Backup for a backup... for a back up...

ccarver80

Petty Officer 1st Class
Joined
Feb 17, 2015
Messages
238
so I'm a worry wart.... I have a 2004 16' Crestliner super hawk. with a 04' 75hp Yamaha 4 stroke (the engine dose charge the batteries).. it has a starter battery, and 2- 12 volt batteries up front for the trolling motor...(they are NOT connected to the starter battery in the back)


I'm always wondering "What if" ... and got to thinking if the starting battery dies on the water what are my options... this is what I came up with:

In the back exactly on the opposite side of the starting battery is the same exact size compartment that I could put a "spare" starting battery...that I could just run some jumper cables across?? (then I'm not unhooking wires and swapping batteries)

thinking of carrying a "jumper pack" as well.....

3rd back up option.... tell me what you guys think...

the 2- 12v batteries up front are for the trolling motor... (its a 12 v system... Neg connects to Neg... and Pos. to pos....) They are not connected to the starting battery.... What if last ditch effort... could I run jumper cables from the trolling motor batteries to the back to the starter battery in case the starter battery dies?? (like Say I take a nap listening to the radio and wake up to find the batteries dead)

Also would this work vise versa if my trolling motor batteries died and I hooked the jumper cable to them from the starter battery and cruised on the water for a while?? (I ran my motor last night and with the key in the on position, it was reading 12v but with the motor running it was in the 14v range just idling)

Like I said... in my head I'm always running "what if this happened" scenarios in my head.... I just don't want to fry any electronics or do something stupid
 

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
You could jump the starting battery from the trolling motor batteries. I wouldn't jump from the starting battery to run the trolling motor- won't take long to run it down enough that you won't be able to start the Yamaha. I carry a jumper pack. With its built-in air compressor and 12V outlet, It's handier than yet another battery.

A fully charged 12V lead-acid battery should read 12.6 volts, plus or minus maybe a tenth of a volt. If you're reading 12.0 volts even, your battery is 50% discharged. As you noted, when the motor is running it'll read higher, like 13.5 - 14. Sounds like your alternator is fine.

My .02
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
1. Install the second starting battery and connect it via a dual battery switch.
2. If your motor has the proper setup, carry a rope to pull-start it.
 

ccarver80

Petty Officer 1st Class
Joined
Feb 17, 2015
Messages
238
You could jump the starting battery from the trolling motor batteries. I wouldn't jump from the starting battery to run the trolling motor- won't take long to run it down enough that you won't be able to start the Yamaha. I carry a jumper pack. With its built-in air compressor and 12V outlet, It's handier than yet another battery.

A fully charged 12V lead-acid battery should read 12.6 volts, plus or minus maybe a tenth of a volt. If you're reading 12.0 volts even, your battery is 50% discharged. As you noted, when the motor is running it'll read higher, like 13.5 - 14. Sounds like your alternator is fine.

My .02

Ok, cool, that was gonna be my next question... how low of voltage can i go till i need to crank my motor up to charge it??? my depth finder has a "low battery alarm" and i can set it between like 10v - 15v and it will go nuts if the voltage gets that low.... i tested it out.... what would be a good alarm set point to were i can crank the motor up for a few to recharge the battery ?
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
A 4th battery sounds overkill and unneeded extra weight. Like I should talk... I had 4 batteries, and now a 5th in my 18'er....

I would (and do) carry a set of good quality jumper cables, then jump off the trolling batteries if needed. I bought 100' (50' each of black/red) of 6ga tinned marine cable, ring terminals and heavy duty parrot clamps to make jumper cables for the car, truck and boat. Be careful buying jumper cables as there is a lot of cheap CCA aluminum wire jumper cables on the market now... I have my start and trolling batteries wires to a switch though, and can just flip a switch if the start battery goes dead.

With your setup, I would wire a battery switch between the trolling batteries so you can run off one, or both batteries. Discharging batteries slower will give more run time, so running them in parallel will (should) yield more run time. But.... If you have a weak battery it will discharge the stronger battery. In my jon boat I usually have the switch in combine mode so the 12V batteries are running in parallel, but if I think one of them is getting weak or isn't charged enough, I run them separate, running the weak battery down first. One trip I only got 1/2 hour out of the suspected bad battery before it crapped out....

I would set the low battery alarm at 12V, a tad more than 50% discharged.
 
Last edited:

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
OK -- you've covered all the "what if's" and only one that poses a problem is running the trolling motor off the starting battery using jumper cables. You have two dead or dying troller batteries up front and now decide to jump from the starting battery to those two. Those two dying batteries will suck the juice out of the starting battery whether or not you are running the troller. DON'T DO THAT! You can of course jump the trollers to the engine battery to start it provided you haven't already depleted the trollers to the point where they can't crank the engine. When you have the engine started, disconnect the jumper cables so the full capability of the alternator goes to the starting battery. If, and only if you run the engine while jumping the starting to the trollers so you can troll some more, then that would work but may tax your engine alternator and lead it to early demise. So then I suggest just using the engine to troll. It will run all day at idle with no issue -- but then you didn't tell us what size Yamaha engine you have. The real solution to this problem is when you deplete two batteries trolling, quit trolling or troll with the engine.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,620
I would set the low battery alarm at 12V, a tad more than 50% discharged.
If it's a starting type battery, even that is too low to go. You shouldn't discharge a starting battery more than 80% which is 12.4V.

I would not try and run the trolling motor off the starting battery.
 
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