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kaypea avatar image
kaypea asked

Battery life expectancy - Easysolar system

I have what I thought was a straight forward Victron Easysolar 2GX system. I have connected to it eight XL31S 130Ah Hankook calcium based batteries configured as 4 parallel strings of two batteries in series.

I was under the impression that I would have a resultant power bank of 24v at 520Ah?

Perhaps I'm wrong in my theory, since without any mains power connected, they only last around 6hrs while discharged to 50 % (24.2v). The discharge current averages at around 15amps (between 10 and 18amps nominal). This is following a full cycle recharge until the batteries reach the float stage for several hours.

Where have I gone wrong with my calculations as I estimated they should last more like 20hrs down to a 50% discharge – and not a maximum of 6hrs as I am getting? I don't understand why its such a short time.

All 8 batteries are brand new in the last month.

battery
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mvas avatar image mvas commented ·

24.2 volts may be 50% SOC when no load is attached. You will have to determine what voltage equates to 50% SOC when a 15 amp load is attached.

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JohnC answered ·

Hi @kaypea

Your calcs seem ok, but if you're estimating that '50%' from Voltage, then that's where you're coming unstuck. They're more likely to be closer to 80%+ than 50%.

If they really were down at 50% you'd be seeing serious V sag under load, possibly to the point where they're actually unusable.

Grab yourself a Smartshunt (and tune it) if you really want to know what's going on. Your Easy has an onboard SOC too, but it depends on the rest of your system how useful that is.


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kaypea answered ·

Thanks for your reply John - I'll look into the smartshunt. The 80% would seem more like it. Perhaps I am asking too much from the Hankook batteries as well.

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JohnC avatar image JohnC ♦ commented ·
@kaypea

I didn't really address your 'life expectancy' thing. I'm not a fan of multiple parallel strings of Pb's, as imbalance comes into play, especially as they age. Be gentle with them, maybe back off a little with your charge V's. What you never want to see is them at different temperatures. A touch-test is usually enough to detect that. And I wouldn't plan on taking them below 70% SOC regularly. That's just me, what you do is your choice.

It's not the brand either, this is general stuff.

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