Batteries and power in general

[BobM]

Forgive me if this brings up a lot of stuff that has already been said. Lost my house battery, an Interstate car sized battery. I apparently left it on during the winter and it drained to zero and now won't hold a charge. It was only two years old max. Bummer. The other battery is typically just used for starting and is a matching interstate to the dead one(SRM-27's I believe), which are a hybrid cranking/deep cycle battery.

Anyway...I have to replace it and need to improve the system, likely by adding a small solar panel (boat is 100% at a mooring and usually just day sailed with a few overnights). That worked well on my old boat to keep the batteries topped off. The boat has a battery charger, but is never at the dock long.

I am also thinking about whether a more significant change for the house battery is in order. I know many folks use golf cart batteries, but I really don't know if I have room for one on my 9.2A. The battery space is pretty tight.

Thoughts and recommendations on battery brands / sizes, etc... are appreciated.

 

[Don S/V ILLusion]

You have probably heard this before Bob but it bears repeating -
First, figure out what you power requirements are - typically that required to maintain the boat electrical systems operating until the next charge (by whatever means, alternator, solar, etc.). Next, based on your expected powwr requirements, figure out how to replace those amp-hrs, ie., what size charging system you need.

Once you know what your electrical needs are, everything else follows in progression - alternator size, solar panel(s) size, what type batteries, etc...

 

[Ron20324]

You will want to get a deep-cycle battery for the house. Theory has it, if you only have one 12-volt, you should not use 2, 6-volts. If one 6 dies you have no power anyway, so may as well stick with one 12. If you have 2 or more 12s, going with 6-s is a doable idea....The small solar is a good idea.

 

[sailingdog]

I'd highly recommend you do at least a rough electrical budget of your typical electrical usage. Doing one for while under sail and one for while at anchor is probably a good idea. Take the higher electrical budget and add 30-50% to it for future expansion, and then double that number to give you a rough house bank size.

Your battery charging systems—alternator, passive solar/wind, shorepower, etc, should all be based on the size of the battery bank you have. The house bank is the one that is most important, as the loads and use of a proper starting bank are minimal, and the starting bank can be kept charged up by using an echo charger, duo charger or battery combiner off the house bank.

I've written a basic primer on Solar Power on Boats that deals with the sizing of the solar panel setup and such that you might also want to read. Getting a small 10-25 watt solar panel might have prevented this problem from occurring in the first place.

 

[BobM]

Usage is really minimal now and typically. Historically, the biggest issue I had on my last boat was the battery would run down pretty far if I had the running lights on for even a half hour. I haven't had this boat long enough to work out whether or not a single house battery will be a problem. I think I will just replace the battery with the biggest capacity I can get in the same size and get a 5-10 W solar panel. I just don't use that much power and the boat usually sits in the sun for a week between use.

 

[sailaway78]

Kind of Surprised

I'm kind of surprised that no one has mentioned what you have turned on, while on the mooring. While the energy budget is a very good thing to do, you also need to be aware of the power usage while on the mooring and not on the boat. If you think you have no power consumption when moored, you may not be correct. For example, a stereo with a clock and memory that has a constant hot circuit is a small but constant draw. Bilge pump, if it cycles very much is a fairly large power drain. If you happen to have one of the pumps that cycles every few minutes and checks for water is even more. If you have no power usage while on the mooring, then a 10 watt solar panel will probably be enough to keep the battery topped off and hot. BUT, while a 10 watt panel will keep the battery topped off, it is not enough to replace any energy draw you may have. I would also like to add that if you had a battery going down after a half hour of runnning lights on, you either have a shot battery, or a serious wiring problem somewhere.

 

[Don S/V ILLusion]

I would also like to add that if you had a battery going down after a half hour of runnning lights on, you either have a shot battery, or a serious wiring problem somewhere.

Good point worth repeating. No charged battery should suffer any effect with short intervals of running light use. Methinks you have a battery issue rather than anything else.

 

[zeehag]

car batteries and combination deep cycle/crankers do not last any time at all as house batteries----if you are able try to get a deep cycle instead of a car battery--car batteries and combo ones have only lasted less than 2 yrs in my experience--back in my small boat -any battery will do-days..ps--golf csrt batteries are awesome---you will love them--they last a long time--mine are alll now 5yrs old and still strong--solar rocks----you will do well that way...gooood luck and fair winds~~~~~~_/)~~~~~

 

[BobM]

Thanks all. The running light issue was on my old boat and the battery was rather old. The current bilge pump has a float switch, but I plan to move it higher up in the bilge and mount a smaller, sacraficial automatic 500 gpm bilge pump (I'd rather lose a $50 pump than a $200 pump every few years) at some point. I could just use a switch on it too.

Read your primer Sailingdog. Informative, as always. I am leaning towards the upper end of the range (perhaps 20 watts), but mounting it might be a headache.

 

[sailingdog]

A 20 Watt panel is probably small enough that you could mount it on the sliding companionway hatch on your boat.

Thanks all. The running light issue was on my old boat and the battery was rather old. The current bilge pump has a float switch, but I plan to move it higher up in the bilge and mount a smaller, sacraficial automatic 500 gpm bilge pump (I'd rather lose a $50 pump than a $200 pump every few years) at some point. I could just use a switch on it too.

Read your primer Sailingdog. Informative, as always. I am leaning towards the upper end of the range (perhaps 20 watts), but mounting it might be a headache.

 

[sailaway78]

Mounting small solar panel

Some friends of mine uses a small solar panel to keep the batteries up when not at the boat. They have no power at their dock, so need something. Think they have a 15 watt panel, or something close. What they did was mount some suction cups on the panel, and when they leave the boat, stick it on the cabin top. When on the boat they just pull it off and put it away somwhere. I wouldn't think it would be worth the hassle of permanently mounting a solar panel that small. Drilling holes and running wire for 15 or 20 watts just isnt worth it.

 

[BobM]

NNE, something like that sounds good. I have a 12V plug in the cockpit already so long as it has a one way resistor in it I should be good. I have a cheap charge controller, but have never used it. Don't think I need one if I go small right?

 

[sailaway78]

No need

I wouldn't think you would need a controller for a panel in the 15 to 20 watt size. Thats only a little over an amp. under ideal circumstances. Anything over this size and it might be a wise idea. I have two controllers, on 300 watts of solar. One of them is on a 65 watt panel, and is one of the cheap kind that dumps load when batteries fully charged. I have this one wired direct to the house bank, and the overload dump going to the start/emergency battery. Works fine, and keeps the start battery fullly charged.

 

[HEINZIR]

My sailing habits are similar to yours: mostly day sailing with an occasional overnight. My boat is on a mooring also. The primary current draw is the Davis anchor light that comes on automatically every night and shuts off every morning whether I am on the boat or not. I always have the depth sounder and the VHF on when I take her out (3-4 times a week.) I have a 10w panel mounted on my foredeck hatch. It is not the ideal mounting place for efficiency but it works to keep the Optima battery topped up. This is my second season with this arrangement, based on advice from SD and others on SBO and Sailnet. So far so good. I had used a 5w panel with a Walmart deep-cycle battery previously but the battery never lasted more than 2 years.

I probably don't need the sophisticated charge controller with a panel this small but I got a good deal on it on ebay. I'm kind of a gadget junkie. I also found the LED meters for cheap on ebay. The top one monitors battery voltage, the middle reads current out from the battery, the bottom one measures current from the solar panel. I only turn them on when I want to take a reading.

 

[delstanton]

Even with a good quality deep-cycle lead-acid battery if you routinely use more than 20% to 30% of its amp-hour capacity you will seriously reduce its cycle life. So when figuring battery size versus expected draw in amp-hours between charges take this into account.

It is as if your car had a 100 gal gas tank but to drive economically you can only use the top 20 or 30 gallons of that 100 gallon fuel load you are carrying.

Del Stanton

 

[BobM]

I bought a replacement battery and am scouring ebay for a solar panel. Thanks everyone.