Do I need one or two B300K batteries with a BLUETTI Apex 300 for my RV?
The Apex 300 holds 2,764Wh on its own, and each B300K adds another 2,764.8Wh. Output stays at 3,840W whichever you pick, so the only question is storage. That depends on two numbers you multiply together: what your rig uses in a day and how many days you go without recharging.
The rule our calculator uses
| Daily use x days without charging | Station |
|---|---|
| Up to 2,764Wh | Apex 300 alone |
| 2,765-5,529Wh | Apex 300 + one B300K |
| 5,530-8,294Wh | Apex 300 + two B300K |
The calculator sizes stations on the raw trip total, because BLUETTI already rates them in usable watt-hours.
Worked rigs, 1 to 3 days
Daily figures use the calculator's own allowances: 18Ah base, a 12V fridge at 25Ah, and so on, at 12.8V. Rooftop AC is a 13,500 BTU unit at 1,400W running, through a 92% efficient inverter.
| Rig, per day | 1 day | 2 days | 3 days |
|---|---|---|---|
| 12V fridge + CPAP + Standard Starlink, 1,318Wh | below the Apex* | Apex alone (2,636) | One B300K (3,954) |
| Everything on: fridge, TV, laptop, Standard dish, furnace, CPAP + humidifier, coffee, 1,920Wh | below the Apex* | One B300K (3,840) | Two B300K (5,760) |
| 12V fridge + rooftop AC 2 warm hours, 2,224Wh | Apex alone | One B300K (4,448) | Two B300K (6,672) |
| 12V fridge + rooftop AC 4 warm hours, 3,898Wh | One B300K | Two B300K (7,796) | past two |
\*Small enough that the calculator picks a smaller station.
The pattern: one B300K covers two days of a heavy rig with no AC, or one day with a few hours of AC. Two B300K cover three days of everything-on, or two days with four hours of AC. If it's a full night of rooftop AC more than once, plan on shore power or a generator to refill, not more batteries. Or cool just the bedroom with a low-draw battery camping AC; see battery camping AC vs a regular portable AC.
Start with one, add later?
That works. BLUETTI allows up to six B300K on one Apex 300 through the CA90 connection. Order the Apex 300 version of the B300K, because there are also AC200L/AC300 and AC500 versions with different part numbers. Each B300K weighs 65.04 lb, so a second one is a real weight on a trailer's cargo capacity.
If you camp with solar, the days in the table stretch, because the panels put energy back each day. BLUETTI equipment from us ships free in the lower 48.
Put in your own loads and days in our RV solar & battery calculator. It picks the station from the same ladder.
Shop the full BLUETTI range at RV Parts Giant.
What you need
Want the full walkthrough? Read the complete guide.