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The best laid plans….

We had originally intended to spend a week down at Glastonbury which would have meant the 5 hour drive down would have been an excellent test for the Sterling Power Wildside unit’s first outing. However we had to cancel the trip literally the day before we were due to set off. In the few days between installing the Wildside unit and our planned trip to Glastonbury I had been exchanging emails and phone calls with Charles Sterling talking about some of the aspects of the Wildside unit and the direction that caravan electrics was heading in.

Probably the best route was the one that the Australian caravan community seems to have gone down with a DC to DC charger installed in the vehicle and an Anderson plug to connect between the tow vehicle and caravan or trailer. This allows up to 50 or 60 Amps of charging current and gives them the ability to install 300Ah or 400Ah of battery capacity and be certain of charing it . For us to go much above 120Ah capacity with the current 13 pin setup and to charge it effectively we need to be able to improve the charging current available. I suggested that the fridge might not have to be powered up all the time, maybe on a duty cycle and that would mean all the output would be available to charge the leisure battery. This must have got Charles thinking.


Err…. somthing missing here!

A couple of days later I had a phone call from Charles. ” We can reprogram the box to prioritise the battery or the fridge”. Long story short, I uninstalled the Wildside unit (above) and posted it back to Charles at Sterling Power for reprogramming.

So what’s changed?

The absorption fridges fitted in modern caravans although energy efficiency wise are not very good, they are well insulated and that’s the key point here. The fridge does not have to be powered on all the time. If you go on a ferry crossing, your fridge might be powered down for a couple of hours and most fridges cope. Two hours might be a bit long, but powering down for shorter lengths of time is easily achievable without compromising the performance.


Re-installing the Wildside unit and testing again.

The Wildside unit now has two modes:- Battery Bias Mode (default) or Fridge Bias Mode.

Battery Bias Mode initially charges the battery only for the first 15 minutes or until nearly at full charge. The fridge is then powered up. The fridge remains on then indefinitely providing the leisure battery remains at above a certain level. If the leisure battery voltage drops below, the timer starts again and the battery receives all the Wildside’s output for 15 minutes. This 15 minute cycling continues until the Wildside unit has recharged the leisure battery to a point in the charging profile that dosen’t require a high current.

Fridge Bias Mode operates the fridge permanently with the leisure battery receiving the remainder of the available capacity of the Wildside unit.

Switching between the two modes is as simple as holding down two buttons for ten seconds. If you want to read the full details about how it operates you can find it on the Sterling  Power website here

What’s the advantages of Battery Bias Mode?

Looking after the battery is  key feature here. You invest in a good quality battery, you may have invested in a multi-stage smart charger to maintain your battery in the off-season or you may have gone the solar route. However plugging the caravan into to the tow vehicle is the same as putting you battery on charge with a cheap 5 amp charger that puts the same energy into a battery whether it needs it or not.

The Wildside unit is a multi-stage smart charger that just happens to be powered by the tow vehicle. Having the Battery Bias Mode allows the unit to recharge the leisure battery as quickly as possible while maintaining the correct charging profile for the battery chemistry and as far as I know it is the only way you could charge different   battery chemistry types correctly with a tow vehicle if you have chosen to upgrade from the standard sealed lead acid leisure battery.

So what does this mean for us? Well, it now gives us the option to seriously look at going for AGMII batteries and installing a second battery to increase our capacity to around 200Ah. As we don’t carry two big steel gas cylinders we just have the one lightweight refillable Safefill cylinder we do have the spare weight capacity and space (not in the gas locker obviously!) for a second battery.

I’ll let you know how we get on.


Just the cover to put on and the fuse to install and we’re ‘good to go’.