which charge controllers are isolated?

[cardamon]

Does anyone know which ones - if any- are isolated between DC source and DC output?   Manufacturers never seem to say which is strange because that is important to know if you are doing any sort of system grounding.  I know that the schneider high voltage CC (MPPT 600-80 i think its called) is isolated but I cant get info on any others.  What about the classic?

[dnix71]

http://store.nextekpower.com/secondary/mppt-and-dcdc.html this brand advertises dc-dc isolation. So does this Texas Instruments kit http://www.ti.com/tool/tmdshvmpptkit

Why do you need isolation? Normally the frames of the panels are grounded to frames and those frames to earth for lightning protection.

[cardamon]

I dont need isolation, its just a curiosity and is required information if one wants to system ground properly.  Consider a typical off grid system that has a PV array, a charge controller feeding a battery, and an inverter.  That is potentially three different electrical systems that one may want or be required to ground. 

[Mary B]

National Electrical Code will specify all three be tied to a single point ground or you can end up with voltage differentials that can hurt or kill someone

[cardamon]

I agree.  The problem is its often difficult to figure out if/when these are indeed three separately derived systems.  Grounding two systems that arent in fact  isolated would result in a parallel path for current over non normal current carrying metal parts and/or the dirt.

[boB]

Eltek makes one.

http://www.eltek.com/wip4/detail_products.epl?id=1123815

I think they are only made for 48V battery systems (Telecom) but there might be one for 24VV as well.

Isolation will usually reduce the hardware conversion efficiency a little bit.

boB

[cardamon]

boB,

so generally it seems that most/all  of the common big name CC's are not isolated?  Is the Schneider  600V CC isolated because the high voltage change is best done with a transformer rather than non isolating techniques?

[boB]

>>>Is the Schneider  600V CC isolated because the high voltage change is best done with a transformer rather than non isolating techniques?<<<

 I haven't looked inside one of those so I'm not sure...  The newer TL inverters are not  isolated
and they are also more efficient.  Usually, not isolating it will make it more efficient, hardware wise.

Now you have me wondering...

boB

[cardamon]

As an electrician and a bit of a code geek, this is an interesting problem.  The NEC defines a" separately derived system" as  a premises wiring system with no direct electrical connection to conductors originating from another system.  This is an important concept because we "lose" our system grounding (if required - sometimes its not) if we go thru a transformer.  So its often unclear as power electronics become more prevalent, if these are isolating devices or not.  I suppose I could perform some electrical tests with a low impedance meter and find out.......It would be nice if UL required a device to be labeled as "isolating" or something like that.

[joestue]

Isolation will make a system more efficient when the voltage transform ratio exceeds some rational number.. probably in the range of 4:1.
however that number will increase as the price rises.