battery disconnect switch

[defed]

what are you guys using as a disconnect between your charge controllers and batteries?  i was going to use a siemens 100a fused safety switch disconnect, but the thing is huge, don't really have room for it.  i am thinking now of using an in-line fuse and some sort of standalone switch, but not sure which one.  i see some 'marine' type (perko) and some are UL listed, but would like to know what others are doing.

thanks.

[clockmanFRA]

If not above 60v DC, as a safety device i use Hager NBN series MCB's. I wire them in parallel and stack them along side each over, ie, 2 x 63a gives 126amp etc etc.

I have learnt to click them on and off exactly together. 

[Rover]

Marine battery switch something like this...

http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=112462&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10597

Cheaper on E thingy.  I forget the ratings.. but they can easily handle boat motor starter current...

[Simen]

Or the simpler version for just disconnecting one battery:
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=440850&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10597

These can usually handle 100A cont., and there are metal versions that takes around 175A cont.

[defed]

i should have mentioned that it will be a 24v bank at up to 60a, which means i need to fuse/wire for 75a so as not to exceed 80% capacity as per NEC.

anyone have one of those perko dial types mounted in an enclosure of some sort?  i wanted to put the switch on the outside of the battery box, so it would be in the weather.

would the fuse go before or after the switch, or does it not matter?  would be nice to have that in the house, which would be before the switch.

[defed]

i wanted to use a QO breaker, but those max out at 70a for DC.

[thirteen]

what ever disconnect switch you get take an Ohms reading on the switch and put it on the wall and if you ever have problems with it you will have something to start with.  Just an idea to play with or file thirteen.

[wdyasq]

Check out MidNite Solar's mini-disconnects and breakers, over-current protection and cut-off in one package.  Also it is NEC approved.

Ron

[Volvo farmer]

[defed]

and this is how i reconnect it?  hahah!

[defed]

i got to thinking....do i even NEED a disconnect between the batteries and controller?  i mean, if i disconnect between the batts and controller, the panels are putting power to the controller, which is doing nothing anyway being disconnected from the batts.  i might as well just use the main disconnect before the controller?  in that case, i would just fuse the line between the controller and batts.

[Rover]

I actually thought about this quite a bit after your iniital post. I guess depends on he controller. Mine like to have the battery connected first followed by the PV (big warning about magic smoke and what not) , and PV disconected first ...

BZ controller 250 mppt , I think my blue Sky has the same verbage as well.

Right mow my PVs go to a terminal/barrier strip beforethe colntrollers, and I just pay attention to the disconect order, I probably should throw a switch in the the mix to make life easier

[defed]

i have the xantrex mppt.  the manual doesn't actually state a disconnect order, only that you shouldn't disconnect the batts while they are charging.  i usually use the array disconnect, as this still leaves the controller powered on.  the manual does show a disconnect on both sides of the controller, but again, i'm still not sure why i would need one after the controller.  if i want to cut power to the batteries, just use the main disconnect.

perhaps they don't want the controller installed/removed 'hot'.  but then that takes for granted that you have the disconnect in 'off' while hooking everything up!

[rossw]

I hunted around and found some 500A rated boat/RV switches, they're claimed to be good for 36V operation, but no information on 48V.
Given they're only isolating very low voltage differences (except for the last one - assuming I'm turning them all off), I didn't consider the voltage limitation to be a problem in my application.

They cost me about $10 each - identical switches sell for anything from $6 to $50 depending on where you get them from.

I have a 200A fuse between each switch and the battery bank it isolates as some protection - 200A should just let me run the inverter and handle full load off a single battery string if the others are offline for maintenance or testing etc. The switch actuators can be removed in the "Off" position for safety.



My FlexMax-80 charge controller has a seperate double-pole breaker for each array


and individual current metering. (Nominal 100V per array)


I've only isolated the batteries all together once since I powered the system up in 2005 - and as others have said, consideration of the sequence is important to avoid letting out magic smoke and preventing powerloss to critical services. In my case, it was:
  * Disable generator automatic controls
  * Power up generator
  * Allow inverter to synchronise and bring generator online
  * Add some "stabilising" load (around 1KW)
  * Cross fingers and toes shutdown inverter (critical loads maintained on generator)
  * Turn off DC input to inverter
  * Isolate PV arrays
  * Isolate turbine controller
  * Isolate batteries

On completion of works, the steps were basically the same ones in reverse. All completed without dropping 240V AC to critical loads, and no magic smoke

[defed]

i've been looking at those RV/marine type switches, and some say UL listed, but wasn't sure how to use them outdoors.  i'd think a marine switch is 'waterproof' already, and that mounting it in a box shouldn't be difficult...just wasn't sure.  not sure that the UL listing applies to residential use, but i guess at least it's marked.

as far as a disconnect between the batts and inverter, i personally thought it would be a good idea, but i was told on another solar forum that a fuse is all that is necessary.  if there was no AC load on the inverter and it was powered off, there would technically be no load on those wires.

i'm currently at 24v, but could move to 48v if i ever move up in inverter size.  will be using a 1000w or 1500w i think to start.