UPS

[ben999]

Guys

I am planning to use a 4S li-ion 18650 battery.

Please have a look at my Fritzing sketch :)

Battery pack will be monitored by this item :
http://www.ebay.com/itm/4S-6A-Li-ion-Lithium-Batterie-3-7v-18650-Charger-Battery-Protection-Board/382109076738?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

When off-grid ISDN box and RPi will be powered with that battery via this board :
http://www.ebay.com/itm/Automatic-Buck-Boost-Step-Up-Down-DC-DC-Power-Supply-Converter-Replace-XL6009/142371180585?ssPageName=STRK%3AMEBIDX%3AIT&var=441392018812&_trksid=p2057872.m2749.l2649

When on-grid, this charger will charge the battery pack and power ISDN box/Rpi :
http://www.ebay.com/itm/EU-Plug-4S-16-8V-2A-AC-DC-Charger-Adapter-for-18650-Lithium-Li-ion-Battery-Cell-/262728544983?epid=507598255&hash=item3d2bd772d7:g:m6oAAOSwcLxYJaSF

Is this the correct way of building my UPS ?
Can i draw current from the charger to power box and RPi while it is charging ?

Thanks again for your input/advice.

[rozpruwacz]

isn't it better to buy ready made solution ? e.g. http://www.powerwalker.com/index.php?page=select&lang=en&cat=dc

[ben999]

@rozpruwacz

No DIY, no fun ! :wink:

[rozpruwacz]

haha :) yeah, totally agree :P

[gohan]

@ben999 said in UPS:

@rozpruwacz

No DIY, no fun ! :wink:

No DIY, no problems, no fun :smile:

[dbemowsk]

I didn't read all the comments, so forgive me if this was mentioned. What if you just used an SLA or AGM battery and connected a battery tender to it. The battery tender should keep the battery topped off without over charging it, and I would think have enough power to power the PI also. Then you are converting 220 down to 12, and if the power goes down, the battery tender will just shut off and the battery would take over. No extra loss in converting 12 to 220 and back to12 again.

[gohan]

I think nobody wants to convert 12 to 220v

[ben999]

@dbemowsk
Thank you for your message

@gohan said in UPS:

I think nobody wants to convert 12 to 220v

I think @gohan got me right here. I have a spare "standard" ups at home... but i dont find that tech very sexy (on top of it it's huge)

It's fun to scratch head !!!

[ben999]

Guys,

One last question :

Can i draw current from the charger to power box and RPi while it is charging the home-made UPS ?

I might be ordering this in case it is possible:

link text

[gohan]

if the charger is not drawing too much current I'd say yes, but you need a buck converter

[dbemowsk]

@ben999 The highest current draw from the list of Pi models is 2.5A on the model 3B (https://www.raspberrypi.org/help/faqs/#powerReqs). If you have a power supply slightly larger than whatever model you are running, you should be good. you just need to be able to supply enough so that the PI has enough to run whatever it is doing and some for charging.

[dbemowsk]

As I mentioned in my previous post a few days ago, you will want a battery tender, and not just a charger. A battery tender will shut off if the battery is fully charged, whereas just using a battery charger could overcharge the battery.