I shoud not have to do this.

[JedidiahStolzfus]

This is how I charge my battery after riding to work.  I should not have to go through an inverter, there should be a device, that's "certified" by RadPower and other Ebike manufacturers that can charge from a DC source, such as a vehicle, or solar.

To have to go through and inverter is a terrible waste of efficiency.  Every time you convert DC to aC there's a loss in power.  In the case of the setup pictures, I'm going from 12VDC to 110VAC back to 52VDC. 

I looked for a while, and I cannot find any clean and guaranteed device that will go from 12VDC to 52V with the correct charging profile for these batteries.  Yes, I'm aware there are devices that claim to do it, but they all come from China and there's no guarantee that they are, what they say they are.  The consequences of plugging in an unknown device could be dire.  From destroying the battery to burning your house down. 

There's also a certain level of irony of Ebike manufacturers requiring the usage power plants to charge the bikes and not making it so that the end users can use solar in a safe and efficient way.  We shouldn't have to cobble something together, hope it works and doesn't burn up.

[Altema]

What you need is a direct 12 volt to 54.6 volt charger, and I don't know of any e-bike company that offers that, but it would be nice.
I could not find the complete specifications on your particular unit, but many inverters have an efficiency rating of better than 90%. I have a pure sine wave inverter in my car I use for charging e-bike batteries on trips, and if I recall correctly the efficiency is around 96%. Conversion from 12 volts to 54.6 volts is not not going to be 100% efficient either though, so I'm not sure how much better it would be, aside from being less cumbersome.

Is your inverted causing any specific problems, like draining your battery? And is there a specific reason you can't take the battery inside to charge? Just trying to wrap my head around the situation to see if I can help 

[JedidiahStolzfus]

The point is:
1. It's just one more thing that I need to carry.2. It's another point of possible failure.3. Going from DC to AC to DC is terribly inefficient.4.  There should be a direct DC charging solution available.  While there are some out there that claim to be the right thing, I don't believe they can be trusted until the bike manufacturers come out and say they've tested them and they're good to go.
I've seen the various youtube videos of people claiming that they have a working solution.  Then when you start digging into the products they've used you find out that they're not what they claim to be.  As in, they're not true MPPT devices.
Between the price of the batteries and the potential for fire for doing it wrong, I'd rather have the company say this is the correct device, instead of cobbling something together.  Trust me, I'm not against cobbling something together, I regularly design and build my own IOT devices, but making something like this is beyond my abilities.  Nor do I want to take on the liability if I screw something up. 

[JedidiahStolzfus]

My mobile charging solution, since there isn't a direct DC charger that can be considered safe to use.

Nice case from Harbor Freight, it's a Pelican knockoff.  Seems to be fairly heavy ABS.


The inverter is bolted in place, the charger is held in with velcro straps and a couple of 3D printed pieces.



One of the vans only has one functional 12v port, so I added one into this so I can plug in the GPS, cellphone holder and dashcam.



Cooling down the battery so I can charge it.



When I'm charging in the van, I put the box, with the lid propped open on the floor, and the battery on the floor in front of my seat and then set the AC to the floor to keep the charger and the inverter cool.

I did blow the fuse in the 12v plug this morning because I didn't check it lastnight when I finished wiring up.  It was only a 1.5A fuse, and the entire setup draws more than 3A.