jim-s avatar image
jim-s asked

connecting an unregulated 12V DC power source to 75/15 smart controller

I have a 12.4V / 4Amp diode protected transformer with a bridge rectifier and a 10000 MFD Capacitor @16V. I wish to connect this to the smart controller to use as a battery minder when in storage. Battery is an AGM Lifeline 105Ah. When I measure the transformer output I see an AC ripple of 900 millivolts. Can the smart charger handle this.

Thanks, Jim

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
murph avatar image
murph answered ·

I'm not 100% on this, but I don't believe you can use a MPPT charger like that. The spec sheet says that it requires Vbat+5V to start, and Vbat+1V to operate. I.e. you need a minimum unloaded input voltage of 19.6V and 15.6V under load to get a 14.6V absorption charge (and 1V lower for float).

You possibly could use one of the Orion DC-DC converters (some of them are advertised as being capable of operating as a charger). You might still struggle to make that work from a 12.4V 4A source, as that would be below the nominal rating of the smallest Orion (I think). You'd need to confirm the specific model could step up the output appropriately.

Buying one of the smaller mains chargers is probably much simpler and cheaper (than an Orion or MPPT), for a similar 4–5A output. It might even be cheaper buying a 10–20A basic charger, giving you a full 0.1–0.2C charge rate against 100Ah.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

jim-s avatar image jim-s commented ·

Murph, thanks for the reply. I misspoke in my post. My DC supply can produce 24V or greater. Could I then not use the Victron as a battery minder. It will be looking at current and doesn't know the source whether it be a transformer or PV. I have all the parts and am trying to save buying a charger for when the trailer is in storage. I do appreciate your thoughts. Jim

0 Likes 0 ·
murph avatar image murph jim-s commented ·

Yeah, 24VDC into PV input should probably work ok with a MPPT to charge 12VDC battery. I'm not sure about the 900mV ripple, however, as that's still a larger % than I'd be comfortable just shrugging off as insignificant. The MPPT controller isn't going to be designed or tested with such a rapidly changing input (and presumably won't be trying to do anything like RMS measurement to compensate).

0 Likes 0 ·

Related Resources

Additional resources still need to be added for this topic