Boaters too often go to their boats to find the battery too weak to start. There may be a slow electrical drain, accessories left on, or just an old battery. This has happened to me several times over the years. I recently purchased a 2004 Four Winns 18? outboard (180 Freedom O/B), with one battery. The Fish & Ski version of my boat does have two batteries, to accommodate a trolling motor, live well, etc. So, I decided to start out this boat with 2 batteries. It?s much easier than you would think.
There are many ways to do this, and I researched them. In recent years the technology has changed dramatically so that the new approach I used is faster, easier to install, and functionally much improved. Some of the earlier, low-tech ways save a few dollars but require you to manually switch batteries on and off periodically as you?re underway, which is unnecessary and if done wrong (accidentally switching to Off as the engine is running) can ruin your alternator. Here are my steps, at a cost of about $200 and about an hour or two to install. First, buy the materials. I got a Voltage Sensitive Relay (VSR) and Battery Switch combination (BEP Marine 714-100A), at a cost of about $130 from Amazon. From AutoZone I got two 32? red battery cables and one black battery cable (the ones with just a connection hole at each end), for about $15. Finally, I bought a Marine Starting battery to match my engine at WalMart (24 MS6, 625 amps), for about $70. If you go to West Marine for one-stop shopping, you can get all of this for about $75 more. The only directions you need are the simple diagram of how to hook the batteries together, which is included in the 714 package.
Here?s a link to the simple wiring: http://www.bepmarine.com/media/product/pro4d2e2e961425a.pdf All you do is connect the wires using the simple schematic, attaching the VSR green ground wire to a battery negative post. I left all the ?hotel load" wires where they were on the existing starting battery. So, I now have my original battery as Battery 1 and the new battery as Battery 2. If Battery 1 ever gets weak, I can just switch the dial to Battery 2 and start the boat. On mine, I checked the bilge pump operation and it works whether on Battery 1 or Battery 2, and even in the Off position. In the Off position neither battery cranks, and none of the dashboard switches work, but moving the bilge float still starts the bilge pump. I just leave the switch on Battery I and the VSR works automatically to keep both batteries fully charged.
I bought a 10? ratchet-type strap for $10 to tie the two batteries together, so that the second one won?t move around in the hold. Maybe you could use a bungee cord, but the ratchet strap works great. It requires about 4? of strap to circle the two batteries, and I just cut off most of the rest. The 714A VSR-Switch can just be left sitting in the hold next to the batteries, without attaching it to anything. You never really need to fool with the switch since it is automatic, unless one of the batteries goes dead. Then, you would just open the hold and turn the switch to Battery 2, which is always fully charged.
Here?s how it works. When you?re at the dock with the switch set on Battery 1 that?s the only battery connected to the starter and the hotel loads. When you start the engine and it runs for awhile the voltage increases on Battery 1. When Battery I gets to 13.7 volts the VSR closes a relay so that Battery 2 gets charged too. When you turn the engine off, the voltage on Battery 1 drops below 13.7 volts and the VSR opens the relay to isolate the now fully-charged Battery 2. It?s really a beautiful system, and I think the best way to go.
Finally, there are other ways to use switches for dual batteries. Some people get one battery as a deep cycle for running stereos and accessories, and switch to that when the engine is off. You can do that too with this arrangment, but I like two starter batteries since I don't use many accessories. Some people just buy the switch, which is only $30, instead of the $130 switch and VSR combination. This used to be the only way before they invented VSRs. They need to periodically switch between batteries as they're underway, and mount the switch in the open, which is not worth the small money saved in my view. You can also run both batteries together, with a 1&2 position, or turn the switch to Off for extended absenses, as long as the bilge pump is wired to work as mine is. Happy boating! George
There are many ways to do this, and I researched them. In recent years the technology has changed dramatically so that the new approach I used is faster, easier to install, and functionally much improved. Some of the earlier, low-tech ways save a few dollars but require you to manually switch batteries on and off periodically as you?re underway, which is unnecessary and if done wrong (accidentally switching to Off as the engine is running) can ruin your alternator. Here are my steps, at a cost of about $200 and about an hour or two to install. First, buy the materials. I got a Voltage Sensitive Relay (VSR) and Battery Switch combination (BEP Marine 714-100A), at a cost of about $130 from Amazon. From AutoZone I got two 32? red battery cables and one black battery cable (the ones with just a connection hole at each end), for about $15. Finally, I bought a Marine Starting battery to match my engine at WalMart (24 MS6, 625 amps), for about $70. If you go to West Marine for one-stop shopping, you can get all of this for about $75 more. The only directions you need are the simple diagram of how to hook the batteries together, which is included in the 714 package.
Here?s a link to the simple wiring: http://www.bepmarine.com/media/product/pro4d2e2e961425a.pdf All you do is connect the wires using the simple schematic, attaching the VSR green ground wire to a battery negative post. I left all the ?hotel load" wires where they were on the existing starting battery. So, I now have my original battery as Battery 1 and the new battery as Battery 2. If Battery 1 ever gets weak, I can just switch the dial to Battery 2 and start the boat. On mine, I checked the bilge pump operation and it works whether on Battery 1 or Battery 2, and even in the Off position. In the Off position neither battery cranks, and none of the dashboard switches work, but moving the bilge float still starts the bilge pump. I just leave the switch on Battery I and the VSR works automatically to keep both batteries fully charged.
I bought a 10? ratchet-type strap for $10 to tie the two batteries together, so that the second one won?t move around in the hold. Maybe you could use a bungee cord, but the ratchet strap works great. It requires about 4? of strap to circle the two batteries, and I just cut off most of the rest. The 714A VSR-Switch can just be left sitting in the hold next to the batteries, without attaching it to anything. You never really need to fool with the switch since it is automatic, unless one of the batteries goes dead. Then, you would just open the hold and turn the switch to Battery 2, which is always fully charged.
Here?s how it works. When you?re at the dock with the switch set on Battery 1 that?s the only battery connected to the starter and the hotel loads. When you start the engine and it runs for awhile the voltage increases on Battery 1. When Battery I gets to 13.7 volts the VSR closes a relay so that Battery 2 gets charged too. When you turn the engine off, the voltage on Battery 1 drops below 13.7 volts and the VSR opens the relay to isolate the now fully-charged Battery 2. It?s really a beautiful system, and I think the best way to go.
Finally, there are other ways to use switches for dual batteries. Some people get one battery as a deep cycle for running stereos and accessories, and switch to that when the engine is off. You can do that too with this arrangment, but I like two starter batteries since I don't use many accessories. Some people just buy the switch, which is only $30, instead of the $130 switch and VSR combination. This used to be the only way before they invented VSRs. They need to periodically switch between batteries as they're underway, and mount the switch in the open, which is not worth the small money saved in my view. You can also run both batteries together, with a 1&2 position, or turn the switch to Off for extended absenses, as long as the bilge pump is wired to work as mine is. Happy boating! George