Lead-Acid temperature compensation in charging

[flippineck]

I have this new charge controller for my solar power system.

One of it's features is 'temperature compensation' and it has something to do with changing how the battery is charged depending on it's temperature.

The 'temperature compensation' feature is adjustable in programming and is measured in millivolts per cell per degree C (I think). You can set the value to zero which, according to the manual, means 'temperature compensation feature inactive'.

There is no external port for a temperature probe, and reviews of the unit online seem to confirm, the temperature sensor is a fixed component located permanently within the unit. The idea seems to be, that the controller is mounted in the same enclosure as the batteries.

Well for safetys sake I fitted my battery bank outside the house in a dedicated enclosure, but the controller is fitted inside in the understairs cupboard.

How important is the temperature compensation?

I have 2 options.. leave the function disabled, or fit the controller outside in the battery enclosure.

I'd rather not open the unit to try and create an external probe port, it's tempting but I'd rather preserve the guarantee.

If the compensation feature doesn't really give massive improvements in charging or battery life, I'm tempted to just leave it set to 'off'. What do you guys think?

 

[Arouse1973]

Temp compensation is important if you are charging it at high or low temp. The other thing that makes a difference is how much current you are using to charge the battery as this inreases the batery temp, also if its wet or gell type makes a difference.

Aceptance charge for gell type and wet type differ as does float charge. At room temp say 25 deg C a wet cells float charge is about 13.5 Volts and a gell cell is about 13.8 Volts.

Both aceptance charge is about 14.4 Volts for both but this reduces with increase in temp. So unless your charging with a lot of current or at elevated or reduced temperatures then you could switch it off. But if it a setting as part of the charger then it makes sense to switch it on, I would.
Adam

Edit: The above voltages are for a 12 Volt battery.

 

[gorgon]

Depending on the local ambient temperature it may be very important to have the temperature compensation installed correctly.
When the ambient temperture is increasing, the nominal charge voltage is decreasing. Geting an over voltage charge over time, will increase the internal temperature ov the battery, start gas production, and in worst case ruin it permanently.
When the ambient tempareture is colder than 25C the nominal charge voltage is increasing, and you need to charge at a higher voltage to top your battery all the time, or you'll loose capacity when running on battery.

if you have your battery out in the cold in the winter, you will have a lower capacity on the battery anyway, and a too low charge voltage will not make the problem better.

 

[flippineck]

Thanks chaps. According to met office data the average temperature round here swings between 0 deg C & 20 deg C, with winter low extremes down to -19 deg & summer high extremes up to 32 deg.

 

[signalman72]

Find out what the optimal float charge is for your batteries. Check them periodically with temp swings and adjust float voltage to compensate.