Wiring 2 sets of seperate battery banks in parrallel. issues

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tonkatoy87uk

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Evening.
Im trying to wire 2 sets of battery banks both sets are in parrallel.

Start batterys- lead acid. I have 2 in parrallel

both start batterys are wired seperatly through a 1,2,both isolator,. for some reason the earth side has an isolator too? with the starter motor earth attatched

wired through the continuous terminal is the winch and starter motor. Off of this inside on the board is 2 bilge pumps, 100w light(for when engine is running/traveling)

wired between the 2 the banks is a cyrix- i 120A battery combiner
https://www.kuranda.co.uk/cyrix-ct-1224v-120a-intelligent-combiner-vcyr010120010-victron


2 of these also in parrallel
House batterys- Deep cycle.
https://www.batterymegastore.co.uk/brands/hankook-batteries/hankook-dc31s.html

wired through a seperate single isolator

both banks are earthed on different parts of the engine. I'm guessing this wont make much difference.

Having a quick readup on the cyrix it links both sets of batterys together when charging.

Would this damage the deep cycle batterys ? Also linking the both banks cause wiring headaches inside. when things are on linking both sets of banks together?
 
Is this with two engines / alternators or one ?

It won't harm the leisure batteries to be linked in parallel to the start batteries whilst an external charge is present, but on a twin engine setup they are normally kept separate, with a solenoid provided to boost the leisure set if they have become over discharged.

If the batteries of the bank are matched and same age then it would be more normal to have them permanently wired as a pair, with one single pole isolator switch, with the maintained supplies (bilge pumps) taken from the battery side of this switch. Perhaps time to bin the 0-1-both-2-0 switch.

Why do you need a 100w lamp ? That is 9 amps of your alternator's output wasted. Easy enough to fit an LED lamp and reduce this to ~10w for similar brightness.

It is perfectly normal to have a combined negative (earth as you describe it). Sounds like the previous owner wanted to be able to entirely disconnect the starter bank with the extra isolator, although this does not make much sense if the same bank is running the maintained services.
 
vm mercruiser 4.2d. 1 alternator. start batterys are just a normal lead acid.

both start batterys are of the same type and age

both house leasure batterys are of the same type and age.



the 1-2 - both switch has both start batterys wired each for a seperate poll for space on terminals (short studs). dunno why, just is. not how i would have done it but it works for now .

boat wiring.png



the 100w light is halogen. chose halogen over led because I wanted a good solid beam rather than a naff spread of random light. led's are ok for a work light. not for distance. were moored up a creak and sit on a mud mooring. plus there is a lot of pots round our way to avoid etc etc etc and is only on when we need it.
 
tonkatoy87uk said:
vm mercruiser 4.2d. 1 alternator. start batterys are just a normal lead acid.

both start batterys are of the same type and age

both house leasure batterys are of the same type and age.



the 1-2 - both switch has both start batterys wired each for a seperate poll for space on terminals (short studs). dunno why, just is. not how i would have done it but it works for now .

View attachment 75465



the 100w light is halogen. chose halogen over led because I wanted a good solid beam rather than a naff spread of random light. led's are ok for a work light. not for distance. were moored up a creak and sit on a mud mooring. plus there is a lot of pots round our way to avoid etc etc etc and is only on when we need it.
Click to expand...

Although a bit unusual, there isn't much actually wrong with that.

The split charge relay is wired incorrectly, it should be connected to the batteries or to the battery terminals of the isolators. As it is, it will close and power the domestic circuits from the engine batteries, even if the domestic circuits are isolated. It won't harm the deep cycle batteries, it's only charging them from the alternator, which is what would charge them whatever you used for split charge.

There is nothing wrong with have the two negative go to different connection points on the engine block.

The bilge pumps could run the engine batteries flat if you had a leak, probably not the end of the World, but not ideal.

The 1-2-B switch is odd, as is having two engine start batteries. You could change this for a single switch and single battery, but it's not doing any harm.

The negative isolator is not needed. I would connect the negative straight to the block and use the switch as an emergency switch. Connect cables from the switch to the load terminals of both isolators. In the event of a flat engine battery you can start the engine from the domestic bank.
 
We have 2 start batterys due to having a big engine and wont start on one battery.

so i just need to move the split charge cables to the battery side of the isolators? 2 min job.

bilge pumps - I'm on top of any leaks in the boat. only a slight drip from the cutlass bearing.
 
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