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Old 08-23-2016, 02:47 PM   #1
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Default underhood generator

I am considering the purchase of a Roadtrek Zion with the underwood generator. Since this seems to be fairly new I wonder if anyone has any experience with these generator, both good or bad?
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Old 08-23-2016, 03:13 PM   #2
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I am considering the purchase of a Roadtrek Zion with the underwood generator. Since this seems to be fairly new I wonder if anyone has any experience with these generator, both good or bad?
I have a zion with this works fine. i have the standard agm battery

However it is not actually a generator.

it is an extra large second alternator feeding battery and a 2000 watt inverter in the zion
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Old 08-23-2016, 03:19 PM   #3
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Default underhood generator

Do the batteries in the zion provide enough power for the AC and the Microwave?
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Old 08-23-2016, 03:25 PM   #4
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Do the batteries in the zion provide enough power for the AC and the Microwave?

"It depends" is the standard answer.

It depends on how many batteries you purchased.
It depends on how long do you want to run the AC.
It depends on... a lot of things.

Roadtrek provides a document called "Power Budgeting Guide".
You can use it to calculate your supply and demands.


Modern day RV has a lot of technologies.
It can provide many creature comfort and conveniences.
Unfortunately it is not an appliance yet.
ie it does not operate like your toaster (one touch / plug and play),
and the relationship between the components is complicated.


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Old 08-23-2016, 03:47 PM   #5
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"It depends" is the standard answer.

It depends on how many batteries you purchased.
It depends on how long do you want to run the AC.
It depends on... a lot of things.

Roadtrek provides a document called "Power Budgeting Guide".
You can use it to calculate your supply and demands.


Modern day RV has a lot of technologies.
It can provide many creature comfort and conveniences.
Unfortunately it is not an appliance yet.
(ie it does not operate like your toaster, and the relationship is complicated)


since i actually have a zion with it's standard tppl agm battery-the answer is yes- it runs all 120 volt devices in the van. However since the inverter is only 2000 watts you can actually only run 1 hight wattage device at a time.

you can run the air conditioner-however since the agm battery is 186 amp hours it's about 1/2 hour max if not running underhood alternator.

you can run microwave but not at same time as AC- will over power inverter and have to reset.

as long as you don't go over say 1800 watts-thats my guideline you can run anything but not multiples

the inverter has a 3x surge capability for overcoming initial start requirements
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Old 08-23-2016, 04:53 PM   #6
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One thing i forgot to mention-if you are plugged in the converter/inverter/charger which is one device allows full 30 amp pass thru power. the inverter part does not function when plugged in since full 30 amps is being passed thru.

because it is one device and has to be turned on for the converter/charger part to be functioning-people think they are running on inverter when plugged in and they are not.

the inverter senses when on shore power and is not functioning

you can use muptiple 120 volt devices up to 30 amps of shore power at the same time
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Old 08-23-2016, 05:22 PM   #7
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and for those trying to calculate- 1000 watts is 8.3 amps at 120 volts, usually round up to make up for resistance in wiring or switches or...

a 30 amp service is good for 3600 watts on paper but practically maybe 3300 watts

the 1800 watt inverter above is 15 amps- which is same as most household outlets are rated.

we use ohms law to calculate these and online calculators abound

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Old 08-23-2016, 05:39 PM   #8
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The engine generators work fine for most. The questions relate mostly to what control systems and battery packs. The lithium packs in Roadtreks have huge parasitic losses, so that would need to be considered. The AGMs won't have that issue, but also won't recover from the engine generator as quickly or be as able to run big loads as long.

Air conditioning is nearly out of the picture unless you are willing to run the van engine near 50% of the time, from what we have heard from Zion owners.
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Old 08-23-2016, 06:18 PM   #9
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As Gerry and Booster say, it's all about the configuration and the demands you have. These rigs will not boondock for long periods of time, especially with a/c required, unless you run the engine.

I'm just back from a 4 day park-up in my CS (8-agm variety) at my daughter's non-electric cabin. We were fine, and used the CS to run 110v fans in the cabin as it was 100 in the day. Plus my reefer worked hard, we ran the Keurig a lot, along with fans in the rig itself. Only used the a/c a little bit. (Fortunately it cooled off at night.)

On day 3 I ran the engine 40 minutes to bring the pack from 61% to 93%.

Only after you assess your travel/camp plans can you decided on these rigs. If I needed a lot of a/c, I'd favor a standard generator.
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Old 08-23-2016, 06:30 PM   #10
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As Gerry and Booster say, it's all about the configuration and the demands you have. These rigs will not boondock for long periods of time, especially with a/c required, unless you run the engine.

I'm just back from a 4 day park-up in my CS (8-agm variety) at my daughter's non-electric cabin. We were fine, and used the CS to run 110v fans in the cabin as it was 100 in the day. Plus my reefer worked hard, we ran the Keurig a lot, along with fans in the rig itself. Only used the a/c a little bit. (Fortunately it cooled off at night.)

On day 3 I ran the engine 40 minutes to bring the pack from 61% to 93%.

Only after you assess your travel/camp plans can you decided on these rigs. If I needed a lot of a/c, I'd favor a standard generator.
Those recharge numbers are kind of interesting, and puzzling, to me.

32% of 800ah is 256ah, in 40 minutes of idling. That would convert to 384ah per hour, so you had to average 384 amps of charging at idle to get that kind of recovery. Plus, once you get past about 70%, the acceptance rate of the AGMs starts to drop very quickly, so it would limit how much was recovered.

How big is your engine generator and what kind of a monitor are you using?

I would agree with having a standard generator if someone wanted a regular use of AC.
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Old 08-23-2016, 06:54 PM   #11
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Those recharge numbers are kind of interesting, and puzzling, to me.

32% of 800ah is 256ah, in 40 minutes of idling. That would convert to 384ah per hour, so you had to average 384 amps of charging at idle to get that kind of recovery. Plus, once you get past about 70%, the acceptance rate of the AGMs starts to drop very quickly, so it would limit how much was recovered.

How big is your engine generator and what kind of a monitor are you using?

I would agree with having a standard generator if someone wanted a regular use of AC.
the engine generator system at 40 miles per hour is probably around 300 dc amps. at idle probably closer to 120
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Old 08-23-2016, 07:05 PM   #12
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If your SOC percentages are based on your usable battery amp hours then that could be just a little over 200ah to make up assuming you have 640ah of useable if you draw down to a 20% limit.

640 x .32 = 204

That might be doable. 91% is not fully charged so would that be bulk charging only?

No way is a Nations alternator going to produce 300 amps at 40 mph.
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Old 08-23-2016, 07:08 PM   #13
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You guys can debate the different ways to monitor. I just read the % off the inverter screen, which is good enough for me. I'm simply explaining "real world" usage.
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Old 08-23-2016, 07:41 PM   #14
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You guys can debate the different ways to monitor. I just read the % off the inverter screen, which is good enough for me. I'm simply explaining "real world" usage.
Not debating how to monitor being good or bad either way, but felt it would be of good interest to you to point out that it appeared to not be physically possible to gain that much power, in that short a time, at idle. I don't have any idea what the monitor is, or how it is programmed, and that is why I asked. It doesn't matter how it is done, but it is pretty necessary to know how is set up if you want any kind of accuracy.

If you expand on davydd's example, and the monitor is programmed at 50% of total AH for the max use, you are leaving a lot of usable capacity on the table, that could save you running the engine as much. If it is at 50%, then that would make the recharge within what might be possible in 40 minutes, so then the physics works better. If you have that extra capacity, just thought you might want to know it, and also what the % readings you are seeing are actually telling you.
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Old 08-23-2016, 08:17 PM   #15
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If your SOC percentages are based on your usable battery amp hours then that could be just a little over 200ah to make up assuming you have 640ah of useable if you draw down to a 20% limit.

640 x .32 = 204

That might be doable. 91% is not fully charged so would that be bulk charging only?

No way is a Nations alternator going to produce 300 amps at 40 mph.
whats 3500 watts . i think on all models except zion both alternators give some amps
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Old 08-23-2016, 08:50 PM   #16
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I would suspect that the % capacity display from the inverter is not likely to be very accurate. It is not going to be based on a shunt reading and has no info on what the underhood generator is doing in terms of charge amps. Not sure how it calculates state of charge with these limits on available data but likely not very accurate but it is what is available...
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Old 08-23-2016, 09:24 PM   #17
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I would suspect that the % capacity display from the inverter is not likely to be very accurate. It is not going to be based on a shunt reading and has no info on what the underhood generator is doing in terms of charge amps. Not sure how it calculates state of charge with these limits on available data but likely not very accurate but it is what is available...
That makes sense, and would tie into Roadtreks history of very poor information concerning state of charge. It does make it look like system is doing an incredible job of recharging in a short time, though, which is probably what Roadtrek wanted, even if not very accurate .
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Old 08-23-2016, 10:54 PM   #18
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whats 3500 watts . i think on all models except zion both alternators give some amps
Roadtrek has a historical penchant for exaggeration and slight of hand waving with numbers. Do you know that for a fact or are you just assuming? I would say odds are if they don't do it with a Zion as you said that they certainly would not with a Sprinter. Even so, I still doubt 300 amp charging.
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Old 08-24-2016, 12:41 AM   #19
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The % SOC shown on the inverter in my E-Trek is, as far as I can tell, just a voltage meter with unknown calibration to generate % SOC. It is prone to the same inaccuracies as all voltage meters. The inverter screen alternates between the % SOC display and an integer voltage display, which is pretty much useless. I wish there was a way to install a shunt-based amp meter on an 8 AGM E-Trek, but my understanding is that this is not feasible with two grounds.
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Old 08-24-2016, 01:10 AM   #20
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Roadtrek has a historical penchant for exaggeration and slight of hand waving with numbers. Do you know that for a fact or are you just assuming? I would say odds are if they don't do it with a Zion as you said that they certainly would not with a Sprinter. Even so, I still doubt 300 amp charging.
zion battery just gets charged by 'engine generator'

all other models use bothalternators -that was what i was told
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