Battery Chargers

[xcw]

I have survived the season using the alternator to charge the batteries, however, I am now thinking of installing a charger on my Bav 36 (2 batteries). The price of marine chargers seems to be very high when compared to car chargers. For example, Halfords are selling a fully automatic charger that they say is suitable for all types of batteries for £37. Even the cheapest marine chargers are significantly more expensive. Do I need a marine charger? What are they giving me that the cheaper option is not?

Your views would be much appreciated.

 

[steve_cronin]

Your Halfords charger is not intended to fully charge a leisure battery to the 100% rated capacity. To do this it needs to charge to 14.4volts. car chargers are intended to "get you going" by supplying enough charge to reach sufficient capacity to operate the starter motor. They usually can't manage more than 13.8volts so this would give you only about 91% of the battery's rated capacity. Now running it up to 14.4 volts straight off will get the battery hot cause suphation and could even damage the plates. So you need a device which will charge in short bursts or pulses gradually diminishing the freuency of these until the peak voltage is achieved and then providing a float charge for a while to achieve complete chemical change in the plates. After that a trickle charge is maintained to counteract the natural discharge always present in a lead acid (indeed in ALL cells to a greater or lesser extent) batteries. Now throw in a good initial burst at say 15.5volts or so to clean the surfaces of the plates and you have the four phase "Pulse Charger"

Marvellous devices and I wouldn't be without one. Sterling make the best by far in my experience but they need a little intelligent setting up which requires more patience than skill and there you are a completely automatic battery maintenance system which will cope with several banks of batteries , gell or standard and of varying capacities all at the same time.

Steve Cronin


ps On your Bavaria, there is a three pin "power out" (ausgang) socket on the rear of the electrical panel specially for a battery charger input - providing you have the shorepower of course. The owners handbook will show you where to connect the low voltage charging leads although to minimise voltage drop I connected mine directly to the batteries (one output for each on the Sterling)

 

[ccscott49]

Only one problem with the sterling charger! They don't make one big enough (output current) for me, boo hoo! /forums/images/icons/frown.gif

 

[steve_cronin]

Was that you wanting 50amps into 24 volts? If so do you run a widescreen cinema on board or something?

Steve Cronin

 

[ccscott49]

No, I want a 75 amp charger! I have a 525ah 24v domestic battery bank, when I want to charge it with my genny I want minimum running time, a 75 amp three stager will do that nicely in about four hours, they never get that low, so thats the reason, the widescreen comes later!!

 

[xcw]

Steve,
Many thanks for a very clear and helpful answer.

Chris

 

[Chris_Robb]

One point to add - Marine chargers such as the sterling will also supply a demand charge - keeping your fridge lights etc going. The Halfords one won't - in fact it would probably burn out.

I use the smallest sterling (25amps) with 260 amps on main bank and 130 on engine. Its more than adequate.

 

[Nigelhg]

are u sure. We have an 80amp sterling charger that we bought last year...it works great but we have to turn it on to half power in most british marinas because it blows the trip....that shouldn't be a problem in the med or running from the genny.BTW it is 24v.

The only thing i would say is that the sterling alternator regulators do charge the batteries better than the charger...we have the sterling battery monitor which shows the charge in amp/hours so u can see how much charge the batteries need to get topped up.

 

[yachtbits]

50, 80 & 100Amp 24v chargers from Sterling are now discontinued.

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