Dual Battery Wiring Mistake

[chartrock]

It's worrying how close I came to a major disaster through my wiring of a second battery. Just by chance, I went to see @boots33 to ask his expertise on the fitting of a Ctek 250S and we looked at the wiring in the tub for the 2nd battery.


The wiring was exposed through melted plastic along almost all the length although the extent wasn't seen until I pulled the wire completely out. I had the 2nd battery wired from the main battery through a fuse to an isolator (ABR brand) then to the 2nd battery. I figured as it was fused, all was OK. This cable carried current for the second battery and sometimes a Waeco fridge as well as the van battery through an Anderson plug. Obviously too much current and the wire overheated and melted the insulation. It did blow a fuse but I did not know that right away. Because the 2nd battery was connected and unfused back to the isolator, the melted insulation allowd the wire to short and virtually kill the 2nd battery and really overheat the wire.

I was just lucky the truck did not go up in flames. I have now replaced the ABR isolator with a Ctek 250S which limits current to 20 Amps, and fused both end of the line then added another fuse in the link to the Anderson plug to the van battery.


Thanks to Boots, :hail: I can put this up as a warning to other members not to make the same mistake.

 

[blacky]

Bloody hell well there ya go.. Thanks for the heads up mate. I think I'll fit a fuse at my auxillary battery as well now!

 

[Burnsy]

Hmmm, I think I'll fit a mega fuse straight off the terminal.....sparky said it wasn't necessary! Looks like it's all sorted now @chartrock......what size cable was it that melted?

 

[expanda]

It's worrying how close I came to a major disaster through my wiring of a second battery. Just by chance, I went to see @boots33 to ask his expertise on the fitting of a Ctek 250S and we looked at the wiring in the tub for the 2nd battery.
View attachment 19783 View attachment 19784 View attachment 19785 View attachment 19786

The wiring was exposed through melted plastic along almost all the length although the extent wasn't seen until I pulled the wire completely out. I had the 2nd battery wired from the main battery through a fuse to an isolator (ABR brand) then to the 2nd battery. I figured as it was fused, all was OK. This cable carried current for the second battery and sometimes a Waeco fridge as well as the van battery through an Anderson plug. Obviously too much current and the wire overheated and melted the insulation. It did blow a fuse but I did not know that right away. Because the 2nd battery was connected and unfused back to the isolator, the melted insulation allowd the wire to short and virtually kill the 2nd battery and really overheat the wire.

I was just lucky the truck did not go up in flames. I have now replaced the ABR isolator with a Ctek 250S which limits current to 20 Amps, and fused both end of the line then added another fuse in the link to the Anderson plug to the van battery.
View attachment 19787

Thanks to Boots, :hail: I can put this up as a warning to other members not to make the same mistake.

Wowser, looks like you saved yourself just in the nick of time!

 

[cruza driver]

Very, very lucky mate to get away with that mate

Probably could have sparked up at anytime too I guess.

 

[boots33]

Great to hear you got it sorted Paul and yes a timely reminder for us that all power sources must be fused. In the case of dual batteries it is very common to see people forget to fit a fuse to the second battery. I must say I was surprised to see no fuses shown in the wiring diagrams supplied with you cetec... interestingly the manuals available for download from their website do show fuses in the diagrams.

 

[Antman]

Lucky @chartrock .
Im just about to wire my CTEK up as well.

@boots33 can you tell me ( i have just downloaded the manual from ctek and still nothing about fuses on those manuals?) anyway, my setup is having the CTEK connected to my secondary battery in the car and then I have run 6B&S cable to an anderson plug at the rear that will connect the van.
I have got 40amp circuit breakers (resettable ones) to run on the 6B&S cabling however i don't have anything to run from the CTEK to the 2nd battery in the car. The wiring diagram does not state anything but are you saying I should fuse this also?

Thanks mate any info is appreciated.
Cheers
Ants

 

[gwadir]

You are so lucky @chartrock could've ended up a whole lot worse, I've placed fuses on both +ve and -ve lines myself and fused the Ctek as well, also running 6B&S cable to allow plenty of room for high currents if needed.

Dave

 

[boots33]

Lucky @chartrock .
Im just about to wire my CTEK up as well.

@boots33 can you tell me ( i have just downloaded the manual from ctek and still nothing about fuses on those manuals?) anyway, my setup is having the CTEK connected to my secondary battery in the car and then I have run 6B&S cable to an anderson plug at the rear that will connect the van.
I have got 40amp circuit breakers (resettable ones) to run on the 6B&S cabling however i don't have anything to run from the CTEK to the 2nd battery in the car. The wiring diagram does not state anything but are you saying I should fuse this also?

Thanks mate any info is appreciated.
Cheers
Ants

Hi Ants

In the ctek manual i downloaded the diagram on page 17 shows the fuses in the circuit. They are not marked in as fuses though so this could be a bit confusing.
On page 24 it gives the recommended fuse sizes as 30 Amp so that is what you should use and yes these fuses must be installed.

I have attached a modified version of the ctek diagram that represents (i think) what you are trying to achieve. I have marked in orange the original ctek fuse locations as well as the two required for your van hookup. While I have shown fuses in the diagram you can use your 40A breakers for the anderson lead and 30A non auto reset breakers for the ctek if you wish. All fuses/circuit breakers should be located as close as is practical to the power source they are meant to protect.

Shane

 

[cruza driver]

Hey @boots33,

So does the van battery and service battery need to be the same size? I think @Antman mentioned this in another thread.

I guess my question is will the cetek handle charging both batteries adequately?

And one more question while I'm at it as my past dual battery setups were for the older wiring vechicles, can you use the reset fuses where ever a fuse is requiered ?

Thanks in advance mate

 

[Antman]

Hi Ants

In the cetec manual i downloaded the diagram on page 17 shows the fuses in the circuit. They are not marked in as fuses though so this could be a bit confusing.
On page 24 it gives the recommended fuse sizes as 30 Amp so that is what you should use and yes these fuses must be installed.

I have attached a modified version of the cetec diagram that represents (i think) what you are trying to achieve. I have marked in orange the original cetec fuse locations as well as the two required for your van hookup. While I have shown fuses in the diagram you can use your 40A breakers for the anderson lead and 30A non auto reset breakers for the cetec if you wish. All fuses/circuit breakers should be located as close as is practical to the power source they are meant to protect.

Shane

Sorry @chartrock for stealing your thread

@boots33 you are the king! Thank you very much. Very clear on exactly what needs to happen.
Thanks so much it is really appreciated.

And you were right I just went back and had another look at that manual and they are there. I guess its assumed that someone with wiring diagram knowledge would be installing as those fuse icons meant nothing to me. The reason why professionals should install your products I guess.

While I have you, I also got the relay that gets hooked into the start of the car. I think this is just if you are going to hook up solar?? But not sure. Have you seen this? If so, am I actually required to have this installed if I am not going to use the solar part of the unit?

I run all my cabling on the weekend and am going to get an auto sparky to install the reley but if i don't need it i can save some coin thats all.

Cheers mate,
Ants

 

[cruza driver]

Dont worry @Antman as @chartrock is at Tassie he wont know

 

[Gadgets 21.63.1]

i run a 4guage cable from the second battery down to the rear where the anderson plug is, but only run a 20 amp self resetting breaker and a 25amp fuse as a backup. never had a problem, but if i short the ends out, the breaker trips and alls good. the fuse is just incase the breaker fails.

 

[boots33]

Hey @boots33,

So does the van battery and service battery need to be the same size? I think @Antman mentioned this in another thread.

Ideally when hooking batteries up in parallel they should be identical, same brand ... same type of construction and same capacity, this will achieve the best performance overall. If you were starting from scratch then you should try and do that. Having said that just about any combination will work with varying degrees of success. Mixing batteries of different amp-hour ratings is ok (within reason) as the charger will just see them as one big battery and they will discharge and charge at the same rate. Of more concern is battery construction or type, it would not be a good idea for example to mix a calcium battery with an AGM battery as they have have quite different requirements when it comes to charging. you should also use deep cycle batteries for your Auxiliary work. It is also very important to use sealed batteries if the batteries are to be fitted in spaces with little ventilation. AGM or Gel batteries are best suited to this task.

I guess my question is will the cetek handle charging both batteries adequately?

Sorry for my bad spelling in my original post, getting me all confused now

The Setec that comes standard with our jayco's is tasked to do a lot of things at once. It has to be a constant supply for when we are on 240v as well as keeping the battery topped up and ready for when we are off grid. It also has to allow for the fact that it could be connected to 240v power permanently and must do this without overcharging the battery. While there are no doubt other units out there that will outperform the setec i have never had any problems with mine keeping up to my needs. If you have a very large bank of batteries or are heavy power users then you may need to consider an alternative but for most of us it does an adequate job.

And one more question while I'm at it as my past dual battery setups were for the older wiring vechicles, can you use the reset fuses where ever a fuse is requiered ?

Buy reset fuse do you mean circuit breakers, if so then in most circumstances yes you can. they can be a lot more convenient than carrying around a bag of fuses.

Shane

 

[boots33]

While I have you, I also got the relay that gets hooked into the start of the car. I think this is just if you are going to hook up solar?? But not sure. Have you seen this? If so, am I actually required to have this installed if I am not going to use the solar part of the unit?

I run all my cabling on the weekend and am going to get an auto sparky to install the relay but if i don't need it i can save some coin that's all.

Cheers mate,
Ants

Can you give me more details as to where and what this relay does. As far as i can see there is no mention of it in the ctek instructions. With or without solar you should need nothing more than what is shown in the diagram above.

 

[boots33]

Dont worry @Antman as @chartrock is at Tassie he wont know

Hey cruza when he dropped in on his way south did he say if he was going to use the method i suggested in this thread to save on the ferry crossing.

 

[cruza driver]

Haha we had a laugh about that pic actually, he wasnt confident it would be a success

And a massive thanks for answering my questions mate

 

[navmatt]

Can you give me more details as to where and what this relay does. As far as i can see there is no mention of it in the ctek instructions. With or without solar you should need nothing more than what is shown in the diagram above.

The relay is used for cars with "smart" alternators, using the relay on the solar input. If you have a smart one and no solar just wire directly to the solar input. If you have solar as well use the relay...The solar input on the C-Tek is designed to provide decent output power even at reduced input levels (correct voltage just less amps - battery will still charge properly, just more slowly).

 

[navmatt]

this is because the alternator input of the ctek is designed to be receiving a full load from the alternator & once the smart electronics kick in & drop alternator voltage, its no longer got the power to do what it designed for?
But the solar input is designed to still work well at lower voltages.....

 

[Antman]

Can you give me more details as to where and what this relay does. As far as i can see there is no mention of it in the ctek instructions. With or without solar you should need nothing more than what is shown in the diagram above.

The relay is used for cars with "smart" alternators, using the relay on the solar input. If you have a smart one and no solar just wire directly to the solar input. If you have solar as well use the relay...The solar input on the C-Tek is designed to provide decent output power even at reduced input levels (correct voltage just less amps - battery will still charge properly, just more slowly).

Hey @boots33 and @navmatt
Thanks guys that is great to know. Boots33 see the image attached for the actual wiring diagram of the relay that i got with the ctek.
Navmatt, im not sure what you mean by if you have no no solar just wire directly to the solar input??? I would have thought, if no solar than no need to wire in the relay and just leave the solar one empty or do you wire the ignition straight into the solar input?

again thanks guys.
Cheers
Ants