Cracking and/or Deep Cycle Batteries

[AlexG]

I have a 2007 Sundancer 240, and all 4 batteries died. I didn't use the boat for a couple of months and it looks like the bilge pump stayed on and drained the batteries. (Yes, I will be replacing the bilge pump and looking for other potential issues.)

My question comes to replacing the batteries.

The boat has a switch where I can use 2 cranking batteries for the motor, and when the motor is off, I can switch it and use two other batteries for music, GPS, etc...

The boat currently has (these are the 4 dead batteries):
2 x Interstate 24M-XHD Battery 800 CCA 1000 MCA Reserve 135
2 x Interstate 27M-XHD Battery 800 CCA 1000 MCA Reserve 182

I am planning to buy:
2 x 24M 27M cranking batteries, and
2 x Interstate 27M-EFB Deep Cycle Marine Battery

The question is, if I would be able to use the deep cycle batteries to start the boat, or at least to charge the two cranking batteries if needed.

I don't know much about boats, which is why I had no idea the bilge pump would drain and pretty much kill my 4 batteries.

Any advice on the configuration I am thinking of, or should I be better off just buying all 4 batteries the same 27M 800 CCA 1000?

Thanks.

 

[RichieRitz]

I’d charge batteries if they are not too old and see if they hold a charge. Maybe still ok to use. Maybe float switch on bilge pump got stuck and left it running. Is pump burned out or what? I use a pair of the 24 deep cycle type and no issues so I’d say if that’s your choice I don’t see any problem with them.or your configuration. Fwiw. Oh I’d Stick with interstate. .

 

[Scott215]

If you use a good charger it will actually tell you what's wrong with it if it's good it'll charge it in a way that protects the batteries they're expensive they're like a smart charger I bought one and I have 5 years on my batteries and they are tip top

 

[Lazy Daze]

You said "it looks like" the bilge pump stayed on. Can you explain how you verified that? I ask because it it sounds like you might be guessing? Depending on the batteries age and their level of charge when you put the boat away a few months ago, they may simply have withered away and died from old age or insufficient charge.

Did you unplug the CO detector? That stays active regardless of the battery switch.

If the switch was installed correctly, it would enable you to use either bank of batteries to power the boat (both the engine and the house). Whatever bank is currently selected will ALSO be charged by the engine's alternator.

Selecting "both" on the switch combines the banks. Typically this is only used when both banks are somewhat depleted.

You absolutely don't need two starting batteries. It's actually kind of strange to have that.

A Group 24 starting battery (Deka is also an excellent choice) is plenty/perfect.

It's your call as to what you want to use for the other bank - it all comes down to your use of the boat when the engine is off. It's possible that one DC battery will be enough.

 

[ranger58sb]

2 x Interstate 27M-EFB Deep Cycle Marine Battery

The question is, if I would be able to use the deep cycle batteries to start the boat, or at least to charge the two cranking batteries if needed.

Those battery labels are likely slightly misleading. They're probably really dual-purpose batteries, designed to service both starting and house loads.

Only a few 12V batteries are "deep cycle" -- most deep cycle batteries are 6V and connected in pairs to 12V or 24V etc. A single Group 31 12V battery capacity might be about 100-Ah. A pair of GC2 6V batteries wired to 12V might give you more like 220-Ah capacity.

-Chris

 

[Lazy Daze]

Only a few 12V batteries are "deep cycle" -- most deep cycle batteries are 6V and connected in pairs to 12V or 24V etc. A single Group 31 12V battery capacity might be about 100-Ah. A pair of GC2 6V batteries wired to 12V might give you more like 220-Ah capacity.

-Chris

On a little boat, though, it is, by far, standard practice to use a 12V DC battery. Not that (2) 6V "couldn't" be used, of course.

 

[bobeast]

As long as the deep cycle batteries have sufficient grunt, you can use them for cranking. I guess, technically, you should use "dual-purpose" batteries. I've long held that "dual-purpose" is just a label, signifying said sufficient grunt.

I have all deep cycle AGMs without the label, and they seem to hold up just fine.

 

[Stee6043]

For what it's worth - I do recommend avoiding cracking batteries

 

[Scott215]

What's a cracking,you mean cranking i hope, I have 1 cranking and 1 deep cycle for house. Never had a problem

 

[AlexG]

What's a cracking,you mean cranking i hope, I have 1 cranking and 1 deep cycle for house. Never had a problem

Yes, I meant cranking.

 

[AlexG]

I’d charge batteries if they are not too old and see if they hold a charge. Maybe still ok to use. Maybe float switch on bilge pump got stuck and left it running. Is pump burned out or what? I use a pair of the 24 deep cycle type and no issues so I’d say if that’s your choice I don’t see any problem with them.or your configuration. Fwiw. Oh I’d Stick with interstate. .

I removed them from the boat and used a smart charger to repait them (https://www.amazon.com/gp/product/B097D397M6). One holds charge at 12.11, another at 12.16. The other two are just plain dead.
It's very possible the pump got stock and it stayed running. I haven't even removed it yet, but it stayed on until all 4 batteries were dead. I would think is safe to assume that it burned out.

I am planning on using 4 since that's what it originally came with. It was a good setup and it worked fine for a couple of months until this happened.

 

[AlexG]

You said "it looks like" the bilge pump stayed on. Can you explain how you verified that? I ask because it it sounds like you might be guessing? Depending on the batteries age and their level of charge when you put the boat away a few months ago, they may simply have withered away and died from old age or insufficient charge.

Did you unplug the CO detector? That stays active regardless of the battery switch.

If the switch was installed correctly, it would enable you to use either bank of batteries to power the boat (both the engine and the house). Whatever bank is currently selected will ALSO be charged by the engine's alternator.

Selecting "both" on the switch combines the banks. Typically this is only used when both banks are somewhat depleted.

You absolutely don't need two starting batteries. It's actually kind of strange to have that.

A Group 24 starting battery (Deka is also an excellent choice) is plenty/perfect.

It's your call as to what you want to use for the other bank - it all comes down to your use of the boat when the engine is off. It's possible that one DC battery will be enough.

The assumption is based on the fact that a couple of months after the last use, when I brought the boat home (I keep it at a yard), and plugged the shore power cord, the bilge pump light came on, but there is no sound from the pump running (assumed it burned out). All other lights were off, and the main selector switch was in the OFF position. The switch has 4 options: 1 for the motor, 2 for the house, Both, and OFF. (https://www.westmarine.com/guest-battery-selector-switch-universal-mount-without-afd-1240704.html)

When I bought the boat I was told the bilge pump was wired so that if there was water (or debris I guess) it would draw power from any of the 4 batteries to prevent the boat from flooding.

 

[Lazy Daze]

12.1 is a goner - it's a dead battery.

Check your wiring diagram, but I don't think the bilge pump is hooked up to all 4 batteries, is it? I could be wrong, though.

It's your boat so of course do what you want. But 4 batteries was not original equip. That's not to say that you can't improve or redesign the original equip. But 2 cranking batteries is overkill and, really, just a waste of money.

 

[Bt Doctur]

Personally I think your wired all wrong.You should use dedicated engine batteries, period!
The house battery should be a stand alone system. Battery switches can be configured to charge all batteries while under way.
You cannot "charge " a battery from another battery. You should have 2 bilge pumps connected as 1 pump to port battery direct ,and 1 pump to stbd battery direct.

 

[ranger58sb]

Personally I think your wired all wrong.You should use dedicated engine batteries, period!
The house battery should be a stand alone system.

Tell that to Sea Ray. And a large percentage of U.S. boat makers.

It's dead common to have dual purpose battery banks... for starting an engine and for servicing house loads.

Significant work to change it, with limited benefit.

-Chris