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How to setup my dual battery system

Discussion in ''How To' & 'Handy Hints'' started by greengiraffes, Sep 24, 2007.

  1. Dexi

    Dexi New Member

    Messages:
    22
    T3 bus/camper

    Hi

    Thought Id throw in my setup.
    I have 2 aux Batts run by a Piranha battery protector ($350 odd). I started with lead acid deep cycle batteries. One broke a plate and the other has reduced charge after sitting for too long. Ill be replacing them with AGM 100a/hr. I have a good heavy duty 15amp battery charger for topping up at caravan parks. Ideally I want a small solar panel to keep them topped up in the drive. I keep a spare lead acid battery under the passenger seat for accidents (jump starter pack, jumped off a cliff...or was it pushed). I have a marine grade switch/fuse panel in the back to switch all the power and another under the dash for cigarette lighter and stereo. All the batteries have switches to isolate them from the main and each other or dual. I found the marine shops had the most useful stuff. Matched with a 1000 watt inverter. I run a fridge (Relayed and switched) stereo, amp, mobile phone charger and Laptop/dvd/tv/gps/etc. At the moment I use a LED head light for reading at night with rechargeable batts. Changing over the lights to the aux is down the track (Seems a little difficulty). I just keep all the cabin lights turned off. The old door open is fast way to staying where your camped.

    All so I can get reliable power and then drive off in the morning. Next I'm going to add a timer so I don't fall asleep and drain the system with radio (my work around is using the aux separately, one for night one for the morning, through a big marine dual isolation switch).

    Cheers
    Dexi
     
  2. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi Dexi, why are you going for AGM batteries.

    The reason I ask is that contrary to all the hype surrounding AGM batteries, standard flooded wet cell batteries actually stand up to automotive use better than most AGMs do.

    There is a good reason for why AGM batteries fall short when use in vehicles and thats because MOST AGM batteries were never deigned to be use in an automotive situation.

    Anyway, back to my question, why AGMs.

    Cheers
     
  3. Kombi Dad

    Kombi Dad Well-Known Member

    Messages:
    2,408
    Location:
    Bungendore, NSW
    AGM batteries were originally designed for military use and can take a fair battering. Many race cars are now opting for AGMs. I have used mine in my camper for about 3 years in some pretty hard fire trails etc and still work fine. I know quite a few 4WD owners that have run them in severe conditions without an issue. With this kind of history surely they are Ok for a Kombi?
     
  4. drivesafe

    drivesafe Active Member

    Messages:
    108
    As I posted, I emphasised “MOST” and the reason is the MOST AGM are neither military spec or initially intended for automotive use.

    If you have an Optima AGM or similar, then you have a GENUINE automotive AGM battery.

    But most AGM batteries are designed for RAPS and UPS use and to be charged using a current limited constant voltage charger.

    If you don’t discharge the average AGM too low you will probably get a fair sort of operating life out of them.

    On the other hand, if you regularly discharge your AGM battery to a low level and then charge it back up off the alternator as you drive home, your are going to dramatically shorten the battery’s life.

    Contrary to what many people think, most AGM should NEVER be charged with high currents and standard flooded wet cell batteries can actually take much high charge current safely, than can most AGM batteries.
     
  5. Dexi

    Dexi New Member

    Messages:
    22
    Better

    Hi Drivesafe

    I have a standard wet cell battery for starting (when it dose), a spare wet cell under the passenger seat, trickle charging from a small solar (better than a jump pack.)
    Two 120a/hr Trojan deep cycle wet cells in the back for aux stuff. One broke a plate (salesman said it was rare but out of warranty) The other does not hold much of a charge. The van sat stranded in TAS for 4 months. The batteries discharged and where never the same. AGM are not as effected by deep long discharge. I get to use the whole 100 a/hr without damage. In heavy use the battery set gets hammered. AGM last longer in this enviroment if you control the charge enviroment. You need to use a 4 stage charger. (cost more too). When charging overnight on mains wet cells get a bit smelly. I would not use AGM for cranking thats what the spare wet cell is for ( I manualy swap them when needed).

    If you just wanted one extra battery then a deep cycle cranking battery would be best. Just keep it charged and dont let it sit flat (sounds easy).
    If you want fridges, TV, internet, disco LEDs then a nice big set of AGMs is my way to go for reliable power. (A 20 amp solar cell on the roof will set the system off nicely.)

    AGM offers easy maintained, hi amp hour usage at a premium price. Batteries and charges are not cheap.

    Thats my understanding. There are quite a few steel shelled AGM batteries available that are designed for harsh mobile environments. Just don't get suckered into a couple old telstra UPS batts. Pay the money for the real deal and radio national can go all night and day drowning out the refreshing hum of cold beer.
     
  6. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi Dexi, this thread has not been about charging batteries with a 240 vac battery charger but if you do use a battery charger then you should expect to get a good life span from AGM batteries and you only need a two stage charger for AGM batteries.

    The thread is based around using a dual battery set up to charge the auxiliary battery and I’m not suggesting AGM batteries can’t be used in an automotive situation, what I was saying is that good old fashion flooded wet cell batteries are still good value for money and that they will equal the performance of any AGMs on a dollar for dollar basis and that wet cell batteries are less finicky.

    Agm batteries have been around for some time now but it’s insufficient reason to change to an AGM just because one wet cell battery failed. I’ve seen plenty of football shaped AGM batteries and I’ve probably seen as many stuffed wet cell batteries.

    My argument is that there are limitation to the use of AGMs and most of these limitations stem from the way AGMs are charged, not how the are used or stored.

    You posted that you get to use the whole 100 A/H of your AGM, this too is not a correct use of most AGM. Most are not designed to be full discharged but most are designed to be discharged safely to a level below what you can safely discharge a wet cell but here is the problem, MOST AGMs should not be charge with a current that is greater than 20 to 25% of the battery’s total A/H and this is the crucial difference between using a battery charger and a dual battery system.

    The lower you discharge most AGMs before charging them up using a dual battery system, the more likely you are going to shorten their life span. This is not the case with wet cell batteries.

    BTW, you didn't say what brand of AGM you are using?

    Cheers.
     
  7. Dexi

    Dexi New Member

    Messages:
    22
    Charging

    Well said Drivesafe. AGM are not for the faint hearted or cash strapped.They complicate what should be simple. Power in your van. Wet acid are way easier to buy and set up.

    Yes charging is more complicated you cant just hook it straight in. The charge rates are lower. A three or for stage charger with a temperature probe should keep the football battery at bay or at least let you know there is a problem. Its the storage that killed my wet cell batteries as it does in caravans, boats and of things that don't get used enough.

    Im moving on to AGMs because I don't want to spend another $700 odd on trojans (not that there is anything wrong with trojans, They are the deep cycle to buy.) My fault I know. That would be 3 wet cells Ive destroyed in 16 months. We will see if a AGM system will survive. So now Im spending consideraly more and getting way more involved than my first system a dual wet cell set up.

    I don't think I agree with you on the shorter life span thing. Wet cells hate having the guts sucked out them deep cycle only less so.

    The lower you discharge most AGMs before charging them up using a dual battery system, the more likely you are going to shorten their life span. This is not the case with wet cell batteries.


    Ill hunt up some links.

    Cheers
    Dexi
     
  8. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi Dexi, I agree about the unmaintained storage of wet cell batteries is a killer and AGMs will last much longer when left in a fully charge state.

    Again, this thread has to the most part been about dual battery systems and relates to the auxiliary battery(s) being in the vehicle.

    If the vehicle is used fairly regularly then there is little need for any external charging.

    If the vehicle is used infrequently then a maintenance charging regime needs to be implemented regardless of the type of battery you are using.

    Reason being that with a vehicle that is used frequently, after returning from a weekend away, there is a good chance the battery will not be fully charged but will gain a full charge as the vehicle is continually driven in it’s day to day use.

    On the other hand if the vehicle driven home after the trip and stored away, no matter what type of battery you have, you will need to fully charge it before storing it. In this case if you have a two ( or more ) stage charger, you can simply connect it to the battery and leave it there. Again, in this situation there is no advantage to having one type of battery to another.

    If you prefer to fully charge the battery and then disconnect the charger before storing it, then there is an advantage to using an AGM.

    As to charging the battery off the alternator, which is the main theme of this thread, if you have a low charged AGM, when you start your vehicle for the drive home, you will be applying full alternator current to the battery and you will easily exceed most AGM battery’s maximum tolerable charge current by 2 fold or more because most AGM batteries are NOT designed to take full inrush current, but will. This is what shortens there life.

    Because flooded wet cell batteries are virtually self current regulating, you can apply full alternator current and they will not be harmed in any way.

    Cheers
     
  9. ttmck

    ttmck Super Moderator Staff Member

    Messages:
    2,733
    Location:
    Hallett Cove STH AUS
    Tim your a great help to so many people how the hell this escaped a sticky in the how too's god i need my eyes tested !
     
  10. Radar

    Radar New Member

    Messages:
    17
    Location:
    ACT
    ok, being a not very electrically minded lady here, can anyone link or tell me where to start with buying or getting installing the auzillary battery and solar panels? Tips on ACT installers would be terrific too pls. ive been reseraching and reading your tips, but it still looks like alien language to me!
    not sure we're confident managing doing it ourselves....
    thanks!!
    :)
     
  11. Radar

    Radar New Member

    Messages:
    17
    Location:
    ACT
    haha, sorry - so many typos there, im too keen!
    auxillary! (auzillary sounds too close to Godzilla!)

    but poor spelling and rambling posts aside, I'd appreciate your help.
    We want to run a stereo, fridge, laptop charge, phone charge and camera charge and possible a microwave off this power source.

    x0
     
  12. Kombi Dad

    Kombi Dad Well-Known Member

    Messages:
    2,408
    Location:
    Bungendore, NSW
    I had my gear sent down from http://www.fridge-and-solar.net/ They were cheaper than what I could get in Canberra at the time. PM me if you need assistance as I could help connect it all up. I have done my own plus a few 4WD. There's not a lot to it once you know.
     
  13. Kombi Dad

    Kombi Dad Well-Known Member

    Messages:
    2,408
    Location:
    Bungendore, NSW
    Just read your post again. A microwave may be a bit of a challenge but we can speak about that. They consume a huge amount of power which means the battery supply must be large.
     
    Maxa1967 likes this.
  14. Radar

    Radar New Member

    Messages:
    17
    Location:
    ACT
    Cheers Kombi Dad
    Will let you know once we're organised! :)
    And thanks for the link too!
     
  15. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi Radar, the stereo and fridge are easily powered straight off the auxiliary battery and a 300 watt inverter would be sufficient to power the Laptop Charger, Phone Charger or Camera Charger but as Kombi Dad posted, I’d leave the microwave out of the equation.

    The cost of an inverter that would be big enough to power even a small micro wave would probably cost at least twice as much as the microwave itself and would require so much power that your auxiliary battery, if it could handle it with out being damaged, could be flat after as little as 15 minutes.
     
  16. Kombi Dad

    Kombi Dad Well-Known Member

    Messages:
    2,408
    Location:
    Bungendore, NSW
    I will be putting in an inverter, probably 300W, before we go on an extended trip again. The new laptop, Macbook, does not have a 12V power lead that I can find. Up until now with the old Dell, I have used only 12V from a cigarette lighter socket. I also have 12V lighter socket charging leads for all other bits and pieces, e.g. battery charger for AA and AAA batteries, phones, GPS etc.

    If you do use a lighter socket make sure the cable going to it is thick enough. There were some issues that I know of where new vehicles would not power the Waeco fridge owing to too much voltage drop on the thin cable going to the standard socket.
     
  17. Dingostrategy

    Dingostrategy Active Member

    Messages:
    4,322
    Location:
    SW Vic ++
    Hi all, here's a bump.

    I have a 'electro parts Australia BI-80' isolator module. I have had the system inspected by a general autoelectrician, who advised it is correctly wired and quite safe, but that the secondary battery is stuffed.

    My usage profile is that I will store the Kombi for longish periods. Hopefully someone will drive it once in a while but you see the point.

    Reading this thread I take it that I need a wet deep cycle, but I should not expect a long relationship with the battery since it will be affected by the long abandonment. I can charge batteries before taking off, but obviously I will drain them overnight, then charge from alternator. I could, I guess, get a '2 stage charge' and leave, but seems extravagant. Would a trickly solar charger help prolong battery life in this situation?

    I'd appreciate some advice on this - sounds like Trojan is a good idea but since I'll likely stuff any deep cycle battery - perhaps it is sensible not to go for the flash ones? If a trickly solar charger assists during long storage, then maybe this is a reasonable idea?

    Your thoughts appreciated.
     
  18. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi Dingostrategy, first off, trickle charges only work at maintaining a fully charged battery, they WILL NOT charge a battery and will not maintain a low charged battery.

    If you decide to use a Solar trickle charger, you must first fully charge your battery before leaving it to be maintained by the trickle charger.

    It may well work out better to simply use a multi stage battery charger and just leave it connected between vehicle uses.

    Next, to find out if power is getting to your auxiliary battery, start your motor and then start measuring the voltage at different points along the positive cable, starting at you cranking battery and work you way to your auxiliary battery.

    If you get to a point where there is a major difference in voltage levels at the present position you are measuring and the last place you measured then the problem lays somewhere in between.

    If the dual battery controller is in between the tow point then you need to have it looked at.

    If there is some form of cable joiner, then this may need cleaning and the terminals tightened and so on.

    Finding the fault is a process of elimination.
     
  19. Dingostrategy

    Dingostrategy Active Member

    Messages:
    4,322
    Location:
    SW Vic ++
    Thanks indeed Drivesafe, really appreciate your input.

    In fact that was the plan - I have a charger but feel uncomfortable leaving it on permanently. I don't know why exactly, but my intention is to have solar maintaining the battery only. I appreciate 5W won't charge a big battery.

    I had the system checked out by an autoelectrician - by his own admission didn't know much about the particular module. But he advised that the current was going to the appropriate places in the appropriate amounts. I think the deep cycle was 2-3 years old and it was left in a low-charge state just now for nearly a year. Point is, I think it was stuffed - just not charging however well the system was feeding it. I put it on a charger and it really didn't make a lot of difference.

    I replaced it with a 65A wetcell 'century' brand, despite the cynicism about brands like that. It was reasonably priced. I would loved to have put in a much larger battery but there really is very little room in the LHS battery area.

    I would proposed to anyone considering installing a dual battery system to consider that when installing: it is probably a little tricky but swapping the crank battery to the left would leave a much large space (for probably 150A) on the RHS. I am sure it is no simply thing to run a loom from one side of the engine bay to the other but I offer this suggestion for your comment or for the notion to be scuttled entirely as amateur folly.

    Cheers.
     
  20. drivesafe

    drivesafe Active Member

    Messages:
    108
    Hi again Dingostrategy, a much easier and cheaper alternative would be to fit one of my SC40-BK kits.

    My SC40 Dual Battery Controller allows the auxiliary battery to share it’s power requirements with the cranking battery but isolates the cranking battery while it still has heaps of power to be able to start the vehicles.

    This set up effectively adds 50% more power to your auxiliary battery without any additional cost.
     

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