wiring advice (1 Viewer)

[beltsandbraces]

bought a pure sine wave inverter and works a treat, surprised how little a tv uses. anyway I have 2 130 amp batteries and I have attached live and earth to just one of the batteries. Should I have connected the live to one battery and the negative to the other one or does it not really matter.
Thanks in advance.

 

[Richard n Ann]

Yes positive to one battery, negative to the other to balance the load. Wouldn't have thought it matters much though if you've just got a TV on it.

Edit:
This is how you're supposed to connect the terminals to the van too.

 

[Rollin]

Wouldn't the two batteries be connected in parallel? In which case, the positive of each should be connected to the positive of the other, and same for negative - therefore it wouldn't matter?

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[Richard n Ann]

Yes in parallel but you take one connection from each battery. Doesn't make much difference I know, but that's the 'by the book' way. I suppose it's for when there is a long line of batteries really.

 

[rosalan]

I believe that it is most important to keep the wires to the inverter as short as possible

 

[SuperMike]

I believe that it is most important to keep the wires to the inverter as short as possible

And as big as practical.

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[Stealaway]

surprised how little a tv uses.

My 24" draws about 6 amps but I won't let the battery voltage drop below 12.4V so as not to over stress the batteries.
I can watch TV for over 3 hours if there is no other demand on them like the central heating.
Keep an eye on the voltage, you can only have out what you put in on a daily basis.

 

[Rollin]

I won't let the battery voltage drop below 12.4V so as not to over stress the batteries

One thing I've not yet understood - is that 12.4V under load? Or with no load after leaving the battery to settle for an hour or so?

I did once see my battery voltage at 12.5V after I'd been watching a movie for an hour or two, so I quickly shut everything down in a panic and sat there in the dark biting my nails.

I'd been driving for a couple of hours so the battery should've been fully charged - however I did have the fridge running from the alternator while driving - the first time I'd put it on so maybe it was sucking up all the power and not letting the battery have any? No idea if it works like this...

 

[Rollin]

I found this article very well written and it seems to answer my questions.

On page 6, it says when taking a reading of the leisure battery charge state:

• All electrical appliances should be switched off. If you don’t want to disconnect a clock, an alarm that runs from the battery, a fridge’s fascia controls or similar, the reading will not be completely accurate. Obviously this is not an issue if you’ve removed a battery and transferred it to a work bench.
• If you have recently disconnected a charger or have been driving a motorhome or towing, a reading will be higher than normal. After a battery has been receiving a charge, it is recommended to let it settle for at least four hours before taking a voltage reading.
• Now you need to interpret the reading and although we talk about 12V batteries and accessories, this description is only nominal. If a leisure battery achieves a 12V reading, it is considered to have reached a discharged state.

As a rough guide, work to the following table:


Voltmeter reading Approx state of charge
12.7V or over --> 100%
12.5V --> 75%
12.4V --> 50%
12.2V --> 25%
12V or under --> Discharged

Which suggests that while you have to wait 4 hours after stopping charging the battery before taking a reading, you don't have to wait after shutting off any load.

Also my 12.5V reading wasn't as critical as I'd thought, as it still indicated 75% charge. However the difference between that and 12.4V is really only a small difference in the voltmeter position.