Beefy AUX alternator installed. No power pulling away, then surge of power. Normal?

VanGoSki

Well-known member
Your pulley looks visibly smaller. They may be using the smallest pulley possible to maintain a certain RPM at idle. Maybe the 24V is more sensitive to that. It will be interesting to see what they say.
 

WT1J

Member
Makes sense. I've sent Nations an email to try to find out if they think a clutch is needed and whether it's an option. This alternator apparently also has an option to detune it so that it produces less current (and load) at engine idle and then ramps it up as the RPMs increase. I've asked them if this is an option and for more info. It may provide us with more power during initial pull away while the alternator is producing current.
 

VanGoSki

Well-known member
That's a thought. It may be a regulator option.

Remember too that your battery is going to charge very quickly with this set up. So for the vast majority of time, the regulator isn't going to be calling for power and your alternator won't be loading your engine.
 

WT1J

Member
The van has an unusually high battery capacity and unusually high power delivery capability. It's a 800AH bank of 24 volt batteries. Equivalent to 1600 amp hours at 12 volts or 19,200 watt hours.

We have the ability to pull 8,000 watts continuously from the batteries with 10,000 watts peak We're using dual Victron Quattro inverters:


It's a film truck with quite a few 20 amp AC circuits inside and out that let us fully utilize the available power. So it's quite possible for us to run them down to zero in just over 2 hours.

At 3KW alternator output it'll take over 6 hours to charge them up assuming 100% efficiency, so maybe more like 9 hours.

Typical use will be driving to shoot location, parking and turning off van. Using the heck out of the batteries and hopefully not running out of juice. Then packing up and driving to home base. Supplementing any remaining charge time needed with shore power on arrival back at home base.

She'll be doing quite a lot of highway miles for remote shoots - over 1000 mile trips regularly. So we may see for example a 6 to 9 hour charge time for an entire day trip leg. And then have that scenario repeat fairly often.

~Mark.
Edited for clarity.
 

VanGoSki

Well-known member
Wow, that's pretty cool. Is all that power for video lighting? Or maybe satellite transmission? I figured you had about half that amount of storage.

I believe you can expect your efficiency to be 100% with this setup. Unless I'm missing something, your batteries will have a direct connection to your alternator so there are no losses to factor in. 100 amps generated will be 100 amps stored.
 

WT1J

Member
Thanks. Yes it's mostly for lighting, which has become much more efficient since LEDs have gotten to a point where they are good enough (have a high enough CRI/TLCI for film). Used to be that you'd need a generator truck to power 12 kilowatt units. Also it will have on the road production capability with a little workstation inside the van and that needs power. But the majority is lights and other on-set power like powering video village.

The van isn't for live broadcast - it's for film making. And so no live satellite links.

Yeah agreed that the efficiency will be better than I indicated - we are running lithium and that's pretty much linear when charging up compared to lead acid. So it's mostly down to resistance in terms of losses I'd think.
 

autostaretx

Erratic Member
If i'm reading the photos correctly, your green belt is (properly) coming from a second pulley sheave on the crankshaft.

The "sprag clutch" is to allow the alternator(s) to *continue to coast* when the engine slows down abruptly.
It does not affect "push back" (which i translate as "resistance to forward motion").

By allowing the alternator to coast, it's not reversing the direction of "power flow" that the belt is carrying.
(switching from "engine pulling alternator" to "alternator pushing belt to try to get the engine to go faster")
Many of the "wrap angles" and tensioner designs are not really prepared for that reversal.

For a dedicated belt like the Nations', it's probably OK. (versus the "powers everything" serpentine)

--dick
p.s. although i'm an electrical engineer, i'm well aware of the mechanical engineers' credo of "F=M*A" and "you can't push a string"
 
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WT1J

Member
If i'm reading the photos correctly, your green belt is (properly) coming from a second pulley sheave on the crankshaft.

The "sprag clutch" is to allow the alternator(s) to *continue to coast* when the engine slows down abruptly.
It does not affect "push back" (which i translate as "resistance to forward motion").

By allowing the alternator to coast, it's not reversing the direction of "power flow" that the belt is carrying.
(switching from "engine pulling alternator" to "alternator pushing belt to try to get the engine to go faster")
Many of the "wrap angles" and tensioner designs are not really prepared for that reversal.

For a dedicated belt like the Nations', it's probably OK. (versus the "powers everything" serpentine)

--dick
p.s. although i'm an electrical engineer, i'm well aware of the mechanical engineers' credo of "F=M*A" and "you can't push a string"
Yes thanks. I understood this to be the case. Sorry if I gave you the impression I thought my alternator was going to assist my engine or something along those lines. Understood that the goal is to reduce wear on the belt by allowing coasting.
 

Eric Experience

Well-known member
Wti.
You should get a sprag fitted, the sprag is not there for sudden slowing of the alternator, that is a common misunderstanding, the crank is like a torsional spring it flexes back on compression and then flexes forward on firing, the angles are only a few degrees but it happens twice in each revolution, typically 8 thousand times a minute, that generates a lot of heat and loss of efficiency. you have paid good money to get this installation you should get it done correctly. It is a sad fact that companies will try to take short cuts and rely on there customers to do the quality control. Eric.
 

Boxster1971

2012 Sprinter 3500 Ext
Hi all,

2021 Sprinter 3500XD 4x4 170" wheel base with MBUX package. Rear of the van is an empty metal box without anything in it. We're turning it into a film truck. . . . . The vehicle is brand new and we only received it a few days ago, so I'm sure we'll have much more data as the week progresses.

Thanks,

Mark Maunder.
Mark - is your van really a 2021 model or a 2020. Several threads on this forum indicate the V-6 diesel and 4X4 are not yet available on the 2021 models. Searching various dealer inventories in my area - I could find no 2021 models, only 2020.

Edit: Just saw your answer in another thread - you have a 2020 model as I thought.
2021 Sprinter | Sprinter-Source.com (sprinter-source.com)
 
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Beach2Snow

New member
Hi Mark, I don't mean to de-rail the conversation.

I am building a similar set up (not nearly as big) using the nation's 24v dual alternator.

I am assuming you are using the Balmar MC-624. Can you share what other components you are using to communicate with and monitor the alternator charge rate?
 

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