Parallel EasySolar setup with battery issues

Running a parallel EasySolar setup on my narrowboat (well, dreaming of scaling up from my single unit anyway) so this caught my eye.

Anyone else had grief with battery comms when running two EasySolar 48/5000 units in parallel? From what I understand, the VE.Bus parallel config needs both units seeing identical battery state — if your BMS or battery monitor is only talking to the master unit, the slave can end up making dodgy charging decisions.

A few things worth checking:

• VE.Bus cabling — even a slightly loose RJ45 between the two units causes weird behaviour
• DVCC enabled in Venus OS — this is the biggie for parallel setups, lets the GX device take control of charging rather than each unit acting independently
• Battery temp sensor — gel banks especially need this nailed down, they're fussy about charge voltage at different temps

With gel batteries specifically, I'd want to double-check the charge profile is spot on. Victron's defaults aren't always right out of the box for every gel chemistry — worth cross-referencing your battery manufacturer's specs and tweaking in VictronConnect.

Also, 36 kWh of gel is a hefty bank. What's the C-rate looking like from the inverters? Two 5000s pushing hard into gel can sometimes trigger protection issues if the bank's internal resistance is higher than expected.

What monitoring have you got on it — CCGX, Cerbo? Would help narrow things down.

Keen to hear what others have found with parallel EasySolar installs — feels like there's a lot of nuance that installers sometimes gloss over. 🔧

@BreezyDrifter the comms issue is almost certainly the VE.Bus configuration rather than the batteries themselves. When you parallel two EasySolars you must use the VE.Bus cable to daisy-chain them, and only one unit acts as master — the other slaves off it. If your BMS is talking to both units independently via VE.Can or whatever, you'll get conflicting charge commands.

Victron's own documentation on this is frustratingly vague, but the key setting is "ESS assistant" on the master unit only. Slave gets nothing.

Had a similar headache when I was scoping out a parallel setup for my shepherd's hut — ended up going single larger MultiPlus-II rather than paralleled EasySolars partly because of this complexity.

What BMS are you running? If it's a Fogstar or similar UART-based unit, that changes the diagnostic approach entirely.

@SomersetVanLifer makes a fair point about VE.Bus, but I'd add one thing that catches people out specifically with EasySolar units in parallel: the battery temperature sensor assignment.

In a parallel setup, only the master unit should have the temp sensor active in VEConfigure — if both units are reading temperature independently you can get conflicting charge parameters being applied, which manifests as erratic absorption behaviour that looks like a comms fault.

On my narrowboat I'm running a single EasySolar 24/3000 with Fogstar Drift 200Ah cells, and even in a single-unit setup the VE.Smart Networking config needs to be deliberate about which device is "broadcasting" battery data.

Worth downloading VEConfigure3 and checking the "Battery monitor" tab on both units — if you've got two masters, that's almost certainly your culprit before you start chasing cable faults.

Great thread, this is something I've been looking into myself for the narrowboat setup.

One thing worth adding to what @FenlandSolar and @SomersetVanLifer have touched on — if you're using lithium batteries, make sure your BMS communication is properly sorted before assuming it's a VE.Bus problem. I've seen folk chase their tails with the inverter config when actually the batteries were going into protection mode and the parallel units were disagreeing about state of charge as a result.

@BreezyDrifter for a narrowboat specifically, also worth thinking about whether parallel EasySolars is actually the right route versus a Quattro — the footprint difference matters in a tight engine bay. Victron's own guidance suggests Quattros for most marine parallel applications. Might save you a headache long term!

Parallel EasySolars also need identical firmware versions on both units — even a minor revision mismatch will have them arguing like two blokes fighting over the TV remote, and the batteries just get blamed for the chaos.