LiIon solar charge controller with load output regulation?

[Joerg]

Folks,

Is there a solar charge controller that provides a hard and (somewhat)
regulated 12V-14V output and uses a LiIon battery? The standard ones are
like this and then the battery voltage fluctuates with the LiIon pack:

http://www.solarbruder.com/charge-controller/ephc-for-li-ion-battery-pack

Most are for 3-cell and then the low cut-off is around 8V. Way too low,
a lot of 12V gear conks out below 10V or so. If one would use a 4-cell
battery the problem is going to be the upper end, almost 17V ... phssss
.... *POP*

We'd need 12V/20A out, driving motors. Ripple can he quite horrid. Our
current charge control costs around $25 but I realize that's not quite
possible with regulated output. But has to be <$50.

 

[Joerg]

Why not a system designed for (and using) a 6-cell lead-acid? That'd put
you right in your 12-14V range.

That's what we have right now.

Those usually are not able to follow the precise charge regimen for
LiIon batteries. The end-of-charge voltage for LiIon must be accurately
regulated. It's only a small band between not reaching capacity and
*KABLAM*

Also, LiIon has a much wider voltage range over the useful discharge
range. 3-cell is too low in voltage at end-of-capacity, 4-cell is way
too high when full.

6-cell lead acid is what we have right now but the gripe is that it
makes the whole unit too heavy to carry.

 

[[email protected]]

That's what we have right now.

Those usually are not able to follow the precise charge regimen for
LiIon batteries. The end-of-charge voltage for LiIon must be accurately
regulated. It's only a small band between not reaching capacity and
*KABLAM*

It's not all that difficult, today.

Also, LiIon has a much wider voltage range over the useful discharge
range. 3-cell is too low in voltage at end-of-capacity, 4-cell is way
too high when full.

That's why they make buck/boost regulators. ;-)

6-cell lead acid is what we have right now but the gripe is that it
makes the whole unit too heavy to carry.

SLACs are nice but have a fairly low power density.

 

[Joerg]

I figured you were going to bring weight into the discussion.

Yes, if you want to use LiIon cells then your life gets more difficult.

Somewhere out there on the web is someone selling a LiIon battery that's
supposed to be a form-fit-function replacement for a 12V car battery.


I'm not sure how they're doing it (I suspect on-board electronics), but
if you're lugging more than one car battery now, and you can get the
capacity you need from one of these gizmos, then it may be your meal
ticket.

Particularly if they have a motorcycle version...

We'd need something between 25Ah and 30Ah, 12V. Unfortunately the power
hardware is picky regarding those 12V. Especially some of the motors
really lose steam when that drops to less than 11V. And a 3-cell LiIon
will, big time.

 

[Joerg]

It's not all that difficult, today.

I know, but we are looking for a fairly cheap off-the-shelf solution.
Figuring that we can't be the only one with such a wish. Although the
20A peak power requirement is unusual, outside the normal camping
utensil range.

That's why they make buck/boost regulators. ;-)

Sure, I could roll my own but the client would rather not want to do
that. Then you have to go through engineering phase, all new EMC, and
all that.

SLACs are nice but have a fairly low power density.

Wot's a SLAC? I guess you don't mean the National Accelerator Lab

 

[[email protected]]

Wot's a SLAC? I guess you don't mean the National Accelerator Lab

SLAC == Sealed Lead-Acid Cell

 

[Joerg]

SLAC == Sealed Lead-Acid Cell

Ah, thanks. But that's what we'd like to get rid of, on account of its
weight.

 

[Joerg]

Maybe you'll have to go with 4-cell and drop some volts on the load
side. Inefficient, sure, but it'll get around the voltage "mismatch".

That would be my choice, use a sync buck on the load side. But that part
of the product is done and they don't want to change it.

Also, all the controllers I found so far only supported 3-cell LiIon :-(

 

[Jamie]

We'd need something between 25Ah and 30Ah, 12V. Unfortunately the power
hardware is picky regarding those 12V. Especially some of the motors
really lose steam when that drops to less than 11V. And a 3-cell LiIon
will, big time.

Hi,

I found these ones, look pretty cool:

http://www.valence.com/sites/default/files/images/XP_Module_Datasheet__1.pdf


http://www.valence.com/sites/default/files/images/RT_Module_FR_Datasheet_.pdf

cheers,
Jamie

 

[Joerg]

Hi,

I found these ones, look pretty cool:

http://www.valence.com/sites/default/files/images/XP_Module_Datasheet__1.pdf



http://www.valence.com/sites/default/files/images/RT_Module_FR_Datasheet_.pdf

Thanks, Jamie! Those look promising, will inquire whetehr they are
reasonable in cost and can work with a solar panel.