Battery advice?

[Quandary]

I am in the process of adding a battery to our Moody S31 in the hope that we can run the fridge a bit longer in the sweltering heat we now have to put up with up here. The present arrangement is a pair of 100ah, one domestic and the other for starting the engine and running the windlass. My plan is to make the two existing large batteries domestic by wiring them in parallel
and add a smaller engine/windlass battery alongside, there is plenty of depth but the size is limited by available height as the locker floor moulding rises with the hull shape. I have a surplus Numax MV12, described as a 'starting and leisure marine' battery which is showing 12.75v about a month after it was last charged which I am tempted to use. Problem is that the terminals are the wrong hand and the existing battery cables are neatly routed through the moulded ducts under the aft cabin but difficult to replace.
I presume it would be ill advised to attempt to extend an existing positive battery cable?
If it is better to start with a new battery is there a size demanded by this use, ie is 50-70ah enough?
Another question? most batteries now seem to have small bolt on terminal pins paired with the conventional pillars, is there any reason not to use these to increase terminal clearance?
I am a cheapskate as well as an electrical numpty so content to continue with conventional lead acid type batteries though I know that more sophisticated compact batteries are available which might be easier to accommodate, but I have plenty of space low down, close to the centre line, and weight is not an issue. I am still at the stage of making the plug for the box for the third battery so any comments or advice welcomed. I may eventually add a solar panel, but one step at a time.

 

[Spyro]

Sounds like a fine idea to me. Running your windlass off the starter battery doesn't sound like a great idea I would have the engine on when running the windlass anyway so juice is coming from the alternator and not the battery.
50-70 ah is the capacity and not really anything to do with starting power. A small starter battery would be the way to go and still be able to start off the domestic bank if that fails. If it was me I'd be off down the scrappys for a small starter batter that has terminals in the right place.

 

[moomba]

I am in the process of adding a battery to our Moody S31 in the hope that we can run the fridge a bit longer in the sweltering heat we now have to put up with up here. The present arrangement is a pair of 100ah, one domestic and the other for starting the engine and running the windlass. My plan is to make the two existing large batteries domestic by wiring them in parallel
and add a smaller engine/windlass battery alongside, there is plenty of depth but the size is limited by available height as the locker floor moulding rises with the hull shape. I have a surplus Numax MV12, described as a 'starting and leisure marine' battery which is showing 12.75v about a month after it was last charged which I am tempted to use. Problem is that the terminals are the wrong hand and the existing battery cables are neatly routed through the moulded ducts under the aft cabin but difficult to replace.
I presume it would be ill advised to attempt to extend an existing positive battery cable?
If it is better to start with a new battery is there a size demanded by this use, ie is 50-70ah enough?
Another question? most batteries now seem to have small bolt on terminal pins paired with the conventional pillars, is there any reason not to use these to increase terminal clearance?
I am a cheapskate as well as an electrical numpty so content to continue with conventional lead acid type batteries though I know that more sophisticated compact batteries are available which might be easier to accommodate, but I have plenty of space low down, close to the centre line, and weight is not an issue. I am still at the stage of making the plug for the box for the third battery so any comments or advice welcomed. I may eventually add a solar panel, but one step at a time.

for your 2 leisure batteries you must make sure they are of the same Amperage is the best advise, to balance to flow and charge (which I think you are doing)
To extend you battery cable can be done buy using either a link fuse or a junction box or distribution post that is able to take the amps , you must make sure that the cables are the same and check that the battery cable that is now taking double the amps is capable of doing so. I have given you a ink to a great shop that I have used many times with great service, (no affiliation)
https://www.12voltplanet.co.uk/power-distribution.html
For your starter and windlass , is this wise as you may find if you need to use the windlass more than once when anchoring it might drain your starter battery .
Cn you put you windlass onto the leisure set up .

 

[Gwylan]

Regarding leads, should be as big a diameter as possible and as short as possible.
Within reason get the biggest battery you can fit. Though there are some very imaginative sales people out there when the rating of batteries are concerned.
If you are going to parallel batteries then get two new ones the same rating. Or you can expect some difficulties. Others will explain why. Trust me, I learned.

Assume you have a common neutral. The black wire - smiley face.

We have three sets of batteries. Keeps things some.

2 x 100 Ah in parallel for domestic use. A dedicated marine (expensive) charger.

1 x 100_Ah for the fridge, the car radio thingie and the Eber.

1 x whatever it is battery for engine starting.
Also have some jump leads in case I ever need it. Did need it once thanks to Humpty crew, another story.

The fridge and starter have their own dedicated Lidl chargers. Fraction of the price of a marine charger for them

Have 120 watts of solar panels. These can be used to charge either the fridge battery or the domestic bank. A switch concealed from fiddling fingers enables this.

All sorts of isolation opportunities so we can leave the fridge, navtex, radio and barometer on and everything else off. The barometer is an electronic recoding one, so it needs to be permanently live to function.
Means that we can be ready to go whenever we want to.
Most important the engine battery is isolated.

We also have an Adverc system and a spliter diode that charges all this off the alternator.

The result is that even in the golden north it was possible to keep beer cold and run the instruments whilst sailing away from CEE17 blue socket.

Suggest you use a bus bar to connect multiple feeds to or from the battery positives

 

[pvb]

...and check that the battery cable that is now taking double the amps is capable of doing so.

The OP hasn't said that he's going to be running additional equipment, so why would the current in the cable double?

 

[moomba]

The OP hasn't said that he's going to be running additional equipment, so why would the current in the cable double?

because he is doubling his leisure battery amps and he will need the cable to handle the extra amps and a good fuse to deal with the extra power if their is a fault . This is always advisory information and as boats have no electrical coding we DIY yourself, therefore caution is the best foot forward
This also allows redundancy in the system as the OP might want to add to his electrical current draw as he is adding double his amperage.
The OP also states he wants to run his fridge a lot longer in a warm climate , this will create more draw and therfore increasing wire size if needed (as I did say check first)

 

[pvb]

because he is doubling his leisure battery amps and he will need the cable to handle the extra amps and a good fuse to deal with the extra power if their is a fault . This is always advisory information and as boats have no electrical coding we DIY yourself, therefore caution is the best foot forward
This also allows redundancy in the system as the OP might want to add to his electrical current draw as he is adding double his amperage.
The OP also states he wants to run his fridge a lot longer in a warm climate , this will create more draw and therfore increasing wire size if needed (as I did say check first)

You don't really understand this stuff, do you?

 

[moomba]

You don't really understand this stuff, do you?

If you are so intelligent please inform me were I am going wrong , or I truly think your not reading my posts correctly
If the OP adds too his current set up and doubles the battery amperarage this potentially COULD run through his existing cables if a fault occured , causing a nasty wire fire, and running to his distribution , then I SAID CHECK TO SEE THAT YOU CABLE IS SUFFICIENT to handle extra loads.
At no point did I say it was not!! and no did I recommend he did change!! I said check , as this is sensible, if you are not sensible or wanting to add sensible ideas then please stop moaning :encouragement:

 

[pvb]

If you are so intelligent please inform me were I am going wrong , or I truly think your not reading my posts correctly
If the OP adds too his current set up and doubles the battery amperarage this potentially COULD run through his existing cables if a fault occured , causing a nasty wire fire, and running to his distribution , then I SAID CHECK TO SEE THAT YOU CABLE IS SUFFICIENT to handle extra loads.
At no point did I say it was not!! and no did I recommend he did change!! I said check , as this is sensible, if you are not sensible or wanting to add sensible ideas then please stop moaning :encouragement:

I explained in post 5, querying your statement "check that the battery cable that is now taking double the amps is capable of doing so".

The OP may well have gathered by now that he can disregard your remark.

 

[moomba]

I explained in post 5, querying your statement "check that the battery cable that is now taking double the amps is capable of doing so".

The OP may well have gathered by now that he can disregard your remark.

to OP I suggest if doubling the battery bank you check that you battery cables can take the amerpage and and the same size and length this will give you optimal battery life and safety
I am afraid PVB likes to follow me around and says silly things in his post, we have had run in before regarding batteries were he was shown up must be his revenge and a sad loser if he had better advice then we are still awaiting to hear it , he keeps going back to my post were I said I check your cable size this is sensible and a good electrician will tell you the same , basic common sense.

 

[RupertW]

to OP I suggest if doubling the battery bank you check that you battery cables can take the amerpage and and the same size and length this will give you optimal battery life and safety
I am afraid PVB likes to follow me around and says silly things in his post, we have had run in before regarding batteries were he was shown up must be his revenge and a sad loser if he had better advice then we are still awaiting to hear it , he keeps going back to my post were I said I check your cable size this is sensible and a good electrician will tell you the same , basic common sense.

Explain to us why you think doubling the Ah will double the maximum current through the cables and we might understand what you are trying to explain. It sounds to me like you are saying that if you double the size of the water tank then you must double the size of your taps as the water flow will be doubled. Amps and Amp Hours are different dimensions.

 

[moomba]

to OP I suggest if doubling the battery bank you check that you battery cables can take the amerpage and and the same size and length this will give you optimal battery life and safety
I am afraid PVB likes to follow me around and says silly things in his post, we have had run in before regarding batteries were he was shown up must be his revenge and a sad loser if he had better advice then we are still awaiting to hear it , he keeps going back to my post were I said I check your cable size this is sensible and a good electrician will tell you the same , basic common sense.

To OP if you are demanding more load on your batteries I.e fridge longer adding some more , using a larger inverter please
Calculate the maximum load you will ever put on your battery bank and size the cables to that load. Before finally selecting and settling on a cable size though it’s worth reading Understanding Cable and Cable Sizes as there might be a bit more involved.

 

[pvb]

to OP I suggest if doubling the battery bank you check that you battery cables can take the amerpage and and the same size and length this will give you optimal battery life and safety
I am afraid PVB likes to follow me around and says silly things in his post, we have had run in before regarding batteries were he was shown up must be his revenge and a sad loser if he had better advice then we are still awaiting to hear it , he keeps going back to my post were I said I check your cable size this is sensible and a good electrician will tell you the same , basic common sense.

You said the cable was taking double the current. It isn't.

You have a history of posting less than accurate advice on this forum, and I've taken issue with some of it because it's important that forum users are given accurate info. If you want to descend to personal insults, fine, I'll just ignore them as I ignore much of what you post.

 

[moomba]

Explain to us why you think doubling the Ah will double the maximum current through the cables and we might understand what you are trying to explain. It sounds to me like you are saying that if you double the size of the water tank then you must double the size of your taps as the water flow will be doubled. Amps and Amp Hours are different dimensions.

Never said that at all I said that potentially if their is a short the load through the cable will be the maximum the batteries will let out which is 200 amps if he does not have a fuse or wire rated at 150 amps there is a problem
hope that makes sense.:encouragement:

 

[Tranona]

to OP I suggest if doubling the battery bank you check that you battery cables can take the amerpage and and the same size and length this will give you optimal battery life and safety
I am afraid PVB likes to follow me around and says silly things in his post, we have had run in before regarding batteries were he was shown up must be his revenge and a sad loser if he had better advice then we are still awaiting to hear it , he keeps going back to my post were I said I check your cable size this is sensible and a good electrician will tell you the same , basic common sense.

Stop digging your hole and think through exactly what pvb is saying. Your "logic" is just plain wrong.

If the OP is not adding any electrical equipment and therefore loads why does he need to double the cable size - or even change it at all. The size of his battery bank is irrelevant. All it means is he can run his current equipment for a longer period.

 

[pvb]

To OP if you are demanding more load on your batteries I.e fridge longer adding some more , using a larger inverter please

Inverter? Where did the OP say he was using an inverter?

 

[moomba]

You said the cable was taking double the current. It isn't.

You have a history of posting less than accurate advice on this forum, and I've taken issue with some of it because it's important that forum users are given accurate info. If you want to descend to personal insults, fine, I'll just ignore them as I ignore much of what you post.

No I never said it I said it might happen in a short I never said he will need double amperage , I also said he will be demanding more on his fridge . you have been proven wrong many times PVB at least I am man enough to admit it

 

[pvb]

Never said that at all I said that potentially if their is a short the load through the cable will be the maximum the batteries will let out which is 200 amps if he does not have a fuse or wire rated at 150 amps there is a problem
hope that makes sense.:encouragement:

No, it makes no sense, like much of what you've posted here. If there's a short, the batteries will probably be capable of delivering a current of 800-1000A.

 

[moomba]

No, it makes no sense, like much of what you've posted here. If there's a short, the batteries will probably be capable of delivering a current of 800-1000A.

therefore his cable needs to be protected by either having better cable or a fuse and not all short will demand the max you are using an extreme example , were as I am protecting against simple surges and faults use google if you know how

 

[pvb]

No I never said it I said it might happen in a short I never said he will need double amperage , I also said he will be demanding more on his fridge . you have been proven wrong many times PVB at least I am man enough to admit it

Are you sure you didn't?

... check that the battery cable that is now taking double the amps is capable of doing so.