Dual Batteries good idea or overkill?

[Thorne]

Re: Dual Batteries good idea or overkill?

Once again I am seeking advice by joining a current thread. I am a new boater/boat owner. I've been getting the boat out on many cooler days to practice my maneuvering before the lake gets really crowded this summer. My wife and I got out boat primarily for summertime recreation with our friends that are boat owners on one of our local lakes.

We own a 2003 Larson SEI 190 Ski n Fish that we purchased from the original owner. When we were looking at the boat the battery would not start the engine and the prior owner bought and installed a new deep cycle battery. We have had no trouble starting the boat with this battery. We have made some alterations to the boat, specifically installing a new stereo system to upgrade the original tape deck unit. We put in an Alpine IDA-x100M head unit, an Alpine PDX-4.100M amp, and 2 Rockford Fosgate M262 6.5 speakers to replace the original speakers. The boat didn't have an amp to start with.

I know that we are going to need a good bit of power to keep the tunes going all day on the lake. Currently the head unit is wired to the battery used to crank the engine. I think all the other electrical applications are also powered by this battery except the trolling motor and now the amp.

The boat is a bowrider with step-through windshield. There are two chairs and a bench seat in the passenger area. The boat came with two batteries, one in the stern for the engine and one under the bench seat on the starboard side. The trolling motor was the only thing hooked up to the battery under the bench seat when we purchased the boat. I have two additional deep cycle marine batteries that my wife and I use to power satellite tv through an inverter when we tailgate at football games. I think that I will replace the battery under the bench seat with the 2 I already own because they are of the same age, make, model, etc.

I guess what I am asking is should I rerout the head unit to also run off these two batteries? I will not have the trolling motor on the boat on the days that we are not fishing. I have two objectives I suppose: 1.) that the boat will start and get us back to the ramp; and 2.) to have tunes all day as we want them.

I guess a second question that I have is whether I should tie the two batteries together under the seat so that they are used equally or should I just run them one at a time and keep one in reserve?

Thanks for any advice you care to share.

 

[John_S]

Re: Dual Batteries good idea or overkill?

Thorne,

I do not recommend running two batteries in parrellel. This usually leads to problems.

The quick and easy solution for you, is to hook your stereo to the trolling motor battery. If you drain that battery from just the stereo, it will not impact starting. If you have blasted the tunes all day long to kill a decent deep-cycle, I suspect there might be some people on your lake ready to torepedo you. If memory serves, a typical deep-cycle would be about 3 hours @ 25A discharge rate or 75Ahours. I would expect a typical stereo to be around 1-2Ah, but check your manuals.

If you want to add another battery, do it as a spare for the starter, and with a switch, aka what this thread is about.

 

[Blue Crabber]

Re: Dual Batteries good idea or overkill?

I have got 2 on the boat plus I always carry a fully charged jump start unit. I never want to be caught out on the water with a dead battery. As already mentioned, if the weather changes quickly and you can't start the engine, you could be in danger very quickly. But then again, sometimes I go overkill, better safe than sorry though.

 

[mphy98]

Re: Dual Batteries good idea or overkill?

a lot of wierd things can happen on the water, a spare is always a good idea.

 

[Rancherlee]

Re: Dual Batteries good idea or overkill?

I run 2 and sometimes 3 batteries depend on what I'm going to be doing with the boat. The cheap setup is a Deep cycle as your secondary battery with all the accessories run off it and leave the starting batter for just the engine. Run a heavy duty switch or 12v circut breaker (40 amp 12v circut breakers are ~5-10$) and 8 gauge wire from the starting to the secondard battery and remember to shut the switch off when starting. Deep cycle do not charge fast unless there is a HUGE difference in voltage so a 8 gauge wire and 30-40amp breaker will suffice. A Deep cycle will charge at ~10amps or less with a 14.4v source charging it (aka alternator). Or you can step up a little and spend some cash on an isolator.

 

[Merrymeeting]

Re: Dual Batteries good idea or overkill?

My boat came with a single battery set-up but I plan to add another battery. I like the idea of having a battery just for the starter. I plan to drop anchor and sit around listening to the radio quite a bit and am afraid that I would drain the battery. If I dont add a second battery I plan to get an inexpensive lawn mower battery to store in the boat just in case if I ever need it. I would hate to be stranded and have to get a tow just because of the battery. A lawn batter would be plenty of power to start the outboard and doesnt have the weight of an additional marine battery.

 

[Thorne]

Re: Dual Batteries good idea or overkill?

Thanks for all of the advice. I think I will move the head unit connections to the trolling battery and go that route. Then I will just keep a spare battery charged up for back-up on the tunes and leave my starting battery to do its job.

 

[Eddie P]

Re: Dual Batteries good idea or overkill?

I've upgraded to a dual battery system myself. I have a Stingray 220DS - sort of typical sporty family boat with extra electronic components, that can kill a starting battery quickly.

The original configuration was a single cranking battery. The second battery installed was a very good quality, proper marine deep cycle battery.

This season, after deciding my cranking battery was getting old and not holding it's voltage as well, I replaced it with another deep cycle battery of 700 CCA's and 800 MCA's. I hope the decision to go with two deep cycle batteries vs. a single deep cycle and one cranking battery does not cause issues, but based on my experience with my deep cycle last season, it was getting excellent re-charge out on the water as I use a battery manager at home to monitor waht I used and what was put back in to each battery. It seems the alternator was doing a good charge of keeping everything happy.

Anyone else have ideas on two deep cycles vs. one and a cranking battery?

 

[bruceb58]

Re: Dual Batteries good idea or overkill?

I have two deep cycles in my boat and I am starting a 454 with them. Now saying that, my deep cycles are the ones from Costco and, although they say they are deep-cycle, they are probably more of a hybrid.

 

[sheltonchris1]

Re: Dual Batteries good idea or overkill?

Could someone explain exactly how to wire up two batteries? I would like to know what switch I should get and how to wire the batteries into the switch etc. Thanks.

 

[Eddie P]

Re: Dual Batteries good idea or overkill?

I have two deep cycles in my boat and I am starting a 454 with them. Now saying that, my deep cycles are the ones from Costco and, although they say they are deep-cycle, they are probably more of a hybrid.

Hey Bruce, how's it going? Glad to see your batt setup works well. The new Deep Cycle I bought is also a Costco buy. I felt good about that since it was a new battery, and my other Deep Cylce is a nice expensive quality unit. My engine is a V8 280 HP, I think that's a big block, so it probably needs more juice to start. I've noticed since I put the new batt in I've had a case of "turn the key, hear the oil psi horn, and get no crank". I held the key in the start position for about three seconds - nothing - and then all the sudden the engine starts cranking and it starts with no issue. With the old cranking battery, the starter always seemed to engage as soon as the key was turned. The battery selector was on "both" - odd as both batteries have cranking amps in parallel of about 1400 amps, minus electrical losses in the longer battery cables from #2 battery of course.

The most obvious thought is that the cranking amps might be a little low on a set of deep cycle batteries that have also not been top charged in a few weeks. I do have an electronic battery manager/charger and I'll be sure to start the next rip topped off, and then test again. I'll probably also bring a jump start mobile pack along for the next couple trips just in case, in spite of pre-charging. Side note, after this last boat session I docked up and re-started the engine before putting it away, and the starter cranked over immediately and the engine of course started right up. Not surprising though, the batteries were freshly charged from the previous motoring and the engine oil was nice and hot, making easy work of the cranking.

Just out of curiosity, when a starter begins to go, what are the typical signs, if any? Does it just not turn over the engine one day? Or does it start to draw a lot of amperage to crank the engine before it burns itself out? ie - masking the real situation by showing signs of not enough cranking amps from the batteries?

Sheltonchris - The switch I used has all the wiring diagrams in the kit. If you go to WestMarine or a similar Marine store you will see a few types. Depending on your boat, most guys use the rotating selector switch that allows you to select no batteries, #1, #2 or both in parallel. To be honest I bought the equipment and had a Marine Repair facility install it simply because I wanted the dual battery upgrade for the season last year and it was the first work done on my boat after buying it. I did not want to screw up the electric system right out of the shoot being a new boat owner. Looking at it now, and after having the boat for the second season, I'm pretty sure I could do it again on my own - but I'm happy I had it done professionally at the time.

 

[Eddie P]

Re: Dual Batteries good idea or overkill?

I've noticed since I put the new batt in I've had a case of "turn the key, hear the oil psi horn, and get no crank". I held the key in the start position for about three seconds - nothing - and then all the sudden the engine starts cranking and it starts with no issue.

Must have been a case of new battery itis. It has worked well in the couple times I've boated, since. I did top off the battery when I got home and a few days later it was perfectly fine.

 

[flargin]

Re: Dual Batteries good idea or overkill?

Chris or anyone else: what about Dual Purpose Batteries? Are they damaged by deep discharged? Would a Dual Purpose Battery be damaged by using a portable Jump start?

Duals can handle deeper discharge, but cannot supply full starting cranking power, kinda not great at either, but not bad if you have a smaller, less demanding setup. (small motor, few electronics)

 

[hubes58]

Re: Dual Batteries good idea or overkill?

I went out last weekend, dumped the boat in the launch and had my bro start it up..... click click....good thing I had a back up! oops that was dead... use the deep cycle the (for trolling motor) the rest of the day.

Bought three new batteries the next day ( they came with the boat 2+ years ago and the boat is 5 years old) Now I have dual deep cycles, and 2 cranking batteries, Now switch, but after reading a few post, I think it sounds much better than crawling down and trying to swap cables while 10 people are waiting to launch there boats!

 

[fishing1]

Re: Dual Batteries good idea or overkill?

For the gentleman that has one battery for his OB in one compartment, and the two deep cycles in another. I always always keep a pair of jumper cables in the boat.

 

[Eddie P]

Re: Dual Batteries good idea or overkill?

Yeah, I have to admit I take a bit of comfort in having that portable battery jumper with cables, in case I need some more cranking amps. And if it can help someone else stranded on the beach some day so be it, as well.

When I eventually replace one of my two on board batteries, I'll go back to the single deep cycle battery and single cranking battery configuration hooked into the battery master switch. But for now the two deep cycles are working adequately.

 

[Thajeffski]

Re: Dual Batteries good idea or overkill?

I installed the ADD a battery system from blue sea systems..........absolutely worth the effort and price.....

Before I was worried that might boat might not start after the radio on all day.

Now I charge my laptop/phone/ipod and run the radio at the same time, all day........and the battery that is "reserved" by the system for starting always comes through.

 

[JimmyOOOOO]

Re: Dual Batteries good idea or overkill?

I actually don't have a dual bat setup yet, but I will soon!

 

[wingless]

Re: Dual Batteries good idea or overkill?

The factory built my boat w/ five group 27 batteries; port engine; starboard engine and gen.

The one gen battery is dedicated to that only.

One two-battery bank is connected to the house, the other to the helm electronics.

I've upgraded to six group 31 batteries, with a rotary switch to short the two port and three starboard on-demand. I usually leave them shorted for maximum run-time on-hook.

My largest load is the 'fridge, drawing about 9A, almost continuous. The five house batteries hold this load for about 4? days. The UPS / inverter is second at ~0A standby / 3A idle / 5A powering the salon TV/DVD. That will grow as I expand the usage to future AC loads.

My backup is the gen, that will power the on-board Charles 50A charger. This initially shows about 60A output to bring-up a discharged bank.

I've also got jumper cables, if I need to get going in a hurry.

Back-up is essential. It is too easy to have a bad battery, or to deplete capacity, then the boat don't go.

The best way to maximize life is to not use the batteries and keep them on a float charge. Each discharge / charge cycle decreases the storage capacity, shortening the life. Time also shortens life.

Also, the electrolyte in flooded-cell batteries must be maintained, especially in warm weather.

Also, idle batteries lose about 10% charge per month, more in warmer temperatures. Batteries should not be stored below about 50% state-of-charge to avoid permanent damage called sulfation. The best storage is to keep them on a float charge continuously.

The best way to charge a battery is to use a properly configured smart charger, for at least 24 hours. A battery will only be close to fully charged if the duration is less. It is better for the battery to be fully charged, not just close.

Batteries connected in parallel should be matched, the same capacity, manufacturer and date code is best. When they are off, one will supply more current and one will accept more charge than the other. That isn't good for either battery and will shorten life and provide less capacity.

 

[Eddie P]

Re: Dual Batteries good idea or overkill?

Batteries connected in parallel should be matched, the same capacity, manufacturer and date code is best. When they are off, one will supply more current and one will accept more charge than the other. That isn't good for either battery and will shorten life and provide less capacity.

That's a good point.

I always run accessories off a single battery when stopped. I often start on a parallel configuration. I used to charge on #1 or #2 for each time after the start, while underway - but I've gotten lazy lately and left the selector on both until I stop again where I'll typically use my #2 for accessories as it's more of a true deep cycle battery.

Probably better to stay separate for charging as each of my batteries are certainly not matched.