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Charging your E-bike via an inverter and a 12v battery


MadKon

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Can I charge my e-bike with a pure sine wave inverter connected to 12 volt battery? Have any body done this before?

I have a 12 Volt 105Ah battery as my power source. Which should give me 1260 Wh.

My e-bike battery have a 36 Volt 625 Wh battery. Power needed is about 17.36 Ah

With losses of about 85% max I should be able to recharge at least once before I need to charge the battery again. 

I go off grid allot and want to take my bike with but I don't want to get "stuck" without power.

Edited by MadKon
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Very possible just need to match the power of the inverter to the charger

 

But issue will be battery life of the lead acid battery if you discharge too deeply, lifetime nosedives with depth of discharge, you dont really want dip more than 20-30% DOD  of regular basis, so maybe add more batteries or get a Lithium one.

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As an off grid guy you probably know this already, but here is for future reference for others as well.

 

Check the ebike chargers watt rating, and make sure your inverter's output matches that, prerefably you want the inverter wattage to be higher.

 

I doubt whether the charger will pull a wattage spike like a motor will on start-up. But the charger has one job, and that is to put as many watts into the ebike's battery in as short a time as possible, so it will pull a lot of amps until the ebike battery is about 80% full and then pull less amps. (This is a thumbsuck, different chargers have different protocols.)

So your inverter will need to be able to supply this current.

 

If you are charging from your vehicle, and the inverter can support it, I'd suggest charging the ebike while driving if possible, thus saving your deep cycle battery from the bulk charging phase.

Edited by PhilipV
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As an off grid guy you probably know this already, but here is for future reference for others as well.

 

Check the ebike chargers watt rating, and make sure your inverter's output matches that, prerefably you want the inverter wattage to be higher.

 

I doubt whether the charger will pull a wattage spike like a motor will on start-up. But the charger has one job, and that is to put as many watts into the ebike's battery in as short a time as possible, so it will pull a lot of amps until the ebike battery is about 80% full and then pull less amps. (This is a thumbsuck, different chargers have different protocols.)

So your inverter will need to be able to supply this current.

 

If you are charging from your vehicle, and the inverter can support it, I'd suggest charging the ebike while driving if possible, thus saving your deep cycle battery from the bulk charging phase.

Agree as a rule I apply a factor of 2 when matching inverters to load so if you need 100w go for a 200w inverter. If the load includes the start current for a motor I apply a factor of 3.

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Can I charge my e-bike with a pure sine wave inverter connected to 12 volt battery? Have any body done this before?

I have a 12 Volt 105Ah battery as my power source. Which should give me 1260 Wh.

My e-bike battery have a 36 Volt 625 Wh battery. Power needed is about 17.36 Ah

With losses of about 85% max I should be able to recharge at least once before I need to charge the battery again. 

I go off grid allot and want to take my bike with but I don't want to get "stuck" without power.

 

your 105ah battery will only do 105ah when brand new.  pull it lower than 50% a few times then you quickly learn the joys of Lead acid (they don't last).  You might get 40ah if you lucky after about 10-20 cycles below 50%.

 

You also not state if this is a normal car battery (made to deliver amps, not capacity) or "deep cycle" battery.   

 

I would get a lithium bank as others stated or you will need at least 400ah lead acid bank to keep your source battery to last even a year with regular use.  Lithium you will get away with 150ah and last about 5000 cycles.

 

 

Personally i get a small 800w petrol generator .(or if you have cash, a silent honda generator). they quite enough to run and take up far less space and can be used for many other things as well.

 

Edit:  Just go buy 2-3  spare batteries for they bicycle and charge them when you get to power source

Edited by Karman de Lange
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your 105ah battery will only do 105ah when brand new.  pull it lower than 50% a few times then you quickly learn the joys of Lead acid (they don't last).  You might get 40ah if you lucky after about 10-20 cycles below 50%.

 

You also not state if this is a normal car battery (made to deliver amps, not capacity) or "deep cycle" battery.   

 

I would get a lithium bank as others stated or you will need at least 400ah lead acid bank to keep your source battery to last even a year with regular use.  Lithium you will get away with 150ah and last about 5000 cycles.

 

 

Personally i get a small 800w petrol generator .(or if you have cash, a silent honda generator). they quite enough to run and take up far less space and can be used for many other things as well.

 

Edit:  Just go buy 2-3  spare batteries for they bicycle and charge them when you get to power source

Or even better just add a 300 w solar panel with a MPPT Solar charge controllers to the battery and charge during the day.

 

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Or even better just add a 300 w solar panel with a MPPT Solar charge controllers to the battery and charge during the day.

 

 

300W panel is MASSIVE..... and you would need 2 as you won't get enough voltage out on most days on single panel to get to fully charged voltage of the battery bank (about 48v), (Most mppt inverters need higher input voltage than output)

 

   Probably should ask if Madkon if he/she have space to even carry this charge system in his car/truck/bicycle ;

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300W panel is MASSIVE..... and you would need 2 as you won't get enough voltage out on most days on single panel to get to fully charged voltage of the battery bank (about 48v), (Most mppt inverters need higher input voltage than output)

 

   Probably should ask if Madkon if he/she have space to even carry this charge system in his car/truck/bicycle ;

I got the impression that this was not a portable set up, assuming it isn't the 300w panel measures 2x1m and with an input of 300w it should charge a 365w battery in about 1-3 hours if fully discharged. You could go for smaller solar panels it will just take longer. As a back check my overland camping set up uses about 22ah overnight and it takes about 5 hours for the 130w panel to charge it back to 100% while the fridge is still drawing off it. If I disconnect the fridge it takes less than 3 hours so that gives about 7ah /130 watt  in an hour, so that it's possible to use a smaller panel. The price difference is about R400 on R1200 to get double the capacity which helps on cloudy days so if you have the space go for the bigger panel.

 

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I got the impression that this was not a portable set up, assuming it isn't the 300w panel measures 2x1m and with an input of 300w it should charge a 365w battery in about 1-3 hours if fully discharged. You could go for smaller solar panels it will just take longer. As a back check my overland camping set up uses about 22ah overnight and it takes about 5 hours for the 130w panel to charge it back to 100% while the fridge is still drawing off it. If I disconnect the fridge it takes less than 3 hours so that gives about 7ah /130 watt  in an hour, so that it's possible to use a smaller panel. The price difference is about R400 on R1200 to get double the capacity which helps on cloudy days so if you have the space go for the bigger panel.

 

 

Must then go with 2 x 150w ...most panels only push out about 42v at full power with no load

  

36v battery is charged at 42v, so you need to have more than that available to get it to 42v

Mptt don't ramp up voltage, only reduce it.

 

So to get 42v output on the mptt you will need at least 45v input .   So with losses you talking at least 2 panels in series with a 36v MPPT

 

this is of course all on the assumption that the intelligence is in the battery itself (all balancing/cut offs etc)  (you don't want to overcharge your lithium pack).

Also hope there voltage out on the charge points of the pack so MPPT can detect its connected

 

And probably void warranty ...  Sounds to much pt .. I would still just buy 1/2 extra packs

Edited by Karman de Lange
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Must then go with 2 x 150w ...most panels only push out about 42v at full power with no load

  

36v battery is charged at 42v, so you need to have more than that available to get it to 42v

Mptt don't ramp up voltage, only reduce it.

 

So to get 42v output on the mptt you will need at least 45v input .   So with losses you talking at least 2 panels in series with a 36v MPPT

 

this is of course all on the assumption that the intelligence is in the battery itself (all balancing/cut offs etc)  (you don't want to overcharge your lithium pack).

Also hope there voltage out on the charge points of the pack so MPPT can detect its connected

 

And probably void warranty ...  Sounds to much pt .. I would still just buy 1/2 extra packs

 

As much as I agree with you ...... have a look at the cost of extra batteries.

 

 

It was expensive before lockdown, with the new covid tax on everything it is simply absurd !!

 

 

 

 

 

As a side note  -  I am looking at my options, as I already have a small 12V PV system running my home lights.  Been using this for almost 5 years.  Only use eskom for the tv, fridges and washing machine.  Summer time this battery is fully charged early in the day .... with the correct inverter, I could easily charge the ebike batteries from this system.

Edited by ChrisF
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Must then go with 2 x 150w ...most panels only push out about 42v at full power with no load

  

36v battery is charged at 42v, so you need to have more than that available to get it to 42v

Mptt don't ramp up voltage, only reduce it.

 

So to get 42v output on the mptt you will need at least 45v input .   So with losses you talking at least 2 panels in series with a 36v MPPT

 

this is of course all on the assumption that the intelligence is in the battery itself (all balancing/cut offs etc)  (you don't want to overcharge your lithium pack).

Also hope there voltage out on the charge points of the pack so MPPT can detect its connected

 

And probably void warranty ...  Sounds to much pt .. I would still just buy 1/2 extra packs

I think you're on a tangent my reading of the OPs requirement is that he needs an inverter to connect his 12volt battery to. That implies that he has a bespoke charger which operates off a normal 230v supply which is why I am more focused on the power produced than the volts.

 

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I think you're on a tangent my reading of the OPs requirement is that he needs an inverter to connect his 12volt battery to. That implies that he has a bespoke charger which operates off a normal 230v supply which is why I am more focused on the power produced than the volts.

 

 

completely misread your post ..  :oops:    thought you mean charge direct from panel to battery (something I would do)

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Madkon thanks for prompting me to finally do the experiment ....  :whistling:

 

This battery box has a 120A.h Gel battery.  It handles higher currents and lower discharges better than traditional batteries.  Paired with a quality inverter it is very handy "anti-eskom-load-shedding" device ....

 

I connected the ebike-battery charger to this, and monitored the charge.

 

post-110956-0-97872300-1602686229_thumb.jpg

 

 

The initial high charge rate explained why my previous attempt with a smaller inverter did not work.  It starts charging at 22,9A with a battery voltage of 12,4V, thus about 284W.

 

post-110956-0-43854000-1602686378_thumb.jpg

post-110956-0-89748200-1602686383_thumb.jpg

 

 

At about 50% state of charge for the ebike battery the charge rate started lowering.  It is now drawing about 15,5A from the gel battery, at about 12,6V. 

 

NOTE - the "50%" of the ebike battery is a best guess ..... I would have to do more tests, and log more data to accurately show the decline in charge rate as the ebike battery reaches a higher state of charge.

 

 

EDIT - staying steady on the 15,5A charge rate for some time now ..... 

 

 

 

 

So yes it can be done.  BUT, these are high currents.  Make sure to use the correct equipment, properly sized cables, etc.

 

And be SURE to use a very good quality pure sine wave inverter.

 

 

 

How many times can you charge an ebike battery from a "car battery" ? .... uhm ja .... this will put a very good load on a deep cycle battery, not sure I would subject a car battery to this.

 

As others have suggested .... THICK cables, decent inverter, and charge it while you are driving, ie while the alternator can supply the juice.  And then I will make sure to only do so while the headlights, wipers etc are NOT being used.  

 

 

 

 

 

 

As for me doing this via my little solar system ....  :thumbup:   Certainly a possibility !!  I would wait until the PV system battery is fully charged, then start charging the ebike battery.  During the high charge stage the battery will supply 60%, and my small PV panel 40% (good sun conditions), then as the ebike battery charges and the charge rate drops the PV would supply more and more of the charge rate.  So maybe 20A.h load on the PV battery, which can be topped up later in the day.  But this is based on a little 100W panel, with a 150W panel the system will be balanced better.... but now I am deviating from the core principle of the small systems for the lights .... 

Edited by ChrisF
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I've connected an Inverter to the car battery (Car Running) and Ran a Kettle to Boil on It.

I wasn't comfortable doing It. Is it OK to do this or not ?

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