Victron IP65 Blue Smart charger settings for battery backup

Running a similar setup in my shepherd's hut actually — Victron IP65 12/25 keeping a 100Ah LiFePO4 topped up as emergency backup for my water pump. Took me ages to dial the settings in properly.

The key thing I'd flag for anyone doing this is don't just leave it on the default AGM/GEL profile. You need to manually set it to Li-Ion mode via the VictronConnect app, otherwise it'll push absorption voltage too high and your BMS will be tripping constantly. Learned that the hard way.

For a permanent float/storage situation with LiFePO4, I've settled on:

• Absorption: 14.2V
• Float: 13.5V (some people drop this lower, 13.2V even)
• Storage mode: enabled — this is the one most people miss

Storage mode is brilliant for backup batteries that just sit there most of the time. It'll drop to a lower voltage to reduce stress, then occasionally top back up. Exactly what you want if the battery isn't cycling daily.

One thing I'm still not 100% sure on — does anyone know whether the IP65 25A model handles the transition back from storage voltage to float cleanly, or does it do a full absorption cycle every time it tops up? My Fogstar 100Ah seems happy enough but I'd love to know what's actually happening under the hood.

Anyone else running the IP65 as a standby/backup charger long-term? Curious whether others have tweaked settings differently for low-cycle use cases.

@JA_Solar the IP65 is a beast for that kind of duty but make sure you've got the absorption voltage set to 14.2V not the default flooded setting or you'll be cooking your cells slowly like I nearly did with my Fogstar 200Ah in the static van 🔥

Also worth enabling the "Li-Ion" preset as a starting point then tweaking — saves you half the headache of doing it manually from scratch.

@BorderVanLifer is spot on about that absorption voltage — 14.2V is the sweet spot for most LiFePO4 cells. I'd also add that for a backup/standby application like this, you really want to look at your float voltage too. Drop it down to around 13.5V rather than leaving it at the default. Keeping LiFePO4 sat at full charge indefinitely does them no favours long-term.

Also worth checking whether your BMS has a charge enable signal you can feed back to the charger — the IP65 has an option for that on some firmware versions which lets the battery manage the whole process rather than relying purely on voltage thresholds.

What BMS are you running with it @JA_Solar? Makes a difference to how aggressive you can be with the settings.

Float at 13.5V or your cells will be cooking on a slow hob for eternity — my Fogstar 100Ah on the narrowboat took six months of abuse before I figured that one out. 🔥

Also worth disabling the equalisation cycle entirely in the Victron app, because LiFePO4 and equalisation go together like a canal boat and a motorway.

@WonkyHermit raises a fair point on float, though I'd actually push back slightly — on a pure backup battery that sits idle most of the time, I've had better long-term results dropping float to 13.2V rather than 13.5V. Less parasitic stress on the cells between charge cycles.

Worth noting for @JA_Solar specifically: the IP65 12/25 has a storage mode option which cuts in around 13.0V after a period of inactivity. For a shepherd's hut backup application where the battery might sit untouched for weeks, that's arguably more relevant than fine-tuning absorption and float.

I run a similar setup in my cabin — Victron IP65 paired with a Fogstar Drift 100Ah — and enabling storage mode was the single biggest improvement to my battery's long-term state of health.

@CaddyCamper has a decent point there — if it's basically just sitting doing nothing 99% of the time, you really don't want float voltage doing unnecessary work on those cells.

Worth flagging: the IP65 12/25 has a storage mode option that kicks in after a set period. That's basically what you want for a backup scenario — it'll drop down to around 13.2V which is much kinder long-term.

I've got my garden office setup doing something similar. Runs my inverter occasionally but mostly just sits there looking smug. Storage mode has been brilliant for keeping cycle count low.

Check under the charger profile settings in the VictronConnect app — dead easy to tweak once you're in there. Took me about 4 minutes and a cup of tea to sort.