Faraday Auxiliary Battery Pack do it yourself

Hello everyone,

I am new to the forum and one of my friends recently built a electric Surley "Big dummE" with the help of this forum. I was going to buy the auxiliary battery pack (https://adventureelectric.bike/faraday-accessories/) directly from Faraday when they announced that they were going to start to sell them. Unfortunately they went out of business. I wanted to know if anyone one could help me recreate what they were going to bring to market.

Here is what they described tabout how the auxiliary battery pack would work:

We’ve been told that once someone rides a Faraday, they want to ride it everywhere they go. So we’re creating an auxiliary battery pack that can double your range to over 40 miles – freeing you to take your Faraday wherever you want without worry of running out of juice.

This stylish, lightweight, detachable pack will also let you charge your battery without having to get your bike near an outlet. And all you have to do is plug it into the existing charge port on your bike, and the bike knows to start using both batteries. Just plug the Auxiliary Battery Pack into the charge port on your bike and your bike will start to use both batteries (the built-in battery and Auxiliary Battery) as if they’re one. (Coming Soon)

Any help would be greatly appreciated!!

Cheers,
Sean

ProperPint said:

I was going to buy the auxiliary battery pack (https://adventureelectric.bike/faraday-accessories/) directly from Faraday when they announced that they were going to start to sell them. Unfortunately they went out of business.

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You were going to buy the auxiliary battery pack for what bike? What bike do you have?

I have the Faraday Portuer but I believe all of there frames run the exact same battery/controller/motor.

Alright. You want to make your own aux battery for your Faraday?

To paraphrase the kick starter claim ... The Faraday aux pack plugs into the exiting Faraday bike via the charge port. It can charge the bike battery. If the bike is running, then it can help power the bike.

The above requirements are really difficult to pull off. Consider a fully charged aux battery connected to a half charged bike pack. Bad stuff happens if you connect two batteries that are far apart in voltage, This concept of an idiot proof aux pack sounds great, but it's a complicated design. Did they ever make one? I wouldn't advise it.

Basically in order for this to work safely under "any" conditions, the "Auxiliary battery pack" (ABP) would have to be a portable battery-powered battery charger, not just a simple battery.

So the actual battery inside the ABP could be any voltage or capacity that gives you the extra total capacity you want, after allowing for the losses in the conversion/charging circuit (up to 20-30%, more or less, depending on what you use, etc).

The circuit that goes between the battery inside the ABP can be any kind of DC-DC converter that has current limiting. The limit needs to be set to or below the maximum charging current allowed for the existing main bike battery, to prevent damage to it or it's wiring. If you don't have specs on it, the safest limit is just to make it the same as the plug-in charger.

If the bike doesn't use power faster than the charging happens, then it really will be just like having a bigger battery.

If the bike uses power faster than the charging happens, then the bike's battery will last longer than usual, but won't quite be like the above.


If you use a high voltage (120V+) battery in the ABP, you could use something like the Meanwell LED PSUs as the converter/limiter. Some versions (HLG, etc) are potted and sealed, so they would work well built into a bike or battery pack. They are also AC input, so you could have a switch on the ABP and a power cord socket, and *also* use that same unit to charge from while out and about.

The disadvantage of this setup is you need a separate charger for the ABP, as it won't charge off your original Faraday charger. That *can* be done, if you use another DC-DC on the ABP's charge input port, that converts the Faraday charger's input to the high voltage the ABP battery needs.

Or...a switch in the ABP to convert (cut in half and hten parallel the halves) the ABP battery to the same voltage the Faraday charger is intended for. Then switch back to run the ABP on the bike.

Your bike probably uses a 36v 250w Bafang geared hub motor, so battery is probably 10s, although they describe it as 43v so verify it. The charger is probably 2 amp. If I was building this, would probably try to use an off-the-shelf low wattage 36v battery pack with a 20 amp dc circuit breaker in series. Probably best to charge up both batteries to same voltage before connecting. Notice all the times I used "probably" and realize that lithium batteries are very dangerous. Also, you can easily destroy everything electrical on your bike by doing this. Good luck!

Did you ever make any progress on running a second battery for the Faraday? I've got two of those bikes on the way and am looking for a way to add range.

freewaypigeon said:

Did you ever make any progress on running a second battery for the Faraday? I've got two of those bikes on the way and am looking for a way to add range.

Click to expand...

The above discussion involves using one battery to charge the other while riding. All your really need to do is either carry a second battery as a spare, or hook it up in parallel.

To do the parallel, discipline yourself to only connect them when they're at the same voltage. Make a simple harness to connect your spare.

I do this with some smaller packs I own. It seems I get more range with two in parallel than running them separately. You can only parallel packs with the some battery chemistry. Don't mix lead-acid and lithium. Dont mix LiFePO4 and LiPo.

Thanks doc! I'll start looking into it now.

We have a Faraday bike and I found this thread looking to see if anyone else has attempted this.

The way the Faraday external pack was supposed to work is to plug into the power jack on the back of the bike. The bike has an integrated charger so the input power just comes from a standard 51 VDC / 2 Amp power supply. If you follow this route there is no need to worry about balancing the external pack with the internal one. You just need your pack to provide approximately 51 V and the internal charger will take care of stepping this down to the pack voltage.

What I don't know is the allowed input range input voltage range is. A 13S Li-ion pack would provide approximately 53-54 V when full, but only about 43 volts at the end of its discharge. If the built-in charger circuit has a low-voltage cutoff at say 46 V you will not be able to use the full capacity. If that is the case, you might have to use a 14S pack or find a suitable boost converter that can produce a steady 51V. I plan to use a bench power supply to measure the minimum voltage where it starts charging, but would be interested if anyone else had tried this.

Another wrinkle is that the Faraday provided power adapter only supplies about 100 watts. Presumably that means that the integrated charger should only ever draw 100 watts or less. This is not enough to run the bike. So I don't know if the bike was designed with a high current mode where it could detect whether an external battery vs. charger is connected and change the power draw or if they were just counting on splitting the load 50/50 between the external and internal pack. Perhaps this is why the apparently simple external pack never made it into production -- maybe the bike's internal electronics were not really up to the job.

Update: partial success.

I was worried that the bike would not operate while charging which would make connecting an external battery pack via the charge port ineffective. A quick test confirmed this.

The charge port on the Faraday bikes is a male XLR connector (similar to what is used by pro microphones). On the power supply, pin 1 is +51 VDC, pins 2 and 3 are both 0 VDC. I confirmed with a multimeter that pins 2 and 3 are shorted together inside the power supply. On the bike, all three pins are high impedance to each other. This makes me think that one of the pins is being used not for power but to signal the bike that it is charging.

I made a small XLR to XLR straight through cable with 3 loose wires to go between the power supply and the bike, then use a DC clamp ammeter to check the current flow on each wire. Pin 1 was carrying +25 mA (the internal battery was fully charged), pin 2 was carrying -25 mA, and pin 3 (the "center" pin of the XLR) was carrying 0 mA. So I cut pin 3 of my makeshift adapter and it dropped out of charge mode. Pin 3 on the bicycle side floated up to +3.3 V -- a sure sign that it was being used as some digital input to the charge controller. The bike was drawing some current from the power supply, but only a few milliamps. Since the battery is fully charged, I can't tell if the reason for the low current draw is because it doesn't need the power or if the charge controller is just completely shut down.

So I loaded a small computer UPS into the bike basket. Plugged the power supply into the UPS with a kill-a-watt power meter, and used my XLR-XLR adapter with pin 3 now disconnected and went for a ride around the block. When I pedal and the assist kicks in, the kill-a-watt meter reads power draw! Up to about 85 watts. So it is officially drawing power from an external battery, in this case the UPS. However, as I suspected, it seems limited to less than the 100 watt rating of the provided power supply used for charging.

85 watts (minus the power supply losses) is not enough to run the motor, which is a 250/350W unit. So it will be draining the internal battery while operating at all but the lowest power. Once the internal battery is dead the bikes available power will be greatly diminished. This could still be OK in some cases: the single trip range should be increased 30-50% at 350 W or 250 W continuous. Any stops will extend the range and give the internal battery a chance to recharge. But this isn't really what I am looking for -- I want it to be able to run nearly 100% of the external pack without worrying about cooldown periods.

So I am going to keep experimenting to see if I can get it to draw more current from the external supply. I also need to investigate what it does with a variable voltage source like a battery rather than the regulated 51V of the provided power supply and what it does when the internal battery is not full.

perhaps a bit off topic but does anybody know what cells faraday uses in their packs any pictures.

Thanks,
K

Did anyone find a cure to the auxiliary Faraday battery? I was wondering if this would work..

https://www.amazon.com/Jeefull-Lithium-Electric-Protection-48V20AH50Amp/dp/B08D32W3PN/ref=mp_s_a_1_2_sspa?dchild=1&keywords=bafang%2Bmotor%2Bbattery&qid=1619471504&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzSEs2RkcyOFNCMDZEJmVuY3J5cHRlZElkPUEwODU5MTU0M0ZTSEFNUzFMV1VDRSZlbmNyeXB0ZWRBZElkPUEwMzg5Mzg2Mk1RSkhZOUZaNFNTMSZ3aWRnZXROYW1lPXNwX3Bob25lX3NlYXJjaF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1

It would be nice to know if any has made further progress.

Hi,

I fixed a Faraday this way:

https://bikefleetnews.blogspot.com/2021/12/faraday-porteur-s-e-bike-resurrection.html

Having issues now with the Amazon sourced pack cutting OUT at 48volts, not sure if the Faraday
could be shorting it out in vengence...

-T