2 x 200amp hr bat. set up on homebuild

Discussion in 'Motorhome Chat' started by PeterCarole29, Aug 27, 2013.

  1. PeterCarole29

    PeterCarole29 Read Only Funster

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    I didnt know where to put this thread homebuilds or motorhome chat .i even thought perhaps of tagging it onto the last leisure battery thread.So please correct me if needed.I am not very confident with electrics or rather i dont know whats available to fit and use as gadgets
    I have fitted but not connected 2 of the attatched batteries.Last year i fitted a relay under the bonnet to charge a leisure battery and think it said a max of 140amp hr.
    Has anyone got an idea of a perfect set up.
    I useually end up doing things twice and hope to start avoiding that this time .Thanks in advance
     

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  2. pappajohn

    pappajohn Funster Life Member

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    dificult to know where to start without knowing how you wired the vans 12v electrics.

    do you need advise on connecting the batteries together or connecting to the actual 12v electric circuits ?
     
  3. Geo

    Geo Trader - Funster

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    Also what do you want the batteries to do for you:RollEyes:
    Sounds obvious but trust me it aint:Sad:
     
  4. Gromett

    Gromett Funster

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    I doubt it said 140 Amp/Hour. I bet it said 140 Amps if you look at it?

    The relay will pass X amount of current whether that goes into a 100AH battery or a 500AH battery bank is irrelevant I believe.

    They do sometime give a recommended range so that they are matched up.

    No point putting a 10Amp relay on a 500Amp battery as it would take forever to charge. The opposite is also true. They are however just guidelines.

    For example I have 500Ah battery bank but only a 25Amp charge because that was all I could afford. It works fine but takes a long time to charge. I will upgrade to a 50Amp charger when I have some spare cash.
     
  5. PeterCarole29

    PeterCarole29 Read Only Funster

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    Yes you are right 140 amp and i understand about it now thanks
     
  6. pappajohn

    pappajohn Funster Life Member

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    I doubt your alternator will produce 140amps, certainly wont when your engine battery is fully charged, so that relay will be fine.

    most 'shop bought' split charge relay's are rated at around 30 amps.
     
  7. PeterCarole29

    PeterCarole29 Read Only Funster

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    Also Thanks to Papajohn.
    We intend to wild camp in portigal and southern france january and Febuary .not have a generater.A solar panel would be good across the width and between roof vents.An inverter for a hair drier.Its an essential as i wont get fed otherwise.Unsure what size i would need as a minimum.All the other stuff normal except i have a 24v eberspacher which will run through an 12-24volt inverter(i was thinking of changeing this to 12v but its now fitted and is a good one so am finding it hard to justify removing it for a 12v one)
     
  8. pappajohn

    pappajohn Funster Life Member

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    buy the biggest solar panel the roof, and your pocket, can take.

    you can never have too much power.

    keep the hairdrier as low wattage as possible while still useable....inverters kill batteries.
    a 1200 watt inverter running a 1200watt drier will draw 100amps per hour from your battery.(ies)
     
  9. cmcardle75

    cmcardle75 Read Only Funster

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    TBH, with 400Ah of batteries, you'll need to replace the relay with a battery to battery charger to get any meaningful recharge when driving. You will also need a pretty heavy duty mains charger to take advantage and as many solar panels as will fit. The end result will be a lot of available electricity.
     
  10. TheBig1

    TheBig1 Funster Life Member

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    what you seem to be missing is that the alternator on your vehicle will produce a high current charge to top up the engine battery, this then drops off as it becomes fully charged. any supplemental load like split charge is drawn from the engine battery at a much slower rate

    fitting a battery to battery charger in effect fools the alternator into providing a higher current till the leisure battery is charged at a faster rate. it is limited by a number of issues though including the thickness of the cables between the batteries. also regularly "fast" charging a leisure battery will shorten its working life. these batteries are only warranted for about 300 charges maximum, so could end up being very expensive if replaced regularly
     
  11. TheDogMan

    TheDogMan Funster

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    I have 2 x 225amp batteries and they are just connected together and with 240watts of solar they stay full as long as I get at least a lightish day, I did learn a lesson though, the invertor makes all the sockets live when switched over so I have to ensure the tec tower is switched from auto to gas otherwise it auto switches the fridge frezzer to mains from the invertor:Doh:
     
  12. TheBig1

    TheBig1 Funster Life Member

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    be very careful if your inverter is wired direct to the sockets in your van. if you forget and go to plug in the ehu, the inlet port will be live with exposed connectors.
    plus if any high load items like the kettle and heater or hot water are left switched on, it will overload your inverter

    it is far safer to power a separate socket from an inverter:thumb:
     
  13. Terry

    Terry Funster

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    Pray tell me how your alternator knows the difference between engine battery (full) and leisure battery through an open circuit ?

    Terry
     
  14. cmcardle75

    cmcardle75 Read Only Funster

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    Typically, the path between the engine battery and the leisure battery is via a quite high resistance path via thin cables and a relay. This means that the alternator is only really sensing the voltage across the engine battery.

    Some alternators are "smart" and have charging electronics built in. These will charge at around 14.4V and then drop to about 13.4V float charge when they detect the battery is full. These are the ones that can get fooled, as the 13.4V, just won't be enough to charge the leisure batteries through a high resistance path in anything other than geological time.

    Older alternators will only produce about 13.8V anyway, as a compromise between actually charging the battery and avoiding overcharge. These charge slowly at the best of times, even for the engine battery, let alone with the voltage drop to the leisure battery.

    Hence, a split charge relay will only charge your leisure battery very slowly. I still put such a system on mine. This is because I get quite enough power from my solar system so I don't rely on it for charging and because its main reason is actually to power the 12V fridge when driving. It was also a lot cheaper.

    If you actually want to charge your leisure batteries when driving as your main source of habitation power when stopped, you will need a proper B2B charger. The actual charging rate will likely be many times faster than a split charge system.
     
  15. PeterCarole29

    PeterCarole29 Read Only Funster

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    I have been looking at the batteries most of the morning and pondering and come to the conclusion its not posible to ask all the different questions that come to mind .
    Do we have anyone going to Lincoln that can show me what to connect to what please.
    For the time being i have fitted one battery each side of the van.I have connected the engine relay to one.the same battery i have earthed it to the chasis through a breakerblock.I have also wired it to the 12v of the van through an isolater.
     
  16. Terry

    Terry Funster

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    While I can agree to a point provided the correct thickness cable for the length of the run is used then the alternator should/will not sence any difference (assuming a newer van-older van won't anyway) and now after reading OP above there is nothing to stop him from conecting another relay (or a twin relay) to charge the batteries:Smile:
    Personally I have fitted a twin feeding LB/Fridge with decent wiring so get no problems charging :thumb:I also fitted a good 22 amp 3 stage charger but if I had 400 amp hrs LB I would choose a bigger 40 / 50amp charger :Wink:
    Peter can you fit both LBs side by side? If you can it would be better than sticking an extra relay but if not the extra relay is the way to go :thumb:Also with 400 amp hrs of batteries you won't need solar unless you are off grid for more thana week or two :BigGrin:
    Scotjimland used to have a very good link for cable thickness/lengths required someone may well post the link for you :Wink:
    Terry
     
  17. PeterCarole29

    PeterCarole29 Read Only Funster

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    Thankyou Terry for your reply and sorry i havent been on for a few days.The batteries will have to go one each side because of the distribution of weight as they are so heavey i am guessing at 50kg each.I will wire them together if its best with cable that must be the diameter of my fingure 15mm.So far i have bought a 1600w modified sine wave inverter/charger 80amp made by stirling. the plan is to also get 12v alternater to battery charger .I will get one solar panel hopefully 120w on the roof as well.
    I seriously lack the technical knowledge to know the best way to connect it all up or if i should have any other other worthwhile gagdets
     
  18. Terry

    Terry Funster

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    Why not wait and see IF you need solar? Provided you get a decent 40 amp hr ish mains charger and get on hook up overnight once a week ish I would think 400 amps of battery power will last easily. I only have 1 x 110 amphr battery and last 3 to 4 days off grid easily but it all depends on how you use the van and power available.
    It's very rare for us to simply park up and not move, be that to the shop restaurant etc, so I get a little charge into the battery from that.I find that is more than enough for our needs without overkill :Wink:
    You can of course spend lots of cash on things you may need or never need :BigGrin: just to be sure :Smile:Indeed I have had a spare LB in my garage for almost 4 yrs that simply because I have never needed it I have never got around to fitting it :Eeek: It is only a case of side by side fitting :BigGrin: chances are it will be kna---ed before I get around to fitting :BigGrin: You can always add to what you need rather than want :BigGrin:
    Terry
     
  19. mitzimad

    mitzimad Funster

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    so your saying an incorrectly fitted split charge will not charge the batteries in that case neither will an incorrectly fitted battery to battery charger
     
  20. mitzimad

    mitzimad Funster

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    my self build has 225amps of traction batteries and 180 watts of solar and a correctly sized split charge system weve not had a hook up all this year and never a problem with electrics think the longest staitionary was 5 days so between solar and alternater weve been fine
     
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