Starter battery VS. Reserve Battery

[ontherocks83]

My head hurts now

[David M]

The design philosophy is to have a bank of batteries in which all of your loads draw from. You also need a battery to start your engine in which nothing draws from except the engines starter motor. Same with your generator if you have one. You then have a battery combiner or a battery isolator so that your house loads cannot draw from your engine or generator start battery but yet they can be charged when the alternator or battery charger is running.

Doing this will dramatically reduce the chance of being dead in the water where you cannot start a source that charges the batteries.

Or you can frequently move switches and hope you don't forget something on time or make a mistake with a switch setting.

It is somewhat of a complex system but helps to reduce human error.

[ramblinrod]

Originally Posted by rom

So you still have "dead lead" on board, don't you ?

No.

Under normal circumstances, (house bank within normal duty cycle range) all batteries are used to supply house loads 24/7.

Only in the unusual circumstance that the house bank is accidentally discharged below the normal duty cycle, is the reserve battery disconnected from the house bank, to preserve starting capability.

Instead of a house+reserve (or house+start) you are advocating house+bigReserve connected permanently and where you need to carefully setup the LVD to a voltage that preserves enough dead lead to start the engine(s).

No. This is not what I advocate.

I advocate using all of the batteries on board to supply house loads and start the engine under normal circumstances, and only isolate one (or possibly more if needed) deep cycle batteries from the house bank to preserve starting capability if the boater screws up and attempts to discharge the house bank too low.

It is not a case of "careful set-up".

A Blue Seas 7635 m-LVD does the job with default settings.

Just connect it between the "reserve" deep cycle (connected directly to the starter) and the rest of the house bank. Done. (Suitable for vessels where the reserve battery contribution to the house bank is 65 A nominal or less.)

More than that you are adding a big balancing issue between each single battery.

No balancing issue.

[Q Xopa]

Originally Posted by ramblinrod

Because boaters, even really smart ones, sometimes make mistakes.

A manual system is fraught with risk of human error.



The system I proposed is automatic, nobody has to present, astute, or even alive, to prevent discharging batteries to the point the engine cannot be reliably started.

Operating a 1/2/B/off switch based on SOC monitor and/or alarm, requires someone to be there and take action.



Dead lead is not the end of the world.

But if one has batteries they paid good money for, that take up valuable space, and slow the boat down due to additional weight, I recommend using them to ones best advantage vs just carrying them around "just in case".

Yes, some spares carried aboard are dead weight until they are needed. So is a dedicated starter battery. But if one can easily configure a reserve battery so it supplements the house bank under normal conditions, and starts the engine under normal conditions, and only is isolated to preserve starting in abnormal (heavy house bank discharge) conditions, I just don't see any down side.

It's akin to putting an alternator and H2O heating loop on an auxiliary engine. The auxiliary engine could be used solely for propulsion, but why not also use it for charging batteries and heating water when it can be done so easily.

Yes I agree that this idiot given half a chance is gonna mess it up.
IMHO is much better than having the system automatically kill my House bank.
My preference is a warning buzzer 'wake up dopey' (me) and switch your motor on/ switch the fridge off etc before your house bank is dead.

What happens in your setup if the reserve bank has a shorted cell? I think it will drag the house down until disconnect. Id say seperate banks would be better in this case as the house wouldnt get dragged down needlessly. Admitedly not terribly likely, but you stake your customers safety and wallet on that not happening?

Yes I also agree get double duty out of everything you can. Im all for engine alternators and water heaters. No argument from me there.

[rom]

Originally Posted by Q Xopa

What happens in your setup if the reserve bank has a shorted cell? I think it will drag the house down until disconnect.

I can't wait to read the answer.

@ramblinrod, can you define the word "normal" which you have been using a lot in your last answer ? I sometimes pump .3C to cook a chicken in my MW/grill combo. I suspect I am not normal. Also, may I ask you if you understand and/or have witnessed balancing issues ? I did, 4P system, same batteries as mine, poor balancing, very tired after only 2 years. I do maintain, parallelizing 2 banks(unless exact same) is asking for trouble. Trouble will come later if your "normal" use is .01C of course, but then you probably have a lot of dead lead

[thomm225]

Originally Posted by ontherocks83

My head hurts now

You don't really read all that crap when they get to arguing do you?

Many times folks will resort to alternative facts and hope someone will agree with them just to one up the other guy

[ontherocks83]

Originally Posted by thomm225

You don't really read all that crap when they get to arguing do you?

Many times folks will resort to alternative facts and hope someone will agree with them just to one up the other guy

No just skimmed for a minute then skipped to the end. My original question was answered by page 2 so I'm good.

Other than that it seems to be an appendage measuring contest now.

[ramblinrod]

Originally Posted by rom

I can't wait to read the answer.

@ramblinrod, can you define the word "normal" which you have been using a lot in your last answer ? I sometimes pump .3C to cook a chicken in my MW/grill combo. I suspect I am not normal. Also, may I ask you if you understand and/or have witnessed balancing issues ? I did, 4P system, same batteries as mine, poor balancing, very tired after only 2 years. I do maintain, parallelizing 2 banks(unless exact same) is asking for trouble. Trouble will come later if your "normal" use is .01C of course, but then you probably have a lot of dead lead

Normal means normal, opposite of abnormal.

You are trying to find fault in a solution that. Is not faulty. I do not care if does not suit your personal use case.

[thomm225]

Originally Posted by ontherocks83

No just skimmed for a minute then skipped to the end. My original question was answered by page 2 so I'm good.

Other than that it seems to be an appendage measuring contest now.

That's what some call cruising.

They buy a boat and sail a bit (or motor the ICW and call it sailing) then argue on the internet from an anchorage near 4G or at a marina

What else are you going to do in those situations as a retired person if you are not actually going to cruise (sail) your boat to distant lands and don't own a home to maintain

It can be sort of depressing since we weekend warriors (hoping to cruise one day) can pretty much do the same thing. We sail across bays be they 5 miles or 30 miles then argue on the internet during breaks at work with so called "real" cruisers.

Also, this can be done by the owner of a $2,000 boat, a $250,000 boat, or from a person that has never even owned a boat or been on the water much but still gives advice to new sailors and old

[Q Xopa]

Originally Posted by ramblinrod

Normal means normal, opposite of abnormal.

You are trying to find fault in a solution that. Is not faulty. I do not care if does not suit your personal use case.

'It is not faulty'. Good answer.
Nothing to see here folks, move right along.

Guilty, yes you are right I do try and think how what Im doing can bite me later. Aviation maintenance throwback I guess.

I conceed you win. You say its right for your use case- Great.

Best of luck to you.

[EmeraldCoastSailor]

Interesting thread; I have thought about re-configuring my starting batt arrangement to the reserve approach but haven't done it even though I just invested in new monitor, charger, 24/7 bus bar, solar, large inverter, and other things electric. Long ago I introduced a way to keep the start batt isolated (via a switch) from shore power charging to prevent abuse since I run my engine a good amount and my engine starts with ease. My thinking is that I know my starting batt is in good shape via moderate engine charging and constantly being tested when I start the engine and check voltage. If I had a reserve battery I'd have to test it regularly to make sure it was worth having; something doesn't seem right about that approach - why not just have a start batt? But I appreciate learning of other approaches.

[mikecambrai]

After nearly 60 years of owning boats I always err on the side of having redundancy at all times.
1. The engine is independent of everything. If you have a calorifier fitted then it must be able to be isolated with a valve at each end.
2. The engine has its own independent starter battery sized to take the CCA of the engine,
3. All batteries are either Gel or AGM. Reason? I have lost more batteries through not topping up in time then anything else,
4, All battery outputs should go through a 12B isolator so that you can go dead ship just by turning of the isolator which should be on deck for safety and make sure that you have not added some wire to the battery to bypass the switch if you don't want to find your battery dead when you least expeect it.
5. Fit a pair of cheap voltage meters from ebay/amazon so that you can always see what is happening as you walk by,
You have enough to worry about without worrying about the batteries.
This is based on some bitter experiences!
KISS

[MVDarlin]

I use "both" to start. At anchor I use house only overnight. To be sure the start battery is isolated I added a separate mechanical switch on the battery box. Nothing worse than having dead battery at remote anchorage. House bank is 11 optima batteries. Start bank is 3 Optima batteries. U have 50 amps of solar power panels to charge all.

[Dockhead]

Originally Posted by rom

. . . Also, may I ask you if you understand and/or have witnessed balancing issues ? I did, 4P system, same batteries as mine, poor balancing, very tired after only 2 years. I do maintain, parallelizing 2 banks(unless exact same) is asking for trouble. . . .

I think all the real pros will agree, that parallelizing battery banks, EVEN if exactly the same, is asking for trouble. Where is MaineSail?



You can count me as one more person besides yourself who has experienced these problems in real life. Although my two 210 amp/hour (@24v) battery banks are exactly the same, just a little bit of cabling is enough to mess up the balance.


Poor balance means some cells get chronically overcharged and some get chronically undercharged, which kills them.


Problems I've had from this are exactly why I'm going to a SINGLE lithium bank with no parallel cells.

[EmeraldCoastSailor]

I forgot to mention that I technically carry a reserve in addition to dedicated start and separate house bank. My reserve is one of those jump start lithium things that go for about $100. I have never used it so I don’t know if it would turn over my 3YM30. Hard to test it with a good start batt and I am not purposefully running my start batt down just to test it. Back up after the jump starter are jumper cables just long enough to reach start batt from house bank.