Standing loads that never announce themselves: an inverter left in standby, a monitor, a tracker, an alarm, a battery management system, a radio memory. Individually each is small; together over a month they empty a bank that was never used.
A battery that was full in October and flat in February was not faulty. Something was awake.
Why small currents matter over long periods
A standing draw is multiplied by the hours it runs, and a winter is a lot of hours. A current too small to notice on any instrument except a clamp meter is enough to take a bank below its cut-off before spring.
The usual culprits
An inverter in standby, which consumes even with nothing plugged in. A battery monitor, a tracker, a gas alarm, a habitation control panel. On a lithium pack, the management system itself. None of these is a fault and all of them add up.
Why it is worse for lithium
A pack taken below its protection threshold disconnects, and many management systems then refuse to accept charge until a specific procedure is followed. A lead-acid battery left flat suffers differently — it sulphates — but neither outcome is recoverable by wishing.
What to do about it
Measure the standing current once, attribute it fuse by fuse, and decide deliberately what stays live. Then isolate the rest, and check the state of charge once during the idle season rather than at the end of it.
Where this page and the manufacturer’s documentation differ, the documentation is the one to follow. Every capacity, output, input window, current limit, cycle count and temperature threshold on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And the distinction this page keeps: a nominal capacity is not the energy that reaches a socket. A reserve the chemistry never gives up, and the cost of converting stored direct current into a mains-style output, both sit between the two. Where a maker publishes a usable figure, this page reports it beside the nominal one; where only the nominal one exists, it says so rather than converting it.
What people ask before they order
How do I find them?
A clamp meter on the main negative with everything supposedly off gives the total in seconds, and pulling one fuse at a time attributes it. A shunt monitor reports the same figure continuously.
Does an isolator solve it?
For everything downstream of it, yes — which is why one is fitted on vehicles and boats that sit unused. Anything that must stay live, such as an alarm, has to be wired around it deliberately.
Last reviewed 16 September 2026