Charging Battery

[hellosailor]

Solar IS expensive, there's no way around that. If you are going to be taking the battery home and back to recharge it, get an AGM battery so there's no problem with acid spilling.

You can expect that most solar panels will put out about four hours worth of their rated capacity, given a full day of sunlight. So if the panel is rated 25 watts--you may get 100 watt hours (about 7 amp-hours) of power on a sunny summer day. Make sure that if you do go solar, the panels are warranteed for marine and exterior use, otherwise they will be destroyed by water penetration. The cheap "keep the car charged" panels usually have to be kept sheltered, even rain will kill most of them.

[mawm]

The best advice I got when looking for a way to keep the batteries charged out on the water was that diesel is a lot cheaper than buying solar panels or wind chargers. I have 2x 80ah house batteries (which gives me about 60ah usable power) and a separate starter battery, my alternator is old and puts out 28amps (!!!). I run the engine (18hp - uses 1litre an hour) 2x a day for 1hr to cool the freezer and charge the batteries - but then I don't have a lot of electronics, just a gps/depth sounder, vhf and an auto tiller. I have put in LEDs on some lights, but have kept incandescent for the rest as they are much 'warmer'.

I guess that I make up the shortfall of amps at times when I'm motoring and at the marina I keep a trickle charger attached. It is cheap and works for me.

[sailingdog]

This is not necessarily true, since you have to account for the cost of maintenance and replacement of the diesel charging source. If you take those factors into account, solar and wind are both far more reasonable. Also, if you're cruising long-term, diesel charging sources have a problem of having finite fuel—which solar and wind charging systems do not. With solar and wind charging systems, you don't have to carry the fuel with you.

Originally Posted by mawm

The best advice I got when looking for a way to keep the batteries charged out on the water was that diesel is a lot cheaper than buying solar panels or wind chargers. I have 2x 80ah house batteries (which gives me about 60ah usable power) and a separate starter battery, my alternator is old and puts out 28amps (!!!). I run the engine (18hp - uses 1litre an hour) 2x a day for 1hr to cool the freezer and charge the batteries - but then I don't have a lot of electronics, just a gps/depth sounder, vhf and an auto tiller. I have put in LEDs on some lights, but have kept incandescent for the rest as they are much 'warmer'.

I guess that I make up the shortfall of amps at times when I'm motoring and at the marina I keep a trickle charger attached. It is cheap and works for me.

[netscheid]

I have another question, are there any small and possibly cheap meters or gauges that I could hook up to the battery to tell me how much power is left in it?

[mawm]

Sailingdog - if you are going cruising and are going to spend a lot of time (years) on the boat I agree. For th average 3weeks a year trip and a few longish weekends, I wouldn't bother to spend the extra money. I have to run the compressor for the fridge anyway.

Netscheid - a simple multimeter ($10 - 60) and a hygrometer to measure the specific gravity of your battery acid (from an auto shop - mine cost about $10)

[rugila]

Looking at Cam's lnk for the battery, I don't think an auto shop hygrometer would be of much use in measuring specific gravity of a sealed battery like that.

a hygrometer to measure the specific gravity of your battery acid (from an auto shop - mine cost about $10)

[sailingdog]

A solar panel will work pretty much year round with little maintenance or upkeep. A 25 Watt panel is less than $200, and can probably keep up with weekend usage if the battery bank is sized appropriately.

Originally Posted by mawm

Sailingdog - if you are going cruising and are going to spend a lot of time (years) on the boat I agree. For th average 3weeks a year trip and a few longish weekends, I wouldn't bother to spend the extra money. I have to run the compressor for the fridge anyway.

Netscheid - a simple multimeter ($10 - 60) and a hygrometer to measure the specific gravity of your battery acid (from an auto shop - mine cost about $10)

[SteveInMD]

Originally Posted by netscheid

I have another question, are there any small and possibly cheap meters or gauges that I could hook up to the battery to tell me how much power is left in it?

It's really hard to test a battery and tell how much charge it has in it. A hydrometer helps some, but it's messy (battery acid is nasty stuff) and as mentioned above, not useful with a sealed battery. Looking at resting voltage is also of limited use. The only way to have a good estimate of the charge state of a battery is, is to track how much charge you put into the battery and how much you take out. There are meter systems that do this quite nicely. Do a search for "Xantrex Link 10 Battery Bank Monitor". You don't usually see them 15 foot boats, but on the other hand I would think the installation would very simple. You would know your battery condition and exactly when it's time to recharge.

[Magic_Moments]

I have a little gizmo I think is made by Minn Kota that has 4 lights to give you an idea of the charge level. I think I got it at west marine for $10-15.

Some of the solutions you guys are making are a bit much for a 15 foot boat. I have a 6watt solar panel that I clamp on a rail that keeps the battery topped. I used to have a 6hp evinrude outboard with a charging wire that I ran to the battery. That assumes you will use the engine.

One other solution is to replace the anchor light with a LED that will cut its draw by 80-90% . I also have 5-LED lights from Costco that run on AAA batteries. They last a long time and are decent for reading. They can be stuck on with velcro or a screw.

[anthonyinnes]

Good suggestions above perhaps some more thoughts.
On our 23 foot sloop we have running and cabin lights and do ten daytrips far from power.
We have a battery charger for marina tie up.Its a 6 amp cheapy and brings up our two average car batteries up to the mark.Soemtimes we have had to put them into the car to charge them up on the way home because we wanted to hurry back out sailing.In shaky ports where we have to watch the crims do not steal the battery we have taken it on board and once or twice been glad of the extra.Push starts have happened for the car.
Potters would be small for a decent solar panel.A small generator solves my friend's problemns .He likes to take walks on the beach and leaves his generator running up on deck while he goes for a walk.It also keeps the scum from ripping off the boat when thay think someone is home.As the economy tightens you'll find they'll steal the cleats I am not paranoid but in the UK theft is major around the waterfront.The generator we have can run our waeco freezer,computer and charge the batteries ar the same timefor way less fuel than the big boat motor.I can lift it with without strain at 62 AND WHEN I GO OUT ON BIGGER BOATS i DO NOT HAVE TO WORRY ABOUT THEIR SYSTEM and most of them see the wisdom in having unlimited power .its an option and up on deck in a blow you have to strain to hear its running down below.I use earplugs around some boats as i like to sail not motor.With head lights for personal use,LED bulbs ,crank power and other wonders you can be simpler and more efficient.Stuff from LL Bean is great,cheaper than the marin suppliers and they mail order.Have fun
anthony innes