SOC_Nerd | 2,341 posts | 🔋 Off-Grid Grump
The efficiency "looking dodgy" is the tell. Most of these units overstate their own tracking performance and you'd never know without...
@VanLee what battery are you actually running? Makes a massive difference here. LiFePO4 and lead-acid want completely different charge profiles and Victron's defaults aren't always right out of...
Yeah, this catches a lot of people out and it drives me absolutely mental seeing the same confusion repeated every few months on here.
The standing charge is the killer nobody talks about.
@DODGuy is on the right track but I'd add — check your cable gauge and connection resistance too, not just battery voltage. I had this exact nonsense with my Phoenix 375 last winter.
@SueThompson depends heavily on what "overnight" means to you and how efficient that freezer actually is.
@OffGridJack 2 hours is conservative but not wrong. The thing people miss is that absorption time is basically irrelevant if you've got your tail current set properly.
@StormyDrifter yeah the BT polling is a nightmare — discovered that the hard way when my Prometheus scrape interval kept clashing with the Victron app's own BT connection and one of them would...
@Thommo already covered the obvious bit so I won't rehash it.
Worth checking whether your cells were properly top-balanced before assembly.
@LakelandNomad's DVCC limiter theory tracks with what I've seen on my own setup. The bit nobody's mentioned yet: check whether your MPPT is actually receiving the updated CCL from the BMS after...
@AlexHobbs the VA rating mismatch is the obvious concern — you're asking a 6 kVA UPS to drive an 8 kVA transformer core before you've put a single load on it.
@FrostySocket is right and people consistently underestimate floor heat loss — it's not glamorous insulation work so it gets skimped on.
One thing nobody's mentioned: vapour barrier placement...
@Bazza60 is right on the fusing — but the bit everyone glosses over is fuse placement. It needs to be within 300mm of the battery terminal, not just "somewhere on the positive cable."...
@DucatoSolar the 100/30 is a 12/24V controller — your Voc absolutely cannot exceed 100V. Four 175W panels in series will likely blow straight past that depending on your panel specs.
@Tommo10 yeah, LiFePO4 gets grumpy below about 5°C — charge acceptance drops off a cliff and the JK will protect itself by disconnecting.
@RustyTinker 200Ah sounds like loads until you're sat in the Cairngorms in January. The Webasto fuel pump ticks along fine but your parasitic loads are quietly murdering you — fridge still...
