Victron BP to JVR digital timer wiring trouble

Been scratching my head over something similar and wondered if anyone here has cracked it.

I'm running a Victron BP-65 protecting a 100Ah LiFePO4 (Fogstar Drift) and I want to bring a JVR digital timer into the circuit to control a 12V water pump on a schedule. Should be straightforward, right?

The issue I keep hitting is around where exactly the timer sits in the circuit. If I wire it downstream of the BP, does the BP's load disconnect behaviour cause the timer to lose its programmed settings when the BMS cuts power? Or does the JVR retain memory without a continuous supply?

A few specific questions if anyone's tackled this:

• Should the timer's live supply come directly from the battery (pre-BP) with only the pump circuit running through the BP?
• Is there a risk of the BP seeing the timer's quiescent draw as a problematic load?
• Has anyone used a small supercapacitor or backup cell to keep the timer's memory alive during a disconnect event?

I've had a look through the Victron BP documentation and it doesn't really address ancillary control devices, just the main load side. The JVR manual is fairly thin on off-grid scenarios too.

Feels like there should be a neat solution here — possibly something to do with splitting the supply rails — but I don't want to bodge it and end up with the pump running at 3am because the timer reset itself! 😅

Anyone done this kind of setup, or know of a better 12V programmable timer that handles intermittent supply more gracefully?

@Cleggy the OP seems to have got cut off mid-sentence — could you finish describing what you're trying to do with the JVR timer? Specifically:

• Are you using it for load-side switching or trying to control the BP-65's remote on/off?
• What's your battery voltage — 12V or 24V system?

I've got a BP-65 on my cabin setup protecting a Fogstar Drift as well, so genuinely curious how you're intending to integrate it. I've seen a few people use digital timers on the load side of a BP but the wiring order matters quite a bit to avoid backfeed confusing the BP's voltage sensing.

If you can post a rough diagram or describe the circuit path you're envisaging, I reckon someone here will be able to spot where it's going wrong.

@Cleggy yeah your post got chopped, finish the thought before anyone can properly help.

That said, I've got a BP-65 on my van setup protecting a Fogstar 100Ah and I've dabbled with timers on the load side, so I can probably guess where you're heading.

The thing that catches most people out — the BP's load output isn't a switched live in the traditional sense. If you're trying to use a JVR timer to control the BP remotely, you're wiring into the remote H/L pins, not splicing into the load terminals directly. Done it wrong myself once. Melted a connector. Wasn't a great afternoon.

Finish describing your actual goal and I'll tell you what worked for me. Diagrams help if you can manage one.

Yeah @Cleggy looks like your post got mangled, hopefully you can edit it and fill in the blanks!

That said, I've had a JVR digital timer running alongside a BP-65 on my van build for about eight months now. One thing that catches people out is that the BP-65's load output isn't meant to power the timer directly — you want the timer on a separate fused feed from the battery, otherwise you get all sorts of weird behaviour when the BP trips. The timer's output switching side then controls whatever load you're protecting.

Happy to sketch out the wiring logic once we know what you're actually trying to switch. Is it a fridge, a pump, something like that? Makes a difference to how you set it up practically.

@Cleggy looks like the post got cut off before you explained what you're actually trying to do with the JVR timer — worth editing that before this goes too far down the wrong track.

That said, I've got a BP-65 on my static caravan setup and I'm curious about this myself. A few questions that might matter once you clarify:

• Are you putting the timer on the load side of the BP, or upstream?
• What's the timer actually switching — a 12V load direct, or triggering something else?
• Is the Fogstar Drift running its own BMS independently of the BP-65?

The reason I ask is I had a weird issue where my BP-65 would trip unexpectedly and it turned out to be inductive kick from a relay. Might be unrelated but could matter depending on what the JVR is driving.

@Cleggy the post definitely got trimmed — hopefully you can edit it and fill us in on what you're actually trying to achieve with the JVR timer, because the wiring approach changes quite a bit depending on whether you're using it for load control, scheduled charging, or something else entirely.

That said, I've done a fair bit of fiddling with the BP-65 on my cabin setup, and one thing that catches people out is that the BP's remote on/off behaviour doesn't always play nicely with timer modules expecting a clean switched live. Worth knowing before you dive in.

Once you've shared the full picture, I can walk through exactly how I've got mine arranged — saved me a lot of head-scratching once I understood what the BP actually wants to see on those terminals.