3RD battery questions

[07luxyTD]

Thanks Mark

[07luxyTD]

Righto with the canopy almost being ready to get thrown on the truck in a months time or so ive gotta put a 3rd battery in for canopy itself. Current system is a ctek dual 250s, with a century 100ah marine under the bonnet. So a few options ive been looking at is running a smart pass doubled onto the 250s and connecting the 3rd battery so it just thinks the 2 batteries are one big one. Or adding as Alby suggested earlier a 3 way switch (pretty sure i have 1 laying around some where ) But the 1 big con is when i take the canopy off, dosnt matter where i have the charger mounted in canopy or truck 1 battery is going to go without charge untill i put it back on again.

So what i can think of for the solution is to leave the charger in the car with a 3 way switch to swap over to the 3rd battery when canopy is on. And mounting a solar regulator and pannels in the canopy for the 3rd battery when the canopy if off. Also a ac/dc charger in the canopy when at van parks and stuff. Can anyone see a down fall in this design?

[Alby]

The main problem I see is that your longest run of cable that will suffer the most voltage drop is your third battery in the canopy so ideally your Ctek should be next to it plus you will have to purchase another solar regulator

[Skog07]

The main problem I see is that your longest run of cable that will suffer the most voltage drop is your third battery in the canopy so ideally your Ctek should be next to it plus you will have to purchase another solar regulator

X2 which is the reason my ctek will go into the canopy. Cranker gets the load first aux and ctek will get current afterward. The only thing is my first aux batt will only get charged to the lower voltage, will have to bring the wiring diagram from the dummies thread when I get a chance.

[07luxyTD]

Thanks fellas, i did have a look at your diagram Mark and still have my old isolator in the shed somewhere. Was thinking if i could charge both batteries to 100% or close to then i probly should. The run from the ctek to the canopy is 3.5mtrs which the ctek manual doesnt look like it agrees with doing so as the cable sizing is blacked out after 2mtrs Im thinking with 10mm2 it should be alright tho, might loos 5% all up.

Maybe i should just invest in another ctek and throw it in the canopy But still have the 2 chargers on a 3 way switch to save loading the alternator right up. Its starting to sounds like the best option, solar option for both batteries, chargers mounted close to battery, spare if 1 fails and the ctecks arnt over overly expensive for what they are and do.

[Skog07]

Was thinking of running a switchable and fuseable loop back over from the + ve out on the Ctek back to the alternator feed side on the Ctek unit. Which should also charge up the Aux 1 Batt up to the higher voltage. The isolator from the cranker should keep the ctek away from the cranker but get the Aux 1 Batt up to 100% ?

[07luxyTD]

Would the ckek in turn tho draw some of its own output and result in a much higher voltage drop? Sounds like charging a battery with the battery you want to charge. I'm only an amateur when it comes to this stuff tho.

I know there's alot of variables but could anyone tell me the formula for voltage drop?

[ng_newbie]

Hey 07

I thought this would be to do with resistance, it is, but more to do with temperature & distance traveled

To calculate voltage drop in a copper wire, use the following formula:

Volts= Length x Current x 0.017
Area

Volts= Voltage drop.
Length= Total Length of wire in metres (including any earth return wire).
Current= Current (amps) through wire.
Area= Cross sectional area of copper in square millimetres.

Notes:
• This formula only applies to copper at 25°C, voltage drop increases with wire temperature, at approx 0.4% per °C.
• 0.017- This figure only applies to copper.
• Area is in square millimetres of copper, there can be confusion on how cable size is rated, with some manufacturers stating wire diameter rather than area, some even including the insulation. An explanation of this can be seen at:
http://www.motorhomesaustralia.net/cable.html

HTHs

NG

[Alby]

Before I new about DC/DC chargers I ran 2 B&S cabling to the tray to counter voltage drop but that is only part if the problem, the other issue is the alternator going into sleep mode so it doesn't fully charge your second battery, a few of the electrical gurus here state only 80% charge status

[ng_newbie]

Hey Aqua

I notice you have what look like really big fuses in this picture

Notice the labels 1 , 2 , 3 what are these ???



Also were did you get the short thick cables for the batteries that feed into these ???

I have never seen them in supercheap

TIA

NG

[Skog07]

No. 2 is a shunt. It's on the negative side and is used to measure current. I've got a smaller jaycar version in mine hooked up to an ammeter.

[ng_newbie]

G'Day Skog

The more I learnt about this the more of a Newbie I become

So then 1 & 3 are big fuses ???

Do you know the best place to get the fuses & the short batt. cables that I would need to install them ???

TIA

NG

[wholehog]

a alternator diode will boost your charging rate sufficiently to achieve a 100 percent charge...fit an isolator like an SC80or the like from traxide and u won't look back...all for a total cost of about 200 bux.cheers

[Skog07]

I think so? They look like Mega fuses.
Here is Aquas post a few replies up.

Post by Aquaholics on Thu Nov 08, 2012 5:46 am

Thanks Qwerty, it hasn't come up too bad. I am running a Victron Energy BMV-602s which monitors the voltage of both batteries and detailed monitoring of the service battery. Through a 500amp shunt it records and reports voltage, the rate of charge and discharge in amps, estimated state of charge (%), Ah consumed, approximate time to go and all sorts of other stuff I haven't found a use for. It will also alarm or activate a relay at pre-set values if I required but the Ctek's do that for me already.

[Aquaholics]

Hey Aqua

I notice you have what look like really big fuses in this picture

Notice the labels 1 , 2 , 3 what are these ???

Also were did you get the short thick cables for the batteries that feed into these ???

I have never seen them in supercheap

TIA

NG

Hi NG,

Yes 2 is the shunt and 1 and 3 are mega fuses in a "fuse block MEGA with cover" from Baxters. Part number ELF-MEGA.

Baxters are an electrical wholesaler (in all states of Oz) but will sell to the public if you are buying more than just a fuse or something small. I put my shopping list together and went in and got everything I was after at wholesale prices. Worked out much cheaper than ebay and without the delay and huge freight costs on 2BS cable.

The short cables I made up myself. $100 for a hydraulic crimp tool from Baxters while your there then ebay it when your done if you don't think you will need it again.

Oh and skip their website its crap, just call them or go in and see them with a shopping list.

Hope that helps.

[ng_newbie]

Hey Aqua

I contacted Baxters

I missed this the 1st time around & emailed them !!!

Oh and skip their website its crap, just call them or go in and see them with a shopping list.

Here is the reply for anyone wanting to make up their own cables etc.

"As Baxters is a wholesale supplier we do not sell cable in one metre lengths. All our cable is rolls of 50 or 100 metres. Cable connectors are sold in quantities of 10 or 25 depending on the size you require. The fuse holders are $22-68 and the crimp kit is $79-65. Prices are plus GST and stock is available."

So you must have bought the cables from someone else or did you buy 50 metres ???

TIA

[Talktheroo]

The main problem I see is that your longest run of cable that will suffer the most voltage drop is your third battery in the canopy so ideally your Ctek should be next to it plus you will have to purchase another solar regulator

X2 which is the reason my ctek will go into the canopy. Cranker gets the load first aux and ctek will get current afterward. The only thing is my first aux batt will only get charged to the lower voltage, will have to bring the wiring diagram from the dummies thread when I get a chance.

You are supposed to mount the Ctek 250 dual unit as close to the auxiliary battery, as possible.
There are a couple of options for installs in the rear.
Jamie makes a really good box, and Derek has a really good tray to sit it on. Just use the Anderson plug provided, and this makes the auxiliary totally portable.
Links : http://www.jtsonline.com.au/12-volt-pro ... meter.html
Tray link : http://www.sidewinder.com.au/page158a.html
The Roo.

[Aquaholics]

So you must have bought the cables from someone else or did you buy 50 metres ???

I think the 2BS rolls are 30m from memory. I bought a roll as I am running my CTEK's behind the back. I also wanted to be able to plug the portable compressor in at the back of the car, it draws about 60amps hence the mega fuses.

[Skog07]

Thanks Roo.
I have the battery already in a Bias Marine battery box. Which is similar to the first link. Nice setups BTW. The ctek is mounted in the canopy and is less than a metre away from the third battery and has 2BS cable between the ctek and battery. Its about a 5 metre run from the aux. under bonnet in 2BS cable to the ctek unit.

[VMN]

So you must have bought the cables from someone else or did you buy 50 metres ???

I think the 2BS rolls are 30m from memory. I bought a roll as I am running my CTEK's behind the back. I also wanted to be able to plug the portable compressor in at the back of the car, it draws about 60amps hence the mega fuses.

Try this on eBay

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 0592575972

Ordered this and received overnight just recently. Half the price of Battery World