FitRV's lithium/alternator/inverter setup

[avanti]

Originally Posted by booster

I have no idea how they could limit the output of the MB to 25 amps, though.

Coachmen is a Mercedes "Master Upfitter", so they must be doing it somehow.

[Davydd]

Originally Posted by avanti

Coachmen is a Mercedes "Master Upfitter", so they must be doing it somehow.

Of course, the Sprinter alternator always could charge your coach batteries. But if you have a second alternator it could be simpler to avoid MB's alternator and their local interface network regulator which has restrictions. One such restriction is the alternator needs to satisfy the chassis and engine needs first and if I am reading the BEG right they limit current to additional batteries to 40 amps and have other restrictions like battery type, wiring, fuses, etc. When you have a second alternator capable of 270-330 amps why bother unless the connections are already there and convenient to use and follow their guidelines?

You can access the Body and Equipment Guidelines (BEG) here:

https://www.upfitterportal.com/en-us/

[prfleming]

Originally Posted by avanti

As ARV has demonstrated, one add a mighty big alternator if it is really needed.

Interesting video on what's new for 2017. ARV is implementing an all 48V house system. He mentions running the A/C 7 hours, and having 94% remaining battery capacity. Wow.

https://youtu.be/rNmX11blPRg

[avanti]

Originally Posted by prfleming

Interesting video on what's new for 2017. ARV is implementing an all 48V house system. He mentions running the A/C 7 hours, and having 94% remaining battery capacity. Wow.

https://youtu.be/rNmX11blPRg

Well, yeah, it did sound like he said that, but I think he inadvertently conjoined two independent thoughts. The claim is otherwise implausible. It would imply that the a/c could run for almost 5 days continuously. Yes, that would count as "wow". But it ain't going to happen this decade.

[BBQ]

Originally Posted by avanti

Well, yeah, it did sound like he said that, but I think he inadvertently conjoined two independent thoughts. The claim is otherwise implausible. It would imply that the a/c could run for almost 5 days continuously. Yes, that would count as "wow". But it ain't going to happen this decade.

+1

[Davydd]

Advanced RV has a 48v (actual 56v) Volts Power Systems installed in a van and they are testing it thoroughly. They also have a new air conditioner under testing that is much efficient than the Coleman Mach 8 they have been using. Of course it depends on the size of your battery bank in how long you can run. But they can charge at over 500 amps per hour with the Volta system to replenish lithium ion batteries. They've gone way beyond the Nations alternator and now even the Delco alternator they are currently using. The point is you can survive in the heat a lot longer off grid like no other Class B.

[GeorgeRa]

Originally Posted by Davydd

Advanced RV has a 48v (actual 56v) Volts Power Systems installed in a van and they are testing it thoroughly. They also have a new air conditioner under testing that is much efficient than the Coleman Mach 8 they have been using. Of course it depends on the size of your battery bank in how long you can run. But they can charge at over 500 amps per hour with the Volta system to replenish lithium ion batteries. They've gone way beyond the Nations alternator and now even the Delco alternator they are currently using. The point is you can survive in the heat a lot longer off grid like no other Class B.

"500 amps per hour at 56v", wow, impressive.

[booster]

Something is wrong with the numbers stated here, I think. Volta lists their alternator at 191 amps at 54 volts, and it is using 20hp at that point. That would be equivalent to nearly 800 amps at 12v, but nowhere near 500 amps at 54 volts which would use 50 hp off the engine based on their spec.

They do say they can recharge most of their systems in two hours. Their approx 20K w-hr system would be equivalent to something like 1750ah of 12v power if I did the calcs right. That matches their two hour charge time statement.

I think folks are getting amps and amp-hours mixed up again or something. Unless ARV is getting something that is not listed on the Volta site. I don't think a Sprinter could spare 50hp anyway, and it would be very hard on the front main bearing, I would think, unless more support was added.

[Davydd]

I get a charge rate off my Delco alternator of about 280 amps. The Advanced RV video stated they were getting over twice the charge rate with the Volta systems.

[avanti]

I think it may be time to switch from amps to watts.

[prfleming]

Right. The confusion is comparing 56V to 12V (approx 14V charging).

The Volta alternator is rated at 191 amps ~ 10,600 watts
The Delco alternator is rated at 320 amps ~ 4500 watts
The Nations alternator is rated at 270 amps ~ 3800 watts

So the Volta is a little over twice the wattage compared to the Delco.

I would say the Delco is an incremental improvement over the Nations. The Volta is a game changer.

[Luv2Go]

10KW! That's almost the power you get from a 50A RV connection! Definitely a game changer. Can't find it now, but someone just announced a new model with a 48V electrical system. I believe it was a so-called mild hybrid. All accessories were powered by the 48V, no belt-driven devices at all. Of course, lack of a belt would make it hard to add a belt driven second alternator!

[booster]

I wonder what MB is saying about loading a Sprinter with 20 hp of load at idle, for extended times?

IIRC, the Warp Core is also right about 20KWh, so similar on battery bank size. That would also imply similar run times for the AC to the Warp Core.

[booster]

Originally Posted by avanti

I think it may be time to switch from amps to watts.

I am with you on that. We keep hearing amps used for amp-hours all the time, and now we have a new term thrown in as "amps per hour" which I think is supposed to also mean amp-hours.

Of course if we switch, then we will likely just have the same confusion between watts and watt-hours.

[avanti]

Worth noting that 10K watts is more than 13HP -- before the very significant mechanical and electrical losses. So Booster's calculations are very plausible.

[booster]

I got the 20hp off this chart for the 191 amp alternator on the Volta site.

[GeorgeRa]

I bought 115 amps battery, it uses 15 amps per day……. very common mistakes in RV world, now we adding mixed voltages. Even Ah unit is not correct, it assumes voltage, it should be Ax12Vh which is Wh.

Extra 5-10kW taken from the front pulley is significant, I assume it is driven by a separate serpentine belt. If this number will continue to go up it almost calls for a PTO.

[booster]

Originally Posted by GeorgeRa

I bought 115 amps battery, it uses 15 amps per day……. very common mistakes in RV world, now we adding mixed voltages. Even Ah unit is not correct, it assumes voltage, it should be Ax12Vh which is Wh.

Extra 5-10kW taken from the front pulley is significant, I assume it is driven by a separate serpentine belt. If this number will continue to go up it almost calls for a PTO.

Yep

20 hp is a lot of power to take off an overhung load like is done with accessory belt drive. The front main bearing of the engine actually sees more side load than the belt drive tension and the second main sees the difference. PTOs, as far as I know always use a totally self supporting unit and a shaft to the engine, so the engine sees only torque and not sideload. Hopefully, they are looking at the issue and adding an outboard bearing or something like it.

A true PTO setup would be really slick

[prfleming]

Umm, I think think we are worrying too much about this pulley side load.

The high power alternators use a wider serpentine belt, more grooves, more friction. Belt tension is the same or similar to the std alternator, just more torque delivered with a heavier belt.

[avanti]

Originally Posted by prfleming

Umm, I think think we are worrying too much about this pulley side load.

The high power alternators use a wider serpentine belt, more grooves, more friction. Belt tension the same as std alternator, just more torque delivered with a heavier belt.

I don't follow your reasoning. If there is more torque, how could the belt tension be the same? I suppose that could be true if they used very large pulleys, but I don't think that is the case.