Position for more batteries

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pcatterall

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I am considering installing 2 more leisure 100AH batteries. I cant find a place near the existing bank. Might be nice to locate them on the other side for balance purposes.
Can I link them without using huge stiff cable assuming that they are not used for starting.
Any advice welcome!!
 
pcatterall said:
I am considering installing 2 more leisure 100AH batteries. I cant find a place near the existing bank. Might be nice to locate them on the other side for balance purposes.
Can I link them without using huge stiff cable assuming that they are not used for starting.
Any advice welcome!!
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I have this arrangement on my boat, 4 domestic batteries under starboard bunk in aft cabin, 2 domestic batteries under port bunk. They are interlinked with hefty cable (35 sq mm?) to minimise voltage drop. Also, the negative and positive feeds are taken from opposite ends of the bank. The cable doesn't have to be stiff, but it is best to use heavy stuff.
 
You can stick them where you want as long as the cabling is rated and fused for the maximum load. Close to the alternator and distribution board is favourite.
 
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You could wire them up with lighter wire if you really must, but the wire would still have to cope with whatever loads you would be putting through, and that includes charging currents. You would also need to have, and remember to use, a switch to disconnect them if you needed to use the main bank for starting. It would all be a bit of of a botch and not very good practice. Best to use the right wire for the job.
 
pvb said:
Interesting theory perhaps, but hugely complicated and many additional connections at battery posts. At the end of the day, not practically worthwhile. Just taking the feeds from each end of the bank suffices.
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It's worth taking feeds from opposite ends of the 'bank' even with 2 batteries. The bit about the %age draws from a 4 battery bank was illuminating!
 
pvb said:
Interesting theory perhaps, but hugely complicated and many additional connections at battery posts. At the end of the day, not practically worthwhile. Just taking the feeds from each end of the bank suffices.
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Look again. There are the same number of links in No. 1 and No. 4. One link on each side just happens to be longer.

I think! :rolleyes:
 
Rigger Mortice said:
Look again. There are the same number of links in No. 1 and No. 4. One link on each side just happens to be longer.

I think! :rolleyes:
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But some of the connections have 3 cables on them, not ideal in many cases. And I can't even imagine how complex an arrangement he'd suggest for my 6 domestic batteries! In realistic practical terms, as I said, just taking feeds from opposite ends of the bank will be fine for most people.
 
Welding cable is very flexible and cheaper than tinned marine cable - I have used 70mm cross section for the run from my 120A alternator and my bank of 3 x 130AH domestic batteries. Possibly overkill, but what's the point in having a big domestic bank and then losing power in the cables?

Neil
 
Well I think that if your existing batteries do the job of starting the engine then it would not be necessary to use heavy wire to the new batteries. Not super light of course but not necessary to be rated like the main battery cables. yes you will take more current from the original batteries in starting if you use all batteries in parallel.
Charging and low current drain will still be OK. Charge will not be at very high currents initially if batteries are flat but any losses due to cable resistance will soon become insignificant.
As said you may need to fit fuses if you use light cable. Both ends if the batteries are paralleled. However if the wiring rund is simple wires well separated so that any chance of them shorting is nil and if they do get red hot there is no chance of fire ensueing then you may reasonably risk no fuses. good luck olewill
 
William_H said:
Well I think that if your existing batteries do the job of starting the engine then it would not be necessary to use heavy wire to the new batteries. Not super light of course but not necessary to be rated like the main battery cables. yes you will take more current from the original batteries in starting if you use all batteries in parallel.
Charging and low current drain will still be OK. Charge will not be at very high currents initially if batteries are flat but any losses due to cable resistance will soon become insignificant.
As said you may need to fit fuses if you use light cable. Both ends if the batteries are paralleled. However if the wiring rund is simple wires well separated so that any chance of them shorting is nil and if they do get red hot there is no chance of fire ensueing then you may reasonably risk no fuses. good luck olewill
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If the batteries are paralleled then surely they will all be sharing the load equally if the whole bank is used for starting? I don't understand why you say that you will take more current from the original batteries.

As for separating the wires, and if one then gets red hot there is no risk of fire..........Did you really mean that or was it meant tongue in cheek?
 
Rigger Mortice said:
If the batteries are paralleled then surely they will all be sharing the load equally if the whole bank is used for starting? I don't understand why you say that you will take more current from the original batteries.

As for separating the wires, and if one then gets red hot there is no risk of fire..........Did you really mean that or was it meant tongue in cheek?
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The starter large drain will be less on the new batteries because the thinner wires will cause a volt drop or restrict current from the new batteries. This will not matter much in terms of ballancing batteries if the new batteries are newer than the old ones anyway.

No not meant as tongue in cheek. Logically if the wires are well supported so that there is no chance of a short +ve to -ve then you should not get overheated cables. However you can also ensure that if overheat occurs. (wire red hot then finally melting to open the circuit) then it is not too close to GRP or anything that could butn to start a fire.
Cars were built for many years with no fusing in the starter wiring. Despite higher risk of short due to much metal bodywork connected to negative. Though less risk of fire due to metal structure. Apparently an acceptable risk and not many fires caused by electrical problems.
I am just suggesting that fuses can be really unnecessary in some places and in themselves introduce a likely hood of failure of an electrical cuircuit. It needs to be a well informed decision regarding fusing or not. olewill
 
William_H said:
The starter large drain will be less on the new batteries because the thinner wires will cause a volt drop or restrict current from the new batteries. This will not matter much in terms of ballancing batteries if the new batteries are newer than the old ones anyway.

No not meant as tongue in cheek. Logically if the wires are well supported so that there is no chance of a short +ve to -ve then you should not get overheated cables. However you can also ensure that if overheat occurs. (wire red hot then finally melting to open the circuit) then it is not too close to GRP or anything that could butn to start a fire.
Cars were built for many years with no fusing in the starter wiring. Despite higher risk of short due to much metal bodywork connected to negative. Though less risk of fire due to metal structure. Apparently an acceptable risk and not many fires caused by electrical problems.
I am just suggesting that fuses can be really unnecessary in some places and in themselves introduce a likely hood of failure of an electrical cuircuit. It needs to be a well informed decision regarding fusing or not. olewill
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That sounds like a recipe for disaster. I'll stick to proper sized cables and fuses.
 
pvb said:
Interesting theory perhaps, but hugely complicated and many additional connections at battery posts. At the end of the day, not practically worthwhile. Just taking the feeds from each end of the bank suffices.
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Beg to differ. I recently installed an extra battery and followed Smartgauge's method. There are no additional connections and it's not very complicated. It works well for me.
 
i have two leisure batteries on my small intro 22 yacht. they are each going to a battery selector and can be ran together or individually, how can i add another battery?

thanks
 
Just connect it in parallel with one of the other batteries.

However, unless you have sufficient power being generated to charge all three batteries, it probably wouldn't be worthwhile.
 
Rigger Mortice said:
Just connect it in parallel with one of the other batteries.

However, unless you have sufficient power being generated to charge all three batteries, it probably wouldn't be worthwhile.
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I had not given much thought to the charging regime, especially the fact ( which I knew but hadn't considered practically) that the last 20% of charge takes proportionally far more charging time than the first 80% a third battery may have the advantage of delivering the storage you require from less charging time 3 batteries charged to 80% for less time than 2 to 90% ??
 
pcatterall said:
I had not given much thought to the charging regime, especially the fact ( which I knew but hadn't considered practically) that the last 20% of charge takes proportionally far more charging time than the first 80% a third battery may have the advantage of delivering the storage you require from less charging time 3 batteries charged to 80% for less time than 2 to 90% ??
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It all depends on how you are using the batteries.

If you were to end up only ever charging the batteries to 80% you'll not be doing them much good in the long run. Batteries need to be fully charged on a regular basis and if you add another battery it will take even longer to fully charge them.

Just adding another battery isn't necessarily the best approach. Two properly charged batteries may be better than three poorly charged batteries.
 
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