Charge Controller to Battery.. do I need a breaker or fuse??

ywhic · April 2012

I plan on running a MorningStar Pro 30 Controller.. and I will be putting a breaker/fuse on the inbound SOLAR voltage side... Do I need to put a breaker/fuse on the side going to the battery??

It says it has safety protection in both directions..

I will install a SWITCH between the controller and battery (for shutoff/safety).. but do I need an actual fuse/breaker??

Most drawings do not show one between the controller and battery...

I'll be running a 12v 200AH battery setup (2 T105's 6V in series).. with a 4AWG wire going to the battery (from the controller) and then back to the inverter (fused)

I DO know going from the battery to the inverter I need a breaker/fuse of like 150amp.. (1000 watt inverter)..

Any help would be apprecitated..

techntrek · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

You should have the fuse between the battery and the connection point (e.g. terminal block) for the inverter AND charger, with the fuse as close to the battery as possible.

vtmaps · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

When controllers fail, they become a short circuit across the battery. You do need a breaker there. --vtMaps

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

Ok..

So would a simple inline 60 Amp DC rated breaker/fuse work for that application (controller - battery)??

And CAN I mount it up near the controller as it would be easier to mount on something solid..??

I just re-read the MS 30 Amp Controller manual.. 6 AWG is the terminal size for the battery..

I'll run 4 AWG from the battery back to the inverter (with 150amp breaker/fuse) per the manual on that..

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

ywhic wrote: »

Ok..

So would a simple inline 60 Amp DC rated breaker/fuse work for that application (controller - battery)??

And CAN I mount it up near the controller as it would be easier to mount on something solid..??

I just re-read the MS 30 Amp Controller manual.. 6 AWG is the terminal size for the battery..

I'll run 4 AWG from the battery back to the inverter (with 150amp breaker/fuse) per the manual on that..

FWIW..

The length from the CONTROLLER to the BATTERY would be about 5'.. so 5' of 6 AWG..

Then maximum of 5' of 4 AWG from BATTERY to the XANTREX Pro PW1000 (Sine) Inverter.. 4' up wall.. then 150AMP breaker/fuse then another 1' (or less) lead to the inverter..

niel · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

as a battery can put forth vast amounts of current when a short occurs, the fuse or circuit breaker is to protect the wiring from overheating or possibly catching fire. for this reason it is recommended to have the fuse/cb as close to the battery as is possible. it may also help prevent damage to the battery by breaking the circuit when it becomes shorted.

now i don't know what an ms30 controller is, but it will be the max current rating x 1.56 and rounded up to the next highest commercially available value. now one can go lower in value to trip sooner just as long as the controller will not ever be outputting the new value while in operation. the idea is to kill shorting currents and not interfere with operations of the controller.

mounting the fuse/cb isn't always easy to do and many like it to be mounted on their battery box, but if you don't have one of those you may need to construct something to mount it safely to so as to keep it near the battery. it's also a good idea to have some way to prevent accidental shorts across the posts and can be a simple insulative cap on a post.

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

Niel..

Its a MorningStar Pro 30 Amp Controller..

So a 50-60Amp Breaker would work.. (based on 1.56*30 = 46.8amps).

I'll go with an Abs ICB60 Amp and mount it down low near the battery.. since its small (and nothing is moving) I should be ok.. reviews say its closer to 57 amps then pops.. but thats 10A above what I need..

Thanks..

niel · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

i believe it should be 50a as there are breakers and fuses that exist at that level.

here's an example,
http://www.solar-electric.com/30and50ampdc.html

edit to add: i guess i should add that i wouldn't mind using a 40a fuse or breaker if it were me as you aren't going to exceed the 30a controller rating anyway. the nec loves to put their crazy stipulations like the 1.56x thing and there are plenty of aftermarket fuses and mounts from the automotive industry. your choice.

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

Thanks..

I like the inline breakers as they can be SWITCHED using the breaker..

I appreciate the tips..

Looking to get into buying components starting next month.. (for the build in my signature)..

Vic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

Hi Albert,

Not a reply to your question, but, ... Technically, I think that a 150 Amp breaker on #4 AWG wire would often result in a bit of an overload on the wire. Breakers in this type of wiring serve the purpose of protecting the WIRE, not the equipemnt, from overload, heat builtup and possible fire.

Much depents on the insulation temperature rating, and weather the wiring is contained in a cable or conduit. If you need a 150 Amp breaker (and you may well due to surge current etc), and you are using 90 degree C rated wire, you might need to increase the wire size to #1 AWG, if the wire is in conduit. A single conductor #4 GA wire in free air is rated at 140 Amps max, so you could probably do fine with this, as this current cannot be continuous for a long time period.

Do not want to be too nit picking. This installation will probably not be inspected for code compliance. And it is possible that conductors larger than #4 AWG will not fit existing wire lugs on the inverter/breaker. Many unknowns (guesses on my part), and variables. Trying to make certain that you are aware of this point. Have Fun with the installation, Vic

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

On page 11 for the Xantrex Prowatt PW.. its says 500 CCA or less battery use ANL 150 fuse for the PW 1000 model (like I'll be getting)..

I don't see any CCA listed for the Trojan T-105 (which is what I'll be using in series)..

Another site said 110 Amp for upto 1000 watts.. using #4 wire..

Then I just found this ON this same forum.. (using google)

Say you have 2x 6 volt 220 AH "golf cart" batteries for a 12 volt @ 220 AH capacity, the maximum Inverter AC output load recommendation would be:

* 12 volts * 220 AH * 0.85 inverter eff * 1/8 max cont. current =280.5 watts max continuous (~8 hours or less to drain bank dead)
* 12 volts * 220 AH * 0.85 inverter eff * 1/2.5 max cont. current =897.6 watts max surge

----

So back the other chart a 60 Amp fuse/breaker would be fine upto 500 watts..

What size would you recommend?? The PW1000 unit output at max is 8.2AMP 115 AC.. if that matters..

ywhic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

ywhic wrote: »

On page 11 for the Xantrex Prowatt PW.. its says 500 CCA or less battery use ANL 150 fuse for the PW 1000 model (like I'll be getting)..

I don't see any CCA listed for the Trojan T-105 (which is what I'll be using in series)..

Another site said 110 Amp for upto 1000 watts.. using #4 wire..

Then I just found this ON this same forum.. (using google)

Say you have 2x 6 volt 220 AH "golf cart" batteries for a 12 volt @ 220 AH capacity, the maximum Inverter AC output load recommendation would be:

* 12 volts * 220 AH * 0.85 inverter eff * 1/8 max cont. current =280.5 watts max continuous (~8 hours or less to drain bank dead)
* 12 volts * 220 AH * 0.85 inverter eff * 1/2.5 max cont. current =897.6 watts max surge

----

So back the other chart a 60 Amp fuse/breaker would be fine upto 500 watts..

What size would you recommend?? The PW1000 unit output at max is 8.2AMP 115 AC.. if that matters..

I found a 100AMP breaker/fuse for use on 4 AWG wire.. that may be a smarter fit.. like you said 140 amp is the wire max.. 150 would be a little DUH.. IMHO..

Vic · April 2012

Re: Charge Controller to Battery.. do I need a breaker or fuse??

Hi Albert,

I am not exactly certain which Xantrex inverter that you are interested in ... perhaps it is the PW SW 1000. In any case, the cable sizes and breaker/fuse size would often be sized to the maximum surge current that your maximum load would place on the inverter. If you cannot determine this at the time you are ready to order parts, you could base this on the maximum surge current that the inverter can supply, and multiply this by some safety factor to add a bit of reserve. At very high discharge currents, battery voltage sags, especailly over a period of time. This lower voltage can result in increased battery current for the same abount of power delivered by the inverter.

Some of the nits that folks like me pick, are really nits. At times, all of us push the written limit on some things a bit. The wire ampacity ratings are written for long term continuous loads, so sometimes it is fine to overload a cable a bit. For systems that will be inspected, often one cannot get away with this little bit of cheating. Some of us also worry about insurance companies looking over our shoulders and so on.
Vic

Charge Controller to Battery.. do I need a breaker or fuse??

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