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Thursday, December 29, 2011

Battery Rewire




Having now had 3 people say that our cables from the Victron invertor/charger and the batteries, and between the batteries, were too small, today we replaced them all. The existing cables are 40mm and we have replaced them with 70mm ones, these measurements are the cross-sectional area of the wire, not the diameter for none electrical people, just in case you, like me, thought that’s a hell of a large diameter cable! The diameters are 7mm and 9.5mm respectively.

We had been told originally by Simon Pollard who had visited us at Crick when we had our battery blow up. He came to check the Victron and discovered the temperature sensor was causing it to overvoltage which is what blew the battery up. At that time he had commented that the cables to the Victron from the batteries were too small.

We have been trying for the past 2 years to get to Whaley Bridge to get Brett from Kuranda to check our electrical system, especially following the blown up battery incident. Recently we have been having problems with the charger not starting up correctly, which has steadily been getting worse. On Tuesday we visited Keith & Ann on Oakfield, and he also thought out cabling was undersized, so yesterday I telephoned Brett and he confirmed this. Not only this but the Victron had been cabled directly to the 1st battery and then each subsequent battery, but Brett stated that the +ve and –ve connections from the Victron should go to opposite corners of the battery bank. The reason for this apparently is to distribute the charge/discharge across all the batteries evenly, rather than to the 1st then the 2nd, etc.. Unfortunately for me when I studied electrics at college in the late 60’s, batteries in parallel was not covered, in fact in those days it was considered not the done thing. Of course battery technology has moved on since then, so it is an area I am unfamiliar with in electrics/electronics.

After speaking to Brett we decided we really ought to change the cables whilst we were still here in Braunston, so we  measured our existing cables and I then went to Midland Chandlers and they made the required cables up for me, which I collected from them first thing this morning.

Taking out the old cables and replacing them with the new ones went far better than I expected. It took 2 hours start to finish which was not bad really, considering the scale of the task of 4 batteries to rewire and new cables to feed through from the batteries and master cut off switch to the Victron. Especially as it is something you really need to take time over to make sure that you get it right first time, and especially making sure no accidental shorting occurs, sparklers are for Bonfire Nights only! We will only see the real benefit of this when we change the batteries for new ones, which we will do when we do eventually get to Whaley Bridge this year.

P.S. please note the links to the Victron Invertor/Charger is a newer updated version which is 3000watts whereas ours is 2500watts, apart from that they are identical.



Halfie said...

Keith and Jo, I have finally got round to adding you to my blog list! I trust you are having a good Christmas and that you will have a Happy New Year.

Keith (Boatman) said...

Hello Halfie, we had a nice quiet Christmas and now looking forward to a Happy New Year. We hope the same applies to you. See you about sometime.

Happy New Year to you.


Anonymous said...

Keith, I have a victron charger/inverter on my yacht (the Easyplus 70A/1500w) and have had a similar problem to yours with the charger starting. I found that if I disturbed the temperature sensor wire the charger started so in conversation with victron we've concluded that a new sensor is needed. I dealt with victron UK directly and they have sent me a replacement sensor foc. It sounds like you've done the right thing with your battery cables; I've 10mm cables on my setup. The contractors upgraded the cables that came with the victron when new which surprised me but better safe than sorry! We run AGM batteries (2x 255ah + engine start) so was concerned to hear of your over voltage, I don't think I've seen that problem thank goodness, that would kill AGM's in short order.

Good to swap ideas between narrow boaters and yotties eh! Happy new year to you.

Robert Horsford
Sy Crazy diamond

Keith (Boatman) said...

Happy New Year Robert, Our overcharging problem had been caused by the temperature sensor, so, like you, we changed it, however for us the new sensor did exactly the same thing, so I immediately disconnected it again, and following my discussion with Kuranda, where our batteries are sited in the bottom of the boat, and not affected by engine or generator heat, they reckon that the temp sensor is overcompensating, so instead of it reducing the voltage if the batteries get hot, it is increasing the voltage if the temp is colder. The batteries sit directly on the steel base plate of the boat which is always at water temperature, so it stays very cool down there, especially when the canal freezes. In our situation the temperature sensor is not only unnecessary, but acting in the opposite direction, after all the sensor is a temperature sensitive resistor, so as the temp increases it reduces the voltage, hence if the temp drops it increases the voltage.