Re: Battery switches - what do they do?


Dave Bulllar wrote:
"Rich" <richard.bird2@xxxxxxxxxxxxxx> wrote in message
news:fjipd2pbvk4bagb5kf0lbc27hcs9r6hopu@xxxxxxxxxx
On my Centaur I have a main battery switch and two batteries. I
always thought they were to isolate the circuits and protect the
engine battery. There are Off 1 Both 2 switches. I always start the
engine on 1. I thought all circuits would be off when this switch was
on off - however I find taht can use my general switches eg lights
radio etc and they all work. I then read in a book that this was the
charging order for batteries but you should never have both on when
charging. I am now confused what does the battery isolator do and I
want to ensure taht my domestic stuff does not draain my engine
battery. Any advice
Thanks
Rich
Westerly 2219 DAVICO

Look at the connections behind the 1,2 both switch - the terminal where the engine main pos lead is connected is the common. If that's the only lead on there then the switch will only isolate the engine when in the off position. If the service supply was connected there, then the switch would isolate it.

The other two terminals are battery one, battery two main pos leads.
Are there any extra wires connected to these ?

You may find the service is connected directly to the battery 2 itself,
or the batt 2 terminal of the rotary switch - rather than the common.

In fact - if you don't have an extra wire feed on the battery 2 itself,
then the service 'must' be connected to the battery 2 terminal on the
switch. After all - its getting power from battery 2 somehow - and the
only place it can connect, without being isolated by the rotary switch,
is either the battery end or the rotary switch end, of the main pos
lead from battery 2 to the rotary switch.

Is there any form of main switch to the service supply ? If not, there
should be.

I have my service connected to the battery two switch terminal, rather
than the common -then have a separate circuit breaker for the service
isolation next to the rotary switch. This is just for neatness -
essentially service supply is wired direct to battery 2, via a 30amp
circuit breaker, which acts as an isolation as well ( Maplins, 24ct
gold plated, about a fiver - car hi-fi stuff )

The rotary switch only isolates the engine supply and switches to 1 or
2 for starting or charging. I don't use it on 'both'.

If you use the rotary switch as an isolator for both - then your
service supply would connect to 'common', along with the pos lead from
starter.
When on 1, the engine starts from 1, charges 1 and the service supply
is fed from 1 - similarly with 2.
This is not ideal, as if you forget to switch it to 2, you can drain
the engine battery.

With the service direct to battery 2 terminal - then I can never drain
the engine battery form service load, unless I left it on 'both' -
which I never use.

If my service batteries were dead flat, and there was a desperate need
for power from the engine battery, which is a pretty unique situation,
then I could just swap the leads easily, being bronze wing nuts and
spring washers. The 'both' setting would just flatten the other under
those circumstances.

The rotary, really is only used as a means of switching the charging /
starting - and as an isolation switch for engine supply.

Hope that helps - I found all this battery charge stuff a minefeild of
different options - and widely varying technical opinions.

.

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