Trojan Boat Forum

First of all a 400 watt stereo is rated at Peak output. Typically it's not going to be putting out anywhere near 400 watts. That being said even if it were running peak the entire time it's only drawing about 33 amps. Your batteries should be rated around 800 amp-hours (or more) so in theory you could run your stereo off one battery for an entire day and still have half a charge left on the battery. The issue with that is with our big block engines half a charge on one battery may not be enough to actually start the boat. Another issue with that theory is it bases everything off of 12 volts and as the battery dies the volts will drop and the amps used steadily climb. Lastly, my batteries are brand new but by next year they won't hold their full capacity and after 4 to 5 years they really won't.

The solar charge is kind of a joke for running anything. It's typically around a 2 amp trickle charge that you get off it. Running a stereo that draws around 30 amps you're hardly gaining anything by having a solar charger hooked up.

In any case though running your stereo off of one bank for the entire day shouldn't be an issue because you always have the second bank to start the boat. While we have a generator on our boat, we don't need or use it. I can see where if someone ordered that boat to keep on LOTO or Minnetonka (where we keep ours) they would save some coin by not getting a generator or inverter. It's just not necessary when every night the boat is on shore power and we are never more than 8 miles from our dock. If your on the ocean go big or go home! If your running on lakes, get four new batteries and run two per bank in parallel.

PS. We could keep going on this and get into discharge rates and more but for your stereo it's really not worth it. When you start pushing 3000 watts and want to run it without a generator then you'll have a little more research to do.

I have a few comments/tips; while engines are off, your stereo may be your biggest load, but boats can be power hogs; gps, vhf, sounder, blowers, lights, water pump, maybe head, maybe bait well etc etc. All these possibilities need to be considered if applicable. I have always stated that I am not a fan of the battery selection switch. What you intend or are going to try and remember to do so you charge both banks is to operate/manage the switch as mentioned. IMO, this is not needed. You would be better off, and minimize problems by completely isolating both banks, and bring them together only in a case where the crank battery does not start the engine. If set up and maintained right, a crank battery on it's own should start you every time. But leave that switch in there and you're setting yourself up to drain both banks one day. There are a few options for charging and maintaining separate banks that have been discussed which leave no possibility to forget returning a switch to the proper position and return to port safely. There are also a few better/safer options for bringing banks together in case of a dead cranker. The switch introduces one more thing to remember, and unfortunately I've seen the sesult far too often. Just ask the Coast Guard or towing companies what the bulk of thier calls are for; dead batteries and out of fuel! Use an ACR or make up a temporary emergency parallel switch of your own with a solenoid and a momentary switch at the helm; push the switch to parallel and start, then let it go and you're isolated again. It's what tons of manufacturers do now and in fact is what Trojan used to do back in the day...no selection switches just ON-OFF for each bank. If you must use a selection switch, make sure it's a newer vintage that "makes before breaks" or has a field terminal if you're going to switch it after starting the engine as you mentioned or you can say goodbye to the alternator. Don't connect anything to the battery posts but the battery cables, all other connections; chargers, pumps, etc should go to a terminal block or back of switch.

I think this is something like what Big D is talking about. Maybe in yours you could put all of the house stuff on one bank so the second bank is always untouched. On our boat it's wired just like this diagram and is stock from Trojan. Of course we have another battery (generator bank) that we can always jump from if both engine banks went dead, but I highly doubt that will ever happen on our small lake.

Close but the key difference is I don't like selector switches, you need to manage them to charge or isolate all banks. I prefer that be done automatically without having to give it any thought...one less thing to worry about.

Sorry if those look like selector switches. They are not, just On/Off switches (breakers) for the bank in our electric panel. I should also mention that even with the switches off our refrigerator and two bilge pumps stay powered but everything else DC shuts off.

Other than the emergency connect we have no way of connecting the two banks.

Big D in the diagram above I don't see any need to manage anything with the switchs in normal use . You have two sepreate systems charged by its own engine. The only thing I would like to see added is a switch to conect the bank together if needed ( other then the emercency start switch ) . Am I missing something ?

You would like it done automatically ? Are refering to the digram above ? (Just4play) or maybe your refering to the one by LLCD ? in that case I also would want a system that would charge both with no worrys .

prowlersfish wrote:Big D in the diagram above I don't see any need to manage anything with the switchs in normal use . You have two sepreate systems charged by its own engine. The only thing I would like to see added is a switch to conect the bank together if needed ( other then the emercency start switch ) . Am I missing something ?

If you were talking about the diagram of mine I should mention we have a way to connect the banks.... jumper cables . Figured if we ever really got in a bind we can use them to jump off the generator battery which is truly it's own system

EDIT: Wow, it's early. I just had to edit this because I had spelt which "witch"... GED here we come!

just4plaay wrote:Sorry if those look like selector switches. They are not, just On/Off switches (breakers) for the bank in our electric panel....

Yes I thought they were selector switches. The only other concern I would have with your set up is that you have two completely different types of loads being applied to the same battery. To ensure longevity, one should use a crank battery for starting and a deep cycle for house loads. Running both off one battery design is contrary to the type of load the battery was designed for. In a "Perfect" world, the engines would have their own cranking batteries and the house circuit would have it's own deep cycle batteries.

Paul, I realy like the emergency start switch; simple set up and nothing to remember after you finally get the engines running. Trojan used them before, and they have made a come back because the concept works. For auto chargingof more than one bank, do away with the selector switch and install one or two ACRs or diode isolators. Turn the key and go, then turn the key and come back...no more worrying/remembering about what position to put the switch in to start, to run, at anchor, return...that takes the fun and safety out of it for me.

just to butt in for a second. I have 2 batteries going to my motor, and the the deep cycle 6v golfcarts for the house. I think im confused here sorry. If My motor batteries were to ever fail. I could use my large house bank to jump the engine correct?

Yes you can Jeff, but not with jumper cables. There are a few different ways to do it but simple and inexpensive is to get an ignition proof solenoid, one cable to engine battery, one cable to house bank, run control wire from solenoid to the helm to a momentary push button switch, and power it up at the helm. For dead battery, hold the switch in, start the engine, then let the switch go. Charging both banks at the same time off one alternator but keeping them isolated from each other is where ACRs or isolators come in.

ok I thought that was what I was reading, I even drew a little picture. Im doing your ACR. The batt cable from house bank to siliniod to engine will be costly but well worth it. what gauge for control wire to helm do you recomend? And! do you wire this from the begging of the house bank or the end or does it matter what battery it goes on?

Jeff, if you put the solenoid close to the batteries, cable should be minimal unless your banks are far from each other, but solenoid needs to be ignition proof if in engine compartment. You could just pick up 12 volts at the helm for the control/switch side. We could get more complicated here but just keep it simple for now. The gauge really depends on the solenoid draw. Get the unit first, measure the distance from where you place it to the switch at the helm, then let us know what it draws and the distance, I'll let you know the wire to use.

here's a solution, those battery/ boost packs mechanics use, you can just leave it plugged in, or however to keep it charged, and if there is every a prob just break out (another thousand) the booster

or is this silly? On another note it would be awesome if you meet a fellow boater with the dreaded flat bat!

rooferdave wrote:here's a solution, those battery/ boost packs mechanics use, you can just leave it plugged in, or however to keep it charged, and if there is every a prob just break out (another thousand) the booster

or is this silly? On another note it would be awesome if you meet a fellow boater with the dreaded flat bat!

Just don't buy a cheap one .