Alternator Paralleler Circuit

[Tractor]

When paralleling DC generators, the system requires a falling Volts load characteristic, in order to prevent one generator progressively taking all the load from the second generator, and load sharing is effective. Here this does not happen, when in use, I cannot see why this is the case?

Edited February 27, 2019 by Tractor
failed to read all the 'thread'..

[Jen-in-Wellies]

Another way of doing alternator paralleling for Lithium batteries. 

 

[Guest]

Hi bud, cool experiment but an alternator only charging 1a won't put any load on the belt and the crank pulley, one charging at 80a will load the engine and the anti stall setting will increase the fuel supply to keep the revs up. You can get a 1,2, off isolator and switch between the batteries and observe the change in load on the engine 

[Tony Brooks]

40 minutes ago, Wildling said:

Hi bud, cool experiment but an alternator only charging 1a won't put any load on the belt and the crank pulley, one charging at 80a will load the engine and the anti stall setting will increase the fuel supply to keep the revs up. You can get a 1,2, off isolator and switch between the batteries and observe the change in load on the engine 

 

I take it you understand this topic is about LFP lithium batteries and not lead acid. Using an automotive alternator plus a 1,2, both, off switch without a B2B in a hybrid system is very much frowned upon, totally against the lithium battery makers/vendors advice, and may soon fall foul of upcoming regulations.

 

Your solution seems to ignore the fact that lithiums will take all the current the charge source (alternator in this case), can throw at them until the batteries' BMS cuts off the charge. This creates two problems for the alternator and potentially your pocket.

 

1. Automotive alternators that the vast majority of boats use are designed to feed lead acid batteries where the batteries themselves start to limit the current within minutes of stating - say 15 minutes, so they only run flat out for a short time. Connect them to LFP batteries and the alternator is likely to burn out unless the charge is controlled - hence the use of a B2B

 

2. When the BMS open circuits the charge, it is likely to create a voltage surge in the alternator that may    burn alternator components or blow electrical equipment on the boat.

 

I feel that you may do well to study the many lithium battery charging topics on this forum, especially the newer ones.

[Sailbadthesinner]

Thread was started in 2009, don't think it's about LFP.

[ditchcrawler]

8 minutes ago, Sailbadthesinner said:

Thread was started in 2009, don't think it's about LFP.

Someone's awake 

[Tony Brooks]

16 minutes ago, Sailbadthesinner said:

Thread was started in 2009, don't think it's about LFP.

 

But the piece it seems Wilding responded to was Jens from 2025 and it definitely was about parallelling with LFP batteries. If the response was to a for more historic post, then I apologise.

 

It would be far easier to know what was in Wilding's mind if he had quoted the post he responded to.

[jonathanA]

13 hours ago, Sailbadthesinner said:

Thread was started in 2009, don't think it's about LFP.

I couldn't really understand what @Wildling was on about to be honest, my thought was he clearly had not read the last few posts or didn't understand what Jen (and I) were discussing, then, after Tony responded i thought i'd wait for clarification. 

To me suggesting the use of a 1,2,off,both switch is very much out of fashion these days even for Lead acids and if you did, care would need to be taken not to select the off position whilst the engine is running. 

[Guest]

49 minutes ago, jonathanA said:

I couldn't really understand what @Wildling was on about to be honest, my thought was he clearly had not read the last few posts or didn't understand what Jen (and I) were discussing, then, after Tony responded i thought i'd wait for clarification. 

To me suggesting the use of a 1,2,off,both switch is very much out of fashion these days even for Lead acids and if you did, care would need to be taken not to select the off position whilst the engine is running. 

If I had known that the post was from 2009 I wouldn't have revitalised it, it was at the top of the forum pile.. I will only post this reply and then let it fall back to the silt