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We are (finally) taking delivery of our new M next week . I have ordered 2 Rolls group 27 batteries (starting/deep cycle). Going to install them with 3 (on/off) switches and a battery combiner for charging.

My thinking is typical 1 house and 1 starting. But be able to combine them (via switch) on rare occasion for extra house or starting needs.

Probably overkill, IMO. But rather have too much power than not enough.

This is our first boat with 2 batteries. No experience other than talking with other experienced boat owners.

Do you NEED 2....probably not for a lot of owners. We used our powerboat for 12 years with only one starting/deep cycle battery with no issues (did carry a portable jump starter last few years though). Never had a lot of demand other than a radio going for a few hours while anchored though.

I see no downside to having 2, other than weight.

Paul

Dimitri,
What I found, unless you have alot of current draw is 2 batteries seem
to work well for me, although I did find myself one time with both batteries
drained completely. I do not designate one as a starting battery, but would if a third battery is installed. I carry one of those self contained jump systems with a light and cigar lighter plugs built in. I just jump started the engine as I dreaded pull starting it. The carry type of jump system was from Harbor Freight, and really works like a champ! I stow it in the head all the way forward in that little cranny, and there if needed in a pinch. The light works well also, as I found out last weekend. I gotta trace down a problem with the electrical system right now, as the engine starts fine, but the rest of the electrics are out.....everything else!

Conservation is much less expensive then upgrades such as large solar panels. Their impact is minimal at best anyway! I do use a 5-watt model to keep the batteries up to snuff between trips though.

I also doubt I will go as elaborate as a monitoring system, but I am contemplating using an inverter and small microwave aboard. Again, if I run out of juice for starting, I just hook up the portable unit and it's good to go! I spent 2 weeks at Catalina Island last year with the anchor light illuminated and the GPS on anchor watch, and again only had to jump start once. I even assisted two power boats that required a jump start! I ran the engine for recharging for about a half hour at idle in the mornings, and that worked for me!

Another thing worth mentioning is to NEVER switch the Master switch over to any position while the motor is running. This is a sure way to fry your electronics on the engine in the charging circuit, due to surge!

Tom Root
2002 26X
Great White
San Diego

Dimitri:

I agree. My Suzi DF50 injected 4-stroke starts immediately regardless of how long since it last ran (might be 3 months or more). So I see no need for a separate starting battery IF you have no significant load, and/or don't forget to isolate it if you do, or one battery doesn't go bad unbeknownst to you, or you have hand-started your motor for practice.

Last year anchored off Key West, I had the two unidentified batteries that came with the boat, and forgot to turn the switch from Both to 1 and the Coleman thermodynamic cooler ran them both dead overnight. My friend had brought a portable backup kit and we started up with that.

Since then I installed three identical Lifeline AGM 105 AH batteries. Two in parallel serve as a house/starter bank, the third is connected via a Combiner 50 so it charges automatically and it is never used. I still have the Off-1-both-2 switch with the bank on 1 and the standby on 2. I have also installed the Xantrex Link 10 Monitor but have not yet connected it until I study the manual more.

If you use one battery for both house and starting and use a Combiner 50 for the standby to avoid forgetting the switch, you should be fine. You know how to figure your loads VS battery capacity. I got my Combiner 50 on ebay.

Edit: Just remembered that EFI engines need some power even for hand starting. So "stone-cold dead" may leave one dead in the water.

Jack O'Brien wrote:Dimitri:
forgot to turn the switch from Both to 1 and the Coleman thermodynamic cooler ran them both dead overnight.

This is the reason I am not going to use a 1 2 both switch. Just on/off for each and one (with removable key) to combine them if needed, so there will be no way for them both to go flat.

Paul

Howdy,

I only have one battery although I wold like to add a house battery. At the present time I have one of those jumper batteries that I always take along just in case I run down the battery and can't start my motor.

Beyond just the convenience of being abloe to start the motor in the event I suck my battery dry with lights etc over night, there is a safty reason. If I need my Marine VHF or other radio (CB) I can power it up with the spare battery in an emergency. I guess I am paranoid because I also have a portable handheld VHF. (Sometimes I even where both a belt and suspenders too).

I will take your word for it that a 50 HP is easy to start by hand as I have never tried. Perhaps I will give it a shot this spring just to see how easy it is to start that way.

Regards,
Nelson Thomas

I have 3 batteries all hooked together. The orignal battery plus 2 group 27s from Exide. low tech, lots of juice. If anchoring overhight, I might unhook one of the batteries for a reserve start battery in the morning.

I've never hand started my Tohatsu 50. Don;t you have to unbolt the recoil cover to hand start? Is this hard to do or a trivial couple of screws to undo?

I have two house batteries and last season one of them went bad without me knowing it. After an afternoon of sailing, with the tv on for the kids and fans going, the other house battery started my Yamaha 50hp with no problem. But I did go right out and bought one of those jump starting systems Tom Root talked about. I find that it is really nice to have it for the extra light and if we need to charge cell phone on shore.

God Speed
Dave

I have two batteries, but they are connected together as a single bank. This has served without any problems for 4 years. The two battery, combiner systems are great, but for such a simple boat with the simple electrical system we have it seems unnecessary overkill. If all you're using is lights, stereo, instruments, there is really not a need for all that complexity.

Skip the big red switches, combiners, etc. Put your money in a good battery meter and connect they system up as a single bank. Your batteries will last longer too. Taking 30 or 40 amps out of a parallel two battery system is much better than taking the same amount out of a single battery half the size. The life of your batteries is directly related to how deep you discharge them. Why have that starting battery sitting there doing nothing while you kill you house battery with 50% discharges. Unless your running something, like a fridge, that you expect to regularly drain the battery there is no need for a separate system.

These aren't boats we're cruising around the world in. Keep it simple.

I do carry a small simple jump starter but have never needed it for the boat. The Tohatsu 50 can be hand started, one of the boats on the San Juans trip last summer did it easily, first pull (his battery wasn't dead, he had wiring issues with his key start system). You do have to remove the plastic cover to access the flywheel. Or better yet, take it off and leave it home. It's only a safety cover for when you run the engine without the casing installed. How often do you do that? I never do. So take it of now so if you need to hand start out on the water you don't have to mess with undoing the bolts.

my battery setup is: 1 starter battery, 1 house battery, west marine battery combiner, switch with removable key to put them together in the case of...

did you ever handstart a 50hp 4stroke? i did 2 times (before i added the 2nd battery). it was not easy! was ok when laying stern to shore and standing on the pier. was difficult when working in the cockpit: too less space to pull with full power, steering wheel and pedestal were in the way. a longer starting line with a better handle than the factory providedr small red plastic thingie may help.

Hello:
Here's my take on this. I use two batteries with switch. When I'm on a vacation with my family I don't like problems. I keep the tow rig & trailer in good shape for the same reason. I leave my switch on the house battery most of the time. Makes it a no brainer, I don't have to remember to isolate or switch anything. After 7 years of service my house battery just didn't have enough reserve capacity left to start the motor one morning. I just switched over to the starting battery to "jump start" the motor and we were off. No interuption to the trip to make port and replace the battery. We just continued the fun and replaced them both when we got home. That is the beauty of redundant systems. Problems like these have a habit of happening at the worse possible moment, like when you have to switch fuel tanks in the middle of a traffic lane and the motor will not restart.

Have to agree with Don & Norbert. Pull starting a 50HP is theoretically possible, but that remains no more than a theory until you've actually done it, from a cold engine, in an emergency.

Choosing your battery setup based solely on planned usage is ignoring Murphy.

In an emergency, you may need your motor to start now, not sometime in the indefinite future. Don't know about the others, but pull starting my Tohatsu involves removing both the outer cover and the cover on top of the motor, and removing the top cover requires a wrench to remove three screws. Not that tough, but realistically it's going to take 4-5 minutes, assuming I can find the wrench and pull cord in a hurry. Starting mine from cold normally requires five or ten seconds of cranking; I figure that's at least four or five attempts with the pull cord. It's certainly not something I'd want to attempt while being current driven toward the falls, wind driven onto a lee shore, or trying to get out of the way of a VLCC bearing down on me at 20 knots.

Combiners, splitters and switched banks aren't all that complicated; if running any of these is too complex, then you may as well save the complexity of two batteries as well. You'd be better off to run a single large one instead. It's cheaper, easier to mount and maintain and more efficient from a weight standpoint.

Wow, thanks for all the responses and tips so far. Seems like there are a lot of different opinions on this topic and many more than one make good sense.

My Merc 50 has a plastic cover that goes over the flywheel and timing belt but it goes off and on easily without any tools. I've never tried to hand start it, but I did once about 20 years ago on a larger 2-stroke (85HP I think). It was no cakewalk but I got it done (was also in better shape then though). Seems like my 4-stroke would be much easier to start though. My Merc even kicked over in the first 1 second right after I recently reinstalled the carbs after a dis/re-assembly for un-clogging purposes. I can see how the pedestal or rear pulpits may get in the way though. Guess you would have to use a short strong pull...and definitely not forget to have the key turned on A nice big wooden handle would make the job easier too.

My boat already came with the big red switch so I figure as long as I don't forget it on "both" when I really should be isolating, I should be ok.

Don, with your setup, how does the "reserve" (starting) battery get charged? I thought if you just had a plain switch installed (ie, no combiner), you would need to put it on "both" once in a while to charge it...ie, the battery that is not connected to the engine wouldn't charge?

Hello:
Dimitri, I have a 20 amp diode between the batteries (across the switch). When the house battery is charged back up and the volts get high enough it passes current to the starter battery. It stays topped off.

Jack O'Brien wrote: .... My Suzi DF50 injected 4-stroke starts immediately regardless of how long since it last ran (might be 3 months or more). So I see no need for a separate starting battery ....

Agreeing w/ Jack, my Suzuki 60 starts 'first turn, every time" just like my Ford and GMC trucks always have. Electronic fuel injection represents one of the great paradigm shifts of the 20th century.

I have two batts, combiner 50, as setup by my Mac dealer on the new boat. However, I liked Duane's approach when I first heard it, and I'll probably join them in a single parallel bank. Also, have been watching eBay for a Link 10. There they are going for $200, or a little less, so I may just go retail.