240V Inverter in a Van or Truck

[rayivers]

What kind of flexibility do you have in mind?

Well... you could power a 48V inverter with four 12V 200aH batteries in series, which would give well over 4kW for 2 hours (more than enough for one 240V rapid charge). You'd still need to charge these batteries, but I'm sure there are a number of 48V chargers available (a lot of smaller EV's use 48V batteries / chargers / etc., which is another excellent reason to go 48V).

I really don't see any way to use an alternator at these power levels unless you go whole-hog and add a giant 240V alternator plus rpm servo-control on the engine, and even then I doubt you'd be able to provide 4kW continuously without overheating the alternator.

The Powerwall would've been such an elegant solution to all this. I wonder if they ever show up used, maybe after a house sale / demolition / whatever.

 

[bluefxstc]

If you are using lithium batteries you need a specialized charger. As rajivers stated you can't charge a lithium battery, at least not if you want the battery to last, with an alternator or a dumb charger. Lithium batteries require a somewhat specialized charge curve and then at a preset point you shut the charger off. My charger shuts off when the pack reaches 53 Vdc and the current decreases to about 3A. If you try and use a dumb lead acid charger you will eventually over charge the cells which will lead to premature failure.

The only reason I went with 48V, is because I already had a 48V lithium charger. To charge this pack I simply unplug it from the lawn mower pack and plug it into the pack for the Alta off grid charger. Using the existing charger saved me $500-600. If I was building an off grid setup without that consideration, I would go to a higher voltage. A higher voltage reduces the amount of current required for a given power output. Lower current reduces the wire size and also losses at all the connections, and there are lots of connections in these systems. The losses at each connection go up exponentially with increases in current so less current is good. There's a reason most EVs produced now are 350V+ and going to higher voltages. The Porsche Mission e reportedly has an 800Vdc high voltage pack. If you are building the system from scratch, use a voltage as high a voltage as you are comfortable with. If you try to make 2500W with 12Vdc you are looking at around 210A which is a lot of current. I would try and avoid that.

If you are shooting for max efficiency, you probably want have your pack voltage approximately equal to the peak voltage of your inverter output. This will minimize amount of voltage boosting that your system needs to do to get the desired output. To get the peak voltage of an AC waveform multiply the RMS voltage, 120 Vac in the US, by 1.414. In the US that will give you a value of about 170V and 340V for 120Vac and 240Vac respectively. I am not encouraging anyone to build a 340v off grid system, just saying it would be more efficient, but higher voltage within reason, are better. For an off grid system, 48V is adequate. Personalty, I would rather be at 120 if I had the choice. My car is at 155 Vdc/700A so I am more comfortable with higher voltages and currents than most.

 

[rayivers]

+1 ! It would be cool to have maybe a 380V? pack, so the inverter could be eliminated completely and the Alta charging circuit driven direct (don't know where you'd find a suitable 380V charger, though). Definitely not Electronics 101 projects.

 

[bluefxstc]

380V charger is relatively easy, like most things it just takes money , but not really that much ($665 plus shipping). The charger I have in my car will go to 417V and I think the charger from a Chevy Volt will will go to 420V with an appropriate CAN controller, but it is liquid cooled. Definitely beyond my ability to design, but I can make it work since for the most part you just plug it in. The Volt charger requires some programming, but the controller works pretty well so I am pretty sure it is just entering the values through a web interface.

Not sure if the charger will take a DC input instead of AC, but it is a possibility. Basically the first circuit in my car charger is a bridge rectifier so from there on it is just seeing DC anyway.

 

[rayivers]

Those sound like pretty nice chargers! I'm used to the weenie 116V Zero units.

Not sure if the charger will take a DC input instead of AC, but it is a possibility. Basically the first circuit in my car charger is a bridge rectifier so from there on it is just seeing DC anyway.

I was thinking about injecting the 380V after / instead of the rectifier, probably using an SPDT contactor or similar.

 

[Philip]

Well... I am not planning to install a second alternator in my van at this time, and my current stock alternator is only 12V.

The Battle Born battery company said I can use the stock alternator to charge their batteries if I install this LiFePO4 Battery Isolation Manager gadget:


I appreciate the efficiency and thin power cables, but I have a feeling I'd have to jump through hoops to convert my 12V van into 24V or 48V. And the expected gain is only 1-2%. Maybe more, if the 48-240V inverter is more efficient. Or maybe less, if the additional 12-48V step-up converter is not very efficient.

Not happy about having to run 1/2" thick 4|0 AWG wires to the batteries though.

DC Cable Sizing Tool - Wire Size Calculator - MM2 & AWG - solar-wind.co.uk

12VDC - 300A - 4|0 AWG - 1m cable - 1% loss
12VDC - 300A - 4|0 AWG - 2m cable - 2% loss

48VDC - 75A - 9 AWG - 1m cable - 1% loss
48VDC - 75A - 6 AWG - 2m cable - 1% loss

 

[rayivers]

I am not planning to install a second alternator in my van at this time... I'd have to jump through hoops to convert my 12V van into 24V or 48V

I absolutely agree with both of these - in fact, at this point I'd suggest not doing anything to your van's OEM electrical system at all, and just going with a standalone / charge-at-home 48V (or whatever) battery + 48V (or whatever) inverter setup, physically mounted in the van but 100% electrically separate from the van's electrical system, that will give you one complete fast charge at the track using battery+inverter power only.

 

[Philip]

you could power a 48V inverter with four 12V 200aH batteries in series, which would give well over 4kW for 2 hours

This 800 Ah of batteries will weigh 500 lbs in AGM, or will cost $7,500 in LiFePO4. This is too heavy and bulky, or a bit less bulky but costs way too much money.

The stock alternator is quite capable. It can run the van's engine and the Standard charger from 110VAC simultaneously, indefinitely. It can, in effect, provide about a half of the electrical power that I need to charge the bike from 240VAC. I would like to be able to use it, at those times when I have to. When I know I need a full second full charge from 240VAC, the alternator can help the batteries, or the batteries can help it. In most other cases though, I will be only using the batteries. I have not been able to drain my two bikes in one day, so I think I will be okay most of the time.

With a 48V system I would have to use either 4 or 8 batteries. With a 12V system I can start with just 3-4, and then add more, if needed. That is flexibility. Thick wires is the only inconvenience that I see.

 

[rayivers]

The stock alternator is quite capable. It can run the van's engine and the Standard charger from 110VAC simultaneously, indefinitely.

So you've actually done this? I thought everything was still in the planning stages at this point.

 

[Philip]

I've had a 3000W 12-110V modified sine wave inverter in my van for the last 3 years. Yes, it can charge the Redshift from 110V from zero to full. But only if it is 110V. It made very little difference at the track though because you normally need 5 hours to charge at that rate.

I even tried hooking up a 12-220V inverter, but it worked only for 30 seconds.

With my new setup I hope I would be able ride noticeably longer. Long enough to get me tired and wanting to go home before all the batteries run out.

 

[rayivers]

I'm pretty much running out of ideas. It seems the only options are big alternators or big bucks, with no guarantees either way.

I even tried hooking up a 12-220V inverter, but it worked only for 30 seconds.

Any thoughts about why this happened? Given your long-term success with the present inverter, it seems like analyzing & possibly fixing this problem would be worth pursuing.

 

[Philip]

I'm pretty much running out of ideas. It seems the only options are big alternators or big bucks, with no guarantees either way.

Yep. This pretty much sums it up. Compared to the existing off-the-shelf battery options the Tesla Powerwall and the Alta's spare battery pack look like screaming deals.

Any thoughts about why this happened? Given your long-term success with the present inverter, it seems like analyzing & possibly fixing this problem would be worth pursuing.

The stock alternator is rated at 180A. When I was asking for 110A from it, it worked fine. When I started asking for 220A, the stock battery tried to step in, but it couldn't provide enough voltage and current, so the inverter was turning itself off.

The fix to this problem is either a much bigger alternator or a much bigger battery.

I do not want to sink $2,500 into alternators and have to deal with a running van and its heat.

Batteries seem much more attractive in a van. You need some batteries in a camper van anyway.

 

[rayivers]

When I started asking for 220A

I think it's more like 300A. The Alta fast charger draws 16A at 240V, almost 3.9kW; this would require at least 270A at 14.4V alternator out, or 325A at 12V (before losses).

It's like there's this @ 1500W threshold: below it things are fairly easy to implement at a reasonable price, above it not so much.

 

[Philip]

I do not have my Rapid charger yet, so I was only able to experiment with the Standard charger. That one supposedly draw only 12A at 220V.

 

[rayivers]

I do not have my Rapid charger yet, so I was only able to experiment with the Standard charger. That one supposedly draw only 12A at 220V.

Oh, OK. Hey, have you looked into a custom 12V battery (taller w/same footprint as OEM)? I almost had one made by a local battery shop for my trailer generator, as the stock pan was pretty small. One rated for @ 1000 cold cranking amps should easily be able to provide the extra current needed to power your standard charger at 220V via the inverter; you'd still need the engine running, though. This would eliminate the charging and paralleling issues, big cables still required. The guys at the battery shop would probably be a wealth of info on what type of battery to have made, what to watch out for with this setup. etc.

 

[Philip]

This whole thread could be summarizes in a 3x3 decision matrix. The choices are:

Alternators:
A) Stock
B) Upgrade Stock, or add an independent Second
C) Upgrade Stock and add a Second in parallel

Batteries:
1) None
2) Just enough to help the alternator(s)
3) Enough to run independently of alternator(s)

The B2 combination is Recipe #1 (post #1).
The C1 combination is Recipe #2 (post #31).
The A3 combination is Recipe #3 (post #52).

I think the A2 combination might not quite cut it, if I eventually get and start using a Rapid charger.

If I have to upgrade the alternator, I would then have to run the van every time I need to charge the bike (combination B2). At this point I might just as well upgrade both alternators and not have any batteries (combination C1). I do not like these scenarios because standing near a hot running van on a sunny day can be quite exhausting. I might instead then just carry generators and have them running behind the van. It will be cooler and cheaper.

So my current plan is combination A2.5, upgradeable to A3.

 

[Philip]

Hey, have you looked into a custom 12V battery (taller w/same footprint as OEM)?

No, I didn't look into it. I think I would need at least 150-200 Amps more for this setup to work with a Rapid charger. The stock battery would have to triple in size. Which brings me to combination A2.5, which I am currently pursuing.

 

[snydes]

No, I didn't look into it. I think I would need at least 150-200 Amps more for this setup to work with a Rapid charger. The stock battery would have to triple in size. Which brings me to combination A2.5, which I am currently pursuing.

Would 8D sized lead acid batteries be of any use to your cause?

Shop Deka 12-Volt 1,005-AMP Farm Equipment Battery at Lowes.com

 

[Philip]

Would 8D sized lead acid batteries be of any use to your cause?

That is 1,005 cranking Amps. Most car batteries have about 900 cranking amps for 30 seconds. I need 200-400A continuously for at least an hour.

 

[bluefxstc]

Not sure what the rules are here on vendors, and I don’t want to break any rules. Really not looking to sell anything, but I also don’t want to see people pay more than they have too. I have seen some really high numbers floating around on what it will cost for an off grid charging setup. I have a small business doing EV conversions, so sell both CALB (batteries) and Elcon (chargers). If you want a lithium battery, off grid charging here is what it will cost:

Batteries: 17 CALB 100 AH cells $2380 ($140 EA) plus shipping. Shipping is via UPS ground. The weight of 17 cells is about 127 Lbs so it is not cheap, probably $100-300 in the continental US, but it will not change that much with additional cells. Additionally, you will need 16 battery straps per group of 17 cells at $2.00 each so $32 per set. 17 cells will give you 5.5Kw of power, so good for fast or slow charge, depending on the inverter you chose and charger you have. If you want to do more charges, just add another bank of 17 cells. Realistically you can get 5Kw out of a bank of 17 cells so a good solid charge, but not 100%.

Charger: An Elcon 1500W is $525 or $665 for a 2500W charger. A 2500W charger requires 240Vac so I would recommend a 1500. Get home from riding, plug it in and go to sleep. It will be charged in the morning. You could also probably power the 1500W charger from a vehicle inverter if you really wanted to, your choice, but I wouldn’t recommend it.

Inverter: My inverter which seems fine for charging at 120Vac was $266 off ebay. They have a 5000W version which will do 240Vac out so it should power an Alta fast charger, but no promises there since I haven’t tested it. The cost for the 5kw inverter is $590.

Misc Parts: You will need a fuse which is $10-50, some fairly large wire $50, Connectors $20 and an enclosure of your choice for less than $100.

Tools: Only basic hand tools. The only specialized tools you need is a good set of wire crimpers. 3.3kw at 48Vdc is almost 70A so you want to make sure you have good wire connections or you will build heat. In the price estimate I am assuming you have all the tools you need.

Rounding the numbers and adding in approximate shipping the total cost for a charge system is about:

Slow Charge / Fast charge

Batteries $2700 / Same
Charger $550 / Same
Inverter $270 / $590
Misc $300 / Same
Total $3820 / $4140

A 4kw generator is a cheaper option, but if you want off grid, lithium battery charging, this is what I can get it to you for. You can also adjust these numbers some. You can add more batteries for more power, but then you will need a different inverter unless you go to parallel strings of batteries. In my setup I have 15 cells in series but quoted 17 here for more power so there are options. Pretty sure different inverters are available, I have seen them all the way up to 120Vdc input, but I don’t have firm info on them.