Question about Renogy solar panel system

[newhaul]

Originally Posted by Rohan

Maybe I should have added one more detail then - I didn't provide those specifics because I bought this system as part of a kit, everything included, so I can assume the wiring is the correct size, etc. Specifically it was this kit right here:
https://www.renogy.com/200-watt-solar-flexible-kit/

The panels are slightly curved on top of my bimini. Zero shade around other than from the boom. But I don't think shading or position is a factor because while my results changed, my boat's position and the overall weather hadn't changed at all.

As others have stated you need to hook panels in parallel pos to pos neg to neg then to your pwm charge controller. After the charge controller the pos lead to the positive bussbar ( with an appropriate fuse or dc breaker inline between controller and bussbar) and the negative to negative bussbar .
All will be well .

[Spot]

In looking at the diagram I put up yesterday, it may be missing some fuses or breakers:
1. between panel(s) and charge controller (one each panel?)
2. between batteries and selector switch (one per battery or one per bank?)

My own boat currently does not have one between the PV panel and controller but does have one between the controller to battery and battery to main panel / house.

I can re-post the picture once I know the revisions to make.

[Rohan]

Originally Posted by waterman46

Which battery terminals did you connect to? That diagram is correct. You need to connect the + solar output to the common +12V bus, not to one or the other batteries and certainly not directly to both banks at the same time.

And be sure your solar controller negative is connected to the 12V negative bus of your boat.

The instructions said the wires go from the controller to the battery, so I just did it that way. I attached to one battery. I wanted to keep it as simple as possible.

[Boatwright]

Two things:

You absolutely need an MPPT controller with your panels wired in parallel.

Also, good connections and correct wire size. This spring when we first put the system in service, we had very low solar output -- turned out it was a poorly designed rusty in-line fuse holder.

We also have 200 watts of Renogy semi-flexible panels with 12v refrigeration. Here in Michigan during typical summer weather this setup provides 100% of our electrical needs. The typical mid sunny day output is 130 -140 watts. Over the cruising season the output averages 1 KWH per day. Very occasionally (once so far this year) during prolonged cloudy wx we have to top off the batteries with our alternator.

[newhaul]

Originally Posted by Boatwright

Two things:

You absolutely need an MPPT controller with your panels wired in parallel.

.

I assume it's a typo but no you dont need an mppt controller if panels are in parallel however you do if they are in series.

[Boatwright]

Originally Posted by newhaul

I assume it's a typo but no you dont need an mppt controller if panels are in parallel however you do if they are in series.

You may not "need" it, but on the average an MPPT controller will be about 20% more efficient.

The output voltage of this "12v" panel array connected in parallel is about 20 volts, connected in series 40 volts. In both cases well above the 14 v needed for charging. The MPPT controller functions as DC-DC converter. It drops the panel voltage down to the voltage required to charge the battery. The current is increased in the same ratio as the voltage is dropped, and as panel output varies through the day efficiently matching the charging load to the panel output.

[newhaul]

Originally Posted by Boatwright

You may not "need" it, but on the average an MPPT controller will be about 20% more efficient.

The output voltage of this "12v" panel array connected in parallel is about 20 volts, connected in series 40 volts. In both cases well above the 14 v needed for charging. The MPPT controller functions as DC-DC converter. It drops the panel voltage down to the voltage required to charge the battery. The current is increased in the same ratio as the voltage is dropped, and as panel output varies through the day efficiently matching the charging load to the panel output.

I am a retired shipwright and yes I agree if you have no more space for panels then an mppt is the next step however you stated you absolutely need an mppt for 12v nom panels in parallel which while nice is not required.

[fguptill]

I have been running a system similar to yours for 16 years. Two 100 W panels wired in parallel with an MPPT controller. On average, the panels provide enough power to keep my refrigerator running - just. To be precise, I get an average of 50 Ah per day out of my system, and have been doing so fair consistently for 16 years.
In other words, your system performance is exactly what I would expect. Change to an MPPT controller and you will probably get a 15% improvement in power output.

[Boatwright]

More on the subject:

The last poster reports 50 AH per day, approx 650 WH. We get 900 - 1000 WH. These amounts are definitely in the range of what you should expect from your panel set-up. It may be cloudier in Nova Scotia than Michigan, or his older panels may have degraded a bit.

Our Isotherm Danfoss BD35 refrigeration compressor runs an average of 2.5 hours per day (we have an hour meter installed and note the dates and times in the maintenance log). On the hottest days in mid-summer (highs 85 - 90 F.) it runs a bit more, 3.5 hours. The measured amp draw is 4.6 amps. Total is about 200 WH per day max. This 1/4 or less of our panel output. The Isotherm specs rate the unit at 210 WH per day, so I am confident in our system's performance.

Our old chest used as much as 80# of ice on a three day weekend, which is typical in older boats. When we installed the Isotherm, we also rebuilt the chest with 4 - 6" of foam, fiberglass liner, and a double sealed lid.

Assuming you don't have a big problem with how it is installed, such as bad connections or too small wiring, your problem may not be solar.

Have you considered evaluating the heat loss from your box with the compressor turned off? This can be done by timing how long in takes to melt a measure of ice. 5# (5 pints) of ice takes real close to 200 WH to melt (42 WH / lb.). As I mentioned, our old box would melt 25# / day.

Is it possible that your refrigeration system has lost some refrigerant, is not cooling the condenser properly, or has a control problem? Did you load the box with a bunch of warm beer before you had the low battery?

Did you note your battery voltage with everything off? Wait an hour and then read the voltage. This can give a reasonably accurate measure of the true SOC. (Please -- no need to point out that this method is not the 20 hour rest, temperature compensated, etc. method. It will however give you a useable idea of your batteries State of Charge.) What kind of batteries do you have, how old are they, and has their true capacity under load been accounted for?

These situations could mean your compressor is running 24 hours / day, instead of the few it should. Your batteries could be shot. Your chest is too big or is too poorly insulated. You have a refrigerant leak, your condenser coils or water intake is clogged, or some other problem affecting the performance of your refer system. Etc....

Make sure you carefully consider and test all possibilities before you fixate on one thing.

[newhaul]

Originally Posted by Boatwright

More on the subject:

The last poster reports 50 AH per day, approx 650 WH. We get 900 - 1000 WH. These amounts are definitely in the range of what you should expect from your panel set-up. It may be cloudier in Nova Scotia than Michigan, or his older panels may have degraded a bit.

Our Isotherm Danfoss BD35 refrigeration compressor runs an average of 2.5 hours per day (we have an hour meter installed and note the dates and times in the maintenance log). On the hottest days in mid-summer (highs 85 - 90 F.) it runs a bit more, 3.5 hours. The measured amp draw is 4.6 amps. Total is about 200 WH per day max. This 1/4 or less of our panel output. The Isotherm specs rate the unit at 210 WH per day, so I am confident in our system's performance.

Our old chest used as much as 80# of ice on a three day weekend, which is typical in older boats. When we installed the Isotherm, we also rebuilt the chest with 4 - 6" of foam, fiberglass liner, and a double sealed lid.

Assuming you don't have a big problem with how it is installed, such as bad connections or too small wiring, your problem may not be solar.

Have you considered evaluating the heat loss from your box with the compressor turned off? This can be done by timing how long in takes to melt a measure of ice. 5# (5 pints) of ice takes real close to 200 WH to melt (42 WH / lb.). As I mentioned, our old box would melt 25# / day.

Is it possible that your refrigeration system has lost some refrigerant, is not cooling the condenser properly, or has a control problem? Did you load the box with a bunch of warm beer before you had the low battery?

Did you note your battery voltage with everything off? Wait an hour and then read the voltage. This can give a reasonably accurate measure of the true SOC. (Please -- no need to point out that this method is not the 20 hour rest, temperature compensated, etc. method. It will however give you a useable idea of your batteries State of Charge.) What kind of batteries do you have, how old are they, and has their true capacity under load been accounted for?

These situations could mean your compressor is running 24 hours / day, instead of the few it should. Your batteries could be shot. Your chest is too big or is too poorly insulated. You have a refrigerant leak, your condenser coils or water intake is clogged, or some other problem affecting the performance of your refer system. Etc....

Make sure you carefully consider and test all possibilities before you fixate on one thing.

We already have deduced the op has issues with his solar install let's get that straightened out first before throwing other stuff at him shall we .

[Boatwright]

FYI:

There is a difference between a battery's State of Charge and a battery's Capacity.

A 20 AH motorcycle battery at 75% SOC has used 5 AH.

A 200 AH deep-cycle marine battery at 75% SOC has used 50 AH.

The same 200 AH battery at the end of its life may have only 40 AH capacity.
At 75% SOC it has used only 10 AH.

Big difference.

BTW: Many so called "Marine Deep Cycle" batteries are nothing more than a slightly heavier duty automotive starting battery. And please note there is absolutely no relationship between "cold cranking amps" and the AH capacity of a battery.

[Stu Jackson]

Wow. This thread wins this week's Thread Drift Award!

[newhaul]

Originally Posted by Stu Jackson

Wow. This thread wins this week's Thread Drift Award!

Reminds of a member in Canada wrt battery threads.

[newhaul]

Originally Posted by Boatwright

FYI:

There is a difference between a battery's State of Charge and a battery's Capacity.

A 20 AH motorcycle battery at 75% SOC has used 5 AH.

A 200 AH deep-cycle marine battery at 75% SOC has used 50 AH.

The same 200 AH battery at the end of its life may have only 40 AH capacity.
At 75% SOC it has used only 10 AH.

Big difference.

BTW: Many so called "Marine Deep Cycle" batteries are nothing more than a slightly heavier duty automotive starting battery. And please note there is absolutely no relationship between "cold cranking amps" and the AH capacity of a battery.

The op states specifically large AGM batteries so one would assume 220 or so AH capacity each.
Why muddy the waters .

[Grattaway]

Rohan hi
Have you got enough info to sort your problem?

Noelex is right - panels need to be in parallel with the controller you have

But it was a bit unclear as to what you are doing at the battery end as you said you had 4 batteries connected together but in a later post you said you had two banks

So is it 4 12 volt batteries all in one bank giving 12 volts out or is it 2 batteries together giving 12 volts out and then another 2 batteries together giving 12 volts out such that you could switch from one to the other.

If its 4 batteries together then your wiring is such that you charge all 4 batteries as a bank - and not just one of them - from your one controller with panels in parallel

if you have 2 separate banks then in my ideal world you would charge one then the other rather than both at the same time - could be via a switch, controller or some such smarts which others will have more understanding than I

Wayne