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[BSDThw]

DC/DC Converter mean you change your voltage it would be possible to make 12VDC to 74VDC but as closer both voltages are the better the efficiency (if using the right technology).

You don't need to bypass the charger. You have the connector at the right of your battery pack for the additional charger.

As much as I know you can feed it from 0-24A (2* DeltaQ => 2*12A) DC.

The Delta will work current delimited till you reach the top voltage than it will reduce current to stop over-voltage.

A correct adjusted DC/DC Converter could feed the battery with the maximum your Solar module is able to deliver(e.q 3ADC and 50-74,7VDC).

By the way a "modified sine wave" is a square like Lipo423 painted but between the negative and the positive square there is a time when the voltage remains zero. So the the peak voltage is 325V/ 155V
and the RMS area of the power is the same as for a sinusoidal.
 

 

[ed5000]

I have a 12 VDC system at home with a 300 watt pure sign wave inverter that I use to charge my electric bicycle.  For the bicycle I have a 300 watt charger that changes 120 VAC to 60 VDC so it's not very efficient but, interestingly the bike charges faster on the inverter than my standard wall outlet.  The bike charges in 3/4 of the time on the inverter over the wall outlet.  I'm not sure what's going on except it must be a power factor issue.

I've been very tempted to buy a Samlex 1500W pure sign wave inverter to charge my 2010 DS.  It would only cost about $500 and I already have everything else but, I would really rather go with a dc to dc converter.  I would need one that converts 12vdc to 60vdc for a '10 DS.  Anyone know a good one? 

[kcoplan]

BSDthw -- Thanks for the advice, but I am not sure a "DC-DC" converter ends up being that much more efficient.  As far as I know, the only way to step up DC voltages (what a DC-DC converter would have to do) is to convert the DC to AC and run it through a transformer, then rectify it back to DC.  That is, essentially what an inverter combined with a charger will do, with one additional (and not strictly necessary) voltage step down involved.

Inverter plus charger:

12v DC converted to 12v AC stepped up through transformer to 120VAC --> charger steps 120VAC down with transformer and rectifies to a voltage and current regulated 72VDC ()

DC-DC Converter:

12v DC converted to 12v AC stepped up through transformer to 72VAC then rectified and voltage controlled to 72v DC

So a DC-DC converter will probably be more efficient than a DC-AC inverter connected to a charger (AC-DC), but not dramatically more efficient.

But my knowledge on this subject is somewhat dated.  If there is a DC-DC converter that works without making AC as an intermediate step, I suppose it could be much more efficient  . . .

[ColoPaul]

As far as I know, the only way to step up DC voltages (what a DC-DC converter would have to do) is to convert the DC to AC and run it through a transformer, then rectify it back to DC.

Charge pumps can work to 90+% efficiency, but I've only seen low power implementations.
http://en.wikipedia.org/wiki/Charge_pump

A type of switching supply called a "boost" also works without a transformer:
http://en.wikipedia.org/wiki/Boost_converter
They are used in high power situations, and can be very efficient if they don't have to be built to tolerate wide voltage/current ranges.

[RickSteeb]

"Got a very prompt and helpful response from DeltaQ as follows:

Thank you for your email.  A modified sine wave produced by the inverter should not be a problem for powering the QuiQ.  However, generators with active voltage regulation circuitry may interfere with the power factor correction (PFC) stage of the charger. ..."

Power factor correction would seem likely to have serious issues with the "modified sine wave", as keeping current "in phase" with near instantaneous voltage swings is not possible.  Just sayin'...

[trikester]

From a career of designing switchmode power supplies (AC - DC & DC-DC & a few modified sine inverters) plus power factor correctors (I have a patent for one of those), I agree with RickSteeb. The power factor correction built into the front end of the battery chargers could (most likely would) have a problem with the modified sine wave source. However, it may still work but put an unusual load waveform (possibly stressful) on the power supply. I never looked at that combination. 

Trikester

[kcoplan]

Trimester, when you say "unusual load waveform on the power supply" do you mean the inverter in the power hub, or the "power supply" in the QinQ charger?  Do I risk frying the charger?

[trikester]

I was referring to the modified sine inverter supplying the charger input. The power factor corrector in the front end of the charger could create high current spikes in the source as it tries to do its normally sine wave job. However, without knowing the design, I'm just guessing about its behavior. It would be a good thing if someone on this forum had that combination and could monitor the output current, and voltage, waveform of the inverter with a scope, while it was powering the charger, and post the waveform. 

Trikester

[kcoplan]

That's good, Trikester.  If I have to choose between frying my 12k bike and my $800 inverter . . . I choose the inverter.

- Karl

[kcoplan]

Success!  After receiving further assurances from the DeltaQ techie, I used the Xantrex inverter and the battery bank to recharge my Zero S ZF6 this evening without any problems.

Today was the first day I rode the Zero to work and it was also the first day with the solar panels connected.

The 15 mile trip to work was a typical commuting day  -  probably averaged 35 mph, with a couple of 65 mph stretches.  Only used 3 of 12 "bars" to get in, and I plugged the bike in all day at my office.

The trip home was a little faster. - probably averaged 55 mph.  Used 4 bars.

So with the ZF6 about 30% discharged, and with the solar battery bank showing 13.1v (probably about 90% charged) I plugged the Zero in and watched for fireworkks.  The charger worked normally, and the Powerhub showed 960 watts coming out of the batteries and 880 watts going into the Zero.  After two hours, the Zero indicated a full charge (about the right amount of time for a 30% recharge) and the PowerHub draw dropped to 10 watts, with 0 watts going out to the Zero.  My solar battery bank is at 12.2v, which should be about halfway discharged, which is just about as much as I want to discharge it.

It's a 440 amp hour battery bank, so 2 kwh at 12v should work out to 160 amp hours, well under 50% of the battery bank capacity, the sweet spot for maintaining the longevity of the solar battery bank.

So -  tomorrow, we'll see how fast the solar panels recharge tha battery bank, but at least as far as the battery bank and the inverter goes, looks like I have a fairly sustainable solar powered commute (my office just installed a solar array on the entire roof )

Thanks again for all your advice!

[manlytom]

Lucky u can charge at work. Only way 4 me is to wheel into the lift and navigate it into my office.

So u charge it carbon neutral at home - what about the power at work?

[kcoplan]

Lucky u can charge at work. Only way 4 me is to wheel into the lift and navigate it into my office.

So u charge it carbon neutral at home - what about the power at work?

I teach environmental law at Pace Law School in White Plains, NY.  My building is very green -- it houses our Energy Project -- and we just covered the entire south facing roof with solar panels this year in a grid-tied system.  I think I can take credit for solar power when I charge my bike at work!  (I am running a cord out the window of my first-floor office).

Also, I pay a couple of cents extra at home for what Con Ed claims is 100% wind power, so even without the solar panels at home, I have some claim to being zero carbon (though electrons are very fungible, of course).

There's something really cool about having a second way to get to work now that is completely independent of oil companies and only partly dependent on electric utilities!  (My other carbon free way of getting to work involves two bicycles and a kayak, but that is a longer story).

[protomech]

Also, I pay a couple of cents extra at home for what Con Ed claims is 100% wind power, so even without the solar panels at home, I have some claim to being zero carbon (though electrons are very fungible, of course).

The utility that servers northern Alabama, TVA, has a renewable energy program which I subscribe to. It's almost entirely landfill methane, though they're adding more wind recently.

Anyhow, the fungible electrons bit really bugs me.