Alternator output and Lithium batteries

[PaulJ]

Interesting video for those pondering on Lithiums - 

 

[MtB]

22 minutes ago, PaulJ said:

Interesting video for those pondering on Lithiums - 

 

 

Thanks. Just watched it.

 

Seven minutes spent showing how alternators can overheat when spinning too slowly and connected to lithiums. 50 seconds at the end describing how the BMS disconnecting the alternator wrecks it and putting forward a couple of unexplained fixes. 

 

Skip to 7 minutes if you wanted to see what it says about the 'disconnection' problem. The rest is all very nice but is stating the obvious!

 

 

 

[PaulJ]

9 minutes ago, Mike the Boilerman said:

 

Thanks. Just watched it.

 

Seven minutes spent showing how alternators can overheat when spinning too slowly and connected to lithiums. 50 seconds at the end describing how the BMS disconnecting the alternator wrecks it and putting forward a couple of unexplained fixes. 

 

Skip to 7 minutes if you wanted to see what it says about the 'disconnection' problem. The rest is all very nice but is stating the obvious!

 

 

 

Lol. Well I must admit it isnt the most in depth bit of video- but its seven minutes of not watching/talking/thinking about the corona virus..???

[Dr Bob]

9 minutes ago, Mike the Boilerman said:

 

Thanks. Just watched it.

 

Seven minutes spent showing how alternators can overheat when spinning too slowly and connected to lithiums. 50 seconds at the end describing how the BMS disconnecting the alternator wrecks it and putting forward a couple of unexplained fixes. 

 

Skip to 7 minutes if you wanted to see what it says about the 'disconnection' problem. The rest is all very nice but is stating the obvious!

 

 

 

Yes, anyone who is contemplating putting lifepo4s on board will know the issues with alternators and this video doesn't really give any details. The bench test on high and low revs with the standard alternator is conclusive and says don't run at slow speed but it doesn't help in the real case. My engine bay is a lot hotter than that lab was and what speed is my alternator running at? I don't see that much difference in alternator temp when changing from my engine tickover speed of 750 rpm to cruising speed 1100 rpm ( not a clue what the alternator revs are). The biggest effect on temp is how much current you allow the alternator to generate so my 90A alternator is quite happy at 45A continuous, maybe ok at 50A in winter and overheats at 60A (I am setting a limit of 95degC for the centre top of the alternator casing).

Jono would be better producing a video with real boat data and tips on how to improve it. A massive change can be had by putting a bilge blower on (thanks @peterboat) which can cool the alternator by 10deg.

I agree also on the last few minutes of the video showing a number of ways of 'how to ' but without any details or advantages / disadvantages.

[WotEver]

The video was also misleading. When he spun the alternator at 1500rpm he stated “and this is still higher than most boat engines run at”. Yes of course it is, but I’ve never seen a boat yet that has a 1:1 pulley ratio on the alternator. 

[nicknorman]

The regulator chip I am using for my smart alternator controller project has programmable voltage reduction with temperature - you can specify the temperature at which voltage starts to reduce, and the rate at which it does so. Only problem is that it is measuring the temperature of the chip which in my case won’t be on the alternator, not the temperature of the alternator! Which is why I have a remote temperature sensor in the design. Just by way of an update I now have the microprocessor exchanging data with the regulator chip over LIN bus, and am close to wanting to do a “live trial” ... just one problem the boat is 425 miles away and we are in lockdown!

[TheBiscuits]

3 hours ago, nicknorman said:

I now have the microprocessor exchanging data with the regulator chip over LIN bus, and am close to wanting to do a “live trial” ... just one problem the boat is 425 miles away and we are in lockdown!

Try it on the car