Battery Quandry

[Phil23]

I am running 2 house batteries, adequate but can always use more plus 2 starter batteries each 90cca 100ah. I don't think my starters get enough pull and constantly seem to be only holding 12.3 12.4 volts after a stand down period of approx. a week.
Wondering, as I have just installed 2 new house batteries it would be worth considering adding a third while all will be the same age and run one starter. My motor starts after no more than 2 to 3 revolutions even having sat for a couple of weeks.


Any thoughts??

 

[Phil23]

Oops 900cca on the starters

 

[BruceK]

Here`s a little sheet on battery voltage/fullness. https://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf.
Your start batts seem to be falling to 70% charged in a week of no charging. If they are flooded LAs with caps, try a hydrometer test, easy to do. If sealed, what does the "eye" "thingy" show?
On face value they seem to be discharging without load below what might be expected. Yet they appear to be starting the motor(?s) no problem.
Within reason,always worth having more house battery. What is the charging arrangement between house and start? What gets charged first, what regulates that?

 

[SteveK]

Phil,
How about some more info. Too much left to the imagination.
You have two start batteries (are they same type 900cca and what age), Two house batteries (2 same 100AH, are they same as start), starters (2?) and then my motor (1 or 2)
If you have twins then one can charge start and the other the house. Of course how fast they charge will depend on the amps the alternators can put out. You do not appear to have a maintenance charger.

what is state of charge after a trip, when you walk away from the boat for a week. Hydrometer reading.
Have you got an inverter/charger with 3 stages for house batteries?

 

[OldDan1943]

The start batteries are isolated and dedicated to starting the engines only, with some exceptions which seems to be an individual's and or builder's decisions ie aux equipment supporting the engine. IF you have a problem starting the main engine don't forget that 'magical' switch that will bring all batteries temporarily in parallel.
With electronic engine control, you will have to run parallel until you can either get the engine battery to 'near full charge', (above a bare minimum of 11vts and ideally above 12vts and increasing). This is obviously accomplished via the engine alternator or the main charger via the generator or shore power.
DON'T FORGET to open the battery parallel switch when things are approaching normal.
Investigate WHY the engine start batteries failed and replace as necessary.
Per the recommendation of replacing all the batteries at the same time, yes it is a good idea if you have the money. You must replace all the house batteries at the same time time.

 

[Phil23]

I guess my real question is do I in fact need two starting batteries or would one plus 3 house been a better scheme.
My 2 starters are both the same brand at 900cca they are sealed units 2 years old.
2 deep cycle house batteries 140ah both same brand and both less than a month old.
My altenator is new at 70 amp. I 4 cylinder motor For Devon 98hp read Leman kin US talk.
both house and starter isolation swithces both on or selected.
No 3 stage inverter only a 200w unit run off batteries for vacuum, tools etc.

 

[KnotYet]

One decent battery should suffice to reliably start a small diesel like yours.
Make sure it is being fully recharged between starts.

Your alternator, though small, should keep it charged.
If the alternator is the only source to charge all four batteries then maybe not.
It would be better to have a different alternator charging the house bank or
at least an isolation system.

I am a fan of marine alternators and external regulators.

 

[C lectric]

In addition to checking the electrolyte with a hydrometer for basic condition disconnect those batteries NEGATIVES and one by one, using a DMM in amp mode and using some jumpers reconnect each battery NEGATIVE through the DMM to the bussbar they were previously connected to..

Take a reading. You may have some ghost or parasitic loads drawing the batteries down. You will need a DMM that can handle up to about 10A DC.

If there is no current reading then at that moment there are no ghost loads.

You could then do the same to each battery with the DMM connected to both NEGATIVE leads of the two batteries. If there is ANY current then one of the batts. may be failing and the other is feeding it which then discharges the good one. One has become a load to the other.

Just be very carefull to ensure you connect the DMM to each of the NEGATIVES of each battery.

When not dealing with a battery make sure the NEGATIVE is secured out of the way.

 

[BruceK]

with post 7 above.
Try to discover what is causing your start batts to lose charge over 1 week of disuse. Could they be transferring charge into the ?undercharged existing 2 house batts?
If you have 2 batts connected, and one is undercharged, (or just plain defective) the "good" one will be drained by the "bad" one.
Are you on a marina with electricity which can power a charger? If not, do you have solar, or can you install it? Batts left chronically undercharged will sulfate, ie the sulfur in the acid will attach to the plates. Equalization by a charger function may put it back into solution but it`s best avoided by good charging maintenance.

 

[SteveK]

Phil,
One alternator charging four batteries. As said, possible, but chances are that your selector switch also sends charge to one of two banks, either starter or house.
Still until you check with Hydrometer and also as said before look for a parasitic drain on the start batteries we will not know.
Since you do not have a charger, once the engine stops the batteries no longer get a charge. So it is possible the start batteries are connected to house which have a draw on them.

You did say the house batteries are a new addition along with a small inverter. Perhaps the start battery issue started after that install.

 

[BruceK]

Start batts are sealed, hydrometer test not possible.

 

[SteveK]

Start batts are sealed, hydrometer test not possible.

Right. That leaves voltage check and as said disconnect GND wires and check for drain caused by ?

 

[Phil23]

All goods stuff guys thanks very much, was looking at a repower to 6 cylinder a couple of years ago but at 8.5 tons of displacement hull the current motor on a 3/1 prm box and a 25 x 25 3 bladed prop gives me hull speed at 1900rpm and intermittent 9 to 9.5knots at 21/22rpm and motor not overlaoded to many more geegees and I would just dig a hole.
I think I will now add a third house battery to the mix.

 

[OldDan1943]

Phil, if you intend to add a 3rd battery and the other 2 are about a year old, you are safe with the addition. That is assuming you did not abuse the other 2 batteries. If the other 2 batteries are more than a year old or been cycled too many times, plan on replacing all the house batteries together.
Changing out the start battery at the same time has merit but, I wouldn't worry too much because that battery is isolated from day to day use with the house load.

 

[backinblue]

Phil, I had the same issue. 2 house batteries that were marginal for an overnight at anchor. I planned to add a third, installed by a local yard that I trust. After looking at it, they suggested I could up-size my 2 house batteries and have approximately the same capacity of adding another (3rd) of the smaller size. They fit in the same location (just new boxes) and saved a lot of time and money not having to add another mounting location, cabling, etc. I was left with 2 almost new batteries that I resold at about 50%, but in the end saved money for the same result.

 

[ronobrien]

I am running 2 house batteries, adequate but can always use more plus 2 starter batteries each 90cca 100ah. I don't think my starters get enough pull and constantly seem to be only holding 12.3 12.4 volts after a stand down period of approx. a week.
Wondering, as I have just installed 2 new house batteries it would be worth considering adding a third while all will be the same age and run one starter. My motor starts after no more than 2 to 3 revolutions even having sat for a couple of weeks.


Any thoughts??

If I understand correctly the batts are down to 12.3 while sitting for a week. This seems low for batts after only a week sitting idle. I have 2 8d's and they hold a full charge for months sitting on the hard. I think you need to look for a parasitic draw existing with everything "off". Or the batts are simply not holding a charge due to age/damage. Verify the batts and the system before making changes. You may wind up chasing a ghost otherwise.

 

[Davil1]

I am running 2 house batteries, adequate but can always use more plus 2 starter batteries each 90cca 100ah. I don't think my starters get enough pull and constantly seem to be only holding 12.3 12.4 volts after a stand down period of approx. a week.
Wondering, as I have just installed 2 new house batteries it would be worth considering adding a third while all will be the same age and run one starter. My motor starts after no more than 2 to 3 revolutions even having sat for a couple of weeks.


Any thoughts??

===========================
there are many opinions on having a big one bank vs having two banks with a dedicated staring bank, and the opinions are as strong as any boating issue.
In my setup have 6 batteries size 31.
4 are dedicated to house.
two are separated, isolated and charging independently, on a single bank with a
1-2 combine - off switch
Battery 1 to starter
Battery 2 to windlass
combine both.
Rational (or lack off)
I cannot retrieve my anchor without windlass
Cannot start engine without battery
My engine alarm goes off when the engine starts, the key on the panel is always on, the alarm reminds me to go down and turn the batteries switch off!!
Use a "smart" charger that allows charging two banks separated when connected to 110
also a smart charger from the alternator, set up to charge starter bank first and then switch to house.
Also use 2 solar panels dedicated to starter/windlass bank.
Obsessive compulsive
you bet

 

[castellah22]

looks a very nice boat

 

[BruceK]

===========================
there are many opinions on having a big one bank vs having two banks with a dedicated staring bank, and the opinions are as strong as any boating issue.
In my setup have 6 batteries size 31.
4 are dedicated to house.
two are separated, isolated and charging independently, on a single bank with a
1-2 combine - off switch
Battery 1 to starter
Battery 2 to windlass
combine both.
Rational (or lack off)
I cannot retrieve my anchor without windlass
Cannot start engine without battery
My engine alarm goes off when the engine starts, the key on the panel is always on, the alarm reminds me to go down and turn the batteries switch off!!
Use a "smart" charger that allows charging two banks separated when connected to 110
also a smart charger from the alternator, set up to charge starter bank first and then switch to house.
Also use 2 solar panels dedicated to starter/windlass bank.
Obsessive compulsive
you bet

On my last boat I had a solar panel dedicated to the dedicated start batt for the genset.

 

[Davil1]

On my last boat I had a solar panel dedicated to the dedicated start batt for the genset.

======================
yes
realize it all depends on what type of boating a person does.
If the boat is worked on protected waters, inland,easy to reach by towing services is a total different experience.
I sometimes cruise offshore, most times away from home and sailboats tend to
overkill on redundant systems, nevertheless any boat should benefit from having a battery dedicated to the starter motor, totally independent , in my humble opinion.
cheers

 

[Phil23]

Ok I am feeling a right "dick" after pulling out my two starter batteries which I stated were only 2 years old, wrong, they are 5 years old, an incorrect entry in my maintenance log!!! blaming the ships dog.
I have decided to add a third deep cycle house battery giving me 360ah. My alternator which is new is 70amps plus a have a 200watt solar panel installed through a regulator and running at all times to the house bank.
My query now is will I have adequate charging capabilities for 3 deep cycle and 1 start battery at say 90cca.

 

[Phil23]

I have made an error in my original post due to an incorrect maintenance log entry, my starting batteries are in fact five year old and not 2 as originally stated hence the reason they are struggling to hold a full charge over a week or so.
I have made to decision to change my set up to 3 deep cycle house batteries at 120ah each and 1 starter at 900cca. My alternator which is new 12months ago producers 70 amps and I have a 200amp solar panel through regulator etc to the house bank or both when both the house and start switches are on. My query is do I have enough charge capabilities for this set up.

 

[SteveK]

Phil. Post #1 said your start batteries are 12.2 volts after sitting for a week which is considered 50% depleted, but that your engine starts after 2-3 turns.

Your two similar posts just now say you have 5 year old batteries but will add one to house and only keep one starter battery.
Both old start batteries will be replaced by one new start battery?
You may have a 200 watt solar panel maybe 20 amps, 200 amps suggest a lot of solar panels.
You have one 70 amp alternator, I may have missed how that charges house and start batteries which should be separated from each other so they all do not discharge.
Does solar charge only house and alt only the start batteries?

 

[backinblue]

The separate banks may be charged together from the alternator through an ACR.

 

[catalinajack]

The separate banks may be charged together from the alternator through an ACR.

Or a DC-DC charger if the battery technology is different requiring different charging profiles.

 

[Seevee]

I have made an error in my original post due to an incorrect maintenance log entry, my starting batteries are in fact five year old and not 2 as originally stated hence the reason they are struggling to hold a full charge over a week or so.
I have made to decision to change my set up to 3 deep cycle house batteries at 120ah each and 1 starter at 900cca. My alternator which is new 12months ago producers 70 amps and I have a 200amp solar panel through regulator etc to the house bank or both when both the house and start switches are on. My query is do I have enough charge capabilities for this set up.

Assume your house batteries are 12v, then 120a each would give you 360 total ah, of which 50% or 180ah would be usable, and the 70a alternator would do the job, but a bit anemic.



Personally, I like the idea of one start battery for both engines to allow for a bigger house battery. You could use the house as a back up to the start, and the gen battery as a back up to the start. I'm thinking of going that way.



And, as mentioned, you can charge both start and house with an ACR or DC to DC charger.