Battery cutoff with solar

I guess I'll let my ignorance shine here, but..... the controller's wired in between panels and batteries, both have varying degrees of volts and amps the controller interprets. I presume how big the differences are are what the controller uses to make it's adjustments to do it's job. Bottom line is that electricity is "coming at" (for lack of proper term) the controller from both sides. Granted even with small voltage differences things should move towards the battery but disconnecting either one first still leaves the controller hooked up to power. What's it matter whether it's panels or battery first?

pianotuna wrote:
Hi Joel,

For some controllers running without the battery connected may let out the magic blue smoke.

Joel_T wrote:

smkettner wrote:
No switch. My RV runs 24/365 on solar. And with 510 watts you should not have an issue. Off is fine too.

Always cut power from panels before you disconnect controller from battery.

What's the danger....overloading the controller? I have a fused breaker before and after the controller and shut the one off between controller and batteries occasionally so I can measure true panel output without the battery influence.

I used the cutoff switch while replacing my batteries last weekend, and suddenly heard that rising pitch whine that usually means smoke escape is imminent. I forgot to shutdown the solar first. I think I got lucky. Everything appears to be working.

Joel,

Many controllers can do either 12 or 24 volts. That is one good reason to do the batteries first on connection.

2oldman wrote:

smkettner wrote:
Controller is designed to charge a battery not to be an open power supply. And when I pay $500 for a piece of equipment I try to go by the book. So read your manual..

x2

My Outback controller manual is clear about connecting batteries first.

LScamper wrote:
Just wondering what happens if the battery fails in an open condition. Will it destroy the controller?..so I can measure true panel output without the battery influence.

I don't know, but that's extremely unlikely, unless one likes to keep one's batteries until they die.

I'm not sure why knowing the 'true panel output' sans batteries would be of any value.

I don't check the panel output often but understanding what shade, clouds and tilt and whatnot have on true output can't be had with the batteries in the circuit.

The only thing I found in the different manuals was typical. It said to disconnect batteries and solar panels before wiring up the controller. Then, verify wiring and polarity. Then "close the switches or circuit breakers." No mention of a particular order. What you guys are fearing is reasonable. I'll check back when I hear from Bogart.

I had a last look this spring at the first set of panels I owned, before the old 1987 class C was towed to the wrecking yard. The panels were from 1992 and were still working just fine.

2oldman wrote:

I'm not sure why knowing the 'true panel output' sans batteries would be of any value.

In theory, one might want to check the panel health if suspecting something. In practice, panels made in the last 10-15 years rarely fail.

Besides, if panel fails, you will see a lot of changes in panel voltage with battery connected. All you need is another voltmeter or a battery monitor that could read both input and output voltage. Controllers over $300 often have their own display with both input and output voltage.

smkettner wrote:
Controller is designed to charge a battery not to be an open power supply. And when I pay $500 for a piece of equipment I try to go by the book. So read your manual..

x2

My Outback controller manual is clear about connecting batteries first.

LScamper wrote:
Just wondering what happens if the battery fails in an open condition. Will it destroy the controller?..so I can measure true panel output without the battery influence.

I don't know, but that's extremely unlikely, unless one likes to keep one's batteries until they die.

I'm not sure why knowing the 'true panel output' sans batteries would be of any value.

Joel_T wrote:

smkettner wrote:
No switch. My RV runs 24/365 on solar. And with 510 watts you should not have an issue. Off is fine too.

Always cut power from panels before you disconnect controller from battery.

What's the danger....overloading the controller? I have a fused breaker before and after the controller and shut the one off between controller and batteries occasionally so I can measure true panel output without the battery influence.

My manual says so. I believe others do also. Controller is designed to charge a battery not to be an open power supply. And when I pay $500 for a piece of equipment I try to go by the book. So read your manual.

Panel Voc can be measured when disconnected from the controller.

LScamper wrote:
pianotuna wrote:
"For some controllers running without the battery connected may let out the magic blue smoke."

Ahhh, the wife would probably enjoy pretty blue smoke....me, not so much :B I emailed Bogart Eng questioning my habit on their SC2030 controller. We'll see.

pianotuna wrote:
"For some controllers running without the battery connected may let out the magic blue smoke."

Just wondering what happens if the battery fails in an open condition. Will it destroy the controller?