Tuesday 15 April 2014

12.6 and falling

My experiment to see just how much our battery bank loses overnight powering just the fridge via the inverter yielded a somewhat inconclusive result. I disconnected the mains lead, and the voltmeter showed 13.3 volts, dropping quickly to 13.2. That seemed OK for fully charged sealed batteries. After 8 hours the voltage was down to 12.6. I'd forgotten to disconnect the mobile broadband unit, but it probably takes relatively little.

Now some of the charts I've seen on the internet would suggest that a 0.6 volt drop overnight is an appreciable amount of the batteries' capacity, so I rang the Evesham battery people to ask them. Unfortunately, Steve Smith the boss, who's been very helpful in the past, is away till after Easter. Eventually I spoke with Curtis, who installed stuff for us last June and is a mine of information. He thought the voltage drop wasn't excessive. So we haven't taken the batteries to Evesham, and the timing means that we probably now won't, unless plans change and we cruise down there later in the year.

Well – I'm back to thinking about getting (a) a proper battery monitor, and (b) a solar panel. Everybody who has them says they are really worth it. I think the battery monitor is probably first on the list – some genuine data would be really nice. It's the uncertainty that taxes the emotions.

5 comments:

  1. Hi,
    Just to help with your battery figures;

    12.7v-ish is fully charged for a rested battery (so a battery that's had nothing put in or out of it for at least a couple of hours).

    12.2v (again rested) is 50% charged.

    When the battery is on charge, you might see a voltage as high as 14.8. When the battery is being used, you may see it dip to 11.9.

    Hope that helps.

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  2. Oh, and as far as a battery monitor is concerned, I would highly recommend the Smartgauge made by Merlin.
    The Smartgauge designer has a great website for all things electrical too: http://www.smartgauge.co.uk/

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    Replies
    1. Ta! Smartgauge is certainly one of the systems I've been looking at. I've been back to their website many times to try and sift genuine science from the points where "the lady doth protest too much".

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