Portable outlet battery bank?

[edskate]

Hey everyone, So I was out on my electric longboard today, and I run out of power and had to ride it normally back.. no big deal.. wasn't too far away from home, I was wandering if there is a portable battery bank? similar to what you can get to charge mobile's and tablet's, but this would charge the board!

anyone know if such a thing exists?

 

[Ianhill]

Moving stored energy is complex it creates losses and its not as simple as bleeding one pack into another, it needs to be through a charger, there needs to be a capacity difference between them eg. battery a 10000watthour charges battery b 1000watthour, two equal packs one full bleeds into the empty pack only gives two half full packs if theres no dcdc cc cv charger, so it be lighter to carry a spare battery pack charged and a lot faster to swap a battery than charge it specially out on the move.

 

[edskate]

Ohh ok, thanks for explaining that

 

[thepronghorn]

Not exactly sure what you're asking for here, but I had to chime in because the answer isn't a flat no like the 1st reply said.

If you want to charge your longboard's battery from another battery, that's totally possible. One way of doing it would be to have a 12V battery powering your battery charger (that presumably also takes 12V input). However, if you're going to carry around your charger, you might as well just bring your power supply and plug everything into the wall. If you were somewhere without access to a plug, then the 12V battery power supply would be an option.

Another option would be to just have a second pack and swap it onto your board.

If you want something that will charge your pack while allowing you to continue to ride like how you presumably use a cell phone battery bank, the answer is probably just have a swappable packs or a bigger pack so you never run out of charge.

An extension on the first option might be to use a current controlled boost or buck converter as a bulk charger to convert the voltage of your battery bank into the voltage and current needed to charge your main battery pack. You would have to take precautions to make sure your charger knows to cut off charging when the battery bank is depleted.

 

[Grizzl-E]

Hmmm although the answer to this question is no, carry a spare battery.

There actually could be a market for a battery bank like this. Use high ah low discharge 18650's, build in a 5v out and then an adjustable dc-dc converter. 3 amps out of a buck booster isn't that big to fit into a case.

Market is as a battery bank for your devices that can also top up an eboard battery. Bet you someone sells one within 5 years. Likely an overpriced accessory from boosted or similar.


Sent from my iPhone using Tapatalk

 

[Ianhill]

I never said its not possible flat out no, I said it highly impracticable if your carrying a device with enough cappacity to charge your battery it will clearly weigh more than a charged battery alone don't take my word for it.
When ever you step up or down electricity there are heat losses so its inefficient, you could just take charged packs out it would cost less than a mobile charger and weigh less and quick as a swap your back on the road.
It not that it can not be done its just better ways of managing your day and electricity it seems wasteful to me.

 

[edskate]

So what I meant was basically Is there some sort of way I can charge my electric longboard (Lecdec) when I'm out, on the train to work there isn't any plugs to charge my board, and it would be useful if i could some way charge it with out connecting to the mains, I can take my charger and correct a battery to my charger to charge it i just don't know what sort of battery i could use. Swapping batteries isn't an option because the battery is in a inclosure that is sealed to the deck and way to much hassle to take on and off all the time

thanks guys

 

[Ianhill]

OK I get u that would be a pain In the arse if its a enclosed unit and I see your point with out sockets its tough, I would work out your watthour of your board and the chargers voltage and go from there make a pack large enough for your needs my Icharger works from 10v to 18v so 4s pack would work for me then say 12s 8000mah you will need say 4s 24ah for a 80%+ charge from flat I would use the lifepo4 20ah prismatic its light fairly compact pack and over 1000 cycles it would out last the board.
Just thinking surely the board has a BMS and is the charger built in ? so it would need a 230vac supply or 110v would it need an inverter or a hobbie charger it depends on the board charge system

 

[thepronghorn]

Well you did say that "two equal packs one full bleeds into the empty pack only gives two half full packs" which is not correct because you just use a dc-dc converter so that one pack ends up empty and the other ends up about 80-90% full based on efficiencies... Also your battery bank could be built with high energy density cells that would be lighter than your main pack for the same energy because they don't need to discharge as fast. Also lifepo4 is rather big and heavy for its capacity, so I'm not sure if it's the ideal chemistry for the battery bank.

 

[Ianhill]

If I say black you will say white .
Ill stand by the use of lifepo4, why do u need high c ratings for charging or the highest energy dense cell to charge a board when he's on a huge train and plans to keep it in a rucksack. I can understand on the board use less space but charging too.
I'll eat my words when I'm wrong and I have wrote it in a strange fashion so I'll edit it to make sence.

 

[Ianhill]

Better still I have 3 16ah lipos and a icharger so I will do a few tests.

 

[Ianhill]

I done a basic test.
I had 2 identicle 4s 2p 16ah multistar lipos they had been balanced then discharged is series so they were at simular states of charge at 3.70 rest voltage.I then balance charged call it battery A from the mains with an icharger 1010b+ then left it for 3 hours to simulate a rest period then I used the same Icharger i set the input voltage minimum to 14.8v or 3.7v per cell and used battery A to charge battery B here are the results.

Battery A, 3.7v per cell rest, took 2hours 9mins,15750mah to full charge

Battery B 3.7v per cell rest,
At 55mins 8900mah 15.80v the charger started to reduce current to the charging battery below my asked 10ah even though its well below 16.80 so it shouldn't be ramping down yet the input voltage was dropping and the input current climbing as expected due to the output voltage climbing so battery A had warned to ambient temp with 11.5ah be drawn and climbing.
1hr18mins, 11330mah, 16.00v I stopped the test, the input battery voltage had reached 14.80v 3.70v cell the charger had ramped down to 3ah charge and 5ah draw from battery A and still a ambient temp

I can say that if I was charging a 12s pack from a 4s as most of the board users would need then the voltage differences would be more and the heat losses etc would be worse, I have achieved 72% capacity moved from A to B and that is 4s to 4s to hazard a guess I would say you would be lucky to reach 60% with a 4s to 12s configuration.

 

[Ianhill]

well you did say that "two equal packs one full bleeds into the empty pack only gives two half full packs" which is not correct because you just use a dc-dc converter so that one pack ends up empty and the other ends up about 80-90% full based on efficiencies...

have a read of my test 60% at best in most circumstance unless u have a charger that uses the same input voltage as the output voltage needed to minimize losses and then I only achieved 72%.

So for a 12s board you would need a 12s pack with around 50% bigger capacity than the boards and a charger that uses upto 50v to keep losses on all fronts small as possible based on my 4s to 4s test.