My batteries are dead every morning. What is drawing them down?

Some draw is normal — propane and carbon-monoxide detectors, control boards and memory circuits never fully switch off. The question is how much. Measuring actual current with everything switched off separates expected standby consumption from a genuine fault, and it is quick to do. Inverters left in standby are a frequent surprise.

Can I just drop lithium batteries in place of my lead-acid ones?

Sometimes, but it is rarely only a battery swap. Lithium needs a charging profile lead-acid converters do not provide, and it can accept far higher charge current, which can expose undersized cabling and fusing. Done without addressing the charger, it usually results in a bank that never fully charges — or a system stressed beyond its wiring.

Why did my lithium battery stop working in cold weather?

Most likely its battery management system inhibited charging to protect the cells, which is correct behaviour rather than a fault. Charging lithium iron phosphate below freezing causes permanent damage, so the system refuses. Cold-weather use generally requires either heated batteries or keeping them above freezing.

Battery voltage reads 12.6V but nothing works properly. How?

Resting voltage tells you the surface state, not the capacity. A battery with badly degraded plates can show a normal resting voltage and then collapse the moment a real load is applied. That gap is exactly what load testing measures, and it is why a voltmeter reading alone should not be used to clear a battery.

Repair guide

RV battery and charging repair

Whether the battery, the charger, or something drawing on it is the problem.

The three-way split between capacity, charging, and draw — and the lithium cold-charge limit, which is a real hazard that produces silent, permanent damage and is absent from most general battery advice.

What brings owners here

Batteries are flat by morning with nothing obviously running
They never reach full charge even on shore power
Voltage looks fine at rest but everything misbehaves under load
New batteries failed within a season
The system worked all summer and stopped working in cold weather

What to observe and write down

These are observations, not repairs. Each one narrows the problem before anybody charges you for time.

01
Record battery chemistry and age
Flooded lead-acid, AGM, and lithium iron phosphate behave completely differently and need different charging profiles. Chemistry plus install date explains a large share of "bad battery" reports, and a mismatch between chemistry and charger is a very common root cause.
02
Take voltage at rest, then under load
Read after several hours with no charging or load, then again with a real load running. A battery that reads acceptably at rest and collapses under load has lost capacity, which resting voltage alone will never reveal.
03
List everything that stays live with the coach "off"
Propane and carbon-monoxide detectors, radio memory, control boards, antenna boosters and inverters in standby all draw continuously. Together they explain many overnight drains, and a battery disconnect switch does not always isolate all of them.
04
Note the temperature if the problem is seasonal
Lead-acid capacity falls in the cold. Lithium iron phosphate is different and more serious: charging below freezing damages the cells, which is why compatible systems block charging at low temperature. A "stopped working when it got cold" report is a strong signal on a lithium bank.
05
Check the terminals and grounds for corrosion and tightness
A poor connection produces every symptom of a failed battery and a failed charger simultaneously. It is visible, it is free to check, and it is found far more often than owners expect.

How a technician works through it

Knowing the order matters: it tells you whether a quote skipped a step, and it tells you what a technician still has to establish before anyone can say what is wrong.

01
Load-test the bank rather than reading voltage
Capacity is measured under load because resting voltage does not reveal it. This determines whether the battery is actually the problem before anything is replaced.
02
Verify the charger output and its profile
A converter set for the wrong chemistry either undercharges or overcharges, and both destroy batteries over a season. The output voltage is checked against what that chemistry requires, not against a generic figure.
03
Measure parasitic draw with everything switched off
Actual current is measured rather than estimated. This distinguishes normal standby consumption from a genuine fault, and it is the only way to find an unexpected load.
04
Check connections, cable sizing and grounds under load
Voltage drop across an undersized or corroded connection appears as poor charging and poor performance at the same time, and it is measured with current flowing rather than at rest.

What drives the cost

We publish no dollar figures anywhere on this site, because real prices vary by market, season, and technician, and a number we invented would look authoritative and help nobody. What is stable is what moves the number.

Chemistry — lithium banks cost substantially more but the diagnosis is often the same work
Whether the converter or inverter-charger has to be replaced to match the battery chemistry
Whether cabling and fusing need upgrading, which is common when converting to lithium
How many batteries are in the bank and whether they must be replaced as a matched set
Whether a monitoring shunt is fitted, which makes future diagnosis far quicker and cheaper

Before you weigh any of that, settle who is paying. Warranty, insurance, or you works through the order that protects a claim — because authorising a repair before you have the answer is what turns a covered failure into one you funded.

Mobile or shop?

Entirely suited to mobile service. Testing, converter and charger work, parasitic-draw hunting, cabling, fusing and full battery replacement are all standard on-site jobs, and a mobile technician can test the system in the state it actually fails in rather than on a bench.

Where this plays out differently

A handful of markets change the advice on this system rather than merely hosting it.

Quartzsite–Yuma, AZ
How to diagnose and prioritise a power fault when there is no pedestal available to isolate the problem.

Common questions

My batteries are dead every morning. What is drawing them down?: Some draw is normal — propane and carbon-monoxide detectors, control boards and memory circuits never fully switch off. The question is how much. Measuring actual current with everything switched off separates expected standby consumption from a genuine fault, and it is quick to do. Inverters left in standby are a frequent surprise.
Can I just drop lithium batteries in place of my lead-acid ones?: Sometimes, but it is rarely only a battery swap. Lithium needs a charging profile lead-acid converters do not provide, and it can accept far higher charge current, which can expose undersized cabling and fusing. Done without addressing the charger, it usually results in a bank that never fully charges — or a system stressed beyond its wiring.
Why did my lithium battery stop working in cold weather?: Most likely its battery management system inhibited charging to protect the cells, which is correct behaviour rather than a fault. Charging lithium iron phosphate below freezing causes permanent damage, so the system refuses. Cold-weather use generally requires either heated batteries or keeping them above freezing.
Battery voltage reads 12.6V but nothing works properly. How?: Resting voltage tells you the surface state, not the capacity. A battery with badly degraded plates can show a normal resting voltage and then collapse the moment a real load is applied. That gap is exactly what load testing measures, and it is why a voltmeter reading alone should not be used to clear a battery.

Sources for the claims on this page

Charging lithium iron phosphate cells below freezing causes permanent damage, which is why compatible battery management systems inhibit charging at low temperature.
Industry consensusEstablished lithium iron phosphate chemistry limitation; industry-wide consensus
Lead-acid, AGM and lithium chemistries require different charging voltage profiles, so a converter configured for the wrong chemistry shortens battery life.
Industry consensusIndustry-wide consensus across battery and charger manufacturers
Safety detectors and standby electronics draw continuously in most RVs, so some overnight consumption is expected rather than faulty.
Professional judgmentProfessional judgment applied to standard RV electrical layouts

Related systems

Next step

Work through structured triage for this system and you will end up with a written service brief: what you observed, in what order, and what has not been established yet. It is the document that lets a technician quote properly instead of guessing on arrival.

Being straight about what this is. No technician is signed to any territory yet — not one. We do not match you, dispatch anyone, or promise a call. What you get is the brief, and a request form that copies it to us so we know the demand is real. If you need someone today, take the brief and send it to a local technician directly; it works just as well that way.

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