· Edition #24

The Busbar

Off-Grid Garage charged a 137kWh bank built from batteries of different sizes and cable lengths: in bulk, current split by path resistance, not capacity.

Twice the capacity, the same current: Off-Grid Garage shows a parallel bank splitting charge by path resistance

Andy's newer batteries, further from the chargers, have twice the capacity of his original shelf but took the same 50A in bulk. The split only moved to them once the shelf reached absorption: 5A against 140A.

In a video published on 8 October, Off-Grid Garage's Andy fully charged his whole 48V bank for the first time since connecting the new "PowerWall" side. It now holds about 137kWh in seven batteries. The original battery shelf (three packs, 864Ah) sits right next to the chargers' busbar. The PowerWall batteries are further away, connected through four 95mm² cables, a breaker and a second SmartShunt. They are an MB56-cell pack, a CL530 pack and two packs of about 310Ah, around 1,778Ah by our sum. Andy describes them as double the shelf's capacity.

In bulk, at about 54V, each side took about 50A. The two shunts read about 100mV apart, which Andy puts down to "all the cabling and connection points". Twice the capacity got the same current. By our arithmetic, that means the shelf was charging at roughly twice the C-rate of the PowerWall.

Then the shelf neared full. At 54.66V the split was 42A to the shelf and 100A to the PowerWall. Near 55.2V it was 5A against 140A. Inside the PowerWall, the MB56 pack took almost 70A while a 314Ah pack took 5–7A. One shelf battery took 1.9A while another battery in parallel took 70A.

Andy raised absorption from one hour to over three to let the packs settle. The CL530 pack, which carries one MB56 cell in place of a cell damaged in transport, peaked near 80mV of cell spread on a 2A balancer. A V19 JK BMS reported 78% state of charge at 55.4V while accepting 1.2A. His view is that the imbalance mostly shows when batteries are first added. He argues that ten short absorptions do the same job as one long one. With 70A flowing, the connectors measured about 32°C.

The bank worked. But on the charge side it behaves like its nameplate only at the top. For most of the day, the nearest batteries do more of the work. The Background explains why.

Venus OS v3.81 stops the new Cerbo GX MK3 rebooting with memory to spare

A week after the MK3 surfaced, Victron's first follow-up release fixes reboots on it, plus two regressions introduced in v3.80.

Victron released Venus OS v3.81 on 7 October. On the Cerbo GX MK3, which Panbo reported last week, the device "no longer reboots while plenty of free memory remains", and about 19MB more RAM is available. Victron doesn't say how often the reboots happened. Anyone setting up a new MK3 should check it is on v3.81 or later. The release also fixes two problems introduced in v3.80. The Classic UI was missing AC and DC values for VE.Bus devices in the device list. And Modbus-TCP register 232 (/MicroGrid/OperationSwitcher/Operation) had been made read-only by mistake. New registers are 235 (MicroGrid AllowBlackStart) and 129 (the VE.Bus Weak AC Input setting). Installers can now enable Shared Voltage Sense on Pytes batteries.

IBEX electrical awards go to a two-box alternator regulator and a sealed small-boat distribution module

ARCO's Zeus Omega, our June Lead, shares the Electrical Systems category with Egis Mobile Electric's Modular PDM.

The 2026 IBEX Innovation Awards, judged by Boating Writers International and the NMMA, were announced in Tampa on 6 October. Two products share the Electrical Systems category. One is ARCO's Zeus Omega, which we led with in June: the judges' citation says it "splits the alternator regulator in two", with a potted drive module at the alternator and a control module near the batteries, joined by one cable. The other is Egis Mobile Electric's Modular Power Distribution Module. In the citation's words, "small-boat DC systems have long been a patchwork of switches, fuse blocks, and bus bars". The PDM puts them in "one sealed, ignition-protected module" with fuses, resettable breakers, Deutsch connectors and NMEA 2000 control. Egis's product page gives no current ratings or price for it yet. AquaAmp's Smart DT Connector received an honourable mention.

Open-source Battery Pack Card adds a whole-bank view and phone alerts for Home Assistant

Four releases in nine days turned a one-pack Lovelace card into a bank overview with a JK-style display and, in alpha, automatic alert automations.

Battery Pack Card is an MIT-licensed Home Assistant card by Sven Hamers that draws a lithium pack with its cells, temperatures and alarms. Version 1.6.0 (1 October) added a Battery Stacked Pack Card that draws a whole bank as cases in a cabinet. Version 1.7.0 (3 October) added a bank display styled after the JK BMS screen. It works out voltage as the packs' mean, sums current and capacity, and weights SOC by capacity. 1.9.0 (9 October) lists packs found through the JK-BMS RS485 add-on and credits "Andy" (Off-Grid Garage) for ideas. The same day, 2.0.0-alpha.1 added alerts for cell difference, cell voltage, temperature, low SOC, BMS alarms and a BMS switching charge or discharge off. Critical alarms break through a phone's silent mode. The card writes only its own automations, "never to the BMS". It isn't JK-only: Seplos, Daly, JBD and Pace work if their data is in Home Assistant.

Anker SOLIX S5000: 5kWh, a TT-30 outlet and an 8.8W idle draw

Marketed for home backup, but the RV outlet, a 165V solar input and the published idle draw make it relevant to RV owners. $2,499.99 at launch on 27 October.

Anker announced the SOLIX S5000 on 9 October. It is a 5,024Wh power station built on 314Ah LFP cells, with 4,500W continuous and 8,000W peak at 120V or 240V. It has four NEMA 5-20 outlets, an L14-30 and a TT-30 RV outlet. There are two solar inputs: 11–60V (1,000W) and 16–165V (2,000W), each up to 17A. It weighs 97lb on wheels, expands to 30kWh and lists UL 9540 and UL 9540A. Anker rates it at 6,000 cycles to 80% and gives a five-year warranty. The figure worth having is idle draw: 8.8W in 120V mode and 13.7W at 240V. By our arithmetic, 8.8W is 211Wh a day, about 4% of the battery, whatever you run. Anker continues the published-idle-draw approach we noted on the S2000. Launch price is $2,499.99 from 27 October; the MSRP is $3,599.99.

Find on Amazon →

Dragonfly Energy, Battle Born's parent, does a 1-for-8 reverse split to stay on Nasdaq

Effective today, 12 October. The aim is to lift the share price above Nasdaq's $1 minimum bid.

Dragonfly Energy filed an 8-K on 8 October reporting a 1-for-8 reverse stock split, effective 12:01am Pacific on 12 October. The stated aim is to raise the closing bid price "above $1.00 per share" and stay compliant with Nasdaq Listing Rule 5550(a)(2). Authorized common stock falls from 400 million to 50 million shares, and the CUSIP changes to 26145B 601. The filing mentions no deficiency notice or deadline. This follows the eighth term-loan amendment a week earlier, under which lenders waived the September minimum-liquidity test. A reverse split changes the share count, not the business. For Battle Born owners, the open question is still the long-term backing for the warranty.

The Background · Standards Explainer

Parallel batteries share current by voltage, not by capacity

Most builders picture a parallel bank like a set of buckets: double the capacity, double the share. The Lead shows a better model. In parallel, each battery is a voltage source (its resting voltage at its current state of charge) behind a resistance. That resistance is the cells' own internal resistance plus everything between the cells and the common busbar: cable, lugs, fuse, breaker, shunt. All the batteries see the same busbar voltage. Each one's current is set by how far that busbar voltage sits above its own resting voltage, divided by its total resistance. Capacity doesn't appear in that calculation.

Why resistance wins in the middle

Across most of its range, LiFePO4 has a very flat voltage curve. Two batteries at 40% and 70% state of charge rest at almost the same voltage. So in bulk, the voltage gap is roughly equal for every battery, and the split is set by resistance. At this scale resistance means milliohms. As an illustration (our arithmetic, not Andy's measurement): with the busbar 100mV above resting voltage, a 2mΩ path carries 50A and a 4mΩ path carries 25A. That holds whether the battery behind it is 100Ah or 600Ah. The Lead's two sides took equal current in bulk despite a 2:1 capacity ratio, which fits this.

Why it fixes itself at the top

Above about 3.4V per cell, the curve turns steeply upwards. A battery that is nearly full now raises its resting voltage quickly as charge goes in. Its gap to the busbar closes and its current falls. The emptier batteries, still on the flat part, take over. That is the 42A→5A fall on Andy's shelf while the PowerWall rose to 140A. The flat curve that let resistance decide in bulk lets state of charge decide near full. The bank converges, but only if the charger holds absorption long enough. That is why Andy extended it from one hour to three.

What it means in practice

First, a mixed bank works, as Andy's does. But for most of a charging day, the batteries with the shortest path see the highest C-rate. If the nearest battery is also the smallest, it works hardest relative to its size. The same physics applies in reverse on discharge under heavy loads. Second, the usual textbook layout puts each battery on equal-length cables to a common busbar, with its own fuse. That layout equalises resistance, not capacity. It removes the uneven share in bulk but not the effects of age or state-of-charge differences. Third, state of charge per battery drifts apart between full charges: Andy's 78%-at-55.4V reading is an example. A bank-level number aggregated over CAN, as in JK's mixed-generation test, is more reliable than any single BMS's estimate.

None of this needs new hardware. It needs a different picture of the bank: one busbar voltage and several resistances in parallel.

Community Pulse

What the forums are talking about this week

Three r/vandwellers posts this week connect to recent editions.

On 6 October, a builder installing two Victron 235W panels in parallel wanted a 100/30 rather than the 100/50 that online calculators suggest. They expect the panels' roughly 33A peak to be rare and clipped, and note correctly that the 100V limit is not negotiable. This is the same decision as Alec Hughes' over-panelled 75/15s in September: rated controller power isn't the same as harvest, and voltage, not current, is the hard limit.

The same day, another poster asked how people check a Bluetooth BMS on the road. They summarise app-store reviews of JK, JBD/Xiaoxiang and Daly apps: accounts required, some needing internet, dropping links, switching between batteries. They also ask whether people trust the app's SOC or a shunt. That ties to the Daly lockout in our 28 September Background.

On 10 October, an owner's Arctic Tern AirPlus roof fan, installed in May and used 20–30 times, stopped opening and closing on its own and squeals unless the lid is closed by hand. It is the fan from our 7 September airflow test.

We can read the opening posts but not the replies, so treat these as questions, not settled answers.

On the Bench

YouTube picks: builds, teardowns, firmware walkthroughs, and reviews

New PowerWall connects for the first time. Lots to check and test...
Build Walk-through
Off-Grid Garage · 3 October 2026
The first time this side of the bank was switched on. Resistance and voltage checks before closing the MCCB, then an infrared walk-around at up to 180A: connections no more than about 5°C over ambient.
LiTime 12V 100Ah Trolling Motor Battery: Honest Review and Teardown
Teardown
Cleversolarpower by Nick · 27 September 2026
Measured 101.4Ah, the 100A BMS tripping in about 10s at 160A and recovering in about 25s, a full discharge at 100A without thermal shutdown, and a cold-charge cutoff check. Inside: Great Power cells and 39Ω balance resistors (about 88mA). The description includes affiliate links.

Product Radar

New and notable components announced or launched this week

SOLIX S5000 — Anker
Battery

5,024Wh power station on 314Ah LFP cells; 4,500W continuous / 8,000W peak at 120V or 240V; TT-30 and L14-30 outlets; solar inputs of 11–60V (1,000W) and 16–165V (2,000W); 8.8W idle at 120V; expands to 30kWh; UL 9540 / 9540A; 97lb.

$2,499.99 at launch (MSRP $3,599.99) On sale 27 October 2026 (US) Find on Amazon →
Marketed for home backup; the TT-30 outlet and the published idle draw are what make it relevant to RV owners (News 4).
Modular Power Distribution Module — Egis Mobile Electric
Marine

Sealed, ignition-protected DC distribution module for small boats: fuses, resettable breakers, Deutsch connectors, NMEA 2000 control, stackable and linked by busbars.

Not published Shown at IBEX 2026; no date given
IBEX Electrical Systems co-winner (News 2). Current ratings aren't published yet, and those are what a builder needs.

Pre-wired mobile power panels built around the BCDC Alpha50 R (50A DC-DC with MPPT solar, solar given priority). Nomad50 adds a Smart Battery Monitor and fuse block (6×30A blade, 4×100A MIDI), 465 × 308 × 79mm, 7.1kg. Pioneer50 adds the TVMS Rogue and RedVision Pro Display.

Nomad50 $2,199; Pioneer50 $2,899.01 (REDARC US store) Available now in the US; 'official launch' announced 6 October 2026
The smaller Scout25 and QuickFit100 were covered when they appeared at Overland Expo in May; the 50A panels are new to us. Two-year warranty.
Battery Pack Card / Battery Stacked Pack Card — Sven Hamers (open source, MIT)
Monitoring

Home Assistant cards showing per-cell voltages, temperatures and alarms for each pack, plus a whole-bank cabinet view with a JK-style display. Alerts added in the 2.0 alpha. Installed through HACS.

Free v1.9.0 stable and v2.0.0-alpha.1 released 9 October 2026
Software, not hardware. Listed because it gives one view across BMS brands, which their own apps don't (News 3).