Guest ChrisB Posted September 12, 2011 Posted September 12, 2011 I have a 300W inverter, just under 3 years old. Last trip the red "low battery" light came on when trying to use - even though the van control panel showed 13.4V for the leisure batteries - confirmed by voltage check with a meter at the inverter. The voltage drops to 13.3V when switched on - but 0V (AC) output. The inverter is located next to the batteries (short 12V cable run) and protected by a 30A fuse which is fine. I don't think the unit would be repairable - so I'm asking for suggestions on where to buy a reasonable quality replacement at a fair price (the last one came off Ebay). Nothing sophisticated needed (e.g. sine wave) as it's only normally used for powering cooling fans or spin drier - not sensitive electronic equipment. Chris
Keithl Posted September 12, 2011 Posted September 12, 2011 Hi Chris, I wouldn't just go out and replace it without doing a few more checks first. It sounds very much like you have a loose or dirty connection on the 12v side and as soon as you apply a load the voltage drop across the fault causes the available voltage to fall below the minimum it can operate at. You say you measured the voltage at the inverter with a meter, did you do this with the inverter on or off? If with it off then it proves nothing. Try turning the inverter on then measuring the voltage at every point you can along the wires. And don't forget the fault could be on the Negative OR Positive. HTH, keith.
Guest ChrisB Posted September 12, 2011 Posted September 12, 2011 Keith Thanks for the advice. I checked all of the connections from the batteries to the inverter (only about 50cm of cable) and mde sure all joints were secure. All equipment is internal (under a seat) so not subjected to any road dirt. Just checked the fuse on the inverter and it's OK too. The red light shows on switching on. As i said in the previous post the meter reads around 13.4V at the connections to the inverter. Switch on and the cooling fan operates but the red light (which has indicated a low voltage in the past) comes on. No AC output and the voltage drops by around 0.2V. I'm no expert I readily admit, but it looks to me that the circuit that checks the voltage is falsely indicating a low reading and isolates the inverter?
Brambles Posted September 13, 2011 Posted September 13, 2011 Switch on every 12 volt appliance running off the liesure (same) battery and then measure the voltage. Work out what the 12 volt load is in watts ( e.g 4 x 10 watt lamps + heater fan, + extractor fan etc)and report back . It may be fine for small loads but not the start up spike the invertor needs. How to get round this for testing. Start the engine so liesure battery is charging, then try the invertor with no load. If it powers up then, stop the engine see if it remains powered up. Now apply a small load to the 240v output like a 60 watt lamp and increase the load, ( a 100 watt lamp!) until it fails and each time measure the battery voltage. However the fact it powers up with engine running almost proves the liesure battery has high internal resistance and just cannot supply the high spikes of current needed.
Guest ChrisB Posted September 13, 2011 Posted September 13, 2011 Brambles - 2011-09-13 1:45 PM Start the engine so liesure battery is charging, then try the invertor with no load. If it powers up then, stop the engine see if it remains powered up. Now apply a small load to the 240v output like a 60 watt lamp and increase the load, ( a 100 watt lamp!) until it fails and each time measure the battery voltage. However the fact it powers up with engine running almost proves the liesure battery has high internal resistance and just cannot supply the high spikes of current needed. Brambles Thanks for your advice - I know from your previous posts that you are the resident expert in these matters. My problem is that with the leisure battery fully charged (and the 'van on mains hookup) the inverter refuses to give any 240V output whether or not a load is attached. It has been working fine in its current location for a couple of years but failed this summer. I'm sure it's not worth repairing so I was hoping that someone might recommend a suitable model for replacement.. A Maplins has opened up near us recently - will give them a try (their website is slow/down at the moment).
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