battery charger with more than one temperature sensor

simonfraser said:
following on from another forumite with his hot battery

my Sterling Pro Digital battery charger has one temp sensor, but i have four batteries

can i just buy three more sensors and wire them all up in parallel to the charger, or ?
Click to expand...

ITYWF that the temperature sensor should be connected to the negative terminal of which ever battery you think will be in the warmest location.


I guess the temperature sensors are negative temperature coefficient thermistors. If you put 4 in parallel the charger will see only a 1/4 of the resistance of one and think the batteries are very much warmer than they in fact are, 40C or 50C instead of 20 C maybe, dispaly a high battery temperature warning and reduce the charging voltage accordingly or even shut down
 
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simonfraser said:
following on from another forumite with his hot battery

my Sterling Pro Digital battery charger has one temp sensor, but i have four batteries

can i just buy three more sensors and wire them all up in parallel to the charger, or ?
Click to expand...

The temperature sensor is most likely a simple thermistor. Connecting more of them in a single plug will provide a grossly false reading. Won't work. Your best solution is to have all batteries of the same kind and age and measure the temperature on one randomly selected. There is, of course, no guarantee they will be ageing at the same rate... If you batteries are not exactly the same, it will be hard to achieve perfect results with one charger. The only viable solution I can see is having 4 sensors fitted and alternating the outputs to the charger in a few minutes intervals. Complicated as it seems, it may be actually achieved by some quite simple circuitry. Be aware the charger will respond to the highest reading an may leave the colder batteries undercharged.
 
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jiris said:
The temperature sensor is most likely a simple thermistor. Connecting more of them in a single plug will provide a grossly false reading. Won't work. Your best solution is to have all batteries of the same kind and age and measure the temperature on one randomly selected. There is, of course, no guarantee they will be ageing at the same rate... If you batteries are not exactly the same, it will be hard to achieve perfect results with one charger. The only viable solution I can see is having 4 sensors fitted and alternating the outputs to the charger in a few minutes intervals. Complicated as it seems, it may be actually achieved by some quite simple circuitry. Be aware the charger will respond to the highest reading an may leave the colder batteries undercharged.
Click to expand...

simple ciruitry, i am a simple man, explain further pls :)
 
What you need is something like this: https://au.element14.com/cebek/i-5/...la-295294719026|&CMP=KNC-GOO-SHOPPING-2817052 . This particular one is almost taylored to your application - not necessarily the simplest or cheapest, it was just the first one I found meeting my technical criteria. I am sure if you search some of the Chinks sites like Alibaba for "sequential circuit", you will get something for a fraction of price of this one.
 
jiris said:
What you need is something like this: https://au.element14.com/cebek/i-5/...la-295294719026|&CMP=KNC-GOO-SHOPPING-2817052 . This particular one is almost taylored to your application - not necessarily the simplest or cheapest, it was just the first one I found meeting my technical criteria. I am sure if you search some of the Chinks sites like Alibaba for "sequential circuit", you will get something for a fraction of price of this one.
Click to expand...

Hm, neat.

But, that will just show peak temp to the charger as the board cycles.
Might calm the charger down in case of a raised temp.

Neater solution would be ?
Adreno board that checks 4 temp sensors and outputs the highest temp to the charger 24/7
Guess that’s buildable....
 
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Absolutely! It could cause the charger to have a wobbly and not behave as designed which could have some strange effects are we don't actually know how the charger would be affected from a software point of view if the values kept scrolling.

The Mastervolt chargers I fit have a single temperature sender per charger, the idea being, all batteries are together so you stick it on say 1 in the middle and get on with life.

If the batteries are in separate boxes, then consider a 2nd charger if it is a problem worth worrying about.

simonfraser said:
Hm, neat.

But, that will just show peak temp to the charger as the board cycles.
Might calm the charger down in case of a raised temp.
Click to expand...
 
simonfraser said:
Neater solution would be ?
Adreno board that checks 4 temp sensors and outputs the highest temp to the charger 24/7
Guess that’s buildable....
Click to expand...

ESP8266 with 4 x DS18B20 temperature sensors would do it, maybe initially just have the esp make a little webpage then you might see that the problem doesn't really exist. Might as well add an ASD1115 4 channel voltage sensor while you're at it :cool:
 
The OP has not mentioned that he wants to monitor battery temps for all batteries in case of a shorted cell in one battery, causing it to get rather hot, in the hope that the charger would reduce output enough to stop the battery over heating.
 
PaulRainbow said:
The OP has not mentioned that he wants to monitor battery temps for all batteries in case of a shorted cell in one battery, causing it to get rather hot, in the hope that the charger would reduce output enough to stop the battery over heating.
Click to expand...

If that's what you want to do, then a separate temperature alarm for each battery, ORed together so that any alarm stops the charger mght be the way forwards?
 
lw395 said:
If that's what you want to do, then a separate temperature alarm for each battery, ORed together so that any alarm stops the charger mght be the way forwards?
Click to expand...

Not what i want to do, what the OP wants to do. Much of the thread also assumes that someone will be onboard. The OP is also working on the assumption that the battery charger will reduce the charging enough to stop the battery over heating, i'm not sure if it would, or not.

For the purposes of a failed battery overheating i'd have thought a monitor that could turn the charger off completely would be the better answer. If designing something using an Aruino or similar i'd guess some logic to trigger a normally closed latching relay would work.
 
lw395 said:
If that's what you want to do, then a separate temperature alarm for each battery, ORed together so that any alarm stops the charger mght be the way forwards?
Click to expand...

hm, indeed that would be simpler :)

plenty of low cost 12V temperature sensors with a relay and display on ebay, did not know they existed
can just wire some up and cut the charger off it it gets too hot, possibly not perfect, but stops it boiling off / catching fire
 
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