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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 9th Mar 2023, 1:00 pm   #21
beamcurrent
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Default Re: Temperature sensor for lead acid batteries

On the subject of lead acid battery charging I have been contemplating making some controllers for use in MCR21 which has 4 sets of lead acid batteries of 12, 18 & 2 x 24 volts.

We would like to sill use the original crude charger as the primary source of power for historical accuracy, but to save boiling the smaller batteries (22AH in place of 100AH) make a set of controller units based on the UC3906N Integrated Circuit. This chip is quite flexible, it monitors the battery voltage and temperature.

My worry on this is the supply from the charger is rectified AC and will this rough supply upset the IC? and should I smooth it a bit? or is the response time of the IC able to deal with the 100 hz ripple?
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Old 9th Mar 2023, 1:20 pm   #22
Jon_G4MDC
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Default Re: Temperature sensor for lead acid batteries

Thanks for the picture. I will look out for something resembling it.
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Old 9th Mar 2023, 4:10 pm   #23
GMB
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Default Re: Temperature sensor for lead acid batteries

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Originally Posted by beamcurrent View Post
We would like to sill use the original crude charger as the primary source of power for historical accuracy, but to save boiling the smaller batteries (22AH in place of 100AH) make a set of controller units based on the UC3906N Integrated Circuit. This chip is quite flexible, it monitors the battery voltage and temperature.
Actually it doesn't. It monitors its own temperature and assumes that the battery is in the same place.

Quote:
My worry on this is the supply from the charger is rectified AC and will this rough supply upset the IC?
Well since it monitors the supply and trips if it doesn't like it I think you must smooth it. It has separate supply for itself so I am not sure what it would make of a rough supply to the battery.

There was another chip that also included the regulator, but I cannot remember its number.
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Old 10th Mar 2023, 11:44 am   #24
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Default Re: Temperature sensor for lead acid batteries

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Originally Posted by GMB View Post
This is what it looks like:
That's a rather neat answer to the problem! How is the little sensing element retained in the ferrule part of the tag that would normally be crimped onto a wire?
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Old 10th Mar 2023, 11:08 pm   #25
Ed_Dinning
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Default Re: Temperature sensor for lead acid batteries

Hi GMB, we used these as heatsink temp sensors on SCR traction supplies in the 70's, probably not available now but I may have the odd one

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Old 11th Mar 2023, 12:28 am   #26
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Default Re: Temperature sensor for lead acid batteries

Traction battery application is sort of like UPS application - typically a long duration between a heavy discharge, but perhaps some light loading for controls if the mains supply stops. A traction battery is typically rated for a wider temperature range, like with SLI application, with testing down to circa -18C to a specific cold-cranking amps CCA level. So the internals are customised to the application, and the max loading current levels far exceed more common VRLA type batteries, and by needs the battery cells or monoblocs can be quite large and costly.

Given the wider application ambient temperature range, the sensor and controls would need to sit the battery at a float voltage level that could be quite different at -5C to +30C, otherwise the battery either loses state of charge over time, or self-corrosion gets worse than optimum.

Any battery temperature monitoring is typically best down at the metallic terminal location, as that has the lowest temperature gradient to the internal parts/processes needing to be sensed.

Some large traction batteries benefit from boost charging, especially wet cells where acid density stratification over time can occur and where boost charging causes internal liquid mixing.

Intermittent charging is a more advanced form of charging that is especially suited to UPS application, but I haven't seen applied to traction, whereby the battery is removed from float charge for a significant portion of time such that internal corrosion rate is lowered and hence service life is extended. But of course advanced charging infrastructure is the opposite intent of many cheaper forgotten about battery systems.
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Old 15th Mar 2023, 11:07 am   #27
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Default Re: Temperature sensor for lead acid batteries

Quote:
How is the little sensing element retained in the ferrule part of the tag that would normally be crimped onto a wire?
It is stuck with black epoxy.
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