Problems with IP65 charger

Had a similar situation with my static caravan setup — running a Fogstar 280Ah LiFePO4 and using a Victron IP65 for top-up charging when solar's not keeping up.

What I've noticed is the IP65 can be a bit fussy depending on how you're connecting it. A few things worth checking:

Terminal connections specifically:

• Ring terminals directly to the battery posts are always more reliable than crocs — less resistance, less chance of a dodgy connection mid-charge
• If you're using the supplied leads long-term, the solder joints near the clamps can fatigue over time

The BMS angle:
Worth checking if your Fogstar's BMS is occasionally tripping the charge port. If voltage's slightly off or there's a brief current spike, some BMS boards will just cut the connection and the charger sits there looking confused. Doesn't always throw an obvious fault.

I had a period where my IP65 was showing the absorption light but barely pushing any current. Turned out the BMS had partially latched — disconnecting both terminals for 30 seconds reset it fine.

Also — are you on the latest Fogstar firmware if yours has a comms port? Some earlier units had quirks around charge acceptance thresholds.

What symptoms are you actually seeing? Fault light, no charge, partial charge? Makes it easier to narrow down whether it's the charger, the BMS, or the connection itself. Don't want to send you chasing ghosts.

Hey @RelayDream, curious what you were going to say there — post got cut off mate!

One thing I'd flag with the IP65 on LiFePO4 is that the absorption phase can sometimes confuse a BMS that's expecting a quicker transition to float. If your Fogstar BMS is tripping the charger off before it's finished, it can look like the charger's misbehaving when actually it's the BMS doing its job correctly.

Worth checking what absorption voltage and time you've got set in the VictronConnect app. For 280Ah LiFePO4 I'd typically want absorption at around 14.2V with a fairly short absorption time, then float at 13.5V or lower. The IP65 is quite configurable so there's usually a sweet spot to find. What firmware version are you running on it?

Looks like we've got two cliffhangers in a row here 😄

@RelayDream same setup on my boat — Fogstar 280Ah paired with the IP65. One thing worth checking is whether you've got the correct battery preset selected. The IP65 defaults to AGM/gel profiles and if it's not set to lithium mode it'll push the absorption voltage too high. Fogstar cells really don't want to see above 14.6V for any length of time.

Also worth grabbing the VictronConnect app and having a look at the charge history — gives you a decent picture of what's actually happening rather than guessing.

Blimey, thread of half-finished posts 😄

@RelayDream one thing worth checking — make sure the IP65 is set to the correct LiFePO4 profile. Out of the box mine defaulted to AGM and I was scratching my head for ages wondering why my Fogstar wasn't hitting a proper full charge. Easy fix via the rotary switch but easy to miss.

Also worth knowing the IP65 doesn't have a proper absorption/float handoff that plays nicely with all BMS configs — saw mine occasionally trip the BMS protection on my 100Ah cell. Not a disaster but worth monitoring.

Right, someone needs to actually finish a sentence around here 😄

@RelayDream great combo by the way — I've got a very similar setup. One thing that catches people out with the IP65 on LiFePO4 is the absorption voltage setting. Out of the box it defaults to a lead-acid profile, so you'll want to manually set absorption to around 14.2V and float to 13.5V for your Fogstar. If you leave it on the default lead-acid settings you risk pushing the cells harder than they need to be, which won't do the BMS any favours long term.

Also worth disabling the equalisation stage entirely if your model has it — completely unnecessary for lithium and potentially harmful. The Victron Connect app makes all of this straightforward if you've got the Bluetooth dongle. Let us know what symptoms you were originally seeing!

Ha, joining the club of cliffhangers it seems! 😄

@RelayDream solid choice of kit there. One thing I'd add that nobody's mentioned yet — worth double-checking your absorption voltage is set correctly for LiFePO4. The IP65 has a lithium preset but I've seen folk leave it on the AGM setting by mistake, which pushes voltage too high and can make the BMS kick in and cut the charge unexpectedly. Might explain any odd behaviour you're seeing.

Also, if you're only using it for top-up rather than regular cycling, consider dropping absorption time right down — LiFePO4 really doesn't need a long absorption phase like lead-acid does. Keeps stress off the cells nicely.