Portable Battery Generator for KTM Freeride EX-C Dirt Bike

[mjfav]

Hello everyone!

Total noob here looking for some guidance. Here’s my shot at brevity with specs, context, and use cases.

Use Case: Charge my electric dirtbike on multi-day trips…as well as my drone batteries.

I can buy 2 Ecoflow Delta Pros ($7500) and daisy chain them together with their 240 adapter and accomplish what I’m after (I think) but I am interested in a cheaper DIY option.

Bike Battery Specs:
Rated voltage: 259.2 V
Rated energy: 3.888 kWh
Rated capacity: 15 Ah
Max. charging current: 10A

Bike Battery Charger Specs:
AC INPUT: 220-240V ~, 50/60Hz, 13A Max.
DC HV OUTPUT: 180 - 302.4V ==-, 10.0A Max.
DC LV OUTPUT: 14.5V ==-, 4.0A Max.

Charger plug: it came with a male L6-20. I purchased a NEMA 14-30P Male to L6-20R Female, 20A, 250V adapter so I could plug it into my dryer outlet to charge my bike at home. Thanks to these guys here! chargethebike.com

Potential set up…

Solar Inverter: EG4 6000EX-48HV 6000W Output 7500W PV Input Split 500V VOC Input Split Phase 120/240VAC
Battery: EG4 LifePower4 Lithium Battery 48v 100AH Server Rack Battery 5.12kWh
Portable Solar Panels: Could use help here
Cables: Also some help here
Outlets: (I’m not looking to use 120 and 240 at the same time)
1 to charge bike
2 regular 3 prong wall outlet (1 for drone, 1 for misc)
2 usb-c for general glamping

Maybe there is something else I need?

My thinking is after I recharge my bike once, that will leave me with 1.24kWh hours in the EG4 Battery. Then I will solar charge on day 2 back up to at least 3.9kWh so that I can recharge my bike again in order to get 2 full recharges on 3 day trips. (Rinse and repeat for longer trips).

Although the bike is 100% the priority, I figured if I’m building this I might as well aim for something multipurpose to charge my drone and other misc items.

Last but not least, it looks like mounting this to a hand truck like this is the way to go. Although I don’t know if it’s possible to make it a little more weatherproof since the inverters I believe are supposed to be used indoors only.

Any insights is much appreciated!

 

[50ShadesOfDirt]

This is a learning curve for me ... electric dirt bike batteries; specifically, the EU model you seem to have and its constraints in the US.

Don't know what other constraints you are facing (glamping, noise, etc.), but it seems theoretically inefficient to use batteries to recharge batteries.

Have you considered (small, quiet, parallel) fuel generators and such? As in two inverter-gens paralleled to get 240v?

Don't know what vehicle you drive, but a (possibly massive) solar generator for 240v diy solar gen on hand truck would be interesting. Perhaps other formats (permanent mounting in truck bed, trailer mounting, etc.) might be an option?

 

[mjfav]

This is a learning curve for me ... electric dirt bike batteries; specifically, the EU model you seem to have and its constraints in the US.

Don't know what other constraints you are facing (glamping, noise, etc.), but it seems theoretically inefficient to use batteries to recharge batteries.

Have you considered (small, quiet, parallel) fuel generators and such? As in two inverter-gens paralleled to get 240v?

Don't know what vehicle you drive, but a (possibly massive) solar generator for 240v diy solar gen on hand truck would be interesting. Perhaps other formats (permanent mounting in truck bed, trailer mounting, etc.) might be an option?

Thanks for the reply!
Can you expand on “theoretically inefficient to use batteries to recharge batteries”?

I have considered a generator (reference), specifically the Genmax GM5500i or Harbor Freight 6500, although a big reason I went electric is to not deal with a gas motor. The noise also being a big factor when enjoying downtime in nature.

Permanent mounting could be an option.

 

[HRTKD]

If you're using an enclosed utility trailer or an RV toy hauler, you can certainly put solar on the roof and everything else inside and do your charging. I have enough in my RV toy hauler to charge my EV for ~3 hours. That isn't much charge for my EV (I got maybe 30 miles added to it), but for a bike I bet it's plenty.

 

[Hedges]

Dollars is the greatest inefficiency of battery to recharge battery.
Consider the number of discharge cycles you anticipate, and cost per cycle. Lead-acid tends to be 50 to 500 cycles, lithium 500 to 5000. You can calculate costs; I come up with $0.05 to $0.50/kWh if you use all the cycles. Much higher if battery dies due to shelf life rather than cycle life.

There are some quiet portable generators, which would be a good choice for some usage scenarios.

What is Wh rating of dirt bike battery, and how many cycles per day?
I would consider PV panel to recharge car/truck starting battery, and use that battery to recharge bike. If capacity and charge rate makes sense, could be a good option. Sizing PV array according to charge rate could extend this to higher current.
A different battery as you're thinking may also make sense, have to calculate the numbers.

 

[mjfav]

Ah yes, the almighty dollars. Generator let’s say $1000, this solar battery option around $3500. So I definitely agree it’s not cost effective. But let’s assume the noise and no gas motors is worth the extra cost to me.

What is Wh rating of dirt bike battery, and how many cycles per day? I would only cycle the bike battery once per day. As far as Wh, the only specs I have are in my first post.

 

[Doggydogworld]

How many days a year of usage do you expect? For something like 10-15 days I'd go with a small, quiet generator. Should charge your bike in a couple hours, maybe while getting dinner ready so the noise isn't as noticeable. Charge a small portable battery in parallel for glamping in silence the rest of the night.

Or maybe consider an EV with bidirectional charging? Obviously a major purchase, but you need a vehicle anyway so it might make sense. F-150 Lightning and most Hyundai/Kia EVs offer it. I've read the Mitsubishi Outlander PHEV has it, but don't know details. Some Toyota RAV4 Primes have a 120V outlet rated for 1500W, but you'd need to add a transformer or 120V charger for your bike. You can also attach an inverter to the 12V battery in just about any EV.

Is your dirt bike battery removable? If so buy a spare and charge one from solar while riding with the other. A spare can come in handy other ways, too.

If you're camping in a trailer or RV I'd lean toward adding solar+LiFePO4 to it, then charge the dirt bike from that system.

If you build a portable system like the one in the video, would you also use it and the solar panels at home? That can change the economics and justify a bit of extra upfront cost.

 

[Hedges]

Ah yes, the almighty dollars. Generator let’s say $1000, this solar battery option around $3500. So I definitely agree it’s not cost effective. But let’s assume the noise and no gas motors is worth the extra cost to me.

5kWh 48V LiFePO4 server rack battery ~$1500. "Drop-in" 12V assemblies various capacity and price.

What is Wh rating of dirt bike battery, and how many cycles per day? I would only cycle the bike battery once per day. As far as Wh, the only specs I have are in my first post.

Sorry, I should have read the details you provided:

"Rated energy: 3.888 kWh" - good fit for server rack battery

"AC INPUT: 220-240V ~, 50/60Hz, 13A Max." 230V x 13A = 3kW

"DC HV OUTPUT: 180 - 302.4V ==-, 10.0A Max." 300V x 10A = 3kW

Can't use automotive starting battery, would be 250A for one hour at 12V.

This would be 0.6C load on server rack. Would prefer slower charge, but you might find a suitable inverter for this 3kW load. Should be larger than 3kW, because it may have a nasty waveform and poor "power factor". Not sure, but I'm guessing another $1500 +/-, although maybe a cheapie ~$300 will work.
If you get a decent 48V sine-wave inverter (or if you select a different battery, like 24V, and matching inverter), you can run many things with it.
You'll also want a solar charge controller. Look into an AIO, e.g. the rebranded "DIY" line from Midnight, or other brands.

MidNite Solar's

MidNite Solar manufactures E-Panels, combiners, charge controllers, pre-wired renewable energy systems, surge protection devices and other quality Renewable Energy System electrical components.

midnitesolar.com

I suspect the 24V 3kW model isn't enough for your 3kVA load. The 48V 5kW model may be.

"male L6-20"

That's AC connection. How many pins connect DC charger to e-Bike? If only 2 or 3 (I doubt charger sees that many individual cells!) you might get away with a 300W charger that could run all night. But if there is communication, you would have to buy one meant for the bike. See what is available.

 

[mjfav]

Is your dirt bike battery removable? If so buy a spare and charge one from solar while riding with the other. A spare can come in handy other ways, too.

It is. I’ve read spares costs around the same as the setup I proposed. Can you explain the upside and how your suggestion differs exactly? If I’m charging from solar, isn’t that what I’m doing with my setup?

The 48V 5kW model may be.

Are you saying this is better than the EG4 6000ex? It is $50 cheaper but I think you get an extended warranty from eg4 if you buy an inverter and their batteries.

If you build a portable system like the one in the video, would you also use it and the solar panels at home?

Yes, if there is a way to hook it up to the house and for it to still be portable when I go on my trips.

 

[Hedges]

Are you saying this is better than the EG4 6000ex? It is $50 cheaper but I think you get an extended warranty from eg4 if you buy an inverter and their batteries.

I don't have experience with either. You might be able to read what others say.

Midnight is very highly regarded and the products they build are quality. The rebrand some quality items like breakers. DIY line inverters are rebranded Chinese clones; forum members were taken aback by that, but Midnight says they studied these and are confident in them. Might get custom software and upgraded parts or design in the future, but not yet. You do get their support and warranty.

What you're planning adds up to quite a few bucks, I think $3000+ with inverter and battery. Would make sense to have something that serves as backup for home use, an inverter/charger with AC input so it can be a UPS with PV. For a larger system I'd want the PV to blend with grid and supplement it, but not practical for your smaller PV array.

 

[Doggydogworld]

Can you explain the upside and how your suggestion differs exactly? If I’m charging from solar, isn’t that what I’m doing with my setup?

Spare battery advantages:
1. If one battery fails you can still ride
2. You can ride one to empty, return and swap in a few minutes, and go ride more (vs. wait a couple hours to recharge)
3. If you ever need to travel long distance, you can carry the spare and swap midway
4. If you ride a lot you'll eventually need a replacement battery anyway, so it's "free" to pre-buy it now
5. It's more efficient to charge a spare directly than to charge an EG4 then use it to charge your bike

EG4 advantages:
1. It can power other stuff (in theory a spare bike battery could, too, but that's a whole other can of worms)
2. You can possibly use it at home during blackouts or maybe to save on your electric bill

 

[50ShadesOfDirt]

You have a pretty good start to gathering requirements (power audit), so a design step is needed:

1. Go here, and enter in each appliance's (bike battery, other things you care about) values (watts, hours/day you want to run it, etc.):
https://unboundsolar.com/solar-information/offgrid-calculator
- in your case, the bike battery takes X hours to charge w/ your existing charger

2. Go here, using numbers from above, and fiddle with various entries/components, and you'll see in real-time what your system component (inverter, mppt, panel) sizing is:
https://www.altestore.com/store/calculators/off_grid_calculator/
- There are many similar website pages/calculators, but these two pages should help you get through most of the necessary calculations. This helps you quickly decide if you can do what you want to do, and you can vary component choices for what-if scenarios.

3. you'll probably need a 24v or 48v system voltage reference, just to get 240v output (bike battery constraint), and the 48v rack battery you desire also pushed you to 48v, but again, the above pages let you do some what-ifs

With the above, you've got a 24v or 48v AIO inverter, batteries, and panels somewhat sorted.

Sounds like a fuel generator isn't desired because of noise/nature constraints, but keep in mind weather/clouds/solar can be fickle, and leave you stranded, so if you can size components right for a honda 2200, these are extremely small and quiet, and a cover can be made/integrated to get noise to almost zero. Plus, if weather isn't cooperating, then gen is available, so it's a good part of the backup strategy what-ifs.

You could consider a small (harbor-freight 4'x4' or 4'x8') trailer, build a platform/enclosure to house everything, and then you've got solar gear under cover, solar panels on top, possible room for other gear, and, when done camping, trailer might be close enough to residence to provide backup solar to home (separate system, so no mess with tying in to home wiring). Or as suggested earlier, a "toy hauler" kind of trailer (sized for your needs) keeps you from DIY'ing the trailer.

Hope this helps ...

 

[Hedges]

Considering weight and bulk, you might want Anderson or similar connector for battery, and package the system as two modules you can easily manhandle or dolly around. Might use at home sometimes, or want space/weight of vehicle for other purposes.

PV panels you might want on a cart you can roll out and unfold to deploy in the sun, with vehicle parked in shade. Have a way to secure against blowing over and against growing legs. An extension cord with different plugs could be connected while discouraging the feeding of PV DC into anything that wouldn't like it.

 

[mjfav]

5. It's more efficient to charge a spare directly than to charge an EG4 then use it to charge your bike

Ah, I never thought I would have enough power to go straight from solar to the bike charger/battery. What would this setup look like and how long would it take to charge the 3.88kWh battery?

For comparison, plugging into my home dryer outlet will charge the batter in a little over an hour. I assume with the setup I proposed, time to charge would be similar.

 

[mjfav]

You have a pretty good start to gathering requirements (power audit), so a design step is needed:

1. 240V x 13A (Bike Charger Specs, not the battery)


2.


If my numbers are correct, I'll need 4, 400w Portable Solar Panels to add 4056w back to the battery - timing around 4.46 hours (full sun).
Haven't looked for comps yet but quick search found these for $579 each: ALLPOWERS SP037 400W Portable Solar Panel Waterproof IP67 Foldable Solar Panel Kit with 37.5V MC-4 | Good review here:

Based on my previous calculations, I'll need 2640w in order to charge my bike battery again. So perhaps that drops timing down to 2.9 hours (full sun).

If I only get 2, 400w solar panels, does that just increase the time to charge x2 or is the math not as simple?

 

[Supervstech]

Make sure you factor in efficiency losses...
The inverter is going to eat some of that 5120, as is your power supply to the bike...
I doubt ANY Wh will be left from the 5120Wh after charging the bike from zero.
Now, if you have 1200W of solar on top feeding while you discharge, it should have a bit left over after the charge.

 

[Doggydogworld]

Ah, I never thought I would have enough power to go straight from solar to the bike charger/battery. What would this setup look like and how long would it take to charge the 3.88kWh battery?

Ideally you'd use a MPPT solar charge controller that works directly with your spare battery. That would eliminate the losses due to the EG4 battery and inverter. It would only charge as fast as your panels generated power, not the full 10A of your current charger. Unfortunately I don't know of any SCC that can charge a 259.2V battery. DIYers like this guy have built devices that directly charge EV batteries from panels. A lot of their work involves tricking the car's systems so they can access the high voltage battery. Your task is simpler, but I still don't know an off-the-shelf SCC that would work.

For comparison, plugging into my home dryer outlet will charge the batter in a little over an hour. I assume with the setup I proposed, time to charge would be similar.

That's not bad. I figured it'd charge full speed for an hour or so then taper way down and take another couple hours to fully charge. You're right -- EG4 is rated for ~5 kW discharge so even with inverter losses it should be able to fully power your charger.

 

[mjfav]

Make sure you factor in efficiency losses...
The inverter is going to eat some of that 5120, as is your power supply to the bike...
I doubt ANY Wh will be left from the 5120Wh after charging the bike from zero.
Now, if you have 1200W of solar on top feeding while you discharge, it should have a bit left over after the charge.

Interesting, you think the inverter is really going to eat 1240w in a little over an hour of operation? I do like to overestimate for wiggle room. For instance, I rarely drain my bike battery down to zero but running the numbers as if I do.

 

[Doggydogworld]

Interesting, you think the inverter is really going to eat 1240w in a little over an hour of operation? I do like to overestimate for wiggle room. For instance, I rarely drain my bike battery down to zero but running the numbers as if I do.

I can see 20% loss in the inverter and bike charger. Plus you probably don't want to drain the EG4 all the way to 0%, especially not at ~80A.