Lobster boat PV and controller(s)

EatMaineLobster

Need advice! Hi, I have an ongoing project of building an electric lobster boat here in Maine. http://www.affordableacadia.com/2012/electric-lobstering-in-lamoine-maine/ and http://www.affordableacadia.com/2012/electric-boating-the-range-issue/
My goal is to avoid shore tie-up at high tide to use shore power to charge my battery bank once a week. I have (6) Trojan T-105s in series (36v) and can check my traps for 2-3% of my battery life. I have built a roof upon which I plan to put 400 watts of flexible panels. (3) 130w panels would add up to 390w. My dilemma is about a charge controller. I have read about PVM VS. MPPT and would like to go with the MPPT. Is there an MPPT controller rated for 36v or would I be better off using one controller for each panel? If I used 3 would I combine the outputs for my 36v battery bank or connect each output to two batteries? Bear in mind that this is a harsh salt water environment and I am not into spending a lot when I can still use shore power. Still, the option of solar would give me greater range. I am thinking of using the Sacred Solar 130 watt 5444-01 VOC 29.4v ISC 5.76A. http://www.sacredsolar.com. Thanks.

BB.

Re: Lobster boat PV and controller(s)

Welcome to the Forum.

Some comments:

EatMaineLobster wrote: »

My goal is to avoid shore tie-up at high tide to use shore power to charge my battery bank once a week. I have (6) Trojan T-105s in series (36v) and can check my traps for 2-3% of my battery life.

What do you mean by "battery life"? Depth of discharge or "cycle life"? (using 3% of the electricity stored or you will need to replace the batteries after 33 trips to sea?)

I have built a roof upon which I plan to put 400 watts of flexible panels. (3) 130w panels would add up to 390w.

In general, I am not a big fan of flexible panels. They tend to not be as efficient (need about 2x the the square footage to capture the same amount of energy as a set of poly or mono crystalline panels--Mono crystalline panels are usually the most efficient per sq foot).

Also, flexible panels tend not to last as long as glass panels (sometimes as sort as a few years in marine environments). Check the references on any brand of solar panels you purchase.
36

My dilemma is about a charge controller. I have read about PVM VS. MPPT and would like to go with the MPPT.

For a "small" solar array/PV system (less than 200 watts is "small", over 800 watts is large)--A PWM controller tends to be an OK solution. Good bang for the buck and a MPPT controller will not gain that much energy (perhaps 10% or so) in colder weather.

The down side is finding a PWM controller that will support 36 volt battery bank (the standard for solar is 12/24/48 volt). Perhaps the MorningStar TS xx amp family of PWM controller can be programmed for 36 volts with a computer dongle/cable (you will need to contact MorningStar and/or check out there support documentation for details).

If you could converter to 48 volts, it may be worth the effort.

Next, the real advantage to MPPT charge controllers is that they can take a wide range of input voltages and efficiently down convert from high(er) voltage/low(er) current to low voltage/high current for charging the battery bank.

For efficient PWM controllers (and minimum voltage for MPPT controllers), you need to match the Vmp of the solar array to the battery bank in use. Nominally, you will usually find "battery compatible" solar panels with Vmp in the range of ~17.5 to 18.6 volts or so... For a 36 volt system, 3x that amount or ~52.5<Vmp<54 volts for a 36 volt system. If you can get solar panels with Vmp in that range (and/or series/parallel connections of lower voltage panels that will meet that specification), you will be OK. But that is going to be rare, require custom panels, or just not possible--Sort of pushing you to using a (more expensive) MPPT charge controller for efficient battery charging.

Is there an MPPT controller rated for 36v or would I be better off using one controller for each panel? If I used 3 would I combine the outputs for my 36v battery bank or connect each output to two batteries?

Yes, many MPPT charge controllers are programmable for 36 volt operation with a computer (and usually a special adapter) to program to the correct voltages. Plus there are usually logs you can download, if you wish.

It is possible to use 12 volt (or a 12 and 24 volt controller) and charge sections of your battery bank. That may be a reasonable solution too for your needs. Note you have to be careful because many charge controllers, if you use external meter or communcation connections will have shifted electrical grounds--So you don't want to interconnect the accessory wiring together in a common network.

Bear in mind that this is a harsh salt water environment and I am not into spending a lot when I can still use shore power.

Many of the smaller PWM charge controllers (12/24 volt) from Morningstar have conformal coated electronics--Can last a bit better for needs--But you still don't want to get them wet/salty.

Still, the option of solar would give me greater range.

Depending on how much energy you use per trip/day (that 2-3% question again)--For the most part, vehicles use a lot more energy than can be collected for a roof top solar array to be useful... A typical car uses around 300-500 Watt*Hours per mile (don't know about your boat's kWH per mile usage)... A 720 Watt solar array mounted flat on a roof may collect around:

720 watts * 0.61 system efficiency * 4 hours of sun per day = 1,757 Watt*Hours per typical summer day

Marine locations can have lots of clouds/moisture in the air, plus less than ideal solar panel orientation--But the above guess gives you an estimated 3-4 mile additional range on a good sunny day--Not huge.

I am thinking of using the Sacred Solar 130 watt 5444-01 VOC 29.4v ISC 5.76A. http://www.sacredsolar.com. Thanks.

The panels you are looking at have a Vmp~24.4 volts (they appear to be crystalline panels--so reasonably efficient).

That value is not a good match for a 12 or 36 volt battery bank... Referenced to a standard 17.5 volt panel at 12 volts:

17.5 volts / 24.4 volts = 0.72 = 72% "efficiency" vs "standard panel"

You could use one panel+PWM controller per 12 volt battery block--Just at reduced "useful" output. The "72% efficiency" is not a killer with PWM and still may be your best option at this time. Two panels in series for 48.8 volts is not great for charging a 36 volt system--But may be acceptable for your needs (at least to experiment). Being in Maine on the cold ocean waters may keep Vmp high enough for your needs (Vmp falls with increasing temperatures).

Your thoughts?

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

Bill, Thanks for the thoughts. I am not up to speed on terminology. When I said "battery life" I should have said "charge capacity", as in 3% of the 7200 amp hours in my bank. I have a Bogart TM 2025 meter, so I'm basing this on what it tells me. Naturally, I would not want to discharge below 50%, so 3% is really more like 6%.
I am committed to using flexible panels simply because the extra weight on my roof of glass panels is a deal killer--too much motion underway, like a pendulum. I realize longevity is a factor. Again, I may decide it's just too costly compared to shore power charging. The good news is that I am not using a stinky generator.
I realize the Vmp of the sacredsolar panel is not ideal. That's why I was shooting for MPPT. It is my understanding that an MPPT controller would take care of the voltage matching problem/efficiency loss. A Canadian company, Solar Converters, makes a series of 36v MPPT converters. The 20 amp one is $450. Ouch!
My power usage per mile is of course greatly dependent on speed. I can cruise at 4 MPH at 11 amps. Since I have 200 amp hours, to limit my discharge to 100 amp hours I could cruise at this speed for 100/11 or 9 hours, covering 9X4 miles= 36 miles. With an input of 3 130 watt panels I could substantially increase the range, especially if I used my meter to monitor power from my array. If I were to increase system efficiency to 90% with an MPPT controller then using your math assuming 4 hours per day and a 390 Watt array I could get 390 X .9 X 4= 1404 watthours/36= 39 amps, equal to 14 miles. This could increase my range to 50 miles on a sunny day. The next three days would be necessary to recharge at mooring, again, assuming sunny days and no bird poop. Bruce

BB. wrote: »

Welcome to the Forum.

Some comments:



What do you mean by "battery life"? Depth of discharge or "cycle life"? (using 3% of the electricity stored or you will need to replace the batteries after 33 trips to sea?)



In general, I am not a big fan of flexible panels. They tend to not be as efficient (need about 2x the the square footage to capture the same amount of energy as a set of poly or mono crystalline panels--Mono crystalline panels are usually the most efficient per sq foot).

Also, flexible panels tend not to last as long as glass panels (sometimes as sort as a few years in marine environments). Check the references on any brand of solar panels you purchase.
36


For a "small" solar array/PV system (less than 200 watts is "small", over 800 watts is large)--A PWM controller tends to be an OK solution. Good bang for the buck and a MPPT controller will not gain that much energy (perhaps 10% or so) in colder weather.

The down side is finding a PWM controller that will support 36 volt battery bank (the standard for solar is 12/24/48 volt). Perhaps the MorningStar TS xx amp family of PWM controller can be programmed for 36 volts with a computer dongle/cable (you will need to contact MorningStar and/or check out there support documentation for details).

If you could converter to 48 volts, it may be worth the effort.

Next, the real advantage to MPPT charge controllers is that they can take a wide range of input voltages and efficiently down convert from high(er) voltage/low(er) current to low voltage/high current for charging the battery bank.

For efficient PWM controllers (and minimum voltage for MPPT controllers), you need to match the Vmp of the solar array to the battery bank in use. Nominally, you will usually find "battery compatible" solar panels with Vmp in the range of ~17.5 to 18.6 volts or so... For a 36 volt system, 3x that amount or ~52.5<Vmp<54 volts for a 36 volt system. If you can get solar panels with Vmp in that range (and/or series/parallel connections of lower voltage panels that will meet that specification), you will be OK. But that is going to be rare, require custom panels, or just not possible--Sort of pushing you to using a (more expensive) MPPT charge controller for efficient battery charging.



Yes, many MPPT charge controllers are programmable for 36 volt operation with a computer (and usually a special adapter) to program to the correct voltages. Plus there are usually logs you can download, if you wish.

It is possible to use 12 volt (or a 12 and 24 volt controller) and charge sections of your battery bank. That may be a reasonable solution too for your needs. Note you have to be careful because many charge controllers, if you use external meter or communcation connections will have shifted electrical grounds--So you don't want to interconnect the accessory wiring together in a common network.



Many of the smaller PWM charge controllers (12/24 volt) from Morningstar have conformal coated electronics--Can last a bit better for needs--But you still don't want to get them wet/salty.



Depending on how much energy you use per trip/day (that 2-3% question again)--For the most part, vehicles use a lot more energy than can be collected for a roof top solar array to be useful... A typical car uses around 300-500 Watt*Hours per mile (don't know about your boat's kWH per mile usage)... A 720 Watt solar array mounted flat on a roof may collect around:

720 watts * 0.61 system efficiency * 4 hours of sun per day = 1,757 Watt*Hours per typical summer day

Marine locations can have lots of clouds/moisture in the air, plus less than ideal solar panel orientation--But the above guess gives you an estimated 3-4 mile additional range on a good sunny day--Not huge.



The panels you are looking at have a Vmp~24.4 volts (they appear to be crystalline panels--so reasonably efficient).

That value is not a good match for a 12 or 36 volt battery bank... Referenced to a standard 17.5 volt panel at 12 volts:

17.5 volts / 24.4 volts = 0.72 = 72% "efficiency" vs "standard panel"

You could use one panel+PWM controller per 12 volt battery block--Just at reduced "useful" output. The "72% efficiency" is not a killer with PWM and still may be your best option at this time. Two panels in series for 48.8 volts is not great for charging a 36 volt system--But may be acceptable for your needs (at least to experiment). Being in Maine on the cold ocean waters may keep Vmp high enough for your needs (Vmp falls with increasing temperatures).

Your thoughts?

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

Sorry, I meant 7200 watt hours in my bank, 200 amp hours assuming a slow discharge. Bruce

westbranch

Re: Lobster boat PV and controller(s)

EatMaineLobster wrote: »

When I said "battery life" I should have said "charge capacity", as in 3% of the 7200 amp hours in my bank.

I hope this is a mistake as later you say 200Ah.

What motor do you use? type HP

BB.

Re: Lobster boat PV and controller(s)

Sounds like the numbers will work out for you.

The Solar Converter is not really a "charge controller" (specifications are a bit confusing--says set point tolerance is 5%--For a charge controller you probably want a 1% or smaller tolerance). It may not work for your needs if you choose to put three panels in series (my recommendation for 36 volts) as this would exceed its maximum input voltage of 67.5 volts (cold weather Voc-array output).

Yea, for a full blown 36 volt capable solar MPPT charge controller, you are looking at $400 for a TS 45 amp MPPT MorningStar (plus optional meter) or a $500-$610+ Midnite or similar >60 amp charge controllers.

Note that batteries tend to sulfate faster the more time they spend discharged... You don't want to (for example) run the battery down to 50% state of charge and take 6 days to recharge--You should get above 75% State of Charge within the next day.

If you don't have one, a Battery Monitor (Victron is another good brand) would be a good idea.

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

Thanks Bill, I hadn't noticed the maximum voltage disparity and I didn't (and don't) know what "set point tolerance" is all about. That's why I signed up for this forum! I wish there were a way to build your own controller. It's hard for me to believe there's $400-$500 worth of stuff in those little boxes. Gold? Diamonds?
I think my Bogart TM 2025 serves as what you mean as a battery monitor since it keeps track of the amps in and amps out, giving a readout of the battery bank's state of charge. My only complaint about it is that the display is about impossible to read in sunlight. As for leaving batteries discharged, I wish there was a graph I could look at with % discharge VS. time before full recharge. To say hurry up and recharge begs the questions of how long you can wait and how deeply you can discharge. I realize self-discharge will increase over time, but never heard anything about consequences of delay with respect to sulphate. Assuming my 50% discharged bank (unlikely anyway) the next day could provide me with 39 amps and bring me up to 139/200 or 69.5% at the end of the next day. Not that far from 75%. Bruce

BB.

Re: Lobster boat PV and controller(s)

It is all trade offs... Your batteries won't die tomorrow--But they may in a few years.

Xantrex and Victron have LCD displays (the Victron is sold as a marine unit too--perhaps a bit more fisherman resistant? )... But, yes, the Bogarts work well too.

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

I wish I had 7200 amp hours, but it would sink the boat! My 36volts powers a Mars 0909 PM motor fitted to an old Chrysler outboard. The motor is rated at 5 HP, but I think that might be at 48 volts. I can reach hull speed of 6.5 MPH at full bore, 120 amps. Bruce

Photowhit

Re: Lobster boat PV and controller(s)

Something is hinky with your numbers, and now I'm confused, How far are you going on your 2-3% of battery capacity?

What numbers did you program into the Trimetric?

westbranch

Re: Lobster boat PV and controller(s)

If that is a 48 volt motor why are you using 36 volts? you would get more speed out of it and there are more electronics stuff that will work with 48 v than 36, at least it the RE field.

BTW you should use 100AH as the available power not 200Ah, since going past 50% or 100 Ah regularly, will hasten the eventual death of you battery.
So if you speak of 3% of the total (200Ah) it is 2 X the amount you actually can use safely. Probably better to use the actual Ah used than %'s.

Interesting topic.

EatMaineLobster

Re: Lobster boat PV and controller(s)

The rated amp-hours of the Trojan T-105 is 185 at the 5 hour rate, 225 at the 20 hour rate. I work with these numbers for convenience. I do not plan to discharge the batteries below 50% and have not yet even come close to this. I apologize if the 3% is confusing, I am used to it not meaning 3%, but 6%, or rather I charge before 60%. I do not want to use the motor at its maximum speed capacity. The extra speed would be wasted in a boat which can reach displacement hull speed at 36 volts. As for the choice of 36 volts, I was aware that many golf carts used this voltage and assumed, incorrectly as it turns out, that enough equipment existed to make my plan possible. My eighteen foot boat fits in my garage in winter and to put 8 batteries in it would in my opinion overload it. It's a six battery boat, with a seventh for the bilge pump. I found a 36 volt charger and motor controller with no problem. Why they don't make a 36 volt solar controller is not because 36 volts is inherently flawed, but because 36 volts is not a profitable voltage for some reason, like an orphan disease. I could add two more batteries, mismatched because they're newer, making my boat heavier and sinking it below the designed waterline, so I could add a 48 volt solar controller and panels but I choose not to compromise. I had no idea solar was so rigid. And expensive. The panels are starting to get reasonable, but the controllers are ridiculous, both in price and choices.

Photowhit

Re: Lobster boat PV and controller(s)

Specialty Concepts makes some PWM 36 volt Charge controllers on special order, Might be worth looking into. My guess is they do small batches so they may have some available. The unit I had 14? years ago was a sealed unit so that would handle the salt air better than others, Though You can 'seal' the midnite classic (MPPT type), I don't know how well I'd trust it with a lot of exposure to salt air.

Specialty Concepts link.

niel

Re: Lobster boat PV and controller(s)

interesting as i never knew they made electric boats. it seems you are stuck between a rock and a hard place with much of this. you complain of the extra battery weight could put your boat too low, but the weight of the pvs will also weigh it down some even though not as much as the batteries would. you may also need more area on the roof to work with and that green, black, yellow, and red thing on the roof could potentially shade things. moreover the angles off of that roof may not be good as you may want a more flat surface being angles limits you to always face a certain way as far as aiming the boat more toward south due to the slope to the front of the boat.

i don't have any real answers for these problems, but i can say i would feel very uncomfortable out there on the water just relying on a bank of batteries. to stay low speed could still also cause you to lose ground if there are any currents flowing the wrong way. i am in favor of some supplemental power out there and solar may just provide that, but the best arrangement and with what equipment is touch and go because of what is commercially available and the requirements of your boat and budget. i don't think you will stop having to get shore power, but the extra umph (power) from solar could slow down the draw enough to add some better efficiency and could add battery life.

EatMaineLobster

Re: Lobster boat PV and controller(s)

Well, the "they" is me. Most electric boats are converted sailboats by owners who want to cruise silently when the wind dies, but they have no qualms about starting up the diesel generator when they need it. The weight of the PV on my boat will have to be from the new flexible ones, not as rugged as the traditional, but a helluva lot lighter. We'll see how it goes. Bill turned me on to the Morningstar 45 amp charger which I guess is compatible with 36 volt systems, so I guess I'll have to stop complaining. Bruce

EatMaineLobster

Re: Lobster boat PV and controller(s)

Thanks for that link, I'll check it out. I'd like an MPPT charger however since it looks like my array voltage will be quite higher than my bank voltage. Maybe I can "pot" the MPPT charger myself. We boat builders use a lot of epoxy.

niel

Re: Lobster boat PV and controller(s)

i don't advise you potting any controllers as this could be detrimental in some of the parts dissipating the heat they have to get rid of. this could lead to parts failure and would probably void the warranty.

BB.

Re: Lobster boat PV and controller(s)

The 12/24/48 volt steps are handy because they are reasonable sizes... going to 36 volts is a 1/2 step and does not really really that different from 24 or 48 volts.

I think Exeltech will make 36 volt (very good) inverters if you ask nicely.

36 volts used to be common for boats, and back in the 1920's or so, 32 volts was popular for rural electrification (using wind mills). And I think 8 volts used to be somewhat popular with old cars when 6 volt systems just did not cut it.

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

Looks like the Morningstar Tristar 45 amp MPPT controller wants to be indoors, mounted vertically and with 6 inches of space above and below. While it will do 36v it doesn't look like I can mount it under the foredeck, and I certainly can't enclose it. Still searching!

EatMaineLobster

Re: Lobster boat PV and controller(s)

Sorry, I didn't respond earlier. I am amazed by the response to my project, your guys are a great resource. I discovered the numbers on my page were wrong. I had failed to multiply the hours of run time by the MPH, so for 4 MPH I can go 25 miles and still be at 70% charge remaining. At least without a headwind. As for the danger of being on the ocean with a finite range, here it's more like fjordland, lots of deep bays, islands and not much open ocean. I also have two 12 foot oars. Given the complexity of internal combustion, I really don't think there's much to be worried about. Probably the main difference between my boat and most electric launches is that my boat is built using lobster boat features, high bow, flared sides, robust construction. It rode at its mooring during hurricane Sandy. A dumb move, but no damage.
I also noticed on my page that I misquoted the bit about checking my traps, it took 3 amp hours of my 200 amp hours in my batteries. That's 3% of a 50% drawdown or 5% of a 30% drawdown. I don't know what the distance is, I didn't measure it. It worked out to 2 cents worth of shore power. Since I move my traps around a lot this number will change. Bruce

Blackcherry04

Re: Lobster boat PV and controller(s)

How about 3, 12 V mppt controllers and do a distributive charge on each 12v increment part of your 36 V bank. There are some cheap 10-15 amp charge controllers out there one for each panel. More than one way to skin a cat. Thats how you charge a 36 V trolling motor batteries in a Bass Boat. I understand what your trying to do, but the amount of Solar is miniscule compared to the amount your using.

Here is a China cheapo, sold under a couple different names.

http://www.tektrumcorp.com/solar_chargers

BB.

Re: Lobster boat PV and controller(s)

EatMaineLobster wrote: »

Looks like the Morningstar Tristar 45 amp MPPT controller wants to be indoors, mounted vertically and with 6 inches of space above and below. While it will do 36v it doesn't look like I can mount it under the foredeck, and I certainly can't enclose it. Still searching!

MPPT charge controllers have more waste heat because of the MPPT switching electronics (around 5% of input power). If your solar array/output current is less than full 45 amp rating, then the waste heat will be 5% of the lesser amount. The controller at 36 volts would be able to support a ~2,100 watt solar array--You would be a fraction of that amount--So the controller will need less ventilation in your application.

-Bill

EatMaineLobster

Re: Lobster boat PV and controller(s)

Yeah, that was part of my original question. Three 12v controllers, but why not just wire them in series and THEN wire to bank. That way there would be no chance of a part of the bank being undercharged because one panel happens to be in the shade. Please explain to me why this wouldn't work. The link to the cheap controller is much appreciated. I'm not trying to be a penny-pincher, I just can't let go of the fact that the whole project could go down in a storm. And somehow I don't think I could get insurance.

EatMaineLobster

Re: Lobster boat PV and controller(s)

That's good to know, and in line with my assumptions. On a related note, does oversizing an MPPT controller as in this case (45 amp capacity VS. 5-10 amps array) result in inefficiencies due to the mismatch? Would I be better off trying to find a 15 amp 36v controller? Bruce

BB.

Re: Lobster boat PV and controller(s)

You would not put the 3x 12 volt controllers in series--You would wire the +/- of each controller to its "12 volt" section of the battery bank. Basically, each controller would be responsible for 1/3rd of the battery string. Put fuses/breakers on both +/- leads from the battery bank to the charge controllers (in case of any short circuits).

It is possible for the batteries to be unequally charged if something goes wrong or uneven light to the 3x solar panels/arrays. But monitoring the specific gravity and 12 volt block battery voltages can alert you to uneven charging.

Your battery monitor will become a bit less useful as it will only be monitoring the charging current for the first 12 volt battery set.

-Bill

Cariboocoot

Re: Lobster boat PV and controller(s)

EatMaineLobster wrote: »

Yeah, that was part of my original question. Three 12v controllers, but why not just wire them in series and THEN wire to bank. That way there would be no chance of a part of the bank being undercharged because one panel happens to be in the shade. Please explain to me why this wouldn't work. The link to the cheap controller is much appreciated. I'm not trying to be a penny-pincher, I just can't let go of the fact that the whole project could go down in a storm. And somehow I don't think I could get insurance.

You can't wire the controllers in series without connecting the junctions to the battery as each controller needs battery Voltage on its input to function. If the only battery Voltage is on the negative of the 'first' controller and the positive of the 'last' controller the circuits inbetween will not operate properly.

One thing you must be very careful of when wiring panels & controllers to charge batteries this way: the (-) in and (-) out of most controllers is straight through. They must be kept isolated on each controller or you will create a short between controllers where the (+) of one meets the (-) of the next on the battery bank (because that negative can all-too-easily be connected to the negative of the other controller). With some controllers it's even worse as they have MOV's on the inputs which must be disconnected to prevent this shorting as well.

BB.

Re: Lobster boat PV and controller(s)

Yes, a large MPPT charge controller will have more losses (bigger switching transistors have more capacitive switching losses)--So, getting a smaller one would probably operate with lower losses. You could get a pair of MorningStar 15 amp MPPT 12/24 volt charge controllers -- One charging 24 volt of batteries, the other charging 12 volt of batteries (2/3 and 1/3 of your array). Still not cheap at ~$215 EACH (these are very good MPPT charge controllers--And you need to get the remote battery temperature sensors for them too for best operation).

-Bill

Cariboocoot

Re: Lobster boat PV and controller(s)

$215 + $215 = $430
Price of TriStar 45 MPPT: $390
Price of TriStar 45 PWM: $145

Just so you know.

EatMaineLobster

Re: Lobster boat PV and controller(s)

OK, all good info, thanks. I have been especially careful not to unbalance my battery bank. For example, I chose to get another battery to run my bilge pump rather than steal 12v from my bank, so to split it up with solar charging is kinda tough for me. Also, since it (one or two of the two or three) would be wired up to the bank not through the big shunt I have for my meter, it would not appear on my dash and the solar gain would be a mystery while underway, making it hard to guess range. Not only that, but the function of my monitor would not be accurate since it wouldn't "know" about one or two of the charging legs. I am glad to hear about the 24/12 split too (using 2 smaller controllers). That had occurred to me. Still, I think I have talked myself into a 36v controller, since they can't be wired in series. Let me know if I'm wrong about the monitor. Bruce

EatMaineLobster

Re: Lobster boat PV and controller(s)

Just re-read Bill's comment about the monitor. DUH! I should read more before I write!

BB.

Re: Lobster boat PV and controller(s)

Just to be clear--On average, the Batter Monitor with two or three charge controllers will be about as accurate as one 36volt controller--But if something goes wrong, it may not catch the problem (i.e., a charger fails, monitor does report the failure--bad news if you fail to catch it otherwise). You could put two to three simple digital volt (and/or current) meters--one on each charge block--so you can catch any charging problems visually--But adds costs and complexity--And still relies on you scanning/catching the problem before it causes you grief.

Not a great solution either...

-Bill