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Post Info TOPIC: 2 ways lithium can kill your alternator


Senior Member

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2 ways lithium can kill your alternator


This video is targeted for sailors and power boats but I expect it could apply to motor homes and camper-vans that have upgraded to lithium batteries. Apparently under certain conditions the BMS shuts down during charging thereby causing an open circuit to the alternator which can fry the diodes.

 



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In the meantime our 300Ah 4 cell Sinopoly LiFePO4 battery has survived 9 years of fulltime travel being charged by our Canter 100A rated alternator at 70-80A. The battery also starts our 3.9l turbo diesel engine often multiple times a day. No smoke yet.

I knew there was a reason for omitting any inbuilt BMS. biggrin



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Correct me if I'm wrong, but this guy didn't mention "load dump". That's the term that everyone uses to describe the phenomenon where an alternator is abruptly disconnected from its load(s).

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I will look at that in detail later but I suspect it is alarmist BS.
In a vehicle all sorts of high amp loads switch on and off all the time and the alternator just does its job. Indeed all modern alternators have zenner type main diodes for years so any higher voltage peaks will be dissipated by the main diodes which are in heatsinks any way so handle any power dumps ok. Then the alternator regulator will turn down the excitation to reduce voltage to normal and power output to what is required.

Well coming back to this video my opinion has not changed. He has a whole grab bag of ideas that sound possible but not much evidence to back up the problem scenarios. But surprise surprise he does have a little white box to help, for sale I guess ? Also I do not think his marine engine alternator will be affected the same as a MH or similar vehicle use. It is true that running an alternator at high output at low revs is not good for the alternator heat dissipation. If I need to top up my batteries I always run the engine at about 2000-2500 revs by something on the accelerator and open the bonnet. 

I think we can all rest easy in our beds and sleep well. I for one would convert to lithium and not be concerned if I have applied common sense to my selection. The built in BMS might be a stumbling point in cheap low amp rated batteries but do not buy that type anyway, do your home work first.

jaahn



-- Edited by Jaahn on Thursday 7th of December 2023 09:04:01 PM

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I suspect its a stunt to sell his gizmo.

In my boating days the cranking battery was direct feed from alternator, and the Deep Cycle Battery was feed via a VSR, and both batteries had isolations switches.

No need for DC-DC chargers, a simple protection is to use an MPPT solar charge controller between the VSR and BMS.



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Some useful reading material in this thread:

 

https://thegreynomads.activeboard.com/t67732755/lithium-batteries-charging-discharging-balancing/



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Whenarewethere wrote:

Some useful reading material in this thread:

 https://thegreynomads.activeboard.com/t67732755/lithium-batteries-charging-discharging-balancing/


click here for that link.

https://thegreynomads.activeboard.com/t67732755/lithium-batteries-charging-discharging-balancing/ 

jaahn



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Marine setup can be different as there may not be any lead acid (or non-bms lithium) in the circuit to act as a sink, so overvoltage spikes can occur.

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Mumbo Jumbo. If what he says is a problem then the battery makers would incorporate a solution in the management system. Or a suitable sized resistor or capacitor across the alternator output to bleed off the self induced voltage caused by the collapsing magnetic field in the wiring.

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