2nd battery needed if installing prawn puller??

[wild.coast]

18ft RIB zodiac with 50hp Yamaha outboard, currently have just one battery used for starting + electronics.

Just got a prawn puller which has a 3.4-30amp load range. I definitely don't want to drain my only battery and be stranded, wondering if I should be wiring up a secondary battery? Space is at a premium, so I'd rather only do this if I have to!

Curious if anyone has any advice?

Details on my setup:
My current battery is a NAPA 24RVS deep cycle (link)

• Cold Cranking Amps: 575 A (makes me think this is technically a dual purpose deep cycle considering the high CCA)
• It has a 130min reserve capacity (54Ah)
  • I understand that reserve capacity is how long a fully-charged battery can deliver 25 amps of current in an 80°F environment, before the battery is discharged down to 10.5 volts.
  • I understand 130min to mean that I can operate the prawn puller for just over 2hrs, correct?

Thoughts/questions:

• Prawn traps are not crazy heavy, so I'm assuming it's not actually drawing the maximum 30amps, more likely 20-25?? But I have no idea.
• On a given outing I'm usually pulling 3 traps @ 400ft of line, which usually only means the puller will be running for ~5min x 3 = ~15-20min
• Any way to calculate how much 15-20min of pulling would drain down the battery?
• Would my outboard still start if battery is at 10.5v?
• I'm assuming if my outboard is idling the alternator would also be charging the battery while the prawn puller is operating, so less draw

 

[alldodge]

I would think about using a LifePo4 Bat. These Bats can be drained almost dead and still be fine. A small one could run the puller most the day and still be fine. Just recharge upon returning

 

[Horigan]

The numbers say the single battery would work. I would assume 30A for this calculation (I sometimes blow the 30A fuse pulling pots) so you'll pull up to 10 Ah (amp hours) in 20 minutes from the battery, without idling.

 

[cyclops222]

Once you get the pots moving ? Rev up the 50 hp engine to 1/2 of max speed. It will keep battery up & share the current being used by the puller motor.

If you have a fish finder or depth reader ? program the low battery alarmto about 12.2 volts.

 

[flashback]

It's always nice to have a spare battery

 

[Texasmark]

In my early years of running a new, low powered trolling motor on a 16' Chrysler Sport Fury, 85 hp Chrysler engine, with a single cranking battery, I ran the battery down to the point where it didn't have enough energy to start a new 85 HP engine.

I had to pop the cowl, get the cranking rope out of its neat plastic bag on the underside of the cowl, get everything ready, have my other occupants get out of the way of a possible "flying cranking rope", wind the rope up on the space provided for such item on the top of the flywheel, and give it a hard tug........It lit right off...yeaaaaaaaaa.........I never had that problem again....and its been several decades.......read between the lines!

If you don't want to subject yourself to a possible similar situation, don't sell yourself short on battery power....I mean a battery in a battery box, strapped to the top deck is no biggie and can save you some heartache if you don't have space to put it elsewhere.....I mean you are making room for your pots when they aren't in the water.....your rig, your effort, your decision.......good luck.

 

[dingbat]

outboards typically don’t charge while idling.

The rated output of the charging system is rated in hours of run time. A 30 amp system is charging at a rate of 30 amps per hour

 

[cyclops222]

Old Evinrudes, 1986 and newer 9.9 hp and larger have a working 5 amp alternator and rectifier of 5 amperes. At rated speed.
But the OB motors are NOT run long enough & fast enough to keep replacing the power being used up every trip. Add in winter storage & you are buying a new battery after a few years.
A great battery charger can do wonders for years of reliable full power needed.
Who teaches people that a boat ....IS NOT.... like a car with the same battery in both ? Does the Mandatory Boating Safety Course teach what is needed ?
A person who passes out or goes into severe pain spasms' will convince you of taking better care of the battery and instant engine starting.

 

[wild.coast]

Once you get the pots moving ? Rev up the 50 hp engine to 1/2 of max speed. It will keep battery up & share the current being used by the puller motor.

If you have a fish finder or depth reader ? program the low battery alarmto about 12.2 volts.

Oh good, idea. I have a Garmin ECHOMAP Ultra 106sv - I believe it gives you battery current read out.

 

[mr 88]

Buy a small jump box for less than a hundred bucks, will fit in your glove box. Leave it in the boat for the season , then in the car for the winter ,problem solved.

 

[Texasmark]

Oh good, idea. I have a Garmin ECHOMAP Ultra 106sv - I believe it gives you battery current read out.

Where's the sensor, especially the current sensor? You have to have something, usually wrapped around the cable that converts amperes to volts....sometimes a series shunt is used for that purpose but you don't want a shunt in a starting circuit.....adds resistance, however small.

 

[dingbat]

Oh good, idea. I have a Garmin ECHOMAP Ultra 106sv - I believe it gives you battery current read out.

Nope….no current, voltage only