Using the Spektrum S150 Charger Without Losing Your Mind
The Spektrum S150 is a basic single-cell LiPo charger aimed at people flying micro helis and small trainers. It handles 3.7V to 4.2V packs at up to 1.5 amps charge current. That is it. Nothing fancy. The manual is mostly diagrams, but there are enough gotchas that I have found myself going back to it repeatedly over the years. You can find the official Spektrum S150 Charger Manual on the Horizon Hobby support site. Search for model SPMB150 and pull the PDF from the documents section. It is free. I still carry a printed copy because the screen reading is slower than flipping to a page when you are troubleshooting a weird error on the bench.
Spektrum S150 Charger Manual breakdown
The charger has four buttons and a small LCD. You select the cell count, set the charge current, pick the termination method, and hit start. The manual walks through each of those steps with screenshots that are barely readable at normal size. Here is what actually matters in practice. The default termination is delta-V. That means the charger watches the battery voltage drop slightly as the cell nears full and cuts off there. This works fine for healthy packs. For aged cells with high internal resistance, the voltage dip can be shallow or nonexistent, and the charger might think the pack is not full yet and keep pushing current until it hits the time limit. When that happens, you get a "cell low" or timeout error. The workaround is switching to timer termination and setting it to about 90 minutes for a 1.5 amp charge. It is not as precise, but it keeps you from leaving the charger running forever hoping it will figure itself out. Another thing the manual does not emphasize enough: the input power requirement. The S150 draws around 18 watts at full charge. That sounds small, but if you are powering it from a car adapter or a cheap wall wart, sagging voltage will trip the charger into fault mode mid-cycle. I burned through two bargain-bin 12V adapters before I switched to a proper 2A output supply. The charger itself will tell you "input low" — it just does not warn you until it is already too late in the charge cycle.
Balancing is not a feature on this unit. That is a design limitation you have to accept. If you are running a 2S pack through the S150, it will charge both cells in series with no balance correction. For most micro packs that stay reasonably matched, this is acceptable. For higher capacity 2S cells that you cycle frequently, you will want to pair the charger with a standalone balancer or move to a more capable unit. Spending $60 on an S150 and then buying a $30 balance board anyway defeats the whole purpose. Connectors are another area where people run into trouble. The S150 comes with an IC6-style charging lead. IC6 is not the same as JST-XH or Deans, and it is not the same as a balanced charging port. Some hobby shops sell IC6 adapters for popular battery types like Nano-Tech or certain Gensace packs. If your battery does not plug in directly, do not force it. I once bent a pin on a sloppy adapter and spent twenty minutes magnifying-glassing the connector to straighten it back out. Cheap adapters are a real pain. The charge current setting deserves a bit more thought than the manual gives it. A 2000 mAh pack at 1.5A is a 0.75C charge, which is gentle and safe. But a 500 mAh pack at the same 1.5A setting is running a 3C charge, which will heat the cell noticeably and shorten cycle life over time. Always calculate C-rate before you press start. The formula is straightforward: charge current in amps divided by capacity in amp-hours. If the result is above 1C for a standard LiPo, consider dropping the charge current or accepting that the cell will run warm.
Get the Full Details
I also want to flag one limitation that the manual mentions only in passing. The S150 does not support storage mode. That means you cannot put a freshly charged pack into a low-voltage sleep state for long-term storage. If you plan to store batteries for more than a few days, you need to manually discharge them to around 3.8V per cell using a resistor load or a dedicated storage charger. Leaving a fully charged LiPo at 4.2V for weeks will degrade capacity faster than you might expect. I learned that the hard way with a batch of 650 mAh packs I left on the bench over winter. They came back at roughly 80% of original capacity with no visible damage. When the charger shows an error code, do not just reset and restart immediately. The S150 logs temperature and voltage faults distinctly. A reverse polarity fault means the leads are connected backwards — check the red and black wires. A cell imbalance fault during charge means one cell is significantly lower than the other before charging begins, which usually indicates a bad cell or a connector issue. The manual has a table for these, but the real fix is often visual inspection of the connector pins and the battery leads, not a settings change. The unit itself is small enough to sit on a workbench without taking up space, and the fan is quiet. It is not built for professional shop use, but for home use with small models it does what it claims. Just read the manual once all the way through before your first charge, calculate your C-rates, and keep a spare charging lead handy since the stock one is on the thin side. Beyond that, it is a simple device that will serve you well if you do not expect it to do things it was never designed to do.
