Campervan dual battery monitor

[fixedfixer]

I’d like to wire in a voltage meter that shows the condition of both main and leisure battery. Something like this, Monitor. Now I don’t want it on 24/7 draining the batteries. It has three terminals, one each for the positives and a common negative. Would a simple on /off rocker switch on the negatives solve my issue?

Apologies for what is probably a very basic question for you folks but I’m not a electrical wizard

 

[Barking Mat]

Yes, shouldn't be an issue.

 

[fixedfixer]

@Barking Mat thanks.

 

[voipio]

Better to have a two pole switch to disconnect both positives. If only the negative is switched, it may be possible for current to flow between the two batteries, e.g. when there is a high current draw from one battery or the other, possibly damaging the meter circuitry.

 

[julianf]

I've always been lead to believe that a simple voltage check is quite a uninformative way to monitor a batteries health.

But, yes, if all you're doing is checking the voltage, then a dual pole switch, as suggested above, would, I'm sure, be fine.

 

[MoreWellie]

I haven't checked to see what is available but if you can find a suitable momentary double pole push button it would save you leaving it on accidentally

 

[finyuk2005]

I've always been lead to believe that a simple voltage check is quite a uninformative way to monitor a batteries health.

But, yes, if all you're doing is checking the voltage, then a dual pole switch, as suggested above, would, I'm sure, be fine.

it isnt very accurate as especially lead acid batteries voltage will drop if there is any load on at the time you check the voltage,
Its handy enough for giving you a rough idea though, handy for keeping an eye on the charging system too

 

[fixedfixer]

Thanks for advice, it’s just a simple quick check I’m after. Unfortunately the split charge relay failed recently and went un noticed until the fridge stopped work - you’ve guessed it whilst on holiday. As the van is a daily runner, it would be nice to have a quick check ( when I remember) to see all is working.
Double pole sounds the way to go.

 

[fixedfixer]

Sorry for yet another novice question. Is this what’s required? Double Pole Momentary

I assume this will keep both batteries independent, be in off position unless pushed?

Thanks again. (I may well be needing some help relating to wire positions (a1 a2 a3 b1 b2 b3).

 

[MoreWellie]

I assume this will keep both batteries independent, be in off position unless pushed?

Correct, which is why I suggested momentary as it only makes contact when the switch is held in the pushed position

That switch is double throw which means it will connect the centre pins to the corresponding end pins in the direction it is pushed. You just ignore the pair of contacts at one end or the other

Whilst your linked one would work fine it might be simpler to use something like https://uk.rs-online.com/web/p/push-button-switches/7346763 as it just has a push rather than switching in two directions and also needs a round hole rather than a rectangular one

 

[fixedfixer]

@MoreWellie thanks. I’ve already got blank rectangle places on the dashboard. I was thinking double throw to push up for starter battery and down for auxiliary. Both circuits would be independent and therefore no chance of problems between the two batteries as cautioned against earlier in the thread. Give me mechanical things to sort any day but electric even basic is a challenge

 

[MoreWellie]

in that case you could get a cheaper voltage meter as you wouldn't need the double one you linked to and just use the three pins along one side of the switch connecting the meter to the centre pin and the batteries to the outside ones. It also means you could buy a single pole version of that switch

there is never just one solution

 

[fixedfixer]

Thanks