[electromango]

I have a 300Ah ~13V battery in my campervan. In the winter, solar power is insufficient.

I would like to use public EV charge stations to charge my battery at 0.5C = 150A , ~2kW.

I could buy a gasoline generator, but I'd still need to convert 230VAC to 13.5V @ 2kW, and buy a generator, which is noisy, more expensive per kWh, and generally less attractive than quiet EV charging.

Are there any plug-and-play solutions that can communicate with the charge station, and possibly convert the voltage into low-voltage range, e.g. 48V (which I can then convert to ~13.5V).

I'm not sure what words to search for in the forum.

I welcome any ideas!

 

[john61ct]

First off, they are for EV use only, IOW it's stealing.

Second you can actually get in trouble.

Third, no there isn't simple gear for this, and you'd have to ask elsewhere for DIY help.

Note those high voltages can be deadly.

 

[electromango]

Hi John

Is it stealing if I am paying for the kWh that I am charging?

I just thought this was the right forum, because I assume that DIY builders also want to make their cars compatible with public EV charging stations, and given that batteries can have different voltages, it might be possible to buy a properly certified EV solution that could provide a low-voltage, for example for motorcycles which I presume have smaller batteries and there also lower voltages.

Thanks anyway

 

[brian_]

While I agree that "free" stations are intended for EVs so this would not be appropriate, I also agree that if you're paying it should be fine.

Past the ethics, I wonder about the economics: at some of these things the cost depends on time (not energy), so at a very low (by EV standards) charging rate it wouldn't be a great deal.

Technically, the charging station hardware is just a cable, connector, and elaborate switch to make sure that a charger is properly connected and can handle the power before the voltage is applied. That means that there's no need to use an actual EV on-board charger, just the components that tell the charging station that it's okay to turn on and how much current should be allowed. It would be excessively complex and inefficient to convert from the AC source to ~48 V DC, then convert again from ~48 V DC to the battery voltage.

The charger itself - the part that takes 120 V or 240 V AC and produces battery-voltage DC - could be whatever off-the-shelf automotive/RV charger that you want to use.

Personally, I would just look for ordinary 120 V 15 A plug-ins (or the local equivalent if you are not in North America, such as 16 A @ 240 V in some places), and wait longer for a charge. At 1.5 kW instead of 2 kW it wouldn't be much longer at all, and if you're in a 240 V service area you would likely have over 2 kW available). Unfortunately most automotive battery chargers run at nowhere near the desired rate, so the best readily option might be a large RV converter/charger; Xantrex chargers (for instance) only come up to 60 amps, but can be "stacked" (combined in parallel) and will work with anything from 90 V to 265 V AC input, and Progressive Dynamics offers a compact 80 amp unit (for North American AC voltage).

While the battery is about 13 volts (presumably lead-acid at nominally 12 V), the charging voltage would presumably be significantly higher. 150 amps multiplied by a realistic charging voltage will be more than 2 kW.

 

[MattsAwesomeStuff]

I would just use a normal 120v 15A plug. That's 1800 watts. Close enough.

You can build your own (well, 800-1000 watts anyway, otherwise would need 2) from an old microwave and about a $2 rectifier. It'd probably take an hour or two.

Can probably even re-use the cable and not have to buy wire if you want to spend some time on it.

I presume you're using lead-acid batteries, in which case, it's dead-simple. Feed it ~14-15v and it'll take care of the rest.

Alternatively, if you want something different and free built out of junk, get a 2hp electric motor and a car alterantor to two, mechanically strap the two together and the alternator should automatically become a charger. Ghetto as all hell, but, if you're stealing power, meh, you're already aboard that train.

 

[brian_]

I just thought this was the right forum, because I assume that DIY builders also want to make their cars compatible with public EV charging stations, and given that batteries can have different voltages, it might be possible to buy a properly certified EV solution that could provide a low-voltage, for example for motorcycles which I presume have smaller batteries and there also lower voltages.

All that makes sense to me.

DIY project compatibility with public EV charging stations isn't trivial, but from reading in this forum it appears that it has been done. I don't know if anyone has done it for a low-voltage pack; I don't even know if anyone has done DIY charging from a public charging station of any motorcycle.

 

[electromango]

I would just use a normal 120v 15A plug. That's 1800 watts. Close enough.

You can build your own (well, 800-1000 watts anyway, otherwise would need 2) from an old microwave and about a $2 rectifier. It'd probably take an hour or two.
...
Alternatively, if you want something different and free built out of junk, get a 2hp electric motor and a car alterantor to two, mechanically strap the two together and the alternator should automatically become a charger. Ghetto as all hell, but, if you're stealing power, meh, you're already aboard that train.

Matt, you're my spirit animal

And it's a great idea:
a) some car alternators can provide 150A, and can even be modified to provide desired voltage, e.g. controllable range of 13-14.4V

This is a much better alternative than generating 230V, then converting to 12V, then boosting to a controllable 13-14.4V.

b) the alternator could probably be modified with improved cooling to support continuous 150A load

That would give ~150A x 13.5V = ~ 2 kW

But it's a lot of hobby work, that doesn't easily translate into a mass market product


The microwave idea is also interesting. I didn't know that they have such transformers.
My idea was to convert 230V to 12V using server PSUs. That's about $50 per 1200w PSU. And then convert 12V to 13-14.4V range.

But I think they're both quite noisy :/

 

[electromango]

I'm using LiFePO4 cells, where the discharge voltage is typically ~13.0V, and charge voltage is typically 13.5V, although ~12.5 in the first 5% SoC and 13.8-14.4V at last 5%.
Typically I stop charging at 14.0V to avoid full SoC for longevity. (homemade charger using Arduino and a relay turning off the charger).

I'm located in Malmo, Sweden. In Europe, the Type 2 socket is most common.
The price is about 0.28 USD per kWh, with free parking during charging.

I've looked into it, and it seems that the Type 2 socket provides 3x230VAC.

And it seems one guy succeeded at making a simple socket conversion:
https://www.instructables.com/id/Type2-Mennekes-to-3-230V-Sockets-under-Constructio/

Each 230VAC is supposedly limited to 16A, which is ~3.7kW, which is perfect.

And apparently the communication protocol is also ridiculously simple: just a resistor.
I thought it was something more complicated, i.e. CAN bus with actual data being transmitted.

http://evblog.wanjon.nl/?p=18


Now the main problem is how to cheaply getting 13-14.4V charging at 2-3kW.
Most of the chargers are expensive (e.g. 500-1000 USD) and only at 100A, when I would prefer 200A.
I'll either go the server PSU or microwave transformer route, I think.

 

[baxy]

The product at the end of Damien's video here my be of interest to you for powering off type 2 chargers
https://youtu.be/A197yWQKaLs

 

[MattsAwesomeStuff]

But it's a lot of hobby work, that doesn't easily translate into a mass market product

Good Christ do not sell or even give away a home-made fire hazard made from a rewound microwave oven transformer. When you build something you generally understand it and the risks and can stay on top of it.

The microwave idea is also interesting. I didn't know that they have such transformers. But I think they're both quite noisy :/

https://www.youtube.com/playlist?list=PL2FD9A01DD3B7A5D7

And, if you build it right it should be just about silent, aside from the fan. No getting away from the fan, MOTs are built to cut every corner, they run hot.

 

[electro wrks]

Alternatively, if you want something different and free built out of junk, get a 2hp electric motor and a car alterantor to two, mechanically strap the two together and the alternator should automatically become a charger. Ghetto as all hell, but, if you're stealing power, meh, you're already aboard that train.

This is a variation of what are called rotary converters:https://en.wikipedia.org/wiki/Rotary_converter. It would be kind-of heavy and not very efficient. You could incorporate it on the same frame unit with a belt drive gas engine. Just switch the belts that drive the alternator(s) from the gas engine to the electric motor depending on how you wanted to charge your batteries. Again-heavy, noisy, inefficient.

Like it says in the Wikipedia article, rotary converters have been mostly replaced by solid state electronics. In your case, this would be an electronic battery charger. You should shop around for these. Some of the chargers can be paralleled. If this could be safely done(check with the supplier), you could stack them up to get your desired charge rate and time. Don't forget to check or have a GOOD BMS to check the voltage balance of the cells in your battery bank.

 

[brian_]

I guess that's two votes for off-the-shelf chargers, stacked (paralleled) if required.

I'm using LiFePO4 cells, where the discharge voltage is typically ~13.0V, and charge voltage is typically 13.5V, although ~12.5 in the first 5% SoC and 13.8-14.4V at last 5%.
Typically I stop charging at 14.0V to avoid full SoC for longevity. (homemade charger using Arduino and a relay turning off the charger).

Although the battery is LiFePO4, the charger doesn't need to be specifically for this application - it just needs an adjustable output.

The price is about 0.28 USD per kWh, with free parking during charging.

You're lucky that although the cost per unit energy is excessive, there is no time factor. Draw power at a low enough level, and that's cheap parking even if you don't need the energy.

 

[ga2500ev2017]

The most important item you need is an charger for the battery. Understand that a L2 charging station is little more than a "smart" 240V extension cord which is designed to have a dead wire until the EV is actually plugged in.

So go ahead and design your charging system to take power from the wall and get it working to your liking. Once you're finished with that, then take a look for an item known as an EV simulator. It's a simple device consisting of a few resistors, a diode, and some switches. You can find an example of one here: http://analogevse.xyz/AnalogEVSE-en.html#Testing. Note that you really only need the 2.7K and 1.3K resistors, SW2, and the diode. SW1, SW3, and SW4 are there to test connections and errors.

In the end the most costly part of the project is the actual J1772 connector. You may be able to get a cable cheap at a U-pull-it type yard if you can find a plugin vehicle on the site.

Hope this helps. While there may be a bit of a gray area in terms of using an EVSE to charge a non traction battery, I'd suggest that etiquette is probably more important. Specifically if an EV comes along and needs to charge while you are charging, please cede the cable to them and either wait, or move on. An EV needing a charge really cannot move without recharging. It's unlikely that your sitation matches that.

ga2500ev

 

[john61ct]

Fully agree as to etiquette, but also be wary of legality with free stations, those funded by tax dollars as well as those on private property.

So technically, a "worldwide universal" charger, like Sterlings and Promariner for 12/24V House banks, could be used off the 240V provided by the EV station as well as USA 120V?

A female mains plug inside the vehicle, then the EV simulator, then a box outside with your J1772 extension cable.

IOW does that EV 240V have the same characteristics as Euro home / mains current, or the 240V you find at RV campgrounds and marina power poles?

Or is further splitting / conversion required between those?

 

[brian_]

IOW does that EV 240V have the same characteristics as Euro home / mains current, or the 240V you find at RV campgrounds and marina power poles?

Euro 240V can be single-phase or three phase. North American 240V domestic service is split-phase, meaning that it is 240 V between the two lines, with a neutral so you can have two out-of-phase 120 V supplies from the same source; home don't get any 3-phase power here. North American RV "50 amp" service is the same 240 V split-phase; the receptacle used is even the same NEMA 14-50 as used for a typical residential kitchen range.

 

[edanto]

The product at the end of Damien's video here my be of interest to you for powering off type 2 chargers

This is amazing! Has anyone managed to find a commercial supplier for this type of device, please? I've reached out to Damien and asked if he could put me in touch with the person (Matija) who supplied it.

Perhaps someone on this thread might know where to get one?