Why does charging voltage need to be higher in lower temperatures for lead-acid batteries?

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greendrake asked May 14, '20

Why does charging voltage need to be higher in lower temperatures for lead-acid batteries?

I came across this blog entry which basically says that, for lead acid batteries, lower temperatures require higher charging voltage. Can anyone please explain why this is true, or point to an authoritative source?

I did ask this question on Chemistry SE a while ago, and those guys seem to be of the opposite opinion: higher temps need higher voltage.

Intuitively I disagree with them and agree with the blog post: lower temps need more power to move molecules around, remove sulphate crystals etc. But I seek a definitive authoritative explanation.

battery charging battery lead-acid temperature compensation

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sulphate crystals etc. But I seek a definitive authoritative explanation.

Answer 1 · 2020-05-14T06:58:12Z

Matthias Lange - DE answered · May 14, 2020 at 06:58 AM

Maybe the "Energy Unlimited" book helps you:
https://www.victronenergy.com/orderbook

Chapter 2.5.9 and 4.4

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greendrake commented · May 15, 2020 at 02:57 AM

This is helpful, thanks! Even though it does not go into details of the underlying chemistry, at least it appears to be reliable source to trust.

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Daniël Boekel (Victron Energy Staff) ♦♦ greendrake commented · May 15, 2020 at 08:19 AM

Hi @Greendrake

If you want 'proof' just read the datasheet of any lead-acid battery, where they will specify the temperature compensation values.

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Answer 2 · 2021-11-29T22:18:12Z

Fra answered · Nov 29, 2021 at 10:18 PM

For me the only reason is that with low temperature, the internal resistance increase, and for charging the same level of current, you need to increase the charging voltage.

With high temperature, the internal resistance decrease and you need to decrease the charging voltage to maintain the same current charging for each voltage.

The charging current that flow into the battery depend of (charging voltage - battery open circuit voltage) / battery internal resistance.

If the battery internal resistance increase or decrease, you need to increase or decrease charging voltage to maintain the same charge current.

These is my reasoning

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