running dual batteries
Submitted by paul d on Thu, 2015-07-02 16:00
Hey guys,
I've got two batteries on my boat with a switch to have power to battery 1 , battery 2 , or both.
My question is how is the best way to run them ie; both at the same time ,or battery 1 going out , battery 2 coming back in ?
Your thoughts would be appreciated.
Cheers Paul
Starbug
Posts: 563
Date Joined: 27/08/09
The later. Avoid running them
The later. Avoid running them on 'both'. If you have any problem with a battery it will take the other one down with it.
Tradewind
Posts: 756
Date Joined: 18/09/12
I always run on the first
I always run on the first battery including when at stop using the Radio & Sounder
That way if I run it flat I can switch to the second for the trip home
D_d_001
Posts: 1522
Date Joined: 09/03/13
what starbug said. but to
what starbug said.
but to elaborate never start or run on both (except emergency)
best way to go is start and run on one for the trip out. then switch over and start and run on the other for the way back. to keep them both charged to full.
Ideally it's best to replace them both at the same time for reasons starbug says..( a dead battery will kill the good one if run in parallel.)
epic restos and...
Posts: 226
Date Joined: 22/06/15
the best way to use duel
the best way to use duel batteries in my mind is each time you go out start and run on the other battery so your always changineing the load so each battery wears evenly or install a red arc inverta monitors each separate battery and attends to it (but they are costly)
Starbug
Posts: 563
Date Joined: 27/08/09
If you want to keep you
If you want to keep you batteries in good shape, buy a multi stage "smart charger" and give then a charge once a month. Charging one battery at a time.
The day before you head down to the ramp, try starting the motor on each battery.
And as others have said, if one battery is getting weak, the other wont be far behind. Replace them as a pair.
Rob H
Posts: 5745
Date Joined: 18/01/12
Suprisingly-everyone is on
Suprisingly-everyone is on the money above for a change!
I dont know how many times on forums Ive seen people argue black and blue that you should run on both etc
And also the number of times over my years at sea of skippers with dual batteries flat at sea and almost invariably said "it wouldnt start on bank1 so I put it on both for the trip out..."
As D--D says, only EVER use "both" to start if needed, then immediately put in on 1 or the other.
Another point-many people think its a good idea to leave a smart (or solar) charger on their batteries permanently while its parked up.
BUT-how will you know a battery is on its way out? You'll find out the first time you stop for an extended period, drifting, anchored etc.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
Brucesta
Posts: 1721
Date Joined: 29/05/09
alternate your trips on each
alternate your trips on each battery if you're using it often. just run on battery 1 for the day one weekend then switch to number 2 the next trip.
I replace my batteries every 2/3 years and the boat gets used most weekend so i don't buy into the whole switching too much but it is true if you have a bad cell on bank 1 then it'll drag down bank 2 with it as you start or draw load off them.
Las Vegas - Rolling the dice and trying your luck. 1M+ Barra summer target. 100kg Black Marlin winter target
ranmar850
Posts: 2702
Date Joined: 12/08/12
Smart relays are the go.
Someone mentioned Redarc, but there is a marine setup available with three switches and a smart relay all in one compact unit, about 200mm square. Switches are Crank, House, and Both.Crank is your starting battery, House is accessories. With both House and Crank on, you are charging into House only when Crank gets above 12.2v, or similiar, like a Redarc.Not expensive, $200-ish? House cannot drain Crank if you leave stuff on. If you need both to start, turn Both on, and they are parallelled. Foolproof, really.Had one on the boat i just sold, will fit one to the Dommie when i get a chance.
From the beach at sunny Ningaloo.
sstevee
Posts: 466
Date Joined: 15/11/11
As above... Check out the
As above... Check out the blue sea 'add a battery' systems... I have one in my tinny... One switch and one voltage sensitive relay... Switch has 'on' 'off' and 'combined(emergency only)'... All I do when I get on board is turn the switch to on... The cranking battery is charged until it is happy, then the VSR combines the batteries while putboard is running. If I stop it isolates the crank and house batteries allowing me to potentially flatten the house battery with no negative affect to the crank battery..
boonmack
Posts: 69
Date Joined: 31/07/11
I'ven got the same set up as
I'ven got the same set up as sstevee.
wish I was fishing
jng
Posts: 488
Date Joined: 03/08/07
I run the BEP vsr- had it on
I run the BEP vsr- had it on the last 2 boats and works a treat.
Sharky1
Posts: 18
Date Joined: 17/08/15
I'm currently rewiring my
I'm currently rewiring my boat with dual batts. I'm going to use the same system as I have in my 4WD, 1x Cranking battery & 1x Deep cycle battery for everything else. The motor only charges the cranking battery as the deep cycle chrages from the cranking battery via a 30A DC-DC charger which stops charging either once it senses the cranking battery is no longer recieving charge or when the cranking battery drops to 12.5V which is usually within a minute of turning the motor off.
It's better for weekend trips. You don't have to worry about remembering to switch batteries & by using a deep cycle you get longer use out of your accessories. The DC-DC charger I have is fully waterproof. It costs about $400 & has much less wiring than isolators. I guess you could always have a charging switch from your motor to go between batt 1 & batt 2 in case the DC-DC ever fails & you need to charge the deep cycle.