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Straight answers to the questions buyers ask most, written so you can apply them to your own vehicle or project.
How to size an RV solar system
To size an RV solar system, first work out how much energy you actually use in a day by listing each appliance, its power draw and how long it runs.
9 min readCharge ControllersMPPT vs PWM: which solar charge controller should you choose?
MPPT controllers convert surplus panel voltage into additional charging current, so they harvest roughly 10–30% more energy than PWM in cold or partially shaded conditions, and they are the right choice for arrays above about 200W or systems running at 24V and above.
7 min readBatteriesLiFePO4 vs AGM: which battery should you put in an RV?
LiFePO4 is the better choice for most RV installations because you can use about 90% of its rated capacity against roughly 50% for AGM, it lasts several thousand charge cycles rather than a few hundred, and it weighs substantially less for the same usable energy.
8 min readBattery ChargersHow do I charge my RV leisure battery while driving?
The alternator charges the leisure battery while you drive, but how you connect the two decides how quickly and how fully it charges.
6 min readInvertersWhat size inverter do I need for an RV?
Size an inverter around the loads you will actually run at the same time, not around the battery.
7 min readSolar PanelsShould I wire my solar panels in series or parallel?
Series and parallel describe how the panels' outputs are added together.
7 min readBatteriesHow long will a 12V battery run my appliances?
Runtime comes from three numbers: the battery's usable capacity in amp-hours, the load in amps, and how deeply you are willing to discharge.
6 min readAccessoriesWhat size cable and fuse does a 12V system need?
Cable is sized by the current it must carry and by the length of the run, because voltage drop grows with both; the fuse is then sized to protect that cable.
6 min readCharge ControllersWhat size solar charge controller do I need?
A charge controller is sized from two limits on the array: the maximum voltage it can accept and the maximum current it can pass.
6 min readSolar PanelsWhat goes into a complete RV solar system?
A complete RV solar system is a chain of five parts, and each one has to match the next.
7 min readBatteriesShould I build a 12V or a 24V battery bank?
Stay at 12V while the system is small, and step up to 24V as soon as a large inverter enters the plan.
7 min readCharge ControllersHow do I wire an RV solar system?
Connect the battery to the charge controller first and the array to the controller second, and disconnect in the reverse order: array off first, battery last.
8 min readInvertersCan you run an RV air conditioner on solar power?
An air conditioner can be run from a solar system, but it is the largest load most RVs will ever ask of one.
7 min readBatteriesCan I leave my lithium battery in the van over winter?
Yes, with two conditions: nothing may charge it below freezing, and it should go into storage charged rather than flat.
6 min readSolar PanelsDo flexible solar panels last as long as rigid ones?
No, a flexible panel does not last as long as a framed glass one, and it is worth being straightforward about that before comparing prices.
7 min readInvertersPure sine wave or modified sine wave: which inverter does an RV need?
A pure sine wave inverter reproduces the smooth alternating waveform that mains power has, and a modified sine wave inverter approximates it with a blockier, stepped version of the same shape.
7 min readAccessoriesCopper or CCA battery cable: does it matter?
It matters more at 12V than almost anywhere else.
6 min readSolar PanelsHow many solar panels fit on an RV roof?
Work it out from the physical size of the panels and the usable dimensions of the roof, not from a rule of thumb.
7 min readCharge ControllersSolar and the alternator at the same time: how dual input charging works
Two sources can charge the same battery at once, and the reason people usually keep them apart is the behaviour of the alternator rather than the battery.
7 min readSolar PanelsDo solar panels work on cloudy days?
They work, but they produce a fraction of their rated output.
7 min readCharge ControllersWhere should a solar controller or charger be mounted?
In a dry, ventilated space, as close to the battery as the cable run allows.
6 min readBatteriesHow hot is too hot for a lithium battery?
A lithium leisure battery publishes three temperature windows, and the hot end is the tightest of them.
6 min readBattery ChargersWhat voltage should a LiFePO4 leisure battery be charged at?
A 12.8V LiFePO4 battery is charged at 14.40–14.60V.
6 min readSolar PanelsLooking after an RV solar system: what to check and when
A solar system has no moving parts, so looking after it is inspection rather than servicing — and almost everything that goes wrong shows up first as a number that has quietly fallen.
7 min readBatteriesWhat does a lithium battery's voltage tell you?
Less than most people expect.
6 min readAccessoriesBattery terminal and lug sizes: what has to match?
Two dimensions matter, and they are different ones.
6 min readCharge ControllersHow many solar panels can you connect in series?
Work from the panels' open-circuit voltage against the controller's maximum PV voltage, then check the input power limit as well, because on a 12V battery it usually binds first.
7 min readAccessoriesWhich fuse type belongs where in a 12V system?
Fuses come in a handful of physical forms, and the form decides which jobs a fuse can do.
7 min readAccessoriesWhy a DC fuse has a voltage rating
Most people read the amp rating of a fuse and stop there, and the amp rating is only half of it.
7 min readBatteriesHow do you fuse a lithium battery bank?
The main fuse belongs on the battery's positive cable, as close to the terminal as the mounting allows, and it has to satisfy three things rather than one: the current the system will actually draw, the DC voltage of the bank, and the fault current the battery can deliver.
6 min readInvertersWhich appliances should run on 12V and which on the inverter?
Keep an appliance on 12V when it is available as a native DC appliance, and put it on the inverter when it is only made as a mains appliance.
7 min readSolar PanelsCan I add more solar panels or a battery later?
Yes, as long as the parts you choose now have room above them.
7 min readBatteriesHow should the system differ for weekend trips and full-time living?
The difference is not the size of the system but which part has to carry the gap.
7 min readSolar PanelsAre perovskite solar panels ready for a camper van?
Not yet, in the sense that matters to a van build.
7 min readBatteriesWill sodium-ion batteries replace LiFePO4 in a camper van?
Not yet, and the reason is energy density rather than price.
6 min readBatteriesDo you need a self-heating lithium battery for winter camping?
Only if you charge in freezing weather and the battery sits somewhere cold.
6 min readBatteriesAre solid-state batteries coming to camper vans?
Not yet, and the first distinction that matters is semi-solid against all-solid.
6 min readSolar PanelsWhat do TOPCon and HJT cells change in a van panel?
They change the watts available per square metre of roof, and very little else.
6 min readSolar PanelsDo shaded panels on a van roof need DC optimisers?
Only if the shade is persistent and you cannot move what is causing it.
6 min readSolar PanelsCan the van body itself generate solar power?
In principle yes, and the area is certainly there: a van has far more body surface than roof.
6 min readInvertersCan a camper van power a house?
Not the way an electric car can, and the difference is the direction of the power.
6 min readBatteriesWhat does a smart BMS add to a van battery?
It changes what you know, not what the battery can do.
6 min readInvertersWhat is the difference between an RV inverter and a converter?
They work in opposite directions.
6 min readInvertersWhy is my RV inverter beeping or giving no output?
On most RV inverters a beep or a shutdown is a message about the DC side rather than a fault inside the inverter: the battery voltage has fallen, the current being asked for is too high, or the unit has overheated.
7 min readInvertersHow do you install an RV inverter?
The order that works is: choose the location, mount the unit, run and fuse the DC cables, connect the AC output, then commission it with a small load before the real one.
8 min readBatteriesWhat battery bank does an RV inverter need?
Size the bank around two numbers: the DC current the inverter will draw, and how long you want that load to run.
7 min readInvertersDoes an RV inverter need a transfer switch?
It does if you want the same sockets to work from either source without moving plugs.
6 min readInvertersWhere should you mount an RV inverter?
As close to the battery as the layout allows, and somewhere with moving air.
6 min readInvertersDoes an RV inverter drain the battery when it is switched off?
Yes, in one specific sense: an inverter that is switched on keeps drawing current for its own control electronics, display and protection circuits even when nothing is plugged into it, and that standing draw is what flattens a battery over days rather than hours.
6 min readInvertersDoes an RV inverter need to be earthed?
Two separate jobs, and both matter.
6 min readInvertersRV inverter or a generator: which should you choose?
They are two ways of solving the same problem.
6 min readInvertersLow-frequency or high-frequency RV inverter: does it matter?
There are two ways to build an inverter and the difference shows before you connect anything.
6 min readBattery ChargersDo you need an RV inverter with a built-in charger?
It depends on what is already in the van.
6 min readInvertersDoes an RV inverter output 110V or 220V?
It is one or the other, decided when the unit is built.
6 min readInvertersHow much surge power does an RV inverter need to start a motor?
An RV inverter carries two ratings rather than one: a continuous figure for loads that run, and a peak figure for the instant a motor or compressor starts.
6 min readInvertersCan you run an RV inverter while driving?
Yes.
6 min readInvertersWhy does an RV inverter interfere with the radio or the TV?
Because an inverter switches thousands of times a second, and every switching edge is a small radio transmitter if the wiring gives it an antenna.
7 min readInvertersCan you run an RV inverter straight from solar panels?
No.
6 min readInvertersHow do you test an RV inverter before you rely on it?
Test an RV inverter in four steps: verify the DC polarity and voltage at the terminals, power it up with nothing connected and meter the AC output, run a known resistive load, then run the real load while watching the DC voltage.
6 min readInvertersWhat do CE, FCC and RoHS on an RV inverter actually cover?
CE, FCC and RoHS on an RV inverter are declarations about conformity and materials, not about performance.
6 min readInvertersShould you buy an RV inverter or a portable power station?
They decide different questions.
7 min readInvertersCan you run two RV inverters together?
Not as one bigger supply.
6 min readInvertersCan an RV inverter charge a laptop or a phone?
Yes, and there are two routes.
6 min readBattery ChargersDoes a DC charger need MPPT?
Only on the solar side.
6 min readBattery ChargersHow do you install a DC charger in a campervan?
Mount the charger close to the leisure battery on a solid, dry surface, put the fuse at the starter-battery end of the input cable rather than at the charger, connect the control wire that lets it run only with the engine, and check the polarity before the first switch-on.
7 min readBattery ChargersDoes a DC charger work with a smart alternator?
Yes, and it is the case a DC charger is built for.
6 min readBattery ChargersWhy is my DC charger not charging?
Work through the conditions the charger publishes before assuming it has failed: no control signal from the engine, a blown or loose fuse on the input, an input voltage below the cut-off, a panel voltage that has not risen far enough above the battery, a hot unit derating its output, or a battery that is simply full.
7 min readBattery ChargersIs a DC charger the same as a solar charge controller?
No, though they do the same job.
6 min readBattery ChargersCan a DC charger charge a caravan battery from the tow vehicle?
Yes, and the charger belongs in the caravan rather than in the car, so that the output run to the leisure battery stays short and the long run carries the input instead.
6 min readBattery ChargersDoes a DC charger charge the starter battery too?
On our dual-input models, yes.
6 min readBattery ChargersDoes a DC charger draw power when the engine is off?
Very little, and it should not be charging at all.
6 min readBattery ChargersDoes a DC charger need cooling?
It needs somewhere to put its losses, because that is what the wattage it does not pass on becomes.
6 min readBattery ChargersCan you monitor a DC charger from your phone?
On the DD range, yes.
6 min readBattery ChargersHow do you wire the ignition signal on a DC charger?
It is a small signal wire from an ignition-switched source to the charger's control input, and it exists so that the charger only charges with the engine running.
6 min readBattery ChargersDo you need a bigger alternator for a DC charger?
Not always, and the comparison is straightforward once both sides are known.
6 min readCharge ControllersWhat is the load output on an RV MPPT solar charge controller?
It is a second set of output terminals, separate from the battery, that feed DC loads or a distribution board directly from the controller.
6 min readCharge ControllersWhy is my RV MPPT solar charge controller not charging?
Check what the controller is being given before suspecting the controller.
7 min readCharge ControllersCan an RV MPPT solar charge controller work with 12V, 24V, 48V and 96V banks?
Across the family, yes, and each model is published for particular bank voltages rather than for all of them: 12V and 24V on the 20A and 30A models, 48V on the 40A and 60A models, and 96V on the 80A and 100A models.
6 min readCharge ControllersCan an RV MPPT solar charge controller charge a lithium battery?
Yes.
6 min readCharge ControllersCan you use a portable solar panel with an RV MPPT solar charge controller?
Yes, provided the portable panel does not have a charge controller of its own built in.
6 min readCharge ControllersDoes an RV MPPT solar charge controller work in winter?
The controller is rarely the winter problem.
6 min readCharge ControllersWhat does the amp rating on an RV MPPT solar charge controller actually mean?
It is the maximum charging current the controller will deliver to the battery, not the current arriving from the solar panels.
5 min readCharge ControllersShould you use 12V or 24V solar panels with an RV MPPT solar charge controller?
With an MPPT controller the panel's nominal voltage does not have to match the battery's, so a 12V battery can be charged from panels whose label says 24V or higher.
5 min readCharge ControllersDoes an RV MPPT solar charge controller need a fan?
Ours are fan cooled across the whole range, from the 20A model to the 100A model.
4 min readCharge ControllersCan you run two RV MPPT solar charge controllers on one battery bank?
Two controllers can both be connected to one battery bank; each charges it independently using its own profile.
5 min readCharge ControllersWhat are the charging stages on an RV MPPT solar charge controller?
Our range publishes three charging stages: fast, absorption and float.
5 min readCharge ControllersWhy does an RV MPPT solar charge controller stop working when the battery is flat?
Because the controller is powered from the battery, not from the solar array.
5 min readCharge ControllersDoes an RV MPPT solar charge controller drain the battery at night?
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.
6 min readCharge ControllersWill an RV MPPT solar charge controller charge the starter battery?
Not as a second charging output, because our MPPT range does not publish one.
5 min readCharge ControllersDoes an RV MPPT solar charge controller equalise a lead-acid battery?
Not as a published stage.
6 min readCharge ControllersCan you monitor an RV MPPT solar charge controller remotely?
Locally, yes; remotely, not on this range.
6 min readCharge ControllersWhy is my RV MPPT solar charge controller charging below the target voltage?
Because the controller regulates the voltage at its own terminals, not at the battery posts.
6 min readCharge ControllersHow much of my solar array's output reaches the battery on an RV MPPT solar charge controller?
Two published figures describe it, and they are not the same figure.
6 min readBattery ChargersWhat size DC DC charger do I need for a leisure battery?
Work from the battery rather than from the vehicle.
7 min readBattery ChargersIs a DC DC charger better than a split charge relay?
They do different jobs.
7 min readBattery ChargersWhat cable size does a DC DC charger need?
There is no single size, because the answer depends on your run length and your charge current rather than on the charger.
6 min readBattery ChargersHow long does a DC DC charger take to charge a leisure battery?
Divide the amp-hours you need to replace by the charge current, and you have the optimistic answer: a 60A charger puts back 60 amp-hours in an hour, on a battery willing to accept it.
6 min readBattery ChargersCan you run two DC DC chargers in parallel?
Two different arrangements get called parallel, and they have different answers.
6 min readBattery ChargersCan a DC DC charger be used on a 24 V system?
It depends which range.
6 min readBattery ChargersCan you connect solar panels straight to a DC DC charger?
Only if the charger has a solar input of its own, with an MPPT stage behind it.
7 min readBattery ChargersCan one DC DC charger charge two battery banks?
Not as two independent banks.
6 min readBattery ChargersDo you need a new DC DC charger when switching to lithium?
Usually not the charger itself.
7 min readSolar PanelsHow long does an RV solar system last?
There is no single figure, because an RV solar system is four things that age at different rates: the panels, the charge controller, the cabling and connectors, and the battery.
7 min readSolar PanelsMonocrystalline or polycrystalline for an RV solar system?
For a van roof the difference that matters is how much power a given area produces, and monocrystalline cells have the advantage there.
6 min readInvertersCan an RV solar system run a fridge?
Yes.
7 min readInvertersCan an RV solar system run Starlink?
Yes, but the arithmetic is different from an appliance that switches on and off.
7 min readSolar PanelsDoes panel angle matter in an RV solar system?
It does matter, but a van roof rarely allows you much choice.
7 min readSolar PanelsHow should an RV solar system enter the roof?
Through one sealed penetration, not one per panel.
6 min readSolar PanelsHow do you test whether an RV solar system is working?
Measure the panel on its own, then compare with its published figures.
7 min readSolar PanelsWhat causes hot spots in an RV solar system?
A hot spot is a cell that has stopped generating but is still in the circuit, so current from the rest of the string is forced through it and dissipates as heat.
7 min readSolar PanelsCan you fit an RV solar system to a pop-top roof?
Yes, and a raising roof is one of the better cases for flexible panels: ours are 4mm thick and carry no frame, so they add little height and follow a curved surface.
7 min readInvertersCan an RV solar system run a washing machine?
Sometimes, and the deciding factor is almost always whether the machine heats its own water.
7 min readSolar PanelsCan you mix different panels in one RV solar system?
You can, but the wiring decides whether it works.
8 min readSolar PanelsDo flexible panels need an air gap in an RV solar system?
There is no single answer, because it depends how the panel is fixed.
7 min readAccessoriesHow do you crimp a battery cable so the joint does not fail?
A crimp is a cold weld.
7 min readAccessoriesBreaker or fuse: which belongs in a 12V system?
Both devices do the same thing in principle: they open the circuit when current goes somewhere it should not.
7 min readAccessoriesHow should a busbar be laid out in a 12V system?
A busbar replaces a stack of ring terminals on one battery stud with a single solid connection point for each polarity.
7 min readAccessoriesWhat should you check before crimping an MC4 connector?
MC4 is a family of connectors rather than a single part, and two connectors that look identical can come from different families that do not seal or latch against each other.
7 min readAccessoriesHow should solar cable be protected along its run?
A cable run fails at three places rather than along its length: where it enters the structure, where it crosses a hard edge, and where it is fastened.
6 min readAccessoriesWhere does a battery monitor's shunt belong?
A shunt is a calibrated resistor, and a battery monitor works out state of charge by counting every amp that passes through it.
6 min readAccessoriesHow should a 12V system be earthed in an RV?
Two systems share the word earth and they do different jobs.
7 min readSolar PanelsHow much does an RV solar system cost?
There is no single figure for an RV solar system, because the same daily energy need can be met at very different totals depending on how many days of battery you carry and how the array is built.
8 min readAccessoriesRV solar system kit, or parts bought separately?
Buy a kit when its sizing already matches your daily energy use and it contains the parts you would have chosen anyway; buy separate parts when you are extending an existing system, working around an unusual roof, or need a rating the kit does not offer.
7 min readBatteriesIs an RV solar system worth it?
An RV solar system is worth it when you would otherwise be paying for hookups, burning fuel in a generator, or idling the engine to charge, and when you spend enough nights off grid for those costs to add up.
8 min readBatteriesHow much power does an RV use in a day?
There is no useful average, because a van's daily consumption depends almost entirely on whether it runs a compressor fridge, an inverter, or air conditioning.
8 min readSolar PanelsHow much does an RV solar system weigh?
The battery is usually the heaviest single item, and the roof array is usually lighter than people expect.
7 min readSolar PanelsPortable solar panel or a fixed roof system?
A fixed roof array needs no attention, charges while you drive and cannot be left behind, but it only ever sees the sun at whatever angle the van happens to be parked.
8 min readBatteriesHow many days can an RV go off grid on solar?
On a sunny day, usable battery capacity divided by daily consumption gives the answer, with the array covering part of the load as it goes.
8 min readAccessoriesCan you install an RV solar system yourself?
Most of a 12 V system is within reach of a careful DIYer: mounting panels, running cable, crimping, fusing and connecting the controller.
9 min readInvertersCan an RV run an induction hob on solar?
An induction hob is a battery and inverter question rather than a panel question, because the energy arrives in a short burst at high power.
8 min readSolar PanelsHow do you choose a solar panel for a camper van?
Choose by working down from consumption rather than up from a panel.
8 min read