Infinity Eco-Green 12L tankless water heater

[MarkP]

My battery bank is 48 volts. I have to have a separate 12 volt battery to run the 12 volt pump. What a pain. I wish that they made 48 volt DC pumps.

Just checked...they do. My system sort of evolved. Wish that I had done more research way back when.

[kalakoa]

a separate 12 volt battery

Use a Solar Converters # PPT 48-10 R13.6 to create a 12V supply; may or may not be cost-effective compared to 48V pumps, but the convenience of easily-available 12V parts might be worth it.

[bluesboy]

samlex makes pretty good dc-dc converters too.

[MarkP]

The price of $215 for the step-down transformer compares favorably to the price of $660 for the 48 volt pump but the 10 amp capacity is insufficient to run the current 12 volt pump, which may draw up to 30 amps.

[bluesboy]

they make converters that are rated for more amps. i would suggest one with plenty of headroom.

[kalakoa]

the 10 amp capacity is insufficient

10A is enough headroom for the small pumps, which draw around 7A.

I've actually thought about cascading a (small) 12V battery off a 48V system, using a conventional charge controller that's capable of floating on the 12V side -- it might seem excessive but there are probably cases where it's quite cost-effective, especially if the controller/battery live in the pumphouse, keeping the long wiring run on the high DC side.

[MarkP]

I keep my 12 volt marine battery topped off with a standard automotive battery charger on a timer. I would rather put that $110 cost of the battery towards a larger capacity 48 volt battery bank and forgo the separate battery. That touches upon a whole 'nuther question. I usually see my charge controller flashing by 10 or 11 am, meaning it is throttling the solar power to the batteries. If I were to add more panels right now I might reap no benefit since the charge controller would just throttle their output while if I add more batteries it is like I magically got more panels too. Since I leave my inverter on 24/7 I should go with a 120vac pump and more batteries and see where I stand.