Regulated Power Supply

If your van has batteries I would be checking them first as 8V doesn't sound good.

I think that what HKB Electronics means is that your batteries may be getting low, and when you hook the 240 V in, they are sucking the charge initially. As they get a bit of charge into them the voltage will then come up. Before you plug the 240V in, check the battery voltage and see if it is 8 V.

If a battery gets down to 8v it is usually stuffed or the low voltage has made it so.
The charger is most likely a switchmode powersupply and if used for the last 12 years it may have one or more faulty electrolytic capacitors on it's circuit.

Having all of them replaced by a competent person may fix the charge situation, but the cost of labour and parts possibly means a new charger is the way to go for continued reliable life and good charging.

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Hi Peter,

I was able to find a number of references online about the Hybralec S220A power supply. All these references were regarding failed Hybralec's and no links to supply of these devices. From what I could glean it would seem that they performed as both a 12v power supply and also charged the caravan battery. Some consumers replaced the Hybralec with another 12v power supply. I would guess that your van has been modified to add a separate battery charger and leave the Hybralec to supply the lights when 240v is available but that the Hybralec has now failed.

If the Hybralec has failed (likely) then you have the options to replace it with an equivalent or re-arrange your wiring so that the lights are always fed from the battery and the existing charger supports the lighting load. You may need proficient assistance to achieve this.