FET Battery Isolator and Different Charging Voltages

mermike

mermike

.
Nov 21, 2012
598
Yamaha 33 Port Ludlow, WA
Related question, can an ArgoFet or Orion provide enough resistance to absorb the voltage spike?
 
heritage

heritage

.
Apr 22, 2011
865
Hunter 27 Pecan Grove, Oriental, NC
Johann said:
I don’t believe this is the case with any internal BMS batteries. Victron Smart Batteries and Lithionics External BMS model, yes. But they have a single BMS communicating with the individual batteries.
Click to expand
Correct... most of us with lfp battery banks have no communication between batteries. If one bms freaks out the others are not affected.

I think that the most likely scenario of a bms shutting down a battery is if the alternator is able to put one of the battery cells over 3.65 volts. If this happens on one of the batteries then it will most likely happen soon on the others because they are in parallel and of very similar voltages. Why I don't think this is a problem for the alternator is that the current flowing into full batteries is very low, so any spike would be minimal and shouldn't cause any damage to the diodes.
 
J

jdrutten

.
Mar 27, 2021
139
Hunter 306 Lake Pepin
mermike said:
Related question, can an ArgoFet or Orion provide enough resistance to absorb the voltage spike?
Click to expand
Bumping this because I'm wondering the same thing. I put the cart in front of the horse a bit and got a good deal (i.e. budget) on a new-fangled LFP house battery to complement my FLA start batteries before doing anything with my charging system. Now I'm faced with possibly converting my Hitachi 60 amp alternator for external regulation, and then using some mix of Orion dc-dc charger and/or an argofet along with all the related fuses and cabling. It all adds up.

Maine Sail's "Drop-In LiFePO4 Batteries" article at MarineHowTo depicts the Balmar APM in both the argofet and Orion scenarios. Of course I'm inclined to accept the general wisdom of this, but if I can get away, at least in the short term, with not having to buy an APM in addition to everything else, then I might be inclined to put it on the back-burner. In the event of a BMS disconnect, wouldn't the FLA absorb the full 40 amps or whatever my diminutive alternator might be pushing out? Likewise with the Orion?
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,674
Canadian Sailcraft 36T Casco Bay, ME
jdrutten said:
Bumping this because I'm wondering the same thing. I put the cart in front of the horse a bit and got a good deal (i.e. budget) on a new-fangled LFP house battery to complement my FLA start batteries before doing anything with my charging system. Now I'm faced with possibly converting my Hitachi 60 amp alternator for external regulation, and then using some mix of Orion dc-dc charger and/or an argofet along with all the related fuses and cabling. It all adds up.

Maine Sail's "Drop-In LiFePO4 Batteries" article at MarineHowTo depicts the Balmar APM in both the argofet and Orion scenarios. Of course I'm inclined to accept the general wisdom of this, but if I can get away, at least in the short term, with not having to buy an APM in addition to everything else, then I might be inclined to put it on the back-burner. In the event of a BMS disconnect, wouldn't the FLA absorb the full 40 amps or whatever my diminutive alternator might be pushing out? Likewise with the Orion?
Click to expand
It might and it might not, the diodes the the Hitachi alts are not very robust.The Orion can be load dumped and survive, because it is switch mode not a magnetic field, but, the alt can't. Best to have an APM or Sterling APD..Remeber it is the speed / voltage of the transient that causes the damage

QWe have a bunch of APD's left in our bargain bin.......

The Bargain Bin - Marine How To
 
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