Advice please

Discussion in 'Motorhome Chat' started by Red Dragon, Sep 10, 2013.

  1. Red Dragon

    Red Dragon Funster

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    Hi all
    I would like to be able to charge our electric bike batteries whilst on the move?
    My current set-up is
    Rapido with 90watt solar panel,
    2 x Trojan 130amp/h batteries
    Sterling B2B battery charger
    electric bike batteries a/ 36v-10 amp/h. b/ 37v-24 amp/h.
    150watt qausi inverter

    Would I be able to use a 12volt inverter in a standard 12volt plug to power the bike battery chargers?
    Or would I need a bigger inverter? and would it need to be pure sine?

    If I need a bigger inverter would I have to wire directly to the battery bank?

    Thanks in advance:thumb:
     
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  2. cmcardle75

    cmcardle75 Read Only Funster

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    Your bike batteries will take about the same electricity to charge as you have safely available in your battery bank. Your solar panel will not be enough to charge both your battery bank and bike batteries in one day. You will either need hookup, drive when charging, or a lot more solar (you will need about 5 times as much solar capacity). If you charge overnight without hookup, you will also need more battery capacity, or your entire capacity down to 50% will be used purely for bike charging, although Trojans are traction batteries so can be used for deeper discharge at your discretion.

    You don't give enough information about the bike charger to know if the inverter is sufficient. However, if we guess that it charges in 4 hours and there is about 80% efficiency, you're going to need a minimum of 400W, preferably more. Whether it requires pure sine or not depends on its design. Inverters should be connected directly to the battery, or via a thick bus. The max you can get on a cigar lighter is usually 120W.

    Check your B2B and mains charger capacity if intending to use them for charging the bikes. With the above estimate, you'll be drawing 30A from the system for the inverter. Ideally, your B2B will be enough to cover that, plus your 12V fridge requirements plus anything else you've got on, before it even starts to charge your leisure battery.

    If the bank is fully charged before you start, there's no harm in having 20A from a mains charger and 10A from the battery until the bikes are charged. The inverter will then drop its current and the leisure bank will start charging again.
     
  3. hilldweller

    hilldweller Funster Life Member

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    Now what does that mean ?

    When touring but stopped for a few days or when motoring along ?

    No problem when driving, just plug into a suitable inverter. Your 150W might just make it but only just. I have a 300W sinewave.

    If off hookup you are stuffed by that little panel. Your bikes can use more power than it can provide.

    I posted this a few days ago when I did the test for real and ran out of battery power. Now I have only one battery, but that does not matter, after you have charged the bikes once the solar will never catch up.

    Depending on time of year and weather you'd need your roof covered in solar to pull it off and even then you'd fail in a Scottish winter.
     
  4. Red Dragon

    Red Dragon Funster

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    Advice

    Hi Guys
    Thanks for the details,my idea was to charge the bike batteries whilst driving but only one at a time,they both take about 5 hours from absolute flat, but they are normally about 30/50% after use and was just thinking of topping up whilst driving.:thumb:
     
  5. cmcardle75

    cmcardle75 Read Only Funster

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    That should be fine. However, the 150W inverter is too small. You need a larger one connected to the battery. You also need to check the amps on your B2B charger. I would say 20A is the absolute minimum, provided you don't turn the fridge on. Ideally you'd have 40A+ if you want to run the fridge.
     
  6. jonandshell

    jonandshell Funster

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    Whatever you do, you can't draw current from the Trojans whilst they are being charged.
    The b2b charger won't work correctly.
    Your inverter will need to be connected to the starter battery whilst you are driving. How you achieve this is down to you!:BigGrin:
     
  7. hilldweller

    hilldweller Funster Life Member

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    That will work and with the right inverter probably two at once, which is best because I doubt you drive 10 hours a day.
     
  8. hilldweller

    hilldweller Funster Life Member

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    Glad I've not got one :Smile:
     
  9. cmcardle75

    cmcardle75 Read Only Funster

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    Most B2B chargers should cope. The voltage drop should provoke bulk mode.
     
  10. jonandshell

    jonandshell Funster

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    Thats fine if you want to constantly charge your battery at 14.8v and not float it at the correct voltage once charging is complete. The battery will be overcharged and won't last, a waste of a quality battery......
    You will just turn the b2b into an expensive overcharging fixed output unit...
     
  11. Red Dragon

    Red Dragon Funster

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    b2b

    Thanks,
    , cmcardle75,Brian, and jonandshell
    for all your input especailly the comment regarding the b2b(jonandshell):Eeek: no worries though it was a thought regarding charging batteries,there's always plan b,and c. campsites with EHU.........................or generator(shhhhhh!!) :Rofl1::Rofl1:
     
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