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Alternator charging LiFePO4 ?

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Rickety

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OK solar junkies,

I have a 50DN+ ( 24VDC @ 400 Amps ) continuous duty alternator on my bus.

I want to charge some 24v LiPeSO4 cells.

Can I connect my alternator feed ( about 28Volts ) to a MPPT solar in, simulating solar panels and get the correct charging profile for the LiFeSO4 cells ?

Thanks in Advance !

-Rick
 
Rickety said:
OK solar junkies,

I have a 50DN+ ( 24VDC @ 400 Amps ) continuous duty alternator on my bus.

I want to charge some 24v LiPeSO4 cells.

Can I connect my alternator feed ( about 28Volts ) to a MPPT solar in, simulating solar panels and get the correct charging profile for the LiFeSO4 cells ?

Thanks in Advance !

-Rick
Click to expand...
Not really my area of expertise.
However here is an article and some products from Victron that address it.

www.victronenergy.com

Careful - Alternator Charging Lithium - Victron Energy

Charging lithium batteries from an alternator, be that in a boat or vehicle, presents some challenges when compared to the straightforward nature of charging lead based batteries. The video in this blog highlights these lithium challenges and shows you what can happen when things go wrong –...
www.victronenergy.com www.victronenergy.com
 
Rickety said:
Can I connect my alternator feed ( about 28Volts ) to a MPPT solar in, simulating solar panels and get the correct charging profile for the LiFeSO4 cells ?
Click to expand...
Standard MPPT controller probably will not boost voltage if desired. Really need to know the exact equipment for best answers.
Although 28 volts direct is not that bad to put a good charge on LFP.
 
If the 400A is less than the max current spec of the 24V battery bank, I don't see why not. Make sure the alternator really has a 400A continuous duty rating. If the batteries have a BMS, it will shut down the charge going into the battery.

The reason people use a DC to DC converter is because 1) the alternator can't put out enough continuous current and 2) the voltage isn't high enough from the alternator by the time it goes through a long length of wire and has a lot of voltage drop.
 
bruceb58 said:
The reason people use a DC to DC converter is because 1) the alternator can't put out enough continuous current and 2) the voltage isn't high enough from the alternator by the time it goes through a long length of wire and has a lot of voltage drop.
Click to expand...
A standard alternator is not designed to charge LiFePO4 batteries; you need the DC to DC that has the proper charge profile as a go-between—ever heard of using the appropriate wire size for the load at a given length? There's also this thing called cost. The higher the charging amps, the higher the price.
 
if you connect battery to alternator, there will be a biiiiiiig hole effect, as for the moment the current flow will be very high, almost similar to short circuit situation, if the battery will be discharged and big enough. this situation can overload as well alternator, as well bms and also the battery, as the alternator may provide(if he survives the shock) more current, then the battery max charging current. and also, the connectors and cables can blow up... this is just a very stressful barbar connection schema... it can work, if you will be lucky, but most probably not. either alternator will be too big for battery, or bat for alt...

therefor you need to regulate the current and start from zero slowly to the max of weakest component limit...

you can use alternator regulator, but it may not take care for battery needs as balancing and max charging limitations.

best solution will be dc-dc charger or more of them. they will do the job perfectly and much cheaper, then altreg...
 
Cajunwolf said:
A standard alternator is not designed to charge LiFePO4 batteries; you need the DC to DC that has the proper charge profile as a go-between—ever heard of using the appropriate wire size for the load at a given length? There's also this thing called cost. The higher the charging amps, the higher the price.
Click to expand...
Hence my comment. OP has a continuous duty 400A alternator....not a "standard" alternator.

Take a look at a Progressive Dynamics lithium specific converter. It basically is constant current until it reaches 14.6V. There is no float. Basically, same as an alternator.

The Storyteller vans charge their 48v 12KW battery bank with a 48V 8KW alternator. Would be interesting to see how they control their alternator. I can pretty much guarantee they aren't using a 8KW Dc to DC converter LOL.
 
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racmaster said:
best solution will be dc-dc charger or more of them. they will do the job perfectly and much cheaper, then altreg...
Click to expand...
So what's your solution if he wants to put close to 400A into his battery bank?

As I posted above, Storyteller's system puts 170A into 12KW bank with a 56V alternator.

BTW, there are smart regulators that would be perfect for his scenario. Way better than a DC to DC converter.

In addition, if you actually understand how alternators work, you never are going to get max current immediately. Alternators have a linear curve vs RPM typically. Just the start up of the engine and the initial lower current is going to prevent the "biiiiiiig hole effect", whatever the hell that is.
 
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The issue is not so much what the alternator can put out continuously but the fact that some folks like to run the engine of their vehilce at idle, while standing, in order to charge the house battery. In this situation some alternators don't get enough cooling since the vehicle isn't moving and the fan blades on the alternator don't spin fast enough at idle RPMs, and that may very well over-heat and destroy ANY alternator.

The temp rating for OP's alternator is 121°C / 250°F. I'd point a laser thermometer at it, in summer, under heavy load, while standing, and see how its doing. That being said, its a commercial grade unit and it "should" be designed for operation at idle and while standing.
 
McCarthy said:
The issue is not so much what the alternator can put out continuously but the fact that some folks like to run the engine of their vehilce at idle, while standing, in order to charge the house battery. In this situation some alternators don't get enough cooling since the vehicle isn't moving and the fan blades on the alternator don't spin fast enough at idle RPMs, and that may very well over-heat and destroy ANY alternator.

The temp rating for OP's alternator is 121°C / 250°F. I'd point a laser thermometer at it, in summer, under heavy load, while standing, and see how its doing. That being said, its a commercial grade unit and it "should" be designed for operation at idle and while standing.
Click to expand...
It's not going to be putting out close to 400A at idle so less of a concern.
 
I'm wondering what you're trying to charge at 400 amps?

@McCarthy On my last setup, I had a 30 amp DC to DC that charged while driving and was really intended more for night driving while running a 6000 BTU window unit with a thermostat. The dash unit only cools the cab in a class C, but it's open behind you. The window unit in the back is blowing forwards. I don't have to run the rooftop that way, but I can run it while driving during the day with the panels pushing juice. I'm setting up the same on this new one. The one I have is 12/24-volts and 60/30 amps, respectively. My load is only 60% of the capacity of my system; it's how we sized offshore generators in the oilfields. Most generators are sized that way; you get a smoother current, and you're not beating a mission-critical piece of equipment to death at or near the max load. At idle I'm not pushing much juice.
 
bruceb58 said:
It's not going to be putting out close to 400A at idle so less of a concern.
Click to expand...

The low RPM issue has burned up alternators at MUCH lower amps. Most of those commercial setups spin the alternator faster at engine idle in order to produce any amps at all. This alternator does not produce ANY power below 1200 alt RPM at all, so it must be geared accordingly with a large pulley on the crank.

Have you ever dealt with commercial alternators? I don't think so.
 
McCarthy said:
Have you ever dealt with commercial alternators? I don't think so.
Click to expand...
LOL...does working as an electrical engineer for GM in the electronics arm of the company count as experience?

Have you even looked at the size difference between the crank and alternator pulley. It's typically around 4:1.
 
bruceb58 said:
LOL...does working as an electrical engineer for GM in the electronics arm of the company count as experience?

Have you even looked at the size difference between the crank and alternator pulley. It's typically around 4:1.
Click to expand...

So with other words you do not have any experiences with commercial grade alternators. You didn't even understand my prior comment. The increased ratio was exactly my point and defuses your "It's not going to be putting out close to 400A at idle so less of a concern" comment.

MEng, M.S.C.S., BBA

Watch and learn.

 
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