We've no mains power in the garage, which is quite a bit away from the
house. So I'm looking for a petrol generator to charge my mother's
electric mobility scooter.
The charger is the usual constant voltage type used for charging
sealed lead-acid batteries, and has the following info on the side
INPUT: 100-120/200-240 VAC, 50/60Hz, 4A
1. How powerful a generator would I need (in 'continuous' watts or
KVA) to comfortably run this charger?
2. Would any suitably-rated charger suffice? OR would I need to buy
one of those very expensive digital 'inverter' types like the Honda
EU20i or something similar.
I shall be much obliged for any guidance. TIA.
BTW - is 1 watt the same as 1 KVA? I'm confused.
P.S. I'm in the UK.
Karen, a small generator should suffice to charge batteries. if you are
charging 24 volts at 8 amps you are charging at 192 watts, however due to
the length of time needed to charge the batteries, the probability that the
generator will be left unattended, the fire hazard, fume hazard, the
cussedness of getting these things to start sometimes, the necessity for
maintenance and oil changes, and the fact that these things wear out sooner
or later, i would suggest that you have electric service installed (run a
wire) if it possible for you to do so.
you might even talk someone into getting you an electric garage door opener
for Christmas :)
1 kW is not exactly the same as 1 kVA but in this case its bound to be
if you do decide to get the generator you might look for one with a 24V DC
output. then there would at least be one less gizmo to catch fire when you
aren't looking :)
Thanks for your help Tim and I hear what you're saying about getting
electric installed. However, that's not an option for several reasons
- the main ones being distance from the house and the fact that over
here in the UK power companies make 'standing charges' for metered
electricity which can result in one's quarterly 'standing charge'
being much more than the amount of electricity used.
Also - would I be correct in assuming that a cable from the house
would result in a considerable voltage drop over a 100 metre run? I
seem to recall something about this from school physics lessons ;-) If
so, would it affect the operation of this charger?
sory, i dont understand this :) is that like a flat rate plus usage? and
it would cost more to run a branch from existing service?
you are correct but lets try some rough calculations to see how much the
loss will be.
your estimated load was less then 200 watts. add a little loss in the
charger lets call it 200 watts.
200 watts / 220 volts = .9 amps
100 M = 328 feet
10 AWG wire has .9989 ohms per 1000 FT (according to the first handy chart i
lets round that off to 1 ohm per thousand
328 / 1000 x 1 = .328 ohms.
now since it take 2 wires to make a circuit we multiply by 2 to get a total
of .656 ohms
the formula for voltage drop is I squared R so .9 x .9 x .656 = .53 volts.
of course if you are going to wire your garage you will probably add in a
being in the USA i picked 10 AWG wire. i hear wire tends smaller sizes in
the UK. fortunately the calculations stay the same.
i have a number of generators at work that i am responsible for. some are
small and portable and some are fixed and generate 100,000 watts. ALL of
them are a pain in the posterior in one way or another. i had a problem with
one blowing an overcrank breaker instead if starting when it was needed. the
factory feild service charged me $600 USD to tell me that my transfer switch
was way too old and i needed a new one.
i have a brand new $40,000 USD generator sitting there, not working because
a second stage propane regulator is on back order.
sorry to get side tracked here... i don't know what your situation is in
regards to running overhead or underground cable... maybe a long extension
cord would work :)
maybe a little shed next to the house just for the electric cart.
if you do get a little generator, try to find one with a fuel tank large
enough to run for a long time. i would not be to happy about having to set
an alarm to get up at 3 AM to refill a tank.
Yes. They make a charge for using their meter ;-) Then each unit of
electricity used is charged on top of that. To give you an idea - when
pop was alive his annual bill for units was much less than the annual
standing charge - so being a canny Scotsman he asked them to
disconnect the service. That was about 20 years ago. Now we 're sorry
he did that of course...
Meanwhile, I'm very grateful for your calculations and will keep them
for reference. 0.53 volts on the wire gauge you quote doesn't seem
much, does it? And the charger is quite tolerant when it comes to
input voltages. Whereas the little shed next to the house is something
we did not think of. In fact - there's space for one round the back. I
shall look into this tomorrow. The main problem with getting work done
round there is that mum can't be bothered now with what she calls
'men' knocking about and making a mess of things. So although there's
much needing 'done' round her house she keeps putting it off because
of her reluctance to deal with tradespeople. This is a common
reluctance of older folks so I believe. Hence the generator idea was
just a way of charging her buggy 'transparently' as it were.
However, I do take your points about generators generally. Those ones
you have sound complicated and very expensive to repair. Yet, all
hassles aside, I was wondering if in the end we do decide on the
generator route whether an ordinary petrol device would do or whether
we'd have to get one of those rather pricey 'inverter' types just to
run that charger. I say this because I've heard from a not terribly
reliable source that ordinary gens might cause problems for sealed
lead-acide type constant voltage chargers like the one we have for the
cart. Something to do with the sine wave outputs not being pure
enough....or summat. A bit like inverters maybe...modified as opposed
to pure sine wave? I dunno ;-)
Absolutely. I don't fancy that either. But with mum's useage the cart
charges up from the mains in about three hours. We wouldn't have to
leave it on all night or anything.
I'm not sure about an inverter Dean. Over here decent ones for that
input are quite expensive. As for wind or solar power....? Again the
cost and the installation would tend to rule those out.
Strictly speaking this cart thing should be kept in the house, which
it currently is. However, my mother says it looks unsightly and is
thus keen to have it removed to the garage.
Many thanks for your advice.
"> >> Thanks for your help Tim and I hear what you're saying about getting
if this is a simple automotive or marine type charger it is little more then
a transformer and diodes. there will be a couple breakers in it to protect
from shorts and overheat.
there might be a sensor to detect full charge and switch to trickle charge.
the smallest and least cost unit you can find will probably be sufficient.
here is on that is not so small, and probably not so cheap but it will run
on several types of fuel
a good plan might be to call a local generator repair shop to see which ones
they can get parts for. they might even have something used/refurbed for
I say this because I've heard from a not terribly
ill have to take your word for it :) check the A-H (ampere-hour) rating of
if they are 100 A-H it would take at least 100 A-H / 8 amps = 12.5 hr to
charge if fully depleted.