Different battery readings

pvb said:
I don't, simply because they require correctly setting (and resetting), and are therefore liable to be left on the wrong setting, potentially leading to a flat start battery. But it's not just me - most new boats are now fitted with simple on/off switches for the engine and domestics, rather than the old-fashioned 1-2-Both switch.
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Yep... removes user error for sure... but also removes flexibility.
 
Phoenix of Hamble said:
It would appear that PVB doesn't like 1-2-both switches, but this gives me a degree of flexibility that offers many benefits,
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Seems a very complicated way of getting flexibility. Much more simple to have an engine start and a separate house bank, individually switched and a way of combining such as a parallel switch so that that you can start the engine with the house bank. Start battery needs very little capacity so does not make sense to rely on it for house duties, but paralleling it would allow you to access that capacity in an emergency.
 
VicS said:
For a simple method of managing a basic two battery system there is nothing wrong with a 1 2 both switch. Similarly nothing wrong with two separate switches if that is your preference but it's irrelevant to helping the OP sort out his problem.
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However, if they did not exist don't think anybody would "invent" them given the superior systems available now. Can't remember the last time I saw a new boat of any size fitted with one.
 
Back to OP question. If he thinks the batteries are linked together (switch on "both" position) and gets different voltages on each battery then clearly they are not linked together. A failure of a connection of a battery would explain why that battery would not start the engine. Problems cam occur at the battery terminal +ve and -ve and at the switch terminal.
good luck olewill
 
Tranona said:
Seems a very complicated way of getting flexibility. Much more simple to have an engine start and a separate house bank, individually switched and a way of combining such as a parallel switch so that that you can start the engine with the house bank. Start battery needs very little capacity so does not make sense to rely on it for house duties, but paralleling it would allow you to access that capacity in an emergency.
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Yes, but if, for example, my starter battery collapses completely, and my house batteries aren't at a high charge level, I can try and start off just the house batteries, without the starter battery dragging them down.
 
Phoenix of Hamble said:
Yes, but if, for example, my starter battery collapses completely, and my house batteries aren't at a high charge level, I can try and start off just the house batteries, without the starter battery dragging them down.
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Does anyone have a reference for this 'dragging down' effect? When in the trade, I'd never disconnect the car battery when jumping (for obvious reasons) and the low battery seemed to contribute to the overall power.
 
VicS said:
... least likely, a defective selector switch.
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I have a symmetrical pair of batteries with a one two both switch. It works fine for me. It didn't when I first installed it. It took me for ever to find out that the problem was the switch. It was new, and I never expected it to be defective. It was.

(Symmetrical system works for me because general purpose engine can easily start my tiny engine - and if it doesn't I can hand start it.)
 
Phoenix of Hamble said:
Yes, but if, for example, my starter battery collapses completely, and my house batteries aren't at a high charge level, I can try and start off just the house batteries, without the starter battery dragging them down.
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That's a good point to make; many emergency parallel switches aren't wired this way - instead, they parallel the (good) house batteries to the (bad) start battery. It's easy though to wire the emergency parallel switch so that the power goes straight to the starter (see diagram below). A foolproof way of ensuring this is to use the simple on/off switches with removeable red handles, and only have 2 handles for the 3 switches. In order to start the engine from the house batteries, you take the red handle out of the engine battery switch and use it to operate the emergency parallel switch.

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"A foolproof way of ensuring this is to use the simple on/off switches with removeable red handles, and only have 2 handles for the 3 switches. In order to start the engine from the house batteries, you take the red handle out of the engine battery switch and use it to operate the emergency parallel switch."

Easy? Imagine getting your head round that for the first time in earnest, eg with a dead engine in a TSS....

I have a diode splitter and just keep the 12B on 'house' all the time (when on board) knowing I have a healthy 'start' battery if I get the dreaded 'click'
 
pvb said:
That's a good point to make; many emergency parallel switches aren't wired this way - instead, they parallel the (good) house batteries to the (bad) start battery. It's easy though to wire the emergency parallel switch so that the power goes straight to the starter (see diagram below). A foolproof way of ensuring this is to use the simple on/off switches with removeable red handles, and only have 2 handles for the 3 switches. In order to start the engine from the house batteries, you take the red handle out of the engine battery switch and use it to operate the emergency parallel switch.

wiring3_zpsacdd1a9c.jpg
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Yes, that's effectively how i'm using my 1-2-both switch, but can also choose to run the house from just the engine battery (although I can't see a particularly likely scenario for needing to do that!)
 
NickRobinson said:
"A foolproof way of ensuring this is to use the simple on/off switches with removeable red handles, and only have 2 handles for the 3 switches. In order to start the engine from the house batteries, you take the red handle out of the engine battery switch and use it to operate the emergency parallel switch."

Easy? Imagine getting your head round that for the first time in earnest, eg with a dead engine in a TSS....
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I didn't say it was easy, I said it was foolproof! Although, if the emergency switch is mounted near the engine switch, it shouldn't be too difficult. Importantly, if the engine start battery is separated and dedicated, the chances of suddenly finding it flat are very low indeed. Batteries rarely just fail, they drop in capacity and suffer a lingering death, so a dedicated start battery on its way out should be noticed.
 
Sorry but I cannot resist commenting on the 1- both - 2 switch controversy. Have this type of switch and cannot think anything can be simpler. (Fwiw, we never use the both position). It is just so easy to see at a glance which battery is being used/charged and also easier to explain to crew so that there is always a battery connected. Maybe one reason they are not now fitted to new boats is that they are expensive.
 
Storyline said:
Sorry but I cannot resist commenting on the 1- both - 2 switch controversy. Have this type of switch and cannot think anything can be simpler.
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With two simple on/off switches you can just arrive at the boat, turn both on, use the boat as you wish, for as long as you wish, then turn them both off when you leave the boat. No need to make any switch changes when starting the engine, after starting, during charging, after stopping the engine, etc. That's surely simpler?
 
pvb said:
With two simple on/off switches you can just arrive at the boat, turn both on, use the boat as you wish, for as long as you wish, then turn them both off when you leave the boat. No need to make any switch changes when starting the engine, after starting, during charging, after stopping the engine, etc. That's surely simpler?
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My set up is just the same... turn on the switches for the house and engine batteries.... I can then chose to change the status quo with the 1-2-both switch if I need to... the only way you can get it wrong is by setting the 1-2-both switch for an unusal situation, and then forgetting to change it back... unlikely
 
pvb said:
With two simple on/off switches you can just arrive at the boat, turn both on, use the boat as you wish, for as long as you wish, then turn them both off when you leave the boat. No need to make any switch changes when starting the engine, after starting, during charging, after stopping the engine, etc. That's surely simpler?
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It does seem simple but how do you ensure just one battery bank is charging ? Do you have to turn a switch off - if so surely there is a risk that a crew member will get confused and switch both off.
 
Storyline said:
It does seem simple but how do you ensure just one battery bank is charging ? Do you have to turn a switch off - if so surely there is a risk that a crew member will get confused and switch both off.
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Charging is automatically controlled by a diode splitter or a VSR, both of which ensure that one battery/bank can't discharge into the other battery/bank.
 
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