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Solar Charging and Lithiums


aandncaravan

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Saw a motorhome yesterday where the owner was concerned about the professional Lithium installation as following the install certain functionality had been 'lost'.

Not impressed by the installers, "that is normal sir as we have to bypass the main controller/charger", response so they came to us.

 

 

However, we were more concerned that the Solar regulator was charging the battery "flat out" as it has been known for a while that Lithium battery lifetime is severely degraded by constant Solar charge/EHU and the best Solar Regs keep the battery at no more than 80% max charge.

 

The Votronic MPP Solar manual states -

 

"Automatic trickle charging of the LiFePO4 battery when the vehicle is stopped to maintain a charging state of 50-80 %, which is advantageous for the battery lifetime."

 

It deliberately won't keep the battery fully charged, but at a state only between 50% and 80% charged as this reduces Solar charging damage.

 

 

I can't find much info on the Victron range of Solar Regulators to change it to follow the Votronics style of Lithium operation, can anyone help, please?

 

Lithium Battery page recently updated : http://www.aandncaravanservices.co.uk/lithium-batteries.php

 

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The internal settings need to be changed using the Victron Connect app either via the built in Bluetooth, if the model has this feature, or the add on Bluetooth module.

 

The battery itself will have a battery management system to take care of things but the solar settings can be adjusted to give best performance.

 

Victron user defined settings,

 

Absorption voltage, 14.2 to 14.6 volts, the lower value will give maximum cycle life to the battery.

Absorption time, a short time to fully utilise the battery capacity or zero time. Its suggested that a maximum of 60 minutes per 200 Ah is suitable.

Float voltage, 13.5 volts. Ideally lower than 13.6 , equivalent to a 30% charging battery voltage

Equalisation, disable.

Temperature compensation, disable.

Low temperature cut off, ( if available), between 0 and 5 degrees C

 

These are the settings used normally used in marine applications where solar is the major charging method. The numbers agree with the data sheets of the major suppliers of the lithium phosphate cells used in the available batteries.

Its suggested that long term storage, several months, should be with the batteries at around 50% charge but with the batteries in use this is less important.

Mike

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