# How is SOC measured?

• posted

What is/are the method(s) used to determine the SOC (state of charge) of batteries used in cell phones, tablets and other small portable electronic devices so it can be indicated to the user?

Thanks guys,

Jeff

```--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE) ```
• posted

Coulomb counter. A chip counts electrons going in and out of the battery. For example:

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com ```
• posted

Yes, though it helps if the battery is captive or if interchangeable, then serialized. You want to keep the history of a particular battery. Some algorithms try to factor in the number of cycles.

Basically an unhealthy battery has poor charge efficiency.

• posted

Thanks.

I thought it had to be something like that but was unaware that there were ICs that handled the whole job.

Jeff

```--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE) ```
• posted

"jeff_wisnia"

** There is no way to measure or determine remaining capacity other than by discharging the battery.

So equipment makers resort to predicting it by keeping track of the charging time and discharge energy since last charge.

Bit like predicting the weather .........

.... Phil

• posted

Ok, so, instead of rating them as 10 AH (10 amp hours) we can now use the term 10 AH = 36000 C(coulombs)/H, not to be confused with light speed :) Sounds like a marketing scheme!

Jamie

• posted

Smart Battery Specification

Battery Firmware Hacking: Welcome to the dark side.

Someone probably wanted to call it an electron counter, until someone else noticed that the electrons were going the wrong direction. Counting holes didn't sound very impressive. So, what was left was counting coulombs.

As a joke, I once suggested that a client rate their portable radio batteries in terms of horsepower in order to give the buyer a more familiar term for the "power" of the radio. For example, the NiCd battery pack of the day was about 12V * 0.600A = 7.2 watts

1 watt = 0.00134 horsepower Therefore, this would be roughly a 0.01 horsepower battery. Unfortunately, management seriously considered my horsepower rating, where it might become some kind of sales advantage. However, they were not thrilled by the resultant small numbers. So, I suggested millihps, where 0.01 hp = 10 millihp. Fortunately, that killed the idea before anyone else took it seriously.

Since then, the auto industry has gone the other direction, starting with small hp numbers, and translating engine power into much larger horsepower numbers. (Bigger numbers are better).

```--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com ```
• posted

Coulombs, but not /H.

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John```
• posted

Threshold (Nelson Pass's old company) used to make a one horsepower audio amplifier. I can't find it on the interwebs due to too many people talking about horsepower in a general rather than literal sense. That is, too many false positives from google.

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