Battery advice?

[ghostlymoron]

The starter battery has a very easy life. Although it has to provide 200 amps to start the engine, it's only for about 10 - 15 seconds so the draw is 200*15/60*60 amp hrs or > 1. Upon starting, the engine alternator provides say 10 amps charge so after 6 minutes the battery is fully charged again. If you have a larger alternator, it may do it in less.

 

[jwilson]

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:

Please stop: if an ordinary quite small car starting battery shorts out the draw can easily be 600-800 amps through the red-glowing spanner across the melting lead terminals - doesn't mean all the cable in that car has to handle 800 amps..... All the OP wants to do is take the same (probably 5 amp) load for longer.

 

[Quandary]

The main thing I have got out of this thread is how low my understanding of 12v. electrics is.
I am now having second thoughts about the whole idea. I was attracted to the project by having time and a battery to spare, unused locker space to fit it and what I thought was a simple job moving some cables. We have probably one to three seasons left in us if we are lucky, and it ain't broke perhaps best not to fix it? The existing system seems to be safer as it is so I will defer deciding whether to proceed with the job until my head clears a bit.
I do appreciate the efforts made to guide me, thanks.

 

[pvb]

The main thing I have got out of this thread is how low my understanding of 12v. electrics is.
I am now having second thoughts about the whole idea. I was attracted to the project by having time and a battery to spare, unused locker space to fit it and what I thought was a simple job moving some cables. We have probably one to three seasons left in us if we are lucky, and it ain't broke perhaps best not to fix it? The existing system seems to be safer as it is so I will defer deciding whether to proceed with the job until my head clears a bit.
I do appreciate the efforts made to guide me, thanks.

I can see you're in a quandary about this (geddit?), but it really is a very simple DIY job, and it'll double the capacity of your house bank, enabling you to run the fridge for longer if you need to.

If you don't want to DIY, any sensible marine electrician could hook it up for you very quickly.

 

[Tranona]

Second, how on earth did Tranona get banned? That has to be crazy.

Back now and as you would expect I asked myself the same question. Those who followed the thread might deduce what caused the concern.

There have been exchanges with the Administrators so I can't go into details. However I will continue to make honest observations in my usual polite way.

It's amazing how a simple thing such as the OP proposed could lead to so much misunderstanding, despite right from the start sensible advice on how to achieve his aims was offered by a number of respondents. But guess not for the first time here things can get out of hand.

Life goes on.

 

[awol]

The main thing I have got out of this thread is how low my understanding of 12v. electrics is.

... and if you absorb bits of utter tosh that has been spouted on this thread, you will not have improved it. Your plan is good, your wiring is fine. Connect your 2 house batteries together + to +; -ve to -ve, put your new battery in place of the swapped engine start yin and you are done. I did as Spyro advised, popped down to the local scrappy and got a s/h Renault van battery when I doubled up my house batteries. I just kept my 1-2-both switch to control the set-up.

 

[Quandary]

I can see you're in a quandary about this (geddit?), but it really is a very simple DIY job, and it'll double the capacity of your house bank, enabling you to run the fridge for longer if you need to.

If you don't want to DIY, any sensible marine electrician could hook it up for you very quickly.

Thanks, I will digest everything before deciding. I do know a good marine electrician but he is not close and I had expected to be able manage something that had appeared straightforward.
I am usually in a Quandary and was definitely in one when I chose my user name. Believe it or not I did once have a boat called Quandary, the name came from the indecision about what name we should give her.

 

[scottie]

You seem to have sparked off quite a bit of heat with this post which I know was not your intention but your in cheek ref to warmer summers was misinterpreted by some .
We have a 3 battery set up with domestic,engine and winches (anchor and main hoist)
I have always felt uncertain at the winch battery being linked to the engine in that we can only use it whilst the engine is charging? However when we did have a problem which took quite some time to solve we discovered that even with the battery switches off the winch battery could drain the engine battery.
The point I would make is keep it simple and have a proper wiring diagram for the next owner or even your own reference.

 

[moomba]

Please stop: if an ordinary quite small car starting battery shorts out the draw can easily be 600-800 amps through the red-glowing spanner across the melting lead terminals - doesn't mean all the cable in that car has to handle 800 amps..... All the OP wants to do is take the same (probably 5 amp) load for longer.

nope depends on the short agreed the batteries can go higher my apologizes on that but really stop over reacting to my post a small short can only demand a smaller amount as well

 

[pvb]

nope depends on the short agreed the batteries can go higher my apologizes on that but really stop over reacting to my post a small short can only demand a smaller amount as well

Some people might consider that "a small short" is rather like being "a little bit pregnant".

 

[PaulRainbow]

nope depends on the short agreed the batteries can go higher my apologizes on that but really stop over reacting to my post a small short can only demand a smaller amount as well

Oh dear, you don't understand, do you.

What's a small short ?

Seriously, you need to learn a lot more about electricity before you post. I'm not sure where to suggest, but you really do need to go back to basics, starting with the differences between amps, volts, amp hours etc. This is where you got into trouble in this thread, you don't understand what amps and amp hours are, or even how current works.

I'll try a couple of basics, for the pedants, the following is basic, i'm not confusing things be being overly technical. Amps is a measure of current, think of it as how fast you can get power out of the battery. So a 600 amp battery can deliver 600 amps, maximum. It can obviously deliver less. It's probably about 100 amp hours. This means it can deliver 1 amp for 100 hours. This is a bit innacurate in the real World, as the capacity varies with age, temperature etc and you should not go below 50% discharge with a normal lead acid battery. But don't get hung up on that here.

If you connect two batteries in parallel (pos to pos, neg to neg) the voltage stays the same, but the amps will become the sum of both batteries amperage. Two 12v 600a batteries will become one 12v 1200a battery. The amp hours obviously do the same.

But, just because you now have twice the available amps, nothing else changes, except you can run the same things for twice as long (or more things). Amps are not pushed up the cables by the battery, they are sucked up it by the appliance, so no need to increase cable sizes. If you ran the fridge for longer, still no need to increase cable sizes, if the cables are correctly rated they will run the fridge for 5 minutes in the hour, or run it 24/7, the current draw (amps) is the same, so again, no need for bigger cables.

Where you to add more equipment that resulated in a greater current draw, you would need to consider cable sizes, but that would be the case whether you had one battery or 6. So, as you can now see (hopefully) the act of adding more batteries does not require the cables to be uprated.

As for fusing, in an installation such as this (typical boat arrangement) it's best to forget about available battery amps or even loads, all you are protecting is the battery cables, so just fit fuses that are rated for the cable. For 35mm cable, fit 240a fuses.

 

[awol]

I'll try a couple of basics, for the pedants, the following is basic, i'm not confusing things be being overly technical. Amps is a measure of current, think of it as how fast you can get power out of the battery. So a 600 amp battery can deliver 600 amps, maximum. It can obviously deliver less. It's probably about 100 amp hours. This means it can deliver 1 amp for 100 hours. This is a bit innacurate in the real World, as the capacity varies with age, temperature etc and you should not go below 50% discharge with a normal lead acid battery. But don't get hung up on that here.

Please Paul, you're making my head hurt almost as much as Moomba. There is no such thing as a 600amp battery. It may be rated as 600 CCA - Cold Cranking Amps are the numbers of amperes a lead-acid battery at 32 degrees F (0 degrees C) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery). Amp.hours are the measure of charge, easier to handle than the Coulomb, a basic SI unit - 1Ah = 3.6kC

 

[ctva]

Thanks, I will digest everything before deciding. I do know a good marine electrician but he is not close and I had expected to be able manage something that had appeared straightforward.
I am usually in a Quandary and was definitely in one when I chose my user name. Believe it or not I did once have a boat called Quandary, the name came from the indecision about what name we should give her.

We’re down on the boat just now and we have the kind of setup that you are after to have a look at We’re here all weekend.

 

[moomba]

Oh dear, you don't understand, do you.

What's a small short ?

Seriously, you need to learn a lot more about electricity before you post. I'm not sure where to suggest, but you really do need to go back to basics, starting with the differences between amps, volts, amp hours etc. This is where you got into trouble in this thread, you don't understand what amps and amp hours are, or even how current works.

I'll try a couple of basics, for the pedants, the following is basic, i'm not confusing things be being overly technical. Amps is a measure of current, think of it as how fast you can get power out of the battery. So a 600 amp battery can deliver 600 amps, maximum. It can obviously deliver less. It's probably about 100 amp hours. This means it can deliver 1 amp for 100 hours. This is a bit innacurate in the real World, as the capacity varies with age, temperature etc and you should not go below 50% discharge with a normal lead acid battery. But don't get hung up on that here.

If you connect two batteries in parallel (pos to pos, neg to neg) the voltage stays the same, but the amps will become the sum of both batteries amperage. Two 12v 600a batteries will become one 12v 1200a battery. The amp hours obviously do the same.

But, just because you now have twice the available amps, nothing else changes, except you can run the same things for twice as long (or more things). Amps are not pushed up the cables by the battery, they are sucked up it by the appliance, so no need to increase cable sizes. If you ran the fridge for longer, still no need to increase cable sizes, if the cables are correctly rated they will run the fridge for 5 minutes in the hour, or run it 24/7, the current draw (amps) is the same, so again, no need for bigger cables.

Where you to add more equipment that resulated in a greater current draw, you would need to consider cable sizes, but that would be the case whether you had one battery or 6. So, as you can now see (hopefully) the act of adding more batteries does not require the cables to be uprated.

As for fusing, in an installation such as this (typical boat arrangement) it's best to forget about available battery amps or even loads, all you are protecting is the battery cables, so just fit fuses that are rated for the cable. For 35mm cable, fit 240a fuses.

 

[black mercury]

Please Paul, you're making my head hurt almost as much as Moomba. There is no such thing as a 600amp battery. It may be rated as 600 CCA - Cold Cranking Amps are the numbers of amperes a lead-acid battery at 32 degrees F (0 degrees C) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery). Amp.hours are the measure of charge, easier to handle than the Coulomb, a basic SI unit - 1Ah = 3.6kC

I think Paul knows this, he was just keeping things simple. I could understand that Paul meant a 600 cold cranking amp battery when he called it a 600amp battery. And his post makes sense to me.

 

[moomba]

Please Paul, you're making my head hurt almost as much as Moomba. There is no such thing as a 600amp battery. It may be rated as 600 CCA - Cold Cranking Amps are the numbers of amperes a lead-acid battery at 32 degrees F (0 degrees C) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery). Amp.hours are the measure of charge, easier to handle than the Coulomb, a basic SI unit - 1Ah = 3.6kC

Ok people I have to again repat that I am several disablaed in the cognitve function and certain words and phrases come out , left field, please clam down to some thing that are said its ok
my meanig t this is that the wire can demand more or less pwer due to the fault, i.e a light blowing or two wires connecting , will each have a diffrence of pwer asked for.
Now as the argument went on I was 3 hours of my meds and my anxiety kicked in therefore writng like a mad mad man but not knowing what I was writting
I also have taken certain comments out of context my apooligies if that offended anyone
but my intial claim which I was lamblasted for was if you add 2 batteries in parrelel then just check the wire can handle the extra thats all . simply really
I ahve added a lovely website that tells you this to just incase you think im having a funny turn
he other type of connection is parallel. Parallel connections will increase your current rating, but the voltage will stay the same. In the “Parallel” diagram, we're back to 6 volts, but the amps increase to 20 AH. It's important to note that because the amperage of the batteries increased, you may need a heavier-duty cable to keep the cables from burning out.
https://www.batterystuff.com/kb/articles/battery-articles/battery-bank-tutorial.html

Oh Paul I appreciate your knowledge on these forums s I alway like them
but my brother in a Naval Artichtuce and my brother for the lat 20 years is an ROV piolt and technician which runs all electrical , so I can and do knw somthing , just get confused ,

 

[ip485]

Yes, PaulRainbows post makes perfect sense to me, and sets out the position very clearly.

 

[awol]

I think Paul knows this, he was just keeping things simple. I could understand that Paul meant a 600 cold cranking amp battery when he called it a 600amp battery. And his post makes sense to me.

You may think it's keeping it simple - to me it is just wrong. I don't think it's pedantry to object to palpably incorrect information e.g. "So a 600 amp battery can deliver 600 amps, maximum." So we have Moomba pushing 100A down a wire because it's a 100Ah battery, and Paul conflating CCA and Ah.

My memory was wrong about the Coulomb - it is not a base SI unit, it is defined as C= As where the Amp is defined in terms of Force.

 

[dom]

I just kept my 1-2-both switch to control the set-up.

Your electrical insights and calcs are both spot on and a valuable addition to this bizarre thread.

But relying on logic to control the indignation following the suggestion of a 1-2-both set up; well I wish you luck

 

[moomba]

Your electrical insights and calcs are both spot on and a valuable addition to this bizarre thread.

But relying on logic to control the indignation following the suggestion of a 1-2-both set up; well I wish you luck

My apologies to the OP for causing confusing this was not my intention , My was first post may have been taken out context and I may have taken at face value what was asked for.
I was trying to say to check the cables on the battery's if you are connection in parallel. Parallel connections will increase your current rating, but the voltage will stay the same. It's important to note that because the amperage of the batteries increased,as you were adding another battery you may need a heavier-duty cable to keep the cables from burning out on the batteries.
I was then hit with multiple replies , that got me confused and I was answering under stress and anxiety.
So please I take those other comments out ,and would appreciate if all would not reference those comments as they are wrong. ty