Houseboat Solar Setup

System · September 2011

Hello All,

My uncle and I just finished building a houseboat in May. He tried to design the boat to run completely on Solar, but there is a backup generator in case the system had problems. When we first put the solar system in it worked great for about 6 months. We were still in the ship yard when the system first came online. The battery level would drop to about 82 percent during the night and then charge back up in the morning. Just recently the problem we are having is the Charge Controller stays in Bulk mode and the batteries don't get past 66% charge. It stays in Bulk mode all the time. We recently had to replace one battery because upon load test it failed. The Charge Controller will not move into Absorption mode. The only way I can get it to go into Absorption mode is to connect only one battery to the Charge Controller.

Here is my setup:

SOLAR ARRAY: ( 8 ) BP3175B 24 VOLT PANELS

- WIRED IN PARALLEL.

- NOTE: ON A GOOD DAY AT 12 NOON THE PANELS WERE PUTTING OUT 30
VOLTS AND 3.8 AMPS EACH. THE OPEN CIRCUIT VOLTAGE WAS 38.6 VOLTS.

CHARGE CONTROLLER: OUTBACK FLEX 80

- NOTE: THE WIRES BETWEEN THE SOLAR ARRAY AND THE CONTROLLER ARE
AWG #1 STRANDED. THE VOLTAGE AT THE CONTROLLER WAS 30 VOLTS AND
30 AMPS.

- THE WIRES FROM THE CHARGE CONTROLLER TO THE BATTERY BANK
ARE AWG.#4 STRANDED. THE POSITIVE LEAD IS 2 FEET LONG AND THE
NEGATIVE LEAD IS 7 FEET LONG .

- ON A GOOD DAY THE CONTROLLER PUTS OUT 13.5 VOLTS AT 60 AMPS.

- BATTERY BANK: ( 8 ) MK 8G8DLTP-DEKA 225 AH 12 VOLT BATTERIES.
THEY ARE WIRED IN PARALLEL.
FACTORY SPEC: CHARGE VOLTAGE 13.8-14.1 VOLTS
ABSORPTION VOLTAGE 14.1-14.4 VOLTS

- THERE ARE TWO MASTERVOLT 12/2000 INVERTERS. THE AC PANEL IS SPLIT BETWEEN THE TWO INVERTERS

MY MAIN AC LOADS ARE:

- REFER ENERGY STAR RATED AT 404 KWH PER
YEAR

- UNDER CABINET ICE MAKER 805 WATTS

- MICROWAVE 1200 WATTS

- COFFEE MAKER USED ONCE A DAY 1000 WATTS

- CABIN LIGHTS 25 WATT LED DOWN LIGHT.
-MAX USE 10 LIGHTS FOR 4 HOURS A NIGHT

- UNDER CABINET ICE MAKER 1000 WATTS

- MICROWAVE 1200 WATTS

- COFFEE MAKER USED ONCE A DAY 1000 WATTS

- SMALL LED ROPE LIGHTING USED FOR A COUPLE HOURS EACH NIGHT

- MISCELLANEOUS PHONE CHARGERS, SMALL ELECTRONIC DEVICES

Any help would be greatly appreciated. This is our first solar system. I tried to do the KwH per day calculations but I think I may have miscalculated….I came up with 22.25 KwH/day.

Here are my calculations: Everything is in KwH/Day
Refrigerator 1.1
Ice Maker 19.0 (This may be my culprit)
Microwave 0.3
Coffee Mkr 0.16
LED Cabin Lights (Cans) 1.0
Ceiling Fan .04
Alarm Clock .07
Stereo .48
Stereo (Stand By) 0.1

Total KwH/day 22.25
X 1.5 Fudge Factor 33.38

Solar Insolation for area 4.8 KwH/M2/Day

My estimated array size came out to 6,954 wats!!!! (Seems way too high)

My estimated battery bank came to 13,908 Amp Hours (Again I think I mis calculated)

Sorry for the long post. I would appreciate any help anyone can offer!

Houseboat1

Cariboocoot · September 2011

Re: Houseboat Solar Setup

Welcome to the forum.

Let's just check some of the numbers.
Array size: eight 175 Watt panels = 1400 Watts. Using the Icarus Formula you could expect that to yield: 1400 * 5 hours "equivalent good sun" / 2 (50% over-all efficiency) = 3500 Watt hours AC per day.

If your usage really is 22 kW hours per day you have a major insurmountable problem.

Batteries: eight 225 Amp hour 12 Volt batteries in parallel. That's a problem in itself. Nearly impossible to keep current flow even through that many batteries in parallel even with bus bars and careful attention to wire lengths. This is also an 1800 Amp hour battery bank (about 10.8 kW hours at most) which minimally needs 90 Amps of peak current to recharge. It is not possible for your array to supply this minimum charge, nor for the FM80 to pass it. Ideally you'd want twice that much current potential.

So your array can not properly recharge your batteries and your power usage exceeds the maximum production factor by a potential of 10X it seems. It's hard to believe an ice maker uses 19 kW hours per day: that's the equivalent of about eight full-size refrigerators!

I'd suggest you cut your battery bank in half, and then start shedding loads until you're down to under 3.5 kW hours per day. Right now your system seems to be behaving exactly how I'd expect it too for a chronically under-charged set-up: it worked fine until the batteries start to fail from not be properly charged.

System2 · October 2011

Re: Houseboat Solar Setup

Thanks Cariboocoot,

That makes a lot of sense.

I decided to recalculate taking the Ice Maker out of the equation. I believe I have the wrong usage information for that.

My numbers came out much more reasonable:

Total KwH/day = 3.25
X 1.5 Fudge Factor = 4.88 KwH/day Much Better!

New estimate PV Array size was 1016 watts

New estimated battery bank was 2032 Amp Hours

Does that seem more reasonable for my usage without ice maker?

So we should cut the battery bank in half and rewire in Series. Is that what you are suggesting? So we have too many batteries in the bank?

Also My total KwH/day is down to 3.25 without adding the 1.5 fudge factor now. Hopefully that will allow the system to charge back up.

Thanks again for all your help.

niel · October 2011

Re: Houseboat Solar Setup

you might benefit by using some meters to monitor your power. a killawatt meter can track the ac while a battery monitor can track the dc.

you may have problems with the other batteries as well if you were undercharging all of this time. if you have a good ac battery charger you can supplement the charge to the batteries along with the solar to bring them up to full. if they are compromised you may see them go to full quickly. hopefully you'll get some use with these before replacing the batteries, but i'd start saving for new ones.

i believe he is using agm batteries so he can't check the water levels or sg. this is a very nice and expensive bank of batteries. what a shame.

mike95490 · October 2011

Re: Houseboat Solar Setup

You need to dump the 12V system, and up to at least 24, and preferably 48V. @ 48V, you could keep the same batteries, and just rewire to 2, parallel banks of 4. That will allow you to get more power out of the charge controller. You may need more solar PV to keep up with your loads.

If you have a 1KW array, and a 5 hour sun day, AND optimum array aim, you could harvest 5000watt hours daily, and use 2500wh, with the rest going to system losses (wire, inverters, batteries) With arrays "flat" on the roof, you are going to harvest less.

Houseboat Solar Setup

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