[C320-list] Alternator upgrade

[Graeme Clark]

I’ve a feeling this is going to be a bit like one of those threads about which anchor is best! Everyone has a different view which is dependent to a degree on their local environment!

There is a good article (albeit trying to sell you a new alternator) here : https://www.mastervolt.com/all-you-need-to-know-about-alternators-and-charge-regulators/ <https://www.mastervolt.com/all-you-need-to-know-about-alternators-and-charge-regulators/>

If you don't  have time to read it in depth here are some edited highlights!


"Standard alternators, originally designed for the car industry, only deliver sufficient energy to both charge the batteries and power the various onboard consumers when they reach a very high rpm.

These alternators also tend to be temperature-sensitive: In a higher ambient temperature, such as is common in an engine room, their output quickly falls by 50 % or more. This is not a problem in cars as the small amount of energy used during, for instance, starting can be recharged in no time, and windscreen wipers, ventilators, etc. do not need a great deal of power. In general, a car engine also runs at a far higher rpm than a boat’s engine, and the temperature under the hood is lower due to the cooling effect of the head wind.

Make sure you do not choose your alternator too small. A larger one will ensure that the battery is charged faster and engine hours are kept to a minimum – we suggest choosing an amperage between 30 and 50 % of the battery capacity.

The standard alternator designed for road vehicles has a voltage regulator mounted to the back of the alternator and set to a single charge voltage of 14v. This is sufficient for a car battery, which is rarely (if ever) discharged. Furthermore, the voltage regulator of an automotive alternator is often temperature sensitive and in high temperatures regulates the voltage even further down, often to 13.5  volt. This is much too low for sufficiently recharging a discharged battery. The maximum achievable battery capacity for these voltage levels is around 60 to 70 %. The lifespan of a battery is significantly lower if it is never properly charged. In order to adequately recharge a partially empty or completely flat battery at 25 ºC, (77F) voltage need to be 14.25 volt Once the battery is 100 % full, this voltage must be reduced to 13.25  (float phase) to prevent the batteries from becoming overcharged.  A “ smart” charge regulator maximizes the output of the alternator by regulating the alternator in a way that the batteries receive the optimum charge. 



Graeme
#366, 1996


> On 26 Aug 2020, at 04:34, Jack Brennan <jackbrennan at bellsouth.net> wrote:
> 
> There’s a bit of confusion because everyone has to adapt to local conditions and their sailing style. That’s really the key to the setup you decide on.  What works for me may not work for you. Here is what works in Florida:
> 
> To me, the alternator is basically a bulk charger. After spending the night at anchor and using up amps, motoring in the morning before the wind picks up gives you a good jump on restoring the house bank to maybe to 80 percent or so. I don’t have a need to top off the batteries with the alternator.
> 
> That’s because a good MPPT solar controller acts like a smart charger, putting as much of the 5-8 amps an hour as it can into the batteries. So I can usually top off the batteries during the day while sailing, even using the autopilot, depth sounder, etc. (This won’t work with cheap controllers.)
> 
> When we stay at anchor with no motoring, my 160 watt panel will usually top off the house batteries by early  afternoon as long as we’re not eating up the amps with music and it’s not too cloudy. (Car-type stereos really eat up the amps. Use your phone and a portable speaker.)
> 
> I keep the fridge on at the dock 24/7 with no 110, and the solar panel keeps up, so it’s really an issue of what else we’re doing that requires power when we’re at anchor. Being near the subtropics, that usually means fans as well as an anchor light, etc.
> 
> Jack Brennan
> Sonas, 1998 Catalina 320
> Tierra Verde, Fl.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Sent from Mail for Windows 10
> 
>