Thread: Dual Battery System

They don't look like relays to me, maybe fuses? although they do look chunky for 30amps. did you test voltages on both lugs?


Maybe I'll stay out of this one and let the other guys help out, they seem very knowledgeable

I googled the picture on fig 5 and it's apparently a circuit breaker. some are manual reset some are auto reset.
Didn't know you could get them that small.
Maybe one of yours are faulty?

ok first up..

those are not relays they are circuit breakers... these if over used will fail either fully closed or fully open or as a very high resistance if they burn their contacts.


what you need to do now is measure the voltage from both terminals of both circuit breakers to earth.

lets fault find only the circut breaker for the anderson plug first because doing so will let you wrap your head around the testing process

if the circuit breaker is closed (conducting current) then its terminals should both read the same voltage

if the circuit breaker is open the terminal closest to the battery (electrically speaking) will show battery voltage and the one closest to the load will show 0v.

so... if your battery voltage is 12.53 and the voltage on the terminal closest to the battery is 12.53 BUT the voltage is 0v on the other side of the breaker then its failed open. (thats what its ment to do dont panic yet) to confirm this put the meter directly across the 2 terminals of the circuit breaker. Assuming that you have nothing connected to the anderson plug what you really want to see is 0v but I'm going to guess you're going to see some kind of voltage. If you see anything more than about half a volt (and really you want a 0V reading) then you have a short in the wire from the output of the circuit breaker this is bad and needs to be fixed before you can safely replace the circuit breaker.

NOW...

my favorite trick.
go get yourself a minimum 50W headlight bulb. make up some connections on it to suit blade fuses (spade connectors) and then get some small aligator clips and put female spades on them so you can connect the light onto the terminals of your circuit breakers or onto other bits and pieces as you need to. This is your current limiter. its a Vital diagnostics tool. the advanced version includes a 10A circuit breaker like the one you have there.

AUTO SPARKIES MOST IMPORTANT RULE.

Before you screw around with a terminal thats hot or has a fuse you do not want to blow if you own spanners, fingers and eyesight that you value DISCONNECT ALL EARTHS from the battery. Then disconnect the terminal you want to play with and then put the earth leads back on AFTER you have insulated the hot cable you just removed.

because of the magic of electricery you can put your current limiter in the earth path and its still going to work BUT you can get some wierdo readings if you have other loads still connected.


Ok so now disconnect the lead from the circuit breaker and hook up your current limiter in place. with nothing in the anderson plug it should stay off. IF it comes on then you have a short, go track that down, remove it and thats the first half of the problem solved. you'll know you've removed the short when the light goes out.

to prove the concept (assuming that there is no short).. make sure you have the circuit breaker out of the system and only the current limiting light in place of the circuit breaker. Go and short out the anderson plug the light will come on, remove the short and tading. theres one of your most valuable fault finding tools for heavy current failures and blowing fuses.

Originally Posted by Aguy

Maybe I'll stay out of this one

yeah you could... or you could get involved

lets check the facts in play to support this.

you identifed the components
you identified a potential fault
you identified a valid test procedure.
You got there before I did.

It might just be me but thats 3/3 of the primary requirements for fault finding and rectification and picked up the bonus points of doing it quickly.

guys watch for a couple of edits in the main post of mine 2 back, I didnt like the way it read back so I clarified some wording on terminals for the diagnostics part.

I knew what I ment but there was a chance it could be misread

Dave,
Just want to say it sometimes seems that internet fora are the home of negativity put downs and arguing... It's nice to see some encouragement.

Damo89 your 99% of the way to fixing this... Lots of questions lots of good info provided and voila your knowledge will increase and your Landy will be healed

Steve

Dave,

I'm soon going to be installing the same kind of setup as Damo89 minus the second battery and minus the Anderson plug.
Do I need a fuse/breaker on the positive wire between the battery and NEW fuse block if it's only short? i.e, NEW fuse block will go in the same box as the battery.
If so, what would be a good reliable unit?

Yep, As a minimum you should have a fuse or manual reset circuit breaker, when I do the installs I stick in 2 layers of protection at each battery on each leg out of the battery a fuse as close to the battery as I can get it followed by a circuit breaker.

some basics.

total your maximum anticipated load thats the minimum rating that your circuit breaker needs to be the fuse should be 20% or the next largest rating over the selected circuit breaker or higher.

the reason for this is 2 fold

1. if the circuit breaker gets hot clicks closed and welds its contact its not protecting anything any more so the fuse will blow.
2. If you have a short you cant fix that repeatedly tripping the breaker you have a quick and easy way of isolating the circuit.

IF you're going to put in the same setup as Damo but arent going to put in a dual battery later on then you dont need the traxide but you DO need a low voltage cut out unit of some kind Or a switched relay to drop the load off of the main battery.