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- See also: 12V Basics | 12V Wire & Cabling
- Case Studies: 12V power cut-outs | Battery not charging
On a recent trip up the coast our water pump started playing up, and one occasion shut down completely. While I was in the shower!
It didn’t take long to realise that it wasn’t only the water pump that had shut down, but also the fridge and LED lights. Which made the search for the culprit a bit wider than focusing on the water pump itself.
Our fridge, lights and pump all run through a DC distribution panel which also includes a couple of 12V outlets, a USB outlet, and a voltmeter. And as I discovered – a push button ‘reset switch’. I hadn’t noticed this small button before – it is not labelled – but it was now protruding from the panel. I pushed the button back in and instantly we had lights, the fridge started up and the water pump was again operational.
But the original voltmeter, connected to the distribution panel, was displaying a reading of only 10.1V!
We also have a separate battery monitor, which is connected directly to the batteries through a shunt. This monitor had remained operational when everything connected through the distribution panel had shut down, and it was still displaying a reading of 13.5V from the Lithium batteries. So investigations turned to the distribution panel containing the old voltmeter which was still displaying 10.1 volts. Our fridge, lights, toilet and water pump are all connected through this distribution panel, which contains main switches for each of these appliances.
Hindsight is always a wonderful thing. For a couple of weeks I had noticed a very small discrepancy between the voltage displayed on the old voltmeter and that displayed by the new battery monitor. The old voltmeter, which had previously displayed the same voltage as the new voltmeter, was regularly (though not always) displaying a voltage lower than its more recently installed counterpart. I did wonder about it, but didn’t pursue it any further – everything appeared to be running OK, so worry about it later.
Once the water pump stopped mid-shower, ‘later’ quickly became a more urgent ‘now’! Upon removing four screws and lifting the 12V distribution panel out of its housing, the cause of the appliance shutdown and low voltage issues was immediately obvious – even in amongst the myriad of cables connecting to switches and outlets at the rear of the panel.
One spade connector on the back of the reset switch was loose and had a very ‘corroded’ appearance. Not clean and shiny like it should be, and the plastic insulation on the connector had been damaged by heat. When I removed this connector and its connected cable from the lug on the reset switch, the water pump, lights and fridge all went ‘dead’ – this cable was the main 12V supply line coming in from the batteries.
Fortunately I had a couple of replacement female spade connectors in the spares box, and a crimping tool handy to fit a new connector. Reconnecting the joint with the new connector and a cleaned-up lug brought the system back to life, including the old voltmeter which now displayed a much healthier 13.5 V – the same voltage as displayed on the battery monitor.
What had caused this problem?
I am guessing that the spade connector had become a little loose, or had not been pushed on tightly at the time of installation. This probably resulted in some mini-arcing, which would have caused the connector to heat and deform, further reducing the integrity of the joint – and at worst could have resulted in a fire.
Running the water pump for the shower would have been drawing a constant 6 amps through the faulty joint, causing it to run hot, become less conductive, and drop the voltage further. It is likely that this heat and voltage drop caused the reset circuit breaker to activate.
Fortunately the only damage was to the connector itself – turning it a dirty black, which would have further reduced its connectivity, resulting in increasingly lower voltage throughput, the tripping of the reset circuit breaker, and the subsequent loss of function of the water pump and other connected appliances.
Again, with hindsight, I had also noticed that the fridge didn’t seem to be running as cold as usual for the previous month, which is now understandable if its input voltage had been compromised. (The fridge compressor cuts out at around 11V to protect the battery.)
The point of discussing the above?
First, a low voltage reading may not necessarily be the result of a flat battery. Other factors could be causing the voltmeter to display a low voltage.
Second, I had been going to remove the old voltmeter after installing the new battery monitor. Now I am glad that I didn’t get around to doing that particular job. It is useful having an additional voltmeter connected to the same distribution panel as all the appliances, in addition to the voltmeter connected directly to the battery. This ‘remote’ meter gives a much better indication of the electrical conditions being directly experienced by the various appliances, while the battery monitor continues to provide an accurate indication of the battery condition.
Third, replacing the connector saved me from replacing a water pump – or troubleshooting a fridge, or other apparently ‘faulty’ appliances!
If you are experiencing similar performance or operational issues with any 12V appliances, or an apparently low voltage from an otherwise healthy battery, the first step is to have a good look at the cabling and connectors between the battery, the appliance and the voltmeter. Connectors are a lot cheaper and easier to replace or repair than appliances.
Which brings us to: Fourth – It is worth keeping some spare connectors and a pair of crimping pliers in the spares / tool box!
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- See also: 12V Basics | 12V Wire & Cabling
- Case Studies: 12V power cut-outs | Battery not charging