[C320-list] Replacement battery charger

[Graeme Clark]

Hi all,

A few months ago I bought a C320, hull #366, as sole owner, having previously owned a one third share in another (#303)

I have what i guess is the “standard’ arrangement of the time (1996) namely two batteries, each 180Ah and a 1-Both-2-off rotary switch with a Fly-Tec 20-3 mains powered charger.

The previous owner never went near shore power (well almost never) so when we connected everything and looked at voltages, I noticed that the charger is “unwell”. It delivers 15.8V to the batteries which is way too much. I think the charging regime from the Fly-Tec is supposed to give about 14.8v initially then reducing to a lower voltage and eventually even a lower float charge.

So - a replacement is needed. No big deal EXCEPT that technology has moved on a lot in the intervening 20-or-so years since the Fly-Tec was state of the art, and therefore my questions are:

1) is a 20 Amp charger still what’s needed. More Amps = more $, so maybe a modern charger will do the same job on lower amps. Or maybe I need more Amps?
2)  Should I be charging both batteries together, or one at a time. If one at a time would a VSR (Voltage Sensing Relay) be a good idea so that one battery gets charged before the other (I suspect not because surely the output voltage of the charger will trigger the relay, no matter how flat the battery, and both will end up being charged together anyway)
3) On my old (shared) C320 the set up - rightly or wrongly - was that the engine alternator charged only battery 1 and the shore charger only battery 2 and if you wanted to cross charge you needed to set rotary switch to ‘Both’. Is this normal? Advantages and disadvantages of this arrangement?
4) being in Britain we don't have need for AC and only a slight need for refrigeration but our boat is not kept where it can be left permanently plugged in to shore power and so  we plug in whenever we can get alongside but often go for two or three days using battery only. There’s normally some motoring to help keep the batteries topped up and we have an advanced smart charging system via the alternator but its probably accurate to say that the battery will rarely reach full charge through motoring alone. I am aware that battery life is extended by keeping the battery fully charged and not left in a state of discharge for  extended periods of time, so a smart mains charger that fully charges the batteries as fast as is practical would seem to be sensible. Thoughts on that?

Many thanks and here’s to great sailing for everyone in 2015

Graeme