Battery life measures same 2.5 yrs for the last 2 years? Why?

Battery life

by AgentX86 - 2023-02-24 23:52:42

The reported time left is just a guess.  The voltage on these batteries doesn't change at all until right at the end.  Any meaurements aren't all that useful so the PM guesses.  I don't know how long you've had the PM but you might find it falling off more rapidly at some point.

because it's a guess

by Tracey_E - 2023-02-25 10:05:59

Pacer batteries aren't like a tank of gas that goes down gradually so you know exactly how many miles are left in the tank. Any time they tell us is just a guess. Once it shows under a year, they will start checking it more often. Or if you have a home monitor, it will tell them when it's closer to the last 3 months. 

I'm on #5. I've had them say close to a year but then 3 months later it's time. I've had them say 6-12 months for close to 2 years. Maybe some day they'll invent a battery that's easier to predict, but that day is not here yet!

Battery life

by piglet22 - 2023-02-25 10:40:04

The non-rechargeable lithium battery, or cell can have voltages up to 3.7-volts depending on the chemistry.

One of the characteristics of lithium cells is their ability to output a a fairly stable voltage under load.

Medtronics give cell voltage versus time charts for pacemakers like Endura and they quote a lifetime of 9.2-years.

The chart shows a characteristic fairly sharp drop-off at end of life which happens in say several months.

Despite 3-monthly monitoring, my cardiac people still managed to let it fail completely while at home.

There will be device in the PM called a microcontroller which does all the clever stuff. These have all sorts of inputs and outputs, both analogue and digital, plus memory.

Measuring cell voltage is not like an old meter with a scale and a pointer.

It will have a device called an analogue to digital convertor (ADC) and these measure in steps, typically 1024 so the voltage will be divided into these steps. If the voltage is slightly unsteady, the apparent voltage may jitter because of the ADC steps, so remaining the same or falling then rising isn't unusual.

What is important is when it gets to the knee at end of life, then you will see or be told, drops in voltage that do matter.

The impressive thing is just how little current these devices use, allowing them to last for years.

If the PM has Bluetooth then transmissions can use significant energy. You may see on bedside monitors the letters BLE which is Bluetooth Low energy.

Battery Life

by heatherine008 - 2023-03-05 00:32:17

I saw my cardioligist in August 2021 - the PM said I had 18 months battery life.  In February 2022, I started to get a very strange feeling, initially I thought I was having a heart attack, so took myself off to A&E - the ECG was normal, so I concluded I wasn't and started to believe I was having anxiety attacks and didn't stay in overnight as per the doctor's request.   I only use the pacemaker about 10% of the time, so the chances of a 1 min ECG picking something up were slim.  Roll on 6 months and at my check up, my pacemaker battery had stopped working properly around the time of my A&E visit!  The battery went into end of life emergency mode. I had no idea, but should have known.   So, just keep a watchful eye on it,  any strange feelings, stay in over night!  Don't worry too much though, whilst not working properly, the end of life battery mode does keep you going and it's a strange feeling, so just be wary of it!

Good luck!

Heatherine

by piglet22 - 2023-03-08 06:31:55

How interesting.

I too had a pacemaker change mode when the battery voltage dropped dramatically at end of life.

My symptoms were muscle twitching.

Just as you say, don't go out if you suspect things aren't quite right and be wary of people making assumptions from ECGs.

I've had a running battle with the automatic interpretation that comes with modern ECG monitors which was reporting three types of infarction, hypertrophy, block etc. etc., all the symptoms of a heart attack.

It worried me stiff.

My GP called me today about it. Apparently the ECG doesn't know if you have a pacemaker and looks at the rubbish traces and reports that you are deaths door.

There's a relief.

battery life remaining vs capacity used

by brady - 2023-03-20 18:29:10

"Battery life by piglet22 - 2023-02-25 10:40:04" gives a very good answer.

To my knowledge, the output voltage of lithium battery is used to estimate the remaining battery life. The output voltage vs capacity used (%) plot shows that when the capacity used is near the end of life, the output voltage drops off sharply (sudden death?) to a value unable to power the pacemaker. But before that point, the voltage drop off slowly making it harder to accurately estimate remaining battery life (pointed out by by AgentX86). But this is for lithium ion batteries.

(https://www.batterypowertips.com/how-to-read-battery-discharge-curves-faq/)

Pacemaker battery uses lithium mixed with other elements. I would assume the discharge behavior of these batteries is similar to lithium ion batteries. 

"First introduced in 1975, Lithium Iodine batteries are currently being used and have extended pacemaker battery life to over ten years in various models. These batteries have the required long battery life, low drain current, and voltage characteristics. The newer magnetic resonance imaging (MRI)- compatible pace- makers use the lithium silver vanadium oxide hybrid battery or lithium carbon monofluoride (CFx) battery. CFx batteries have been reported to offer higher energy density and can be pulsed at currents above 20 mA.8 Depending upon the percentage requirement of pacing, these newer MRI compatible pacemakers have an expected battery life of 12.6 years to >15 years for both VVI and DDD pacemakers."

"Longest lasting VVI pacemaker on the Indian subcontinent: Over 28.1 years of pacing without requiring pulse generator replacement", Rajneesh Calton and others

https://www.sciencedirect.com/science/article/pii/S2468600X17301652