Charging Electric Bike Batteries When Not On Electric Hook Up

Discussion in 'Bikes and eBikes' started by Phil J., Jul 7, 2015.

  1. Phil J.

    Phil J. Funster

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    Hi,
    I have searched for some help but can't really find the answer I need:

    I have the following:

    2 x 36 volt 10ah electric bikes
    2 x chargers. Input - 240v ~ 1.8A max, Output 42v - 2.0A

    The motorhome has:
    2 x 85ah leisure batteries (new)
    1 x 100w solar panel
    1 x 1000w quasi sine wave inverter

    My problem:
    I tried charging both batteries together on the inverter and the battery low warning came on before both were fully charged but it was a bright but not sunny day. Overnight, as there had been little sun during the day, the batteries were still very low but everything worked fine during the day. As we were again off EHU for a few more days we decided to play safe and have a night on EHU and get fully recharged. All fine again but didn't risk recharging the batteries for the remainder of our trip on the inverter and managed to get the bike batteries recharged on mains at the site wardens caravan (the site had no EHUs for other motorhomes or caravans).
    As a by the way, my solar set up keeps my motorhome going more or less indefinately when just using the normal stuff - satellite tv for maybe an hour or so a day, low consumption led lights, water pump, etc.

    Should I have charged 1 bike battery at a time on the inverter during the day?
    Is my set up sufficient to charge 1 or 2 bike batteries?
    Does anyone else have similar who can share their experience?

    Thanks in advance for any help.
     
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  2. hilldweller

    hilldweller Funster Life Member

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    36V * 10Ah = 360Wh * 2 = 720Wh.
    12V * 85Ah = 1020Wh * 2 = 2040Wh

    You normally use only 50% of a leisure battery = 1020Wh.

    So your two bike batteries, with all the electric losses are as big as your leisure battery. And that assumes you have fully charged leisure and no other load.

    OR.... You have 5litres of fuel and a 6 litre tank to fill.

    If it's any consolation we are in the same boat.
     
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  3. Don Quixote

    Don Quixote Funster

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    Well firstly your inverter will draw 83amps at full power. Secondly you have 2 x 85amp (total 170amps ) batteries, but really you only have 85amps to play with as once you discharge them past 50% you are starting to destroy them. You say/have "2 x chargers. Input - 240v ~ 1.8A max, Output 42v - 2.0A"= total 4amps per hour. Why do you have a 1000 watt inverter when all you really need is a 500watt one. More than enough to charge the bike batteries, but will draw 1/2 the amperage or less.
    The solar panel should do the job, but you only need 2/3 days of no FULL sun and your batteries will start to go past the 50% charge mark and therefore start to die............
    Remember that you are already drawing 4/5amps per hour with your TV, Sat etc....... then plus another 4 amps for recharging bike batteries. Start watching TV at 5pm until 10pm and charge batteries will draw total = 45amps = two days later batteries are below 50%.
    Going onto EHU for 1 x night will NOT fully charge your batteries................
    Hope that helps.
     
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  4. Don Quixote

    Don Quixote Funster

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    GOOD POST.
     
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  5. John Laidler

    John Laidler Funster

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    I see Lidls are selling a generator for £149.00 at the moment....


    But don't worry about your inverter drawing twice as much current as a 500W one, both will, within a gnats, draw the same current for the same load.
     
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  6. Judge Mental

    Judge Mental Funster Deceased RIP

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    is it one of the ever so noisy ones?...really like those!:giggle:

    this where Bosch powered bikes come into there own (yet again) a full charge from empty only takes 2.5 hrs and a partial charge a lot less....
     
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  7. DavidG58

    DavidG58 Funster

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    we charge anything requiring more than a couple of A's while on the move, the leisure batteries are being well topped up by the alternator, we then have a plug in power supply / charger for the laptops and bike charger plugged in to the habitation and cab 12V sockets (y)

    if not moving on, not sure what is best, run your engine while charging maybe? or move more often :)
     
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  8. Phil J.

    Phil J. Funster

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    Thanks for the replies guys.
    If I am understanding Brian's calculations and the other comments, with my set up I should be able to charge one battery at a time? I also understand it is better to top the bike batteries up every time we use them as this will take less time to charge and, therefore, less drain in one go from the leisure batteries. The other thing is - with the extra(?) power of the alternator when on the move with there be sufficient charge going in to charge both batteries at the same time?
    Sorry for all the questions but I want to make sure I'm not overdoing the draw on the leisure batteries which may cause premature failure.
    Thanks again for all your help - really appreciate it.
     
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  9. Red Dragon

    Red Dragon Funster

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    Hi Phil J,we had a similar problem but 3 e-bikes,260amp/hr of L/battery,90watt solar panel and a 500watt pure sine inverter.
    The solution for me was fit a B2B which keeps my leisures nicely topped-up,and charge 1 battery at a time when travelling as then there is no drain on the L/B's,easy enough to check them if fully charged then swap to the next one.
    Keep the e-bike batteries in the front of the van and the co-pilot does the monitoring!!(y)
     
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  10. injebreck99

    injebreck99 Funster

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    We plug our inverter in whist driving and charge them like that with a top up by solar panel if required, only one battery at a time though.
     
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  11. tonyidle

    tonyidle Funster

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    A smaller inverter will save a small amount but it won't save anywhere near "1/2 the amperage". All inverters draw a very small current when not in use and when they are in use this is added to whatever current is being drawn when loaded. This small current is slightly higher for a larger inverter but it's still small.
     
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  12. Don Quixote

    Don Quixote Funster

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    I fully aware of that fact, however my point was why have 1000watts to charge the bike batteries when a 500watt will do the same job. A saving on batteries is a saving no matter how small..........
     
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  13. Neilfg

    Neilfg Funster

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    Not one for expensive ebikes, but quite impressed with 2.5 hrs charge time, mine take 5hrs, also I notice that Bosch and a couple of other suppliers have 12v Travel chargers, which would presumably be more efficient rather than using an Inverter and a 230v charger.
     
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  14. Phil J.

    Phil J. Funster

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    Thanks everyone for your input - you can always rely on Funsters to help!
    I am going to adopt the following on our next trip (and if it works it may be a good policy to adopt for other ebike owners in the same situation):
    • Charge where possible on the move - one battery at a time
    • Top up batteries every time they're used
    • When topping up batteries on the inverter (one at a time) do it half way through the day so the leisure batteries have had a top up on the solar and have time to recover after - best when the sun is shining
    • Don't charge both batteries at the same time and don't leave them too long before recharge
    By the way the reason I have a 1000w inverter is because it was already fitted when we bought it.
    We're away again a week on Friday for a couple of weeks sans EHU so I'll test the theory and, of course, report back.
    Thanks again Funsters
     
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  15. Linda and Steph

    Linda and Steph Funster

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    Can you recommend a good inverter to use while travelling for topping up via the cab cigarette socket ? (If I recall correctly the socket is 150w )
     
  16. Phil J.

    Phil J. Funster

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    Our inverter is a 1000w purchased originally from Roadpro. As I mentioned in an earlier post ours was already fitted when we bought our moho. However, as we spend most of our time without mains we've used itvquite a lot. I understand the problem is that the smaller ones are only good for charging very low voltage stuff that can normally done though a usb. The other thing is that there is always the risk of overloading the wiring to a cigarette socket where as the independent inverter from about 350w upwards is wired direct to your leisure batteries with heavy duty cable and can also be run whilst driving.
    Hope my thoughts help.
     
  17. Don Quixote

    Don Quixote Funster

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    Thats around 12.5amps load, but even though it says rated at 150watts I would be careful. To be honest I would wire it to the battery with an inline fuse.
     
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  18. Phil J.

    Phil J. Funster

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    That's where I'm coming from Don. Many don't realise the danger of overloading the electics.
    My inverter has wire about 5mm thick direct to the batteries with a fuse. I would also say having had to tidy up the electrics on ours it's a fairly simple job to install to the leisure batteries.
     
    Last edited: Aug 17, 2015
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  19. Tom A

    Tom A Funster

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    We have the following charger 20150825_135329.jpg and would like to charge e bike on the move. Also require something to charge laptop. Can anyone recommend an inverter please ?
     
  20. Scattycat

    Scattycat Funster

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    We charge our bike batteries off the inverter while travelling.
    It's worked for us so far
     
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