Bike battery to supplement leisure battery (1 Viewer)

[SandraL]

The lithium bike battery is 48v 10ah.
I have connected it to a dc dc converter and adjusted output to same voltage as leisure battery, then connected it to leisure battery. This then extends our time off grid.
Our actual connection is via a 12v socket, so we can use the van ammeter to check if we are charging or discharging van battery. I have then adjusted the dc dc output so that there is no charge or discharge into leisure battery, well less than 1 amp.
I have added a small panel meter to make sure bike battery does not go too low, its a 13cell battery and I intend to switch off if it gets to 48v. My intention is to discharge the lithium battery first and then the leisure batteries if required.

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This is the cheap dc dc buck converter I used, had to look for one that could handle the 54v max my battery could provide.

Using it for first time this weekend, yesterday and today parked under trees, cloudy, so no solar input.
Only suitable for low current discharge, we have no inverter or heavy loads.
So far has worked as expected.

 

[68c]

Good idea, but seems an expensive solution. A 48v 10Ah battery gives 480WattHrs whereas a 12Volt 100Ah gives 1200WattHrs. Of course neither battery should be fully discharged but you can see a £90 leisure battery will have twice the usable power as a £180 ebike battery. I suppose if you already have the e bike battery the cost is immaterial. In your situation I would probably use the leisure battery first then use the ebike battery as backup. Your van is setup to easily charge the leisure battery, alternator, EHU or solar. Charging the 48volt ebike battery will mean an inneficient use of an inverter or a DC DC buck converter.

 

[SandraL]

Already had the bike battery, actually 2 as his n hers. Will probably user hers first!
Could suggest lithium has more discharges available than my gel 12v batteries so use first?
But basically I was playing with bits I already had, apart from the dc dc converter and should I get caught short power wise I have an answer

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