joer
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For anyone that’s interested, here’s my setup for topping up my Varg at the track. I didn’t really want to deal with the maintenance and fuel on a gas generator. I got the Varg because I was sick of changing oil and cleaning air filters. 
So I went for an external battery instead.
I had posted this on Facebook, but that’s such a lousy medium for referencing something like this.
Please note: I’m not an electrician, so I’ve likely done something ill-advised here. Don’t take my word as gospel.
I bought a 5KWh 48V LiFePo4 battery off AliExpress along with a 5KW 48v to split-phase 240V inverter. It’s enough that I can comfortably run the bike’s charger at full speed in between sessions at the track.
At max charging speed, I’m pulling about 75 Amps at the 48V battery, so I only get to use about 80% of the battery’s rated capacity before the BMS shuts it down. It’s about 60-ish minutes of charging at full speed. I could slow down the charge rate on the Varg and probably get more out of the battery, but I don’t really need it.
The inverter has 2 sets of North American 120V outlets on the back, each 180 degrees out of phase with the other. I bought a Y-adapter that let me recombine them into a single 240V NEMA L14-30 plug which the Stark plugs into nicely.
I also bought a pair of pre-crimped 2 AWG cables with Anderson connectors that make it super easy to connect and disconnect the DC side of things. I bought a much smaller set of wires that I wire up to the inverter’s pre-charge resistor. I plug that one in first, wait 10 seconds for the capacitors to fill, and THEN plug in the large cables. Otherwise, you get one hell of a SNAP.
The battery came with a 48v charger, but it was defective. I ended up buying my own 15 Amp charger which will easily fill the battery overnight.
This setup lets me keep the Varg’s battery in that sweet spot for NMC batteries, between 40-80%. (Honestly, the battery will likely outlast the rest of the bike by a long shot. I'm just mildly neurotic.) The LiFePo4 battery is much more durable so I’m more willing to push it harder (charing to 100% and running it till it shuts down). I leave all this in my trunk while at the track and the cable from the Varg charger is sufficient to reach without the need to extension cables.
I’ve found a single charge on the Varg just a little lacking for riding intermediate pace MX at a fairly muddy track an 48 HP. But not by much. With the extra battery I get all the riding I care to have for a day and still head home with 40-50% on the Varg.
It’s not a cheap setup. But a generator that can feed the Varg at full speed isn’t cheap either. And I didn’t want to go back to changing oil and cleaning air filters. This setup is also helpful at other times. Say the power goes out, I can keep my fridge running for a good long while or whatever. Or at least, that's how I'm justifying this to myself.
I should really have a fused link on the DC side of things if I wanted to be safer. At the moment, I’m relying on the battery’s BMS to shut down if things go too nuts.
I’ve now bought two such batteries. I over-reacted when I saw the first couple of reviews come out (my local track had not yet opened) and pro guys were tearing through the battery really fast. Since it takes months to get a battery from China, I ordered a second. Turns out that’s super-overkill for my use case. But now I've got an absurd amount of extra juice if I take both with me. Might be good for a race weekend or something. Who knows.
What I can tell you is these batteries are cheaply made and vary a lot between one and the next. My second battery had very poorly balanced cells and I was initially only able to pull about 54% of rated capacity before the BMS shut down the battery. The batteries have a passive cell balancer, but it takes a VERY LONG TIME to do it’s job. In this case, months. But after cycling this battery two dozen plus times, I’m now able to pull about 75% of the rated capacity and it’s still getting every-so-slightly better every time. (I’m tracking this.). I think the best I can hope for is about 85% when charging the Varg at full speed.
The upshot is: Don’t expect to pull 5KWh from a battery this cheap right out of the box. And the tech support is all chat-based and run through Google Translate. TLDR: Buyer beware.
The batteries are about 80lbs each and come with convenient handles. The inverter is about 45lb and is a bit awkward to move about.
URLs for the bits needed. I make ZERO claims for any of these products or sellers, other than they all worked for me. The battery took 3-4 months to arrive from China.
48V Battery and Inverter
https://www.aliexpress.com/item/1005005738601747.html
https://www.aliexpress.com/item/1005006042570368.html
48V Charger
https://www.canbat.com/product/48v-15a-lithium-battery-charger-lifepo₄/
Pre-crimped cables:
https://www.amazon.ca/dp/B09GV5T4MT
https://www.amazon.ca/gp/product/B094MH318S
https://www.amazon.ca/gp/product/B08V1629L1
So I went for an external battery instead.I had posted this on Facebook, but that’s such a lousy medium for referencing something like this.
Please note: I’m not an electrician, so I’ve likely done something ill-advised here. Don’t take my word as gospel.
I bought a 5KWh 48V LiFePo4 battery off AliExpress along with a 5KW 48v to split-phase 240V inverter. It’s enough that I can comfortably run the bike’s charger at full speed in between sessions at the track.
At max charging speed, I’m pulling about 75 Amps at the 48V battery, so I only get to use about 80% of the battery’s rated capacity before the BMS shuts it down. It’s about 60-ish minutes of charging at full speed. I could slow down the charge rate on the Varg and probably get more out of the battery, but I don’t really need it.
The inverter has 2 sets of North American 120V outlets on the back, each 180 degrees out of phase with the other. I bought a Y-adapter that let me recombine them into a single 240V NEMA L14-30 plug which the Stark plugs into nicely.
I also bought a pair of pre-crimped 2 AWG cables with Anderson connectors that make it super easy to connect and disconnect the DC side of things. I bought a much smaller set of wires that I wire up to the inverter’s pre-charge resistor. I plug that one in first, wait 10 seconds for the capacitors to fill, and THEN plug in the large cables. Otherwise, you get one hell of a SNAP.
The battery came with a 48v charger, but it was defective. I ended up buying my own 15 Amp charger which will easily fill the battery overnight.
This setup lets me keep the Varg’s battery in that sweet spot for NMC batteries, between 40-80%. (Honestly, the battery will likely outlast the rest of the bike by a long shot. I'm just mildly neurotic.) The LiFePo4 battery is much more durable so I’m more willing to push it harder (charing to 100% and running it till it shuts down). I leave all this in my trunk while at the track and the cable from the Varg charger is sufficient to reach without the need to extension cables.
I’ve found a single charge on the Varg just a little lacking for riding intermediate pace MX at a fairly muddy track an 48 HP. But not by much. With the extra battery I get all the riding I care to have for a day and still head home with 40-50% on the Varg.
It’s not a cheap setup. But a generator that can feed the Varg at full speed isn’t cheap either. And I didn’t want to go back to changing oil and cleaning air filters. This setup is also helpful at other times. Say the power goes out, I can keep my fridge running for a good long while or whatever. Or at least, that's how I'm justifying this to myself.
I should really have a fused link on the DC side of things if I wanted to be safer. At the moment, I’m relying on the battery’s BMS to shut down if things go too nuts.
I’ve now bought two such batteries. I over-reacted when I saw the first couple of reviews come out (my local track had not yet opened) and pro guys were tearing through the battery really fast. Since it takes months to get a battery from China, I ordered a second. Turns out that’s super-overkill for my use case. But now I've got an absurd amount of extra juice if I take both with me. Might be good for a race weekend or something. Who knows.
What I can tell you is these batteries are cheaply made and vary a lot between one and the next. My second battery had very poorly balanced cells and I was initially only able to pull about 54% of rated capacity before the BMS shut down the battery. The batteries have a passive cell balancer, but it takes a VERY LONG TIME to do it’s job. In this case, months. But after cycling this battery two dozen plus times, I’m now able to pull about 75% of the rated capacity and it’s still getting every-so-slightly better every time. (I’m tracking this.). I think the best I can hope for is about 85% when charging the Varg at full speed.
The upshot is: Don’t expect to pull 5KWh from a battery this cheap right out of the box. And the tech support is all chat-based and run through Google Translate. TLDR: Buyer beware.
The batteries are about 80lbs each and come with convenient handles. The inverter is about 45lb and is a bit awkward to move about.
URLs for the bits needed. I make ZERO claims for any of these products or sellers, other than they all worked for me. The battery took 3-4 months to arrive from China.
48V Battery and Inverter
https://www.aliexpress.com/item/1005005738601747.html
https://www.aliexpress.com/item/1005006042570368.html
48V Charger
https://www.canbat.com/product/48v-15a-lithium-battery-charger-lifepo₄/
Pre-crimped cables:
https://www.amazon.ca/dp/B09GV5T4MT
https://www.amazon.ca/gp/product/B094MH318S
https://www.amazon.ca/gp/product/B08V1629L1
