Bartimaeus

Our attendance at Electrika 24 was a last minute decision.  We’d only found out about it a few weeks before, and at that time had thought we might be some distance away.  As it was it did take me a couple of long days to get there.  After my efforts the day before, I was pleased to arrive at the Braunston Locks in the morning and find a lot of action.  I set the top lock and opened the gates.  Another boat arrived before I had driven in, so one of their crew did the rest of the work on that lock.  At the next lock I caught up with a different boat and went down the remainder of the flight with them.  There was a continuous flow in the other direction, so there was always more than one person on the bank, I just stayed at the helm (and even managed to get myself a drink at one point).

After a quick lunch in Braunston I pressed on to the Hillmorton Locks where I got the help of three lock keepers at the top lock, but was then left to my own devices for the other two.  I had hoped to get moored up in Rugby before Clare’s train arrived.  I didn’t quite manage that, but I was there soon enough that she hadn’t got fed up with knitting by the time I found her.

Next day we only had a short distance to cruise to Brinklow Marina  Knowing that we would get electric hook-up when we arrived I’d planned to drive electric the whole way.  We’ve been this way a number of times, but I didn’t remember the graffiti on the bridge.  I shared the picture with my erstwhile colleagues from GeoSciences IT Support – the old GITS.

We had less than a mile to go when beeping started and a message appeared on the screen in front of me.   “Mid-point delta = 6.0%” it said in flashing red.  I have seen this warning before, but not usually with a value that high.  In a previous discussion with Sam, he had made me realise that even 2% indicates quite a big battery problem.

The mid-point delta is a simple but powerful way of monitoring the health of the cells in our battery.  The 48 volt system is made up of 24 cells, each at a nominal 2 volts.  The voltage produced by one half of the cells is compared with that of the other half.  If all is well, the difference should be small.  If one cell is under-performing it gives an early warning that something needs to be investigated.

I did a quick calculation in my head and came to the conclusion that a difference of 6% must mean that one of the cells in the battery is producing no voltage.  I had seen this fleetingly last month in Blisworth Tunnel.  On that occasion I responded by turning the diesel engine on – the message went away, and by the time we came out I had forgotten all about it.

I started the engine again, and was pleased to see the numbers drop quickly.  After a few minutes I turned the engine off again, it would be embarassing to arrive at Electrika with the diesel engine running.  We got to our berth in near silence – phew!

The reception and the event were only a short way from our berth, but there was no bridge (or ferry) so we had to walk about half a mile round the marina.  The local resident moorers were very friendly and the swans and cygnets weren’t as unfriendly as their reputation might suggest – though we didn’t get too close.

The talks on Friday were all interesting.  There were no big surprises for me, but it was nice to have everything brought together.  One feature of our parallel hybrid system I’ve realised is that as we reduce the distances we tend to travel, we spend a higher proportion of our time driving with the diesel engine running.  A serial hybrid has the advantage that it is almost as efficient to run the engine while moored as when travelling, and it is much quieter too.  It could even run while we are out at the shops (other activities are available).  The downside is that sustained power isn’t available – we wouldn’t have been able to do the Ribble Link in a serial hybrid boat.

On Saturday I went to talk to Rob about the battery issue.  While I was waiting my turn, I chatted with Caroline and mentioned that I was now fancying a serial hybrid.  We discussed possible ways forward, I think I was more enthusiastic about it than she initially expected.  After I’d asked Rob about the batteries, he and I talked about upgrade possibilities too.  I went back to Bartimaeus with a clearer idea about the battery issue and a confession.  I told Clare “I may have accidentally bought another boat” – that was an extreme exaggeration.  We aren’t sure what if anything will come of that discussion – watch this space.

I got the mat and the voltmeter out and started testing the voltages of each cell in the battery bank.  They were all showing almost exactly the same voltage except one.  I pulled the auto-watering cover off and peered inside.  As Rob had guessed, it was very dry – the plates I could see should be completely submerged.  I looked inside an adjacent cell to confirm how it should look.

I added quite a lot of de-ionised water to the cell to cover the plates.  Rob was optimistic that the cell will probably recover despite this abuse.  With full sun on the panels and shore power it got a full day of soak charging, by the end of which it was showing a voltage that was only 5% below the other cells – a ten-fold improvement in performance.  I’ll keep checking this cell in particular for a bit, but I hope that problem is now solved.

Electrika 24 was a big success for us.  We enjoyed meeting and socialising with other Ortomariners, Clare was pleased to find the talks interesting and accessible, I got some very helpful technical advice, and we are investigating the possibility of improving our cruising.