Charge controller problem - possibly

tomba

Hi all,

I've been charging a 24 V bank since the start of summer with a Morningstar SS20L-24V, using the Low Voltage Disconnect to switch off AC loads (I have no DC loads) with a relay wired inline with the power switch on my inverter. I have one 180W 45V OC SunTech panel and a 105 AH 24 V bank.

The LVD works well, if the battery voltage goes below 23 V for 3 seconds, the LVD on the SunSaver trips, until the batteries reach 25.5 V again, and you cycle the battery load (flip the breaker off then on again). I realize this is pretty conservative, but the idea is to provide idiot proof protection for the batteries. So far so good.

A new behavior of the CC that seems indicates all is not well is occurring. Recently, when the LVD trips, the red LED goes on, but the charge controller ceases to charge the batteries at all. If the LVD trips at night, no charging occurs at all the following day. I have to take the CC out of the loop and charge the batteries directly of the PV with a jumper wire until their voltage is back to 25.5 V, then reconnect the charge controller, whereafter it sees the reset voltage on the batteries, powers up the LVD load connection and all is back to normal.

This is not correct behavior for a CC with LVD, is it?

Thanks in advance for any ideas on this. My very own idea right now is to shop for another CC (maybe the 10A-24V version of the one I'm currently using), and possibly contact Morningstar to see if they are interested in seeing how/why this one failed.

mike95490

Re: Charge controller problem - possibly

The coil in the relay may have had some inductive "Kick" and zapped the charge controller. Relay coil = Spark plug coil.

BB.

Re: Charge controller problem - possibly

Snubber Diode, also known as a Fly-Back Diode.

-Bill

tomba

Re: Charge controller problem - possibly

Oh man, I didn't think about that at all. You're probably exactly right.

So maybe I'm shopping for a diode first, before the new CC.

tomba

Re: Charge controller problem - possibly

So the happy result of putting a protection diode across the coil in the relay is that the SunSaver now operates normally; it does not go into a non-charging state when the LVD is activated. At least, that is with one try. But every other time in the recent past that the LVD kicked in, I had to route around the SunSaver until my batteries were back. So things are looking up.

The bad (good?) of it this ProStar I have sitting here ready to replace the SunSaver is suddenly looking lonely. Though it does have monitoring which should be nice to see if I want to drop it inline.

Anyway thanks for the pointers! The simple diode is a critical addition to the system.

BB.

Re: Charge controller problem - possibly

I am surprised the Charge Controller LVD output did not have a snubber/fly-back diode... It is a very common killer of electronic I/O when connected to relays or other inductive loads (such has motors or even long wire runs).

Oh well--just another thing to the long list to warn/educate "newbies" about. :roll:

-Bill