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Fuenkli

Partial State of Charge

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Going through the first Cape Town winter with my battery bank (8x200Ah 12V VR Lead Carbon). On cloudy days the batteries do not fully charge anymore. Today for example they started in the morning with 60% SoC and now they are only at 65% SoC :(. I red, that a prolonged partial state of charge will lead to sulfation and permanent capacity loss. What is prolonged PSoC? After how many days PSoC should I fully charge the batteries?

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I think the recommendation is that your batteries should float once a week. Not something that we have an issue with here in the Karoo :P.

TTT?

I would just charge from the grid. It is not Survivor.

 

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4 hours ago, Chris Hobson said:

I think the recommendation is that your batteries should float once a week.

I've heard arguments that says sulfation may start as early as 24 hours after entering a partial state of charge condition. Obviously some batteries are designed to be somewhat resistant to it, and some sulfation can be reversed (one has to remember that the layer of sulfate that forms on the plates are normal, that is how the battery works.... the trouble is it becomes permanent after enough time). So... the number is somewhere between every day and once a week. Definitely not more.

During the winter months, my recommendation would be to move your cut-off upwards so they get a good charge every other day at least.

4 hours ago, Chris Hobson said:

I would just charge from the grid. It is not Survivor.

No shame in doing that.

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Thanks Chris and Plonkster for your replies. Very good advice. I will move the cut off SoC upward until I find the sweet spot for the batteries to float at least twice a week.  

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48 minutes ago, Fuenkli said:

find the sweet spot

For the blue kit we have an algorithm called BatteryLife that deals with that. Whenever the batteries fail to reach 85% on a day the lower limit is increased. There is a bit more to it, and the source is open if you want to check it out... but that's why we have it, for cases like these. Naturally much more important in Europe.

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