Bringing together house, engine and bow batteries?

[Tim Good]

I have a large switch for my batteries with 4 options and allows me to combine them if for example one set were faulty or emergency:



Off - Not off but system only using the house bank of 4 trojans*
1 - house and bow
2 - house and engine
Both - all together

I have a few questions to better understand them:

1
Do batteries balance the charge between themselves together in the same way a diving air cylinder would if combined and left for a while.

2
Is is bad practice to bring them all together for long periods given that some are flooded and some are AGM. If I select Both and leave them like that while I’m away the solar array (500w) will charge them all since the solar panels are wired directly to the house bank.

3
when I bring them together then the house bank shows a negative amp draw and the other two a positive amp inflow. Is that the batteries balancing the charge between them?

* edited as not obvious originally.

 

[TernVI]

1) Not really
2) Yes
3) Not Quite Exactly.

 

[vyv_cox]

That's a most unusual combination. It makes far more sense to keep the house and engine banks separate. You can then run the domestic bank completely flat if you like (not recommended) but you can still start the engine.

My method is that I leave the starter battery basically as an emergency only. The domestic bank is plenty capable of starting a small engine, so I leave the switch on that. The starter battery is switched a couple of times per week, run for half an hour to replace the start charge, then back to domestic, where it remains. I never switch to both, this is asking for trouble.

 

[pvb]

That's a most unusual combination. It makes far more sense to keep the house and engine banks separate. You can then run the domestic bank completely flat if you like (not recommended) but you can still start the engine.

My method is that I leave the starter battery basically as an emergency only. The domestic bank is plenty capable of starting a small engine, so I leave the switch on that. The starter battery is switched a couple of times per week, run for half an hour to replace the start charge, then back to domestic, where it remains. I never switch to both, this is asking for trouble.

It is unusual! It appears that there's no way of isolating the house batteries.

 

[PaulRainbow]

Worse than unusual, it doesn't make sense.

Setting to 1 combines the house and bow batteries and every thing runs from them, including the engine ?
Setting to 2 combines the house and engine batteries and every thing runs from them, including whatever is at the bow ?

2
Is is bad practice to bring them all together for long periods given that some are flooded and some are AGM. If I select Both and leave them like that while I’m away the solar array (500w) will charge them all since the solar panels are wired directly to the house bank.

Extremely bad practice, it's a disaster waiting to happen. With the switch in the both setting every battery is connected in parallel, a problem with one will affect the others. If one cell shorts in just one battery, 500w of solar will boil every battery on the boat, killing the lot in one go.

I'd suggest you think about separate switches, on for each bank, with an emergency switch between the house and engine banks. Then have a think about how you achieve your split charging.

 

[VicS]

It is unusual! It appears that there's no way of isolating the house batteries.

The switch is labeled "Battery charger distribution switch Normally leave in the OFF position"
Hopefully that is the sole purpose, that there are also separate isolation switches and that this switch does not control the use of the batteries.

 

[dansaskip]

I think it might be time to rethink and redesign your switching system and perhaps invest in something like a BEP switch cluster or equivalent to properly isolate the batteries and get a more balanced charging system. As others have said your present set up doesn't make sense.

 

[Tim Good]

That's a most unusual combination. It makes far more sense to keep the house and engine banks separate. You can then run the domestic bank completely flat if you like (not recommended) but you can still start the engine.

My method is that I leave the starter battery basically as an emergency only. The domestic bank is plenty capable of starting a small engine, so I leave the switch on that. The starter battery is switched a couple of times per week, run for half an hour to replace the start charge, then back to domestic, where it remains. I never switch to both, this is asking for trouble.

Vyv - Off is just the house bank. This is what it is set to 99% of the time. I mentioned that in the original post but perhaps it isn't obvious.

 

[Tim Good]

Worse than unusual, it doesn't make sense.

Setting to 1 combines the house and bow batteries and every thing runs from them, including the engine ?

No the engine will still run from the engine battery, bow from bow and so on. But if I select 1, 2 or both then it draws them together for emergencies. the Off setting separates them all. So with Off then the house batteries run the systems but not the engine or bow.

Setting to 2 combines the house and engine batteries and every thing runs from them, including whatever is at the bow ?

This just combines the house to the engine in case the engine battery goes flat and enables me to still start it.

Extremely bad practice, it's a disaster waiting to happen. With the switch in the both setting every battery is connected in parallel, a problem with one will affect the others. If one cell shorts in just one battery, 500w of solar will boil every battery on the boat, killing the lot in one go.
I'd suggest you think about separate switches, on for each bank, with an emergency switch between the house and engine banks. Then have a think about how you achieve your split charging.

What would be the way to split charger the solar between the three banks?

 

[pvb]

Vyv - Off is just the house bank. This is what it is set to 99% of the time. I mentioned that in the original post but perhaps it isn't obvious.

So how do you isolate the house bank?

 

[Tim Good]

So how do you isolate the house bank?

If the Switch is set to "Off "then the House Bank is isolated from the other two banks and the boat systems run only from the house bank. The engine remains on the engine battery and the bow runs the thruster and windlass. All three bank isolated when "Off" is selected.

 

[pvb]

If the Switch is set to "Off "then the House Bank is isolated from the other two banks and the boat systems run only from the house bank. The engine remains on the engine battery and the bow runs the thruster and windlass. All three bank isolated when "Off" is selected.

I think we have a different definition of the meaning of "isolate".

 

[Tim Good]

I think we have a different definition of the meaning of "isolate".

Ok please can you ask the question again using your definition and I'll try to answer correctly.

 

[LadyInBed]

As all have said your setup isn't ideal!
As I see it, you have two separate problems to solve.
1 Charging 3 batteries from your solar automatically whilst you are away from the boat
2 Charging 3 batteries from your alternator

1 I don't think there is a 3 output solar regulator so you could use a 2 output solar regulator, 1 output to the house bank and the other through split charge diodes to the engine and bow battery. I'm sure Paul will say if this won't work.
2 Direct the alternator output through a conventional 3 way make before break rotary switch or split charge relay.