My camper is stored during wintertime in an unheated glasshouse.
230V is supplied during 1,5hrs/day.
Once the temperature of the LFP sinks below 5C it stops charging.
The CERBO GX and GSM ROUTER (20 Watt) slowly drain the LFP.
I installed the system as shown in diagram attached.
4 Silicone heating pads 12VDC/12W each are attached to the long sides of the LFP (2/side). On each side 2 pads are glued onto an aluminium plate 150x250x2 mm. The aluminium plates are attached to the side of the LFP using 3M VHB Tape 1941P (alu plates covered entirely with tape) The LFP including heating pads are insulated on the sidewalls and the top by approx 25 mm insulating material..
The temperature control is done by the CERBO GX. The power to the pads is supplied through a relay which is controlled bij Relais 2 of the CERBO GX.
The main powersupply is branched from the 12VDC supply to the LPG fired Truma Combi 6 heatingsystem.
A VE “Temperaturesensor Quattro, MultiPlus and GX-devices” is attached to the + connection of the LFP, the wires to a temperature INPUT of the CERBO GX.
The setting is: Start at 7C, Stop at 8C. There is an overshoot of approx 1C.
The core temperature of the LFP differs aprox. 1C from the temperature measured by the sensor.
See graphs.
The purpose was to keep a negative impact of heat to the LFP as low as possible and to have a control system which is integrated in de VE system in the camper. Until now there is only experience during low outside temperatures. Interesting to see if there is any effect of the insulation to the LFP core temperature in the summer. The current temperatures in the camper and outside vary between -5C to +5C.
The graph display the measured temperature by the sensor (degr. C)
The Y axis is in Watts. There is a baseload (CERBO GX and GSM ROUTER) of 20W.
Allthough specified at 4 x 12W = 48W the pads take 60 W.
Based on the total surface of the aluminium plates (7,5 dm2) the heat input is 8W/dm2 (75W/ft2)