2004 280da battery switch wiring

J

JBFins22

New Member
May 14, 2013
48
Seekonk, MA
Boat Info
280 Sundancer 2004
Engines
4.3 MPI Mercruisers w/Alpha Drives
As I just noticed that one of my batteries is on constant charge on my maintainer, i'm thinking I should replace my batteries since i have 3 different deep cycle batteries. Got to thinking: Why is it wired the way it is?? 2 battery switches: 1 is for port engine starting only. 2 for house and starboard engine. Why not 1 starting battery for both engines on 1 switch that stays off while on the hook and 2 deep cycle on the other switch for house only??? There has to be a reason they would wire all of them this way. I thought it was hooked up wrong first, but I saw some older threads here that tell me they are all wired this way from SR. One more...what are some better batteries to buy? I have a blue top optima, an interstate, and some other off-brand i've never heard of. Would there be a problem/difficulty changing the wiring of the switches? Is it ill-advised? I have already replaced my charger with a ProMariner 30a 3-bank smart charger. Thanks guys!
 
They are wired that way so that even if you run the house down to nothing, you can still start the engines with one full battery. The emergency start switch bridges the two banks in case that happens. You are better off leaving it the way it is in my opinion. You can always add more capacity to the house bank if you need more time on the hook (I have done that with a pair of 6v golf cart deep cycles).
 
Normal applications will have dedicated starting batteries for each motor and generator.This is especially important if your ign systems are computer controlled.
This keeps the electrical systems seperate for true twin engine reliability.
Engine batters do not need to be on charge all the time, a working alt will provide the charging for engine batteries and house batteries while underway.
When on hook, house batteries should be isolated from the ships engine battery system.
 
Bt Doctur said:
Normal applications will have dedicated starting batteries for each motor and generator.This is especially important if your ign systems are computer controlled.This keeps the electrical systems seperate for true twin engine reliability.Engine batters do not need to be on charge all the time, a working alt will provide the charging for engine batteries and house batteries while underway. When on hook, house batteries should be isolated from the ships engine battery system.
Click to expand...
That's my point. I'd like to have both engines on a dedicated starting battery that's isolated from the house batteries. This way I don't need to use the transfer switch to start the starboard engine when the house batteries are drained. I should simply be able to start both engines from the isolated single high cranking battery on the single switch. So you agree with that but you're saying they aren't that way to protect engine electrical systems? Therefore, because SR seperates them (one on house bank, the other on starting battery bank) they have the transfer switch in the case that the batteries are drained? This happens often on most overnights due to the fridge and stereo being on.
 
Personally I believe you need to have the engines isolated from each other, that included starting batteries.the only safe way is to disconnect the alt from one of the engines so the charging systems dont buck each other. But now you just have a single engine charging system?Should that alt go bad ,now your not charging anything.
each engine should have its own battery due to the electronic components.each engine should have its own battery due to the electronic components.
Try rewiring the switch. I take car of a 28 Wellcraft Coastal with twins. Battery switches have been reconfigured to supply engine battery power as pos 1 on both switches. The house battery(s) to run everything else is isolated from one engines charging system thru an isolator. this charges both the engine and house while underway and isolates the house when engines are off.
What you could do is run a jumper from the #2 position to the house battery system.With no isolation system ,switch to both underway and switch to 1 while on the hook.
with an isolation system, set to #1 and forget it.
common of each switch to each engine
#1 position to each starting battery
#2 position to house battery bank
cable jumper from #2 to #2 on both switches.
switching to "all"(both) can now supply power from 3 batteries to get one engine started if needed.
rewiring a charging lead from the battery charger to #2 position will charge only the house battery unless you put the switch(s) on both(all)
 
Last edited:
Bt Doctur said:
Personally I believe you need to have the engines isolated from each other, that included starting batteries.the only safe way is to disconnect the alt from one of the engines so the charging systems dont buck each other. But now you just have a single engine charging system?Should that alt go bad ,now your not charging anything.
each engine should have its own battery due to the electronic components.each engine should have its own battery due to the electronic components.
Try rewiring the switch. I take car of a 28 Wellcraft Coastal with twins. Battery switches have been reconfigured to supply engine battery power as pos 1 on both switches. The house battery(s) to run everything else is isolated from one engines charging system thru an isolator. this charges both the engine and house while underway and isolates the house when engines are off.
What you could do is run a jumper from the #2 position to the house battery system.With no isolation system ,switch to both underway and switch to 1 while on the hook.
with an isolation system, set to #1 and forget it.
common of each switch to each engine
#1 position to each starting battery
#2 position to house battery bank
cable jumper from #2 to #2 on both switches.
switching to "all"(both) can now supply power from 3 batteries to get one engine started if needed.
rewiring a charging lead from the battery charger to #2 position will charge only the house battery unless you put the switch(s) on both(all)
Click to expand...

Ok, so it makes good sense to keep engine 1 and 2 off the same starting battery, hence why SR wired these boats like this. I probably won't make any changes to the configuration but now I'm presented with this: What type of batteries would be best for the 2 house/starboard starting bank? Here's my current battery situation. I have an Interstate deep cycle, which is junk. I have a Sportsman dual purpose and an Optima Blue top dual purpose. When I bought the boat in 2013 they were installed by the marina and I've just put them back the way they had them. I'm not even sure they knew the order they put them in, in fact i'm thinking they just tossed them in, in no particular order. So, what would be the best configuration, assuming I'm buying 3 new batteries. Battery 1, port starting, should probably, correct me if I'm wrong, a starting battery. Now for the 2 house (and starboard starting) batteries, i'm thinking it's best for 2 deep cycle batteries, mainly because they power house items 95% of the time. For those times, like overnights, when they don't have the juice to start the starboard engine, i use the transfer switch and use the ports starting battery. Does this sound like the best option?
 
The problem is that deep cycles aren't good at cranking, and cranking batteries don't like being deep cycled.

In my opinion, the AGMs offer the best of both worlds. They provide plenty of cranking amps, but don't mind being deep cycled (not as much as cranking batts anyways).

I bought 4 Duracell group 31 AGM's from Sam's club for $179 each. (I had to drive to Worcester since our locals are shutting down). On Sunday, I saw the Deka equivalent batteries at the Boston Boat Show for $350 a piece. I did quite a bit of shopping around in our area and found Sam's had the best prices and it was even worth joining for a year just to save money on the batts.

You may not even need group 31's, so you might even be able to save a few more bucks.
 
I was thinking the deep cycle would be better for more time but yes it does need to crank also. For the most part I never kill the batteries but once in a while on the overnights, it happens. I am definitely leaning towards the AGM, which all I can find is dual purpose AGM anyway. I just looked at Trojan, which are about $300 each. How are the reviews on the duracells? Also considering Odyssey over the Optima. I ready that Ooptima was sold some years ago and they aren't as good as they once were. I'm not afraid to spend a little more if I'll get more longevity and cycle life out of them as well. I wish I was able to tell how old my current batteries are but as they were replaced, nobody scratched the dates off the stickers at all. Regardless, I'll be going with 3 new batteries this year for piece of mind. Looks like 1 starting and 2 dual purpose. BTW, it sucks about Sam's closing our stores here. Glad that Worcester worked out for you.
 
Definitely sucks about Sam's closing in our area. (I'm near N. Attleboro, MA BTW)

Supposedly, the Duracells are just rebranded Dekas. They certainly look exactly the same and have a 18 month warranty. I haven't seen too many reviews on them, but everyone who has them has no complaints.

Even if you have to pay for a Sam's membership you're still ahead of the game. I would offer to help you out and lend you my membership card, but I've already got a refund so I'm no longer a member.
 
I'm going to check them out. That's funny, I'm in Rehoboth. Keep the boat in Barrington. Thanks for the info!
 
SmilingMonkey said:
Definitely sucks about Sam's closing in our area. (I'm near N. Attleboro, MA BTW)

Supposedly, the Duracells are just rebranded Dekas. They certainly look exactly the same and have a 18 month warranty. I haven't seen too many reviews on them, but everyone who has them has no complaints.

Even if you have to pay for a Sam's membership you're still ahead of the game. I would offer to help you out and lend you my membership card, but I've already got a refund so I'm no longer a member.
Click to expand...

I was looking for Sam's clubs inventory to see what they had. I can't find the dual purpose batteries there. Did you buy deep cycle? I've got an email into driveduracell.com to see who else sells them in our area. I do have a buddy who works for Cay Electronics in Portsmouth. Going to see if he can grab them for me too but I have a feeling the Sam's club price is the best deal.
 
All the brands I've been looking at have both deep cycle and dual purpose AGM batteries. I was trying to avoid buying dual purpose but since i start one engine with my house bank, other posters say I should use dual purpose.
 
that's a pretty weak "brochure" if you ask me :)

I wouldn't sweat it too much. I just went to the basement and took a look at my batteries. They say "Marine / RV Deep Cycle" on them. They also provide 1000CCA which is more than what my previous batteries had. Someone else I was talking with on this forum also uses the exact same battery to start his Mercruiser 8.1's. They should be more than enough for your motor.
 
SmilingMonkey said:
that's a pretty weak "brochure" if you ask me :)

I wouldn't sweat it too much. I just went to the basement and took a look at my batteries. They say "Marine / RV Deep Cycle" on them. They also provide 1000CCA which is more than what my previous batteries had. Someone else I was talking with on this forum also uses the exact same battery to start his Mercruiser 8.1's. They should be more than enough for your motor.
Click to expand...

My thoughts exactly. I did see that the cranking amps are up there. That's around what i'm at now but I have 2 different lead acid, unknown age batteries. Also, my starting is an Optima AGM and I don't think that's good for my charger, having different type batteries. I'm going to mull it over for a month and see what my electrician friend comes up with too. Still might just head to Sam's I can always grab them in Jersey since my father in law has a membership. I'll be there for Easter anyway!
 
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