Two batteries, one switch?

[Clearwater262]

After reading other threads I am still a bit confused with my boats current battery set up.

I purchased the boat about a month and half ago. When I was test driving it, the alarm went off signaling low battery power. The previous owner said he would charge the batteries for me before I picked it up which he did.

I have been using the boat at least once, sometimes twice each weekend with no issues. Boat started up great and ran accessories while floating/anchored.

Yesterday while out cruising the alarm went off again. The radio and gps shut off. Gauge stated low battery power. Eventually the batteries died and I had to use the assistance of another boater to get to the dock.

My boat has two batteries and a single on/off switch. The switch does not have an option to switch between batteries. The batteries are connected together with battery cables.

I have two questions. First, how are my batteries being recharged while the boat is in use. Second, why would someone hook up two batteries together and rig up a switch that is only on/off? Seems to defeat the purpose of two batteries.

Attached below is not my exact switch, but an example of what type of switch I have. Other pics are my batteries which I'm guessing are shot and need replacement.

[badmoonrising]

First, if your battery is dying that quickly have it checked. If the battery is good, have your charging output (motor) checked. As for the on/off switch, that model is just as it says - to kill the battery power to the boat. A double pole switch has on, off batt 1, batt 2. Yours is just a kill switch.

[MH Hawker]

I think this is what you want

[Cycleman07]

What Hawker Said. Have that setup on my boat and it works flawlessly and gives you peace of mind.

[fergusmj]

Looks like if it is just that switch, you essentially just have one big battery. Are both batteries deep cycle? Or is one deep cycle and one a starting battery?

I would advise getting a different switch (as suggested) and also maybe look into a VSR (voltage sensitive relay). Usually having a 2nd battery is for a "backup" or house / starter setup to avoid killing your battery. With your setup, I think you will have power for longer, but still get a dead battery.

I'm no expert, so others may chime in and correct me.

[bassn386]

I don't believe deep cycle batteries are recommended for starting batteries.

[babock]

I don't believe deep cycle batteries are recommended for starting batteries.

I have a deep cycle that starts a 7.4L engine in my Wellcraft. For most motors that are on pontoons, they are fine.

[Clearwater262]

I have made the decision to install a new switch that can select either battery to run at once. In the meantime I purchased a Noco Genius G3500 battery charger/tender to keep my batteries up to par and I had originally planned on using only one battery at a time and switching to the other if needed, much like a switch would do. The batteries were showing in the 25% range according to the Noco Genius and I charged them to 100%.

I hit the water today to try the batteries. I first started with one battery only and the boat started strong and showed a strong reading on my volt gauge. As I was cruising around I began turning on my nav lights and docking lights. As I did this I showed a sudden drop on the volt gauge. My radio was also running at the time. I then tried my horn and it would not work with the other switches on. I turned off the switches and my horn worked. It appeared that listening to the radio while cruising and turning on my lights was bogging down the battery.

I then threw my second battery in and connected the parallel circuit (I think that is what it is). The volt gauge did not show the drop like it did with one battery.

I brought the batteries home and again hooked them up to my Noco Genius G3500 which began blinking around the 50% mark, however it quickly got the batteries back up to 100%.

I'm trying to post pictures but it says the files are too big. Any idea how to post them? How do I test my motors charging system? Thanks.

[babock]

With the engine running and measuring at the battery, it should be at least 13.5V

[Ezgoing]

I suggest you take the batteries and have a load test performed on them.

It sounds as if you are using the two batteries for everything on your boat. I would not recommend that. I have a cranking batter that is only used to start and run my engine plus handle the required running lights. The engine recharges this battery while I am running.

If you are using the same batteries for everything then you must be concerned about how long you are running your engine to keep the batteries charged. If you spend more time sitting than running, you will discharge your batteries.

I have three more batteries on the boat. These are deep cycle batteries. Two of them operate my trolling motor, the other one operates my fish finder and other equipment on the boat. I generally get 8 hours or more from these three batteries, but I spend most of my trolling while I fish. My fish finder stays on all day when I'm fishing.

So you definitely are not getting the run time you should from those batteries. Which is why I suggest the load test for them.

Here is a good link about batteries. http://www.batterystuff.com/kb/articles ... asics.html

[tommyz]

I have made the decision to install a new switch that can select either battery to run at once. In the meantime I purchased a Noco Genius G3500 battery charger/tender to keep my batteries up to par and I had originally planned on using only one battery at a time and switching to the other if needed, much like a switch would do. The batteries were showing in the 25% range according to the Noco Genius and I charged them to 100%.

This was a good idea. As suggested, having the batteries tested is a good idea too.

Unless the batteries were identical, and in identical condition (they aren't) they were probably charging at different rates. Having them connected in parallel and using 1 charger probably fooled the charger into thinking they were ready but one was not. A discharged battery can drain a charged battery because they will try to equalize voltage potential.

Your new charger is only 1 bank. Are you now charging 1 battery, then the other? Life will be better if you spring for an on-board 2 bank charger.

If you do upgrade, get a higher amp rated charger (5-10). It will recharge the battery faster, and your batteries will last longer.