Disco 2 Battery moniter

Hi all, has anyone fitted one of the Sealey battery monitoring devices (to any vehicle) ?
I fitted one a few weeks back & it tells me my D2 battery is losing about 22% of it charge overnight e.g went the Goodwood Revival Sunday & got back about 19.00 & as you would expect the app on my phone for it was showing 100% charged, at 09.30 this morning it's showing 78% charge !
Before I left for GW it was showing 44% & 12.5v as I hadn't used it for a week but it always starts 1st time (before you've let go of the key). Battery C31 -1000 is just over 3 yrs old & done 17,000 miles & the alternator (Hella 120A) is nearly 3 yrs old & has done 15,000 miles. It charges at 14.2v on my MM.
Could this be an early warning for the battery (has 4 yr warranty) or is the BMS not brilliant ?

To start with I’d fully charge my battery and disconnect it from the vehicle overnight, then in the morning get a voltage reading, that would tell me which way to go.

discool said:

To start with I’d fully charge my battery and disconnect it from the vehicle overnight, then in the morning get a voltage reading, that would tell me which way to go.

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+1^^^

Thanks guys, I'll put the 'spare' on just so I can keep it locked/immobilised & do as you say.

Never used one of these devices but from the image, it looks like the SoC is being measured using the Voltage Method. Just keep in mind that this method performs well in a controlled environment (i.e. stable voltage, current and temp conditions), which is of course not the case when installed in a vehicle. Hence the accuracy of the readings are not going to be the best even though the algorithm would account for certain fluctuations. Also, lead acid / AGM / Gel batteries lose on average 10% of their SoC with each 0.12V of open-circuit voltage drop. So just don't be alarmed with certain readings as the conditions are not ideal and the margins are very tight.

NPG said:

Never used one of these devices but from the image, it looks like the SoC is being measured using the Voltage Method. Just keep in mind that this method performs well in a controlled environment (i.e. stable voltage, current and temp conditions), which is of course not the case when installed in a vehicle. Hence the accuracy of the readings are not going to be the best even though the algorithm would account for certain fluctuations. Also, lead acid / AGM / Gel batteries lose on average 10% of their SoC with each 0.12V of open-circuit voltage drop. So just don't be alarmed with certain readings as the conditions are not ideal and the margins are very tight.

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I haven't had a chance to swap batteries yet but 24 hrs later & the truck hasn't been opened or used it's now down to this !
I know it will start 1st time even if I leave it a week, so as you say I'm not overly worried yet as it's still reasonably mild but I know the cold weather will soon impact the battery if it's getting near the end of it's life.

Andy Warren said:

I haven't had a chance to swap batteries yet but 24 hrs later & the truck hasn't been opened or used it's now down to this !
I know it will start 1st time even if I leave it a week, so as you say I'm not overly worried yet as it's still reasonably mild but I know the cold weather will soon impact the battery if it's getting near the end of it's life.

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Have you checked the idle current after 30 - 90 minutes after any door activity? It should be around 20mA or less.

Andy Warren said:

I know it will start 1st time even if I leave it a week,

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It may start but you may see other issues if it get's too low. My TD5 would start no problem but refused to rev beyond tickover due to low volts to the ecu.

PopPops said:

Have you checked the idle current after 30 - 90 minutes after any door activity? It should be around 20mA or less.

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Hi, I haven't yet probably a weekend job now.

backinblack said:

It may start but you may see other issues if it get's too low. My TD5 would start no problem but refused to rev beyond tickover due to low volts to the ecu.

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Hi, I think it was reading about 44% on Sunday when I set off for Goodwood & went fine for the 200 mile round trip but I'll have a better look at the weekend. I use a USB charging thing in the fag lighter which has a built-in volt meter, which was showing the same as my MM 14.2 volts eng. running. Due to the inclement weather I had lights & a/c running + my fridge plugged in (only when the engine was running) .