Following on from the thread about second use for old electric car batteries: surely as end of life is reached for any cell the self discharge increases and thus a higher proportion of the charge gets expressed as heat?
I need to provide hot washing water in one of our vans, about 10 litres is enough and these basin units are readily available for £250.
I can see a split charge system will only charge the second battery when the main vehicle battery exceeds 13.5V, and even a facility I'm told that will only charge it on overrun. This will get the water hot on the run to work.
During the day how does one prevent the auxiliary battery discharging below 50% DOD, is it by voltage sensing or do VA have to be integrated?
AJH