dual purpose engine start/domestic batteries

The minimum Cold Cranking AMP (CCA) you require for the 6V92's is 950 ... and my guess is that that a single 110 AH 12V battery would give you around 1000 CCA... So for a 24V system, you will as a minimum need 2 x 110 AH batteries.

However as this is about borderline, I'd upsize... As a sample, on our 6/71's which require less CCA than yours (the 6/92's are higher volume than the 6/71's), I have 2x 190 AH batteries i series (24V), which give me approx 1150 CCA. These are now getting on three years old and they are not more than I need. Next time, I will go with batteries with higher CCA.
 
Thanks Alf (sent you a mail by the way about other stuff)

Sorry for being thick, but my boat is 12v, or are you saying the DDs require 24v?
Is the CCA cumulative - I.e 3 500 CCA batteries = 1500 CCA or does it not work like that?

The current set up does supply just enough juice to start the engines but it's marginal. I suspect the whole lot needs changing, though I'm minded to buy in the uk as batteries seem to be 2.5 times the price out here.

I need to figure out which of my 12 batteries actually does the engine starting because changing 6 is much better than chAngibg 12
 
Portofino said:
MapishM will flame me for carp IT :)
Click to expand...
He might rather flame you for distorting his username as well... :D

Jez, some engines have the option of both 12V and 24v starter motor, and I would think that your DDs are 12V, because the page you previously posted specifies that the engine battery bank is connected in groups to supply 24V in case of MTU power.
In case of doubts about any other parts of the manual, just email me the relevant pages and I'll translate them.
 
Re price: see if you can find a local autofactors in San Carles or nearby, you should be able to get batteries at pretty much the same price as UK. Don´t bother with any of the chandleries - they are all robbers, and they just go down to the autofactors anyway.
It sounds like you have a 12v boat with the batteries connected in parallel (looks like that from your pics but cant be certain). If you find batteries connected in series that would be a 24v arrangement. Given that your batteries seem to be in groups of 3, I think you have a 12v boat. Easiest way to find out which does what is to identify the groups of three, and then disconnect the positive lead that goes into the bowels of the boat and see what doesn´t work etc. to be sure measure the voltage on the large starter motor connections.
 
Thanks P.

Google translate does an acceptable job about 70% of the time.
I'm actually considering bringing the manual home and have a uk version made.
This involves scanning each page and replacing the text.

Not cheap though....

Anyway, back to batteries. Things I have learnt this week:

I don't know enough about batteries
There is something called CCA and I need a fair bit of it.
Batteries in Spain are very expensive

Is there a way I can (using a meter) see when a battery is under load? That way I can crank each engine and see which batteries are feeding the starter.
 
Whitelighter said:
Is there a way I can (using a meter) see when a battery is under load?
That way I can crank each engine and see which batteries are feeding the starter.
Click to expand...
When under heavy load (as is the case while cranking), the voltage drops immediately, and enough to be clearly measurable.
But... Ermm... Can't you simply detach one cable from each battery bank (one at a time, obviously), and see what works and what doesn't? :rolleyes:
 
MapisM said:
When under heavy load (as is the case while cranking), the voltage drops immediately, and enough to be clearly measurable.
But... Ermm... Can't you simply detach one cable from each battery bank (one at a time, obviously), and see what works and what doesn't? :rolleyes:
Click to expand...

That's just me over complicating this as usual.

You and nick make the same sensible point
 
If you have a 12V starter motor, then you need 12V batteries ... It's just that most DD installs I've seen has been 24V ones...

I believe that if batteries are coupled parallel, it will work something like that ... but probably something about energy loss etc., which someone much smarter than I am can answer...

Sent separate note re; e-mail changes...
 
Jez - I've sent you a PM. Some really good stuff coming out of this thread but some red herrings too (all with the very best of intentions by the particiapnts), I've tried to simplify it to explain the logic and rational. This is quite a simple problem with a simple solution. I've also included some options on how to prevent this happening again and how to keep all the battery banks balanced and charged properly.
 
Jez

My experience is that you can see very quickly if a battery is in good condition or not - using the tester that I have back in SC.
It is a simple volt meter with a big load in parallel.

You disconnect each battery and apply the tester to each one at a time.
You don't connect the tester to the whole bank.
With the tester connected, for about 9 or 10 seconds, the voltage will drop (even on a good battery).
You can then read the voltage after 9 or 10 secs - the meter indicates the state of the battery.

This meter works for batteries form 80ah to 140ah but in reality, you will see very quickly if your battery needs replacement.
Another check when using this method (for batteries that can be topped up) is to unscrew each of the cells before carrying out the test - then look inside each one as the test is being carried out.
If one cell bubbles furiously, then the battery is duff.

More importantly to any of this stuff, you should make sure that the battery compartment is properly ventilated.
Are your batteries in boxes that can have vent hoses fitted?
 
They are not in what I would call boxes in that they aren't air tight.
I'll come and find you when your back and borrow your tester - G+S planning a flotilla run down to vineros for lunch in Thursday if you're back
 
Hurricane said:
Jez

My experience is that you can see very quickly if a battery is in good condition or not - using the tester that I have back in SC.
It is a simple volt meter with a big load in parallel.

You disconnect each battery and apply the tester to each one at a time.
You don't connect the tester to the whole bank.
With the tester connected, for about 9 or 10 seconds, the voltage will drop (even on a good battery).
You can then read the voltage after 9 or 10 secs - the meter indicates the state of the battery.

This meter works for batteries form 80ah to 140ah but in reality, you will see very quickly if your battery needs replacement.
Another check when using this method (for batteries that can be topped up) is to unscrew each of the cells before carrying out the test - then look inside each one as the test is being carried out.
If one cell bubbles furiously, then the battery is duff.

More importantly to any of this stuff, you should make sure that the battery compartment is properly ventilated.
Are your batteries in boxes that can have vent hoses fitted?
Click to expand...
Hi Hurricane - just a point of reference - the reason why those drop testers aren't very popular any more is that they can often arc when applying the load and have been known to cause explosions (with the venting hydrogen gasses). Hence the new electronic versions don't adopt the same approach. They need to be used with extreme caution. With proper venting they *should* be OK but as you cannot see Hydrogen you need to be very sure the area is vented well.
 
Jez, it might be worth speaking to Battery Megastore to see if they have a Spanish operation (they have a French subsidiary, for example). If not - then you could buy the replacement batteries in the UK, and just take them with you when you're driving down with your new outboard motor... :D:D
 
Just replaced a batt in daughters car -after she called AA out .
AA chap tested it and told me 12.6 V-it's ready for replacement - it was12.64 V
So I guess if you turn em off( leave the AC power on ) but charger offhand any draw like lights off.
Go out for 2-3 hours -beach /pool etc
Then using a simple multimeter test and record each of the 12 batts
Any arround or under 12.6 --- target 1st for replacement .Any over 13 great .
Depending on how they're connected , probably best to seperate em first and let stand for a coupled hours, then measure?
Alf -they in deep boxes -so that dictates the size - more/ less same or smaller dimensions
 
Whitelighter said:
They are not in what I would call boxes in that they aren't air tight.
I'll come and find you when your back and borrow your tester - G+S planning a flotilla run down to vineros for lunch in Thursday if you're back
Click to expand...

Do you mean this Thursday?
We aren't planning on being back until Wed week.
But we will have visitors on board when we do get back.
 
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