Does an RV MPPT solar charge controller drain the battery at night?
6 min read
Yes, it draws a small amount, because the controller runs off the battery rather than the panels: its display and control electronics need a supply, and after dark that supply can only come from the bank. We do not publish a standby current figure for our MPPT range, so we will not give you a number to multiply by the hours of darkness. The practical question is not whether the draw exists but whether it matters, and for a healthy bank used regularly it does not.
The controller's own supply comes from the battery
It is natural to assume the array powers everything, since the array is what makes the energy. The control electronics are not wired that way. They take their supply from the battery, which is why the published minimum working battery voltage matters at all: below 10.5V on the 20A and 30A models, or 40.5V on the 40A range and above, the unit cannot start, however bright the sun is on the roof.
The same design decision that makes the controller stop working on a flat battery is the one that makes it draw on the battery overnight. There is no separate supply it could switch to.
What we publish, and what we do not
| Question | What our MPPT range publishes |
|---|---|
| The controller is powered from the battery | Yes — published as a minimum working battery voltage per model group |
| Standby or idle current draw | We do not publish a figure for this range |
| The DC load output's own thresholds | Yes — undervoltage shutdown and recovery, per bank voltage |
| Heat dissipation and operating temperature | Fan cooling across the range; −15 °C to 65 °C |
We would rather say plainly that the standby figure is unpublished than estimate it from the size of the unit. If the number matters to your design, ask us with the model you are considering and we will check it against the model rather than the range.
Why the draw usually does not matter
- A healthy bank self-discharges on its own, and the controller's draw is a second, smaller leak on top of it. Over one night neither is a problem.
- The draw is continuous, so the relevant period is not the night but the time the van sits unused. Days are fine; months are a different question.
- A controller sitting below its published minimum working voltage is not holding a low bank down so much as unable to run — the bank has to be charged by other means either way.
- The published DC load output thresholds are what actually stop a forgotten appliance from flattening the bank. They act on the loads, not on the controller's own supply.
Storing the van
For long storage the answer is to take the bank out of the equation rather than to watch it. Note that the controller's battery cable is its own connection to the bank: a switch on the load side, or pulling the fuse from a DC distribution board, will not necessarily take the controller out of circuit, because it is not fed through that path. Whether your arrangement isolates it depends on how the van is wired, so check the actual connection rather than assuming.
Frequently asked questions
- Will an MPPT controller flatten my battery overnight?
- No, not a healthy one. The controller does draw a small supply current from the battery, because it is powered from the battery rather than the array, but over a single night that is a minor leak compared with the self-discharge of a healthy bank. Over months of storage without charging, the cumulative effect is worth managing.
- What is the standby current of your MPPT controller?
- We do not publish a standby current figure for this range, and we will not estimate one from the unit's size. If the number matters for your design, contact us with the model you are considering and we will confirm what applies to that model.
- Does the DC load output protect the battery from the controller's own draw?
- No. The published thresholds on the load output — undervoltage shutdown and recovery — govern the circuit feeding your DC appliances. They do not disconnect the controller's own supply from the battery, which is a separate connection.
- Should I disconnect the controller when storing the van for the winter?
- Taking the bank out of the circuit is the reliable approach for long storage. Purely disconnecting the loads is not the same thing, because the controller's battery connection does not run through the load circuit. Check how your installation is actually wired before deciding what to switch off.
