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Technical => Campers => Topic started by: snow on August 01, 2008, 11:29:44 PM

Title: Dual Battery
Post by: snow on August 01, 2008, 11:29:44 PM
After help in doing a dual battery setup in a camper/motorhome, have plenty of room so that not an issue, 1 battery as a starter and the other as a 12v lights and stuff, an diragrams or pics would be great as well, I know that both batterys are to be of equal size, any input would be much appreicated

cheers snow
Title: Re: Dual Battery
Post by: ShaneJ on August 01, 2008, 11:41:50 PM
Where abouts are you located?

Your starter and aux battery dont have to be of equal size. Get a high CCA battery thats enough to start the engine and get the biggest Ah Aux battery that you can find.

Wire them up like the diagram below and you're laughing.
Title: Re: Dual Battery
Post by: ben on August 02, 2008, 06:03:12 AM
thats so simple shane.. thats flippen great!!! now tell us how bigger relay should we be using? i know its only on the ground but still??

and so that will mean everything will run off the second battery when ignition is turned off until you flick over ignition which is perfect, unless you flatten the aux battery like dead dead wont the aux battery drain the starting battery?? or should it stil kick it over?? or is it just the same as like having a set of headlights on while trying to start. like the headlights certainly would drain the batery but you can still start the vechile with them on..

cheers
ben
Title: Re: Dual Battery
Post by: ShaneJ on August 02, 2008, 08:42:53 AM
You'll be wanting the biggest relay you can find. I normally use 180A jobs but that's just what I have access to.

If you dead flatten the aux battery it will draw a lot of current from the main battery once you turn on the ignition, but the engine will start as long as you do it within a few minutes of having the ignition on.
Title: Re: Dual Battery
Post by: snow on August 03, 2008, 12:22:28 AM
Thanks for that ShaneJ, can't we incorporate a switch so that when you stop you can turn the switch to aux and say flatten it and then when starting turn the switch over to the main starting battery and once the motor is going charge both, I use to skipper my uncles reef boat up north years ago remember once anchored up at night i used to open up a section of the floor where the batterys were and turn a switch so it would not drain any power from the main starting battery and other was used for lights and what not and turn it back to main battery to start.

I'am now liiving in Brisbane

cheers snow
Title: Re: Dual Battery
Post by: ShaneJ on August 03, 2008, 01:31:12 PM
You could use a switch like you just explained, but the circuit I posted will achieve the exact same thing without needing to remember to change the switch.

I'm in Brisbane on the north side if you ever need any help with your wiring.
Title: Re: Dual Battery
Post by: JOE RYAN on August 03, 2008, 03:38:22 PM
Shane J and any other Brisbane members

I am at Redcliffe contact on janddryan1@optusnet.com.au with phone number so we can meet up organise a get together with other Brisbane members
Title: Re: Dual Battery
Post by: ShaneJ on August 03, 2008, 03:46:24 PM
My Bedford is at my mates workshop at Redcliffe at the moment getting some body work done. I'll give you a shout once I get it back.
Title: Re: Dual Battery
Post by: Joel Oswald on August 03, 2008, 03:58:05 PM
I just went through the exact same thing regarding the dual batteries. I used a thing called a VSR. Voltage Sensitive Relay, made for this purpose. Does the same as the boat switch mentioned below i.e. ALL, 1, 2 etc but it's all done automatic. Run your starter battery into the VSR plus your house/second battery + wire, earth & you're away...
Title: Re: Dual Battery
Post by: shaginwagin on August 03, 2008, 07:57:53 PM
Shane J and any other Brisbane members

I am at Redcliffe contact on janddryan1@optusnet.com.au with phone number so we can meet up organise a get together with other Brisbane members

Kath and I live in Deception Bay, next door to Redcliffe, would love to meet up with anyone who is interested in Beddies.  We will be going through the rebuild after the Van Nats at Easter, and will be looking for all types of help with it.
Title: Re: Dual Battery
Post by: snow on August 03, 2008, 11:46:28 PM
Ok. if I had a brain, ShaneJ i didn't notice the in your diagram that the ignition was off and the relay was open so yea the main battery wouldn't be touch, so i'am guessing to get the size of a relay go see an auto electrain, I also like Joel's way with the VSR relay as well, thanks guys 2 good options and a diagram just what i was after i'll let you know down the track how it turns out

Didn't know there was that many from brizzy here maybe it's the new board huh i was beginning to think them sandgropers had pinch everbody

cheers snow
Title: Re: Dual Battery
Post by: ShaneJ on August 04, 2008, 08:11:53 AM
Once we get some stickers available and advertise the site a bit more hopefully we'll get some more Bedford members.

Comet batteries at Geebung can help you out with a good relay. They keep them in stock there.
Title: Re: Dual Battery
Post by: alien8 on August 04, 2008, 06:58:51 PM
My Bedford is at my mates workshop at Redcliffe at the moment getting some body work done. I'll give you a shout once I get it back.

Hi Shane, your bedford wouldn't happen to be at KCF Rallysport and being worked on by Keith would it.
Title: Re: Dual Battery
Post by: ShaneJ on August 04, 2008, 07:10:57 PM
That's the place, but Keith if off work for a bit.

You know him?
Title: Re: Dual Battery
Post by: snow on August 04, 2008, 11:05:04 PM
thanks for the help ShaneJ, i'am on the western side of brissy 1st i'll try on this side other wise over to your side

 cheers snow
Title: Re: Dual Battery
Post by: Clance on August 05, 2008, 07:23:05 AM
Basically you should be thinking about how big a battery can you fit, and less about how small and cheap a battery you can get away with, the larger the battery the less percentage wise you will be draining it, and the longer it will last both in power usage and battery life, with the extra advantage of more capacity when needed.
Hot Tip ÖBatteries love being fully charged, they donít like being discharged at all, they like it when you only take them down to 50% of their capacity and then top them back up soon after, they will lose capacity and die quickly when left discharged for long lengths of time.
The Battery Isolator.
The battery isolator is a device that allows the cars alternator to recharge the auxiliary battery while protecting the cars starting battery from discharging, if these batteries are simply linked together you run the very real risk of draining them both to a level that you can not start the engine, and there are many other reasons why you should not do it this way.
So hence we have the battery isolator, there are many different methods used to isolate the batteries, most use some form of solenoid, this is an electronic switch that can handle large (charging) currents, much more than standard switches can, and they are operated by applying a small amount of power to them, this is turn actuates a solenoid that links the batteries together so that large currents and be passed between the batteries.
There are many ways to operate these battery isolators, some much better that others.
The cheapest way is that you manually turn them on and off, I call these idiot switches, because sooner or later some idiot (and Iíve been there) will forget to turn the switch on (no charge goes into the aux battery) or off at the right time (and then the starting battery gets drained as well).
Another way of doing it is to have the solenoid turn on as soon as you start the engine up, and turn off when you shut down the engine, this has been the cheap way of doing it for many years, but itís far from ideal.
I believe the best way for most situations is to use a VSR (voltage sensitive relay) activated solenoid, and the one I like the best and use is one of the most inexpensive ones, it does the job very well, and as good as, and sometimes better than many of the very expensive ones too.
The Redarc Smart Start battery isolator and how it works.
 
When you start your engine the Redarc works by first letting your starter battery recover itís charge, it lets it achieve 13.2 volts, at this point that battery has about as much charge in it as it's going to get, once the Redarc sees this 13.2 volts it closes the contacts on the solenoid, this links both batteries together for charging purposes.
The next thing the Redarc is looking for is 12.5 volts, in other words you have shut down your engine and started to draw power from the batteries, so very quickly the voltage across both batteries will fall to 12.5 volts, as soon as the Redarc sees this voltage it will open the solenoid contacts and isolate the batteries, leaving your starting battery for starting and your auxiliary battery for auxiliarying ;-)
The Redarc Smart Start battery isolator is rated at 100Amps constant duty with a surge capacity of 400Amps, it has silver contacts unlike some of the cheaper ones that have copper (silver is much better), the Redarc also has spike protection so it wonít upset the delicate electronics on newer vehicles.
Title: Re: Dual Battery
Post by: Clance on August 05, 2008, 07:33:32 AM
This is the Redarc VSR Solenoid that I use in my motorhome, I've been using it for thre years now and have not had a flat battery yet. The wiring is basically the same as Shanes relay method it's just that these are voltage sensitive.

(http://imaginocean.bigpondhosting.com/thumbs/redarc-10-sbi12.jpg)
Title: Re: Dual Battery
Post by: ShaneJ on August 05, 2008, 04:56:21 PM
The problem with those redarc jobs is that the transistor in the voltage sensing unit starts to get lazy after a while. With out enough current the main relay doesn't close hard enough to make good contact for high current to pass through.
I had one fitted in my 4x4 up until a few weeks ago to charge a third battery in the back and I had this very fault with it.
Title: Re: Dual Battery
Post by: ben on August 05, 2008, 06:57:02 PM
far out i dont know whih way to go now!!!! relay or Voltage sensor..

maybe ill flip a coin!!!
ben
Title: Re: Dual Battery
Post by: ShaneJ on August 05, 2008, 07:07:54 PM
A plain ol relay is cheaper ;)
Title: Re: Dual Battery
Post by: ben on August 05, 2008, 07:12:20 PM
ok cheap always wins haha so ive made my decision..

now where would i go to get a mother of a relay like your talkinga bout shane?
Title: Re: Dual Battery
Post by: ShaneJ on August 05, 2008, 07:14:53 PM
Most auto electricians will have them in stock. Failing that, ARB or TJM should be able to help you out.
Title: Re: Dual Battery
Post by: ben on August 05, 2008, 07:16:10 PM
and roughly how much money should i be bringing with me also? cheers for that shane

ben
Title: Re: Dual Battery
Post by: ShaneJ on August 05, 2008, 07:24:41 PM
100Amp solenoid is about $25 but if you can, get one a little bit bigger. Although that's 100Amps continuous, so should handle 450Amps surge. See the following link:
http://cgi.ebay.com.au/DUAL-BATTERY-ISOLATOR-SOLENOID-EASY-TO-DIY-100AMP-ABR_W0QQitemZ230275872648QQihZ013QQcategoryZ30862QQcmdZViewItem

Try contacting that guy and see if he can supply a higher current job.

Here is one of the redarc jobs for $95 from the same seller:

http://cgi.ebay.com.au/REDARC-DUAL-BATTERY-SMART-SOLENOID-SBi12-FREE-PUSH_W0QQitemZ310070968556QQihZ021QQcategoryZ30862QQcmdZViewItemQQ_trksidZp1742.m153.l1262
Title: Re: Dual Battery
Post by: snow on August 06, 2008, 12:57:27 AM
Ok also with the aux battery is it worth while looking at getting a deep cycle one, at the moment my starter battery is a boat battery, also with that solenoid how high is high with the amps

Ben cheap is not always the best way to go believe me, if you want to do it right do it only once thats why forums like this help us

Clance you got any pics of your motorhome?

cheers snow
Title: Re: Dual Battery
Post by: Clance on August 06, 2008, 07:54:12 AM
Hi Snow, there are some in the gallery section of my old one and the current one. Cheers
Title: Re: Dual Battery
Post by: ShaneJ on August 06, 2008, 07:59:20 AM
Ok also with the aux battery is it worth while looking at getting a deep cycle one, at the moment my starter battery is a boat battery, also with that solenoid how high is high with the amps

Ben cheap is not always the best way to go believe me, if you want to do it right do it only once thats why forums like this help us

Clance you got any pics of your motorhome?

cheers snow

If you want to start running the aux battery flat, you will need a deep cycle. Running your high CCA starting battery flat will kill it real quick.

Re the solenoid, a 100Amp job would be fine as these will handle 400Amps surge which is no more than the starter on a 6 will use. If you have a v8 you should be looking at a 150-200Amp solenoid.
Title: Re: Dual Battery
Post by: snow on August 06, 2008, 11:26:01 PM
So ShaneJ are you saying a deep cycle battery is the way to go for an aux battery?

Hey Clance i haven't been in the gallery section properly yet alot of reading of posts but go an have apeek a boo now

Cheers snow
Title: Re: Dual Battery
Post by: ShaneJ on August 07, 2008, 08:00:35 AM
A deep cycle battery is the only way to go for an aux battery.
Title: Re: Dual Battery
Post by: snow on August 08, 2008, 12:06:30 AM
Ok thanks for that and all the others input got a good idea in which way Iam going to set it up, just curious about what that flash button does so going find i sup

cheers snow
Title: Re: Dual Battery
Post by: Auda on August 08, 2008, 05:49:17 AM
Deep cycle batteries are the way to go.
  However, we have a house bus and have used an N150, I think, for the house lights, stereo, computers etc. It has had a hard life being run down to 11 volts fairly often, left to go flat over winter and charged at over 60 amps at times. Its a standard truck battery, has lasted 4 years and cost a bit less than a third of the price of a deep cycle battery. Would a deepcycle one last 10 years ? I dont think so Tim.
  Charging wise the bus has 2 alternators the systems are seperate except that I have a low current switch inside to swap to the bus battery if the lights get to low and a heavy wire in the battery box to connect them for emergency starting.
  I also so have a bettery charger I made from a microwave transformer it will put out 20+ amps at 13 volts and over 100 amps at 10-11 volts good for starting vans with flat batteries.
Title: Re: Dual Battery
Post by: ben on August 08, 2008, 08:55:02 AM
cool can you give us more info on your home made battery charger?? that sounds awesome..

maybe a digram or something.. cheers
ben
Title: Re: Dual Battery
Post by: Auda on August 08, 2008, 09:38:42 AM
I have been going to make another one so I'll do that and take some photos.
Is there a way to host photos here or do you have to have them hosted some were else ? Thats a hassel and not reliable.

Auda
Title: Re: Dual Battery
Post by: ShaneJ on August 08, 2008, 10:10:11 AM
You can attach pictures directly to your posts or you can host them in your photo gallery.
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