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Old 09-09-2020, 08:16 PM   #1
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Default Which Charges Faster?

A question - what charges coach batteries more quickly - running your motorhome engine, or connected to a generator?
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Old 09-09-2020, 08:25 PM   #2
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A question - what charges coach batteries more quickly - running your motorhome engine, or connected to a generator?

It all depends on how big the shore charger and generator are compared the alternator, cables and fusing. It can go either way, but usually in newer vans the alternator will be faster.
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Old 09-09-2020, 11:06 PM   #3
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A question - what charges coach batteries more quickly - running your motorhome engine, or connected to a generator?
What year, make & model do you have?

Has the Alternator been upgraded?

Same with Generator details.

Are you having issues with charging or just a question?
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Old 09-10-2020, 02:27 PM   #4
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What year, make & model do you have?

Has the Alternator been upgraded?

Same with Generator details.

Are you having issues with charging or just a question?
I am actually asking a question about a possible future motorhome. The chassis would be a Promaster with a 220 amp alternator.

This would be the generator - https://powerequipment.honda.com/gen...models/eu1000i

thanks for your help!
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Old 09-10-2020, 02:44 PM   #5
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I am actually asking a question about a possible future motorhome. The chassis would be a Promaster with a 220 amp alternator.

This would be the generator - https://powerequipment.honda.com/gen...models/eu1000i

thanks for your help!

The 220 amp alternator is going to be running the van also, which can be quite variable. I would expect 20-50 amps for that part of it. Factory alternators are normally good to keep under 50% of rated output for long term charging so you would have 110 amps minus the 20-50 so in the range of 60-90 somewhere. If you running anything on the 12v while driving like a frig, charging things, cooker, etc that would subtract off also.



The 1000 watt generator could do about 60+ amps with a shore charger of that capacity and fair efficiency and again would reduce with any 12v loads or AC loads on the generator.


Basically a wash on charge rate, I think with a small advantage to the alternator. The alternator is going to be much less intrusive though as you would be driving, unless you plan on idling the engine in a campsite and in that case I would chose the generator if it is allowed. Odds are that if the genny isn't allowed, idling won't be either, though.
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Old 09-10-2020, 03:30 PM   #6
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Thanks, that is very helpful. I think I will just see what I can do by idling the motorhome if and when necessary. I don't even know if it will be necessary. For the most part I'll have a small 12v compressor fridge running and not much else generally. The motorhome will also have 200 watt solar system which should also assist at least a little bit. FYI - my camping generally consists of boondocking at a race track for 2 or 3 days.
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Old 09-10-2020, 03:32 PM   #7
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It also depends on your charger that you hook up to your generator. Many AC to DC chargers have a max output in the 45A range, which is much less than the 70-90A you can expect from your alternator. If you get a beefier charger (or inverter/charger) that can supply 80A then they would be almost equal.
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Old 09-10-2020, 03:39 PM   #8
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It also depends on your charger that you hook up to your generator. Many AC to DC chargers have a max output in the 45A range, which is much less than the 70-90A you can expect from your alternator. If you get a beefier charger (or inverter/charger) that can supply 80A then they would be almost equal.

I don't think his 1000 watt generator would run an 80 amp charger by the time you put in the inefficiencies, maybe a bit more than the 60 I mentioned earlier, but would have to test.
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Old 09-10-2020, 09:18 PM   #9
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It also depends on your charger that you hook up to your generator. Many AC to DC chargers have a max output in the 45A range, which is much less than the 70-90A you can expect from your alternator. If you get a beefier charger (or inverter/charger) that can supply 80A then they would be almost equal.
Why would a charger need to be hooked up to the generator? I would just plug the coach into the generator.
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Old 09-10-2020, 09:28 PM   #10
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Why would a charger need to be hooked up to the generator? I would just plug the coach into the generator.

You plug the coach into the generator, but then it uses the shore charger in the van to charge the batteries and that is the one being mentioned as needing to be large enough. Most factory chargers aren't very big as others have mentioned.
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Old 09-10-2020, 09:36 PM   #11
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You plug the coach into the generator, but then it uses the shore charger in the van to charge the batteries and that is the one being mentioned as needing to be large enough. Most factory chargers aren't very big as others have mentioned.
The motorhome I'm considering is equipped with a Pure-sine wave 2000
watt Xantrex Freedom XC Inverter/Charger. I don't really know if that does the job adequately or not
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Old 09-10-2020, 10:03 PM   #12
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The motorhome I'm considering is equipped with a Pure-sine wave 2000
watt Xantrex Freedom XC Inverter/Charger. I don't really know if that does the job adequately or not

You would have to turn it down as it is 80 amps and would likely be too much for the 1000 watt generator. It says it can be turned down in increments so 65 or 70 amps would probably work.
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Old 09-11-2020, 12:46 PM   #13
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That is the same model of inverter/charger I have. As Booster says, you will probably want to adjust the maximum charge rate down to avoid overloading the generator.
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Old 09-11-2020, 02:40 PM   #14
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You would have to turn it down as it is 80 amps and would likely be too much for the 1000 watt generator. It says it can be turned down in increments so 65 or 70 amps would probably work.
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That is the same model of inverter/charger I have. As Booster says, you will probably want to adjust the maximum charge rate down to avoid overloading the generator.
Agree. Maybe even turn the charge rate down to less than that. At 65 amps charging, my Renogy 3000W Inverter/Charger draws 9-10 amps from my generator as shown on the Power Control System display. We're talking about a Honda 1000i generator here.
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Old 09-17-2020, 05:52 PM   #15
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I have a 2018 Banff. I once phoned RoadTrek (before the company fell apart) to ask a similar question and spoke to someone from tech. support who said he had worked on the production line. I have two 100-watt solar panels. He said they give, at most, a trickle charge. I have an underhood generator. He said that is better at charging batteries than the solar cells, but the most effective way to charge is while driving. I'm not sure whether that answers this thread's question more generally.
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Old 09-17-2020, 08:43 PM   #16
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Default A little off topic

This might be a little off topic but I have a question about battery charging. Iím looking at a way to emulate the Volt Start on the RoadTrek. Iím told to use the Viper report start system with the Smart Start option. It will start the van when the voltage on the battery reaches a selected voltage. I believe itís set to a default of just under 11 but can be changed. It also has a feature where you can set a temperature point in the van to a selected degree...say 75 degrees...and it will auto start the van to cool it off for a selected amount of time.

Anyone see an issue with this? My goal is when Iím boondocking to be able to sleep with the Dometic Penguin II AC on. Plan to have 600 ah of Lithium batteries, 600 watts of solar on the roof, a 3000 watt Victron Pure Sine inverter/charger and 60a DC-DC charger.

Trying to ditch the generator.
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Old 09-17-2020, 08:56 PM   #17
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Having owned both EU1000i and EU2200i generators, I can say with some experience that you will wish you bought the bigger one.

After adding an easy-start device to my roof air unit, I can run it off the EU2200i, which would be impossible with the smaller generator.

As others have stated, running an 80-amp charger with the EU1000i would not work.
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Old 09-17-2020, 09:11 PM   #18
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...

... Plan to have 600 ah of Lithium batteries, 600 watts of solar on the roof, a 3000 watt Victron Pure Sine inverter/charger and 60a DC-DC charger.

Trying to ditch the generator.
My first thought was, "That's an ambitious system".

Second thought, "Where is this person living?"

Third thought, "Oh, well, yeah, that explains it." (she said, from Houston)

Comment on this specific post:

If you are going to the trouble of putting that much solar on the roof of a van, you might give some thought to configuring it in the manner of a tropical roof, so that you can simultaneously enjoy solar shielding with solar charging. Tropical roofs are an Australian creation IIRC, having never caught on here, but if I were building a van from scratch, that would definitely be a configuration I would try to achieve.

Comment on a number of posts generally, as I do on every thread that suggests heavy alternator reliance:

A reminder from one who has lived through alternator failure that even with the proper Sterling in place, the charging start/stop wear and tear on the alternator can cause the clutch pulleys to fail in short order. I lost a 200A Bosch rather dramatically that way, when it was 17 months old.

I'm not saying it will happen to you, but it can be devastating if it does happen. The alternator fizzles out quietly and unannounced, your van's computer ceases to get the electrical supply that it needs to keep running, and the van can spontaneously conk out in the middle of the freeway... or in the middle of nowhere. More details here.
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Old 09-17-2020, 09:25 PM   #19
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I love the idea of a tropical-roof solar array, and plan to try it on some future vehicle. My present Sprinter already seems top heavy for some reason, so I'm reluctant to put any more weight on the roof.
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Old 09-18-2020, 02:53 PM   #20
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There are two potential pitfalls I can think of to the Viper smart-start system:

1. When the AC kicks on using battery it will drop the system voltage. This might trigger the vehicle to start even when there is plenty of battery power left.

2. LiFePO4 has a very small voltage drop over the discharge cycle. Much smaller than the voltage drop you will see when you put a large load (like AC) onto the system. I think it will be challenging to find a voltage level that accurately captures the low charge state and doesn't trigger accidentally.

What you really need is a way to get the SOC from a battery monitor and trigger off of that.


Interblog - great details with your alternator post, thank you for sharing.

Safety and redundancy is always a relative issue - your system choices can make your vehicle more or less reliable than the factory chassis. Some choices that lower reliability can be offset with choices that increase it.

In your case you have a very large lithium power bank. A fairly simple adjustment to your wiring would let you combine your chassis and house power systems so that the lithium bank would power the chassis even in the event of a total alternator failure. Not a long term solution, but enough to let you drive for 10-16 hours even using chassis AC if you started with a completely full bank. You could recharge at any campsite where you could plug in, letting you complete your trip with the reduced functionality of having to skip house AC use off of the battery pack. This would give you quite a bit of redundancy for critical functions even with a single alternator.

I still have the factory generator installed on my unit, so if I encountered this issue I would make a few quick adjustments to the wiring (I carry all the necessary tools), fire up the generator, and use my house system to power the chassis for as long as I need to drive.
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