question

daves avatar image

Camper van split charge relay clicking

Hi. I have a VW T5 with a 12v leisure battery connected to vehicle battery via a 140A Sensitive Relay (Portable Power Technology).

I have fitted a 150W solar panel and SmartSolar controller MPPT 75/15 to the leisure battery. My problem is that the split charge relay constantly clicks and only stops when I use power from the leisure battery (turn lights or fridge on).

Is this a problem with the controller settings or the relay?

Relaycharge controller compatibility
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1 Answer
Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@Dave.s, it sounds like the relay is probably trying to close (thus combining your start and leisure batteries) while the MPPT is charging your leisure battery. This would typically be due to the relay's voltage trigger being reached - thus why it stops when you apply a load to the leisure battery.

Your relay is likely bidirectional and designed to close when either battery reaches a certain voltage threshold, thus passing charge current through to the other battery, but the fact that it's not closing and staying closed, but rather "fluttering", does seem indicative of an issue with it... I recommend that you contact your relay's manufacturer or user manual to find out how exactly it's supposed to operate.

The Victron Cyrix-ct VSR is bidirectional as well, but it is microprocessor-controlled and uses an open/close timer to prevent the type of "fluttering" behavior that you're seeing from your relay. It may be time for an upgrade to your existing VSR :)

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Thanks Justin, I’ve got another VSR so will try that tomorrow.