Some battery info

[kenai]

Stolen from Boat US pages

Don Casey Tip #30

Deep-Cycle Batteries



A marine starting battery is essentially an automotive battery--sometimes “ruggedized”, sometimes not. Like an automotive battery, a marine starting battery is designed to start the engine(s). After that, the battery is being continuously charged. STARTING BATTERIES ARE NOT DESIGNED TO BE DISCHARGED—PERIOD. So can you run the electrical equipment on your boat from a starting battery? If you run it only when the engine is running, the answer is yes. Power drawn by appliances is concurrently replaced by the alternator, so the battery stays fully charged.

If, however, you expect to operate electrical equipment when the engine is NOT running, you need a deep-cycle battery. Deep-cycle batteries can be discharged to about 50% of their capacity without damage. In other words, you can expect a 100 amp-hour battery to supply around 50 amp-hours of power between charge cycles without suffering damaging. Provided it has sufficient cranking amps, a deep-cycle battery can also serve as the starting battery, but most boaters elect to have a dedicated starting battery so discharging the “house” battery cannot leave them unable to start the engine.

A dual-purpose battery has appeal for those who wish to avoid the complication of multiple batteries. Something of a hybrid, this type of battery typically is more starting battery than deep-cycle, but it will tolerate modest discharge without damage. If you only want to run the stereo and maybe a couple of lights when the engine is silent, this can be a good choice.

[ET]

I find this statement very interesting...

"Provided it has sufficient cranking amps, a deep-cycle battery can also serve as the starting battery"

I have a small 70hp Yamaha so the cranking amps required is relatively low. Right now, I am using dual-purpose batteries, but I think I will purchase true deep-cycle replacements. With electric downriggers, shrimp pot puller and other accessories, I think deep-cycle batteries are a better choice for me.

[Spindrifter]

Hmm....I have always ran 2 starting batteries on my Trophy. I just alternate between the 2 occasionally. I have the fish finder, cabin and lights hooked to the output of my battery switch. Maybe I should change out one battery to a dual purpose or a deep cycle and hook up the acc. there and install another switch? I guess I just liked having the other starting battery as extra insurance

[skein]

Hmmmm....

I'm a pretty big fan of BoatUS and feel that they offer a lot of really valuable tips, but this one makes me feel as if we have to treat our batteries as if they were eggs. I dunno.

I just replaced my batteries, not because they were dead or dying, but because they were three years old and I don't want any surprises 40+ miles out. I asked my RV guy what I should get for my boat and he told me the best was the jell-cell, mainly because of the pounding most boat batteries get. Since he didn't sell them, and because he's been faithful in our dealings over the past 15 years, I bought a pair of his best Interstates. They are deep cycle, but seem to start my OUTBOARD quite nicely.

One more thing. I tend to leave my motor running out there, even on the drift, because I somehow think that if my motor is running, I have a better chance of getting back to shore. I use very little fuel on idle, so it's not a big deal for me. But... that means I'm throwing a constant charge into the batteries at all times. Maybe that has made the difference.

Oh, one more thing. I carry an extra battery along, not hooked up to anything. Just a spare.

I just have trouble believing our batteries are that "fragile."

Skein

[8knots]

One of the reasons long range cruising boats use golf cart or fork lift batteries is because they rely on a large battery bank for when they are on the hook. The run them down to 50% and then charge them back up....a lot.

I don't know that the electronics on a smaller boat like the ones most of us use will draw the starting batteries down that much and we keep our engines running a lot. I could see them being seriously drawn down if you are using a wash down pump and live bait pump and using your electronics on a live bait stop with engines turned off.

Quality, deep cycle batteries will start an engine just fine and give you the security of being able to run it down to 50% without wearing it out like you would a starting battery with thinner plates.

Empire batteries off of Bonita in Tigard has high quality batteries for very competitive prices. I buy 5 8D's at a time and have used them for 10 years with high satisfaction.

[ron m]

I have two batteries, unlike Jim I don't leave my motor running while driftng, but mostly have only the FF, GPS, and radio on the battery while fishing. so far haven't had a problem, may get one deep cycle and one cranking battery when I replace them.

I recently got an electric pot puller and it does better if I raise the idle on the motor while pulling pots, so maybe should be running on a deep cycle battery while pulling pots. Carrying a spare would be good, but would need to make sure it was fully charged for each trip. I guess a spare should be a cranking battery, right?

ron m

[Spindrifter]

I also thought of getting one of those battery buddies instead of a spare. Easier to lug around and will give you the necessary "jump" when needed. Just a thought....

[skein]

Those jump-start units are pretty handy to have, and I remember Fish Assassin getting a guy started with one - waaaay offshore. But I don't want to be without a spare battery. I'm thinking of the time when I not only need starting power, but sustained current to run items like radios and radar and lights and maybe even a bilge pump.

I think of it as a 40lb insurance policy. :grin:

Skein

[Something Good]

Since having battery problems out on the water about 10 years ago due to my brother leaving the ignition key on I carry two batteries and replace one every year. This way I always have one new battery in the boat and the other is less than two years old. I use the combo batteries and haven't had a problem. I run the FF, GPS and radio. Will be running the radar if it's foggy but I always at least have the kicker going.

[Hoghunter]

I would agree with the statement that starting batteries are for that only and aren't built to be discharged w/o the engine running. I would bet that you would reduce their life by 50 to 60% doing that.
For the last 15 years I've used the following system and have never once been dead on the water: I use Rolls Surrette deep cycle for my house bank (500 amp hours which equates to 250 useable hours) and two Deep Cycle starting batteries (one for each outboard motor). I have the whole system wired with three different switches to where I could switch either Deep Cycle start battery to the other motor if one fails and if both failed I could flip switch number three and start both motors from the house bank. In an emergency I can also switch the two Deep Cycle starts to run power required by the house bank. It was a complicated system to wire but when finished it was worth it. I've never had to use it yet but if I ever do I have failure one of the banks I have confidence that I'll get home on one of the other two. The deep cycle Rolls batteries are spendy but they last about 7 to 9 years. That's a heck of a life cycle.

[Something Good]

One more note about batteries. An alternator is not designed to recharge a battery but rather to maintain a battery. If you discharge a battery you must recharge it with a battery charger to regain a full charge.

[8knots]

Not sure, but if your alternator is capable of putting more amps into the battery than are being used then it would be getting charged. That's why big boats, with big battery banks, have big, high output alternators to charge and replace lost amps underway.

[Onokai]

(battery buddies)
I never go offshore without one, It will jump start any motor.
Just ordered the 2 largest optima's(deep cycle) made-D31M to replace my older wet cells which are aged. I will put the stunt switch (combiner) in also so it keeps them booth charged but one at a time. My perko days are numbered. Mark

[Spindrifter]

I will put the stunt switch (combiner) in also so it keeps them booth charged but one at a time. My perko days are numbered.

Could you elaborate on what this item actually is and where to get one? I still use a Perko, but I'm open to a better alternative

[Nalu]

I have three batteries in my boat, all deep cycle. 2 group 24 tied in parallel and 1 group 27. These two banks are seperate, with two independent switched, one for house/port motor, one for starboard motor/miscellaneous.

Like Onokai, this will be the last year for the Perko switches. Next winter is the re-wire, and installaion of combiner/isolater.

Due to worry of galvanic corrosion in Depoe, I installed a solar charger that is mounted to the hard top. It won't bring a dead battery back, but I can definitely see the difference on my battery meter from when I leave the boat until I come back a few days later. It's also nice to look in the battery compartment and see the GREEN light that indicates the batteries have been fully charged by solar.

[Hoghunter]

Several points. First there are alternators that will charge large house deep cycle banks. However, they are made only for inboard motors. I'm referring to alternators made by Ample Power or Balmar here in Seattle. They make alternators that can put out up to 180 amps and more when running. When I had my sterndrive in my previous boat I had an Ample alternator that had no problem charging my large Rolls Surrette batteries when at idle let alone at speed.
I'm not sure how much I think of the combiner/isolator switches that are made and promoted by stores like West Marine etc. When I bought my new Grady two years ago I got the same recommendation from several marine electrical suppliers here in Seattle that I got years ago and that was stay with good quality plunger type switches or switches made by say Blue Sea. When I got my Grady it had two Perko switches and the first thing I did was take them out and replaced them with four Blue Sea switches.
The other factor that I think is critical is that you have a good digital Battery Monitor that will tell you state of charge, voltage, amps used etc. This gives you a much better read on your batteries than the volt meters that come installed in your boat. You can also use them (when combined say an inverter) or large alternator to control and regulate that state of charge that goes into your batteries.
Two wonderful sites that have lots of information about the do's and don't of battery management are www.amplepower.com and www.boatelectric.com. Both of these companies have been in business for many years serving the marine industry here in Seattle. Ample Power is loaded with good information on battery management.

[Onokai]

Here is another talk on the combiner
http://www.ifish.net/forum/showflat.php?...rue#Post1210491