Need Help: Dual Battery set up w/ Cole Hersee 24059

Dual Battery set up w/ Cole Hersee 24059
Hi!
I don't know anything about boats, but I have bought a 1984 Bayliner w/ a 125 in it that I am thinking about working on. I found something on it that I am not sure about. It has a 24059 Cole Hersee solenoid on it, with wires dangling around, and two dead old batteries, one a starting battery that is 10 years old and what I think is a "dual pupose"(can be used as a deep cell or starting) type battery that is 6 years old. They are different, and that doesn't make sense to me. He had the batteries marked #1 on the 10 year old starting batt, and #2 on the other, not sure why. Wouldn't you want two batteries in parallel to be exactly the same and of the same age?

So what is the point of that solenoid? Is this some kind of parallel set up to increase cranking power? Do I even need to run two batteries? I think I figured out how they are connected(positive from each batt to a main post on the 24059, the two negative posts on the batts connected together, and the little post from the 24059 that is not connected to the ignition coil, it is connected to the negative post on batt #1) but I would rather not use two batteries because they are so dang expensive. This boat doesn't have an electric trolling motor or anything like that. It just has a Hummingbird 400TX fishfinder. No other electrical accessories besides the stock boat wiring that is all there.

Sounds like two different issues. The CH solonoid is simply an electronically powered switch. When a low current is applied to the two smaller lugs, it closes the circuit between the two larger lugs. Typically, you use that to apply high current to the starter motor to crank the engine. If you trace the wires, it is likely that one the wires from the small lugs goes to #1 battery positive terminal (or possibly #1 battery ground) and the other wire goes to your starter switch. When to activate the starter switch, it completes the circuit, which activates the bigger switch in the solonoid. Trace the wires from the larger lugs on the solonoid, and one will likely go to the battery positive and the other will go to the starter motor or whatever else is being activated by the solonoid.

You should also have a battery switch. Typically that set up allows you to isolate a cranking battery to do just that - run the starter via the CH solonoid. The other battery is used to run all accessories - GPS, VHF, lights, panel gauges, etc. The battery switch should have four positions - all off, battery 1, batteries 1 & 2, and battery 2, in that order, going from right to left as you face the switch. I would replace the batteries because they are likely too old to be reliable - it's a real bummer to be caught in the middle of the water with a dead battery. I would also replace the battery switch, if there is one, or install a battery switch if there is not one. They have a bad habit of failing over time, especially in a saltwater environment. When running the motor, and with the battery switch in the third position (batteries 1 & 2) your generator will charge both batteries. When stopped, switch to battery 2 only. This will keep your cranking battery (#1) from discharging and assuring you have sufficient power to crank the engine.

Thanks for the reply!! What you said makes sense. I am not seeing a battery switch of any kind, just the solenoid. And I believe it was hooked up as you describe, but I can't be sure, the wires were all disconnected when I got the boat. I'll look for some kind of manual switch, but I'm pretty sure that one does not exist. Without a switch, does the alternator just charge both batteries at the same time? That is my concern with this set up, with the way it was. It doesn't make sense to have two different types of batteries hooked up that way, like the last guy had. Wouldn't one always be under or overcharging, depending on the type it was, and therefore ruin the batteries?? Wouldn't it put undue work on the alternator as well? I guess a switch would alleviate that problem, and allow me to run a deep cell for the fish finder, and a starter battery for cranking. The other option in my mind, not involving adding a switch would be two identical batteries, to avoid any over or under charging issues. I think that would work fine with this set up, and cause no problems. Most of my "knowledge" of this comes from dual battery set ups I have seen in offroad trucks with lots of accessories like winches and crap. And it's from memory, so I could be very wrong. AND, my other thought is, take the solenoid out, use a very nice starting battery, and not worry about it. How much load could a Hummingbird 400TX fish finder draw? Enough to justify an extra battery? Doesn't seem like it to me, but I am guessing that is why the #2 batt was added, if it wasn't added for extra cranking power at start up. There could be long periods of trolling with just the outboard running, and theoretically you could draw down a starting battery far enough to harm it?? I dunno, the whole thing is confusing me, that's why I'm here. I was hoping someone had seen a setup like this, maybe it was a common thing?? How it is seems like some kinda rinky dink trick set up, and I just can't seem to understand the thinking that got it the way it is.

Oh! I should say, I AM going to add a switch, as you suggest, if one does not exist. What you said makes perfect sense, thanks!!!

It is possible that solonoid is not for the starter motor. When you say the motor is a 125 in the Bayliner, are you talking about an outboard or inboard with an outdrive? If an outboard, the starter motor should have its own solonoid mounted on the starter. If it is an I/O, then the solonoid is likely a starter motor solonoid.

Basically you need to map out all the iginition wiring and figure out what does what.

Yes, it is a I/O, and the positive wire from one of the small posts on the solenoid is connected to the ignition coil at the main engine. The other small post has a wire on it too, that I believe is supposed to be atattched to the negative post on batt #1. The outboard is a Honda 9.9, that has wiring for a trolling speed control box at the steering wheel, and that is all. The trolling control box is connected into the other wiring of the boat, and not directly to the batts or the solenoid.

Okay - I really can't give you much more advice because I can't see the set up. It sounds like all this has been gerrymandered around for a specific set up. My best advice is to get a marine mechanic to unravel the whole mess and wire it up correctly.

I think that is some good advice! Thanks

Sounds like a klugged attempt at an ACR setup. What ever you do, make sure marine grade electrical components are used - they aren't cheap but are cost effective in the long run - wire, terminals, etc.

I prefer the ON-OFF type of switches as they are much more 'idiot proof' than the off-1-both-2 types. The ACR scheme is another approach to 'idiot-proofing' the electrical system. May want to get one of the 12V marine wiring books to explore your options - one by nigel calder is a classic reference.

Thanks very much for the comments and the reference material!! I am going to study up on it today, I have been looking at lots of info related to this, and it seems like this was a cheezey way to set up for two batteries in parallel, without a for real switch. Well, I am going to add a switch, so the potential problems I was imagining with charging will be solved. I believe the guy who installed the second battery was just trying to do it as cheaply as possible. I do still question the need for two batts on a boat like this, especially how it was set up, witha fish finder as the only accessory. I don't see how the fish finder justifies the existence of the second battery, but maybe it does. I sure don't know, and I have yet to talk to a boat mechanic. I am thinking maybe we will be using this boat for a bit of sturgeon night fishing, so if I add a bunch of lights for that, I can definitely see the need for an extra battery. I do understand why starting batteries should not be used for anything that draws a significant load, besides starting of course.

I would not take a boat out on the water without a working VHF capable of 25 watt transmission output. And if you are fishing a nightime, then a GPS would also be necessary, although that can be a portable.

Yes, I agree completely! THanks for your advice