Originally Posted by Ex-Calif
... What makes an alternator suitable for deep cycle or not deep cycle? It's a field winding, a stator, some diodes and a commutator.
Sorry about my 'colourful' language but somehow you have to draw attention to the differences between products which will do the job properly in a marine environment
'Cheap' is probably the key to the difference - for example auto shore power
chargers which can be dangerous on boats - see Main Sail posts for this, cables
should be 'tinned' to stop corrosion
, and through-hull fittings should be made of DZR brass to stop dezincification. These and many other products are sold by chandeliers who don't know any difference, which is why I try and advise 'best practice' when buying
kit for a boat. I can't afford to buy 'cheap'. Too many kit failures spoils the 'Cruising' Experience.
So why is an automotive alternator not suitable for deep cycle batteries? This has already been said by others on this and many other threads.
A car alternator is engineered to a price
- cheap - 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.
On a boat the load on the alternator to charge a 50% depleted 400 Ah bank will be much higher for much longer. 200 Ah will have to replaced in the bank, so it will be trying to supply near it's maximum current
for a long time and it will get even hotter and it's output may fall even further. A 'hot rated Marine Alternator', like the Balmar, is 'engineered' to provide 60 amps even at a temperature of over 100 degrees C, so it will maintain that output and 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!
Since I am replying to a 'Moderator Emeritus' I shall continue to defend my colourful language, at the risk of 'breaking the regulations'. As to my use of the word 'Bodge' this is exactly what the Apollo 13 astronauts did to fix their air filters. I'm doing it all the time on my boat to keep me cruising in the Med. If you can't get the right parts
, or you can't control the alternator by getting access to the Field wire, then that is a 'Bodge'. djmarchand in his post called it a 'Kluge' which is surely much more derisory term.
As to the use of the word 'idiot' I have explained that on the other posting
? Mr Sterling feeding 160 amps into a 100 Ah battery to prove his fast chargers are the best is not a sensible thing to do, or to encourage others to do, without some safeguards or warnings. The amp-hour law suggests that the maximum safe current should be 50 amps if the battery is 50% depleted.
If you agree that this is NOT a sensible thing to do then you should also accept that this is a 'foolish' thing to do. The opposite of sensible is foolish. In the UK a definition of 'idiot' is stupid or foolish.
I could also draw attention to Mr Sterling's latest product literature where has changed the graphs from the link you kindly provided. Your link showed the voltage being switched off for 3 minutes every 20, so 15% of the time the charger
is not charging.
This link: http://www.shop.sterling-power.com/acatalog/AB.pdf
- shows a flat graph for the same product, with no output interruption. He still describes in the text that there is an output reduction. So how would you as a Moderator Emeritus describe this latest marketing