Sargent EC100 Series Systems

Whether you can depends on which type of Sargent PSU system you have - manual-charging or CAN-bus based.

On systems that only charge manually - PSU2007 with EC200, EC328, EC325, EC225 with EC100, EC176 with EC361/2/3, and EC155 with EC50/51 - the leisure battery is charged by default: with the control panel switched off, the mains charger starts charging the leisure battery the moment it's plugged in, and with the panel on, it keeps the leisure battery topped up while also powering the leisure loads. To charge the vehicle battery instead, switch the control panel on and pick the vehicle battery - the charger then charges that battery along with any leisure loads left switched on. Note that EC100, EC200, EC325 and EC50/51 panels won't allow the vehicle battery to be selected below 10.9V, while EC328 panels (software V2.21) will allow it above 2V provided the mains charger is on. If mains power is lost while charging the vehicle battery, leisure loads will start drawing from it instead - switching back to the leisure battery once the vehicle battery either falls below the 10.9V cut-off or, if it started above that, once it recovers back up to 10.9V. The leisure battery itself has its own 9V cut-off that disconnects leisure loads to stop it discharging further.

CAN-bus systems (the EC800, EC700, EC600, EC500, EC450 and EC400) include a smart-charge feature instead, on by default but switchable off. With the mains charger on, it defaults to charging the leisure battery while keeping an eye on the vehicle battery - if that drops below 12.4V, charging switches to it for 4 hours, then returns to the leisure battery for another 4 hours, repeating the cycle for as long as the vehicle battery stays low. This runs regardless of whether the control panel is on, as long as the system's own shutdown button is switched in (unless you've disabled the feature) - and if the panel is on, you can manually pick whichever battery you want charged at any point in the cycle.

On newer panels with blue LEDs, seeing the Leisure select & levels and Vehicle select & levels LEDs both flashing while you drive is completely normal - it just means the EC155 is picking up the engine run signal, so its internal split-charge relay has engaged. On older panels with green LEDs, the same thing is shown by the middle yellow LED flashing instead.

Either way, once the EC155 detects that engine run signal, it also switches off the 12V supply to the living area.

Turn off the van's 12V supply, then go to the screen showing the manufacturer's logo (e.g. Autotrail) and press the Up and Down arrows at the same time to enter programming mode, then navigate to (a) Battery Size - set to the right capacity - and (b) AH Start Point - which should be your battery's estimated charge, i.e. 100% if fully charged - using Select (<) to adjust each. Scroll to 'Exit Advanced' and press Select to leave.

Most Sargent systems use a PX300 or PF200 battery charger. If yours has a different charger fitted, check with that charger's own manufacturer for Lithium compatibility. The PX300's charging profile suits many leisure-industry Lithium batteries that have their own internal Battery Management System (BMS) - its charging profile and voltages are available as a downloadable attachment on the PX300's own product page, though you'll still need to confirm suitability directly with your chosen battery's manufacturer.

Systems that use a PX300 include the EC800, EC700, EC600, EC500, EC400 series, EC400+ and EC328. If your system doesn't have a PX300, its charger will run a fixed 13.8V, which generally isn't suitable for fully charging a Lithium battery - and switching to Lithium may also mean you need a DC-DC charger to keep the charging current within limits.

On an Auto-Trail, adding an extra leisure battery is normally simple - every current model and most older ones already have a dedicated connector, so the extra battery harness just plugs in.

Ideally pick a second battery of the same make, type and capacity as the one you have. If that's not possible, at least keep the capacity the same and never mix battery types (for example, don't pair a 'wet' battery with an AGM one).

Sargent sells the harness through its web shop (https://sargentltd.co.uk/shop/product/auto_trail_additional_battery_harness_2011-2016/229). It's the newer type, fitted to Auto-Trail vans from 2011, but it suits older vans too because the battery connector hasn't changed.

To fit it:

1. Connect the harness to the new battery, making sure both terminals are tight and their covers are back on.
2. Secure the battery in its box or compartment (this varies by year and model) without trapping the harness.
3. Take the protective cap off the vehicle's spare battery connector.
4. Plug the new battery in.

With an EC328 or EC700 system, that's it - the extra battery is ready to charge and use.

With an EC500 and the EC480 colour LCD panel, also set the battery size to the new total in the advanced settings (two 100Ah batteries means 200Ah), then recalibrate the current sensor.

To change the battery size:

1. On the home screen showing the brand logo, press both the up and down arrows at once and keep them pressed.
2. Let go once the screen changes.
3. Scroll to 'Battery Size' and use select to raise it to the new total.
4. Go back up to 'Exit Advanced', then press select to return to normal use.

Don't worry if the Ah reading drops afterwards - it takes a few charge and discharge cycles to line up with the real capacity, which is normal.

To recalibrate the current sensor:

1. Turn the charger off, and switch the control panel off at its power button.
2. Go to the active battery screen.
3. Hold select until 'calibrating please wait….' appears.
4. Let go - calibration is done.

We don't endorse any particular make or model, but the PX300 charger (fitted across the EC400/EC400+, EC500, EC600, EC700, EC800 and EC328 systems) suits the great majority of good-quality AGM batteries sold in the UK. Its charge profile is included in the instruction manual attached to its product page - if you're at all unsure whether a battery is compatible, check with that battery's own distributor or manufacturer first.

How much solar you can add through the PSU comes down to the fuse protecting that circuit, which varies by system - the maximum recommended wattage through the PSU is 120W for EC325/EC328/EC500/EC600, 80W for EC400, and 150W for EC700/EC800/EC400+. You can go beyond that by wiring extra panels straight onto the leisure battery via their own regulator and a correctly-sized fuse, though you'll lose the ability to see that extra solar's output on the control panel.

Any system without a PSU solar input at all needs its solar wired directly onto the leisure battery this way regardless - and there's no upper wattage limit when connecting straight to the battery like this.