Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

Please bear with me- I'd like to explore a different direction than what we'd previously planned.

Instead of starting with our expected electrical usage and working forward to develop an electrical system that will supply those needs, I'd like to start (for the purpose of discussion) with the single 250A alternator of the gas Sprinter and work backwards, to see how much electrical capacity we can realize, without generator, solar, or shore power.

LiFeP04 charges faster than AGM or flooded-cell, which I would expect would reduce the amount of time that we would need to run the engine every day to recharge.

Would we need to actually drive the van to recharge, or would the stock 250A alternator put out enough at idle to power the DC/DC charger to it's full potential?

Would a larger DC/DC charger recharge the LiFeP04 battery faster than a smaller one, like using the 60A Sterling as opposed to the 30A Sterling?

FWIW, I'm spit-balling our electrical consumption at less than 100Ah per day. LED lights, one ceiling fan, cell phones, and generous use of our laptops. We would not be planning on powering an air conditioner off of this. Our stove/oven/water heater would be propane. Our largest energy hog would be our refrigerator. We're looking at the Dometic CFX 95DZW, which is rated at 1.3Ah/h in 90F ambient temperatures, with a 41F internal temperature (31.2Ah per day).

And I don't think we need a ridiculous amount of battery capacity, because we're going to be living in it full time, so we'll be able to run the engine every day and/or drive it every day to recharge.
 

marklg

Well-known member
I had issues with an older 60A Sterling and my LiFePO4s. It may be it had some soft fault, but it overheated and cut back the output current. They are replacing it with a new one that is supposed to be better with LiFePO4s. I will post how it works when I install the new one next week. You probably want the latest model.

You do need to pay attention to their installation instructions and oversize the wire. If it is able to charge at the full rate, the larger charger will definitely charge the battery faster.

What model and region is the Sprinter? If it is a recent "Euro 6" you definitely want the latest model DC/DC charger.

Regards,

Mark
 

avanti

2022 Ford Transit 3500
Are there MB-published upfitter guidelines available for the new Sprinters yet? My going in assumption would be that in order to implement a modern charging system for the chassis, it is likely that they will require that current take-off from the chassis be limited to some value. For the NCV3, that value is 40 amps
 
Are there MB-published upfitter guidelines available for the new Sprinters yet? My going in assumption would be that in order to implement a modern charging system for the chassis, it is likely that they will require that current take-off from the chassis be limited to some value. For the NCV3, that value is 40 amps
Good question...

Anybody know the answer?
 

autostaretx

Erratic Member
Please bear with me- I'd like to explore a different direction than what we'd previously planned.

Instead of starting with our expected electrical usage and working forward to develop an electrical system that will supply those needs, I'd like to start (for the purpose of discussion) with the single 250A alternator of the gas Sprinter and work backwards, to see how much electrical capacity we can realize, without generator, solar, or shore power.
So i'm going to cut you off right here and answer:
(a) in previous year's Body Builder's Info Guides (available here), MB has had a consistent drum-roll of "thou shalt only extract 40 Amps from the alternator for nefarious purposes" ... without having a footnote about the various alternator sizes that were available.

(b) So let's guess that 80 amps is really easily available.

That means you'll be able to harvest 80 Amp Hours per hour of driving/engine operation (above 1000 rpm).

So: multiply 80 by the number of hours you'll be running your engine, and there's how much you have to work with. No generator, solar or shore.
FWIW, I'm spit-balling our electrical consumption at less than 100Ah per day. LED lights, one ceiling fan, cell phones, and generous use of our laptops.
So a 200 AH AGM pack would handle that, or (let's say) 120 AH of LiFePO4 .... and expect to drive for 1.5 to 2 hours per day, assuming the batteries could take an 80A charge rate. Scale as need be.
Your driving time could well be dictated (i.e. stretched) by the battery's limited ability to accept charge.

--dick
 
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john61ct

Active member
Idling will not by default put in many amps, but specialized setups exist.

But with **the right** LFP setup, even 1-2 hour's driving will put say 300Ah into your bank.

Now, how long that will last you living off grid becomes a matter of lifestyle and energy efficient decisions.

Use LEDs, small screens, a 12V fridge, propane for cooking, etc.

> Would a larger DC/DC charger recharge the LiFeP04 battery faster than a smaller one, like using the 60A Sterling as opposed to the 30A Sterling?

of course

Stack 3x 60A to maximize short drives, only one will be OK if you're driving all day.

I'd go at least 200Ah.
 
So i'm going to cut you off right here and answer:
(a) in previous year's Body Builder's Info Guides (available here), MB has had a consistent drum-roll of "thou shalt only extract 40 Amps from the alternator for nefarious purposes" ... without having a footnote about the various alternator sizes that were available.
Thanks.

(b) So let's guess that 80 amps is really easily available.
Wait, what? I thought you said 40 amps?

[/quote]That means you'll be able to harvest 80 Amp Hours per hour of driving/engine operation (above 1000 rpm).[/quote]

So: multiply 80 by the number of hours you'll be running your engine, and there's how much you have to work with. No generator, solar or shore.[/quote]

Copy that...

So a 200 AH AGM pack would handle that, or (let's say) 120 AH of LiFePO4 .... and expect to drive for 1.5 to 2 hours per day, assuming the batteries could take an 80A charge rate. Scale as need be.
Your driving time could well be dictated (i.e. stretched) by the battery's limited ability to accept charge.

--dick
...and copy that.

Thanks, Dick.
 
Idling will not by default put in many amps, but specialized setups exist.
Yeah, I was afraid of that, but it is a 250A alternator, so I was hoping that even at idle that it would be putting out enough to run the van and still charge the house battery quickly.

But with **the right** LFP setup, even 1-2 hour's driving will put say 300Ah into your bank.

Now, how long that will last you living off grid becomes a matter of lifestyle and energy efficient decisions.

Use LEDs, small screens, a 12V fridge, propane for cooking, etc.
Yes, that's what we're talking about.

> Would a larger DC/DC charger recharge the LiFeP04 battery faster than a smaller one, like using the 60A Sterling as opposed to the 30A Sterling?

of course

Stack 3x 60A to maximize short drives, only one will be OK if you're driving all day.
You can run them in parallel?

I'd go at least 200Ah.
Thanks- we haven't made any hard and fast decisions yet, we're just trying to explore the feasibility.

The way I'm thinking, is that the amount of money that I'd spend on solar and/or a generator, might be better spent on LiFePO4 that charges faster, and a big DC/DC charger to harness the power of that 250A alternator. I figure we'll be driving an hour a day anyway, just going to the health club to work out and shower, driving to go grocery shopping, and so on, even if we're not changing cities.

Thank you, John.
 

owner

Oz '03 316CDI LWB ex-Ambo Patient Transport
My T1N 150A alternator will shove around 50A into my 160Ah LFP bank when it is depleted at idle. If I increase the idle speed to 900rpm that jumps to 100A+. I normally charge via a 30A DCDC to limit the current load on my alternator. I have a switch to do this or to charge directly from alt. So if I want to quickly put some juice into the bank faster than 30A, then I run it at idle directly connected for the 50A charge rate. Then when it has sufficient charge I will run at high idle so that the charge rage is below about 80A. You don't want to be changing your LFP bank too fast.
 

Graphite Dave

Dave Orton
With 300+ watts of solar, your location and your listed loads there would be no need to ask the question about how much you would need to drive, How about no driving required.
 
My T1N 150A alternator will shove around 50A into my 160Ah LFP bank when it is depleted at idle. If I increase the idle speed to 900rpm that jumps to 100A+. I normally charge via a 30A DCDC to limit the current load on my alternator. I have a switch to do this or to charge directly from alt. So if I want to quickly put some juice into the bank faster than 30A, then I run it at idle directly connected for the 50A charge rate. Then when it has sufficient charge I will run at high idle so that the charge rage is below about 80A. You don't want to be changing your LFP bank too fast.
Excellent.

If you're getting 50A at idle out of a 150A alternator, then I shouldn't have anything to worry about with a 250A alternator.

Your idea of charging directly off the alternator is inventive, but I'd probably prefer the safety of just using the DC/DC charger.
 
With 300+ watts of solar, your location and your listed loads there would be no need to ask the question about how much you would need to drive, How about no driving required.
Dave, you're a smart dude, and I love you like a (much older) brother, but I did say no solar for the purpose of this discussion. :smilewink:
 

markxengineering

Active member
My T1N 150A alternator will shove around 50A into my 160Ah LFP bank when it is depleted at idle
I will second this, using a 50 amp kisae b2b charger, 50 (well maybe 48) amps at idle is no problem for 150 amp sprinter alternator. If you end up needing more out of the alternator, a smaller pulley might be something to look into. The output of an alternator is very non-linear with large gains for very small RPM increases near idle.
 

HarryN

Well-known member
The typical consumer available LiFe battery that is discussed on forums like this should be thought of as charge / discharge rates of about 500 watts per battery. (example BB 100 amp-hr or similar).

This is a separate number from what the van's electrical system can provide for feeding into the appropriate charger to manage the power transfer, but it helps when determining component sizing.

It is helpful in matching battery capacity with inverter demand as well. A 2 kW inverter really needs at least:

( 2000 watts inverter ) / (500 watts per battery) = 4 batteries.

Which is exactly why our units are sized this way.

A 2 kW class system is roughly equivalent to one kitchen outlet in a home.
 
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john61ct

Active member
That is not a proper type of LFP bank for the use case.

Not just the crippling of C rates, but not likely to get good longevity.

And not even cheaper!

The idea that you can just "drop in" and not have to learn the details is IMO a gross deception.

Actually you can, but costs a lot to get a turnkey setup installed.
 

HarryN

Well-known member
Please bear with me- I'd like to explore a different direction than what we'd previously planned.

Instead of starting with our expected electrical usage and working forward to develop an electrical system that will supply those needs, I'd like to start (for the purpose of discussion) with the single 250A alternator of the gas Sprinter and work backwards, to see how much electrical capacity we can realize, without generator, solar, or shore power.

LiFeP04 charges faster than AGM or flooded-cell, which I would expect would reduce the amount of time that we would need to run the engine every day to recharge.

Would we need to actually drive the van to recharge, or would the stock 250A alternator put out enough at idle to power the DC/DC charger to it's full potential?

Would a larger DC/DC charger recharge the LiFeP04 battery faster than a smaller one, like using the 60A Sterling as opposed to the 30A Sterling?

FWIW, I'm spit-balling our electrical consumption at less than 100Ah per day. LED lights, one ceiling fan, cell phones, and generous use of our laptops. We would not be planning on powering an air conditioner off of this. Our stove/oven/water heater would be propane. Our largest energy hog would be our refrigerator. We're looking at the Dometic CFX 95DZW, which is rated at 1.3Ah/h in 90F ambient temperatures, with a 41F internal temperature (31.2Ah per day).

And I don't think we need a ridiculous amount of battery capacity, because we're going to be living in it full time, so we'll be able to run the engine every day and/or drive it every day to recharge.
A somewhat more accurate description of LiFe vs AGM is that the AGM needs to be regularly fully recharged, while the LiFe bank is fairly tolerant of being only partially charged.

Good quality AGMs tend to be more tolerant of abusive charge / discharge rates than LiFe.
 

john61ct

Active member
LFP has **zero** need to ever go anywhere near Full, and sitting there is harmful.

LFP has no problem with C rates **much** higher than AGM. If you use the maximum C rates AGM can accept, that is gentle usage for LFP and great for longevity.
 

hoosierrun

Active member
LFP has **zero** need to ever go anywhere near Full, and sitting there is harmful.

LFP has no problem with C rates **much** higher than AGM. If you use the maximum C rates AGM can accept, that is gentle usage for LFP and great for longevity.

Here is an official response from Battle Born regarding a "Fully Charged" LI battery (theirs).

Dianne F | Jan 4, 2019 at 5:10 pm
Hi John,

Subjecting the batteries to 14.4 volts for a few hours, even a few days will not cause damage or problems to these batteries. If you were storing these batteries for months and had this voltage then we would discourage it.

Thank you,
 

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