A rattling sound

This morning I decided to do one of my routine checks of the engine and associated components.  However this time I had the engine compartment board up and the engine exposed whilst I started it.  There was an obvious rattle coming from the engine and I couldn’t find the source so I went and asked Nick, the engineer.  He listened to it and quickly identified the source as a loose alternator belt.  He checked both alternator belts after we had turned off the engine.  It was the large belt to the 175A alternator that was loose.  This has probably occurred during the “bedding in” phase of running the engine.  Nick suggested I tighten up the belt using a couple of 19mm spanners and test the engine again.  I don’t have any 19mm spanners and instead used a 19mm socket and an adjustable spanner.  Getting the 19mm socket and wrench back off the nut on the alternator bracket proved to be a devil of a job.  In the end I borrowed one of Nicks 19mm spanners to complete the task.  The rattle has disappeared but it’s obvious tightening the belt will be a regular occurrence.  It also means I need a couple of 19mm spanners.  Off to Google……..

There are plenty of potential suppliers but my criteria limits the range I’m prepared to consider.  One key criteria is price!  After trolling through the ‘hits’ I found a supplier on eBay at £5.85 each.  However after further searching I came across FFX Tools who were able to supply the spanners at £1.86 each. When the postage was added the cost of two spanners came to £5.67.  It looked to be the best deal so I’ve ordered two.  Of course I’ve no way of knowing whether the quality of the spanners will be sufficient for the task.  They may have been made in a field forge in remote China…. and look the part!  But looking at the price of other hand tools on their website I may just have received a very good price.

Nick informed me the belt to the larger alternator will need regular tightening as the alternator will be under heavy load most of the time.  I agree with his opinion as we have been using both alternators to recharge the domestic battery bank on a daily basis.  Of course the alternators are only working hard during the initial ‘Bulk’ phase of the recharging process.  I must go back and re-read the manual for the Sterling PDAR.  Some further research into the voltage level at each phase of the recharging process would also be useful.  The PDAR has an LED to indicate when the battery bank has reached the ‘Float’ phase but the PDAR is in the engine compartment and I don’t particularly want to keep going into the compartment to check on the charging status.  It may be possible to identify the individual charging phases by reading the voltage on the Smartbank gauge or even the remote meter for the Tracer solar controller.  This is also connected to the domestic battery bank.

Browsing through various websites indicates the state of charge for flooded wet cell lead acid batteries can sometimes be determined using the following voltage readings.

Voltage           SOC

• 12.7+     100%
• 12.4        75%
• 12.2        50%
• 12           25%
• 11.8        0%

The battery needs to be rested (not under any load) for several hours (up to 6 hours) prior to taking the reading.  This is almost impossible to achieve on Waiouru because there is always a load on the domestic battery bank. 

Measuring the voltage to assess the battery state of charge (SOC) is apparently the LEAST accurate way. Measuring the specific gravity with a hydrometer is more accurate.  Unfortunately the restricted location of our domestic battery bank precludes the use of  a hydrometer.  Another accurate form of measurement is an amp/hour meter.  This will measure the amps put into the battery and the amps removed.  We know the capacity of our battery bank in amp/hours and could start recharging the batteries when 50% of the available amps have been used.  But the capacity of a battery deteriorates with age and use.  A little like me!  So over time our 450 available amps will reduce.  But we won’t know by how much!  The Smartgauge is clever enough to always know the current capacity of the battery bank and displays it as a percentage.  It’s a clever piece of equipment for dummies like me!  But an amp meter would be handy as it would show both our usage and rate of charge.