This is UNBELIEVABLE!

[km1125]

Source of the post .....
Bottom line: draining a starter battery over 50% causes damage and becomes dangerous. Use a house battery to avoid that from happening.

There's nothing magic about the 50% mark. Any lead-acid battery likes to be fully charged. Running them down decreases their life and it's almost a linear scale. The 50% mark is used as an economic balance between useful life and capacity. There are plenty of charts available from manufacturers on depth-of-discharge (DOD) vs "cycle life", which is the number of times that battery can be expected to preform reasonably while being discharged to that percentage. If you look up those charts, you won't see any significant change from 40-60%, just a continuation of the same line from 10-90%.

Since a starting battery typically has a smaller AH capacity than a deep cycle, then draining the same amount from each would result in a much larger percentage from the starting battery. However, if you used two batteries with the same AH capacity, then you could draw the same percentage of each and get very similar life out of both of them.

[Phrancus]

hmmm, often mentioned 50% as a rule of thumb I understand but

do I understand correctly that the only difference between house and starter batteries is the Ah capacity in the same physical volume?

No difference in internals as to deliver a higher CCA and for house to not short out when drawn flat?

[Viper]

The main difference in construction is the thickness of the plates which vary by lead acid battery type. Deep cycle designs have thicker components such as plates and separators. The combination of these traits naturally allow for deep discharges at lower current levels. Thinner plate components are better suited for short high current bursts required for starting an engine or running high amperage accessories like thrusters.

The two different types of construction by their very nature perform better for their specific load type. That's why I'm not crazy about DUAL type batteries. The construction of the internal components is modified to accommodate both high current bursts and deep discharges. This modification however has no choice but to be a compromise at best between good cranking and good deep cycle functionality.

[KyleR]

I wouldn't be surprised if the cables simply got hooked up wrong in the Spring after a Fall disconnect for the winter.

The batteries are all in a row and the cables are exactly the length necessary so it would be impossible to hook them up incorrectly without actually swapping/moving the batteries. But for some boats that could certainly be a possibility.

[Phrancus]

That's the best way to set it up, perfectly at length or also functional by fixating the cables near the connecting points so they don't all get pushed aside into a heap of spaghetti when doing some other job.

[MadHatter]

So here’s a dumb question…
I have a 4207 and I replaced all batteries and cables. Drive the boat from redwing MN to mobile, no issue. But the last 100 miles I started seeing strange things on my volt meter readings.
Are there separate starter batteries from the 4 bank house batteries?
I guess I could just follow the starter cables but thought it would be a good first question.

[pepmyster]

No dumb questions. You will find, presuming they are gas engines, each motor has their own starter battery, 1 tied in to the Starboard engine for the bow thruster (pretty sure it's the Starboard, could very well be the Port), and the house are separate and the the genny is also on it's own.

[km1125]

Source of the post So here’s a dumb question…
I have a 4207 and I replaced all batteries and cables. Drive the boat from redwing MN to mobile, no issue. But the last 100 miles I started seeing strange things on my volt meter readings.
Are there separate starter batteries from the 4 bank house batteries?
I guess I could just follow the starter cables but thought it would be a good first question.

You should really start a new thread on this, or you'll get answers that confuse your situation with the OP's.

It's hard to say with a "vintage" vessel, as so many things could have changed by previous owners. I agree with pepmyster that there are probably dedicated "start" batteries for the engines, but one side might be combined to act as both a house and start battery.

But, I also want to hear more about that trip!!

[bud37]

Source of the post So here’s a dumb question…
I have a 4207 and I replaced all batteries and cables. Drive the boat from redwing MN to mobile, no issue. But the last 100 miles I started seeing strange things on my volt meter readings.
Are there separate starter batteries from the 4 bank house batteries?
I guess I could just follow the starter cables but thought it would be a good first question.

Welcome to the forum...... Good practice will be to map out your system and check wiring routes and connections as they are now first....I agree with above, things can change over time.

[paulr]

I took possesion of a Carver 396 Aft cabin yesterday, The previous onwer said all the bateries are old and should be changed.
I would like to change all 5 batteries but have not had time remove the cover plate yet and look at the yet. Hopefully the batteries are labeled at to what they are for.
Starting fresh, what would the proper batteries to buy for the engines, generator and house batteries ?
Im assuming the battery chargers were never updated to charge AGM so I will replace then with lead acid batteries.
Any thoughts?