# [INFO/Q's] Chargers to keep your N7 at 100% at all times in your car install



## leolulz (Apr 5, 2013)

Hi there!

I've seen alot of questions and confused peoples about what chargers that can keep the N7 charged in their car installs.

I think instead of writing some info in the middle of huge threads we could collect all charger related info/questions in one thread!









I've seen in Timur's ROM thread that some peoples are using something called DCDC-USB charger card(?) Perheps info about how to use it could go in this thread! Would most likely help alot of peoples 

I can start of saying i'm using this charger: http://www.ebay.com/...984.m1439.l2649 and it seems like it can't keep the N7 charged... the N7 is loosing about 1-2% every night and it only charges about 1% every drive i do so slowly the N7 is going to the bottom







And i'm only powering the N7, a USB hub and the Hifimediy Sabre USB-DAC with it.


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## naiku (Feb 24, 2013)

I have a DCDC-USB, typically on my 90 minute drive it charges 5%. It has 2 outputs, I soldered a female USB port onto each, one powers the Nexus, the other powers a USB hub (flash drive, Sabre USB-DAC and Joycon on the hub).

The DCDC-USB has 3 ways of setting it up, Dumb, Automotive, and Scripted. Easiest way to set it up is Dumb mode, you just need to connect 12v power and a ground, and set the jumper to your output (likely you will want 5v). I believe Automotive lets you set up an off timer among other things. No idea on scripted as I have not looked into that.

I did have the same kind of charger that you have, and experienced the exact same thing. It would typically charge 1% or not at all, that's running things like Apollo, and BT. If I throw something like Waze into the mix, forget it,the battery loses faster than it can charge. You won't find anything that keeps the charge overnight, unless you have something wired directly to the battery that remains on even with the ignition switched off.


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## bamaredwingsfan (Jun 9, 2011)

Let me ask a general question about charging. Does this device have a poor rate of charge, or are some Roms an kernels better at taking a charge. I use my nexus 7 as my digital bible for church and I plugged up the device about an hour before leaving the house, an it didn't didn't even get the battery charged enough to power on. I was hoping an hours charge might at least give 15 or 20 percent battery.

Sent from my rOot3d Samsung Galaxy S3


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## leolulz (Apr 5, 2013)

naiku said:


> I have a DCDC-USB, typically on my 90 minute drive it charges 5%. It has 2 outputs, I soldered a female USB port onto each, one powers the Nexus, the other powers a USB hub (flash drive, Sabre USB-DAC and Joycon on the hub).
> 
> The DCDC-USB has 3 ways of setting it up, Dumb, Automotive, and Scripted. Easiest way to set it up is Dumb mode, you just need to connect 12v power and a ground, and set the jumper to your output (likely you will want 5v). I believe Automotive lets you set up an off timer among other things. No idea on scripted as I have not looked into that.
> 
> I did have the same kind of charger that you have, and experienced the exact same thing. It would typically charge 1% or not at all, that's running things like Apollo, and BT. If I throw something like Waze into the mix, forget it,the battery loses faster than it can charge. You won't find anything that keeps the charge overnight, unless you have something wired directly to the battery that remains on even with the ignition switched off.


So for example, if i buy this one: http://www.ebay.com/itm/DC-DC-USB-200-vehicle-desktop-power-converter-DCDC-USB-200-/121111038327?pt=PCA_UPS&hash=item1c32c7c977 What other stuffs do i need to get it connected to the N7?


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## naiku (Feb 24, 2013)

bamaredwingsfan said:


> So for example, if i buy this one: http://www.ebay.com/...=item1c32c7c977 What other stuffs do i need to get it connected to the N7?


Nothing. It comes with everything you need. Actually, you will need a female USB port. The DCDC-USB comes with all the wires you need, on the output side there are 4 wires. 2 x positive, and 2 x ground. Just solder a female USB port to one of those pairs, and plug your Nexus charger into that. You can then use the 2nd pair to provide power to a USB hub. Set the jumpers to 5v, connect your power/ground from the car and done. It's very easy to set up.


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## leolulz (Apr 5, 2013)

naiku said:


> In my experience, it definitely charges kind of slow. But, in an hours charging, on a/c power I am surprised you did not get anything to even turn it on. I would have expected about a 15% charge as well at that point.
> 
> Nothing. It comes with everything you need. Actually, you will need a female USB port. The DCDC-USB comes with all the wires you need, on the output side there are 4 wires. 2 x positive, and 2 x ground. Just solder a female USB port to one of those pairs, and plug your Nexus charger into that. You can then use the 2nd pair to provide power to a USB hub. Set the jumpers to 5v, connect your power/ground from the car and done. It's very easy to set up.


Alright doesn't sound too hard








So no need for the data+ and data- cables then? I guess they only are for data transfer to pc's?

Will order one tonight! My tablet is just going lower and lower from the chinese charger









Also, anyone know where i can order the DCDC-USB with a decently short shipping? I live in sweden.
And at last, is it the DCDC-USB or DCDC-USB 200 you're using?


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## naiku (Feb 24, 2013)

leolulz said:


> Alright doesn't sound too hard
> 
> 
> 
> ...


Yep, its pretty straight forward to wire up. Yellow from the DCDC-USB to Red on your female USB, black to black. Plug in your Nexus and done.

You want the DCDC-USB, not the 200. Here is one on ebay.de, that should not take too long to get to Sweden, certainly a lot less time than one from the US:

http://www.ebay.de/itm/DCDC-USB-Konverter-von-6-34V-auf-5-24V-max-100-Watt-/400225725811?pt=PC_Netzteile&hash=item5d2f4fed73


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## leolulz (Apr 5, 2013)

Tried out http://www.ebay.com/itm/130839213832?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 some more and when the temperatures allows the charger can charge the N7 a little. It's been abit colder here for a few days now so the tablet is back to 74%. Although this is with screen brightness set to almost the lowest. Time to order the DCDC-USB and see if it can keep it up better


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## corywf (Jan 31, 2012)

Interested in this as well. Are there any other alternatives beside the DCDC-USB that people have tried with success?


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## leolulz (Apr 5, 2013)

What kind of enclosure do you with the DCDC-USB have?


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## naiku (Feb 24, 2013)

I just have the metal one that is offered as an enclosure for it. I feel that they should include it in the price, but it's an extra $10-15 or something.


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## Ion (Jun 4, 2013)

I'm surprised the DCDC-USB charge rates aren't faster as I can get 2% every 10 minutes with my less efficient cheaper linear regulator and heat sink but there are a lot of factors impacting charge rates and a system is only as good as the weakest link in the chain. I'm sure there are more factors I'm forgetting right now, but here are a few of the big things I've noticed.

1) Car cigarette lighter adapters don't provide enough current. A two port adapter rated at 2.1A is usually 1A to one port, 1.1 to the other. 3.1A says on the fine print 2.1A to 1 port, 1A to the other I think that may even be a stretch as internal). In order to support fast charging, you're going to want at least 1.8-2A for the N7 alone. I've read about people trying to power the n7 on one port and a fully loaded hub on the other port of a 2A adapter. You need to add up the total current requirements of your N7, USB drives and DAC if you hope to be able to fast charge. For most of us, that will mean a dedicated higher capacity converter will be needed.

2) Keep wire resistance low by using thick wires and keeping them as short as possible. The charging circuit will check the line impedance before deciding the supported rate of charge. Running long lines all over the car will increase wire resistance.

3) Charge rates will vary depending on how far depleted your battery is. At very low charge levels, battery will charge with a trickle at first as per design (safety). The battery will charge the fastest with moderate depletion (assuming ideal conditions) but it will slow for the last part of charge so as to not inadvertently over-charge.

3) Keep battery temperatures low. I've been data logging charge rates under a variety of conditions. Maximum charge rates can't be achieved if battery is allowed to get warm. Once you get too warm you get in to a bit of a pickle. At high temps, charge will immediately be lower, followed by further depletion while using since charge circuit is disabled. Once charging is permitted again temps slightly creep while charging making it harder to maintain a good rate of charge unless you rapidly cool the battery down. Around 19-33C I stay at 100%, or I can pick up 2% every 10 minutes if depleted. 33-35C my charge stays about the same if depleted. In the upper 30s and higher I've noticed it start to drop capacity if I don't bring temps down. It's easy for me to cool my tablet to 19C in less than 10 minutes while driving as my tablet and regulator sits right below the AC vents. I also drilled holes in the interior bottom of my AC ducts. The issue is if my car gets too hot while parked in the sun. My interior temps got up to 54C while I was parked at work until I got a sunshade for my dash. I wasn't charging on my commute home until I started rapid cooling with AC on max, roof on, windows up. The sunshade keeps the temp in the upper 30s while my car is parked now. I only blast the AC when I first get in the car now, then turn down in a few minutes, and I stay topped off.

I've got the Carnetix CNX-P5V with a CPU heat sink for good measure. Even though it's a linear regulator that isn't as efficient as the DCDC-USB, I'm able to stay topped off at 100% or pick up 2% every 10 minutes when being mindful of the factors mentioned above. This is with screen at full brightness, UCA202, USB hub and drive, tethering and USB ROM.

Charging after an over-temp condition where I left car out with top off in the sun (bad idea): Temp is last column.









Example of rapid cool with AC on full blast and two small holes drilled in the bottom of each AC duct: 54->19C in < 10 minutes after sitting in sun at work.









Maintaining 100% with reasonably low temps:









It'd be nice to be able to ditch the battery to no have to worry about these sort of things as much, but this is the reality for now.

Sorry for blurry phone pics.


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## replicant (Jun 25, 2011)

Great write up Ion! I still have my old carnetix powersupply from my carpc days.. May have to dig it out and remember what all it provides. It may work for this type of setup too.


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## leolulz (Apr 5, 2013)

My http://www.ebay.com/itm/170996677409?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 just arrived! It didn't come with a manual so i guess i'll have to search the net of how to configure it and we'll see how it ends by the weekend


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## naiku (Feb 24, 2013)

Nice, make sure you post up how well it is working when you have it figured out. It will be nice to have another option available. Not sure if i posted it in this thread or not, but I re-did the connections on my DCDC-USB and now charge around 20% an hour. My battery is almost always at 100% now.


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## Benjamin99 (Aug 7, 2013)

naiku said:


> You want the DCDC-USB, not the 200.


Whats the reason why the 200 would not work? I purchased the 200 and was about to install and came across this post. I wasnt aware there were 2 options and just purchased this one... It actually looks to me like I could setup 4 usb outputs on this 200 - there are 8 output wires (4 yellow, 4 black).


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## naiku (Feb 24, 2013)

Benjamin99 said:


> Whats the reason why the 200 would not work? I purchased the 200 and was about to install and came across this post. I wasnt aware there were 2 options and just purchased this one... It actually looks to me like I could setup 4 usb outputs on this 200 - there are 8 output wires (4 yellow, 4 black).


As far as I know there is no reason it will not work, I was just letting the previous poster know that he wanted to buy the DCDC-USB as that one was known to work fine, and is cheaper than the 200.


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## Benjamin99 (Aug 7, 2013)

naiku said:


> As far as I know there is no reason it will not work, I was just letting the previous poster know that he wanted to buy the DCDC-USB as that one was known to work fine, and is cheaper than the 200.


Great! I assumed the "not the 200" meant that there was a specific reason why the 200 would not work. Glad to hear there is not one, as I have not found anything else online about it. I'm going to throw mine in tomorrow and see how it goes!


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## xapt3r5 (Aug 29, 2013)

What's with you guys and expensive DC-DC regulator with overpowered current supply? :O

I use 2 of these...










http://www.belkin.com/uk/p/P-F8J051

...In a parallel arrangement, and both my 7 port USB hub and tablet get sufficient current (about 4 A), for at least 4 devices plugged fully drawing 500mA and the tablet charging 1% every 3-4 min, altogether. Why would one need more?

I see a lot of people complaining about cigarette adapters and how they fail to provide enough current. Don't just buy anything, ofc. There's a lot of chinese crap out there. I found out this one has actually good hardware and delivers what it promises, It even states it's appropriate for Ipads.

Don't be fooled into thinking you can easily get away with just one 3,x Amps adapter, or something, while combining a hub. The vast majority of market USB gadgets, adapters and cables aren't ready by design to operate with anything more than 2000mA, making it almost impossible to find one that is really capable. Also, from an electrical efficiency design perspective, it's much better to have more than one adapter so that current load is shared by both regulators, thus preventing from things like overheating. You people should be running two separate sets of solid high grade cables, for connections, rather than throw in clunky Y adapters, extensions and other of sort. Loose connections and thin, stranded (weak) wiring, cause a raise of resistance values, which leads to voltage and current drops inevitably adding even more heat to the circuitry. I recommend the use of at least a 26AWG wire gauge for USB wiring.

If you´re soldering anything, try your best for neat, shiny joints. Things like an appropriate flux and iron power/temp will get you there. Don't get too messy at it or you''ll end up wondering why things aren't working as they should.

Remember, Direct Current is a bitch, and it will surprise slap you in the face. Use clear different colored wires. Always double check your connections!...


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## Mugga (Aug 16, 2013)

Very interesting thread! I also got this power supply: http://www.ebay.de/itm/DCDC-USB-Konverter-von-6-34V-auf-5-24V-max-100-Watt-/400225725811?pt=PC_Netzteile&hash=item5d2f4fed73 in my car setup.

Is it possible to charge the Nexus 7 over y-usb-otg cable and a y-cable for the usb hub? So that I got 2 power inputs, or is this damaging the Nexus together with fast charging?


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