Wiring Sanity Check - 2 Engines - 3 Battery Banks

[5teve]

Hi Guys

My boat has 2x cummins Diesels, 3 alternators (2 on starboard) and i'm looking to remove one of the alternators as it was placed by a previous owner on a bracket that looks very dodgy.

My intention is to use 2 alternators to charge 3 battery banks and I have a query with regard to shore power / genset charging use with a VSR.

Below is a rough diagram of the system (please excuse incorrect symbols)

House is a bank of 8x100ah dual use E-NEX DC31MF (AGM I think) batteries so 800ah - port and starboard batteries are 1100cca Bosch 31-1000MF Calcium and genset is a small Bosch 70ah battery

The VSR is bi directional

House is to Bank 1 on charger (up to 60 amp output as priority)
Port is to Bank 2
Genset is to bank 3

My concern is the following and would appreciate your input.

Under motor running all should in theory be ok apart from maybe the crank battery see's a high voltage when it should be in float from the alternator as when the VSR opens up it will dump the charge in to the house.

Under shore / genset use using the charger priority is given to house bank - but the VSR will no doubt open up as it his trigger voltage and let charge through to the starboard crank battery and then this may see sustained higher than float voltages for a large period of time while the house charges. Would you suggest wiring in a different way?

My thoughts are maybe the VSR needs to be replaced with an isolator (or the VSR triggered to work via ignition only - it has a terminal for this so only operates when charging motor starts) if an isolator is used the it would need to be wired with the charger going to start port - start starboard and house - and have a small 5a charger for the genset - I could charge the house with no back feed of voltage through the isolator.

Your wisdom and thoughts are greatly appreciated

Steve

 

[Portofino]

Does the alternator regulator with the engine running adjust the charge back to the “ crank “bank down as it tops it up anyhow ?



Have you got any X over switches ?
If not worth fitting .
You need one to rob the house bank if the crank bank is not powerful enough .An early sign they ( cranks ) are on there way out .
Ideally another x over on the geny batt circuit to nick 12 v from another bank .
That way you can allways start the geny where ever you are if the combined juice -for what ever reason is,not enough to fire up the main engines .

That’s what I have .

It’s tge CCA of 1100, not the Voltage that’s needed to fire the mains up - I think ?

Anecdotal - story time

With modern engines it’s not just turning the starter motor ,there’s a helluva lot of let’s call it juice needed to run the electrical black boxes and fuel pumps , injection controls etc etc .
Some times as the “crank “ bank starts to fail ,By fail not hold enough juice , it turns by ear - sounds ok ish - but will not fire .
Eventually bit like a duff car batt the cranking sounds slower on the nth attempt .

Gauge may say 26/28 V if a 24 V set up like mine ——- head scratching —— it’s down in CCA or juice - so don,t get hung up on the V alone - that’s what I,am saying .

This winter I used the x over to fire up my MAN 13 L jobbie s , just thought perhaps in a man in denial sort of way that it was because they had not been running for while .
Message to owner - in a spare minute check the terminals for winter corrosion etc ?

Off we went ,dull day fridges on music on , quite a bit of “ house “ on 50 min run .
Anchor in Antibes arrive 11am , ask the guy ( only punter that day ) @ the fuel pontoon if we could tie up for a few hours - had a few domestic chores in town to do .
One person stayed on the boat - house batts running down - no shore P .
Arrived back -@ 3pm filled up - with fuel - kinda thx for letting us wait etc - another 1/2 hr wasted .

Turn the key and errr errr errr , - slow crank .
Pressed the x over - faster crank , but not firing ! Getting slower after a few attempts eventually

Oops !
Now what skip ?

Simple start the geny , which it did .
Turn the charger only on
Look at the “ IN “ Ah gauge —- how much juice is going in .
Almost off the scale on the “crank “ bank and about 1/2 of the scale for the house .
Wait 40 mins - geny doing its stuff , watch the ‘ crank “ Ah IN gradually come down - heading to but not quiet float .
Take a educated guess “ there’s enough now “
Turn the geny charger off - leave it running - in case it’s not worked - give it a kettle to boil up on 220v outlets

Turn the keys - spin em up and they fire up .
Turn the geny off now !
Slip lines return to home berth .
Go off and buy new “ crank ‘ set batts #

Conclusion- although the V gauge indicated 26/28 V or what ever - looked normal , what I could not see ( I think ?) was if they were holding there charge .
There was not enough juice to turn and power up the various electronic stuff to start .
There’s no CCA gauge just V - that’s the point - don,t get hung up on the V

So you need a back up plan .
When they start to fail - holding charge - you arrive to find the charger on as it should be etc the, V where it’s allways been

# prob solved - they just burst into life within 3 secs now - and yes it did the usual connect checks .
Diagnosis- duff bats

 

[5teve]

Thanks P

Does the alternator regulator with the engine running adjust the charge back to the “ crank “bank down as it tops it up anyhow ?

- Good Question - I'm fairly sure the crank will drop as the VSR opens up as the voltage gets distributed to the House.

Have you got any X over switches ? If not worth fitting .

- Not drawn in to keep it simple - will have some - but location is tricky without heaps of wiring - as I dont have a rear bulkhead like many boats I have seen so no flat face to mount stuff on - I'm actually thinking of seeing if I can have one put in! Also a set of heavy jump leads will probably do the job too

You need one to rob the house bank if the crank bank is not powerful enough .An early sign they ( cranks ) are on there way out .
Ideally another x over on the geny batt circuit to nick 12 v from another bank .
That way you can allways start the geny where ever you are if the combined juice -for what ever reason is,not enough to fire up the main engines .

That’s what I have .

It’s tge CCA of 1100, not the Voltage that’s needed to fire the mains up - I think ?

- The CCA is the grunt (actually its the current - but CCA is derived from its ability to dump current fast)- but without the voltage nothing will happen anyway - Thats where this exercise is coming from - I am seeing 8v at the engine on crank due to too many connections - cheapskate manufacturer using thin cable and too long a cable run to port engine - 8ish meters? By remote switching and removing all connections - I can get the wires down to 2m max.

Anecdotal - story time

With modern engines it’s not just turning the starter motor ,there’s a helluva lot of let’s call it juice needed to run the electrical black boxes and fuel pumps , injection controls etc etc .
Some times as the “crank “ bank starts to fail ,By fail not hold enough juice , it turns by ear - sounds ok ish - but will not fire .
Eventually bit like a duff car batt the cranking sounds slower on the nth attempt .

Gauge may say 26/28 V if a 24 V set up like mine ——- head scratching —— it’s down in CCA or juice - so don,t get hung up on the V alone - that’s what I,am saying .

This winter I used the x over to fire up my MAN 13 L jobbie s , just thought perhaps in a man in denial sort of way that it was because they had not been running for while .
Message to owner - in a spare minute check the terminals for winter corrosion etc ?

Off we went ,dull day fridges on music on , quite a bit of “ house “ on 50 min run .
Anchor in Antibes arrive 11am , ask the guy ( only punter that day ) @ the fuel pontoon if we could tie up for a few hours - had a few domestic chores in town to do .
One person stayed on the boat - house batts running down - no shore P .
Arrived back -@ 3pm filled up - with fuel - kinda thx for letting us wait etc - another 1/2 hr wasted .

Turn the key and errr errr errr , - slow crank .
Pressed the x over - faster crank , but not firing ! Getting slower after a few attempts eventually

Oops !
Now what skip ?

Simple start the geny , which it did .
Turn the charger only on
Look at the “ IN “ Ah gauge —- how much juice is going in .
Almost off the scale on the “crank “ bank and about 1/2 of the scale for the house .
Wait 40 mins - geny doing its stuff , watch the ‘ crank “ Ah IN gradually come down - heading to but not quiet float .
Take a educated guess “ there’s enough now “
Turn the geny charger off - leave it running - in case it’s not worked - give it a kettle to boil up on 220v outlets

Turn the keys - spin em up and they fire up .
Turn the geny off now !
Slip lines return to home berth .
Go off and buy new “ crank ‘ set batts #

Conclusion- although the V gauge indicated 26/28 V or what ever - looked normal , what I could not see ( I think ?) was if they were holding there charge .
There was not enough juice to turn and power up the various electronic stuff to start .
There’s no CCA gauge just V - that’s the point - don,t get hung up on the V

Luckily for me my engines are the trusty old 6BTA cummins - so very little demand apart from glow plugs on start up.. all electronics etc are all run from house bank.

Re the voltage This is called surface charge - the ability for a battery to have sufficient voltage but not be able to delivery a) any current to the load b) not maintain the voltage under load

Out of interest why were your crank batteries effected by house loads? do you have a shared bank - house / start?

So you need a back up plan .
When they start to fail - holding charge - you arrive to find the charger on as it should be etc the, V where it’s allways been

# prob solved - they just burst into life within 3 secs now - and yes it did the usual connect checks .
Diagnosis- duff bats

- Fortunately all crank batteries are new - so hopefully wont have issues - but will be putting cross over at least between cranks - and may resort to jump leads for the house to crank as I doubt we would use this very often and couldnt justify the extra wiring and switching - something else to go wrong along the way!


I'm actually thinking of moving away from the VSR now and going for a FET Isolator - as this is only one way and in theory splits the charge where it needs to go (the VSR in ignition mode may also achieve the same thing with less modification of the wiring - as alternator BATT terminal wouldnt need removing and Alternator sense wire shouldnt come into play unlike with the Isolator) With the isolator I can also have the battery charger running house + cranks and have a small charger for genset battery as there is no fear of the isolator linking the 2 banks together due to the 1 way isolator

As per below diagrams

 

[Portofino]

Luckily for me my engines are the trusty old 6BTA cummins - so very little demand apart from glow plugs on start up.. all electronics etc are all run from house bank.

Re the voltage This is called surface charge - the ability for a battery to have sufficient voltage but not be able to delivery a) any current to the load b) not maintain the voltage under load

Out of interest why were your crank batteries effected by house loads? do you have a shared bank - house / start?
Quote -Steve

—————————————-//———————————————————

Crank and house are not connected- independent- except X - over switch on the helm which is spring loaded to off .

By “electronics “ I was referring to the stuff that runs today’s modern Diesel engines ,you will be surprised how much juice / “grunt “ V is needed - additional to the obvious starter motor .

As the “ crank “ batts slowly decay with time ,problem is - you can get into a situation wherby it turns over Ok - but will not fire - with modern engines .
I guess less so with more Mech pumped older engines ?

We had run down the domestic as well - unfortunately! Or they are getting shagged too , not offering much up when asked ??

Like the term “surface charge “ - sums it up .Can lead to a false sense of security with the crank set - that’s the prob .
I ,ve got V gauges on both banks - looked normal ,that’s the problem I highlighted.

Our geny too has its own little charger for its 60 Ah bat ( 400 cc yanmar diesel ) , it chargers its self up when it running ,from its 220v or when not running on shore 220v - from its dedicated little smart charger
Plus there’s a X over by it in the ER , if that batt fails to start it .

Again the practicality of nicking 12 v from a 24 v bank with jumpers - knowing its a last chance saloon .

I guess a set of BIG jumpers will do too as a “get you home “ for those without any form of X overs , but on a small boat like most folks out drive stuff in cramped/ hot - engine compartment s and in a choppy anchorage- the practicality of messing about with those sounds easier than actually doing !

We have Ah gauges of how much / how fast the main ( 80 Ah ) smart charger is pumping amps back in .
It’s by observing this I guess one can start to tell in normal use exactly how healthy the bat banks are .
So one can see when they are on float .

We only have 4 x180Ah ,diveded into two seperate independent banks -24 V system + tiny 60Ah -12 v for the geny
The CAA is 1100


Jumpers
Not a big fan - from auto experience.
Noticed if the donor vehicle is bigger and the jumpers not thick enough, they get hot and start melting the wire insulation
Not what you want with a dead engine (s) on a boat !

So I,am guessing if there are any boaters out there carrying auto motive shop jumpers - you could be in for a nasty a surprise if they use them on truck batts
Truck shop type NOT automotive car type .
Remember we are talking BIG batts here with big CAA .—- hence my suggestion to fit correct X overs

 

[5teve]

Hi Porto and everyone else.

Sorry I have been squirreling away while the boat has been out of the water (it still is) and also business has been keeping me busy. I have found some incredible stuff while dismantling the electrics and am amazed at the fact it ever worked (wire gauges far too thin to charge correctly etc)

As an update - i have worked on the diagram a little more and have notes and some concerns, which I cannot 100% find answers to. I'm hoping some brainy persons can help

as a refresh My aim is to have 1 crank (1000cca) battery per motor (330hp 6BTA's) 1 genset start battery (small 70ah battery) and 8x 100ah house batteries split into 2 banks (left and right hand banks) - may consider reducing this to 6 batteries to help with charge rates - advise will be welcome.

Firstly an updated diagram



Next

Hopefully you can see the detail and the notes. (excuse symbols as they may not be correct due to time constraints)

My main areas of concern were / are:-

• 800ah house bank - split into 2x 400ah parallel banks of 4 batteries. These banks are then paralleled to make the 800ah capacity total. output cables will go to a single point (either before or at the battery switch) to maintain same lengths on the cables - likewise the negatives will be grounded using the same length cable. I will pull + and - from opposite ends of the banks to help balance. I have researched this layout and can find nothing discrediting have 2 parallel banks of parallel batteries. - Thoughts?
• I wanted to use my 60amp 3 output charger to charge the house bank and the cranks. I couldnt do this with the VSR in 'normal' mode so it has an ignition sense so that it only operates when the ignition is on. When engine is off the 2 charger outputs are separate. When the engine is running, in theory the crank will charge and then open to the house - my only unknown (hence my post to persons far more knowledgeable than me) is if the house is depleted after a few nights away - the alternator could potentially dump 100+amps into the house bank via the crank battery - i'm not sure it works like this, but the crank battery certainly could see sustained high voltage when it only needs float - Again your advice would be welcomed.
• based on only having 60amps output from the charger (if the cranks are full it can output the full 60amp to the house battery) is 800ah overkill? or should I just have 6 house batteries and add the crank batteries in the LH / RH boxes along with the house batteries (frees up storage - saves 50kg and potentially shortens the cabling) all lighting is LED - albeit quite a bit of it- no inverter (yet) no real heavy usage other than the fridge (12/240v Engel upright - potentially 25-30ah per day) - I do have a chest fridge (converted from a freezer) which is incredibly efficient but 240v only - I may add a small inverter to power this but again from research it may only use 20-30ah per day even with the inverter in place. - Thoughts?
• I am assuming all negatives are common on the boat? So if i want to add a shunt for house only ( I have a wireless meter on its way) - I need to run the negatives (from each house bank) to the shunt terminal as a common point and then from the shunt to the 'ground' point?
• Finally - a contentious issue - the windlass - should I run it from the crank battery or the house bank? I honestly have no Idea where its connected to currently. I believe the schools of thought are that its only used while the engine is running - so crank is fine - others think it doesnt matter. again thoughts appreciated!

If you see any other issues with the above - please feel free to point them out.

Steve