Blue Smart IP22 and Blue Solar MPPT working together

Running a similar combo in my shepherd's hut actually — Victron Blue Smart IP22 alongside a BlueSolar MPPT 100/20 feeding a pair of Fogstar 100Ah lithium cells.

The bit that caught me out initially was priority. When shore power's available the IP22 obviously wants to do its thing, but the MPPT doesn't just sit quietly — both were pushing into the bank simultaneously and I wasn't 100% sure that was fine or if I was missing something obvious.

Turned out it's totally normal, Victron designed them to play nice together. The MPPT just sees the battery voltage rising and backs off naturally. No VE.Smart networking or anything fancy needed, though I did eventually add that via a dongle and it made a noticeable difference to charge accuracy.

Few things worth thinking about if you're on lead acid rather than lithium:

• Absorption voltage coordination matters more with LA
• Both chargers will run independent absorption cycles which can mean longer time at higher voltage
• VE.Smart network ties them together properly if you want tighter control

Anyone done this with the smaller 75/15 specifically? Curious whether the lower current rating causes any weirdness when the IP22 is also on. My setup's slightly beefier so not sure my experience maps directly.

Also — are you running any monitoring? VictronConnect through Bluetooth is fine for checking each unit separately but I'd love a proper unified view without dropping £££ on a Cerbo GX.

@DalesCruiser — almost identical setup to mine in the shepherd's hut, so I've been through exactly this.

The key thing that caught me out was that without a shared battery sense wire between the two units, they're both guessing at battery voltage independently. The IP22 was reading slightly higher due to cable voltage drop, so it was terminating absorption early.

Run a dedicated sense wire to the battery terminals on both units if you can. Alternatively, if you've got a Victron BMV-712 or SmartShunt in the system, you can use VE.Smart Networking — both the IP22 and the BlueSolar MPPT 100/20 (assuming it's the Bluetooth-equipped variant) will then share a single accurate voltage and temperature reading across the whole charge chain.

Made a noticeable difference to how properly my Fogstars actually top off.

@DalesCruiser the thing nobody tells you until you've already cooked a battery is that the IP22 and the MPPT will both try to be the boss — stick a BatteryProtect or at least sort your charge priority via VictronConnect or they'll argue like two sat-navs giving different directions simultaneously 🗺️

@DalesCruiser both sources need to see each other or you'll end up with the MPPT doing all the heavy lifting while the IP22 sits there thinking it's already finished — learned this the hard way on my narrowboat when my Fogstar pack hit 14.6v from solar and the mains charger just shrugged and declared victory at 40% actual SoC.

Good thread — this is almost exactly what I'm looking at for my garden office build.

Quick question though: does the shared battery voltage actually give enough feedback for both units to back off gracefully, or do you still end up needing a proper BMS communication link between them?

I've got a Fogstar Drift 100Ah on order and the spec sheet mentions a comms port, but I'm not sure the BlueSolar MPPT 100/20 I'm eyeing up supports anything beyond basic voltage-based absorption cutoff.

@HannahDavies85 — when you say they need to "see each other," are you talking about VE.Smart Networking via Bluetooth, or something more involved? Wondering if a VE.Bus Smart Dongle sorts this or whether that's only relevant when a Multiplus is in the mix.