Alternator output at idle? (2 Viewers)

[sdnative]

Does anyone know what output current the factory alternator is capable of at idle without overheating? Is there published specs or performance curves available? Test results? I searched but wasn't able to find anything specific.

2013 LC if it makes a difference.

I know that it is a temperature compensating type. I measured cold idle voltage at 13.85V and warm idle voltage at 13.4V.

I am installing a Victron 18A DC-DC charger for a 200Ah lithium battery bank. This can pull 25A from the alternator. I am slightly concerned about overheating the alternator during extended idling.

I was hoping someone would know before I bought an IR gun.

 

[TeCKis300]

Sorry I don't know the answer to your question.

Though this may ease your concerns
- I wouldn't worry about overheating or too much stress at idle vs. peak output at higher RPMs
- A 25A load should be a breeze for the system

 

[Sandroad]

First, buy the IR gun anyway! They are fun and useful. I agree with @TeCKis300 that 25A would be a breeze for the alternator at idle. I don’t have a LC specific output curve, but I know generally modern alternators can easily put out over 50% of maximum amps at idle. That’s a huge battery bank; the power equivalent of 4 big group 31 batteries. What do you need that much battery for?

 

[sdnative]

That’s a huge battery bank; the power equivalent of 4 big group 31 batteries. What do you need that much battery for?

I don't need that much battery for sure, half that size would work fine for my needs. It was a DIY project, I had fun and learned a thing or two

But it will power my loads for days, and is even capable of jump starting the truck

 

[sdnative]

Thanks guys. These are 180A alternators correct? So I could upgrade to a larger charger down the road if needed. 18A takes a long time to charge.

 

[radman]

I was considering the 30A model (even though it would need larger gauge wire), but now I’m thinking the 18A will be just fine

Edit:
Just saw your last message.
I’m sure I can do a lot of maths on my own, but do you have ballpark charge times on that 100ah battery with 18 vs 30a?

 

[sdnative]

Divide the working capacity by current to get time. Multiply this by the SoC range % (max - min),

For 100Ah battery, charging between 5%-95% SoC:

100Ah * 0.9 / 18A = ~5 hours
100Ah * 0.9 / 30A = ~3 hours.

This is the theoretical minimum time. Depending on a number of factors the charger may not put out full power for the entire duration, and this only applies to bulk charge phase. Once you get into the absorption phase, the current will taper off to maintain a constant voltage so that last few % could take longer. Look up CC-CV charge profile.

The above formula would give you a good estimate for say a 5% - 95% charge, assuming the wiring is sized appropriately.

 

[TeCKis300]

Yup, 180A stock alternator.

IMO 18amps charge rate is fine. Rather than look at time to recharge the full battery capacity from depletion, it may be more useful to look at recovery from usage. For a humongous 200Ah bank, which is larger than the one I have on my travel trailer!, it's really a unicorn among installed batteries.

Using my 100Ah Goal Zero, I do fine for my car camping trips charging at 5A or 10A rates. And this is with using high power coffee makers and George Forman's.

 

[Sandroad]

I don't need that much battery for sure, half that size would work fine for my needs. It was a DIY project, I had fun and learned a thing or two

But it will power my loads for days, and is even capable of jump starting the truck

Heck that much battery would drive the truck (for maybe a few yards!)

 

[TheGrrrrr]

Has anyone looked into or tried the 270A alternator from SDHQ? I'm thinking of upgrading to the 50A RedArc from my current 25A, for no reason at all. Also, I know somebody was working on a sealed version for the 200, but I can't seem to find the post about it.

'08-Current Toyota Land Cruiser 5.7L 270 AMP XP High Output Alternator

11352-270-XP DC Power Engineering-2008-Current Toyota Land Cruiser 5.7L 270 AMP XP High Output Alternator, 11352-27

sdhqoffroad.com

 

[BlackMammoth]

I have a 50a DC-DC charger in my offroad camping trailer and I get an honest 50 amps out of our 2018 LC @ idle.

Honestly I wasn't expecting that level of output at such low RPM but was very happy to see it. It works out really well since I put 200ah of LifePO4 batteries in the thing and they are very happy to suck up the high current until they are nearly full.

 

[sdnative]

I would expect the stock alternator to be able to handle 50A at idle, wouldn't want to go much more though.

Getting the full 50A would be dependent on the wire size from the battery/alt to the charger inputs. I would size for <3% voltage drop at full power at the input side (probably 60A+ for a 50A charger). That would probably be 2awg if you install the house battery in the back.

@BlackMammoth what size wire are you running?

 

[TheGrrrrr]

I would expect the stock alternator to be able to handle 50A at idle, wouldn't want to go much more though.

Getting the full 50A would be dependent on the wire size from the battery/alt to the charger inputs. I would size for <3% voltage drop at full power at the input side (probably 60A+ for a 50A charger). That would probably be 2awg if you install the house battery in the back.

@BlackMammoth what size wire are you running?

I have both the RedArc and the battery in back. The RedArc is wired with 2awg from the starter battery terminal fused at 40amp. I’m running 4awg the 2ft between the RedArc and the Lithium battery.

 

[sdnative]

I have both the RedArc and the battery in back. The RedArc is wired with 2awg from the starter battery terminal fused at 40amp. I’m running 4awg the 2ft between the RedArc and the Lithium battery.

That should work fine, just need to up the fuse size. Maybe double to 80A?

 

[TheGrrrrr]

That should work fine, just need to up the fuse size. Maybe double to 80A?

Do I need to be concerned about running the winch or the DIY ARB “Triple” off the starter battery when the RedArc is pulling near 50A? Maybe a simple cutuoff to the RedArc would suffice in those instances.

 

[sdnative]

Do I need to be concerned about running the winch or the DIY ARB “Triple” off the starter battery when the RedArc is pulling near 50A? Maybe a simple cutuoff to the RedArc would suffice in those instances.

Not sure what a ARB triple is. Is that the compressor? You will need to manage loads to avoid over-burdening the alternator. I think I read somewhere a good rule of thumb is no more than 50% load at idle (this may vary depending on the output curve for your alternator).

Not sure what current the compressor draws, but it would a good idea to disable the charger when you need to winch. You are probably going to increase RPMs anyway, so there will most likely be a process to follow when that need arises.

 

[TheGrrrrr]

Not sure what a ARB triple is. Is that the compressor? You will need to manage loads to avoid over-burdening the alternator. I think I read somewhere a good rule of thumb is no more than 50% load at idle (this may vary depending on the output curve for your alternator).

Not sure what current the compressor draws, but it would a good idea to disable the charger when you need to winch. You are probably going to increase RPMs anyway, so there will most likely be a process to follow when that need arises.

ARB Triple is what I call my ARB Twin and ARB Single compressors that are ‘T’d together and both running off the starting battery/alternator. Each of the three pistons has a 40A fuse if I remember correctly.
Seem if that were drawing even 2/3 of the fused total or 80A, tacking another 50A on would be a bit much. Unsure if the RedArc has been drawing a full 24A any time that I’ve used the compressor, but I suspect it has. Definitely something I hadn’t thought enough about. Now I’m even more interested in the 270A alternator.

Aside from cost, what are the downsides to a more powerful alternator? With 104k on the original, I figure it’s going to be replaced at some point relatively soon anyway.

 

[sdnative]

Hard to say without seeing the curves. The aftermarket alternator may have a higher output, but at a higher RPM. The idle performance may be worse.

If the 270A alternator uses the Toyota casing, it is possible it doesn't have adequate cooling capacity for the increased ouput.

Also keep in mind some (most?) DC-DC charger's rated power is at the output terminals. The input will be higher. For instance my Victron 18A can draw 22-25A on the input.

 

[TheGrrrrr]

Hard to say without seeing the curves. The aftermarket alternator may have a higher output, but at a higher RPM. The idle performance may be worse.

If the 270A alternator uses the Toyota casing, it is possible it doesn't have adequate cooling capacity for the increased ouput.

Also keep in mind some (most?) DC-DC charger's rated power is at the output terminals. The input will be higher. For instance my Victron 18A can draw 22-25A on the input.

This is the curve that is posted, for whatever that is worth.

 

[bjowett]

This graph from Denso shows the output for their 170 amp Poweredge Alternator, which is the same chassis we have in the LC. Unfortunately, it shows engine RPM w/o the drive ratio, most alternators run somewhere in the 2 - 3:1 range.