DIY backup battery for home: which 48V kit to build
Updated 2026-11-13 · Kit: Most homes, overnight essentials: $3,166 (checked 2026-11-13), one link that opens Sun Gold Power's checkout with all four in the cart: https://dealectric.com/go/kit-48v-10kwh-home-backup
Short answer. For a DIY backup battery for home, pair Sun Gold Power's SPH6548P 6.5 kW 48V inverter with two 51.2V 100Ah LiFePO4 batteries (10.24 kWh). The inverter draws 50–80 W just idling: 23–38% of one battery per day, 12–19% of two.
How this table was made: each figure comes from the maker's own US product page or manual, or from the reviewer named next to it, checked 2026-11-13. Dealectric does not test units itself.
| Model | Who it fits | Battery bank (nominal) | Inverter idle use per day, share of bank (50–80 W, Inverter Geek) | Hours at a 300 W load, idle counted (nominal kWh) | Battery current per pack at 6,500 W output | Price | Buy |
|---|---|---|---|---|---|---|---|
| Most homes, overnight essentials Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power 2 × SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker + Sun Gold Power 250A Bus Bar with Cover | Fridge, Wi-Fi and lights through a night and the next day | 2 × 5.12 = 10.24 kWh | 12–19% (1.2–1.9 kWh) | 27–29 h | about 64 A each (127 A ÷ 2) | $3,166 on sungoldpower.com, 2026-11-13 | $3,166 through this link opens Sun Gold Power's checkout with all four in the cart; tested 2026-11-13 |
| Tight budget, short outages Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker | Essentials through one evening and night; add a pack later | 5.12 kWh | 23–38% (1.2–1.9 kWh) | 13.5–14.6 h | about 127 A on the one pack | $2,105 on sungoldpower.com, 2026-11-13 | $2,105 through this link opens Sun Gold Power's checkout with all three in the cart; tested 2026-11-13 |
| Long outages, bigger loads Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power 4 × SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker + Sun Gold Power 250A Bus Bar with Cover | Multi-day outages or a higher average load | 4 × 5.12 = 20.48 kWh | 6–9% (1.2–1.9 kWh) | 54–59 h | about 32 A each (127 A ÷ 4) | $5,101 on sungoldpower.com, 2026-11-13 | $5,101 through this link opens Sun Gold Power's checkout with all four in the cart; tested 2026-11-13 |
What the differences mean
All three kits use the same inverter, so they differ only in how many 5.12 kWh battery packs it runs from. The figures come from four lines of arithmetic:
- Idle draw per day: 50 W × 24 h = 1,200 Wh; 80 W × 24 h = 1,920 Wh (Inverter Geek's measured range for the SPH6548P).
- Share of the bank: 1,200–1,920 Wh ÷ 5,120 Wh = 23–38% for one pack; ÷ 10,240 Wh = 12–19% for two; ÷ 20,480 Wh = 6–9% for four.
- Hours at a 300 W load: 5,120 Wh ÷ (300 + 80 W) = 13.5 h and ÷ (300 + 50 W) = 14.6 h; two packs 10,240 ÷ 380–350 = 27–29 h; four packs 20,480 ÷ 380–350 = 54–59 h. These use nominal capacity, before inverter conversion losses and any reserve you keep, so real runtime is shorter.
- Battery current at full output: 6,500 W ÷ 51.2 V = 127 A before conversion losses, split across however many packs are connected.
| Your situation | Kit | Why |
|---|---|---|
| Fridge, router, lights and phones through a typical overnight outage | The kit: Most homes, overnight essentials (Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power 2 × SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker + Sun Gold Power 250A Bus Bar with Cover): $3,166 on sungoldpower.com (checked 2026-11-13), one link that opens Sun Gold Power's checkout with all four in the cart: https://dealectric.com/go/kit-48v-10kwh-home-backup | 27–29 h at 300 W. Idle draw takes only 12–19% of the bank. This is the best balance of cost and runtime for most homes ($3,166 in one Sun Gold Power cart on 2026-11-13). |
| Lowest cost now, outages of a few hours, plan to expand | The kit: Tight budget, short outages (Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker): $2,105 on sungoldpower.com (checked 2026-11-13), one link that opens Sun Gold Power's checkout with all three in the cart: https://dealectric.com/go/kit-48v-5kwh-starter | 13.5–14.6 h at 300 W ($2,105). Adding the second pack later turns it into the 10.24 kWh kit. |
| Storm-prone area, outages lasting days, or a higher average load | The kit: Long outages, bigger loads (Sun Gold Power 6.5KW 48V Split Phase Solar Inverter SPH6548P + Sun Gold Power 4 × SG48100P 48V 100Ah Server Rack LiFePO4 Battery + Sun Gold Power 160 Amp DC Breaker + Sun Gold Power 250A Bus Bar with Cover): $5,101 on sungoldpower.com (checked 2026-11-13), one link that opens Sun Gold Power's checkout with all four in the cart: https://dealectric.com/go/kit-48v-20kwh-long-outage | 54–59 h at 300 W, and each pack carries only about 32 A when the inverter runs flat out ($5,101). |
The load you don't plug in: the inverter's own idle draw
An inverter/charger that backs up your home stays switched on around the clock so it can take over the moment the grid drops. James Ndungu at Inverter Geek tested the SPH6548P on a 48V LiFePO4 bank (review updated 2026-04-17) and measured it at 50–80 W continuously just to stay powered on, roughly 1.4–2 kWh a day by his estimate. That energy comes out of the battery before your fridge or router gets any.
The lighter your backup load, the bigger that loss gets. At a 100 W overnight load (router, a few LED lights, a fridge between cycles), one 5.12 kWh pack lasts 5,120 ÷ (100 + 80) = 28 h. Without the idle draw it would last 5,120 ÷ 100 = 51 h, so the inverter takes 44% of the energy. With two packs the same load runs 10,240 ÷ 180 = 57 h. That is why the 10.24 kWh kit is the default here, not the single pack.
Battery count also changes how hard each pack works. At its 6,500 W rating the inverter pulls about 127 A from a 51.2 V bank, and its charger can push up to 140 A back in. Sun Gold Power's own one-battery 6.5 kW kit (SGM-655M) ships with a 160 A DC breaker and 4 AWG cable from the breaker to the inverter. Its two-battery version (SGM-6510M) adds a 250 A busbar and 1/0 AWG battery cables, and the kits here copy that hardware. Before first use, set the inverter's maximum charge current to no more than the limit in the battery manual. This matters most with a single pack.
Not in any cart: a listed transfer switch or protected-loads subpanel, battery cables sized to the run, and a licensed electrician for the panel connection. A battery wired to house circuits must not be able to backfeed the utility, and many areas require a permit for battery storage.
Not recommended
Sun Gold Power 6000W 48V Split Phase Inverter With Charger (low-frequency), if you'll recharge from a 120 V generator or outlet. Its store page states that the split-phase inverter "requires 240VAC input". A 120 V-only source does not meet that requirement, so plan on a 240 V feed or 240 V generator if you choose it. It also cost more than the SPH6548P on 2026-11-13 ($1,220 vs $1,035).
Sources
- SPH6548P idle draw measured at 50–80 W continuous (≈1.4–2 kWh/day), CAN and RS485 BMS communication ports, James Ndungu, updated 2026-04-17; read 2026-11-13 — invertergeek.com
- SPH6548P: 6,500 W rated, 13,000 VA peak, 120/240 V split phase, max 140 A charging, 2 MPPT 550 VDC, UL 1741 by ETL, $1,035; read 2026-11-13 — sungoldpower.com
- SG48100P: 51.2 V 100 Ah, UL1973/UL9540A, CAN/RS485/RS232, ≥7,000 cycles, 10-year warranty, $981; read 2026-11-13 — sungoldpower.com
- SG48100P 2-pack $1,953; read 2026-11-13 — sungoldpower.com
- SG48100P 4-pack $3,888; read 2026-11-13 — sungoldpower.com
- 160 A DC breaker $89; read 2026-11-13 — sungoldpower.com
- 250 A bus bar pair with cover, 48 VDC, $89; read 2026-11-13 — sungoldpower.com
- Maker's 6.5 kW kits: 160 A DC breaker + 4 AWG (one battery); 250 A busbar + 1/0 AWG battery cables (two batteries); read 2026-11-13 — sungoldpower.com
- 6000W 48V LF split-phase inverter/charger 'requires 240VAC input', $1,220; read 2026-11-13 — sungoldpower.com
Published 2026-11-13; updated 2026-11-13. The buy links are affiliate links; see the disclosure. Corrections welcome at [email protected] or /feedback.