How to run to charge a laptop/anything from bike

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MarkJohnston

10 kW
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Mar 25, 2021
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How can I charge a laptop from my bike? I have a car cigarette lighter transformer which does 12V to 110AC. I can plug in the adapter to that. But I would need a step down for my battery to 12V. It doesn't seem efficient. I can't find a 48 volt transformer. Anybody know a product?
 
endless-sphere.com

Cheap DC-DC converters for over 60v input.

There don't seem to be many dc-dc converters out there that will handle input voltages higher than 60v. Building one from a "Simple Switcher" chip also limits you to under 60v input. I had a few switching power supplies that were pulled out from medical equipment in my office, so I tried...
endless-sphere.com endless-sphere.com
 
marty said:
endless-sphere.com

Cheap DC-DC converters for over 60v input.

There don't seem to be many dc-dc converters out there that will handle input voltages higher than 60v. Building one from a "Simple Switcher" chip also limits you to under 60v input. I had a few switching power supplies that were pulled out from medical equipment in my office, so I tried...
endless-sphere.com endless-sphere.com
Click to expand...
the only problem with that is the adapter takes AC, so I guess I would need to make a special port for charging and output. Also If I wanted to hook a bunch of different appliances that could get complicated. I am pretty sure a microwave only takes AC current. But honestly not even sure if I can run a microwave.
 
A bit of care with terminology. "Transformer" is already used to mean an arrangement of coils which transfers AC current from one coil to another. It may change the voltage and amperage in the process, although there are 1:1 transformers. And it's only AC in and out.

A device that changes DC power to AC is an "Inverter". A device that changes DC input to another DC voltage is a "Converter" of some description.

The actual power input to your laptop is almost certainly not AC power - almost no one does this anymore as it will be heavy and hot (because there must be a Transformer in the laptop to do it). The input to the power brick/supply for the laptop is likely to be AC power, but the brick puts out DC power - that is what it is for. Check on the brick to see what the label says it outputs to the laptop.

The brick is a transformer (to lower the voltage) and then a rectifier to change the AC to DC for the laptop to consume, and probably some guard circuitry as well.

For this reason, a DC-DC step down or up converter will very likely power your laptop and charge it's battery - DC is what the actual laptop is expecting. Match the connector and leave the power brick at home. I have seen laptops and tablets that require voltages from 5V USB up to 20+ volts for operating and charging.

Your last message hints that you want to power other devices as well - yes, some require AC current and perhaps at high amperage. You may find equivalent devices designed to work off DC power - especially in 'camping' or 'RV' catalogs - there is a market for these. DC powered TVs, washing machines, air conditioners, kettles, fans, etc.

You can also run many battery powered tools with DC if you match the required voltage with a DC-DC converter.

And if you search on the phrase '48v inverter 120v' (or '48v inverter 240v' where I live) you will find many Inverters that can produce AC current from a higher DC voltage. Substitute the voltage your battery supplies for the search. Look for one that matches your likely use.
 
Feed laptop adapter with 48V DC. It might work. Read how and why here:
endless-sphere.com

Cheap DC-DC converters for over 60v input.

There don't seem to be many dc-dc converters out there that will handle input voltages higher than 60v. Building one from a "Simple Switcher" chip also limits you to under 60v input. I had a few switching power supplies that were pulled out from medical equipment in my office, so I tried...
endless-sphere.com endless-sphere.com
 
offGridDownUnder said:
A bit of care with terminology. "Transformer" is already used to mean an arrangement of coils which transfers AC current from one coil to another. It may change the voltage and amperage in the process, although there are 1:1 transformers. And it's only AC in and out.

A device that changes DC power to AC is an "Inverter". A device that changes DC input to another DC voltage is a "Converter" of some description.

The actual power input to your laptop is almost certainly not AC power - almost no one does this anymore as it will be heavy and hot (because there must be a Transformer in the laptop to do it). The input to the power brick/supply for the laptop is likely to be AC power, but the brick puts out DC power - that is what it is for. Check on the brick to see what the label says it outputs to the laptop.

The brick is a transformer (to lower the voltage) and then a rectifier to change the AC to DC for the laptop to consume, and probably some guard circuitry as well.

For this reason, a DC-DC step down or up converter will very likely power your laptop and charge it's battery - DC is what the actual laptop is expecting. Match the connector and leave the power brick at home. I have seen laptops and tablets that require voltages from 5V USB up to 20+ volts for operating and charging.

Your last message hints that you want to power other devices as well - yes, some require AC current and perhaps at high amperage. You may find equivalent devices designed to work off DC power - especially in 'camping' or 'RV' catalogs - there is a market for these. DC powered TVs, washing machines, air conditioners, kettles, fans, etc.

You can also run many battery powered tools with DC if you match the required voltage with a DC-DC converter.

And if you search on the phrase '48v inverter 120v' (or '48v inverter 240v' where I live) you will find many Inverters that can produce AC current from a higher DC voltage. Substitute the voltage your battery supplies for the search. Look for one that matches your likely use.
Click to expand...
For example. I have a 48v powerwall home system. From there, I use a 48vdc to 12vdc step-down converter. There are lots of different kinds, grouped by power rating. From the 12v output of the converter, I spliced in my laptop charging cord (among several other things); red to red, black to black. The laptop regulates its own current, in my case. So, I just give it a 12v power source, and it charges.

Your laptop may not regulate its own current, you'll have to be sure before you try that. But likely, it does. The "bricks" that come with laptops do exactly what @offGridDownUnder say they do, take 120vac and turn it to 12vdc. They also have a max power rating, ie, 50w charger, 90w charger, ect. You'll just need to find a DC/DC converter that can provide more wattage than whatever your laptop needs to charge, which is likely less than 100w (mine just uses 20w or less).
 
Diggs said:
All laptop chargers change it to 19 volts......
Click to expand...
Well, I have older Thinkpads and a Sony (still working) that reduce to 16V, my Chromebook takes USB input and will charge on 5V (not run - it has a 'smart' power brick that switches to the 20V USB standard but still accepts a charge from low power adapters).

Manufacturers do whatever they want, so check the label on the machine you wish to power.
 
Apple could be a bit different and I'm sorry if you have an Apple product or a glorified phone (Chromebook). I fix computers for a living and have 27 chargers (just counted) in a box from all different Windows laptops. They are all 18.5 or 19 volts. Just saying......
 
Not disputing that officially recognized chargers of both Mac and Windows use 14-20 volts on the DC side. However, depending on the computer, many of them will still accept a lower voltage. My tablet is a Microsoft Surface, the charger outputs 19v. And yet, when I give it 12v, it still chargers. My wife's Macbook is a big ol 18v 80w charger. But when I give it a 5Vdc USB-C plug, it charges. Slowly, yes, But is does still accept a charge at a lower-than-standard voltage.

biphaeboh said:
Okay, I just looked at the power adapter on my macbook, and it says.. input 100-240 V 0.75A 50-60 Hz
Output 20V 1.5A or 15V 2A or 9V 3A or 5V 3A.
That small print is hard to read.
Click to expand...

Again, I don't recommend trying on your individual computer unless you're sure. But most laptops will accept a wider voltage range than what their charger says they accept.
 
General answers to a general question. Mark Johnson help us out what exact battery are you talking about ?
As there could be other solutions to your problem.
 
Haven't read all the above comments properly but OP if you're asking how to charge devices very simply and cheaply from your existing battery, for what it's worth I've used all manner of AC chargers (e.g. Usb phone chargers, at least one apple power supply, cheap generic 240v 12v output power supply off eBay) by running them straight off my 52v (14s) AEG battery. Modern switch mode supplies will accept a much lower voltage range than they specify and still maintain output voltage. I suspect you could have issues with the supply if you tried to draw it's full output current for long periods as the total input power has to remain proportionate to the output, which means higher input current at lower voltages, but as I've said I have used a number of 240vac supplies at 52v with zero issues.
 
Bush mechanic said:
Haven't read all the above comments properly but OP if you're asking how to charge devices very simply and cheaply from your existing battery, for what it's worth I've used all manner of AC chargers (e.g. Usb phone chargers, at least one apple power supply, cheap generic 240v 12v output power supply off eBay) by running them straight off my 52v (14s) AEG battery. Modern switch mode supplies will accept a much lower voltage range than they specify and still maintain output voltage. I suspect you could have issues with the supply if you tried to draw it's full output current for long periods as the total input power has to remain proportionate to the output, which means higher input current at lower voltages, but as I've said I have used a number of 240vac supplies at 52v with zero issues.
Click to expand...
That is what I was trying to explain.
marty said:
Feed laptop adapter with 48V DC. It might work. Read how and why here:
endless-sphere.com

Cheap DC-DC converters for over 60v input.

There don't seem to be many dc-dc converters out there that will handle input voltages higher than 60v. Building one from a "Simple Switcher" chip also limits you to under 60v input. I had a few switching power supplies that were pulled out from medical equipment in my office, so I tried...
endless-sphere.com endless-sphere.com
Click to expand...
 
Yes, just had a look at the link. I'd personally just give it a try with something expendable like a phone charger...I couldn't say exactly what voltage I've actually run mine down to, probably close to 50v, and if that was what others found to be the cutoff point then 48v could be borderline, but I'd just try it out.
 
Hmm ok just tried this out, 47.8v resting battery powers up a small phone charger but only delivers 0.1w plugged into my metered power bank. 52v battery @55v delivers 5.7w, same as when plugged into the mains.

Dc-dc converter is an option, but this thing looks like it ticks all the boxes

www.coolgear.com

ChargeIT! Mini 82W USB Type-C PD Charger PCBA w/ 24~48V DC Input

This High Power Single Port USB Type-C charging board that complies with the latest USB-C and PD standards. Intended for use in PC power adapters, mobile chargers, car chargers and power bank applications. This charging board provides one 82W USB Type-C PD port. USB Type-C PD with PD 3.0...
www.coolgear.com www.coolgear.com
 
marty said:
Bush mechanic said:
Hmm ok just tried this out, 47.8v resting battery powers up a small phone charger but only delivers 0.1w plugged into my metered power bank. 52v battery @55v delivers 5.7w, same as when plugged into the mains.

Dc-dc converter is an option, but this thing looks like it ticks all the boxes

www.coolgear.com

ChargeIT! Mini 82W USB Type-C PD Charger PCBA w/ 24~48V DC Input

This High Power Single Port USB Type-C charging board that complies with the latest USB-C and PD standards. Intended for use in PC power adapters, mobile chargers, car chargers and power bank applications. This charging board provides one 82W USB Type-C PD port. USB Type-C PD with PD 3.0...
www.coolgear.com www.coolgear.com
Click to expand...
Ok seems best to just a variable step down DC to DC buck down converter. I bought this for another project, will buy another if you guys green light it for this. I will need to match the male DC adapter for the laptop though. That's goings to be tricky. The cabling will be the tricky part.
Click to expand...

www.ebay.com

DC-DC 72V 60V 48V Volt Voltage to 12V Step down Voltage Reducer Regulator 180W 1 313034885865 | eBay

Find many great new & used options and get the best deals for DC-DC 72V 60V 48V Volt Voltage to 12V Step down Voltage Reducer Regulator 180W 1 at the best online prices at eBay! Free shipping for many products!
www.ebay.com


I also have a 12V Dc to 120v Ac converter with ports for a regular 120 volt household adapter. Its for s car to plug into the cigarette lighter Could I use the above to buck down the voltage to 12VDC then convert to 120 V AC?

OR DO YOU guys know a hack perhaps I can just hook up 54 volt DC TO THE 12V Dc to 120 V AC converter? That would be nice and save me a chunk of change.
 
Mark, stepping down to 12v, then up to 120, then back down to 20v is a bit untidy (and you're incurring a lot of electrical losses which will make itself felt pretty quickly from an ebike battery). Can you just confirm when you say 'hook up 54 volt ' what are your actual battery specifications? Because of you can maintain >50v I'd say you can just use the straight to adapter method.
 
Bush mechanic said:
Because of you can maintain >50v I'd say you can just use the straight to adapter method.
Click to expand...
Yes BM, I can. Several batteries parralel all > 50 V. SO I can hook up the adapter straight in? I guess I can buy a DC to DC microwave, I need a new microwave anyways. Though... I do have really nice AC Toaster and toaster oven
 
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