charging same battery with two motors?

[Kuba]

quick question, i have a 50hp outboard and a 6hp kicker on my boat, the 50 starts and charges the battery, can i also hookup the charging circuit from my new 6 to the same battery? Could this damage my 50 and vice versa?

[jimski2]

My 90 and 9.9 HP motors are hooked up to the same battery for five years now and I have not had a problem. My Lowrance voltmeter shows up to 14.5 volts at times when it is fully charging and I never noticed a problem with both motors running together when I start the other one up to warm it up before I shut the other one down.

[Don Supon]

Ran a 135 and 9.9 from same battery and never had a problem in 5 years. Added a 2nd battery to run the 9.9 when autopilot was added to the mix to seperate from main starter battery because I was concerned the 9.9 alternator might not recharge enough to keep up with the autopilot drain throughout an 8-10 hour troll at med to low rpm's. Overkill probably, but didn't want to experience returning to launch with the kicker only, because I couldn't restart the 135. 

[pokepole39]

why on earth would anyone head to the lake with only one battery to trust ..not being a smart ass but not the best move in the world unless you can row real good

[Kuba]

How big of a battery would I need to restart my 50? Would a motorcycle battery work? If it would I might get one and hook iit up to the kicker and have it charged while trolling? And use it as a backup.

[Sk8man]

When I bought my boat brand new I was told that because my 9.9 and 135 Optimax had different alternator amperages that if they were hooked up to the same battery they could shorten the life of the battery and may create (otherwise unspecified) problems so I've always had two batteries - one a heavy duty starting battery the other a heavy duty combination deep cycle and starting battery. The starting battery is hooked up to the 135 (and depth finder etc.) while the other battery is hooked up to the 9.9 and my electric downriggers and electric trolling motor. I was told by a number of marina mechanics that my 135 (and engines like it) needed at least half charge in the battery at all times to turn over the engine because of the high amperage draw they have. I have NEVER had a problem with this set up (other than normal battery replacement once since 2002). Don's comment above about the charging capability of the small motors alternator is a good one too. Unless they are run at HIGHER speeds they are not charging with anywhere near the max amperage you might assume.

 

My advice would be to have TWO batteries and get the best ones you can afford. They are at the heart of everyone's system and its not an exaggeration (on Lake O) to say that your very life could depend on it (dead batteries almost always happen at the worst times).

 

Kuba I just happened to think of an additional possibility and that is a PORTABLE MARINE starting unit that has multiple uses and you can take it from boat to boat as well. They are quite powerful and are rechargeable  in conventional electrical outlets. Places like Cabelas have them for about the cost of a good battery (about $100)

Edited March 15, 2013 by Sk8man

[Jack]

It's crazy what batteries cost now but , I would never have just one . I have two connect to a switch one runs my main engine and all the accessories the other runs the kicker . If someone (me) leaves the lights on and the battery goes dead  i just flip the switch and run on the kicker batt .

Summer is to short to  miss a day of fishing for a dead batt  .

 

Good Luck !!

[rolmops]

The fifty horse can use a small car battery and never have trouble,unless the battery is drained by a day of riggers going up and down,or if it is a walmart battery.

It is always a good idea to have one deep cycle and one regular starter battery.

That with a Pergo 3 way,so you can choose which battery to charge from what engine with the turn of a knob.

Besides,you can buy a trickle charger  for $30 at sears,this enables you to always completely recharge your battery while at home.

Edited March 16, 2013 by rolmops

[Kuba]

I have 6 marine batteries in my house, 4 were purchased last summer and are a part of my solar array, the two from my boat will go into that and two from the array will go onto my boat.

There is plenty batteries in my house:) The problem im having is my boat is only 17 feet, at the rear its about 80 inches wide. On both sides there is boxes with foam. by the transom there is a "bench" where two batteries were located, one for main engine + accessories, other for the trolling motor. Last year my brand new Terrova with GPS got stolen so i removed the trolling battery and stuck my portable gas tank in the spot underneath the "bench".

Now, if i install a second battery, i will have two gas tanks on the floor, one for my main, one for the kicker. Yes, i know i can run both engines out of one tank either by purchasing a tank with two attatchments or by doing a 3 way connection, but still that will leave me with a tank outside. Im just trying to make it work:) Thats the reason why i was asking if i can start my main with a motorcycle battery, or a small car battery.

Edited March 16, 2013 by Kuba

[Sk8man]

One of the things to consider battery-wise is that marine batteries are specifically designed to withstand considerably more VIBRATION than conventional car batteries I don't have any experience (or knowledge) regarding motorcycle batteries but where you place another type than a marine one may be a consideration.

[Kuba]

Do any of you know how many AMPs a 50hp draws at cranking?

[jimski2]

My 9.9 hp starts easily with the hand pull cord and it recharges the battery when it runs. I have more faith in the extra motor than two batterys.

[Frisco]

I would recommend using separate bateries. Keep in mind that both motors have alternators that charge at different levels depending on what level the batteries are. Serious problems could exist with different voltages in regards to voltage sensative equipment in the OB or other devices. At no time should you be running the motors at the same time. Both my OBs have separate batteries with a switch between them in the open position if one is dead I simply close the switch and it acts like a jumper. At my electronics are off the kicker which uses the most hours.

[rolmops]

How about putting one tank in your splash well?

[Kuba]

This is my tight corner, i also would like to install a water separator somewhere. i have a 33AH battery that came from emergency lighting box. I think i will try that once it gets warm to see how it will work starting my main.

 

 

[Sk8man]

You might be able to get away with placing the small gas tank ON the shelf (bracketed  and secured by something like a metal not plastic battery tie down) that could free up the corner space on the floor

 

 

I had previously mentioned the marine battery starter thing that has multiple uses and which can start up MANY low batteries as well. You could even store iit up in front or under a seat or something. That way you would have emergency start up capability but not be committed to a specific space. I have two of them that I keep for home use as well and I've helped countless people out (cars and boats) with the things. Some even have USB slots to charge your cell phone

 

Here is what I'm talking about (mine is different but same concept)

 

http://www.cabelas.com/catalog/product.jsp?productId=747143&destination=%2Fcatalog%2Fproduct.jsp%3FproductId%3D1191397%26type%3Dproduct%26Ntk%3DAllProducts%26searchPath%3D%252Fcatalog%252Fsearch.cmd%253Fform_state%253DsearchForm%2526N%253D0%2526fsch%253Dtrue%2526Ntk%253DAllProducts%2526Ntt%253Dmarine%252Bstarter%252Bbatytery%2526x%253D0%2526y%253D0%2526WTz_l%253DHeader%25253BSearch-All%252BProducts%26Ntt%3Dmarine%2Bstarter%2Bbatytery%26WTz_l%3DHeader%253BSearch-All%2BProducts&WTz_l=YMAL%3BIK-524079

Edited March 16, 2013 by Sk8man

[rolmops]

Man, that is a very tidy and effective set-up.

You may get away with taking the measurements of the space where your battery is now  and get the biggest possible one in there or the 2 smallest batteries ( I'm thinking honda or fiat size).

The biggest possible one would probably be the most cranking amps. Combine that with a pergo 3 way switch and with the flick of a switch  you can choose which engine you want to charge the battery with.

As for a water separator ,you don't really need it because these small tanks are often almost emptied and they can easily be removed and emptied by hand if there is water or dirt inside

Edited March 16, 2013 by rolmops

[Sk8man]

By the way I agree with Rolmops you have made VERY good use of the space you have there......very neat and orderly ...lots of room left for tangled lines and that kind of stuff too

[Speed]

I only have one starting battery that gets charged by the main motor and then the kicker while trolling but always keep a fully charged automotive Jump start pack in the boat just in case for cheap insurance

[Kuba]

I will take some measurements today.

 

Sk8man, i saw somebody's setup like that with the small tank with the kicker, not too recently, here on the site. Will look for the pictures.

 

Bought some beers, so once i put my 4 year old daughter to bed (single parent here) i will wonder off to the garage and i'll try to figure out the spacing etc...

will post pictures soon

 

 

call me crazy, but im thinking of getting one of those as backup....... http://www.ballisticparts.com/products/batteries/12cell.php

 

 

check out the size of those!!!!!! amazing!

Edited March 17, 2013 by Kuba

[Sk8man]

It does look cool but I'd carefully check out things beforehand e.g. 13.6 volts and 400 amp burst etc. and how it would operate in your application (marine use) or if would void a warranty if you have one  on the motor. I wonder what the difference is in the special charger they offer relative to the amperage your alternator would be putting into the battery.

 

Pretty slick if it would work!  The beers may help ease any anxiety :>)

[jimski2]

With all the battery, fuel tank, main motor and kicker motor on your transom, you are susceptible to taking a swell over the transom. Be careful out there, I learned out the hard way, a couple times.

[Kuba]

Well, actually the only thing that was added to the boat is the kicker. All the stuff in there came like that from the factory. I also removed the second big trolling battery plus I check the weather all the time.

[Chas0218]

why on earth would anyone head to the lake with only one battery to trust ..not being a smart ass but not the best move in the world unless you can row real good

The original poster could probably start both motors by hand.  Being a 50hp engine it would be tough but we have done it to my fathers 50hp 2 stroke before.

 

Maybe a battery relocation would be a good idea for you into the front of the boat if possible.

Edited March 18, 2013 by Chas0218

[Kuba]

My kicker is pull start .only I never tried starting my 50 hp by hand. It never failed me