When do I need dedicated power for electronics?

[stk44]

Currently I have two 10” helix units, the auto bilge, and livewell pumps running off my group 31 AGM, 100 amp hr cranking battery. 
 

in the next 1-3 years I plan to add power poles, a helix 12, and likely mega live with target lock. At what point do I need to start thinking about having a dedicated battery for all these electronics? 
 

I’m not sure how many amp hours the auto bilge and livewell pumps take up, but I think each fish finder alone takes up close to 3 amp hours. 
 

Thanks in advance!

Steve 

[MN Fisher]

I'd do it now.

 

I run my electronics (Striker 7cv, lights, auto-bilge, LW recirc, tablets (mapping software) and cameras from a 18ah battery. Trolling motor has it's own 100ah and the cranking battery is separate from all the rest.

 

I calculated it based on average run - the LW recirc is a 2amp draw....but it's on a 30sec-on, 270sec-off timer - so hourly draw is 0.2amps average. Bilge is also a 2amp, but runs rarely, so I rated it a 0.1amp draw.

 

Calculate everything up, times the longest number of hours you expect to be out, then for a AGM multiply by 1.4 - need to keep reserve for proper charging...never drain an AGM lower than 40% charge.

[Jig Man]

You will find out by your cranking battery not being able to start your motor.  I have 3 Solix units and they would do that to me so I pulled them off the cranker and put them on a stand alone 100 ah lithium.

[Tennessee Boy]

It depends on so many things.  Your outboard will charge the battery when it’s running.  I’ve run more stuff than you have on a group 27 for 12 hours but I spend a lot of time idling around graphing which charges the battery.  I ended up adding a 75 ah electronics battery because I was having issues with the voltage drop that resulted when I cranked the outboard. 

[stk44]

18 hours ago, MN Fisher said:

I'd do it now.

 

I run my electronics (Striker 7cv, lights, auto-bilge, LW recirc, tablets (mapping software) and cameras from a 18ah battery. Trolling motor has it's own 100ah and the cranking battery is separate from all the rest.

 

I calculated it based on average run - the LW recirc is a 2amp draw....but it's on a 30sec-on, 270sec-off timer - so hourly draw is 0.2amps average. Bilge is also a 2amp, but runs rarely, so I rated it a 0.1amp draw.

 

Calculate everything up, times the longest number of hours you expect to be out, then for a AGM multiply by 1.4 - need to keep reserve for proper charging...never drain an AGM lower than 40% charge.

So basically I have 60 amp hours available without degrading my AGM, right?  My helix’s and other electronics take 6 amps/hr so I can go for about 10 hours assuming I never turn the big motor on. 
 

Another helix would definitely be out of the question, correct? 
 

The only thing stopping me from doing it right now is that I’m tired from troubleshooting fixing my truck and boat lol. I would have to figure out how to rewire everything, add a cut off switch, add a 4 bank charger, etc. I do not have much electrical knowledge unfortunately and still trying to figure out which wires power what device in the boat. 

 

Thanks again!

Steve 

[Jig Man]

I think you are heading for a dead cranking battery by drawing it down that far.  The simple solution is to put in a “house battery” and connect all of your sonar units to it.  You can do like I did and install a single bank charger to take care of the house battery. It would not be difficult to extend the power wires from the units to the house battery and hook it up to the new charger.

[TnRiver46]

When do I need a house battery for accessories? When the motor won’t crank. Queue the rimshot……….

 

seems like you’d want max amount of CCA if you don’t use a house electronics battery. Granted your motor won’t charge a house battery up with the alternator/stator. 

[Junger]

I run 2 Helix 10 G3N's, ethernet, auto-bilge, auto-livewell and a BT radio and speakers off my Group 24M cranking battery, 56AH 1000MCA. I've fished with all my electronics on for long long hours (8hrs+). The Helix 10's don't draw much (I think I calculated 1.7ah at one point), and I put the brightness around 60%. I just tested the battery and it's at 97% health in year 3.

 

That being said, I'm putting in a 105AH dual purpose LiFePO4 to replace it next week. I'm finally making the change to lithium batteries because my 3 year old onboard charger has a bad bank and I'm replacing it with a NoCo GenPro.

[stk44]

3 hours ago, Jig Man said:

I think you are heading for a dead cranking battery by drawing it down that far.  The simple solution is to put in a “house battery” and connect all of your sonar units to it.  You can do like I did and install a single bank charger to take care of the house battery. It would not be difficult to extend the power wires from the units to the house battery and hook it up to the new charger.

Did you install a shut off switch for the house battery or is it not needed? 

[MN Fisher]

1 hour ago, stk44 said:

Did you install a shut off switch for the house battery or is it not needed? 

I dunno about him - but I have shut-offs for every battery.

[Jig Man]

Not for the house battery, but everything else has a master shut off.

[Tennessee Boy]

I’m a firm believer in switches that get turned off at the ramp before I head home.   It’s less important with LifePo4 batteries because the BMS should provide the same protections if it’s functioning properly.   Still,  switches are cheap and fires are not.

[stk44]

2 minutes ago, Tennessee Boy said:

I’m a firm believer in switches that get turned off at the ramp before I head home.   It’s less important with LifePo4 batteries because the BMS should provide the same protections if it’s functioning properly.   Still,  switches are cheap and fires are not.

I didn’t even think about the fire issue. That’s all I needed to hear— a switch is getting installed. 

[stk44]

Could I run a 31 group AGM cranking battery or a deep cycle battery in parallel to the existing starting battery? I guess it would no longer be considered a house battery, but wouldn’t I be able to charge using my existing 3 bank charger, but at a slower rate? 
 

If this is a possibility, is there a downside other than the obvious extra space another non-lithium battery would take up? Might it put too much strain on the charger? 
 

thanks!

steve 
 

[gim]

3 hours ago, stk44 said:

I didn’t even think about the fire issue. That’s all I needed to hear— a switch is getting installed. 

 

In addition to the safety issue, a power switch also eliminates any kind of measurable parasitic draw from the battery too.

 

I have an on/off switch that came pre-installed on my Ranger.  One for the deep cycles/bow mount and a separate one for the cranking battery that powers my electronics, pumps, lights, etc.  I've actually forgot to switch them back on more than once and when I go to start my outboard, nothing.  Then I think "why isn't this starting" and remember the power switch is off.

[stk44]

2 hours ago, gimruis said:

 

In addition to the safety issue, a power switch also eliminates any kind of measurable parasitic draw from the battery too.

 

I have an on/off switch that came pre-installed on my Ranger.  One for the deep cycles/bow mount and a separate one for the cranking battery that powers my electronics, pumps, lights, etc.  I've actually forgot to switch them back on more than once and when I go to start my outboard, nothing.  Then I think "why isn't this starting" and remember the power switch is off.

I have a switch for both my 2 deep cycles and 1 on the starter. I’m am not 100% sure but I think my motor and my auto bilge are bypassed for that reason. I’m fairly confident of that with the autobilge but I am pretty sure I could crank the motor with boat switches turned off. 

[gim]

1 minute ago, stk44 said:

I have a switch for both my 2 deep cycles and 1 on the starter. I’m am not 100% sure but I think my motor and my auto bilge are bypassed for that reason. I’m fairly confident of that with the autobilge but I am pretty sure I could crank the motor with boat switches turned off. 

 

That's interesting.  Wonder why they are bypassed.  I know mine definitely aren't.

 

I also have a talon connected to my cranking battery.  If there was no power switch for that, I'd attach a quick-connect/disconnect for that as I've heard horror stories of a talon accidentally deploying while driving down the road.

[stk44]

11 minutes ago, gimruis said:

 

That's interesting.  Wonder why they are bypassed.  I know mine definitely aren't.

 

I also have a talon connected to my cranking battery.  If there was no power switch for that, I'd attach a quick-connect/disconnect for that as I've heard horror stories of a talon accidentally deploying while driving down the road.

 I can’t even imagine those things deploying accidentally on the road. I know when I turn the ignition on it beeps prior to cranking, but maybe the engine won’t start if the switch is off. With my luck I’ll try it out and smash into a dock. 

[gim]

3 minutes ago, stk44 said:

I can’t even imagine those things deploying accidentally on the road. I know when I turn the ignition on it beeps prior to cranking

 

I've never actually known it to happen, but the thought of it is enough to make me instill a switch to ensure that it never does.

 

I like the warning/beeping that the talon has when you start the engine with it deployed.  Its a good reminder not to throttle down with it deployed!