Faulty charge controller ?

If the controller is one which automatically recognizes the battery voltage, it might have glitched and chosen 24 volts instead of 12 volts (for example) during the time it was disconnected from and reconnected to the battery.
More important, most CCs which use microprocessors as overall control require that you always connect the CC to the battery BEFORE you connect the panels to the DC input. That allows the CC to reboot correctly and be stable when the input power becomes available.
Applying DC before connecting to the battery will have unpredictable results, but almost always bad.

If you Renology CC tells you to connect the panels first, then I do not have any explanation.

Hi semper..,

I have no direct experience with the Renology Charge Controllers (CCs). But, generally, one would switch off the PV input before ever switching the battery connection off. AND, when powering the system back on, switch the battery BREAKER on first and the PV on, second.

Hope that you are suing a circuit breaker that is rated for DC, at least on the battery connections to the CCs -- this is a safety issue. A good breaker can act as a Disconnect (switch), as well as protection for the cables connections to and between the batteries.

May be reading too much into your post. Good Luck, Vic

Hi Jake,

So, yes, there really needs to be a circuit breaker or a fuse for every connection to the battery. In the case of the Charge Controller (CC), you should also have what is called a Disconnect -- a switch. So, you can get both of these in one item by using a circuit breaker. These safety items protect the wires that connect things like Inverters, CCs and any other item that connects to the battery.

The fuse or circuit breaker protects against a fire, because, when shorted, batteries can produce huge currents into a short circuit for some period of time, often, long enough to even melt the wiring or, at least get it very hot. This is the fire hazard.

The fuse or circuit breaker needs to be rated for the voltage of the circuit, and, it needs to be rated for DC use. Ideally, the circuit breaker should have a large Interrupting Current rating (something like 5kA).

The very common Square D QO circuit breakers are rated for use in DC systems,. On the battery side, the practical battery voltage limit is 24 VDC. AND, the largest QO breaker that has this DC rating is the 70 Amp unit. For the PV input to the CC application, The maximum voltage would be 48 VDC.

AND, if one is looking in the Big Box stores for panels and breakers, stick to a Square D QO Panel (not the Homeline), and ONLY single, dual breakers, as well as the triple breakers, which are not commonly found in the Box stores. If you use single breakers, the range of breaker current ratings that will work on DC is, 15 to 70 Amps, and only for breakers that do not have two "handles" for a single breaker location in the breaker panel -- this type of breaker is called a Tandem breaker.

The less complex approach for DC rated breakers is to use the MidNite Solar line of breakers, and mount these breakers in a MidNite box.

Here are some breakers and boxes from the sponsor of this website:

http://www.solar-electric.com/instal...br1/mnepv.html

EDIT: When choosing the size of breakers, since their job is to protect the wiring that connect to them, one needs make certain the cable will not exceed its maximum temperature at the current rating of the breaker. Usually an Ampacity Table is used to determine these current ratings, for the temperature rating of the wire.

http://www.solar-electric.com/instal...obigbabox.html

Sorry to make things seem a bit complicated. There are a lot of variables in these systems, and where batteries are involved, having good, safe protection is very important.

More later, The above are my opinions, Good Luck, Vic