Dc-Dc charger

DIY
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1

Ciao a tutti, I need some information if possible.
The situation is as follows:
. 30” sailing boat
. 55A alternator with normal internal regulator
. Lead acid 70Ah starter battery
. Lead acid 110x2 Ah house batteries

The questions are as follows :

  1. Is it possible to use a dc-dc charger without modifying the alternator or the regulator or the batteries to charge the house batteries via the starter battery?
    2)If so, which one?
    3)If so, the house batteries would be charged with the 3-stage charge algorithm: bulk-absorption-float ? while the starter battery would be charged with the alternator’s internal regulator (fixed voltage) ?
  2. if a dc-dc charger is not suitable, what else?
2

You could use a DC to DC charger, you need to be careful to not overload a 55A alternator. You could use an Orion XS 50A rated unit, that may be too high a load but it can have the current limited to say 30A.

https://www.victronenergy.com/dc-dc-converters/orion-xs-12-12-50a-dc-dc-battery-charger

You could use an Orion 12/12 DC to DC charger and choose a 20A or 30A version to avoid over loading the alternator. The output on these can not be adjusted, you can however change the charge voltage to refice the charge current.

3

Thanks for the info pwfarnell.

With the dc-dc charger, you confirm to me that the house battery will be charged witht the 3-stage charge algorithm, while the starter battery will be charged with the alternator internal regulator (fixed voltage)?

Thanks

4

Yes it will be a 3 stage algorithm…

You need to be careful when you but it. Victron sell a range of converters with fixed voltage and a range of chargers with 3 stage algorithm. Make sure you buy the correct one.

5

Ok, thanks again.