Battery recommendation for experimental use

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
Hi,

I'm considering purchasing a fairly high capacity battery for indoor use as a pure DC voltage source. The purpose would be to compare the effects of an unadulterated voltage source to the noise generated by SMPS / mains AC. A 12v lead acid battery comes to mind but I am unsure about it's safety and efficacy for bench use.

1) Which chemistries are ideal for this application?

2) Which voltage / current regulators are available that are free of an AC component or as little as possible?

3) What other means do engineers use to produce a pure DC source for experimenting?

4) Any other considerations to take into account?

Regards,
Mark
 

MrChips

Joined Oct 2, 2009
26,062
You omitted two important criteria.

1) What is the current draw?
2) What is the duration of operation, in other words, what is the capacity in Ah?
 

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
You omitted two important criteria.



1) What is the current draw?

2) What is the duration of operation, in other words, what is the capacity in Ah?


I omitted because those criteria are not nearly as important as safety, I'm skeptical with batteries in general. I anticipate current draw to be 1A max with an average of 100mA and can recharge as needed so a few Ah would be nice. All my experiments are low power.

I realized immediately after I posted that someone would ask about this. Please refrain from grabbing your pitch forks just yet.;)
 

MrAl

Joined Jun 17, 2014
8,972
Hi,

I'm considering purchasing a fairly high capacity battery for indoor use as a pure DC voltage source. The purpose would be to compare the effects of an unadulterated voltage source to the noise generated by SMPS / mains AC. A 12v lead acid battery comes to mind but I am unsure about it's safety and efficacy for bench use.

1) Which chemistries are ideal for this application?

2) Which voltage / current regulators are available that are free of an AC component or as little as possible?

3) What other means do engineers use to produce a pure DC source for experimenting?

4) Any other considerations to take into account?

Regards,
Mark
Li-ion comes to mind as long as you know how to charge it or can get a charger.

A linear regulator puts out the cleanest output in most cases. A switcher would be a little noisy but there are ways to filter the output to a cleaner voltage. There are a lot of single chip linear regulators out there some are constant voltage (like 5v, 12v, etc.) while others are adjustable from maybe 1.2v up to maybe 30 volts.
 

LowQCab

Joined Nov 6, 2012
2,036
Go to Walmart and get a Lawn-Mower-Starter-Battery, ( SLA, Sealed-Lead-Acid ).
To make this Battery last,
it must be kept on a "Maintenance-Charger" when not being actively used.

Here's an example of a Battery-Maintainer ............
.
.
.
2-Amp Battery Charger .png
 

crutschow

Joined Mar 14, 2008
29,755
As LQC recommended, use a sealed-lead-acid battery with a maintenance charger.
It's cheaper and safer than a Li-ion battery.

For a clean, adjustable output use a linear regulator such as the common, bullet-proof LM317, which can be adjusted from a minimum of 1.25V to a maximum of the battery voltage minus about 2V.
It must be on a heat-sink if it has to dissipate more than a watt (dissipation equals output current times the difference between the battery and output voltage).

What are you experimenting with, that you are so concerned about power supply noise?
 

MrAl

Joined Jun 17, 2014
8,972
I omitted because those criteria are not nearly as important as safety, I'm skeptical with batteries in general. I anticipate current draw to be 1A max with an average of 100mA and can recharge as needed so a few Ah would be nice. All my experiments are low power.

I realized immediately after I posted that someone would ask about this. Please refrain from grabbing your pitch forks just yet.;)
You also need to specify the predicted run time.
You see all the lead acid suggestions? That is because they are assuming your run time will be long before you need to charge the battery.
I would use Li-ion over Lead Acid any day if the ampere hour capacity and voltage is not too large.
If the run time has to be very long i might go to lead acid too.
As a side note, they make some really big Li-ion batteries these days but you need a good charger and they are very expensive over about 7 ampere hours.

So it would be good if you specified the intended run time before you can charge again that will also help choose the battery.
 

crutschow

Joined Mar 14, 2008
29,755
I would use Li-ion over Lead Acid any day if the ampere hour capacity and voltage is not too large.
For this application, where size and weight are not a factor, why would you want to use a more expensive and more difficult to charge LI-ion battery?
 

LowQCab

Joined Nov 6, 2012
2,036
2) Which voltage / current regulators are available that are free of an AC component or as little as possible?
.
The "Battery-Maintainer" Circuit that I provided above will produce
an almost immeasurable "Noise-Level".
You might get "some" tiny amount of Noise from the Resistors in the Circuit.

You may not need a Battery at all.

It sounds like You may be asking for a "Bench-Power-Supply".
.
.
.
 

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
Thanks everyone for the replies. The interest in this topic is purely scholastic as I have had no problems that I could attribute directly to signal noise. Realistically I can see from the replies that having a pure DC source is not necessary at my level of application nor do I think my scope is capable of providing the visible distinction to justify the setup. The other half of my interest that I did not mention was having a stable semi-portable power source where I could be sure my calculations begin with as few unknown variables. The local shop always has a few sizes of lead acid batteries sitting out and I figured it would be an interesting learning project for my own charge/discharge circuits as well as the associated calculations as I've read lead-acid batteries are fairly forgiving.

I wasn't going to rush out today for the setup although it's something I thought about building for a few months. I'll probably opt for an expensive bench power supply instead as my setup is hot garbage.
 

dl324

Joined Mar 30, 2015
14,457
Realistically I can see from the replies that having a pure DC source is not necessary at my level of application nor do I think my scope is capable of providing the visible distinction to justify the setup.
I used a power supply from a Heathkit Experimenter and I didn't realize it had more than 300mV of ripple on the supply until I was using it for a circuit where voltages were near the rail and it didn't work correctly. However, it worked for all of the logic circuits I breadboarded with it.

Initially I chalked it up to a shoddy design. When I opened it up to investigate, I found that a cap was bad.
 

MrAl

Joined Jun 17, 2014
8,972
For this application, where size and weight are not a factor, why would you want to use a more expensive and more difficult to charge LI-ion battery?
Sorry, but "difficult to charge"? You're kidding right? Difficult for who, you or me, because it certainly isnt difficult to charge for me maybe because i understand the correct way to charge both chemistries. When i look at the charge method for lead acid i see quite a bit of a pain in the neck because of the different voltage levels but when i look at the charge method for Li-ion i see 'constant' current then constant voltage. They call it 'constant' current because it's one way to describe it, but it's really "current limited" and then constant voltage, but it's also really "voltage limited" too. So we have "current limited" followed by "voltage limited" and then sometimes a minimum current cut off point.
I designed and built different types of chargers both professionally and privately. The lead acid types are the most difficult unless you can put up with doing it by hand and monitoring the process, which isnt idea. The Li-ion charging is very well defined so you can always get it right with a minimum of parts.
Also, lead acid has to be charged every month or so while Li-ion can go for a year or more without being charged. The lead acid self discharge rate is fairly high will with Li-ion is very low.

That's why i prefer Li=ion and i have been using them and charging them for years now, maybe since they first came on the market. If the larger ones were not so expensive i would have those instead of lead acid.
I did go to lead acid though when i realized that one of my portable battery drills was blowing through NiCd's and that the small NiCd's inside the battery pack were too small anyway. The NiCd's were at most 2AH while the small lead acid was 7 or 8 Ampere Hours, quite an improvement. However, if i did not keep an eye on that lead acid battery it would go dead, and a couple did go dead and one is now being used for a door stop (no kidding i'll show a pic if you would like to see, can be a little funny to see).
Of all the Li-ion cells i have ever owned, i think i discarded maybe three of them out of maybe 20 or so, not including the ones in my old cell phone i went through two of those in about 5 years.

One of the emergency lights we have here runs on a small lead acid battery. It has to be constantly charged even though the lights never come on. I examined one of them after a few years of operation, it was completely dry inside even though it was a sealed lead acid. For an Li-ion you might not have to charge it for a year if the lights never get used and that is the usual operation mode.
 

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
Sorry, but "difficult to charge"? You're kidding right? Difficult for who, you or me, because it certainly isnt difficult to charge for me maybe because i understand the correct way to charge both chemistries. When i look at the charge method for lead acid i see quite a bit of a pain in the neck because of the different voltage levels but when i look at the charge method for Li-ion i see 'constant' current then constant voltage. They call it 'constant' current because it's one way to describe it, but it's really "current limited" and then constant voltage, but it's also really "voltage limited" too. So we have "current limited" followed by "voltage limited" and then sometimes a minimum current cut off point.
I designed and built different types of chargers both professionally and privately. The lead acid types are the most difficult unless you can put up with doing it by hand and monitoring the process, which isnt idea. The Li-ion charging is very well defined so you can always get it right with a minimum of parts.
Also, lead acid has to be charged every month or so while Li-ion can go for a year or more without being charged. The lead acid self discharge rate is fairly high will with Li-ion is very low.

That's why i prefer Li=ion and i have been using them and charging them for years now, maybe since they first came on the market. If the larger ones were not so expensive i would have those instead of lead acid.
I did go to lead acid though when i realized that one of my portable battery drills was blowing through NiCd's and that the small NiCd's inside the battery pack were too small anyway. The NiCd's were at most 2AH while the small lead acid was 7 or 8 Ampere Hours, quite an improvement. However, if i did not keep an eye on that lead acid battery it would go dead, and a couple did go dead and one is now being used for a door stop (no kidding i'll show a pic if you would like to see, can be a little funny to see).
Of all the Li-ion cells i have ever owned, i think i discarded maybe three of them out of maybe 20 or so, not including the ones in my old cell phone i went through two of those in about 5 years.

One of the emergency lights we have here runs on a small lead acid battery. It has to be constantly charged even though the lights never come on. I examined one of them after a few years of operation, it was completely dry inside even though it was a sealed lead acid. For an Li-ion you might not have to charge it for a year if the lights never get used and that is the usual operation mode.
Interesting, I was under the impression Li-ion was among the most volatile chemistries. I had a cheaper tablet (RCA) that wouldn't hold a charge very well since day one which had a Li-ion battery. Eventually I got mad and threw it in a drawer to be forgotten for months. One day I pulled it out and the battery pack had ballooned to where it almost burst, I was quite surprised considering it died within 1/2 hour at full charge and it was "dead" when I put it away. That experience has me wary of Li-ion because I treat my personal devices with care and yet that still happened. Of course we have heard the stories of Li-ion blowing up while people are on the phone. Over the years I've played with Ni-Cad, NimH, Li-ion and Lead-acid and the only one that didn't give me trouble (as a consumer) was NimH.
 

dl324

Joined Mar 30, 2015
14,457
That experience has me wary of Li-ion because I treat my personal devices with care and yet that still happened.
That's a wise course of action.

I had two aftermarket Li-ion batteries in my smartphone bulge so much that they lifted the screen. I had one that swelled in my DSLR camera, and it was a pain to get it out. I had a spare for another camera that swelled up before I even had a chance to use it.

That said, I still use Li-ion batteries because of their higher energy density than NiMH. I'm just careful about not abusing them and I use commercial chargers.

Someone gave me a number of 16340's that they used to power a homemade experimenters board. I hacked a magnifier that used 3 AAA batteries to use one. Then I started using 18650's and 18500's in a number of flashlights, instead of the 3 AAA's that they originally used. One flashlight came with a spacer and a longer body to accommodate 18650's or 3 AAA. For others, I use an extender that holds the 18650's centered or I make my own spacers and use 18500's.
 

Jon Chandler

Joined Jun 12, 2008
189
The point of the battery is to have "pure DC." A 12V lead-acid battery provides 12 volts, which can be regulated down with linear regulators to any lower voltage.

If Li-Ion is used, multiple cells must be used to get more than 3.someting volts (adding expense and complications) or a boost regulator must be used, which certainly gets away from the goal of "pure DC."
 

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
The point of the battery is to have "pure DC." A 12V lead-acid battery provides 12 volts, which can be regulated down with linear regulators to any lower voltage.

If Li-Ion is used, multiple cells must be used to get more than 3.someting volts (adding expense and complications) or a boost regulator must be used, which certainly gets away from the goal of "pure DC."
My original idea was indeed to use a 12V Lead-acid with a LM317 since I'm familiar with it's operation. To my knowledge there are no other chemistries that can achieve ~10V without placing multiple cells in series (?). I have designed my own buck and/or boost converters and have calculated the voltage and current ripples to my satisfaction and have achieved 80-90% efficiency. I also have a benchmark buck boost. The "problem" with the SMPS is I cannot see the AC components at the filtered output with my current setup. This is not so much of a problem as a curiosity because I know it's there since my experience with low pass filters is limited plus it's my current understanding that filters act across a gradient and not a specific cut off frequency.

I would like to extend my designs by taking these factors into account. I know I am getting further away from practicality as I delve further into this discussion, none the less it's something I wish to explore.

Please forgive me if I'm going in circles at this point. Unless there is more someone can advise me on I will consider this discussion concluded.

Enjoy your weekend :)
 

MrAl

Joined Jun 17, 2014
8,972
Interesting, I was under the impression Li-ion was among the most volatile chemistries. I had a cheaper tablet (RCA) that wouldn't hold a charge very well since day one which had a Li-ion battery. Eventually I got mad and threw it in a drawer to be forgotten for months. One day I pulled it out and the battery pack had ballooned to where it almost burst, I was quite surprised considering it died within 1/2 hour at full charge and it was "dead" when I put it away. That experience has me wary of Li-ion because I treat my personal devices with care and yet that still happened. Of course we have heard the stories of Li-ion blowing up while people are on the phone. Over the years I've played with Ni-Cad, NimH, Li-ion and Lead-acid and the only one that didn't give me trouble (as a consumer) was NimH.
Hello again,

Very nice reply thanks, i like to hear about personal experiences and how the 'person' assesses the outcomes.

I could tell you horror stores about Li-ion that could easily top those you mentioned which if you took to heart you would run away from every Li-ion battery you ever see from here on out, but i could also tell you stories about Lead Acid that would make you do just about the same, including one where my father was jumping his car one day and the entire battery blew up in his face. Lucky though he was wearing glasses as we found fragments all over the yard.

Now i am a pretty cautious guy but i still use Li-ion extensively. Why is that? I also use Lead Acid. Why is that? After those stories surely i wouldnt want be seen using either of those chemistries, ever.
The answer is that the personal experience statistical sample size is too small to judge and as we expand that to a wider range we see that there are a very low percentage of problems that come up for either chemistry, even though some of those problems were complete and total horror stories, and that lessons learned helped to keep those problems even lower.

So to look at some larger sample sizes:
1. Almost every gas engine car ever made uses a lead acid battery.
2. Almost every Electric Vehicle (EV) uses Li=ion or similar. These have the most potential for serious problems as the batteries are HUGE comprised of many cells.
This tells me, at least for the current day and age, that we can not judge these too quickly and we cant get rid of them at least for now.

Also noteworthy is that most portable power drills are now going to Li-ion that come with special fast chargers. My newest drill charges from low to full in 30 minutes. My older NiCd drill used NiCd's which required 8 hours to charge from low to full with the included charger. That old one is the one i went to Lead Acid with because i got sick of paying 40 bucks for new NiCd cells that only gave me 2 ampere hours of capacity when a 20 dollar (USD) lead acid gave me 7 ampere hours, which of course means a much longer run time.

Overall NiMH is probably the safest if you are worried about that, but the charge scheme has to be done right or the cells life span is greatly reduced. I would never use NiCd again though.

So really there is something to be said about all these chemistries, pros and cons. Ultimately you have to decide for yourself which one you care to deal with the most or the less. For me i use both LA and Li-ion but each for it's fitting application.

Oh one last word on the Li-ion cells. They are not all the same, even the renowned 18650 which i have to highly recommend. The charge rate and maximum discharge rate has to be observed and some cells are made for average discharge rates and some are made for very high discharge rates. The ones i use in my smaller LED flashlights is a regular 18650 with no specifically high ratings, although in my 70 watt high power LED flashlight i have to use the high discharge rate type 18650's because it has high current draw on the highest setting. That light lights up the while back yard :) That brings up another interesting issue. If i had to run that thing on Lead Acid i'd have to carry around a heavy battery and it would take up a lot more room which means the flashlight could not be carried in my back pocket anymore. You can take a look at the energy densities of the two chemistries to find out more about that.

Good luck with whatever you choose.
Oh BTW, i keep a chemical fire extinguisher nearby no matter what chemistry i am using and ALWAYS monitor the charging of any battery i use as it is being charged. As i said earlier, i am one of the most cautious guys you'll even know (ive even seen large electrolytic capacitors blow up like sticks of dynamite bending heavy copper buss bars all because of overvoltage/overcurrent. I still use capacitors though (ha ha). ).
 
Last edited:

Thread Starter

k1ng 1337

Joined Sep 11, 2020
526
Hello again,

Very nice reply thanks, i like to hear about personal experiences and how the 'person' assesses the outcomes.

I could tell you horror stores about Li-ion that could easily top those you mentioned which if you took to heart you would run away from every Li-ion battery you ever see from here on out, but i could also tell you stories about Lead Acid that would make you do just about the same, including one where my father was jumping his car one day and the entire battery blew up in his face. Lucky though he was wearing glasses as we found fragments all over the yard.

Now i am a pretty cautious guy but i still use Li-ion extensively. Why is that? I also use Lead Acid. Why is that? After those stories surely i wouldnt want be seen using either of those chemistries, ever.
The answer is that the personal experience statistical sample size is too small to judge and as we expand that to a wider range we see that there are a very low percentage of problems that come up for either chemistry, even though some of those problems were complete and total horror stories, and that lessons learned helped to keep those problems even lower.

So to look at some larger sample sizes:
1. Almost every gas engine car ever made uses a lead acid battery.
2. Almost every Electric Vehicle (EV) uses Li=ion or similar. These have the most potential for serious problems as the batteries are HUGE comprised of many cells.
This tells me, at least for the current day and age, that we can not judge these too quickly and we cant get rid of them at least for now.

Also noteworthy is that most portable power drills are now going to Li-ion that come with special fast chargers. My newest drill charges from low to full in 30 minutes. My older NiCd drill used NiCd's which required 8 hours to charge from low to full with the included charger. That old one is the one i went to Lead Acid with because i got sick of paying 40 bucks for new NiCd cells that only gave me 2 ampere hours of capacity when a 20 dollar (USD) lead acid gave me 7 ampere hours, which of course means a much longer run time.

Overall NiMH is probably the safest if you are worried about that, but the charge scheme has to be done right or the cells life span is greatly reduced. I would never use NiCd again though.

So really there is something to be said about all these chemistries, pros and cons. Ultimately you have to decide for yourself which one you care to deal with the most or the less. For me i use both LA and Li-ion but each for it's fitting application.

Oh one last word on the Li-ion cells. They are not all the same, even the renowned 18650 which i have to highly recommend. The charge rate and maximum discharge rate has to be observed and some cells are made for average discharge rates and some are made for very high discharge rates. The ones i use in my smaller LED flashlights is a regular 18650 with no specifically high ratings, although in my 70 watt high power LED flashlight i have to use the high discharge rate type 18650's because it has high current draw on the highest setting. That light lights up the while back yard :) That brings up another interesting issue. If i had to run that thing on Lead Acid i'd have to carry around a heavy battery and it would take up a lot more room which means the flashlight could not be carried in my back pocket anymore. You can take a look at the energy densities of the two chemistries to find out more about that.

Good luck with whatever you choose.
Oh BTW, i keep a chemical fire extinguisher nearby no matter what chemistry i am using and ALWAYS monitor the charging of any battery i use as it is being charged. As i said earlier, i am one of the most cautious guys you'll even know (ive even seen large electrolytic capacitors blow up like sticks of dynamite bending heavy copper buss bars all because of overvoltage/overcurrent. I still use capacitors though (ha ha). ).
Despite my concerns I'm a big believer that a person "can't live in fear" as the expression goes and I do have 2 fire extinguishers on hand (one in house and one in vehicle). I also have long term plans for building a rideable electric go-kart with solar recharge capability and given the price points it looks like Lead-acid is a cheaper starting point on several aspects. The take away I'm really getting here is actively monitoring whatever chemistry in a well controlled manner and staying within spec is paramount for my safety. I've seen more than enough YouTube to know many people jump in full of assumptions and in a state of ignorance which is something I've never cared for.
 
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