Please critique my solar plans

[jbinbi]

Originally Posted by socaldmax

They are rated at 300 watts, keep in mind you'll probably never get full rated power out of a solar panel, even brand new, due to the way they are tested vs real world conditions. I have installed two of them with 410 watts of solar panels on them and they will produce 22 amps if there's enough current draw.

The theory behind putting 410 watts on a 20 amp controller was because the owners used them only in the winter, so in the summer they were only maintaining charge, in the winter they produced much closer to 20 amps than they would have with only 300 watts of panels per controller.

Yours would be much closer to the 300 watt rating per controller, you'd probably see peaks of 14-15 amps in the winter, closer to 18-19 amps in the summer (per controller.)

Right, but since my panels are 285 watts, that should be max of 24 amps at 12 V. So if I put a 20 A controller in there, I am potentially losing a few amps. I know that during bulk charge, voltage is a bit higher, so my amps are probably at 22, but still losing 10%. At float, not so big a deal since it does not require lots at that point.

Plus what about any overhead? I have read that if you have a 20A output, you should have a 25A controller , about 15-20% overhead is good for heat, etc. Is this true?

[socaldmax]

Originally Posted by jbinbi

Right, but since my panels are 285 watts, that should be max of 24 amps at 12 V. So if I put a 20 A controller in there, I am potentially losing a few amps. I know that during bulk charge, voltage is a bit higher, so my amps are probably at 22, but still losing 10%. At float, not so big a deal since it does not require lots at that point.

Plus what about any overhead? I have read that if you have a 20A output, you should have a 25A controller , about 15-20% overhead is good for heat, etc. Is this true?

Theoretically, that's pretty much what everyone recommends. In reality, you will never see 20 amps out of 285 watt panels, much less 24 amps.

Under STC, 285 watt panels would produce 23.75 amps at 12v, but you'll probably never see those conditions. If you were to monitor your MPPT controller, you'd see low output in the morning due to the sun being low on the horizon, and your batteries might start off at 12.4v (that's been my experience.) By 930 or 1030 am, the batteries were topped off at 15v, with the solar controller never exceeding 14 amps (230 watt panel in summer.) If the battery bank were larger and discharged further, I might have seen slightly higher current output (solely due to lower voltage), but again, unless you're using a self tracking system and it's summer and there is no shading at all, you'll never get 285 watts or 23.75 amps at 12v.

Usually, my system spends a lot more of it's time at higher voltages, like 13.5 - 14.8v. 285 watts/14v = 20.36A, but that's theoretical, you'll never see that much with cable losses, sun angle, etc.

Anyways, it's one option, certainly not the only one. The only 3 controllers I wouldn't recommend would be Go Power! (total junk), Tracer controllers (bad MPPT algorithm, they don't ever seem to lock onto the correct voltage) and the Blue Sky Solar Boost 2000e, which is an older design, no menu settings, all potentiometers and my unit doesn't seem to put out what the panels should be putting out and it's fairly expensive for a 25 amp controller, not to mention it's limited to 12v panels. The only reason I even mention the Eco-Worthy controller is I took a chance on one, was impressed with it's build quality (especially the gold plated connectors), impressed with it's MPPT tracking ability and it's low price, delivered.

[mitiempo]

Originally Posted by socaldmax

The only 3 controllers I wouldn't recommend would be Go Power! (total junk),

Go Power controllers are ok but they are both basic inexpensive pwm controllers. They do not offer MPPT controllers.

[socaldmax]

Originally Posted by mitiempo

Go Power controllers are ok but they are both basic inexpensive pwm controllers. They do not offer MPPT controllers.

I think I've seen a total of 4 or 5 of them, 2 of them completely failed and I was asked to replace them with something that worked. I don't think I've seen any other brand that failed, solar controllers are pretty reliable. No, I take that back, there is one more brand called BZ that I wouldn't recommend, it's a cheap knockoff of the Blue Sky SB2000e. It was eaten by acid flux that wasn't cleaned off, even if that had not happened, it never worked properly according to the owner. We replaced that unit with a Rogue controller and he was amazed at how much power he was getting from the same panels. Obviously the BZ controller never worked well at all.

[socaldmax]

Originally Posted by jbinbi

Right, but since my panels are 285 watts, that should be max of 24 amps at 12 V. So if I put a 20 A controller in there, I am potentially losing a few amps. I know that during bulk charge, voltage is a bit higher, so my amps are probably at 22, but still losing 10%. At float, not so big a deal since it does not require lots at that point.

Plus what about any overhead? I have read that if you have a 20A output, you should have a 25A controller , about 15-20% overhead is good for heat, etc. Is this true?

To give you another example, here's a 360 watt kit with one 20 amp Eco-Worthy controller over on Amazon. I think that the controller will occasionally peak at 22 amps at noon in the summer and they might be losing out on 1 or 2 amps, but they're probably banking on that being more than offset by the extra power gained during the winter and during the morning and evening. The 10% of the time you might not be getting that last amp is more than offset by the 75% of the time that you're getting an extra amp or 2 when you need it most.

Amazon.com : ECO-WORTHY 360W Poly Starter Kit: 2pcs 180W Solar Panel+Solar Cable+20A MPPT Charge Controller+MC4 Branch Connectors+Z Bracket Mounts : Patio, Lawn & Garden

[jbinbi]

thanks for all the helpful info. but since i have 2 285s, I would need 2 controllers (putting panels in parallel.) can these controllers work as Master / Slave? That is a reason I liked the Blue Sky, it seemed they can do this.

[socaldmax]

Originally Posted by jbinbi

thanks for all the helpful info. but since i have 2 285s, I would need 2 controllers (putting panels in parallel.) can these controllers work as Master / Slave? That is a reason I liked the Blue Sky, it seemed they can do this.

Yes they can, although they don't call it that. I've installed 2 systems with 2 EW controllers, both connected to the DC bus. Just set both controllers to the same charging voltage and float voltage and they work in tandem.

They also have a load control feature, which I don't use but it allows you to connect a load (lights for example) to it and you can program when it turns the load on and off - like on at dusk, off at dawn, or specific hours of the day, or at preset battery voltages, etc.

[mcarling]

Originally Posted by jbinbi

thanks for all the helpful info. but since i have 2 285s, I would need 2 controllers (putting panels in parallel.) can these controllers work as Master / Slave? That is a reason I liked the Blue Sky, it seemed they can do this.

Why would you need two controllers, unless for redundancy? You should be able to connect two (or more) panels with the same nominal voltage in parallel to one MPPT controller, using diodes to ensure that one panel does not send current through another (perhaps shaded) panel. Ensure that you don't exceed the current capacity of the controller.

[jbinbi]

Originally Posted by socaldmax

Yes they can, although they don't call it that. I've installed 2 systems with 2 EW controllers, both connected to the DC bus. Just set both controllers to the same charging voltage and float voltage and they work in tandem.

They also have a load control feature, which I don't use but it allows you to connect a load (lights for example) to it and you can program when it turns the load on and off - like on at dusk, off at dawn, or specific hours of the day, or at preset battery voltages, etc.

Originally Posted by mcarling

Why would you need two controllers, unless for redundancy? You should be able to connect two (or more) panels with the same nominal voltage in parallel to one MPPT controller, using diodes to ensure that one panel does not send current through another (perhaps shaded) panel. Ensure that you don't exceed the current capacity of the controller.

socal, thanks for all your help.

mcarling, because the controller socal had mentioned is max at 20A, and the one i was looking at was 25A, the panels are each 24A, so I need 2 controllers if I were to use these brands. I can find another 50A controller and use a single one.

[Stu Jackson]

Originally Posted by monte

heres our L380 power budget

Monte's point in his attachment should be clear: there are at anchor daily loads and there are passagemaking modes. The latter can be higher.

Here's another example, which includes three modes:

The All-Important Energy Budget:
Energy Budget

Don't know what you've taken into account in sizing your system.

Your boat, your choice.

[socaldmax]

Originally Posted by mcarling

Why would you need two controllers, unless for redundancy? You should be able to connect two (or more) panels with the same nominal voltage in parallel to one MPPT controller, using diodes to ensure that one panel does not send current through another (perhaps shaded) panel. Ensure that you don't exceed the current capacity of the controller.

The use of one controller per panel is pretty common, on roof top home systems they're called micro inverters. The reasoning is if the controller fails, you only lose output from the one panel. The other benefit in his case is if you have 2 panels in parallel on one controller and one gets shaded, power drops from both to an extent because the MPPT voltage from the 2 panels is now completely different, and since you can't have 2 different voltages on the same circuit, the controller will try to average the voltage which is not correct for either panel. One controller per panel eliminates this problem since the controller only has to find the correct MPPT voltage for one panel as conditions change (shading) which is common on a sail boat. You will always get the max. possible harvest with one controller per panel, if you don't mind the cost and extra cabling.

Also one correction, it's not harmful to exceed the current capacity of the controller, all the ones I've used will self limit at 100% to 110%. The thing you never want to exceed is Voc, especially on a cold day.

[Sea Frog]

Originally Posted by jbinbi

1. Choice of panels. Know lots of Kyocera, nothing of solarwind..

I have been recently reading good things about LG Neon 2 panels. 315 watts, high efficiency and all that stuff. Very high quality. And they are easier to get than Sunpower.

[jbinbi]

can anyone point me to a bus bar that I could use to hook the output of the 2 controllers into and take 1 wire out to the battery. Underneath my aft berth are all the batteries, and on the side wall under the berth is where the controller will be mounted. So as the crow flies it is about 2 feet of wire needed, however I would want to lead it down the side wall and on the floor up to the battery, so I would need to go about 5' maybe from the bus bar to the battery, and maybe a 1' or 2' from controller to the bus bar. Output to from bus bar to breaker, then to batteries unless someone says i should use one of the fuses at the battery post.

Again, appreciate all the advice. Understand most of the theory, just don't know practical ins and outs, like who makes bus bars , fuses, breakers for marine connections.

[vtomanov]

Originally Posted by monte

heres our L380 power budget

600W solar will give about 25amps or may be actually 15-20 average for 10h a day... you can make good saving with electronic control of the fridge and freezer .. |I installed one of this and my fridge started to consume about 30-50% less...

12V 10A Digital LED Thermostat Temperature Controller with Sensor Probe MH1210A | eBay

for me the big change is LiFePo4 battery as with 1h motoring I can put 100ah in the batteries.. and there is almost everyday ..1h motoring for something...

btw: my main consumer is the watermaker - about 100+ ah a day

[socaldmax]

Originally Posted by jbinbi

can anyone point me to a bus bar that I could use to hook the output of the 2 controllers into and take 1 wire out to the battery. Underneath my aft berth are all the batteries, and on the side wall under the berth is where the controller will be mounted. So as the crow flies it is about 2 feet of wire needed, however I would want to lead it down the side wall and on the floor up to the battery, so I would need to go about 5' maybe from the bus bar to the battery, and maybe a 1' or 2' from controller to the bus bar. Output to from bus bar to breaker, then to batteries unless someone says i should use one of the fuses at the battery post.

Again, appreciate all the advice. Understand most of the theory, just don't know practical ins and outs, like who makes bus bars , fuses, breakers for marine connections.

Bluesea makes pretty much everything you need for marine electrical systems. Bus bars, distribution blocks, fuse panels, fuse holders, circuit breakers, etc.

The best place to buy boat cable and connectors is bestboatwire.com (same company as genuinedealz.com) and don't forget to buy adhesive lined heat shrink. Use crimp connectors that are closed end to prevent moisture from entering the end of the cable, covered in heat shrink.

This is what a tinned, closed end connector looks like:




Here is what a hydraulic crimper with hex dies looks like, only $34 on Ebay:



Here is what a good crimp looks like with a hex shaped die crimper:




Here is what one looks like with heat shrink applied:



This should give you a good, long lasting connection with a minimum of internal corrosion and resistance.