Details of the charging and battery system on Lionheart No 2

First problem. Starting the engine.

When we bought Lionheart No 2 the electrical system was far from ideal. In fact it was somewhat similar to many of the boats we get called out to, to put things right.

The first problem was the engine start battery. It was a deep cycle Gel Cell. Now whilst these will (and regularly are used to) start an engine they are not ideal for this purpose. They are happy to be deeply discharged (unlike an engine battery) but pound for pound, can produce far less current in short bursts than the same size engine start battery. Engine start batteries also have the added bonus that they are cheaper.

In the case of Lionheart No 2 the problems were further compounded by the fact that the engine is huge, a Gardner 4LW, which naturally requires far more cranking power than a typical Narrowboat engine.

To make matters worse the batteries were located under the seats in the boatman's cabin and connected via approximately 10 metres (round run) of 35 sq mm cable via an isolator switch that really wasn't up to the job. At the huge starter currents drawn by such a large engine, even with the battery fully charged, the voltage seen at the starter motor during cranking was around 8.5 volts.

On top of all this was the fact that the only charging to the engine start battery was from a dynamo producing around nothing at idle speed and sluggishly increasing to approximately 12.8 volts at a maximum of around 20 amps with the engine screaming at the red line !

No wonder starting the engine was such a problem, involving as it did, use of the decompression lever (which is really only there for hand cranking). The engine battery was replaced with two real engine start batteries, the cabling run in a much shorter path, the cable increased to 70 sq mm and the isolator switch replaced with a bigger, better unit. The result is that the engine now fires first time, cranking at not much below idle speed.

Second problem. The domestic bank

The domestic bank consisted of 4 x 100 Ah Gel Cell batteries. I personally have a lot of respect for this type of battery and after testing them decided to keep them. Properly looked after they do last a long, long time.

Addendum. 21/08/2005. After another 3 years of use the gell batteries finally gave up the ghost. I suppose 7 years total life isn't so bad. They have been replaced with a set of 4 Lucas 679 deep cycle antimony/antimony batteries which are performing well.

Originally this bank was charged by a 70 amp alternator with an internal controller and cabling that was too thin and too long losing about 2 volts between the alternator and the batteries at maximum charge current which due to the cable size, cable run length and regulator only lasted a very brief period of time having soon dropped to around 30 amps.

As the old engine battery was now redundant this was added to the domestic bank giving 500 Ah. Alternator cable size was increased from (I'm guessing because I just laughed at it when I saw it) 25 sq mm to 70 sq mm and the total run length was reduced from about 8 metres to less than 4 metres. Again the isolator switch was replaced with a proper one.

The alternator now performed much better but still not good enough. It was removed and replaced with a Powerline 120 amp unit and also fitted with an external alternator controller. In this case I used a Link 2000R dual battery monitor with integral alternator controller, not for any reason other than I happened to have one in the workshop doing nothing. In all fairness most external alternator controllers (with one exception that I will not name) do pretty much the same thing and I would have been happy to install several other makes knowing I would get the same results. There are quite drastic differences in performance between the various models available on a technical level. As far as getting charge into the batteries and looking after the batteries properly there's hardly any difference. I know, I've measured and tested them all. Bells and whistles is the only real difference between them.

Charging to the domestic bank is now much improved giving 120 amps at cruising engine RPM but it does drop off quite badly at tick over speed. This is due to the low idle speed of the engine and insufficient pulley ratio. There's not much I can do about this without introducing a layshaft arrangement which I don't have time to do at present. Perhaps in the future.........

Further recent improvements

Finally it was time to sort out the charging to the engine battery

I (naturally) chose the easy way out by installing a SmartBank Split Charge System - it also has the advantage of being the best split charge system available. I would say that but I genuinely do believe it - so do many marine engineers and fleet vehicle builders.

I used a SmartBank Standard connected to a SmartGauge battery monitor. Operation of the unit in the case of Lionheart has given the SmartBank its most difficult test yet. This is due to the fact that at low engine RPM (which obviously ocurrs regularly when locking) the alternator output drops quite badly and as we usually have the tumble dryer and washing machine on all the time we are cruising (I usually have my two young children on board) the SmartBank regularly disconnects the engine batteries at times when the heavy loads run the risk of discharging them, then reconnecting to maintain their charge once the engine revs rise or the demand on the domestic bank drops. This would not happen with a "normal" split charge relay energised from the alternator (the normal "cheapo" method) and the washing machine and tumble dryer (and any other loads) would be running from the engine battery at times when the alternator was not able to keep up with demand. If this situation was allowed to continue then it could easily lead to a flat engine battery.

The other major advantage is when we do plug into shorepower and use the mains powered battery charger it automatically takes care of the engine battery. We don't have to remember to do anything. This will also be of benefit when we add the wind turbine (I'll get round to it one day). That's all we'll have to do, simply add the wind turbine, we won't have to play around adding another system to allow the wind turbine to charge both battery banks. The SmartBank will take care of it automatically.

If you're thinking "but split charge diodes would do the same thing" then have a look here to convince yourself of why they wouldn't. Diodes are a waste of time and money. Ask any truly experienced marine electrical engineer.

Originally I also installed the optional standard SmartBank II remote panel (no longer available). This was made redundant by the use of the SmartGauge operating as remote for the SmartBank. The original remote panel now operates as a remote for yet another SmartBank which partly controls the battery compartment vents and thus gives automatic twin speed fan assisted battery venting.

The major components of the DC system on Lionheart No 2 are shown in this diagram.

Not shown in this diagram is the battery compartment forced (i.e. fan assisted) venting system which is detailed here and here.


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