Another solar question...

weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
New Jeanneau comes with the following setup.

2x80AH house batteries
1x80AH engine battery

The alternator is connected to a Cristec battery isolator. This is a MOSFET isolator (as opposed to a diode one) and the voltage drop is negligible at less 10 amps according to the literature attached below.

There is also a battery charger with 2 outputs; one output per battery bank.

I am going to be on mooring with this boat and not using shore power for the most part. In addition, I will be able to sail on/sail off so most days I won't even need the engine at all.

My goal is to keep the batteries topped off. I'm not looking to keep the fridge powered up...just running the basic DC needs....lights, fan or two, stereo, vhf, navigation electronics, etc. a couple days a week.

I figure a small, flexible 50W panel that I can stow when sailing should give me at least 8 to 10AH per day on average which should cover my needs.

My question is this. Can I hook up this small panel with a basic PWM controller connected to the "input" side of the battery isolator? In theory, this should keep both battery banks topped off as long as there is no voltage drop. I understand ACRs and combiners tend to be preferred here, but is there a need to change to an ACR just for this purpose?
 

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Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
The poblem is that this device requires ignition activation in order for solar or such to work properly. IIRC they call it an ignition ground that allows a solar controller to see voltage on the input stud. Most modern battery chargers, alternators, wind and solar controllers need to see a voltage in order to turn on. Diode isolators do not provide for this but some mosfet units do. The problem is you really don't want it "on" all the time at least that is what I was told when I contacted the manufacturer about this issue a few years ago. BTW I don't believe it is Christec that makes them, it is some Dutch company IIRC and Christec and some other private label them........

You can try the IG feature and measure the standby draw on the neg wire and monitor the heat of the unit but I would use caution as they only wanted it on when ignition is on for an alternator..

For the solar you could simply wire it to the house bank and leave the alt connected to the isolator. Engine batt would only be charged by alt but with a 50W panel you don't have all that much to work with anyway... On another note 160Ah's is pretty light if you plan to do overnights or ever use the fridge...
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
Well your literature is not very "correctly relaying accurate information" MOSFET is a type of semiconductor or you need to determine if it is a diode (with lower voltage drop) or a transistor unit that has a similar voltage drop but is turned on by sensing alternator voltage above battery voltage. In any case 10 amps is certianly not what any type of diode would be rated as. They all are rated by the voltage drop and that should be from fractions of a volt to 3ish volts.
50 watts at 14.4 volts is 3.47 amps in full sun with the panel perpendicular to the sun. I'd take half that value for 5 hours a day due to the sun angle not being perpendicular ever and more than 45 degrees most of the time+ clouds and shading by boat parts. that leaves 1.73 amps * 5 hours= 8.6 Ah each sunny day. since she is on a mooring and every day is not sunny I'd take half that value or 4.3 Ah as a planning value. If you only leave the anchor light on (photocell switch??) and it draws 1 amp for 12 hours=12 Ah you will not actually be charging the batteries and they will go completely dead in around 17 days (0 state of charge)
You really need to do a energy assessment to balance loads-production-storage. As a start point we would need all the loads (amps) and how long they are on each day.
As a starting point a 12 Ah drain will need (12 Ah/5 hours=) 2.4 of real production not considering charging and discharging losses..... and a lot of other stuff. That means 4.8 amps of panel production or a panel of (14.4*4.8=) at least 69 watts. Assumes a 1 amp anchor light though so if you go LED a 50 watt panel MAY work. it all depends on what you leave running and how you use the boat.
 

weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
The poblem is that this device requires ignition activation in order for solar or such to work properly. IIRC they call it an ignition ground that allows a solar controller to see voltage on the input stud. Most modern battery chargers, alternators, wind and solar controllers need to see a voltage in order to turn on. Diode isolators do not provide for this but some mosfet units do. The problem is you really don't want it "on" all the time at least that is what I was told when I contacted the manufacturer about this issue a few years ago. BTW I don't believe it is Christec that makes them, it is some Dutch company IIRC and Christec and some other private label them........

You can try the IG feature and measure the standby draw on the neg wire and monitor the heat of the unit but I would use caution as they only wanted it on when ignition is on for an alternator..

For the solar you could simply wire it to the house bank and leave the alt connected to the isolator. Engine batt would only be charged by alt but with a 50W panel you don't have all that much to work with anyway... On another note 160Ah's is pretty light if you plan to do overnights or ever use the fridge...
The 160AH house bank is stock and I'm primarily day sailing and maybe a few races. I'm not looking to redesign the whole electrical system just yet. I wasn't even going to add solar until I saw a previous thread here on those cheap, flexible renogy panels which I don't even have to mount permanently it seems.

FWIW, morningstar makes the "sunsaver duo" which has two outputs. The basic mode is 90% current to the house battery and 10% to the engine battery. When the house gets full, the current is diverted to the engine battery. I believe you can customize those ratios too. I know I'm not working with too much juice here though.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
It really does matter how you wire it though. The charge controller voltage sensing wire (can be a seperate wire or the positive feed to the "batteries/orher appliances" has to see battery voltage and not soem reduced voltage due to diodes or transistors (MS indicated that is is the transistor type BTW but there is still a voltage drop across it). I'd take MS recommendation and just connect it directly to the house battery and don't worry about the start.
You seriously need to consider getting more storage though. 80 Ah of house is not going to survive long if you run the reefer. The deep discharges the reefer will cause over only a day of sailing will make battery replacement a yearly thing. batteries DO NOT like to be discharged below 50%. that means you really only have 40 Ah of house bank. if you have a 5 amp load that gets consumed in 8 hours. Not much of a weekend sail if you don't have cold beer!!!!
 

weinie

.
Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
It really does matter how you wire it though. The charge controller voltage sensing wire (can be a seperate wire or the positive feed to the "batteries/orher appliances" has to see battery voltage and not soem reduced voltage due to diodes or transistors (MS indicated that is is the transistor type BTW but there is still a voltage drop across it). I'd take MS recommendation and just connect it directly to the house battery and don't worry about the start.
You seriously need to consider getting more storage though. 80 Ah of house is not going to survive long if you run the reefer. The deep discharges the reefer will cause over only a day of sailing will make battery replacement a yearly thing. batteries DO NOT like to be discharged below 50%. that means you really only have 40 Ah of house bank. if you have a 5 amp load that gets consumed in 8 hours. Not much of a weekend sail if you don't have cold beer!!!!
I know the fridge isn't going to be able to be run with the batteries I have now. But at this point, I'm not looking to have a floating condo.
They have this cooler for $300 bucks called the YETI. They say it works great for several days at a time. For that price, it should keep beers at absolute zero ! Still, its simpler than upgrading the batteries and alternator, adding a fancy solar installation etc etc.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
OK, but if you wire the voltage sense wire to the wrong side of the iso device the batteries will see a lower than needed voltage and not get much charge.
good luck