48V Lithium Battery for Solar: Sizing and Selection
48V is the default for residential and light-commercial solar because it halves the current of a 24V system and matches the input window of most hybrid inverters. The sizing logic is straightforward once you separate array size from battery size.
Sizing Table
| Nightly consumption | Recommended usable capacity | 48V bank |
|---|---|---|
| 2–3 kWh | 3 kWh | 48V 50Ah + margin |
| 4–5 kWh | 5–6 kWh | 48V 100–150Ah |
| 6–8 kWh | 8–9 kWh | 48V 200Ah |
| 9–12 kWh | 11–13 kWh | Two 48V 150Ah |
The 1.2–1.5 multiplier covers inverter losses, cold nights and cloudy-day reserve. If the site must ride through a full cloudy day, increase it.
Array Size Is a Different Question
The array has to recharge the bank and carry daytime loads. A common starting point is 1.2–1.5kW of panels per 5kWh of battery in a good-sun region, more in low-sun or winter conditions. Do not size the battery to the array — size it to the load.
Inverter Compatibility
Most 48V hybrid inverters accept a DC window of roughly 40–60V and expect CAN or RS485 communication with the battery. Confirm the protocol and the charge current limit before ordering; a battery that cannot communicate may still run in voltage mode but without BMS limits.
Series, Parallel and Expansion
48V packs are internally 16S (or 15S for some telecom models). Do not series-connect 48V batteries to reach a higher voltage — parallel them for capacity instead, with equal cable lengths and matched units. Plan busbar and breaker capacity for one future expansion.
5kW and 10kW Solar Configurations
Most off-grid questions start with the inverter size, but the bank and the array have to be sized together. The table below is a starting point for a 48V system with lithium batteries, assuming 80% usable capacity and a 0.8 derate on array output.
| Daily load | Array | 48V bank | Inverter | Autonomy (no sun) |
|---|---|---|---|---|
| 5 kWh/day | 2 kW | 48V 100Ah (5.1 kWh) | 3 kW | ≈0.8 day |
| 8 kWh/day | 4 kW | 48V 200Ah (10.2 kWh) | 5 kW | ≈1 day |
| 12 kWh/day | 6 kW | 2 × 48V 200Ah (20.5 kWh) | 8 kW | ≈1.4 days |
| 20 kWh/day | 10 kW | 4 × 48V 200Ah (41 kWh) | 10–12 kW | ≈1.6 days |
Two of these rows are deliberately conservative. A 5kW inverter on a 100Ah bank will run, but any simultaneous kettle, pump and air-conditioner start will trip the BMS; the 200Ah row is the smallest bank we would quote for a 5kW whole-house inverter.
PV Charge Current and Recharge Time
Array watts translate into charge current at roughly 55V for a 48V lithium pack. Use the table to check that the array does not exceed what the battery can accept, and to estimate how long a depleted bank takes to come back.
| Array (derated) | Approx. charge current | Time to refill 100Ah from 20% | Time to refill 200Ah from 20% |
|---|---|---|---|
| 2 kW (1.6 kW) | ≈29A | ≈3 hours | ≈6 hours |
| 4 kW (3.2 kW) | ≈58A | ≈1.8 hours | ≈3.5 hours |
| 6 kW (4.8 kW) | ≈87A | ≈1.3 hours | ≈2.5 hours |
| 10 kW (8 kW) | ≈145A | exceeds 100A BMS — use 2 packs | ≈1.6 hours on 2 packs |
A single 48V 100Ah pack accepts about 100A, so an array above roughly 7kW needs two packs in parallel or an inverter/charger that can limit charge current. Oversizing the array without checking this is a common cause of BMS charge cut-offs at midday.
Autonomy: How Many Days Without Sun
Autonomy is usable energy divided by daily consumption. At 80% depth of discharge, a 48V 100Ah pack gives about 4.1 kWh usable, and a 200Ah pack about 8.2 kWh.
| Bank | Usable energy | 1 day at | 2 days at | 3 days at |
|---|---|---|---|---|
| 48V 100Ah | ≈4.1 kWh | 4.1 kWh/day | 2.0 kWh/day | 1.4 kWh/day |
| 48V 200Ah | ≈8.2 kWh | 8.2 kWh/day | 4.1 kWh/day | 2.7 kWh/day |
| 2 × 48V 200Ah | ≈16.4 kWh | 16.4 kWh/day | 8.2 kWh/day | 5.5 kWh/day |
For a site that cannot tolerate downtime — a clinic, a telecom repeater, a cold-storage room — design for two days of autonomy and treat the third day as generator or grid backup, rather than sizing the bank for the worst week of the year.
Frequently asked questions
About 1.2–1.5kW of panels in a good-sun region to recharge 4.8kWh in a day while carrying daytime loads. Low-sun or winter sites need more.
No. The inverter’s DC window must match the battery’s voltage class. A 48V pack on a 24V inverter will not start and may be damaged.
Below about 2kWh of nightly use, 24V is often cheaper and simpler. Above that, 48V reduces current and cable size and matches common hybrid inverters.
80–90% is normal for LiFePO4, unlike lead-acid’s 50%. Sizing at 90% DoD leaves little reserve for cold or aged cells; 80% is a safer design target.
Related reading
Use the battery bank sizing guide, see the 48V battery range, or read about hybrid vs off-grid inverters.
For worked current and runtime figures, read 48V battery bank sizing for 5kW and 10kW loads.
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