Backup charger for a battery bank

Everlong

So I have a small setup, 2 sharp 24v panels, 4x12v batteries and an mppt controller. For what I use it- pot lights outside under the soffit it works and charges just fine. In the summer:) in the winter sometimes with the snow fall it doesn't. I can't clean them cause they are to high. And I can't also move them. My question is, is there a "backup" charger available anywhere that will kick in when the voltage of my 24v bank will drop too much?

Blackcherry04

Re: Backup charger for a battery bank

For my part the ones I found that work best are the IOTA dls- 27-25. I prefer getting the plain model and getting the IQ-4 module as a plug in, gives you more flexibility. There is also a way to turn up the output on them to be able to Equalize your batteries.

Everlong

Re: Backup charger for a battery bank

Ok, im not too clear how they operate. Will they automaticaly kick in once the voltage drops? Or will they constantly charge/maintain once plugged in?

Blackcherry04

Re: Backup charger for a battery bank

Everlong wrote: »

Ok, im not too clear how they operate. Will they automaticaly kick in once the voltage drops? Or will they constantly charge/maintain once plugged in?

They do both. When the voltage drops they will increase their voltage and current to maintain the charge, once the reach they finish the Absorb stage, they then switch to the float voltage and maintain it. You can plug them in or unplug them at anytime. In the case of the IOTA you have to have the IQ-4 option to get them to do that. It's available 2 ways ( Built in or as a plug in ) I like the plug in.

vcallaway

Re: Backup charger for a battery bank

The IOTA is going to draw power and want to keep the batteries up all the time. It is a great charger but will not do what you ask standalone.

What you are asking for is a relay driver that will turn it on at a set voltage point. I believe Morningstar has something that works with their system. You didn't say what controller you had.

Blackcherry04

Re: Backup charger for a battery bank

vcallaway wrote: »

The IOTA is going to draw power and want to keep the batteries up all the time. It is a great charger but will not do what you ask standalone.

What you are asking for is a relay driver that will turn it on at a set voltage point. I believe Morningstar has something that works with their system. You didn't say what controller you had.

I'd consider a " Stand Alone " charger just what the IOTA is. If your talking about being able to control the AC input of the charger by a controller of some type with a low voltage connect and a high voltage disconnect I am sure that there is a controller out there that could do that. For a price today, most anything could be had. A latching relay on the auxiliary contacts of a charge controller could do it.

Everlong

Re: Backup charger for a battery bank

http://www.soltronic.de/shop/themes/kategorie/detail.php?artikelid=4&source=2&refertype=1&referid=&languageid=2 have a German controller, its either available through ebay or through their web site, hete is the link

Blackcherry04

Re: Backup charger for a battery bank

Here is a Voltage Controlled Switch that would turn a charger on at a set low voltage and then would turn it off at a set high voltage. It has a 3 second delay built in, that would keep it from fluttering. So, if you set it at 23 V to turn on and then to turn off at 27 V, that would turn the charger on and off. The IOTA would still be the best charger, you wouldn't need the DLS controller because you are controlling it with the voltage switch. You would want the " Active Low " version.

http://www.solar-electric.com/volconswit.html

You could also use this same switch to start a generator, then the charger would come on as long as it was running. You never said if you have grid power or not. There is no end to the automation you can add to your system, it all works until it doesn't. Remember that your loads will pull your voltage down, so don't set the voltage cut on to High ( false starts ), it will be turning on and off to much, 3 seconds is really to small a delay, but it is what it is. You could probably find a delay timer to put in-line that would extend that, just another brick.
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Everlong

Re: Backup charger for a battery bank

Blackcherry, yes I'm connected to the grid. I'm planning on adding more solar panels and more batteries and wouldn't want to kill them within its first year of operation.

Blackcherry04

Re: Backup charger for a battery bank

Everlong wrote: »

Blackcherry, yes I'm connected to the grid. I'm planning on adding more solar panels and more batteries and wouldn't want to kill them within its first year of operation.

I'd say that the Voltage Switch would work fine for want to do. I'd take a short power cord and have a male & female plugs where you just plug the charger in to the switch. That Switch also has a NC ( Normally Closed ) contact, that you could use to switch a Load off the batteries when the charger was on. Just some thoughts.

Just in case you decide that the VCS will work, this will apply to it if you use it for 120 V.

IMPORTANT: If the relay is to be used to for over 48 VAC or 63 V DC service, remove the 2 blue varistors under the
black relay. These are used for ARC quench in the DC uses of the relay and are not needed for AC operation of the relay.
Once removed, the unit can safely and properly switch 115 V AC service.
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