Originally Posted by BriRich
Looks like I will not get an external regulator as I do not want to run my engine so long as to achieve the "float" charge......
Here are lots of reasons you should
fit an external regulator if you can afford it and are doing some cruising, not just weekend sailing out of a marina.
1. It should have multi-stage voltage settings for different battery types.
2. It should also be custom programmable to match the alternator and battery bank sizes. There are so many ‘new’ batteries now that don’t fit the standard charging profiles. Balmar's regulators allow all charging parameters to be changed, for example they can be programmed to stay longer in the absorption stage without dropping down to float too early to get the batteries close to 100% charged.
It is worth noting that with sealed batteries most battery manufacturers recommend that you use a multi-stage regulator to drop the charge down to float mode at 13.2-13.8 volts to avoid gassing and overcharging. This is a condition of the warranty on some batteries.
3. It will delay the charge current for about a minute at start up until the engine oil
is well distributed. A 100 amp alternator draws 4 HP which is a heavy load on an engine when starting with a weak battery.
4. It will also accept a sensor to measure the alternator temperature and control the charge rate. Even a 100 amp alternator could be providing 15 amps to the boat
systems, another 25 amps to say a watermaker
or an inverter
, and then a heavily discharged bank may be demanding 50 or 60 amps. In this situation the batteries may not get charged and the alternator will overheat and burn out from continually trying to deliver its maximum output if not protected by a temperature sensor. It is too easy for the alternator on a boat
to get too hot if used for long periods.
5. It will also accept a sensor to measure the battery temperature which will rise with a heavy charge current. At 25ºC batteries start to gas at 14.4v, at 40ºC they gas at 14v so the external regulator will reduce the charging voltage automatically to compensate for this. If batteries are fitted in an engine compartment it is very easy for them to get too hot and lose water
. This is fatal for sealed batteries. Sailing in high temperature regions may mean the batteries are already at 30C before charging starts.
6. It will have a voltage sensor at the batteries not at the alternator. This will
compensate for split diodes or losses on cable runs to the battery and always maintain the batteries are the right charging voltage.
7. A Balmar regulator has a “small engine mode” that allows you to cut the output to 50% with a switch to reduce the alternator load on the engine when you suddenly need extra power in a big sea. It also has belt manager to reduce the load on the alternator so when set to 70% will run cooler and produce 70 amps at a lower speed.
If you are getting a newer alternator, make sure it has the field wire accessible. This will either need a positive or negative control voltage so make sure the regulator matches the alternator. If you can afford it get a marine
"hot rated" alternator, not an automotive alternator.
So why is an automotive alternator not suitable for deep cycle batteries?
A car alternator is engineered to a price
- because its main job is to charge a starter battery that has been discharged by about 1%, or about 1Ah, which it can do in about 10 minutes. Then it just has to supply power to the car systems. A 60 amp alternator can happily do this job, even when it gets hot, when it's maximum output may have been reduced to about 30 amps, and it's voltage may have been reduced to less than 14 volts by the built in temperature compensation. This is why car batteries don't gas and get overcharged.
A 'hot rated Marine
Alternator', like the Balmar, is 'engineered' to provide its rated output current even at a temperature of over 100 degrees C, so it will maintain that output current and voltage and so charge the bank much quicker. Faster charging is what we all want.
This 'hot rated engineering' may mean:
- High temperature diodes mounted on big heat sinks
- Heavier gauge stator windings
- precision balanced rotor
- Copper composite brushes
- Heavy duty bearings with high temperature grease
resistant materials & coatings
- Dual cooling
- access to field windings
- tachometer output
- maybe an isolated ground terminal
All this comes at a much higher price!