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Needing help with power requirements

Discussion in 'Power Electronics' started by davelectronic, Dec 24, 2019.

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  1. davelectronic

    davelectronic

    1,087
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    Dec 13, 2010
    Merry Christmas to everyone.
    I'm looking for some advice on charging up a mobilty scooter. I live in a 14 floor tower block, and on the 13th floor. Normally i use the elevator and charge my scooter indoors. But as of two days ago, the water tank at the top of the building ruptured. Hundreds of litres of water got in to the elevator shafts and took out both, so they won't be back in service for a few weeks

    I've been given a lock up to stor the scooter, but sadly there's no power points in the lock up. I was hoping to use a car battery and inverter to power the scooter charger. The scooter has two 50Ah batteries in series, so the scooter system is 24 Volts. If a car battery and inverter is a viable option, I'm unsure of what capacity car battery that i would need. The scooter charger is an input of 120/230 Volts auto detection, the output is 6Amps / 5Amps at 24 volts. I'm not 100% sure on what power inverter to go for.

    And also would i need to recharge the car battery after every charge of the scooter via an inverter.
    This is a bit of a crisis, as i live with my Son, as he's a youngster its unreasonable for me to expect him to run here there and every where. It would be a huge help if someone could suggest a car battery / inverter combination that would be suitable for off the grid charging.
    Thanks for reading, i could really use the help with this.
    Thanks again.
     
  2. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    What might be helpful in the image below. Going on the math, and mine is not fantastic. I've looked at the highest power rating for the mobility scooter charger, it says 2.8 Amps / 1.5 Amps I'm guessing one is for 230 Volts and the other for 115 Volts. So 230 Volts × 2.8 Amps is 644 Watts, so with some headroom, I've found a reasonable 1000 Watt continuous power inverter, and a 12 Volt car battery rated at 110 Ah. Would that combination be capable of recharging the pair of 2 × 50Ah mobility scooter batteries ? I've found a suitable car battery charger to complete this off the grid charging system.
    Thanks again for any help.
     

    Attached Files:

  3. Hunter64

    Hunter64

    27
    10
    Nov 20, 2018
  4. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    I've been searching local to me area, and found a 12 Volt 115Ah leisure battery deep cycle. That would be good news, as i might be able to come down on the inverter maximum power.
    Its the battery and inverter combination I'm unsure on, i don't know the exact charging rates. It the mobility scooter charger switches to some kind of pulsed charging when its nearing full charge.
     
  5. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    It's become very real, like the current drawn from the battery is not doable at the power from the mobility scooter I need. Something like 30 Amps from an inverter on the 12 Volt DC side. 24 Volts looks marginally better, but even that seems high current draw at just over 15 Amps. And I didn't realise the inverter should only be powered for about 1 hour or so. 24 Volt batteries look hard to source, at least in my searches.

    Does anyone have any idea what would be doable off the grid, I only need short journeys until the elevator is repaired. Wow I had no idea that much current was being drawn from the 12 Volt DC side of the inverter.
    Thoughts anyone.
     
  6. Bluejets

    Bluejets

    3,764
    781
    Oct 5, 2014
    50Ah x 2 would require 50Ah x 2 plus any losses.
    Back to the energy in is equal to the energy out plus any losses equation.
     
  7. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Thanks for your reply, I've got to find a solution. I have a second mobility scooter with 2 x 36Ah batteries, they are fairly easy to remove as that scooter in designed to take down in three parts plus batteries. So I would ideally like to use the larger scooter, it has a 35 mile range (less in reality) but much quicker as it's a road scooter. The smaller scooter is pavement use only, but still has a 20 mile range, again less in reality.
    At the moment I'm looking at £130 for two smart chargers, remove the smaller scooters 36Ah batteries and charge independently. I can't find a 24 Volt charger for stand alone AGM cells. And I'm unsure on equal charging of both batteries.

    And my first idea was to power the mobility scooter battery charger via a leasure battery and an inverter, but on further searches realised the DC input current to the inverter would be around 30 Amps. And that is for the scooters AC primary side input of 1.5 Amps of that charger. The image I posted earlier. Is it even viable to use an inverter for powering a mobility scooter charger ? And additionally I've noted the inverter might only be capable of use of up to 1 hour maximum before needing a break, to avoid over heating. It's very cold in the UK at the moment and the scooter is in a lock up I've been given until the elevator in the tower block is repaired. I know the inverter route is far more expensive to implement than the smaller scooter 36Ah simple hook up and charge.

    I know a bit of the maths involved, but these inverters seem to have many variables in terms of power delivery and input to output requirements.
    I had thought an inverter of 12 Volts 1000 watts, and a leasure battery of 115Ah 12 Volts. Knowing the leasure battery needs recharging after every scooter battery charge.
    I can see the higher wattage inverters 2000 watt upwards can handle better for longer. I'm uncertain if a modified sine wave inverter would power the mobility scooter charger, or I would need a pure sine wave inverter instead.
    And there quite a bit more expensive. I have a theoretical spend limit, but the elevator is well taped up with out of order tape all over its doors. And the lock up was loaned to me because the mobility scooter was a fire hazard in the communal lobby ground floor. But when the lifts where damaged by water ingress from the top of the building, I had no where to put the mobility scooter.
    Thankful for the use of the lock up, as at least it won't be vandalised now.
     
  8. Bluejets

    Bluejets

    3,764
    781
    Oct 5, 2014
    I'd be looking to run out an extension lead from somewhere close.
    All this batteries and inverters etc. etc. seem a lot of bother and cost for a couple of weeks.
     
  9. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Yes the inverter option seems difficult and expensive. Yesterday we had one elevator working, not are elevator though. Its odds and evens numbers, I'm on the evens lift. But even that offered some hope, as with my Sons help i could get the smaller mobility scooter batteries and charge them indoors. As of this morning the odds lift has broken down again. My Daughter had a climb of 12 floors to get here this morning.
    Merry Christmas to you all where ever you are, and have a great day out there.
     
  10. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Sorry forget, no there is nowhere to run an extension lead from. I had even considered a cheap and chearful generator, but i can't leave it unattended. If i did go the inverter route, would a 12 Volt 115Ah leasure battery, and 1000 to say 1500 watt inverter be doable ? My concern is the high current the inverter is drawing from the battery. Around 30 Amps i believe, and could run theoretically for 3.4 hours. But the maximum inverter run time before rest, and not dropping the battery below its terminal voltage could be a problem.
     
  11. davelectronic

    davelectronic

    1,087
    12
    Dec 13, 2010
    Thank you for all the replys. I'm using a 12 Volt battery 115Ah leasure battery and 1000 watt inverter. The inverter is probably bigger than i need, i just wanted a good margin of headroom for the task. It appears to be working, although I've limited the charging time to 3 hours. This is so i don't completely flattern the battery powering the inverter. I figure two charges should fully charge the scooter batteries, as i used the scooter and dropped a lot of led's on the scooters power meter. Short few journeys, and it should only need minimal top up charges.
    Thanks for the help.
    Happy new year to you all.
     
  12. WHONOES

    WHONOES

    774
    168
    May 20, 2017
    Could you not use a small generator and a conventional battery charger to do the job?
     
    duke37 likes this.
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