Multiple battery banks or one big one

[Terra Nova]

Originally Posted by Thorne

T...I meant wire size of 4 AWG...

Seems WAY light.

[Thorne]

Originally Posted by Dulcesuenos

1.c ranking for log periods of time is incredibly bad for a starter, might need.
2.. Most high torque starters draw alot less than their rating and only for a second or so if the engine is running properly.
3. Most people I know don't run the windlass for the initial drop or when weighing anchor without the engine running. Kind of negates worrying about a high battery draw.


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1. My motor cranks in about a half a second. Not the point.
2. This is a diesel , not a Honda. ( think HUGE compression, bigger starter amps )
3. Oh, I see, you carefully take the chain out of the windless and "throw the anchor overboard", then you let your chain free wheel out of the chain locker thru the chain guide into the water.... Uh,,,,, HOW?
In other words. Please tell me just how to do that and not break something, or while bouncing around on the waves or wind, even get the 60 lb anchor and attached chain out of the ... oh never mind.

Here is a simple video for reference on a smaller boat on how to use your windless. My boat has a much bigger windless, much heavier anchor, much heavier chain and toe switches on the bow instead of a hand held remote, but the principal and the rest is the same. Yes I have cockpit controls for single handing it.

https://www.youtube.com/watch?v=wf0vk2M5L6o

The bottom line is the further away the electric motor you are running is from the battery the more the "Voltage Drop" ( which means amperage increase, which means HEAT ) is across the wire. You have to increase wire size to allow for this. Otherwise "you can burn up your boat or the motor", I can't afford 0 AWG wire to go from the front of the boat to the back where the engine is ( not so much of a problem on a 19 ft. boat ), so I use a smaller diameter wire to only charge the forward battery.


For those following along at home, wire gauge "like shotgun sizes" gets bigger the smaller the gauge, Example: 0 or 1 is much bigger than 4 and 4 is huge compared to something like 12 or 14.

[Thorne]

Originally Posted by Terra Nova

Seems WAY light.

To try to actually run the windless, yes you are correct. I only charge the forward battery off the alternator using this wire.

I use the forward battery to run the windless.


Repeat of the above.
Wire gauge "like shotgun sizes" gets bigger the smaller the gauge, Example: 0 or 1 is much bigger than 4 and 4 is huge compared to something like 12 or 14.

[a64pilot]

A disadvantage of 2 house banks is your cycling the bank deeper than if it were one large bank, thereby shortening its life.
However if your Solar array were large enough and you charge both banks simultaneously I can see how having twice as many charge days as discharge nights may well get the banks to 100% every other day, will this more than offset the deeper cycle? I have no idea, it might?


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[noelex 77]

Originally Posted by a64pilot

A disadvantage of 2 house banks is your cycling the bank deeper than if it were one large bank, thereby shortening its life.

Not if you have both battery switches on .

I think the stumbling block preventing people understanding the advantage of two house banks. The common belief is that you can only use one or the other. In reality it is better to run both banks in parallel most of the time. This is easily done by switching both battery switches to the on position. In this position the house batteries function like one big battery bank.

[Dulcesuenos]

Originally Posted by Thorne

1. My motor cranks in about a half a second. Not the point.
2. This is a diesel , not a Honda. ( think HUGE compression, bigger starter amps )
3. Oh, I see, you carefully take the chain out of the windless and "throw the anchor overboard", then you let your chain free wheel out of the chain locker thru the chain guide into the water.... Uh,,,,, HOW?
In other words. Please tell me just how to do that and not break something, or while bouncing around on the waves or wind, even get the 60 lb anchor and attached chain out of the ... oh never mind.
.

You really missed the part about not using the windlass Without the motor running but I'm sure you get it now...well maybe not.
With your engine running there's less of a draw on your windlass battery. Why wouldn't you run your engine while operating the windlass? Except perhaps in an emergency
Ever watch you amp draw on your bank manager when cranking the diesel? Most do not draw any more than a microwave being used through the inverter. The difference is the starter draws for a second or two, the microwave for several minutes to half an hour or more, oh wait should I use a start battery for my inverter loads now😂
And by the way several twin engine cats over the years have come with only one start battery, and they were typically not centrally located. So we're those manufacturers wrong?
Seriously before saying foolish things you should re read and check it.

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[Thorne]

Originally Posted by a64pilot

A disadvantage of 2 house banks is your cycling the bank deeper than if it were one large bank, thereby shortening its life.
However if your Solar array were large enough and you charge both banks simultaneously I can see how having twice as many charge days as discharge nights may well get the banks to 100% every other day, will this more than offset the deeper cycle? I have no idea, it might?


Sent from my iPad Pro using Cruisers Sailing Forum

Yeah, that is the question I will attempting to find an answer to now that I have both banks hooked up at the same time....

I have 180 watts of solar ( yeah right, that's what the panels say anyway ) permanently mounted and another 450 I can temp mount and I burn about 250 watts per hour ( according to my kill-a-volt meter) during the day while working, give or take a bunch during coffee making or air conditioning operation or almost any other activity, so I'm fighting a losing battle anyway unless I put up the temp panels......

PAIN in the boat bottom....

So let's say we start at fully charged.

100% and we burn down to 90% during the nite. Then we charge back up to 100%.

using both banks I burn down to 95% and then charge back up to 100%.

"Repeat cycle 365 times" does that make the batteries last longer?

Seems like it would. Like I said, I'm game to give it a try.

Not going to make my house bank start my motor though, unless it is an emergency or run my windless, well maybe the windless, I haven't done the analysis on how many amps it draws.

https://www.batterystuff.com/kb/arti...ry-basics.html

read section 2.

[kmacdonald]

Originally Posted by svlamorocha

Go for one house bank. This was settled years ago

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Yes, for flooded lead acid batteries. For lithium batteries I"m not so sure.
We need a thread to debate it.

[jkindredpdx]

Anyone want to talk about a less heated topic... like composting heads, anchoring, or AIS?

[Dulcesuenos]

Originally Posted by Thorne

Yeah, that is the question I will attempting to find an answer to now that I have both banks hooked up at the same time....

I have 180 watts of solar ( yeah right, that's what the panels say anyway ) permanently mounted and another 450 I can temp mount and I burn about 250 watts per hour ( according to my kill-a-volt meter) during the day while working, give or take a bunch during coffee making or air conditioning operation or almost any other activity, so I'm fighting a losing battle anyway unless I put up the temp panels......

PAIN in the boat bottom....

So let's say we start at fully charged.

100% and we burn down to 90% during the nite. Then we charge back up to 100%.

using both banks I burn down to 95% and then charge back up to 100%.

"Repeat cycle 365 times" does that make the batteries last longer?

Seems like it would. Like I said, I'm game to give it a try.

Not going to make my house bank start my motor though, unless it is an emergency or run my windless, well maybe the windless, I haven't done the analysis on how many amps it draws.

https://www.batterystuff.com/kb/arti...ry-basics.html

read section 2.

So unless I am wrong the formula is watts ÷ voltage = amps. So if your burning 250 watts an hour as you said ( not including AC?, Or coffee making , at say 12.8 volts that's roughly 19 amps an hour your consuming. If night consists of 13-14 hours of no solar charging (7pm to 8am?) That's roughly 250 amp hours burned. To wake up in the morning with a 90% state of charge you'd need a battery bank of over 2000 amp hours. Or are you somehow charging at night and not running refrigeration and lights?
Somehow I'm thinking your a we bit confused.
If you have an average bank a 41 Morgan would have of 600-800 hours you'd be 50-65% state of charge at best and need every bit of all your solar in direct unobstructed sunlight for over 10 hours to get even close to 90%.
I think you should invest in a battery monitor and learn how to use it, otherwise you'll be needing batteries much sooner than later

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[Terra Nova]

Originally Posted by noelex 77

...The common belief is that you can only use one or the other...

Please...

[skipmac]

Originally Posted by noelex 77

Not if you have both battery switches on .

I think the stumbling block preventing people understanding the advantage of two house banks. The common belief is that you can only use one or the other. In reality it is better to run both banks in parallel most of the time. This is easily done by switching both battery switches to the on position. In this position the house batteries function like one big battery bank.

Hope there aren't too many out on the water that don't understand how this would work.

Other than the ability to immediately switch one bank out of the system in the very remote chance that one battery shorts, what advantage do you see for having two banks?

[HankOnthewater]

I am not really a fan of having 2 or more housebanks, mainly for the reason that a smaller (ie 50% smaller) housebank will result the batteries in that smaller bank to be much further drawn down.
For example, if all batteries (in one bank of ie 400 Amp hrs) were down 30% overnight (using 120 Amp hrs), leaving that one bank with 70% as SoC (state of charge), then half that bank (now 200 Amp hrs) with the same electricity use (120 Amp hrs) would be cause the batteries to be down 60% leaving that one small bank with SoC of 40%. Such deep cycling would reduce life expectancy of the batteries, more than needed in my opinion. But for exact figures one should check manufacturer’s information on the correlation between number of cycles (=life expectancy) and depth of charge.

Other than the ability to immediately switch one bank out of the system in the very remote chance that one battery shorts, what advantage do you see for having two banks?

Maybe direct internal battery shorts do not happen very often, but certainly not all batteries age at the same rate, and after a few years one could find a dud one in a big bank.

When all batteries are fixed wired, how would one know if one of the batteries is on its way out or develops a short.....? Yes, we could find a short by touching the batteries and the one that is hotter than the others will be a suspect. How often do we check the battery temperatures?
Maybe once a week we should aim an infrared thermometer at it? I must say, that I never done that, but such infrared thermometer is on my ‘to buy’ list for other reasons as well.

Or another (better?) way checking the health of each battery, is to install a switch or breaker between each positive battery terminal and the positive busbar. Then we could check the voltages of each battery separate. The drawback of this is of course complexity (=money) and introducing more resistance (voltage drop) in the connections and switches.

Of course the above can also be achieved without the switches: just disconnect all the positive battery terminals ie once a month, then approx. 10 to 20 hrs after that, check the voltage of each battery separately. Assuming all the batteries are of the same type and age, they all should be the similar within a very small range.

BTW can anyone check my correct use of “Amp hrs” units?

[Thorne]

Originally Posted by Dulcesuenos

So unless I am wrong the formula is watts ÷ voltage = amps. So if your burning 250 watts an hour as you said ( not including AC?, Or coffee making , at say 12.8 volts that's roughly 19 amps an hour your consuming. If night consists of 13-14 hours of no solar charging (7pm to 8am?) That's roughly 250 amp hours burned. To wake up in the morning with a 90% state of charge you'd need a battery bank of over 2000 amp hours. Or are you somehow charging at night and not running refrigeration and lights?
Somehow I'm thinking your a we bit confused.
If you have an average bank a 41 Morgan would have of 600-800 hours you'd be 50-65% state of charge at best and need every bit of all your solar in direct unobstructed sunlight for over 10 hours to get even close to 90%.
I think you should invest in a battery monitor and learn how to use it, otherwise you'll be needing batteries much sooner than later

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Actually I said "While working" .... Details are important.

[Don C L]

Hmm, these two sites might help some of us a little...
Deep Cycle Golf Cart Batteries For Power Storage
How to wire 6V Batteries in series or parallel configuration