440AH Not Enough ?

[Mark Johnson]

Originally Posted by reiner

We bought a 40ft Challenger not long ago and I replaced the two house batteries with two12v 220AH VRLA Batteries thinking that should be plenty of power. We have about 200W of solar and in the marina a 30A smart charger is keeping the batteries full. We have 2 fridges running most at the time.
First time we went out over night the batteries went down to about 50% capacity and down to about 12.6 Volt.
I really thought 440AH should be plenty of power but maybe not?
What setup do most of you have reg batteries and solars?

Thanks
Reiner

Imo... you need twice the solar panels, a much more efficient (like 40 AH of use / day) boat, equip your boat with 100 less AH in batteries, cycle them < 20%, and take only the gadgets and comforts that you really need. You will spend more time cruising, diving, and seeing the sights... with less time stuck near services repairing your boat.

We covered tens of thousands of miles, and lived aboard for over 12 years, with thousands of nights on the hook. This was with RADAR, watermaker, refrigeration, computer nav, and a truly comfortable lifestyle. It can be done, simply and efficiently if one chooses that route.

For the curious about how... Read my past posts, OR listen to the explanation in "Conversations with Jim Brown".

Fair winds,
M.

[nitpik]

I don't recommend adding diodes in the solar panel circuit to prevent night time feed-back, draining the batteries. Each diode costs you 0.6V, decreasing the efficiency of your panel. If your regulator takes it's power from the panels, it switches off at dusk, and thus prevents the night-time drain anyway. I believe most regulators do this, making those diodes redundant energy wasters.

[denverd0n]

Originally Posted by reiner

A friend suggested to see if I got diodes in the solar panels. He seems to think they could help discharging the batteries at night.
The panels are quiet old, maybe that is where the problem is.

Do you have a charge controller between the batteries and the solar panels? If so, that should be preventing the panels from discharging the batteries. If the panels are wired directly to the batteries then, yes, it is possible they are discharging the batteries. If that's the case, get yourself a good charge controller, not just diodes.

And, yeah, I have to agree with those who said that if your voltmeter is showing over 13 volts on batteries that have been sitting for a day or more then there is definitely something wrong with your voltmeter.

[sigmasailor]

Originally Posted by GordMay

Although I agree with the previous posters, I'd note that 2 fridges can be very "spendy" on electricity.
ie: 5 or 6 Amps each x 2 fridges x 16 hours = 160 - 192 Amp/Hrs.

True if you leave the fridge overnight with the door open. With door closed and properly insulated they do not run 24/24 hours or even 16/24 hours. I never really checked this but is 4-6/24 a good average run time?

[capn_billl]

Originally Posted by sigmasailor

True if you leave the fridge overnight with the door open. With door closed and properly insulated they do not run 24/24 hours or even 16/24 hours. I never really checked this but is 4-6/24 a good average run time?

Depends on how old, efficient, well insulated the fridge. Mine runs closer to 40-50% duty cycle...some of that may be from midnight snacks.

[colemj]

Depends where you are, how big the box is and how much you use it. In the sweltering tropics, our exceptionally insulated 4cft freezer with spillover to 6cft reefer used throughout the day runs 12hr/day. It ran 9hrs/day in the Bahamas and 4hrs/day in the Northeast US.

Mark

[kaimusailing]

Ahoy Reiner,
You have about the same AH in batteries and wattage in solar panels as I do. The rule of thumb is to have 3X the available charging AH per day in battery capacity, so we both have about twice as much battery as what would be optimum for the amount of solar charge capacity. The charge capacity should equal the load, i.e. you would only want to draw down the batteries equal to the amount of solar power. You should get one of those battery specific gravity testers, they are not expensive and give an accurate indication of the health of the battery. I've added a wind generator to help top up the batteries, also picked up 90 more watts of solar to be incorporated in a hard bimini, a future project. The main thing is to match your usage to the amount of charge your getting, otherwise start up the generator. Refrigeration can eat up a lot of AH.

[btrayfors]

Guys....

Reiner said in his first post that he had "VRLA" batteries. That means gelled or AGM. Either of these can display resting voltage considerably higher than flooded batteries, even sitting in your basement for a week or two after charging.

While "over 13 volts" may seem high, VRLA batteries can certainly come close to that, whereas flooded batteries won't stay above about 12.7VDC.

Example: I have two 6V gelled golf cart batteries sitting in my basement workshop right now. These batteries are 15 years old! They've been used in battery tests here for several years, after spending their first 10 years on a sailboat. They were last charged two weeks ago. And, right now, they measure 13.166VDC (on a calibrated Fluke 189 meter).

So, Reiner, don't sweat the multimeter, but it may be a good idea to check with another one anyway.

Bill

[Stu Jackson]

Originally Posted by reiner

I read too that new batteries need too "run in" to hold charge better.
The new ones only had one charge.

"Breaking In" New Wet Cell Batteries

[Bash]

Originally Posted by reiner

What setup do most of you have reg batteries and solars?

I've got 420 AH in AGM batteries charged by 260 watts of solar and 200 watts of wind. I run two refrigeration compressors. My system never really gets below 50% charge, and seldom gets below 75%.

[reiner]

Thanks everybody for all your replies. Since last time I bought a new Fluke multimeter and just checked the voltage again. It is still 13.05 volt being disconnected for weeks now.
Like Bill said VRLA Batteries can do that.
I found that one of the two fridges might have a problem, since we turned it off we get good milage out of the system as it is.
Cheers
Reiner