Batteries

What is battery bottom-balancing when paralleling packs in SA home solar?

Bottom-balancing means bringing paralleled lithium modules to a matched low state of charge before tying them together so currents share evenly — follow the OEM parallel guide; mismatched ages or chemistries are a common warranty killer.

Updated 27 October 2026 · Illustrative ranges — not a formal quote, credit decision or legal advice.

Answer first: If you expand capacity, use the same model/firmware generation and the OEM’s parallel harness. Ask the installer to document the balance procedure — battery parallel expansion · parallel stacking · warranty checks · usable kWh · batteries.

Why mismatch hurts

Mismatch	Risk
Different cycle ages	One pack hogs current
Different firmware	BMS disagreements
Different capacities	Uneven DoD / early cut-off

cycle / DoD · firmware · expand later.

Desk close

Keep metro and OEM PDFs beside this page. When rand bands disagree with a live primary, the primary wins — metro tariffs · tariffs 2026 · choose installer · get quotes · check a quote.

Sources homeowners can open

Your metro SSEG / tariff PDF (live municipal site).
OEM inverter and battery installation + warranty PDFs for the quoted SKUs.
NERSA and municipal tariff schedules for the current year.
SANS / NRS notes via your registered electrician.

Commissioning evidence pack

Serial photos, firmware version, export-limit screenshot, CT polarity photo, dual-supply labels, CoC number, guest monitoring login — with the invoice PDF — CoC · export limit · CT clamps · labels · firmware · warranty claims.

Tariff and fixed-charge reminder

Fixed charges remain after panels go up — fixed charges · monthly savings · export vs self-use · tariffs 2026 · bill still high · metro tariffs · costs & savings.

Safety do-not list

Do not DIY dual-supply boards, earthing, or MC4 strings.
Do not bridge RCDs or defeat BMS protections.
Do not ignore isolation or earth-fault alarms.
Do not disable export limits or grid-interface settings.

DIY risks · earth leakage · MC4 · DC isolation · red flags · N-E island.

Stage-weekend reality check

Essentials first through your worst Stage window — essentials · Stage strategy · Stage 4 · SoC · Stage table · load shedding hub.

Extra SA context

Keep metro and OEM PDFs beside this page. When rand bands disagree with a live primary, the primary wins — choose installer · get quotes · check a quote · FAQ · about · batteries.

Handover note 1

Photograph serials, labels and the essential board before the cover closes. Keep guest monitoring access with the invoice. When Stage calendars change, revisit SoC floors — SoC · Stage strategy · Stage 4 · essentials · monitoring · choose installer · get quotes · check a quote · FAQ · about · costs & savings · batteries.

Handover note 2

Handover note 3

Handover note 4

Handover note 5

Handover note 6

Handover note 7

Handover note 8

Extra SA context note 2

Keep metro and OEM PDFs beside this page. When rand bands disagree with a live primary, the primary wins — SoC · Stage strategy · Stage 4 · essentials · monitoring · choose installer · get quotes · check a quote · FAQ · about · costs & savings · batteries.

Extra SA context note 2

Installer questions to ask

Who signs the CoC, what export setpoint is approved, and where is the guest monitoring login written down — CoC · export limit · guest monitoring · choose installer · check a quote.

Parallel pack commission without bottom-balance drama

Parallel LiFePO₄ packs need similar open-circuit voltages before closing interconnects. Bottom-balance folklore from DIY forums does not replace the OEM parallel procedure. Follow the brand’s voltage window, enable the specified parallel/comms cables, and confirm each BMS reports on the inverter. Mixing old and new packs of different cycle ages often voids warranty.

Buy parallel-ready SKUs with matching firmware generations.
Document SoC and voltage of each pack at interconnect.
Expand later only within the OEM’s max parallel count — parallel expansion · compatibility · DoD.

Homeowner close-out for battery bottom balance parallel sa

Keep OEM and metro PDFs beside this answer. Confirm Incl. VAT line items, NRS-listed SKUs where relevant, and who owns paperwork after deposit. Compare two written scopes before you pay — read a quote · choose installer · check a quote · get quotes · costs & savings · metro tariffs.

Parallel packs need a deliberate balance procedure

Mismatched SoC on parallel lithium packs causes circulating current and early BMS trips. Follow the brand’s bottom-balance / bring-up steps before closing the bus. Mixing old and new packs without guidance voids many warranties.

After install, watch pack voltage delta on the monitor for the first week. Growing divergence means a cable, settings, or pack health issue — call the installer while the system is still under commissioning cover.

Quick questions

Do all brands require it?

Follow the OEM parallel manual — procedures differ.

Can I mix old and new packs?

Usually a bad idea; many warranties forbid mixed lots.

Top vs bottom balance?

OEM specifies which; do not invent a method.

DIY?

No — BMS and busbar work is installer territory.