ARRMA Mojave 6S battery compatibility confuses a lot of new owners, and honestly, the documentation that comes in the box doesn’t help much. You’ve got a desert truck designed to handle serious punishment, but if you’re running the wrong battery dimensions, discharge rate, or connector type, you’re either leaving performance on the table or risking damage to your investment. This guide covers everything from the basics of what fits in the battery tray to the chargers that won’t let you down, plus we’ll tackle diff oil weights and servo upgrades since those questions almost always come up together.
The Mojave 6S BLX runs a 2050Kv brushless motor paired with a Spektrum Firma 150A ESC, which means it demands serious current from your battery pack. We’re talking peak draws that can exceed 100 amps during hard acceleration out of corners or when you’re climbing steep dunes. The stock battery tray accepts packs up to 155mm long, 47mm wide, and 48mm tall per side. That’s the starting point, but there’s a lot more to getting this right.
By the time you finish reading, you’ll know exactly which batteries fit without modification, which chargers balance properly at the right rates, what diff oil viscosities work for different terrain, and which servo upgrades actually survive the abuse this truck dishes out. Let’s get into it.
Understanding the Mojave 6S Power System
The Mojave 6S runs on 22.2 volts nominal when fully charged, delivered through either two 3S packs in series or a single 6S pack. The Spektrum Firma 150A ESC handles the current management, and it’s rated for 6S operation with a BEC output of 7.4 volts at 9 amps. That BEC rating matters because it determines how much power your servo and receiver get, which becomes relevant when we talk about upgrades later.
The 2050Kv motor spins at roughly 2050 RPM per volt under no load. With a fully charged 6S pack sitting at 25.2 volts, you’re looking at theoretical motor speeds over 51,000 RPM before gearing. The stock pinion and spur combination brings wheel speed down to a manageable level, but the point is that this system pulls serious current.
Peak current draw during hard acceleration can hit 120 amps momentarily. Sustained draws during aggressive driving typically hover between 60 and 80 amps. This is why battery C rating matters so much. A 5000mAh pack rated at 50C can theoretically deliver 250 amps, which sounds like plenty. But real world performance of budget packs rarely matches their advertised ratings.
The ESC has built in protection that will throttle power if it detects voltage sag from an inadequate battery. You’ll notice this as sudden power cuts during hard acceleration or reduced top speed. If you’re experiencing these symptoms, your battery’s discharge rate probably isn’t keeping up with demand.
Battery Dimensions and Physical Compatibility
The Mojave 6S battery tray is designed for two separate battery compartments, one on each side of the chassis. Each compartment measures approximately 158mm long, 50mm wide, and 50mm tall. However, the recommended maximum battery dimensions are 155mm x 47mm x 48mm per pack. That 3mm buffer on each dimension accounts for wire routing and the slight flex in the battery straps.
Here’s where it gets tricky. Not all 3S 5000mAh packs share the same dimensions. Some brands run longer and thinner, others shorter and fatter. Zeee, Gens Ace, Spektrum, and Turnigy all have slightly different form factors even at identical capacity ratings.
The Spektrum Smart batteries in the 5000mAh 3S configuration measure 139mm x 47mm x 30mm. These fit with room to spare. Gens Ace 5000mAh 3S hardcase packs typically measure 138mm x 46mm x 38mm, also fitting comfortably. Zeee 5000mAh 3S packs run about 155mm x 46mm x 25mm, fitting but leaving less clearance lengthwise.
If you want to run a single 6S pack instead of two 3S packs, you’ll need to use only one battery compartment or modify the tray. Single 6S hardcase packs in the 5000mAh range typically measure around 139mm x 47mm x 50mm. The height becomes the limiting factor here. Some owners remove the center divider to accommodate larger single packs, but this affects weight distribution.
Weight distribution matters more on the Mojave than on some other ARRMA trucks because of its desert racing design. The suspension geometry assumes relatively balanced weight between front and rear. Running a single heavy pack on one side can cause handling issues, especially during high speed cornering.
Connector Types and Wiring Considerations
The Mojave 6S comes stock with IC5 connectors, which are Spektrum’s proprietary system rated for 150 amps continuous. These connectors are solid and reliable, but they limit your battery choices to packs that either come with IC5 connectors or that you’re willing to re-terminate.
Many aftermarket batteries ship with EC5 connectors, which are physically similar to IC5 but not identical. EC5 connectors will technically mate with IC5 sockets, but the fit is slightly loose. This can cause resistance at the connection point, leading to heat buildup during high current draws. Over time, this heat degrades the connectors and can cause intermittent power issues.
The safest approach is to either buy batteries with genuine IC5 connectors or re-solder your batteries with IC5 plugs. Soldering IC5 connectors requires a higher wattage iron, at least 60 watts, because the large contact surfaces act as heat sinks. Use quality solder with flux core and pre-tin both the connector and wire before joining.
Some owners switch their entire fleet to a different connector standard like EC5 or XT90. This requires changing the connectors on the ESC as well, which voids your warranty but gives you more battery options. XT90 connectors are rated for 90 amps continuous and 120 amps burst, which is adequate for most driving but may become a limiting factor during sustained full throttle runs.
→ 6S LiPo Battery, Look for packs rated at least 100C with IC5 connectors to avoid re-termination and ensure adequate current delivery for the Mojave’s 150A ESC.
Discharge Ratings and Real World Performance
C rating on LiPo batteries indicates the maximum safe discharge rate as a multiple of capacity. A 5000mAh pack rated at 100C can theoretically deliver 500 amps. In practice, these ratings are often optimistic, especially on budget brands.
For the Mojave 6S, we recommend packs rated at minimum 100C from reputable brands. This gives you headroom above the 120 amp peak draws the system can demand. Running a 50C pack might work for casual driving, but you’ll notice voltage sag during hard acceleration and reduced punch overall.
Internal resistance is actually a better indicator of battery performance than C rating, but manufacturers rarely publish this spec. Lower internal resistance means less energy lost as heat and better voltage stability under load. Spektrum Smart batteries display internal resistance on compatible chargers, which is one advantage of staying in the Spektrum ecosystem.
Temperature also affects discharge capability. Cold batteries have higher internal resistance and deliver less current. If you’re running in winter conditions, keep your packs warm before driving. Some owners use insulated battery bags or hand warmers in the pits. Never charge a cold LiPo below 40°F (4°C) as this can cause permanent damage to the cells.
For extended run times, capacity matters more than C rating once you’re above the minimum threshold. Two 5000mAh 3S packs give you 5000mAh total at 6S (capacity doesn’t add in series, only voltage). If you want longer runs, look for 6000mAh or even 6500mAh packs that still fit the dimensional requirements.
Charger Requirements for 6S Operation
Charging 6S LiPo batteries requires a charger capable of handling 22.2V nominal voltage and balancing six cells. Many entry level chargers max out at 4S, so verify your charger’s specifications before assuming it will work.
The charging rate, measured in amps, determines how quickly your packs reach full charge. A 1C charge rate means charging at the same amperage as the pack’s capacity in amp hours. For a 5000mAh pack, 1C equals 5 amps. Most LiPo manufacturers recommend charging at 1C or below for maximum battery lifespan.
However, modern high quality packs often support 2C or even 3C charging. This cuts charge time significantly but generates more heat and may reduce total charge cycles over the battery’s life. For weekend bashing where you need fast turnaround between packs, 2C charging is a reasonable compromise.
Balance charging is non-negotiable for LiPo safety. This process ensures all cells in the pack reach the same voltage, preventing overcharging of individual cells. Never use a non-balance charger on multi-cell LiPo packs. The balance lead, that small white connector with multiple wires, must be connected during every charge.
Storage charging is equally important. LiPo batteries should be stored at 3.8V per cell, which is about 22.8V for a 6S pack. Storing fully charged packs degrades them faster and increases fire risk. Most quality chargers have a storage mode that either charges or discharges to the optimal storage voltage.
→ LiPo Balance Charger, Get a charger rated for at least 6S and 10 amps output to handle 2C charging on 5000mAh packs without waiting all afternoon.
Charger wattage limits actual charge rate regardless of the amp setting. A 100W charger trying to charge a 6S pack at 5 amps is pushing about 125W (25.2V x 5A), which exceeds its capacity. The charger will automatically reduce the charge rate to stay within its power limit. For 6S charging at useful rates, look for chargers rated at 200W or higher.
Dual channel chargers let you charge two packs simultaneously, which is ideal for the Mojave’s two battery setup. Some chargers can even charge both packs from a single power supply while maintaining independent balance on each. This cuts your pit time in half compared to charging sequentially.
Diff Oil Weights for Different Terrain
The Mojave 6S uses three differentials: front, center, and rear. Each can be tuned with different oil viscosities to change how power transfers between wheels. Stock oil weights are typically around 7000cst front, 1,000,000cst center (essentially locked), and 7000cst rear. These work reasonably well for general bashing but can be optimized for specific conditions.
Diff oil viscosity is measured in centistokes (cst). Higher numbers mean thicker oil, which makes the diff act more locked. Lower numbers mean thinner oil, allowing more differential action between the wheels. A completely locked diff transfers power equally to both wheels, while a completely open diff allows one wheel to spin freely if it loses traction.
For loose surfaces like sand and gravel, thicker rear diff oil helps prevent one-wheel burnouts and improves forward traction. Try 10000cst or even 15000cst in the rear diff for desert conditions. The front diff can stay around 7000cst or go slightly thinner to 5000cst for better steering response in loose terrain.
For hardpack dirt or clay tracks, the stock weights work well. You want some differential action to help the truck rotate through corners without pushing. If you’re experiencing understeer, try thinner front diff oil around 5000cst. For oversteer or excessive rear end sliding, thicken the rear to 10000cst.
The center diff on the Mojave is often run very thick or completely locked from the factory. This provides predictable power delivery and prevents the front or rear from spinning independently during jumps. Some owners thin the center diff to 100000cst or even 30000cst for more natural cornering behavior, but this can cause issues with uneven tire wear if the front and rear tires are different diameters.
Changing diff oil requires removing the diff from the truck, disassembling the case, cleaning out the old oil, and reassembling with new oil. It’s a 30 to 45 minute job per diff once you’ve done it a few times. Use a small syringe to inject oil into the case, filling it completely before closing. Air bubbles in the diff will cause inconsistent behavior.
Side-by-Side Battery Specifications
| Specification | Minimum Recommended | Optimal Setup |
|---|---|---|
| Configuration | 2x 3S in series | 2x 3S in series or 1x 6S |
| Capacity | 4000mAh | 5000-6000mAh |
| Discharge Rate | 75C | 100C+ |
| Connector Type | IC5 compatible | Genuine IC5 |
| Max Length | 155mm | 140mm for clearance |
| Max Width | 47mm | 46mm for clearance |
| Max Height | 48mm | 40mm for clearance |
| Voltage (charged) | 25.2V total | 25.2V total |
| Voltage (nominal) | 22.2V total | 22.2V total |
| Weight per pack | 350g | 400-500g |
Servo Upgrades That Actually Survive
The stock servo in the Mojave 6S is adequate for casual driving but becomes a weak point during aggressive bashing. Desert trucks put enormous stress on the steering system due to impacts with rocks, ruts, and landing from jumps. The stock servo’s plastic gears can strip under these loads, leaving you with a truck that won’t turn.
Metal gear servos are the standard upgrade path. Look for servos rated at least 25kg-cm torque at 7.4V, which matches the BEC output of the Spektrum ESC. Speed rating matters too, expressed in seconds per 60 degrees of rotation. Faster servos provide quicker steering response but may sacrifice some torque.
The Mojave uses a standard size servo with mounting dimensions of 40mm x 20mm x 37mm. Most aftermarket servos match these dimensions, but always verify before purchasing. The servo horn spline count must also match. ARRMA uses 25 tooth splines on most of their servo horns.
Coreless and brushless servos offer improvements over traditional brushed designs. Coreless servos provide smoother operation and faster response. Brushless servos add even more speed and eliminate brush wear entirely. For the Mojave’s demands, a quality metal gear brushless servo in the 30kg-cm range provides excellent performance and durability.
→ Metal Gear Servo, Choose a 25kg-cm or higher torque rating with metal gears to handle the steering loads the Mojave generates during hard landings and rock impacts.
Servo savers are another consideration. The Mojave includes a servo saver in the steering linkage, which absorbs impacts that would otherwise damage the servo. Some owners replace this with a solid aluminum horn for more precise steering feel, but this transfers all impact forces directly to the servo. If you run a solid horn, invest in a high quality servo that can handle the abuse.
We covered similar servo upgrade considerations in our Grom ESC and servo upgrade guide, though the Grom uses a micro servo rather than the standard size in the Mojave.
Common Battery Related Problems and Solutions
Voltage sag during acceleration indicates your battery can’t deliver current fast enough. Solutions include upgrading to higher C rated packs, ensuring tight connector contacts, and checking for damaged cells. Use a cell checker to verify all cells in your pack are balanced and healthy.
Shortened run times beyond normal capacity loss suggest cell degradation. LiPo batteries typically last 200 to 300 charge cycles before noticeable capacity loss. If your packs are relatively new but showing reduced capacity, check for puffing. Any visible swelling of the battery case indicates internal damage, and the pack should be retired immediately.
Connector heat during or after driving points to resistance in the connection. Clean your connectors with electrical contact cleaner and inspect for damage. Burnt or discolored connectors should be replaced. Always ensure connectors are fully seated before driving.
ESC cutouts during driving can stem from several battery issues. Low voltage cutoff triggers when cell voltage drops below safe levels, usually around 3.3V per cell. This protects your batteries from over-discharge damage. If you’re hitting cutoff frequently, either your batteries are depleted, damaged, or undersized for your driving style.
The Spektrum Firma ESC allows adjustment of the low voltage cutoff threshold through the programming button or Spektrum app. Lowering this threshold gives you more run time but risks damaging your batteries. We recommend keeping the stock cutoff setting and simply charging more frequently or carrying spare packs.
Charger errors during balance charging often indicate a damaged cell. Most chargers will display an error code when one cell won’t balance with the others. If you see this repeatedly with the same pack, that battery has likely reached end of life. Continuing to use it risks fire or further damage.
For more on battery and charger troubleshooting across the ARRMA lineup, check our comprehensive battery compatibility guide covering the Typhon, Granite, Grom, and Mojave.
Buying Guide: Batteries, Chargers, and Upgrades for 2026
The battery market in 2026 offers more options than ever, with prices stabilizing after the supply chain issues of previous years. Budget 6S setups (two 3S packs plus charger) start around $150. Mid-range setups with name brand batteries and a capable charger run $250 to $350. Premium setups with Spektrum Smart batteries and matching chargers can exceed $500.
For most Mojave owners, the mid-range tier offers the best value. Brands like Gens Ace, Zeee, and CNHL provide reliable performance at reasonable prices. Their 100C rated 5000mAh 3S packs typically cost $40 to $60 each. Paired with a dual channel 200W charger in the $80 to $120 range, you’re set for years of bashing.
The Spektrum Smart ecosystem adds convenience features like automatic charge rate detection, capacity tracking, and remaining charge estimation. These features require both Smart batteries and a Smart charger to work. The premium is significant, roughly double the cost of comparable non-Smart setups, but some owners find the convenience worth it.
When buying batteries, purchase at least two sets so you can rotate while one charges. The Mojave runs through a 5000mAh pack in 15 to 25 minutes depending on driving style. Having four total 3S packs (two sets) gives you roughly 45 minutes of driving before you need to wait for charging.
→ ARRMA Mojave 6S, If you’re still shopping for the truck itself, the 2026 RTR version includes everything except batteries and charger, letting you choose your preferred power setup from the start.
For diff oil, purchase a variety pack with multiple viscosities. Team Associated, TLR, and Mugen all offer quality silicone diff oils. A set covering 5000cst through 30000cst costs around $25 to $40 and will last through many oil changes. Avoid non-silicone oils as they can damage the diff seals and o-rings.
Servo upgrades range from $30 budget options to $150 premium brushless units. For the Mojave, we recommend spending at least $50 to $70 on a proven metal gear servo from Savox, Hitec, or ProTek. The stock servo is the most common failure point on this truck, and a quality replacement pays for itself in avoided frustration.
Frequently Asked Questions
Can I run 4S batteries in the ARRMA Mojave 6S?
Yes, the Spektrum Firma 150A ESC supports 4S through 6S operation. Running 4S reduces top speed and acceleration significantly but works fine mechanically. Expect roughly 30% less speed and noticeably softer power delivery. Some owners prefer 4S for smaller spaces or when learning the truck.
What happens if I use batteries with EC5 connectors instead of IC5?
EC5 connectors will physically fit IC5 sockets but the connection is slightly loose. This causes increased resistance and heat buildup during high current draws. Short term use is unlikely to cause problems, but repeated use can damage both the battery and ESC connectors over time.
How long do LiPo batteries last in the Mojave 6S?
Quality LiPo packs typically last 200 to 300 charge cycles before noticeable capacity loss. With proper storage at 3.8V per cell and avoiding over-discharge, many owners get 2 to 3 years of regular use. Puffing, reduced capacity, or balance issues indicate end of life.
What diff oil weight should I use for sand and dunes?
For loose sand and dune running, thicken the rear diff to 10000-15000cst to improve traction and prevent one-wheel burnouts. Keep the front around 5000-7000cst for steering response. The center diff can remain at stock thickness or slightly thicker for predictable power delivery.
Can I charge both 3S packs at the same time?
Yes, with a dual channel charger. Each pack connects to a separate channel and charges independently with proper balance monitoring. This cuts charge time in half compared to sequential charging. Ensure your charger supports dual 3S operation and has adequate total wattage.
Why does my Mojave lose power during hard acceleration?
Power loss during acceleration typically indicates voltage sag from inadequate battery discharge capability. Your pack’s C rating may be too low, the cells may be degraded, or the connectors may have high resistance. Try higher C rated batteries, check connector condition, and verify cell health with a checker.
Do I need to break in new diff oil?
Silicone diff oil doesn’t require break-in, but the diff itself may feel slightly different for the first few runs as the oil distributes evenly through the gears. Run a few packs at moderate intensity before judging the final feel. Avoid extreme driving immediately after an oil change.
Final Verdict
Getting ARRMA Mojave 6S battery compatibility right isn’t complicated once you understand the requirements. The truck needs two 3S LiPo packs rated at 100C or higher, measuring no more than 155mm x 47mm x 48mm each, with IC5 connectors or compatible terminations. Capacity of 5000mAh provides a good balance of run time and weight. Higher capacity packs work if they fit the dimensional constraints.
Your charger needs to handle 6S voltage (25.2V) and deliver at least 5 amps per channel for reasonable charge times. Dual channel chargers around 200W total output let you charge both packs simultaneously, cutting your pit time in half. Balance charging is mandatory for safety and battery longevity.
Diff oil tuning lets you optimize the Mojave for your specific terrain. Start with 7000cst front and 10000cst rear for general bashing, then adjust based on how the truck handles. Thicker rear oil improves traction in loose conditions. Thinner front oil sharpens steering response.
The servo is the most common failure point on this truck, and upgrading to a metal gear unit rated at 25kg-cm or higher prevents the frustration of stripped gears mid-session. Budget $50 to $70 for a reliable replacement that will outlast the stock unit many times over.
Total investment for a complete battery and charger setup runs $150 to $350 depending on brand preferences. Add another $50 to $100 for diff oils and a servo upgrade, and you’ve got a Mojave that’s ready for serious desert bashing without the common reliability issues that plague stock configurations. The upfront cost pays for itself in reduced frustration and more time actually driving instead of troubleshooting.
Affiliate Disclosure: This post contains affiliate links, including Amazon links. If you purchase through these links, we may earn a small commission at no additional cost to you. As an Amazon Associate, Arrma Cars Reviews earns from qualifying purchases.
