Running Long Wires to a Linear Actuator: Voltage Drop, Done Right
Here is a familiar troubleshooting story: the actuator runs perfectly on the bench, with short test leads. Installed in the project — at the end of a long wire run to a gate, a hatch, or a lift — it moves slowly, stalls under a load it used to carry, or only works when the load is removed. The actuator did not change. The wire did.
The cause is voltage drop: some of the supply voltage is lost in the wire itself before it ever reaches the actuator. This guide explains why it happens, how to prove it with two voltage measurements, and how to fix it — in the right order.
Why a Long Wire Starves an Actuator
Every wire has resistance, and resistance turns some electrical energy into heat. The longer the wire, the higher its total resistance. When current flows, the voltage lost in the wire follows Ohm's law:
Voltage drop = current × wire resistance
Two consequences follow, and both matter:
- Drop grows with length. Double the wire run and you roughly double the resistance, and therefore the drop — for the same current.
- Drop grows with load. An actuator draws far more current under full load than when moving freely. So the voltage at the actuator falls exactly when the actuator needs it most: under load. That is why a system can look fine unloaded and fail loaded, and why a bench test with short leads proves nothing about a long installed run.
Note the full circuit: current travels out along one wire and back along the other, so both conductors contribute to the total resistance. A "long run" in practice means the total loop, not just one direction.
Diagnose It in Three Steps
You do not need to guess at wire sizes to confirm voltage drop. Two measurements under load settle it. Use a multimeter, and take both readings while the actuator is actually driving its normal load — a no-load reading hides the problem.
Step 1: Measure at the power supply, under load.
Read the voltage at the supply output terminals while the actuator runs. This is what the supply is actually delivering. If this number is already low, the problem is the supply, not the wire — see what power supply you need.
Step 2: Measure at the actuator, under load.
Read the voltage at the actuator's own terminals (or as close to them as you can reach) while it runs under the same load. This is what the actuator actually receives.
Step 3: Subtract, and check the connections first.
Supply voltage minus actuator voltage is the drop in the wire run and its connections. Before blaming the wire itself, check the joints: a loose, corroded, or poorly crimped connector adds resistance exactly like extra wire, and it is far cheaper to fix. If the connections are clean and tight and a large drop remains, the wire run is the problem.
| Symptom | Most likely cause | Check first |
|---|---|---|
| Slow or weak only when installed, fine on the bench | Voltage drop in the long run | Steps 1–3 above |
| Slow or weak everywhere, including the bench | Undersized power supply or a fault | Supply output under load, then troubleshooting checklist |
| Intermittent: works, then stalls, then works | Loose or corroded connection | Every joint in the run, under load |
| One direction weak, the other fine | Mechanical or control fault, not wire drop | Linkage, mounting geometry, and switch/remote — wire drop affects both directions |
The Numbers That Decide the Drop: Full-Load Current
Because drop equals current times resistance, the current that matters is the full-load current — the current the actuator draws when working hardest — not the much lower current it draws moving freely. These are HyHaven's verified full-load currents:
| Model | Force | Full-load current, 12V | Full-load current, 24V |
|---|---|---|---|
| U5 | 500N | 3.0 A | 2.8 A |
| U1 | 900N | 3.0 A | 1.8 A |
| U2 | 1500N | 3.8 A | 2.0 A |
| U11 | 3500N | 6.0 A | 3.0 A |
| U3 | 6000N | 8.5 A | 3.8 A |
| U6 | 7000N | 16.0 A | 9.0 A |
| 508 | 12000N | 20 A | 10.5 A |
Two lessons fall out of this table. First, a bigger actuator needs a much more careful wire run: a 508 at 12V draws about seven times the current of a U1, so the same wire loses about seven times the voltage. Second, a 24V system draws roughly half the current of the same job at 12V, which roughly halves the drop — one more reason to match the supply voltage to the system you already have, as 12V vs 24V and powering from a battery discuss.
A worked example makes the scale concrete. This is an illustrative calculation, not a wire specification: suppose you measure a total loop resistance of 0.5 ohms, and the actuator draws 8.5 A at full load (a U3 at 12V). The drop is 8.5 × 0.5 = 4.25 V, so a 12 V supply delivers only about 7.75 V at the actuator. No wonder it stalls. The fix is not a stronger actuator — it is less resistance between supply and actuator.
Fixing It, in the Right Order
1. Shorten the run, or move the supply closer.
This is the most effective fix and often the cheapest. Every metre removed removes resistance. If the supply can live near the actuator — with mains or battery feed running the long distance instead of the low-voltage actuator feed — do that. Long mains or battery runs have their own rules, but the low-voltage, high-current leg is the one that hurts most.
2. Use thicker wire, then re-measure.
Thicker wire (larger cross-section) has lower resistance per metre. Step up the wire size, remake the connections properly, and repeat the two measurements under load. Do not rely on a generic wire-size chart alone: insulation type, temperature, and how the wire is routed all affect what a given size can safely carry, so the measurement after the change is the proof, not the chart. Keep stepping up and re-measuring until the actuator-end voltage under full load is close to the supply voltage.
3. Clean and tighten every connection.
Treat connectors as part of the wire. Strip back to bright metal, crimp or terminate properly, and protect outdoor joints from moisture. A single green, corroded joint can undo an otherwise perfect wire run.
4. Check the supply can still deliver.
A longer or thicker wire run does not fix an undersized supply. Confirm the supply's rated current covers the actuator's full-load current from the table above, with margin, before declaring the job done. For multi-actuator or battery systems, size for the combined load — see what power supply you need.
Three Things Not to Do
- Do not just turn up the voltage to compensate. Raising the supply above the actuator's rated voltage to "make up" the drop overdrives the actuator whenever the load lightens and the drop shrinks. Match the rated voltage, and fix the resistance instead.
- Do not open or modify the controller to chase the problem. If the controller or remote kit is suspected, test with the standard wiring first and work through how to wire a linear actuator and the troubleshooting checklist. Internal modifications are not a field fix.
- Do not ignore a hot wire. A wire or connector that gets noticeably warm under load is dissipating real power as heat. Stop, find the high-resistance point, and fix it — heat is both a symptom and a fire risk, not something to work around.
FAQ
How much voltage drop is acceptable?
There is no single universal percentage that fits every actuator and job, so this guide does not invent one. The practical test is performance: under full load, the voltage at the actuator should be close enough to the supply voltage that the actuator runs at its normal speed and carries its normal load without stalling. If it does not, the drop is too much, whatever the number.
Will thicker wire make my actuator faster than its rating?
No. Thicker wire only restores the voltage the actuator was supposed to receive. It cannot push an actuator beyond its rated speed or force — and it should not. If the actuator is still too slow after the voltage is restored, the answer is a different speed or force selection, not more copper. See how fast should a linear actuator move.
Is the wire run also a problem for battery systems?
Yes, and often more so, because battery systems are usually 12V, where currents — and therefore drops — are highest. Keep battery-to-actuator runs as short as practical, and read powering a linear actuator from a battery for the battery-side sizing.
Can voltage drop damage the actuator?
Running chronically under-voltage under load causes stalling, overheating, and repeated limit-switch or overload stress, which shorten service life. It is not a benign "a bit slow" condition. If an installed actuator is slow and weak, diagnose it promptly rather than living with it.
My actuator works in one direction only. Is that voltage drop?
Almost certainly not. Voltage drop affects both directions roughly equally. One-direction failure points at the switch, remote, wiring polarity, or a mechanical fault — work through the troubleshooting checklist instead.
Where to Go Next
Voltage drop is the last link in the power chain: supply, wire, controller, actuator. Get the supply right with what power supply you need, the wiring right with how to wire a linear actuator, and the control right with our linear actuator controllers and remote kits. The full decision path is on our linear actuator selection guide.