aguyindallas wrote:
Perfect timing...I just finished adding my second battery and getting it all wired up to my Perko switch.
Here is my setup:
1. I had a 4 gauge, 10ft wire made to connect the ground from battery 1 to battery 2. Battery 1 still has the factory ground to engine cable.
2. I had a 4 gauge, 10ft wire made to connect battery 2 to the Perko switch. Battery 2 is on the port side, Perko on the starboard side.
3. 1 wire from the Perko terminal 1 to battery 1.
4. 1 wire from the Perko terminal 2 to battery 2
5. Common wire removed from factory battery 1 and put onto "common" terminal of Perko.
6. Left the "helm power" wire connected to battery 1 as it was from the factory. This allows me to not lose the radio settings whenever I switch batteries to the off position. I am not sure this is the smartest idea, as this would still allow a drain at the help if there was one to drain the power of battery 1.
I am told my setting is safe as long as the boat is not running while the switch is in the off position. When its running in the off position, the alternator is charging, but has nowhere to dispose of the energy it is making while its running. This is what I am told cooks alternators.
My worry in this deal is knowing when/if its safe to start the boat in the "all" position. Only when they are both to low to start the engine independently? Or is it also ok if battery 1 is nearly dead and battery 2 is fully charged? I am just worried that I am applying too much power in the all position and it will fry something.
My intention is to hit the water on day 1, using battery 1. I will leave it there all day, even while anchored and listening to music, led's on etc...IF it goes dead, I will switch to battery 2 to start the boat. When it is running, I will either switch to all, or back to battery 1 to be sure battery 1 gets a good charge on the ride back to the dock. On day 2, I would be running all day on battery 2 and reverse the process as needed. Since our boat is kept inside our garage at home, I can put a charger on it anytime needed. I am considering going to a dual battery on board charger also.
1. Current thinking (yes I meant the stupid pun) is to ground the second battery to the engine block, not the negative terminal on battery #1. I believe that this (along with terminal covers for both positive and negative terminals) is looked for should you ever desire a CG Safety Certification. As I understand it, the theory is that ground wire from the original battery to the engine block may not have been sized for both. Also, in your situation it probably would have been a much shorter run to the block which can impact the wire size and heat rating needed.
6. The helm power circuit has a couple things going on that deserve consideration. The stock bilge pump may be powered though the helm power switch. Unless re-wired, the Stereo Head unit is powered via the Helm power circuit. Navigation lights are powered via the Helm power circuit. If you drain the battery that these are hard wired to and switch to the other, these things will no longer be powered. If you also move the helm power circuit to the switch common position you might be better off given your intended use - but be careful, you bilge pump will be off when the switch is off, and as you mention, your radio presets will be lost when the switch is off.
You should be ok starting in the all position even if one battery is very low as long as you switch, then immediately start the engine. In other words, do not give the batteries much time to equalize, especially if your boat is fuel injected as the electronics are more sensitive to battery charge level at start. Once started the alternator should be able to provide enough amps to run systems and charge both batteries. It's only when a battery is *dead* and can not be recharged that the all or both setting is problematic. In that situation, you want to start and run on only the good battery - even if it took a bit of re-wiring on water to do so.
As far as your intentions go, you should be fine. Especially if you charge up the batteries between uses. Dual on board smart chargers are great, many can individualy sense and charge/tend each battery separately. They are also more likely to have the amp output required to charge two larger group 27 + batteries overnight. I have the Guest 16202 Dual On board Smart Charger on my boat. It can kick out 10 amps per battery (which I believe to be the minimum needed). Works great, I'd buy it again.
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The Blue Sea Systems Add a Battery package worked so well I didn't use my on board dual charger all season long, at least not until it was time to put the boat into winter storage. 