Alternator charging killing my leisure batteries — worth fitting a B2B charger on the boat?

by Neil Jackson · 4 days ago 48 views 0 replies
Neil Jackson
Neil Jackson
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Joined Oct 2024
4 days ago
#8129

Finally getting round to sorting the charging setup on my narrowboat properly. At the moment the alternator just dumps straight into the leisure bank (3x 110Ah AGMs wired in parallel) via a basic split charge relay. It charges them, technically, but I know it's not doing them any favours — bulk charge cuts off way too early and absorption never really happens properly.

Been looking at the Victron Orion-Tr Smart 12/12-30A isolated DC-DC charger as the obvious fix. The isolation is the main draw given I've got two separate battery banks and don't want any funny earth loop issues on the canal. Seen a few people fit the 18A version but for a 3x110Ah bank the 30A seems more sensible. Anyone actually running one of these on a narrowboat day-to-day?

The alternator itself is a 70A Lucas-style unit — nothing exotic. Engine is a Beta 38. Wondering whether the B2B will play nicely with it long-term or whether I need to worry about overloading the alternator on longer cruising days. On a full day's cruise I'm probably doing 6-7 hours, so in theory there's plenty of time to get a decent charge in.

Has anyone also combined a B2B with solar on a boat? I've got two 175W panels on the roof feeding a Victron MPPT 100/30 and I'm trying to work out whether the two chargers talk to each other sensibly or just fight over the battery.

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