Varg charging from generator.

[ReVolter]

I have a small generator with an output of 110V and 20 Amps. I am thinking of adding a step-up transformer to produce the 220V at 10 Amps that the Varg like better. Has anyone tried this? It could significantly reduce the recharge time at the track.

 

[Scott]

Interesting concept. Would it have to be a split-phase step-up inverter, if there is such a thing? Also, the 110v outlet must be capable of supplying the entire 20amps.

 

[ReVolter]

The transformer would be electrically isolating so you can choose whatever ground and neutral reference you want. 220 lines in Europe still use a hot and neutral convention and which is which is random because some of the plugs are reversible.

 

[Scott]

So, you are saying that you could use a generator with a TT-30 (120v 30amp) output and run it through a single-phase step-up transformer to 220v and the charger that comes with the Varg would accept that? That would be great if that would work because it's easy to find generators with the TT-30 plug.

 

[ReVolter]

I think that should work because the 220V in Europe is single phase.

 

[Philip]

I have a small generator with an output of 110V and 20 Amps. I am thinking of adding a step-up transformer to produce the 220V at 10 Amps that the Varg like better.

You'd need a bigger ~4,000W generator because the Varg likes 220V at 16A. Then it would work.

 

[Swank171]

I have a small generator with an output of 110V and 20 Amps. I am thinking of adding a step-up transformer to produce the 220V at 10 Amps that the Varg like better. Has anyone tried this? It could significantly reduce the recharge time at the track.

You would need more amperage, the transformer will give you the higher voltage but in turn you’re going to get less Amperage. Transformer cannot give you more watts.

 

[Scott]

I am going to try the 240v inverter route. Got 5kWh worth of battery running at 48v. Tested it by charging the electric car and got about 4kWhs out of it. I figure, full Varg battery plus this will be enough for my ride time on a motocross track. I will have to dial the Varg back a little bit on the charge current but should be just fine.

 

[ReVolter]

You would need more amperage, the transformer will give you the higher voltage but in turn you’re going to get less Amperage. Transformer cannot give you more watts.

Obviously, but the changing current at 220V is only 10A according to what I have seen .

 

[ReVolter]

You'd need a bigger ~4,000W generator because the Varg likes 220V at 16A. Then it would work.

The videos I have seen are showing a max of 10 A charging, but I think you can set the charge rate to whatever you need.

 

[Duncan]

I think it’s the first law of thermodynamics that states energy cannot be created nor destroyed. You will not get more energy out of that generator by going to higher voltage watts equals volts times amps if you double the voltage, you will get half the amperage the watts remains constant maximum output

 

[Chadx]

There are a few things going on here. First, like other said, your generators max watt output is the limiting factor. Changing voltage in and of itself is not changing how many watts your generator is outputting. And, by using a voltage converter (going from 120v to 240v), you are losing even more energy due to the conversion (converters are no 100% efficient).

120v x 20amps = 2400watts
240v x 10amps = 2400watts

So in simple terms, the generators capability is identical. Now subtract 8% efficiency loss for the converter and your 2400 watts drops to 2,208watt available output.
This is strictly what the generator can output and is a separate topic than what the Varg will accept, which is yet another aspect of the subject.

The interesting part of this that may change the answer is, what is the max amps that the bike will charge at 120v? I don't recall the answer on what owners have found. If it's limiting charge rate to 10 amps on 120v and limiting to 10amps on 240v, then the bike and charger are the limiting factor, not the generator output, as you'd have unused capability from your 120v 20amp generator. But if the Varg will charge at 20amps (or close) when on 120v, then no reason to convert. I see where you are going with this, but the only reason to convert is if the Varg and charger are the limiting factor when charging on 120v; not your generator.

Sounds like the max amperage, when charging on 240v is 10amps. Before we can evaluate the pros and cons of converting, someone needs to confirm the max amps the Varg will charge when using 120v. Is this known? Is it 10amps? 15amps? 20amps? If it's the same 10amps as on 240v, then there likely is some merit to converting 120v to 240v. Then there is the issue of converting a single 120v generator to 240v. I don't think there is an easy way. Typically that requires two 120v generators designed to be run in series, that are paired together to create 240v. The most economical answer would likely be replacing your current generator with a larger generator with built in 240v capability.

Edit: Another question about your current generator. Can you really produce 120v 20amp sustained? or is that spike/max amps? What generator is it and what are the two output specs (in amps or watts)? Max sustained watts and max spike watts?

 

[ReVolter]

For a given battery resistance, R, the charging rate is V²/R so doubling the voltage cuts my charge time by 75%. Since charging on 110V takes longer than charging on 220V I can assume that the Varg charger does not have a boost converter, unfortunately. I would think that a simple transformer should be more than 92% efficient, but even so, I should still win on charging time. My generator is 2100W peak and 1700W sustained. So, I may only be able to charge at 220V and 7.7A, but it should still be faster than at 110V and 10A. I will check the the 110 charging current. If it's still limited to 10A, then the transformer will be faster. I would need about 15A at 110 to be close, but if this was the case the 110V charge time would be the same as the 220V charge time.

 

[Chadx]

Of note, the battery is charged at the exact same voltage (I don't recall the voltage) no matter if the charger is running of 120v or 240v. Battery resistance doesn't figure into this conversation because the charger charges the battery with the exact same voltage no matter which voltage the charger runs off of. Similar to how a usb charger pushes 5v to a device battery (phone, tablet) no matter if the adapter (with built in converter) is plugged into a 120v or 240v outlet.

Otherwise, the thought process behind using a converter to work around the current Varg 10amp charging limitation is a good one. But a big part of the decision will be based on max charge rate on 120v, which may change in the future. Originally Starg said 15amps (on both 120v and 240v), but it seems limited to 10 amps on both currently. If 120v is limited to 10amps, then converting will let you charge faster. But if 120v allows the full 15amps (now or in the future with an update), then 120v x 15amps is 1,800watts.

There is also the inefficiency of the Varg charger to consider. I'm not clear if, when the Varg display says 240v 10amp charge rate, if that is what the bike is receiving from the charger or if that is what the charger is drawing from it's source (and so the bike is receiving the 5% to 10% less due to the losses in the charger). But I'm assuming the display is showing the amount of power going to the battery. That means the charge is drawing a % more than that due to charger losses. I bring that up because if your generator has a max output of 1700watts sustained, you can't set the bike to that exact 1700watt rate because the bike charger, and your converter, will have losses. You'd mentioned 7.7amps if converted to 240v. You won't be able to set the bike to 7.7amps or your generator will be overdrawn. Even if the converter losses are only 5% (I think it will be more), that means your sustained output is reduced by that 5% and then another 5% on top of that for Varg charger losses.

We'll use watts to keep it simple. Working backwards from your generators, sustained 1,700 watts max, 5% converter loss brings that down to 1,615 watts. Then another 5% loss from the Varg charger brings that down to 1,534 watts sustained that can flow to the battery without overloading your generator. 1,534watts / 240v = 6.4amps so 6.4amps would be the max you can set the battery charge rate to not trip your generators safety. That calculation will depend on the exact losses of the converter and the charger, but easy enough to plug in those numbers when you find them out.

By comparison, if you don't use a converter, you'll have only the 5% loss from the Varg charger. 1700w turns to 1,615watts. So the Varg charger would have to allow 1,615w / 120v = 13.45amps charging on 120v to break even with the max your generator can produce if using a 240v converter. If the Varg does allow 13.45amp charge rate on 120v (today or with future update), then charging on 120v would charge as fast as with your converter to 240v. If the Varg only allows a max of 10amp charge rate on 120v (today and in the future), then it is capping the current that is getting to the battery 1,200watts. For comparison, the 240v converter, as calculated in the previous paragraph, would be able to push 1,534watts to the battery. You'll charge 1.28x faster with your 240v converter. Probably worth it. But if Varg charger will allow a 13.45 amp charge rate on 120v, now or in the future, then no reason to mess with a converter.

All that being said, if you are going to spend money on a converter and only get 22% faster charge rate, it seems a better use of money is to sell your current generator and take the money from that and the money that you would have spent on a converter, and put it towards a generator capable of 240v and output of 4,000 or more watts. Then you can charge at 240v x 10amp = 2,400 watts now, which is 2 times faster than 1,200 watts and 1.56 times faster than even your current generator converted to 240v. And, if Varg does an update to allow 240v x 15amp = 3,600watt charge rate, you'll already have the generator and will be faster still. Except for a bit more expense and a bit more weight, there is only upside to the larger generator. It will charge your Varg as fast and possible, will give you a lot more power for household and remote uses, have both 240v and 120v plugs, etc.

 

[F451]

All that being said, if you are going to spend money on a converter and only get 22% faster charge rate, it seems a better use of money is to sell your current generator and take the money from that and the money that you would have spent on a converter, and put it towards a generator capable of 240v and output of 4,000 or more watts. Then you can charge at 240v x 10amp = 2,400 watts now, which is 2 times faster than 1,200 watts and 1.56 times faster than even your current generator converted to 240v. And, if Varg does an update to allow 240v x 15amp = 3,600watt charge rate, you'll already have the generator and will be faster still. Except for a bit more expense and a bit more weight, there is only upside to the larger generator. It will charge your Varg as fast and possible, will give you a lot more power for household and remote uses, have both 240v and 120v plugs, etc.

I agree with this strategy. I liked the B&S Q6500 for my Alta, its now my home backup power generator.

Ps: so many maths in these posts, Lol.

 

[ReVolter]

I looked into the Varg battery and it is a 420 V unit. This probably means that the charger is a boost converter and can take either 110 or 220 inputs. Both residential services are limited to 15A, so that is why it takes 2 hours at 220V x 15A to charge the 6480Wh battery. This puts the charge time at 4 hours for 110V. A transformer won't make a difference. The current shown on the charging display is probably the current to the battery. When charging from 220V the current will be roughly 7.7A and for 110V, 3.85A.

 

[EDR1]

I have a small generator with an output of 110V and 20 Amps. I am thinking of adding a step-up transformer to produce the 220V at 10 Amps that the Varg like better. Has anyone tried this? It could significantly reduce the recharge time at the track.

That’s a slow charge. Varg & Alta both use the same Elcon 3.3KW charger. So the generator requires a generator with an inverter for a pure sine wave output with a constant 3.3KW output (not including the inefficiency of the Elcon) I use a Briggs & Stratton Q6500 (6500 watts peak) abt 95lbs enclosed. Chosen after staring at this forum for a couple hours to see what everyone likes the best for size,weight,reliability,quality,noise. Not CA compliant so bought one used on FB marketplace (in so-called “excellent-like-new condition” and paid to ship it across the state to deliver it) the. threw a few hundred into it to fix the oil leak and clean the carb, filters, gaskets, spark plug, outlets… LOL) Could have / should have driven to Reno and bought it new at Home Depot. but at least I got what I wanted (just like my Alta story.)

 

[ReVolter]

I finally got to ride my Varg. The result was a bad news/good news result. I tested it out on a sand track and it chewed through the battery much faster than I expected. However, I was able to recharge it with my tiny 1700W 110V generator in reasonable time. If I recharge on every break of casual riding I should be able to get a day's worth of riding out of it. I hope I can get better battery life on a dirt track. I made my own 110V to 220V adaptor for about CN$20, so you don't have to pay big $ for the official Stark one.

 

[Theo]

Some days ago I wrote, on this forum, that a power station would have been too expensive and that a generator would have been a more sesnsible choice instead, but I made a small mistake: I didn't check the typical efficiency of a generator.
According to a quick search, it seems that, in order to produce the 6.5 kwh needed for our battery, just to have a reference, we would need to use about 1.3 gallons, or 5 liters, of gasoline, which, at least here in Italy, would not be that cheap: it would cost 9 €. Besides, I think that one should also consider the way in which the required power affects efficiency, because I suspect that a 3.3 kw capable generator doesn't have the peak efficiency at 3.3 kw, so maybe in order to get 3.3 kw it would be wiser to choose for example a 5 kw capable generator.
I've also found out (didn't know much about generators before) that there are generators which can use propane gas or both propane and gasoline.

Therefore, I would be grateful if I could have the following information by whomever uses a generator to charge the Varg or to power anything else needing 220V AC:
• which generator you have,
• whether you use gasoline or propane in it,
• how much gas/propane it takes to produce what amount of kwh,
• at which power you get that fule/kwh ratio.