I need to get an inverter to power a charger for my wife's electronic bike. The e-bike uses a 37 volt Li-Ion battery. The 110 volt charger has a max DC output of 41.5 volts and a charge current of 2 amps. What size do you suggest? Would a 1000 watt do it? Also, does it have to be pure sw or is modified sw OK? I have 2 12 volt batteries.I have a little 300 Watt MS inverter that is fine for powering the TV and DVD player and to charge cell phones, etc, but I don't think it is big enough to power the e-bike charger.

I suggest at least 2 x 41.5 watts.

I would try the 300 watt inverter.41.5 x 2 is just 83 watts... doubt it would draw more than double.

I would stick with Pure Sine Wave.

I used to have a 24 volt scooter with a 2 amp charger, and used either a 150 or 300 watt portable inverter that plugs into the cigarette lighter.I would suggest a 300 watt MSW inverter - Modified Sine Wave. You do not need the much more expensive pure sine wave, it will work fine with MSW.I have bought a 500 watt Coleman brand MSW inverter at Costco for $30, but they do not sell them there anymore. Auto parts stores, or Amazon.com have a lot to pick from at $25 - $50 range. I would run a dedicated cigarette lighter receptacle to the area where you will be storing the bike, or perhaps under the awning in the storage compartment like I did. I used #10 wire and a 20 amp fuse, allowing up to about 200 watts output. I ran #10 wire to both the + and - not using the steel frame as a ground, it seems to have less voltage loss that way.Good luck!Fred.

300w is big enough, the charge input is only 83 watts

What size invertor? | Good Sam Community

14 Replies

MEXICOWANDERER
Explorer
May 19, 2016
" You figure it out, but looks to me like a 300 amp inverter. "

I think you meant 300-watt inverter
Almot
Explorer III
May 18, 2016
RJsfishin wrote:
My 36 volt E Bike's charger is ac 120v 1.5 amps in, and dc 36v 1.5 amp out

That's what I meant. They should read the AC watts and multiply it by 2, this would be minimum requirement for stable work of inverter.
MEXICOWANDERER
Explorer
May 18, 2016
300 watt Samlex pure sine wave inverter...

This is a good, solid unit.
DrewE
Explorer II
May 18, 2016
If the charger is putting out 85ish watts, it's not going to consume double that power from the AC line, not unless it's getting hot enough to be a fire hazard or at least to burn one's fingers. The energy consumed not sent to the battery has to go somewhere, and that somewhere pretty much has to be heat.

It is possible that it could consume 150 VA of apparent power if the power factor is poor. A 300W inverter should be plenty in any case and not break the bank. I would not expect any problems with an MSW inverter for this application.
wa8yxm
Explorer III
May 18, 2016
Yes a 1000 watt will do do do do do (several times over) the job

The charger is drawing about 100 watts. I like to go 1.5 to 2x for inverters

And though I like True Sine wave and feel it is best.. MSW **SHOULD** work, however I can not guarantee it.. I did note some years ago that some battery charger modules run very hot on MSW. Soem .. Do not.. Depends on the charger.
RJsfishin
Explorer
May 18, 2016
My 36 volt E Bike's charger is ac 120v 1.5 amps in, and dc 36v 1.5 amp out

You figure it out, but looks to me like a 300 amp inverter.
doughere
Explorer
May 18, 2016
The output is 84 watts, the input might be 2 or 3 times that (probably less than 1 1/2 times). 300 watts would be fine running. Possible input surge could be a problem; charger might not work well on MSW (overheating possibility).

Most electronic equipment will work with MSN, some won't; I had a DVD player wouldn't.

I would try it, checking the charger temperature first few times.

Doug
Almot
Explorer III
May 18, 2016
On the 2nd thought, this math is flawed because the data are insufficient.

42V*2A=84W DC. Big question is what it says on the AC end? With AC-DC chargers I wouldn't be surprised to see 150W AC input. So... check the label again and report back.
Almot
Explorer III
May 18, 2016
120W should be enough, considering losses and safety margins.

Your existing MS 300W is more than enough, in terms of power, but with $400-500 cost of ebike battery I would stick to PS.
I hear all the time - from customers and manufacturers - that these batteries don't last more than 5-6 years no matter how much you 're babying it, so, if it is older than 4 years - use your existing MS.
MrWizard
Moderator
May 18, 2016
300w is big enough, the charge input is only 83 watts