info and answers
:?
i think that the mx 60 then is out for me but the new xantrex sounds interesting
sean

System2

Re: Solar Boost 3024i - Marine application

if it were a case of 10-15w i'd drain my battery in no time.

Niel, I don't believe you understood my calculation or argument. The issue is to MPPT or not to MPPT.

The argument for MPPT goes something like this. We have a panel that produces 90W. Yet a conventional controller can only replace 13V * 5.1A = 66W into the battery. 24W are lost!!!! MPPT comes along and says, we'll use those lost 24W and boost your current by 24W/13V = 1.8A. That's a 36% gain in charging current. Not bad in theory.

Now the real world comes along. In order to use the 24W, you need a DC/DC converter. That means we need to convert the incoming 17V to 13V (or whatever). This is accomplished by switching MOSFETs working off a regulator, a transformer, rectifier and a filter. The spec states this efficiency is 95% (or better). It's hard for me to believe it's that good (but that's another story).

If the efficiency loss accounts for 10W, then this power is subtracted from the (boost) 24W. The boost current is no longer 1.8A, but 14W/13V = 1.1A, or a boost of 22%. That's as good as it ever can get. IMHO, claims of 30% boost are bogus. Also these calculations are at a 25C PV temperature. Add temperature and you'll break even (or even go negative).

The point is, the 10W does not discharge your battery. It reduces the boost current.

Cal

System2

Re: Solar Boost 3024i - Marine application

specifically bluesky claim a 1 w overhead while producing power and .35w while on standby, part of my question earlier is do they include this figure in the efficiency claims of the unit and if not is this figure just 1 watt used when power is produced or do you have to multiply it as cal has by the output of the panel which blows the power used by the mppt out by quite a bit .

I asked Bluesky technical support that question. This is coming from the horse's mouth:

Power consumption consists of both factors, 1) self consumption to operate the unit (0.35W / 1.0W), and power lost in the DC-DC power converter (~3-4%).

BTW, if I were in your situation, I would use MPPT and cool the panels with salt water. They're going to get wet and salty anyway. Might as well have the salt water work FOR you.

Cal

System2

Re: Solar Boost 3024i - Marine application

while i like the idea of cooling the panels via seawater there are two problems that i can see with this, one you either need to bucket it over the panels manually(tiring) or pump it up (which uses the power your trying to make), the second is the faact that while they will be getting salt spray all over them this is not the same as full immersion,. i would have concerns with full immersion and saltwater getting into the panel itself, this combined with the electrical current produced killing the panel off early
something i have thought of is using fresh water over the panels in a contained system utilising some sort of heat pump( no electrical power) to essentially supply you with solar heated water and at the same time cooling the panels down

also i now see where you are getting the 10w figure from per day i should hopefully still get an extra 16.5 w (90w-(conventional pwm=14.4*5.1)per panel which is 66w -10w which is 56w per day??

also my 100w a week gain is for just 1 90 watt panel as i have four i should get an extra 400w a week and im hoping this would be conservative
sean

BB.

Re: Solar Boost 3024i - Marine application

By the way, Solar Guppy had experimented with using water sprayed on panels to cool them (he lives in Florida). He found that it was not worth the time and trouble.

Also, that 3-4% consumption loss for DC-DC conversion is not really clear enough to understand where the losses are...

For example, from the BS 3024i manual:

Power Conversion Effcy. 96% typical @ 28 Volt 24 Amp Output

Losses would be 28*24*0.04= 26.88 watts of loss (heat)

Normally, losses are not all in one area... Part of the losses will be (I^2)*R losses--this is simply the current passing through copper and electronics (squared) * the resistance which becomes heat loss. This heat loss is proportional to the square of the current... Cut the current by halve, the heat losses go down by 75%.

The other major loss is the electronics and switching components used to change the DC solar panel into AC current, through a transformer (and/or inductors), then back into DC again for the battery... Those losses tend to be there when the switching circuits are on...

In the case of SB 3xxxi, we don't know which part of the 27 watts of loss at full power are I^2*R or are switching losses--typical design rules (for cost effective designs) would tend to make about half the losses as I^2*R and the other half be switching losses.

And remember, the switching losses are consumed by the controller before the first watt of power is transfered to the batteries. So, if you imagine a curve of power vs time of day for the solar panels, imagine subtracting 10 watts from that solar panel curve and the result is what is available for the battery/DC system (any values below zero watts would probably just shut down the controller and not consume power from the batteries).

For the MX-60, the switching losses are about 9-10 watts.

I believe that Solar Guppy measured at least one of the SB controllers--you might ask him if he has more information available... But in one thread, he already suggested that current MPPT controllers are not best suited for use on a sailboat.

-Bill

System2

Re: Solar Boost 3024i - Marine application

Bill-

There really isn't any mystery regarding the power losses in a DC/DC converter. I had designed them for a time period of 15 years. Some of my designs went into outerspace and others are on the battlefield right now. The main components consuming power are the switching FETs, the transformer and the rectifier diode(s). There aren't too many I^2R losses. They are easily controllable (unless you want to count the FET as a I^2R loss).

And remember, the switching losses are consumed by the controller before the first watt of power is transfered to the batteries. So, if you imagine a curve of power vs time of day for the solar panels, imagine subtracting 10 watts from that solar panel curve and the result is what is available for the battery/DC system (any values below zero watts would probably just shut down the controller and not consume power from the batteries).

That's right, the 10W will never consume power from the battery. I tried explaining that to Niel. It is consuming power from the solar panel, reducing its capability.

Regarding the water cooling of the panel. I had calculated a 15W decrease in solar power (per panel) when the panel temperature rises by 35C. The question is, how much power does it take to pump water up to the solar panels? I'm not talking about a mist, but a good water flow. If you have a minimum of 4 panels, I bet it's worth it.

BTW, I've enjoyed reading your posts. Learned a lot.

Cal

niel

Re: Solar Boost 3024i - Marine application

cal,
i do follow what you're saying here and you are right that it will take it from the pvs regardless of any claims otherwise. my point was my battery is not suffering for lack of available charge from my limited pv system as a result of using the sb50. you will never break even watt for watt as that is against the natural laws. i don't know all of the ins and outs of their engineering for mppts, but i know what is the end result and that's what i like to go by. in other words if it is doing better than on a straight pwm controller would do for me. your question is what wasted power went in to go out? i say if it wasn't being passed on by a regular pwm in the first place then it is using power that was normally wasted and the point is moot. it still reaffirms that there is a practical limit to using mppt in the lower wattage spectrum and i have no arguement with that, but the question you bring up are the particulars of the requirements of operation versus output realtime in the area of lower power input. one who could be that specific with you is Bob as he is our resident mppt expert. solar guppy on the other site could also bang heads with you some.
i have electronics background, but i'm no ee as a college degree is different from an associates degree. i should note that the teacher i had was some kind of head teacher in electronics for the entire state of pennsylvania(i didn't pay close attention to what it was called) and that the quality of the education i got was very good for an associates degree. i got a better education than the community college across the street from the school i attended would've gave me and i would've been an ee with that degree. they came over many times from the college seeking advise and answers from my teacher. this was many moons ago i should also add. not praising me, but making my education background more understood. it helps too when ones interest never die, but i never got to go further as i had wanted to do for many reasons.

System2

Re: Solar Boost 3024i - Marine application

Wow...

Really appreciate everyone taking the time to put pen to paper finger to email and the feedback has answered many issues for me.

Thank you

sv_makai

Re: Solar Boost 3024i - Marine application

Sorry to be joining this late I am a newbie here.

Earlier it was suggested that the MPPT controller was not the bet recommendation for use on a sailboat. I beg to differ with real world experince.

We just retruned from 3 years in the Caribe as a full time liveaboard cruiser. Makai is an electrically intensive boat. We do not camp. We carry 4 120 watt Kyroceas, 680 amp liguid cell bank, and a SB50L MPPT charger. For the first year and a half this was our primary source of battery charging.

1st it worked so well we would start seeing positive amps (low) as soon as the sun was on the morning horizon more than offsetting the unit draw and would be fully charged and floating by 10:30AM. The peak output we saw with the combonation was 33 amps vs a projected 28.4 from the panel spec pages about a 15% over projected) starting about 10AM until about 2:30 PM. Everyday with sun and very good outputs under clouds or partial shadings. Every amp you can add back is worth it.

The SB50L uses MPPT and PWM. MPPT is priamry when bulk charing and once it gets to floating it is PWM to keep te battiers topped without over charging.

After working with many other cruisers on thier systems and seeing how far behind the charging curve relative to Makai using PWM controllers (assuming similar sizes). I would recommend using MPPT for the additional gain and not worry about the loss, but a breakeven calculation needs to be done as stated earlier there is a certain breakpoint that one could go either way and get the same output. If your array is on the cusp the decsion to use mppt or not should be based on future changes. are you going to upgrade or add panels to the array. If you may do so in the future the extra espense today will be offset by not having to replace the charge controller in the future.

When actually cruising it is important to maxiimise the PV array and the battery charging. You will find as we did that a carefully planned energy budget changes once you live on the boat and cruise and see how things really work. You always need more power than you planned, we did and we have met only one boat that didn't need a change, but the traveled on a 27 footer and it was like backpacking.

System2

Re: Solar Boost 3024i - Marine application

sv_makai, glad you can join us. Nothing beats real data.

There are reasons you get a MPPT boost.

1. You’re operating somewhere around 19 degrees N latitude. That’s getting close to the equator and your solar energy collection efficiency is very high. I define the PV collection efficiency (for a horizontal laying PV panel) as: sin(sun altitude). For example, on June 1 at 10:30 the sun’s altitude is already at 0.93. At noon it’s at 0.998.
http://www.susdesign.com/sunposition/

2. You have 4 120W PV panels. The 10 to 12W converter loss is insignificant when dealing with 480W.

It would be interesting seeing how the boat does with a standard controller. I don't believe it would be much different.

BTW, I did some calculations based on the fact your batteries are charge by 10:30 (in the summer) and estimate the Makai has a 800 W-hr load. Is this in the ball park?

Edit. After thinking about it, I can't determine your load. 800 W-hr is the energy I calculated that 'fully' charged the battery by 10:30 am when located on the 19 deg N. latitude on June 1.

Cal

crewzer

Re: Solar Boost 3024i - Marine application

SV,

Great report! Now, about this statement:

The peak output we saw with the combonation was 33 amps vs a projected 28.4 from the panel spec pages about a 15% over projected)

It would be interesting to understand more about the source of the "extra" current:

1) Kyocera's specs are +10%/-5% (I think..)... I wonder how much (if any) of the "additional" current was from well-performing modules?
2) Module specs are based on, among other things, 1,000 W/m^2 insolation. Higher insolation (i.e., in the Tropics where the atmosphere is geometrically thin, or in the desert, where the air is dry) will also lead to higher module current.
3) How much of the bulk stage gain was directly attributable to net MPPT boost. Specifically, how many Volts and Amps were going into and then out of the SB50?

It's my view that a PWM controller would also deliver higher than "panel spec" current under conditions (1) and/or (2) above. I own an MPPT controller myself, and I have no reason to doubt your sustained 33 A claim. I'd just like to understand the details behind it. Here's why: When summer camping in the Rocky Mountains, I saw my old PWM (non-MPPT) controller regularly deliver 20 A at mid-day from an array rated at 17.9 A. The explanation? Well aimed modules + thin and dry mountain air = insolation > 1,000 W/m^2.

Thanks!
Jim / crewzer

System2

Re: Solar Boost 3024i - Marine application

thansk guys for all the input and for clarifying a few issues for me, now all i have to do is work out whether i can get away with the solar boost 30 or whether i need to go the 50, the mx sounds like it might use a little more power than these so i ahve for now crossed it off, i think i would like the 50 better as i can run my panels in series reducing wiring size however it is another 300dollars

now the little instruction book that i got with my panels sayd that you need to multiply the voc and isc rating by 1.25 when determing component voltage ratings, conductor ampacities fuse sizes and siZe of controls connecvted to pv output and that an additional 1.25may be required by the nec code for sizing fuses and conductors

nowif i run all my panels individually, to determine which controller i get i multiply (isc)5.5*4*1.25 i get 27.5 which is under the 30 a max of the 3024, would i need to multiply this by another 1.25 or not as this would put me over the 30 a

if this i did need to then i am obviously in the area for 5024 and i can put my panels in series
sean
sean

niel

Re: Solar Boost 3024i - Marine application

be carefull in putting pvs in series on the bluesky stuff as they have low voltage ceilings on most of their stuff. it states 57v for my sb50. you might say that that's not a problem putting 2 12v pvs in series on it, but keep in mind that the 12pvs have higher open circuit voltages and i heard that some of their stuff blewout below that 57v mark. just know what the pvs are capable of before you put it to that kind of controller. other controllers can have higher ceilings on the voltages like the mx60 as it is well over 100v.

BB.

Re: Solar Boost 3024i - Marine application

And I would not cross the MX 60 off because it uses more power based on what you have read here... I have never measured a MX 60 or SB XX (or even seen them in real life) to know apples to apples how much each harvests or which would be better for a specific application. A smaller SB 30 may be more efficient at lower currents simply because the FETs and other items are smaller and may "waste" less power using smaller arrays.

Asking Wind Sun and/or others who have experience with both would be helpful. And, even if there was 5% difference in the lab between models/mfg--It would be hard to even see that in real life (I have 5% difference between Sept thru November 2005 vs 2006--is that because my panels have aged (BP says that there can be a 3% loss when panels are first installed), because of dust on a 2006, now one year old installation, or because of weather (warm winter this year vs last year), more clouds?... I can't tell.

-Bill

niel

Re: Solar Boost 3024i - Marine application

hmmm. it could be all of the above too bill.

crewzer

Re: Solar Boost 3024i - Marine application

The MX60's internal power loss can be derived from the efficiency graphs contained in its user manual.

http://www.outbackpower.com/pdfs_manuals/MX60_Manual_6_2.pdf

My report on my own MX60's operating performance can be found here at the link below. With ~590 W going in, the internal operating- and conversion loss ("36 V" in, "12 V" out) was ~45 W.

http://www.outbackpower.com/forum/viewtopic.php?t=952

A 45 W loss may seem high. However, from a system perspective, that would need to be compared against additional losses if I ran 12 V over the ~87 feet from my array to the controller. Or, I'd need to buy some big wire. I need to redo this experiment with my new configuration (36 V in, 24 V out), as mt MX60's efficiency should now be better.

HTH,
Jim / crewzer

System2

Re: Solar Boost 3024i - Marine application

Jim-

I read your efficiency measurements/calculation. On problem I noticed is that you use two different current measuring devices. The differences in efficiency could be errors in shunt resistance.

Have you calibrated the shunt?

I know it's difficult, but I would use the same shunt to measure both incoming current and out-going current to the controller. Now you got an apples to apples comparison. You can also determine the differences in the out-going current between the controller measured current and your 100A shunt to develop a correction factor for future measurements.

Cal