Battery temperature logging - where to put a thermometer?

[jiris]

Monitoring battery temperature is always a good idea and some charge controllers use this input as a part of the data for controlling the charging. From the accuracy point of view, the middle of the casing or on of the terminals will do the best job. Bluetag or silicon rubber will be O.K. - make sure the sensor has a good contact with the surface and there is some layer of glue on the top providing thermo-insulation from the ambient air.

 

[GHA]

Well, lots of lovely data but nothing definitive yet.
Overnight with charger turned off. Batteries (2 x t105) live under the chart table seat so about 05.30 cushion, locker lid and battery box lid were taken off. Quite an obvious increase in cooling rate which suggests a fan could very well help. Lid etc back on a moment ago and charger back on - seems to be slight heating straight away. Though the charger was off yesterday for a little while without such pronounce heating when it went back on..
The other temperature plot is from a lifting lug on the engine so should be lots thermal inertial on there and guessing it's close enough to ambient inside to use as a base line.

Isn't data great!
Been up all night watching it ...
Don't be silly, course not!

With it all on wifi a tablet means you don't have to get up to see whats going on in the boat

 

[Mistroma]

Well, lots of lovely data but nothing definitive yet.
Overnight with charger turned off. Batteries (2 x t105) live under the chart table seat so about 05.30 cushion, locker lid and battery box lid were taken off. Quite an obvious increase in cooling rate which suggests a fan could very well help. Lid etc back on a moment ago and charger back on - seems to be slight heating straight away. Though the charger was off yesterday for a little while without such pronounce heating when it went back on..
The other temperature plot is from a lifting lug on the engine so should be lots thermal inertial on there and guessing it's close enough to ambient inside to use as a base line.

Isn't data great!
Been up all night watching it ...
Don't be silly, course not!

With it all on wifi a tablet means you don't have to get up to see whats going on in the boat

Looks good. My sensor is against the top corner of a battery furthest from the ventilation path. I would have liked to mount it in a more central position on one post but the wire was too short and I didn't get around to extending it. I haven't checked to see if the sensor casing is connected electrically.

I put in forced ventilation to remove hydrogen and also for cooling. It works well and doesn't use much power as it only runs when charging. The fan gets 50% power initially and only gets full power when voltage is high enough for significant gassing. Not complicated, basically a 6V supply from my VSR when it operates and full 12V via a small relay triggered by high voltage (diode stops connection between 12V & 6V supplies).

 

[Jonny A]

Just to add, there are ready-made data loggers out there that less technical people could use straight away:
Thermistor Temperature Display Data Logger - Lascar

 

[GHA]

Looks good. My sensor is against the top corner of a battery furthest from the ventilation path. I would have liked to mount it in a more central position on one post but the wire was too short and I didn't get around to extending it. I haven't checked to see if the sensor casing is connected electrically.

I put in forced ventilation to remove hydrogen and also for cooling. It works well and doesn't use much power as it only runs when charging. The fan gets 50% power initially and only gets full power when voltage is high enough for significant gassing. Not complicated, basically a 6V supply from my VSR when it operates and full 12V via a small relay triggered by high voltage (diode stops connection between 12V & 6V supplies).

Ta.
Just now found another much bigger fan stashed in a locker. 0.3A but hoping pokey enough to only run a fraction of the time. I thought the 3rd yellow wire was PWM but looks like it's RPM out, never mind, simple to fit a FET to and control from an ESP32 then run it for a few seconds or whatever works, not sure PWM would work on the main power feeds.
Must be near time to order another bag of ds18b20 thermometers Already a load fitted, they're clever little devices which you can daisy chain together each with it's own address. So maybe one somewhere to measure ambient and run the fan based on difference between ambient and battery temperature. Anyway, not that difficult to control. Openplotter has an IoT app in development which looks interesting, send an email and turn on the fan when a threshold is reached

Next up once this is working is get the fridge on the internet
(really )

 

[GHA]

Another thought, as it's easy to load signalk onto windows now it would be pretty easy to design a little board to do lots of monitoring and get a handful made by jlcpcb which wouldn't cost much. That could send all the data to a laptop, signalk is not that different in some way to a smart phone, click and load the apps you want.
SignalK/signalk-server-windows

Burning the firmware onto an ESP might be a step too far for many but the electronics side is remarkable cheap these days.

Anyone interested giving a go?

 

[GHA]

I put in forced ventilation to remove hydrogen and also for cooling.

Well that wasn't a great success


What size pipe did you use for the forced air? Pretty sure mine is far too small.. pity, box is in now, oh well.

Charger seemed to get stuck at absorption somehow which looks like it pushed the temperature up quite a bit.

Also interesting was it looks like the tail current went up a little with the temperature which I suppose you might expect being a chemical process, and you can see the charger tweaking the voltage down a little as the temperature rises >

Onwards we go

 

[Mistroma]

Well that wasn't a great success


What size pipe did you use for the forced air? Pretty sure mine is far too small.. pity, box is in now, oh well.

Charger seemed to get stuck at absorption somehow which looks like it pushed the temperature up quite a bit.

Also interesting was it looks like the tail current went up a little with the temperature which I suppose you might expect being a chemical process, and you can see the charger tweaking the voltage down a little as the temperature rises >

Onwards we go

I was quite lucky with access for ducting and was able to get very cheap parts.

1) 1 x 100mm Round Pipe 100mm x 350mm £1.29
2) 2 x 125mm Round Ducting Reducer 125-100mm £1.46
3) 120mm computer fan
4) 75mm Eberspacher Vent Outlet
5) 100mm flexible hose

The 2 reducers are face to face, forming a short 125mm section with the fan inside. I connected up the 100mm pipe on either side. One end goes into the battery box at about 45 degrees and the other connects to the vent. I think the vent is actually 100mm with a step down to 75mm which I cut off to match the 100mm pipe.

I have a 100mm exit hole on the opposite side of the box and flexible ducting leads upwards from there.

My primary aim was to remove hydrogen and any cooling effect would be a bonus. I did some calculations to estimate the likely maximum rate of hydrogen evolution and the volume above the batteries. The fan was capable of moving sufficient air to keep hydrogen concentration well below the LEL. I think it was by a factor of 4-5.

 

[GHA]

Ta.
Slight aside, but if the exit vent went up and out wouldn't any hydrogen rise and leave on it's own accord?

 

[Mistroma]

Ta.
Slight aside, but if the exit vent went up and out wouldn't any hydrogen rise and leave on it's own accord?

Yes, but there will be resistance to flow and a good chance of localised build-up in the space above the batteries in the box. The outlet pipe doesn't go straight up, it angles up and then curves more sharply towards the deck. Hydrogen is pretty good at escaping without help but it is safer to reduce the chance of increased concentration and getting to LEL. Jeanneau didn't fit any ventilation and I have not heard of lots of explosions in the battery compartment. However, the underside of the berth started to blacken significantly in the first couple of seasons. I decided that I'd fit a lid plus forced ventilation to remove corrosive fumes and might as well do enough to play safe with hydrogen concentration at the same time.

It wasn't a big job because I was lowering the base of the box and moving one side a small distance to fit T-105s. Wiring and access to fit ventilation didn't involve much extra work with it opened up anyway.

 

[affinite]

Ta.
Just now found another much bigger fan stashed in a locker. 0.3A but hoping pokey enough to only run a fraction of the time. I thought the 3rd yellow wire was PWM but looks like it's RPM out, never mind, simple to fit a FET to and control from an ESP32 then run it for a few seconds or whatever works, not sure PWM would work on the main power feeds.
Must be near time to order another bag of ds18b20 thermometers Already a load fitted, they're clever little devices which you can daisy chain together each with it's own address. So maybe one somewhere to measure ambient and run the fan based on difference between ambient and battery temperature. Anyway, not that difficult to control. Openplotter has an IoT app in development which looks interesting, send an email and turn on the fan when a threshold is reached

Next up once this is working is get the fridge on the internet
(really )

SO you have the OpenPlotter IOT app. Has it been released ?
My OP Settings panel says IOT "Coming Soon"

 

[GHA]

SO you have the OpenPlotter IOT app. Has it been released ?
My OP Settings panel says IOT "Coming Soon"

Not yet, just saw that screen shot from sailoog on their forum.
So someone else using oponplotter! Yay

 

[geem]

I was quite lucky with access for ducting and was able to get very cheap parts.

1) 1 x 100mm Round Pipe 100mm x 350mm £1.29
2) 2 x 125mm Round Ducting Reducer 125-100mm £1.46
3) 120mm computer fan
4) 75mm Eberspacher Vent Outlet
5) 100mm flexible hose

The 2 reducers are face to face, forming a short 125mm section with the fan inside. I connected up the 100mm pipe on either side. One end goes into the battery box at about 45 degrees and the other connects to the vent. I think the vent is actually 100mm with a step down to 75mm which I cut off to match the 100mm pipe.

I have a 100mm exit hole on the opposite side of the box and flexible ducting leads upwards from there.

My primary aim was to remove hydrogen and any cooling effect would be a bonus. I did some calculations to estimate the likely maximum rate of hydrogen evolution and the volume above the batteries. The fan was capable of moving sufficient air to keep hydrogen concentration well below the LEL. I think it was by a factor of 4-5.

If you are using a computer fan, the performance of the rotating fan in free air as apposed to the installation you describe will be quite different. Computer fans are not designed to work again any static pressure. The slightest resistance will dramatically reduce the volume flow rate. You seem to have enough performance to satisfy you needs, however, to move lots of air you need a centrifugal fan design. These are specifically designed to operate in ducted systems where you experience system pressure drop. If you want high perfomance it takes high amps.
I use a Jabsco bilge blower. This moves a theoretical 118 litres per second. With four T105s is does do some useful ventilation in high ambient conditions but when you are dealing with a hot boat in the Tropics I find leaving the lid off the battery box works better and uses no amps. Overnight the batteries will cool noticeably. With the lid off the battery box there is no hydrogen build up issue either. We have temperature monitoring at the batteries via our Victron Smart solar regulator.

 

[Mistroma]

If you are using a computer fan, the performance of the rotating fan in free air as apposed to the installation you describe will be quite different. Computer fans are not designed to work again any static pressure. The slightest resistance will dramatically reduce the volume flow rate. You seem to have enough performance to satisfy you needs, however, to move lots of air you need a centrifugal fan design. These are specifically designed to operate in ducted systems where you experience system pressure drop. If you want high perfomance it takes high amps.
I use a Jabsco bilge blower. This moves a theoretical 118 litres per second. With four T105s is does do some useful ventilation in high ambient conditions but when you are dealing with a hot boat in the Tropics I find leaving the lid off the battery box works better and uses no amps. Overnight the batteries will cool noticeably. With the lid off the battery box there is no hydrogen build up issue either. We have temperature monitoring at the batteries via our Victron Smart solar regulator.

Yes, I realised the quoted air flow would be severely reduced. I used about 33% of that figure and still got a 300-400% excess capacity for the expected amount of gassing. I doubt I ever get anything like the hydrogen rate I used except when doing an equalisation cycle and I don't do that very often. I also open the berth cover anyway in that case and leave windows and hatches open. It makes it easier to monitor SG with everything opened up.

Leaving the lid off overnight isn't an option as I sleep directly above the battery box. Thermal transfer from the batteries to the air is fairly inefficient and I reasoned that a howling gale may not actually remove that much more heat than a much lower flow rate.

 

[geem]

Yes, I realised the quoted air flow would be severely reduced. I used about 33% of that figure and still got a 300-400% excess capacity for the expected amount of gassing. I doubt I ever get anything like the hydrogen rate I used except when doing an equalisation cycle and I don't do that very often. I also open the berth cover anyway in that case and leave windows and hatches open. It makes it easier to monitor SG with everything opened up.

Leaving the lid off overnight isn't an option as I sleep directly above the battery box. Thermal transfer from the batteries to the air is fairly inefficient and I reasoned that a howling gale may not actually remove that much more heat than a much lower flow rate.

Ah, I see your problem. Lead acid batteries dont make good pillows!
I found the opposite. My fan moves serious air but the cooling of the batteries over night with the lid off was a far more efficient cooling solution. It helps that at night the ambient can be lower in the Tropics. Trying to cool them with a fan during the day is inefficient due to the ambient air being similar to the battery temperature so with a tiny delta T you need a massive air volume flow. I mean really massive! At night the batteries have enough mass and thermal content that they naturally lose heat to their cooler surroundings assuming you can leave the lid off the battery box. I have tried this with lid on and lid off at night and have seen a 5 degC temperature difference by morning in favour of the battery box lid removed. You could run your fan at night but if you sleep on the battery box you have the noise of the fan to contend with. Fortunately we sleep in the back cabin and the batteries are under one of the saloon seats so leaving the lid off is no issue for us?

 

[affinite]

Not yet, just saw that screen shot from sailoog on their forum.
So someone else using oponplotter! Yay

Yes OP for several years now.
In fact I've just discovered Influxdb and Grafana after following your lead.
All this MQTT data (and a trashed bank of 8 batteries earlier this year) has made me paranoid about undercharging my batteries.
I'll worry about ambient battery temperature next season - oh hang on a minute ......... current ambient temperature is 30 Deg

 

[ottow]

Interesting subject, thanks for sharing!
On a related note, I see you are plotting your Alternator temps too. Where do you put the sensor on the Alternator? I am about to install one on my VP 2002 and am uncertain which part gets hottest...

 

[GHA]

Interesting subject, thanks for sharing!
On a related note, I see you are plotting your Alternator temps too. Where do you put the sensor on the Alternator? I am about to install one on my VP 2002 and am uncertain which part gets hottest...

It's just epoxied onto the the body at the back, seems to work OK. Though mirrors the engine temp pretty closely so think it doesn't generate much heat itself but usually doesn't output much as the batteries will only accept so much - might not matter with a lump of metal where you put it.

 

[sailaboutvic]

Ah, I see your problem. Lead acid batteries dont make good pillows!
I found the opposite. My fan moves serious air but the cooling of the batteries over night with the lid off was a far more efficient cooling solution. It helps that at night the ambient can be lower in the Tropics. Trying to cool them with a fan during the day is inefficient due to the ambient air being similar to the battery temperature so with a tiny delta T you need a massive air volume flow. I mean really massive! At night the batteries have enough mass and thermal content that they naturally lose heat to their cooler surroundings assuming you can leave the lid off the battery box. I have tried this with lid on and lid off at night and have seen a 5 degC temperature difference by morning in favour of the battery box lid removed. You could run your fan at night but if you sleep on the battery box you have the noise of the fan to contend with. Fortunately we sleep in the back cabin and the batteries are under one of the saloon seats so leaving the lid off is no issue for us?

@geen .
Tim I suppose you could just keep a spare bag of ice on top of the batteries , would that work?
I'm in the same situation an Mistroma we also sleep on our batteries but I figured out only having sex three times a week rather then five does keep the batteries 50% cooler .

 

[sailaboutvic]

This I do like .

Thermistor Temperature Display Data Logger - Lascar