Portable 12v 2-3A battery

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Old 08-06-18, 11:25 AM
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Portable 12v 2-3A battery

Hey, I need a portable battery that will last for a good number of hours(aiming for 12~), the use of the battery is to power a telescope system, which requires 12v 2-3 amps(what I currently need requires 2 amps, but in case I connect anything else, it would be preferred to have the ability for more)
I thought about a few different ways:

Deep cycle battery, thats probably the best option for me, but its super expensive where I live, so Im currently looking for other options and ideas.

Car battery, which is also a way, but as far as I know car batteries aren't made for being discharged and charged over and over again, which might end the battery very fast and might be a waste of money.

I also thought about buying those jump starter power banks, something with like 12-16 amper, which might be ok to use, but again the 12v of those batteries are to start a car etc, and Im not sure continuous use like that would be healthy and good for the battery.

One more idea I thought of is buying a bunch of 18650 batteries(like 10-20 which should give me a total of around 32-64 amper), then wiring them together(not necessarily all of them at once), adding a 12v regulator, wiring it to 12v 2-3 amps output(Im not really sure how to do it tbh).

What do you guys think? I think a deep cycle battery would probably be the best solution, but its really expensive so maybe there are other solutions I can use, thanks for the help :slight_smile:
 
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Old 08-06-18, 11:37 AM
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Welcome to the forums.

A basic sealed lead acid battery will give you the best bang for the buck. You'll need approx 35AH of power. Not sure what's available to you but just a link as an idea.....
12V-35Ah-Deep-Cycle-Solar-Battery-Also-Replaces-33Ah-34Ah-36Ah/113486747

A motorcycle battery may be an idea too.
Lithium gives you excellent standby time but will require a sophisticated charger to charge multiple cells.
 
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Old 08-06-18, 12:05 PM
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Originally Posted by PJmax View Post
Welcome to the forums.

A basic sealed lead acid battery will give you the best bang for the buck. You'll need approx 35AH of power. Not sure what's available to you but just a link as an idea.....
12V-35Ah-Deep-Cycle-Solar-Battery-Also-Replaces-33Ah-34Ah-36Ah/113486747

A motorcycle battery may be an idea too.
Lithium gives you excellent standby time but will require a sophisticated charger to charge multiple cells.
Thanks for the reply, the thing is deep cycle batteries are really expensive where I live, like 33 ah, is around 100$, which is sucks.
A motorcycle battery is 6v as far as I know isn't it? And regarding charging to lithium batteries, I don't think its really a problem, I can just wire a charger or something like that I guess.
 
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Old 08-06-18, 12:08 PM
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Motorcycle batteries come in 6 and 12v.
 
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Old 08-06-18, 01:15 PM
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Originally Posted by PJmax View Post
Motorcycle batteries come in 6 and 12v.
Well a motorcycle battery is even more expensive with low amps, so its not a good option, what do you think about the 18650/jump starter option?
 
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Old 08-06-18, 01:30 PM
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I use lithium polymer batteries which are used for RC airplanes and helicopters. 3S (three cells) provides about 12 volts and the voltage holds pretty steady throughout the discharge cycle. They are similar to the batteries used in jump start packs but they are available in many different sizes. They are much smaller and lighter than lead batteries but more expensive. Since you are in Israel I don't think you will have temperatures that are too cold for the batteries.

Compared to traditional lead batteries lithium batteries are "fussy" and must be used and charged properly. I would read a little about them to make sure you are willing to work with them.
 
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Old 08-07-18, 04:30 AM
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Originally Posted by Pilot Dane View Post
I use lithium polymer batteries which are used for RC airplanes and helicopters. 3S (three cells) provides about 12 volts and the voltage holds pretty steady throughout the discharge cycle. They are similar to the batteries used in jump start packs but they are available in many different sizes. They are much smaller and lighter than lead batteries but more expensive. Since you are in Israel I don't think you will have temperatures that are too cold for the batteries.

Compared to traditional lead batteries lithium batteries are "fussy" and must be used and charged properly. I would read a little about them to make sure you are willing to work with them.
Lithium polymer batteries are not the same as lithium ion batteries right? The polymer batteries amps seems much lower and more expensive than the li-on batteries, and the li-on batteries should be better than the polymer as far as I've searched, what are the reasons to use polymer? And what difference does it make? Thanks.
 
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Old 08-07-18, 05:54 AM
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You are correct Li-ion are different than LiPo. All modern cell phones and most laptop computers and tables are powered by LiPo batteries. 10 years ago laptops were powered by Li-ion and many cordless tools today use them as well.

LiPo's benefit is their energy density. They are lighter and smaller for the energy they contain. So, you get the most power in the smallest, lightest package with a LiPo.
 
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Old 08-07-18, 06:25 AM
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Originally Posted by Pilot Dane View Post
You are correct Li-ion are different than LiPo. All modern cell phones and most laptop computers and tables are powered by LiPo batteries. 10 years ago laptops were powered by Li-ion and many cordless tools today use them as well.

LiPo's benefit is their energy density. They are lighter and smaller for the energy they contain. So, you get the most power in the smallest, lightest package with a LiPo.
In case I want to make a 12v battery with 18650 batteries, can you guide my a bit with what I need?
I want to make something like 3s-4s battery pack(still not sure because in both I probably lose a lot of power because 3s can't really discharge too low and 4s is usually too high), obviously a protection bms in case of failures and a 12v dc output, regarding input, Im not sure which one would be better, a 12v input is probably the ideal, but maybe like micro usb charging(even tho it will be super slow) will make the batteries last longer. I also want to connect a led/lcd to know how much ampers I have left.
Any suggestions about that?
 
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Old 08-07-18, 09:57 AM
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Most batteries and chargers are very good and don't benefit from slow charging. Pretty much all I know of can handle 1c charging rate and most can do 2c or more without harm to the batteries.

The first thing I would think about is how I will charge the batteries. Simplest is to simply remove the cells and charge them individually or in a charger that will charge more than one cell at a time. Unfortunately it's a hassle to remove the batteries each time to charge.

I always balance charge batteries as a "pack". This requires a charger capable of balance charging and the battery pack must also be wired to accommodate balance charging. There are standard connectors used with lithium batteries that allow easy connection for balance charging.

You also need to look at the 18650 cells you are using. Are they unprotected or does each cell have built in circuitry for over/under voltage protection?
 
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