Elect70 is on to it, so is some of pcd1 post. The motor will not have enough charging grunt to charge two batteries. If one battery is not as good as the other the the dud battery will pull the good one down if their wired together. Best to keep everything seperate, you can always jumper the battery with the other if one fails. Keep it all simple and seperate. just charge the auxilary battery from time to time at home.
kaspas,
Jul 19, 6:06am
no that would then be 24 volt
taipan4,
Jul 19, 6:13am
and probably damage the electronics on your outboards
petermcg,
Jul 19, 10:03pm
Put a solenoid between the batterys so as to only use battery two for cranking only,, work a switch system for charging battery two.
budgel,
Jul 19, 10:29pm
Putting two batteries with the same output in parallel wont add any more grunt for starting, but you will have the same output for longer.
petermcg,
Jul 20, 5:43am
Good point,
bigfatmat1,
Jul 20, 7:47am
same voltage increased output. Go have a look and see how an american trucks battery system is wired. 4 batteries 12v remove 3 i bet ya bottom dollar it wont start. in saying that wont make squat of diff in this application because a boat starter is not going to draw 600+amps
the output is equal to the sum of all batteries output providing they are in good condition
kaspas,
Jul 20, 9:31am
best to buy two new batteries same brand and from same batch then parallel will be fine,otherwise you get problems like 1 draining the other.
splinter67,
Jul 20, 10:10pm
not probably it will wreck the electronics on your boat
splinter67,
Jul 20, 10:17pm
If all this is to technical for you go to an auto electrician they will tell you exactly what to do safety first a long way to swim if it dont start
bjmh,
Jul 20, 10:24pm
get a modern battery charger ,when the boat is in the shed trickle charge the battery.last boat i had the battery lasted 9 yrs with this set up.There are solar powered charging systems available that would probably work well on a boat.Talk to a competent auto / marine electrician.
gowgirl,
Jul 20, 10:24pm
BOOM!
skyblue17,
Jul 20, 10:40pm
Ehh.! Thats what happens everytime you jumpstart your car with another battery. If you didnt get any more grunt why bother!
budgel,
Jul 20, 10:57pm
I was talking about running two charged batteries in parallel with each other as a permanent setup.
There will be more amp hours available,so you can crank longer, but there is still the same number of cold cranking amps available.
Your jumpstart battery is just bringing things up to what the original was in the first place.Effectively running it for longer. (assuming identical batteries.)
In PARALLEL CONNECTION, batteries of like voltages and capacities are connected to increase the capacity of the battery bank. The positive terminals of all batteries are connected together, or to a common conductor, and all negative terminals are connected in the same manner. The final voltage remains unchanged while the capacity of the bank is the sum of the capacities of the individual batteries of this connection. Amp-Hrs, Cranking Performance and Reserve Capacity increases while Voltage does not. This too
bigfatmat1,
Jul 21, 1:52am
.ummmm does not matter.
elect70,
Jul 21, 2:12am
What do tyou think they do for big marine deisels ,could be 6parralledtogive the requiredcca( cold cranking amps ).1 batterywouldnt do FA , butnot wise on an outboard
skyblue17,
Jul 21, 2:23am
Exactly
rsr72,
Jul 21, 2:27am
#1- Not at all unusual for outboard trailer runabouts to run two batteries, one for starting, one for house operations, and switched using the normal three-way/four way battery masterswitchwhich can be bought from any marine shop.
ummmm I did.Btw it may not be a flat batt for a jump start but a batt with reduced output because the batt is old thus you are still adding to the cca. a batt partially down in charge will also have aoutput this also adding to the sum of the cca. unless its dead flat then it wont
bigfatmat1,
Jul 21, 3:43am
as per my earlier statement as well with alot of trucks 4 batteries parralled up some in a series parallel configuration for 24v and twice the cca some starters like a 50mt will draw upto 2000 amps i do not know of any truck batteries with that amount of cca
gmphil,
Jul 21, 4:46am
Hey op lookin at doin same also have yamaha v140 . Like u am at mo use one battery is deepcycle but want add second for safety lol cant get out and push .apperantly when u buy switches has wiring diagram so that me hopfully otherwise of to lecky as wiring not my strong point . just thursday mate had to get coastguard as stator had gone lol he said starter up fine off fishin but come time go home nuthin dead flat
alan1111,
Jul 21, 9:30pm
Safety comes 1st when out on the water as cant just swim home. I am a mechanic and have been for 28 years, i own a boat and run 2 batteries 1 as starting battery and 1 as a house battery for lights etc. Even with my knowledge i could of installed the switches easily BUT i went to a qualified boat mechanic to do it for me. My suggestion is seek proffesional knowledge aand pay the little bit extra just for peace of mind. Good luck with the boating.
granada,
Jul 22, 12:12am
Every decent boat Ive ever been on has a house battery and starting battery with a manual change over battery master switch. The master switch can isolate both batteries when the boat is unused. Select the house battery only for using lights, fishfinders , etc. or select the dedicated starting battery, or parrallell the two batteries together for charging and emergency starting.
Get it fitted by someone whom knows what they are doing, Make sure all your battery cables have soldered conections, and buy batteries that are fit for the job.You cant push start a boatthere are too many cowboys out on the water,.so dontbecome a statistic by doing it yourself
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