# Charging ebikes off grid?



## Dgo Shelley (May 23, 2020)

Hi, 

Wondering if there is any way to trickle charge a Specialized battery while off grid camping, beyond hooking to a generator? Can I somehow charge off a solar panel or car battery?

Thanks,
Shelley


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## Fuse6F (Jul 5, 2017)

Id bring a spare barrtery and solar panel and charge controller. Then run an inverter to ac and plug in the bike charger. 

This isnt the most efficient way as a dedicated boost converter for your ebike would be best. But this will get the job dont. 

Bunch of equipment to bring along. But you brought an ebike to live off grid. So guess you dont mind extra stuff.


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## Dgo Shelley (May 23, 2020)

Fuse6F said:


> Id bring a spare barrtery and solar panel and charge controller. Then run an inverter to ac and plug in the bike charger.
> 
> This isnt the most efficient way as a dedicated boost converter for your ebike would be best. But this will get the job dont.
> 
> Bunch of equipment to bring along. But you brought an ebike to live off grid. So guess you dont mind extra stuff.


I have a house but have been in my camper this year (for fun) w/ shore power. But with the back country opening this week, I am ready to go off grid for a few days here and there. Can bring a Honda 2200i if that's my best option. Have a nice set of Zamp panels and was hoping there was a way to top the battery off of those & not need the generator.

Or I could bring the hardtail & skip it of course, but it would be fun to be off grid with the e-bike.


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## Fuse6F (Jul 5, 2017)

Even better would be to be plugged in to solar while pedalling/trekking. 

What model is your bike?


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## Charliektm400exc (Jan 10, 2020)

I’ve charged both our ebikes from the car and/or caravan battery via an inverter with no problems at all


Sent from my iPad using Tapatalk


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## PierreR (May 17, 2012)

Charging an e bike by solar would be very slow, inefficient and spotty. If your panels are big enough and you have the right controller then solar would likely be viable.

Alternators are very inefficient for producing electricity to charge a car battery. By the time you run that through an inverter and then through your charger you are super inefficient with the use of power. 

The Honda is quite efficient and will save in the long run in most of your situations. 

I would say under the best of conditions, use solar. Second use the Honda and third convert from a car and battery. 

When using something like the Honda, fast charging is the way to go IF the BMS (Battery Management System) will support it and you have a high capacity charger. You end up running the generator a lot less time . With a 5-10 amp charger it does not take long for most e bike batteries. 

If you are savvy you can usually bypass the BMS through the discharge connections with a high capacity smart charger and some monitoring. On e bike batteries you have the charger connections (front door to the battery) and the discharge connections that plug into the bike itself and run the bike (back door to the battery for charging) The back door allows for much higher current flow.


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## Dgo Shelley (May 23, 2020)

Charliektm400exc said:


> I've charged both our ebikes from the car and/or caravan battery via an inverter with no problems at all
> 
> Sent from my iPad using Tapatalk


Thanks! Guess I need to buy a small inverter and try it. Glad to know it is quite possible.


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## Dgo Shelley (May 23, 2020)

PierreR said:


> If your panels are big enough and you have the right controller then solar would likely be viable.
> ...
> 
> If you are savvy you can usually bypass the BMS through the discharge connections with a high capacity smart charger and some monitoring. On e bike batteries you have the charger connections (front door to the battery) and the discharge connections that plug into the bike itself and run the bike (back door to the battery for charging) The back door allows for much higher current flow.


Thanks, I'll check further into the option of a high speed charger. Would be nice to reduce generator time.

I have an extra car battery (have more than 1 camper, slight mental problem with collecting campers ) and that plus an inverter would probably work well. I'm in the SW US with lots of solar gain.

I'll get a small portable inverter and test the whole setup, might as well, I'm camping anyway.


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## PierreR (May 17, 2012)

In regards to high power chargers. High power depends on the size of battery that you have. For a 500 Watt hr battery, 5-6 amps is big and larger must be used with caution. For double that a 10 amp is fine. 

Not all inverters are created equal and some of the cheaper one's do not work well to charge Li ion batteries. Your Honda is a sine wave inverter generator and is far superior for charging. Sine wave, not modified sine wave inverters are the most efficient and safest for charging batteries. Some modified sine wave inverters approach the efficiency of pure sine wave but are not that much cheaper. It's best to check the recommended uses for an inverter before purchase.


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## Fuse6F (Jul 5, 2017)

PierreR said:


> In regards to high power chargers. High power depends on the size of battery that you have. For a 500 Watt hr battery, 5-6 amps is big and larger must be used with caution. For double that a 10 amp is fine.
> 
> Not all inverters are created equal and some of the cheaper one's do not work well to charge Li ion batteries. Your Honda is a sine wave inverter generator and is far superior for charging. Sine wave, not modified sine wave inverters are the most efficient and safest for charging batteries. Some modified sine wave inverters approach the efficiency of pure sine wave but are not that much cheaper. It's best to check the recommended uses for an inverter before purchase.


ac power is a sine wave. so most power tool motors dont like choppy power from cheap inverters. switching power supplies will have current surges to run and keep the output smooth. this can be hard on the inverters if they cant keep up with those instantaneous power demands. just run an oversized inverter (eg. 1000w) and you should be fine.

ebikes use li battery packs with specific charge controllers designed to properly charge them. Don't bypass this system!!!

a battery, charge controller, solar panel and inverter is a bunch of equipment. But it will run for a very long time with little maintenance.

if you have 500whr bike battery. If your bike charger charges the battery in 2hrs then thats an average 250w push. Given some inverter and charger inefficiencies you likely pull 25a from that 12v car battery. Thats a ton. like 5 high beam (traditional headlights) for two hours. You will need big finger fat cables to the inverter.

recommend 
marine deep cycle 100ahr would charge the bike from full flat once a day
10ahr charger. 
100w solar panel. 
1000w inverter

since the Honda jenny is putting out 120v. it will not need the heavy wires, etc. but will need a jerry can. but plan to run the jenny for 2 - 3 hrs ish at a time. a 1000w jenny would be fine. you could charge bikes all day and night if you like.

hope that helps.


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## Charliektm400exc (Jan 10, 2020)

Dgo Shelley said:


> Thanks! Guess I need to buy a small inverter and try it. Glad to know it is quite possible.


Don't get one that's too small you need to have enough capacity to run your mains charger. I'm pretty sure ours is 300w, but can't check at the moment.

Sent from my iPad using Tapatalk


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## RickBullottaPA (Mar 4, 2015)

Charliektm400exc said:


> Don't get one that's too small you need to have enough capacity to run your mains charger. I'm pretty sure ours is 300w, but can't check at the moment.
> 
> Sent from my iPad using Tapatalk


150W is enough to use the Shimano slow charger. I use the inverter from EGO that allows me to use the batteries from my electric mower, snow blower, chainsaw, trimmer, etc. to charge my eMTB. I also use it to power a 50" TV.

https://www.acehardware.com/departm...cessories/cordless-tool-battery-packs/3924396


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## levity (Oct 31, 2011)

Goal Zero makes several portable power stations, from 400-3000W. We picked up a Yeti 1400 on sale a few years ago, and it has served us well for charging our Levos off-grid. We keep the Yeti topped off during the day using the solar panels on top of our camper van.


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## Dgo Shelley (May 23, 2020)

So much excellent info here! Thank you all! 

Specialized actually sent me back something, too, which makes them super cool in my book. I didn't expect an answer.

Remote charging like this is not something we actively support. Below is the most information I can provide on it. 

Charging a Turbo battery directly via a 12V battery of a car, mobile home etc. 
•	not possible (current too low) and we do not offer a dedicated charger
•	you need a 220/230V inverter
Charging a Turbo battery via a 220/230V inverter 
•	this is the only working method in combination with a car or mobile home battery
•	charger consumes 220W
•	max. consumption of the 4A charger is max. 2.5A/575W (e.g. when powering up charger)
•	all high-quality inverters that are able to supply the charger with sufficient power should work
•	Pure Sine-wave inverter is needed


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## PierreR (May 17, 2012)

Fuse6F said:


> recommend
> marine deep cycle 100ahr would charge the bike from full flat once a day
> 10ahr charger.
> 100w solar panel.
> 1000w inverter


You would need at least a 200 amp hour battery to pull 25amps of 12V for a two hour charge because the Lead Acid Car Battery is a 20C battery. Many RV,s have two 6V golf cart batteries for the house batteries and that is 200 amp hours.

The weather has got to be sunny and the panel system new in order for a 100 watt panel to top off the house batteries for a one bike charge in a single day. Solar is not reliable enough to count as your only means of charging your bike if you ride your bike low battery status every day.

Starting the RV to charge the battery is very inefficient and a big waster of gasoline. Alternators are very inefficient requiring a lot more power and gasoline than the Honda Generator.


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## Dirtrider127 (Sep 17, 2010)

My Levo 700W battery has a charger that puts out 48V/ 4amps.
I can charge it off the car using a 1000W sene wave inverter. A smaller inverter will not charge correctly and damage your $200 charger


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## Fuse6F (Jul 5, 2017)

PierreR said:


> You would need at least a 200 amp hour battery to pull 25amps of 12V for a two hour charge because the Lead Acid Car Battery is a 20C battery. Many RV,s have two 6V golf cart batteries for the house batteries and that is 200 amp hours.
> 
> The weather has got to be sunny and the panel system new in order for a 100 watt panel to top off the house batteries for a one bike charge in a single day. Solar is not reliable enough to count as your only means of charging your bike if you ride your bike low battery status every day.
> 
> Starting the RV to charge the battery is very inefficient and a big waster of gasoline. Alternators are very inefficient requiring a lot more power and gasoline than the Honda Generator.


you will have to explain 20c

i do agree solar is not always reliable! i dont control the sun and clouds.
but if you count having gas on hand and fresh oil for the genny... plus the noise! plus time spent travelling for more fuel and the use of fuel to do that and the wear and tear on the vehicle and the lost riding time, etc.

marine batteries are designed for deep discharge cyclic operation. such as running my trolling motor but also start the engine.

https://www.westmarine.com/buy/west...105-amp-hours-group-31--15020332?recordNum=10

two dedicated 6v rv battery will last longer and perform better in the long run, but are more money.

if your charging for 2 hours, assuming you drained the bike that much each ride. you can safely charge all day and night (get back late and plug in), even if not around or not awake yet. so there are a few advantages of solar. note. get a solar charger with a lvd.

to calculate this out...

100ahr bat discharged by 18.5a for 2 hrs is about 37% draw down.
fudge capacity and call it 50% draw. so we have the battery.

you probably have 12-14 hours to charge during summer hours. 
but lets assume 10.
the 18.33a draw for 2 hrs becomes 3.7a charge requirement for 10 hrs (some overhead).

a 100w panel will give about 6.8a at charge voltage. fudge solar energy to account for charge losses by 20% and you still have 5.5a charge getting into the battery.

this means you only use 67% of the 10hrs charge time. so we have more to account for variability in sun.

more panel is always a good idea. not necessarily more battery. with the 10a charger specified, you could run a second panel in parallel but turned to focus on morning and late afternoon sun. just in case there is cloudy weather during part of the day. 15 or 20a charger is better in this scenario.

now you would have to double the system if charging more than once a day or more bikes. batteries do age and the capacity reduces. winter temperatures reduce the total capacity available, etc. we can go on and on, but the quoted system is sufficient for use during summer.


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## PierreR (May 17, 2012)

Fuse6F said:


> you will have to explain 20c
> 
> if your charging for 2 hours, assuming you drained the bike that much each ride. you can safely charge all day and night (get back late and plug in), even if not around or not awake yet. so there are a few advantages of solar. note. get a solar charger with a lvd.
> 
> ...


Batteries have a C rating. C rating is the number of hours it takes to draw all of the available amps from a battery as rated. Lead acid takes 20 hours to draw the amps down to zero and nearly as long to charge back up. Lead acid is a 20C battery.
A Lithium ion battery has a rating from 1-4 C meaning you can pull amps pretty continuously from them. 
A 100 amp lead acid battery can sustain a 5 amp draw. The 18.5 amps you are talking about will depress the voltage and amperage quickly. Probably unsustainable within two hours on a battery that is one year old. There are battery capacity calculators on the internet to tell you what capacity you need.

Real world capacities on solar panels are 11% to 20% of nameplate. Meaning, a 100 watt panel can be expected to produce 264 to 504 watt hours per day before your charging losses are figured in. You really need three panels if you are going to count on Solar.


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## Fuse6F (Jul 5, 2017)

PierreR said:


> Batteries have a C rating. C rating is the number of hours it takes to draw all of the available amps from a battery as rated. Lead acid takes 20 hours to draw the amps down to zero and nearly as long to charge back up. Lead acid is a 20C battery.
> A Lithium ion battery has a rating from 1-4 C meaning you can pull amps pretty continuously from them.
> A 100 amp lead acid battery can sustain a 5 amp draw. The 18.5 amps you are talking about will depress the voltage and amperage quickly. Probably unsustainable within two hours on a battery that is one year old. There are battery capacity calculators on the internet to tell you what capacity you need.
> 
> Real world capacities on solar panels are 11% to 20% of nameplate. Meaning, a 100 watt panel can be expected to produce 264 to 504 watt hours per day before your charging losses are figured in. You really need three panels if you are going to count on Solar.


That is incorrect.

Please post some references to educate myself and others.

Specifically 20c information and solar ratings.

Thank you


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## PierreR (May 17, 2012)

Fuse6F said:


> That is incorrect.
> 
> Please post some references to educate myself and others.
> 
> ...


 Solar is politically charged as noted by your "That is incorrect" statement and will have to wait. Solar is also much more complicated than batteries and is probably beyond the scope of this thread and would likely close the thread down.

Batteries 
Batteries are complicated to understand but are simple to understand in comparison to solar power. I have included a reference but as you will note; The C rating makes it sound like the higher the C rating the more power the battery has. I have singled out is the practical application of C rating within this PFD in the following bullet point. The practical application seems opposite to the definition of C rating.

"• Capacity or Nominal Capacity (Ah for a specific C-rate) - The coulometric capacity, the total Amp-hours available when the battery is discharged at a certain discharge current (specified as a C-rate) from 100 percent state-of-charge to the cut-off voltage. Capacity is calculated by multiplying the discharge current (in Amps) by the discharge time (in hours) and decreases with increasing C-rate."

https://web.mit.edu/evt/summary_battery_specifications.pdf

Deep cycle lead acid batteries are all about a 20C rating meaning, they have a lot of capacity but at the expense of decreasing available power. 20C means the amount of power you can pull from a battery is the capacity divided by 20 100 amp hr / 20 hours = a rate of discharge of 5 amps continuous. 
Now pulling higher power depresses terminal voltage and with a constant load starts to pull more amperage. Power = volts * amps. Voltage goes down and amps go up for the same amount of power. Its a continuous loop cycle getting worse till you don't have enough available power to charge the bike, long before the deep cycle battery is discharged.

In an E bike we call this voltage drop, Sag. Sag increases with battery age and number of charges. Charging a bike battery to 100% should be done about every 5 charges or so to equalize the cells and reduce Sag.

Now for practicality of application. A marine 12v deep cycle battery is a compromise hybrid between a starting battery and a deep cycle battery. (number of plates and plate thickness). You will likely, with a new 100 amp hr marine battery, fully charged and the right inverter, get one full charge for the e bike out of it.

Can you do this day in and day out with only a 100 watt solar panel setup? Not likely, use the Honda as a backup. The 2000 watt sine wave inverter Honda generator the OP already owns, will charge the deep cycle battery and the bike at the same time. The Honda puts out 12V for charging house batteries and 120V ac for charging the bike. For me, being on a vacation to bike and not being able to charge when and where I want is not acceptable. I'm retired so I could go without for a day but I don't want to.

There is an alternative to Lead Acid. At only twice the price, four 100-200 amp LiPo's in series is a 12V with the smart voltage regulator for charging. Low C rating and infinitely longer life.
https://antybattery.aliexpress.com/...html?spm=a2g0o.detail.100008.3.4a2938d70QD6hE


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## Fuse6F (Jul 5, 2017)

PierreR said:


> Solar is politically charged as noted by your "That is incorrect" statement and will have to wait. Solar is also much more complicated than batteries and is probably beyond the scope of this thread and would likely close the thread down.
> 
> Batteries
> Batteries are complicated to understand but are simple to understand in comparison to solar power. I have included a reference but as you will note; The C rating makes it sound like the higher the C rating the more power the battery has. I have singled out is the practical application of C rating within this PFD in the following bullet point. The practical application seems opposite to the definition of C rating.
> ...


good. now we have something to discuss. and thank you for taking the time to respond.

20c is a rating applied to this type of battery (lead acid). it allows you to compare different brands and sizes of batteries to determine capacity.

it essentially means... what is the capacity of the battery if discharged 100%, during a period that will take exactly 20 hours. eg. a 20ahr battery can supply 1A for 20 hours continuous until 100% depleted.

it doesnt mean that the battery will not provide a specific higher amperage for a shorter time period. this is what i wanted you to research and come to conclusion on. you may draw higher current loads than the rated 20hr specified value.

now as far as draw down of the voltage. this is a normal function of lead acid battery depletion. but there is an internal resistance to each battery. this provides two effects. one it drops the voltage available from the battery and this drop varies with current load (ohms law here) and second, placing a higher current load will deplete more energy as heat internal to the battery and as such, you get less energy out than its rated capacity at the 20hr rate. you also get slightly more capacity at draw rates longer than the 20hr rate.

you will have to review the specifications for the battery used, but as i have already done so, for a good marine battery and even better for deep discharge batteries the 18.3 amp draw is below the rated maxim current draw for 100ahr. by a suitable margin.

now charging this battery is important to discuss. if you have too large of a battery, you wont be able to fill it in the time available with a given solar panel. eg. filling a swimming pool with a garden hose vs a kiddie pool. and there is no better way to ruin a lead acid battery than by too deeply discharging it. even worse, to then not properly recharge at the recommended rates, which varies from battery to battery depending on the battery capacity. proper recharge requires a three stage charger and even better... one that is temperature compensated.

lead acid batteries are comprised of cells internal to the battery. sag as you put it would refer to the internal resistance of the battery. the condition of the plates and electrolyte inside make up this resistance.

my recommendations are for 2 hrs charge for part time use during summer conditions. you wont get to charge the marine battery if there is no solar. eg. raining. but i wouldnt be riding in the rain and need a charge.

i am not sure how efficient different inverters are. that could change things a bit.

now if i was recommending a system that guaranteed ebike charging every day, which included multiple days with absolutely horrible solar conditions (eg. a week of rain) and then allowed charging use to continue while the solar made up for the horrible days until it returned to full capacity again before the next weather front came in. and this factored in the aging of the battery over 5 years and the need to charge at -35c for winter ebike use and the shorter hours and lower sun position during winter.... then this would be completely different. you would need a truck and trailer just to haul it around.

it is nice to have a honda jenny. but its even nicer to have a good little solar unit that quietly charges your bike without the noise and fuss. stays connected indefinitely and picks up again in the morning automatically while your snoozing away.


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## PierreR (May 17, 2012)

Fuse6F said:


> good. now we have something to discuss. and thank you for taking the time to respond.


Very condescending response. I have misread you as you have misread me. 
We design to different standards and neither of us know the acceptable standard of the original poster. If I had to guess you are probably closer to the standard than I am especially given the backup generator and the fact that we are talking about an e bike, not a yacht.


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## Fuse6F (Jul 5, 2017)

PierreR said:


> Very condescending response. I have misread you as you have misread me.
> We design to different standards and neither of us know the acceptable standard of the original poster. If I had to guess you are probably closer to the standard than I am especially given the backup generator and the fact that we are talking about an e bike, not a yacht.


are you in management?


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## PierreR (May 17, 2012)

Fuse6F said:


> are you in management?


Yes and no. I am semi-retired and probably will be that way for a while. I am in management when forced there by circumstances. 
I am a problem solver, mostly in manufacturing. I can literally build any machine you want for any purpose or repurpose a machine to do what you want as your circumstances change. I tell people that I am the janitor because I clean up other peoples mistakes and messes.

I design and build to the philosophy of this equation

E + CFM = QO

Equipment + Complete Fking Moron = Quality of the Outcome.

A CFM isn't stupid. A CFM is semi smart, lazy and has a lack of common sense. They will fiddle with a machine and fk it up. They will bypass safety systems. They will adjust things that affect other processes down the line and the list goes on.

In the case of solar and off grid systems, Mother Nature is more the underestimated CFM resulting in under designed systems that don't live up to the expected outcome.

I read you as under designing a system but my mistake is in not really seeing the end user and budget. Forums such as this one are a form of recreation for me and so my guard is down occasionally and I can make to many assumptions.

When I backed off and looked at what you suggested and realized that it's a pretty good low cost 85% system that will last 2-3 years with little maintenance provided the solar panels don't get too hot on top the RV. Not bad given the original poster already owns a inverter sine wave generator for the other 15% when the system isn't enough. Pretty good compromise for what is already owned verse putting a lot of money into another system.


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## WHALENARD (Feb 21, 2010)

I think harnessing lightning is worth a shot. Maybe just a female plug to your battery attached to a long metal pole. 

Sent from my moto g(6) forge using Tapatalk


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## russinthecascades (Jun 1, 2013)

I designed a 400W solar /400Ah battery/ 3000W inverter system in our Sprinter van prior to my wife getting an ebike. I've only tried to charge it 3 times - 2 successfully and once where no charge got to the bike. I'm chalking that one up to user error, but will be sure after we have more experiences. Looking forward to traveling more and not have to rely on shore power.


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## Fuse6F (Jul 5, 2017)

russinthecascades said:


> I designed a 400W solar /400Ah battery/ 3000W inverter system in our Sprinter van prior to my wife getting an ebike. I've only tried to charge it 3 times - 2 successfully and once where no charge got to the bike. I'm chalking that one up to user error, but will be sure after we have more experiences. Looking forward to traveling more and not have to rely on shore power.


Post some pics please


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## russinthecascades (Jun 1, 2013)

2015 Sprinter Cargo 170 extended. Major design feature was bikes storage without removing front wheels. 3 bikes fit behind the battery box and bed installs over the top of the box. I'm hauling fencing supplies so the bed is out right now.


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