f you are touring around, your starter
battery will be getting good charge during your driving. They typically have lots of extra capacity to cope with being left for a month or whatever between starts so there is a reasonable amount of spare capacity you could ultilise for the basics like phone charging for example. If your van tends to start on the turn of the key then you would be good. If the starter
battery is around due for replacement (maybe hit a certain age?) then specing up the biggest possible size that will fit could be an advantage?
You would not generally want to drop your leisure
battery below around 12.05V (around 50% SOC) as you know - Bear in mind that that voltage level on the starter
battery would still give plenty ooomph to crank the engine on a van that starts well, so being able to use some of that starter
battery energy for leisure purposes could be handy as a backup.
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Many Thanks to you Wildebus
I am very cautious re our LB and it has never been below 12.5 V and is 5 years old ! (Banner Red Bull)
In recent nights with no EHU it tends to read about 12.9 most of the evening (dark) and overnight dropping maybe to 12.6 if running a tap and then "recovering" to 12.8 or even 12.9 again
It is fully maintained (as with EB) in storage in the winter as the Aircarft Hanger" where we store the vehicle has Clear roofing and we leave the "master switch on" The original control panel has lozenges which show the state of each
battery using the rocker switch
THe EB is only 1 year old and is substantial to start a 2.5 litre diesel.
Yes we will travel mostly every other day which even without
solar provides ample power
On Stationery days such as today with
solar the voltage reads 13.8 and more.
After dusk we use minimal power..All the "toys" are on charge and complete
I have from other devices a spare heavy duty cigarette lighter plug and a suitable terminal block which feeds back to the LB
Also suitable wires (red and black) etc and a multimeter.
I assume I could simply go EB socket to LB socket ( terminal block - taking care with the polarity)
AND as you say disconnect before attempting to start the engine.
The pairing of the batteries would only occur in the evening (say 7pm to 9pm) taking care to disconnect whilst sleeping.
3 years of observation allow me to be reassured that early morning sun will top up both batteries.
Thanks very much for persisting with your replies.
I have reasonable knowledge and skill but as you put in an earlier post try to make sure I do not create a problem by trying to be too clever