Electronics die when cranking engine

[viper1216]

This seems to be a common issue and I found a bunch of things online about it, but want to make sure I am doing the right things here and am not the cause. Boat is new to me so learning all sorts of stuff lol. I have a dual battery system. Originally was having issues with battery number 1 dying all the time. (even after being hooked up to shore power and charging) Looked and found that both batteries were cranking batteries. So #1 got killed from running the electronics all the time since it wasn't a Deep Cell. So went out and got a Hybrid battery last week (now battery 1). Stays charged and haven't had any issues. Weather is finally cooperating and have been able to take the boat out. If I have my GPS on (Raymarine Axium 9RV) and go to start the battery, the GPS reboots. Same thing with my VHF. I have my battery selector on 1 at all times. (2 is still a cranking battery) Should it be on BOTH? Should I be switching back and forth all the time? I always thought the 2nd battery was there in case you ended up with a dead battery and could still start your boat. Maybe that is wrong. The selector is in the engine compartment, so while not huge deal to get access, it's not really ideal to have to open the hatch all the time to switch it back and forth. (My wife sits at the table that's on the engine compartment...don't wanna tick off the wife and make her move all the time lol) The engine is a 5.0 Mercruiser.

 

[mike_i]

I also have two batteries but have two switches, 1 switch for accessories 1 switch to the motor. You don't want your electronics connected to your starting battery, they're turning off because of the voltage drop when you're starting your motor.

 

[dingbat]

I've always used my electronics shutting down on "start" as an indication that my starting battery is in need of some attentive. i.e. not fully charged, getting weak, etc.

I run Deep Cycle batteries (grp. 27) for both "start" and "house" batteries. Increased battery life three (3) fold over the typical "marine" battery.

The trick is get a Deep Cycle battery large enough to supply the necessary CCA to met the demands of motor. My outboard requires min. 550 CCA. The batteries are rated 675 CCA each with 190 min. Reserve capacity. Can put 1,350 CCA on the starter using "Both" if need be.

Suggest you install a Blues Seas, "Add a Battery" kit to your setup. Eliminates the need to switch back and forth between batteries. Simply turn the Off/On/Both switch to "On" in the morning and "Off" when done. Charge both batteries automatically.

 

[JASinIL2006]

I used an Add A Battery kit to isolate my starting and house batteries. Before I did so, I'd have to restart my Humminbird fishfinder/GPS everytime I restarted the boat. (A pain in the back end when pulling skiers or kids on the tube.) Connecting the electronics to a different battery completely solved the problem.

 

[dingbat]

If I have my GPS on (Raymarine Axium 9RV) and go to start the battery, the GPS reboots. Same thing with my VHF.

Operating voltage of the Ray unit is 8.0 to 16 Vdc.

If your voltage is dropping below 8.0 volts during "start", you have an issue with your battery(s), Cables, Starter or all of the above. Normal drop is 10.5 to 9.5 V range

What is the recommended CCA rating for your starting battery?
What is the CCA rating of your battery?
What is the current fully charged, "resting" voltage of your starting battery?
When was the last time you load tested either battery?

 

[viper1216]

So I put the switch on BOTH to start this time. Which in theory is the new Hybrid deep cycle rated at 650cca and the "cranking" battery which is 800cca. GPS still shut down. I was connected up to shore power before starting with charger on so batteries are fully charged. And checked prior and both of them at 12.5v Weird. I mean, I guess I can just run the GPS power straight to the the battery..it has an inline fuse, but prefer running it to my fuse box like it's supposed to. Battery cable to the cranking battery seems a bit eh and loose at the wire crimp...so might replace that but I think the new battery should be plenty of juice to start this boat.

 

[mike_i]

You said "checked prior and both of them at 12.5v Weird'. If the batteries are connected in parallel ,+ to + and - to -, or with the switch in the both position, you'll read the same voltage since you are reading them as one battery. If you have any connections that are "a bit eh and loose at the wire crimp" you'll want to fix. You don't want any loose connections they may cause arcs and sparks, heat and are no good in wiring. Have you measured the voltage at the GPS as you start the motor?

 

[viper1216]

When I checked each battery and got the 12.5v, the switch was actually still on 1 only. I'm going to get a new connector for the battery, but it is on battery 2. Battery one looks ok. I'm also going to take the switch itself apart and make sure there is no corrosion there. Good idea on checking the voltage while starting. I'll try that and see what happens. I can actually just check power to the fuse panel and see what I get while cranking.