DC power from house + battery - is this approach sensible?

[gwynm (Gwyn Morfey)]

I’d like to run a diesel heater (12V @ 15A peak, 3A continuous) and some lighting (12V @ 10A) in a garden outbuilding. It’s too shady for solar, but I can run a low-voltage, low-current line from the house. That can handle the continuous load OK, but not the heater startup if the lights are on, so my plan is to add a battery buffer.

Does this setup look sane?

Possible causes for concern:

• If the smart charger tries to draw more than 10A from the house, the 24V transformer will brown out. Can I configure it for a lower maximum draw? (or, is it smart enough to limit itself to whatever current doesn’t cause voltage drop?)

• If I have this right, then when the smart charger is in absorption mode, the battery (and therefore the heater, lights, etc) will actually be receiving ~14V rather than 12V. I can’t think of an easy way to design around this… but do I even need to?

All advice very welcome!

[pwfarnell]

The Orion output can not be limited but it does have input low voltage shut down. 30A is also too large for a 100Ah battery.

Consider the Orion-Tr Smart DC-DC charger isolated 24/12 20A version which would not draw too much from your 10A 24V supply.

If you have the system permanently powered as a buffer rather than a cycling battery then you can set the Orion to have a much lower absorption voltage, set both float and absorption at 13.2V to 13.6V.

[gwynm (Gwyn Morfey)]

Thanks! I’ll look into getting a bigger battery and/or a smaller charger.

[pwfarnell]

Which is exactly what is shown in the schematic in the original question.