Solar controller question

RSD7a

RSD7a

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Why is it important to connect the solar controller to the leisure battery first and then to the solar panel?

I've just had to disconnect the negative pole on my leisure battery because I needed to fix a broken connection. When I reconnect the negative terminal on the leisure battery, does this mean as far as the solar controller is concerned, I have effectively connected the battery to the solar controller after the solar panel (which has remained connected all the while) and therefore messed something up?

My question makes sense to me at any rate 🤣
 
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The battery must be connected to the charge controller first, because that is how the controller receives its operating power. Without operating power applied first, the solar panel output will harm the controller.
You may find that disconnecting the controller then reconnecting will sort this out.
But you may have damaged the controller.
 
I think it unlikely that any damage has been caused. An open circuit condition will have been considered during the circuitry design.

With some regulators, for instance Victron, they are capable of supporting 12v or 24v batteries. In this instance it's important to connect the regulator first in order to configure it for the correct battery voltage.
 
Fisherman said:
The battery must be connected to the charge controller first, because that is how the controller receives its operating power. Without operating power applied first, the solar panel output will harm the controller.
You may find that disconnecting the controller then reconnecting will sort this out.
But you may have damaged the controller.
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I have fitted a few vans with Solar and never seen that reason, makes perfect sense though, I was told on my first install it was so the controller could see the battery, and that was by a pro installer too.
 
It is not something I have "investigated", but one possible reason to always connect a battery first is that it's there to take a load when the solar lis connected and is providing current, so acting as a bit of a power dump to avoid any spikes?

As far as the Victron controllers go, it is important that the battery is connected first the very first time it is powered up so it knows what battery voltage system it is talking to, but once done, that is remembered unless a full factory default is carried out. So after that first time, I wouldn't worry too much (in fact, one of my Victron controllers had a dry joint on the battery connection which meant it lost the battery power repetitively and the controller worked just fine during the day providing power via the Load Circuits and then often shut off at night time (or with a dark cloud :) as had no power in ). Went on for weeks until I found the fault and now resoldered, been good for many months since.


In fact, thinking about it, anyone who has a battery isolation switch (which is always a good idea) and has used it when working on their system will have removed the battery supply from the solar controller in the process whilst the PV panel was still connected.
 
RSD7a said:
Why is it important to connect the solar controller to the leisure battery first and then to the solar panel?

I've just had to disconnect the negative pole on my leisure battery because I needed to fix a broken connection. When I reconnect the negative terminal on the leisure battery, does this mean as far as the solar controller is concerned, I have effectively connected the battery to the solar controller after the solar panel (which has remained connected all the while) and therefore messed something up?

My question makes sense to me at any rate 🤣
Click to expand...
The question makes sense. Many of the answers I've seen over the years on this subject, less so.

There are two reasons given.

One is that the controller can't cope with power from the panels when there is no power from the battery.

If that's true, it's due to appallingly bad design of the controller. A controller that would be destroyed by a fuse blowing is a badly designed controller.

The other reason, which makes only slightly more sense, is that many controllers can charge 12v or 24v batteries and if only the panels are connected on power up, it can't tell what voltage the battery is.

The problem with this argument is that mppt controllers reassess the input and output voltages all the time. They are designed to cope with changing voltages within a range. The battery voltage ranges for 12v and 24v systems don't overlap. I think that any controller should be able to set itself when connected panels first.

I have only actual experience of three brands of mppt controllers at home, but with all three I have routinely unplugged one battery bank then plugged another in. Never had any problems at all doing that.

Damp. That's what I've had problems with. Even in supposedly sealed "dry boxes" I've had controllers die of damp. I guess that inside a motorhome they'd be fine.

It's worth noting that you are supposed to connect the battery first. My experience that it doesn't matter does not mean it's officially safe
 
Nabsim said:
From memory (admittedly dodgy) both my Victron and Votronic controllers said connect battery first so the controller detects battery voltage.
Click to expand...
correct

4.5. Electrical connections
Make all electrical connections in the following order:
• Turn off all DC loads, then connect the loads to the load output of the solar charger. Torque moment 0.75Nm.
• Confirm correct battery polarity, then connect the battery (this will allow the solar charger to recognize the system voltage). Torque moment 0.75Nm.
• Connect the VE.Direct communication cable (if applicable).
• Confirm correct PV polarity, then connect the solar array. Torque moment 0.75Nm
If accidentally connected in reverse polarity, the PV voltage will drop and the controller will heat up but will not charge the battery.
• In case a MPPT WireBox is used:
First: Secure all electrical cables as indicated in the WireBox installation instructions
Then: Place the WireBox plastic cover over the solar charger connection area and secure it.
 
I have seen two instances where those awful blue £3 (often sold as MPPT) PWM controllers sold by scammers on on eBay have destroyed batteries through overvoltage which caused them to boil and off gas significantly. in one van the battery case burst and there was a lot of related damage.

On each occasion it was in Caravans without any isolation fitted only the main habitation power control panel thing which had been turned off without isolating the PV input and at some point the controllers had both decided to default to 24V and when the habitation switch was turned on they pumped 18v+ into the batteries.

It's always always a safe rule of thumb to disconnect PV input before isolating the batteries and to connect the batteries first before connecting the PV input. some controllers may well be resilient to not doing so but it is often mentioned on the instruction manual and why risk it.

My spare Ecoworthy controller I use in my garage makes a fair old hissing noise when PV only is connected, it' not happy at all, but it's also a bit of a weird unit no auto sense

This problem may well apply more to Caravans and people with Coach builds because usually self builders are encouraged to install separate Isolators for battery, PV in/out and Inverters.

There's no need to go ott with heavy duty switches either for very occasional isolation simply fitting and being able to pull a Maxi fuse is perfectly adequate
 
Thistle said:
I have seen two instances where those awful blue £3 (often sold as MPPT) PWM controllers sold by scammers on on eBay have destroyed batteries through overvoltage which caused them to boil and off gas significantly. in one van the battery case burst and there was a lot of related damage.

On each occasion it was in Caravans without any isolation fitted only the main habitation power control panel thing which had been turned off without isolating the PV input and at some point the controllers had both decided to default to 24V and when the habitation switch was turned on they pumped 18v+ into the batteries.

It's always always a safe rule of thumb to disconnect PV input before isolating the batteries and to connect the batteries first before connecting the PV input. some controllers may well be resilient to not doing so but it is often mentioned on the instruction manual and why risk it.

My spare Ecoworthy controller I use in my garage makes a fair old hissing noise when PV only is connected, it' not happy at all, but it's also a bit of a weird unit no auto sense

This problem may well apply more to Caravans and people with Coach builds because usually self builders are encouraged to install separate Isolators for battery, PV in/out and Inverters.

There's no need to go ott with heavy duty switches either for very occasional isolation simply fitting and being able to pull a Maxi fuse is perfectly adequate
Click to expand...
The votronic has a fuse fitted which can be pulled if required.
solar duel a.png
 
RSD7a said:
Why is it important to connect the solar controller to the leisure battery first and then to the solar panel?

I've just had to disconnect the negative pole on my leisure battery because I needed to fix a broken connection. When I reconnect the negative terminal on the leisure battery, does this mean as far as the solar controller is concerned, I have effectively connected the battery to the solar controller after the solar panel (which has remained connected all the while) and therefore messed something up?

My question makes sense to me at any rate 🤣
Click to expand...
It’s simply so any ‘Immediate’ power surges after connection of a ‘Power Source’ can be ‘’Controlled’ at a guess 🤷🏻‍♂️.
Has anyone noticed how I use a lot of ‘Inverted Commas’ when I post.
Even ‘I’ Find that annoying folks !. So thanks for ‘Putting Up’ with that Guys 👍😊
 
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