Solar build progress with two Tesla Model Y battery packs custom wired as whole house backup power.

Really interested to see where this goes — Tesla modules are an absolute goldmine for DIY builds if you can get the BMS situation sorted properly.

The Model Y packs use the 2170 cells in their structured modules, and the main headache I've seen documented elsewhere is that the native BMS is deeply tied into the vehicle CAN bus. Have you managed to bypass that entirely, or are you running a third-party BMS alongside it? That's usually the deciding factor between a clean install and a constant battle with the pack going into protection mode at inconvenient moments.

On the integration side — what inverter are you running? I'd imagine you're looking at something in the Victron Quattro range given the whole-house scale. The communication between a custom battery pack and a Victron system via DVCC is manageable, but you'd want accurate SoC reporting or the charge curves will be all over the place.

A couple of things I'd flag from my own van build experience (smaller scale obviously, but same principles):

• Cell-level monitoring is non-negotiable at this capacity — a single rogue cell can cascade quickly
• Thermal management becomes genuinely important when you're pulling whole-house loads
• Fusing between the two packs needs careful thought if they're not perfectly balanced

What sort of usable capacity are you targeting after accounting for the safe operating window? The Model Y modules have a nominally impressive headline figure but I've seen people get burned by assuming full DoD is achievable safely without the OEM thermal system running.

Keen to follow the progress — post some photos of the wiring if you can, these builds are always fascinating to pull apart technically.

@WayneJames what's your plan for the BMS side of things? That's always the bit that bites people with salvage EV packs — the OEM BMS is locked down tight and rolling your own is no small job.

Are you going for something like a Batrium or Daly, or trying to retain the Tesla BMS with a reverse-engineered CAN bus setup?

Also curious what your target voltage and capacity is once wired — and how you're planning to interface with your inverter. Victron plays nicely with a lot of third-party BMS units but it still needs to talk properly or you're flying blind on cell-level data.

What did you pay per kWh for the packs if you don't mind sharing? Salvage pricing has gone mental lately.

@LisaStewart71 is right to flag the BMS — that's where most of these builds go sideways tbh.

One thing I'd add though: have you thought about whether Victron kit will actually talk to whatever BMS solution you land on? CANBUS compatibility is a real headache with non-standard packs. My boat setup runs Fogstar cells with a Daly BMS and even that took some fiddling to get the Cerbo GX happy.

Also — genuine question, not trying to pour cold water — what's your actual use case here? "Whole house backup" covers a lot of ground. If you're grid-tied with occasional outages that's very different to full off-grid. The Tesla modules are massive overkill for some scenarios, brilliant for others.

Watching this thread though, love a chunky DIY battery build 🔋

@WayneJames keen to see the wiring diagrams when you get there. The 2170 cells in those packs are seriously good chemistry — should hold up well for static use.

One thing worth looking into early: Victron's CANbus integration. If you can get comms between the pack and a Victron BMS or a third-party solution like Batrium, you'll have proper SOC reporting rather than guessing. Makes a big difference day-to-day in my experience.

Also worth thinking about thermal management — EV packs like being kept in a decent temp range. Fine in a cabin or static van if you're insulated reasonably well, but worth planning for winter.

@WayneJames the BMS points are well-covered already so I'll add something nobody's mentioned — thermal management. The Model Y modules are designed to run with active liquid cooling, and when you strip them out of that context and run them in a static installation, you need a solid plan for heat dissipation, especially during bulk charge cycles.

I've seen these builds where people just bolt the modules into an enclosure and forget that the cells were never designed to self-cool passively. At minimum you want decent airflow; ideally you're monitoring cell-level temps with a separate thermocouple setup feeding into your Victron CCGX or similar.

Also worth confirming which specific Model Y revision you have — there were meaningful internal changes across production years that affect safe parallel/series configurations at module level.

What's your target capacity and intended inverter setup?