Battery power supplies for the Regen

[zilch0md]

Hi Cornan,

 

After some searching I have found a suitable battery pack for USB Regen for USD39,95 Lithium Ion Battery 7.4V 4400mAh

 

[ATTACH=CONFIG]26593[/ATTACH]

 

If you add this T-connector male to DC5.5/2.1mm DC plug for USD3,90 Male Dean (T-connector) to male 2.1mmx5.5mm DC barrel plug cable:Tools & Accessories,Cables - FPV Model: RC Plane, Multicopter, Quadcopter, FPV Goggles, FPV System and all things FPV.

 

[ATTACH=CONFIG]26594[/ATTACH]

 

you should have a pretty good & valuable battery pack for the USB Regen without soldering skills or the hassle of buying from China!

 

There's a potential problem with the PCM-equipped 7.4V battery pack linked, above. On the specifications page, it indicates that the built-in PCM (Protection Circuit Module) has a discharge cutoff voltage of 5.5V. That's obviously not the cut-off voltage for individual cells, as they will measure 4.2V when fully charged, so it's the cut-off voltage for the entire pack.

 

Problem: This is a 2S2P pack, so if the PCM is not going to stop the pack from discharging into a load until the sum of two cells in series is 5.5V, each cell could fall to an average of 2.75V per cell.

 

If a user allows this to happen, by nature of trusting the PCM instead of monitoring the voltage on his own to stop using the pack when it reaches 6.6V (3.3V per cell), having discharged from a maximum voltage of 8.4V (4.2V per cell), individual cells could go into phase reversal, suffering permanent damage, with the possibility of spontaneous combustion (not necessarily an explosion), but a fire just the same, with toxic soot getting spread about. Call a hazmat crew after you put out the fire. :-)

 

Ironically, at the top of main page for that same battery pack, the following warning is given:

 

 

Before you use or charge this battery you must read the Lithium Battery Saftety Instructions and Warnings document.

1. Do not charge or use batteries if the battery ...
   


1. is punctured or damaged
   
2. is bloated, expanded, swelling or otherwise deformed
   
3. has any cell with a voltage of 3.3v. This means less than 6.6v for a 2-cell/7.4v battery
   

 

[*]Do not charge batteries unattended. Monitor batteries during charging for popping, hissing, smoke, sparks or fire. Also monitor the battery for any swelling or other deformities. Disconnect the battery from your charger immediately.

[*]Do not charge batteries near flammable material. Charge batteries in a fireproof container. Do not charge batteries while they are in your robot

 

Do you see the disparity? They smartly warn us not to allow any one cell to drop below 3.3V - which is pretty much a standard warning for all LiPo batteries, although some people will say that 3.0V is the absolutely lowest you can go - and yet, going by the specifications, they contradict themselves by using a PCM that will allow a two-cell series voltage to fall to 5.5V (2.75V per cell) before it will shutdown.

 

I ruined a $100 6S LiPo pack once, by pushing the discharge all the way down to 3.0V per cell on each discharge cycle - and I was monitoring individual cell voltages during use, with an audible alarm that was set to go off if any one cell hit 3.0. The battery had only been cycled perhaps 7 or times, when a cell that had repeatedly reached 3.0V ahead of its siblings, decided to stop taking a charge. The pack started swelling when I put it on the charger. That was the end of that pack. So now, I stick to a 3.3V minimum per cell, religiously.

 

Unfortunately, the pack pictured above can't be monitored on a cell by cell basis, because it's not wired for a balanced charger. Both of its connectors use two-conductor connectors. A load only needs two conductors, of course, but the pictured "dumb" charger will charge each of the two banks of series-wired cells, together as a unit, not independently as a balanced charger would. So, there's yet another weakness built-in to this battery pack. Over time, in either one half of the pack or the other or in both halves, one cell in a series pair, could begin to exhibit a higher resistance to the charge current, such that by the time the two cells, together as a unit, reach the PCM-governed charge cut-off voltage of 8.4V, the stronger cell can actually be forced to exceed the safe maximum of 4.2V per cell - you'll be cooking that cell - while the weaker cell in a series pair is left behind at something less than 4.2V per cell.

 

Then, during repeated discharge/charge cycles, a snowball effect can take place, as the weaker cell is always sucked down to a lower voltage than its stronger sibling, leaving it all the more vulnerable to suffering damage from going below 3.3V while the other cell is still putting out something greater than that. (And that would be worse if you and/or the PCM allow the total voltage of the 2S pack to drop down to 5.5V before shutting it down.)

 

The fact that this battery pack is not wired for balanced charging is only compounded by the fact that its PCM allows the voltage of the pack as a whole to drop down to 5.5V. The two "oversights" will work together to shorten the useful life of the battery. Assuming the manufacturer actually knows what they're doing and that there are no errors in the published specifications, I would have to conclude that this pack is designed to fail after only a couple of dozen charge cycles - so that you'll toss it and buy another.

 

A battery pack wired for balance charging will have a two-conductor cable for discharging into a load, just like this battery pack, but it will have a JST connector for charging - similar to a small Molex connector, that has one conductor for each cell in the pack, plus a common ground wire. PCMs do not balance charge a pack internally, so the only way to keep the cells nicely matched throughout many usage cycles (500+), is to buy a balance charger and a battery pack that's made for balance charging.

 

That same vendor sells this 7.4V 4500 mAH 2S1P LiPo pack that's wired for balance charging (or monitoring the voltages of each cell during discharge through the separate two-conductor cable):

 



Tiger 7.4V 4500 MAH 30C LiPo Battery with T Plug

 

 

This photo shows a close-up of its JST connector - used for charging:

 



 

Three wires, not two - allowing each cell to be charged or monitored independently.

 

Here's an affordable ($16) balance charger for that pack:

 



Balance Charger for 7.4-11.1V 2-3S Cell Li-Po Battery

 

And here's a LiPo voltage alarm that I've used for several years (to monitor the aforementioned 6S packs I use to power a 24V TBI Millinea MG3 speaker amp for near-field monitors):

 



1-8S LiPo Battery Voltage Tester/Monitor

 

Just press the JST connector of a 7.4V, 2S pack onto the first three pins and it will start cycling through the cells to show the voltage of each, then the total voltage of the pack. In my experience, this alarm doesn't put any noise at all into your audio signal. (Which begs the question: How silent is a PCM that's equipped with a current-limiter?) You could leave it disconnected during play, re-attaching it occasionally throughout the discharge cycle, but that kind of defeats the purpose. Another feature of this alarm is that there's a little button which allows you to adjust the per-cell voltage at which it will alarm. I use do have mine set at 3.0V, but now I leave it at 3.3V. By the way, those little tweeter horns are ear-splittingly loud. They can be heard from the ground when mounted inside an airborne RC airplane or helicopter. I stuffed mine with some Play-Doh - I can still hear them when listening to music. :-)

 

Speaking of current limiting, this balance-wired battery pack, as with most of its kind, has no PCM and thus, has no current limiter. The specifications page for this battery says it has a maximum continuous discharge rating of 30C. A "C" rating can be converted to Amps (not milliamps) by dividing the pack's mAH rating by 1000, then multiply by the C rating.

 

So, for this 4500 mAh pack, with a 30C rating, we get (4500 / 1000) * 30 = 135 Amps. No kidding! This LiPo pack can deliver a continuous current of 135 Amps, without overheating, until it is fully discharged (3.3V per cell), in roughly 2 minutes flat.) That's why they are used by RC racing hobbyists. (Don't short the wires!)

 

Do we need a current limiter for use with DC audio gear? Without naming names, I've been told by three different manufacturers that their DC-powered audio gear will not pull more current than it can use and that it's safe to use my RC LiPo batteries without a current limiter, but one of them joked that any dust bunnies that might fall across exposed power terminals could cause a momentary arc. Arcs across clean air require much higher voltages, even for short distances. :-)

 

I've used unlimited LiPo packs with multiple pieces of audio gear for several years - never having any problem related to their ability to dump a lot of current. But if you want to shop for larger capacity 7.4V LiPo packs that are wired for a balance charger, I would try to stick with 15C, 20C, 25C, or 30C. The really big packs can go as high as 65C.

 

Here's a brand of LiPo pack I like: GensAceUSA - High Performance LiPoly (Lithium Polymer) Batteries for RC Cars, Helicopters, Planes, Boats, Trucks, Crawlers

 

Mike

[zilch0md]

Wow Mike, you ARE a battery geek!

 

And all those hazards and precautions--you just explained to everyone why I dislike batteries so much.

 

To each his own. Or, Live and Let Discharge…

 

LOL

 

I hear you. LiPo batteries can be dangerous when abused and, at the very least, a little inconvenient to properly maintain, depending on the charging and monitoring equipment you are using. Still, with a balance charger and an alarm, the actual effort required is minimal.

 

When the alarm goes off (as a cell reaches 3.3V), you swap the pack for one that's fully charged, putting the first one on the balance charger, having moved the alarm to the fresh battery. When not playing music, unplug the alarm from the active pack so that it doesn't slowly drain the pack (or sound off in the middle of the night.) That's it. Not so bad.

 

The toughest part is just selecting the right pack for the load - keeping in mind that the voltage can be as high as 4.2V per cell that is in series and that the pack must not be used once the voltage gets down to 3.3V per cell.

 

Given that these packs have no (noise-making) voltage regulators on their outputs, your appliance must be able to operate at both extremes of these voltage ranges (when setting an alarm to discontinue use at 3.3V per cell):

 

1S1P, 1S2P, 1S3P, etc., nominally rated and sold as 3.7V: 3.3V to 4.2V

 

2S1P, 2S2P, 2S3P, etc., nominally rated and sold as 7.4V: 6.6V to 8.4V

 

3S1P, 3S2P, 3S3P, etc., nominally rated and sold as 11.1V: 9.9V to 12.6V

 

4S1P, 4S2P, 4S3P, etc., nominally rated and sold as 14.8V: 13.2V to 16.8V

 

5S1P, 5S2P, 5S3P, etc., nominally rated and sold as 18.5V: 15.5V to 21.0V

 

6S1P, 6S2P, 6S3P, etc., nominally rated and sold as 22.2V: 19.8V to 25.2V

 

7S1P, 7S2P, 7S3P, etc., nominally rated and sold as 25.9V: 23.1V to 29.4V

 

 

If the bottom end of the voltage range is too low for your device, you can always set the monitoring alarm for a higher voltage, but looking at this typical discharge curve, you will lose a lot of play time if you set the alarm for a voltage any higher than about 3.6V per cell. This curve also reveals that you don't gain a lot of play time by setting the alarm at 3.0V instead of at the safer threshold of 3.3V.

 

 

Source: batteries - LiPoly Battery - When to stop draining? - Electrical Engineering Stack Exchange

 

If your device demands a fixed, regulated voltage, you can connect a battery pack with a range that fits the desired voltage, then supply the pack with an LPS that's regulated at the desired voltage for your device - a la JKenney and his Ciúnas DAC or the French-made Audiophonics PCM5102 DAC. Both of these DACs rely on internal LiPo batteries to filter noise coming from the regulated LPS. (I'm not so sure about that, but it might hold some merit.) The trick here is to select a battery pack where the desired voltage for your device (as regulated by the constantly connected, trickle-charging LPS), is as close as possible to 3.8V per cell - for the sake of the battery's longevity. (3.8V is the ideal long-term storage voltage of a LiPo cell.)

 

Mike

[zilch0md]

AFAIK, Jkenney uses LiFePo4 batteries - a whole different ball game than LiPo batteries - no fire risk, very flat discharge curve (remains nominally at 3.3V throughout discharge) & are constantly trickle charged at 3.3V?

 

Oh, that's right, but the concept is the same as I described - putting a battery pack between a trickle-charging LPS and your load to filter the LPS noise (if indeed this is effective).

 

But, yes, LiFePO4 batteries are more stable, "quieter" for audio purposes (or so I've read) and they do have a 3.3V nominal rating, instead of 3.7 for LiPo.

 

Here's a typical LiFePO4 18650 cell discharge curve.

(Note that not all 18650 cells use LiFePO4 chemistry):

 

[ATTACH=CONFIG]26778[/ATTACH]

 

Source: LiFePower4 -1100mAh - 18650 size - RC Groups

 

Better still, you can find LiFePO4 cells that are individually protected against excessive discharge. They are available in sizes other than 18650, too.

 

Mike

[zilch0md]

Having deluged this thread with perhaps too much information about the care and maintenance of batteries, and despite my comfort with using LiPo batteries, I've been pursuing mmerrill99's suggestion of using LiFePO4 batteries instead.

 

I've spent several hours looking for a convenient 6.4V LiFePO4 battery pack, where the individual cells in the series-wired pack are not simply protected, together as a unit, from excessive charge or discharge voltages, but are also kept in a balanced state, while charging with a simple, semi-intelligent, two-wire charger - again, with the understanding that balance charging can greatly extend the service life of the pack by avoiding the situation where one weak cell gets weaker still, eventually spoiling the entire pack.

 

There are lots of LiFePO4 packs that have built-in protection circuits, but very few of them include balance charging modules inside the pack itself.

 

This 6.4V 4500mAH LiFePO4 pack by Tenergy, a company that has a great reputation in the battery industry, appears to have everything we could want in terms of easy use, with proper self-management of its cells:

 

 

 

Tenergy LIFEPO4 6.4V 4.5Ah Pack - Item #31949

 

http://www.tenergy.com/31949

 

https://www.amazon.com/Tenergy-4-5Ah-LiFePO4-Rechargeable-Battery/dp/B00CPTCCPK

 

(This $39.99 Amazon price is a really good deal, as most places sell it for $69.99)

 

 

And here's the matching charger:

 

 

Tenergy 6.4V (2-Cell) Intelligent 1A LiFePO4 Battery Pack Charger - Item #01369

 

http://www.tenergy.com/01369

 

Amazon doesn't carry it. (Why not?)

 

Search Google Shopping: https://www.google.com/search?output=search&tbm=shop&q=tenergy+01369&oq=tenergy+01369

 

----

 

Here are some noteworthy specs for the battery:

 

Nominal Capacity: 4.6Ah (typ.), 4.5Ah (min.)

Nominal Voltage: 6.4V

Max. Discharge Current (Pulse): 8.0A

Discharge Method-Standard: 900mA

Max. Continuous Discharge: 5.0A

Discharge Cut-off Voltage: 4.6V

Battery Dimension: 70x47x101mm (It's about 4-inches tall)

 

I will add that, when fully charged, it can yield no more than 3.33V per cell or 6.67V, but will drop quickly to 3.2V per cell (6.4V) where it will stay throughout most of its discharge. The protection module will shut down the pack at 4.6V (2.3V per cell), but a USB Regen that has to provide 5V power to a DAC will fail before you can get down to 4.6V. If the USB Regen is not supplying 5V power to a DAC, then this battery will shut down before failing to satisfy the Regen's 3.3V regulator (which probably wants to see a little more than 3.3V, anyway, but probably doesn't need as much as 4.6V.)

 

So there you go... Now who wants to be first to give it a listen? :-)

 

By the way, you cannot combine these in series to achieve a higher voltage. If you want a different voltage, Tenergy has the following, similar products from which to choose:

 

Lithium Iron Phosphate

 

Mike

[zilch0md]

Very cool. Now you are getting somewhere Mike!

 

[Not that you will see me fall in love with batteries any time soon. I just can't love 'em the way you do. ]

 

Thanks Alex!

 

Coming from you, I'll take that as an endorsement - of the approach at least, if not the specific product.

[zilch0md]

In fact, it will fail to remain in regulation after it drops below 5.3V which is well above the battery's cut off voltage.

 

Thanks Alex. In the absence of any kind of voltage monitoring alarm, what would you expect a user to hear, while listening to music, when the USB Regen suddenly fails to get 5.3V? Would it just go immediately silent or do you think there might be a transition period, during which the sound quality starts to erode in some way?

[zilch0md]

Good idea! You can ignore the annotations I added to this photo when reviewing the Audiophonics PCM5102 DAC, but it shows a similar meter I hobbled together in the absence of good soldering skills. (I practice DIY for Dummies.)

 

 

With both male and female 5.5mm connectors, it's pretty versatile.

 

https://www.amazon.com/gp/product/B00JOB793W

 

https://www.amazon.com/gp/product/B011YKCK5M

 

https://www.amazon.com/gp/product/B00H0GVYMA

 

Battery hounds love these, too:

 

https://www.amazon.com/gp/product/B00ORGDQOK

[zilch0md]

Hi Mike!

 

Thanks for that awesome lecture!

I am currently on holiday in Torrevieja/Spain and cannot answer in details. All I know is that Lithium ion battery packs (it is not a LiPo brw) like the one I posted (with charger) cannot be sold without voltage regulators. I know that cautions posted by resellers and manufacturers are likely just precautions not to be sued by consumers. If you read about this battery pack sold in the US you will find this info as well:

If discharged too low, Lithium Ion batteries can become unstable and unsafe to use. However these battery packs have built in under-voltage protection. This means that when they fall below the cut-off voltage, the batteries will turn off, preventing the Lithium Ion cells from discharging too low. protecting your battery.

 

The included battery charger and over-volt protection ensure that the battery is charged at correct voltage levels. The charger will change its LED from red to green when the charging process is done.

 

This makes sure that the battery will not burn, smoke etc. However, with batteries it is always best to be safe. Buy it locally and ask the reseller about the limitations and how to use it properly. Btw, I think this should be a 1s4p just looking at it. 2s2p is normally bulked in pairs. Now, back to sunny Torrevieja!

 

/Micael

 

Hi Micael,

 

First, first let me say that Li-Ion and LiPo have the same chemistry, the only difference being that LiPo (Lithium Ion Polymer) refers to Lithium Ion batteries where each cell is in a polymer sleeve (as with the RC batteries I use). When they are cylindrical, like the 4-cell pack you are referencing, they should be called Li-Ion, not LiPo. So, I had not used the proper terminology when I referred to those Li-Ion cells as LiPo, but they have the exact same chemistry, the same risk of fire if abused, the same minimum and maximum cell voltages, etc.

 

Have another look at the large print on this page: Lithium Ion Battery 7.4V 4400mAh

 

That pack is a 2S2P, not a 1S4P. If it were a 1S4P, its nominal voltage would be 3.7V, not 7.4V.

 

Quoting my earlier post:

 

There's a potential problem with the PCM-equipped 7.4V battery pack linked, above. On the specifications page, it indicates that the built-in PCM (Protection Circuit Module) has a discharge cutoff voltage of 5.5V. That's obviously not the cut-off voltage for individual cells, as they will measure 4.2V when fully charged, so it's the cut-off voltage for the entire pack.

 

Problem: This is a 2S2P pack, so if the PCM is not going to stop the pack from discharging into a load until the sum of two cells in series is 5.5V, each cell could fall to an average of 2.75V per cell.

 

Search the web high and low - you will not find anyone advising you to discharge Li-Ion (or LiPo) cells down to voltages below 3.0V, so the published specs for this pack are incorrect -or- the pack should be avoided. As I previously shared, even allowing cells to fall all the way to the recommended 3.0V minimum can leave you having to soon replace a pack.

 

:-)

 

Mike

[zilch0md]

Another good reason for using the mini DVM module, and ensuring that the voltage doesn't drop below 6V.

With the Regen it will still be in regulation with a 6V input, and you won't be able to tell by a change in the Regen's performance.

 

Roger that. And it's funny, that even when I'm using the alarming voltmeter with a 6S1P LiPo pack (powering the amp for my near field monitors), I look at the LED readout often enough that I usually never get to the point that it is sounding off (when any one cell reaches 3.3V, as I have it adjusted). If I find myself ending a listening session with the cells showing something like 3.4V, on average, I put the battery on its charger and swap in the other one for next time.

 

So, in reality, you're right (with one caveat which I will get to in a moment...) We don't need an alarming voltmeter or even an automatic cuttoff mechanism. We just need to glance at a simple DVM from time to time, fully understanding and acknowledging and embracing the FACT that Li-Ion/LiPo must not fall below 3.1V per cell. I can't help but add that safety margin of 0.1 to 3.0, because I have lost an expensive pack by pushing it repeatedly to 3.0V per cell - and it was just one cell that was hitting 3.0 before all the others did.

 

Still, 3.0 is the official absolute minimum "rock bottom" discharge voltage for a Li-ion/LiPo cell, not 2.95 or 2.9, and definitely not 2.75V, as with the previously discussed 2S2P pack's protection circuit. For LiFePO4, the absolute minimum discharge voltage is 2.0V. (Why not stop at 2.2V?)

 

Here's the caveat to using a voltmeter that monitors the series voltage of the entire pack: You don't have a clue what's happening with the individual cells. Even when using a balance charger that monitors the voltage of each cell independently, when you first start using the pack, even after resting overnight, the cells will all be at +/- 0.03V, more or less, but as you start to use them, the unavoidable differences of internal resistance leave some cells at higher voltages than others with the spread increasing as you drive them all down to your minimum voltage per cell.

 

It's a race. And there is ALWAYS a winner. The guy who gave up his electrons most freely will hit 3.0V sooner than all the rest and if the user is not deploying some kind of device or, to shut down the whole pack right then and there - where a single cell has hit 3.0 - you can end up losing the whole pack, with it refusing to take a charge.

 

Here's the rub: Tthe pack as a whole will ALWAYS showing a series voltage that averages MORE than 3.0 per cell when only one cell has actually reached 3.0. If you continue to use the pack, waiting or the AVERAGE to get down to 3.0V, the winner becomes the loser, as it is forced to go below the absolute minimum discharge voltage. That same cell will be tortured again and again, every time you drive the pack down to an average of 3.0V per cell, instead of stopping short at an average voltage that's high enough to prevent the cell with the least internal resistance - the cell that is most generous - from getting hurt by the stinginess of its siblings. :-)

 

So, if you're going to use a DVM to monitor a 2S, 3S, etc. battery pack, you really can't allow the pack to come anywhere near the official absolute minimum series voltage (nowhere near 6.0V for a 2S pack, nowhere near 9.0V for a 3S pack, etc.)

 

And really, this is not such a hardship in terms of play time (using 3.3V or even 3.4V as your minimum per cell, instead of 3.0V). Look at this annotated discharge curve for Li-Ion/LiPo packs:

 

 

Therefore, if I were not able to monitor cell voltages individually, especially with a 2S or more pack that isn't balance charged - if I could only monitor the series voltage of the whole pack - I would stop using a 2S Li-Ion/LiPo pack at 2x 3.4V = 6.8V, going nowhere near 6.0V. Monitoring the series voltage of a 3S pack, I'd stop at 10.2V, not 9.0V, etc. (For 2S or more LiFePO4 packs, when unable to monitor cell voltages individually, especially if the pack is not balance charged or the cells cannot be removed and charged independently, I'd stop using the LiFePO4 pack at 2.2V per cell, instead of assuming I can safely drive the series voltage down to a multiple of 2.0V.)

 

Mike

[zilch0md]

I've been using a 12V 9Ah lead acid battery to power my Regen for the last 2 months.

My DAC (Auralic Vega) does not require the 5V supply so I only need to charge it about once a week or more depending on use. It sounds great!

 

What voltage do you measure when your battery is fully charged?

[zilch0md]

It charges just over 14V then takes a week (depending on use) to run down to about 10V then I charge it again.

The battery replaced the Teradak 9V LPS I was using and the Regen seems to like the higher voltage supply.

It certainly sounds better.

 

That's great that your gear is good enough to allow you to hear an improvement going to the lead acid battery vs. the Teradak 9V LPS.

 

Regarding your battery's maximum of 14V...

 

Quoting: USB REGEN: Questions and Answers – UpTone Audio

 

Once you are certain that no 5VBUS is needed, then yes, you can run the REGEN from a 5V or a 12V supply.

 

But... 12V is not the maximum permissible voltage:

 

If you know that your DAC does not need any bus power at all—or for sure only just for initial handshake—then you really don't have to worry. Our USB hub chip and clock together draw about 50mA at 3.3V, so it would be almost impossible to overheat that second [3.3V] regulator. Even 20V dropped to 3.3V will, at 50mA be only about 0.84 watts.

 

You should be fine at 14V, as long as you're not supplying any 5V power to the DAC.

 

By the way, here's an excellent article you might consider reading:

 

Battery voltage and state of charge - Energy Matters

 

It includes this chart...

[TABLE=class: stcheader, width: 480]

[TR]

[TD=width: 119]State of Charge[/TD]

[TD=width: 119]Sealed or Flooded Lead Acid[/TD]

[TD=width: 120]Gel battery[/TD]

[TD=width: 120]AGM battery[/TD]

[/TR]

[TR]

[TD=class: stc, width: 119]100%[/TD]

[TD=class: stc, width: 119]12.70+[/TD]

[TD=class: stc, width: 120]12.85+[/TD]

[TD=class: stc, width: 120]12.80+[/TD]

[/TR]

[TR]

[TD=class: stc, width: 119]75%[/TD]

[TD=class: stc, width: 119]12.40[/TD]

[TD=class: stc, width: 120]12.65[/TD]

[TD=class: stc, width: 120]12.60[/TD]

[/TR]

[TR]

[TD=class: stc, width: 119]50%[/TD]

[TD=class: stc, width: 119]12.20[/TD]

[TD=class: stc, width: 120]12.35[/TD]

[TD=class: stc, width: 120]12.30[/TD]

[/TR]

[TR]

[TD=class: stc, width: 119]25%[/TD]

[TD=class: stc, width: 119]12.00[/TD]

[TD=class: stc, width: 120]12.00[/TD]

[TD=class: stc, width: 120]12.00[/TD]

[/TR]

[TR]

[TD=class: stc, width: 119]0%[/TD]

[TD=class: stc, width: 119]11.80[/TD]

[TD=class: stc, width: 120]11.80[/TD]

[TD=class: stc, width: 120]11.80[/TD]

[/TR]

[/TABLE]

 

... which shows that even if your 12V lead acid battery is designed for deep-cycling (is yours?) the battery is considered fully discharged at 11.80V.

 

How low are you taking your 12V battery before you decide to put it back on the charger? (You might want to keep a voltmeter connected to it, so that you can monitor its voltage during use.)

 

https://www.amazon.com/gp/product/B00JOB793W

 

0.28 Inch Mini Waterproof Voltmeter 3.5-30V Digital Voltage Tester Meter Sale - Banggood.com

 

Also: If you are at all concerned about not having to replace that battery anytime soon, you should only take it down to about 50% with each discharge cycle - no lower than 12.20 volts (per the chart above).

 

Again, quoting the article:

 

A Sonnenschein Solar Bloc 100 AH Gel Battery discharged to a depth of 70%, i.e. with only 30% or 30 AH (amp hours) remaining, will have a lifespan of around 1200 cycles, which is quite impressive. However, if it’s only discharged to 50%, the expected number of cycles skyrockets to around 1700! If a cycle is a day, that adds over 1.25 years to the life of the battery.

Depth of discharge, also known as DOD, shouldn’t be any more than 50% in most deep cycle batteries in order to get the best value for money. So if you have a 100 AH battery, consider the cut-off discharge depth being 50 AH.

 

This holds true with all makes and models of lead acid batteries: The deeper the depth of discharge for each cycle, the fewer cycles you will get from the battery before it must be replaced - and it's not linear. If it were linear, you could get twice as many cycles by discharging only to 50% of capacity than you could by discharging down to 25% of capacity, but that's not true. In fact, you will get much more than twice as many cycles out of a battery by discharging it to 50% instead of 25%. Truth: Deep-cycle batteries LOVE to be shallow-cycled!

 

For huge photovoltaic installations, shallow-cycling dozens of batteries can be imperative, but depending on your budget, feel free to "abuse" your single, small 9Ah battery by taking it down to 11.8 volts (0% capacity) on each cycle. When it no longer takes a charge, buy a new one. But you will be buying batteries much more frequently vs. taking it down to 50% each cycle.

 

Also: 0% means stop using it - there is no margin for error at 11.8V.

[zilch0md]

@ClothEars

 

I will add that if you would like to escape the inconvenience of manually disconnecting your battery from the load and attaching it to your charger at whatever interval is necessary to avoid going below your choice of discharge depth...

 

If your battery charger has the intelligence to turn itself off at 12.8V (or at least 13.8V?), instead of "cooking" the battery, you could just leave it permanently connected to the battery, using a simple appliance timer to keep it turned off during the hours that you are normally awake and turned on while you are normally asleep:

 

[ATTACH=CONFIG]27124[/ATTACH]

https://www.amazon.com/Intermatic-TN311-Heavy-Grounded-Timer/dp/B005MMSTNG

 

If your battery charger DOES NOT HAVE the intelligence to turn itself off at 12.8V (or at least 13.8V?), you should get a different charger.

 

This 0.75A Battery Tender could top off your battery every night while you sleep, if used in conjunction with an interval timer:

 

[ATTACH=CONFIG]27125[/ATTACH]

https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S

 

These accessory items might be of use to you, as well:

 

https://www.amazon.com/Battery-Tender-081-0069-6-Terminal-Disconnect/dp/B004JV6OMO

 

https://www.amazon.com/Battery-Tender-081-0148-25-Disconnect-Extension/dp/B000FW2MWW

 

With your having said that your 9.0Ah 12V battery lasts about one week between charges, I'm curious how many hours you're actually using it.

 

If you are only powering the USB hub chip and clock within the USB Regen, via its 3.3V regulator, the USB Regen will only pull 50mA. For a lead acid battery rated at 9AH (9000mAh), you should be able to run that battery for 180 hours (or more than 25 hours per day for 7 days.) Factory Ah ratings are usually for a specified load and depth of discharge, so who knows what those figures are, but they are most likely for a load greater than 50mA.

 

In any case, you will be shallow-cycling the battery (a good thing) if you use a timer to turn the charger on and off every night.

 

You can test the impact of leaving the battery connected to the unpowered charger, by just connecting and disconnecting the charger while playing music through the USB Regen. I doubt you will hear any changes, as long as the charger is unpowered - as it would be during the day, using the timer.

 

---

 

Lastly, if your 12V 9Ah battery is an AGM style battery, you should get the Battery Tender Plus charger, instead:

 

https://www.amazon.com/Battery-Tender-022-0185G-dl-wh-Charger-Maintainer/dp/B00DJ5KEEA

 

 

Mike

[zilch0md]

@zilch0md

 

I had a good look through your suggestions so I'm going to buy one of the mini digital volt meters and a more suitable charger to keep within the recommended charge range. I have a question though.

 

Will the charger do any damage to the volt meter or Regen if they are connected to the battery whilst charging?

 

The charger might put out as much as 16V or 17V, but even if you were using the USB Regen with the energized charger still connected to your 12V battery, the USB Regen can handle as much as 20V (per the FAQ) - as long as the USB Regen is not supplying 5V power to the DAC, in which case, even 12V would cause too much heat to be generated. But check the voltage of your charger - as long as its output is no more than 20V, I don't think you have to worry about it damaging the USB Regen.

 

It wouldn't be a bad idea to put an inline switch between your battery and the USB Regen - flip it on when you're ready to play - instead of powering the USB Regen 24/7.

 

https://www.amazon.com/gp/product/B00H0GVYMA

This little voltmeter for can handle up to 30V, so there should be no need for concern there, either.

 

https://www.amazon.com/gp/product/B00JOB793W

 

0.28 Inch Mini Waterproof Voltmeter 3.5-30V Digital Voltage Tester Meter Sale - Banggood.com

 

Mike

[zilch0md]

Mike, I have this CTEK 7200 on my AGM, appears I should have the Plus type, what's the difference ? Worth changing, I've run mine for 2 yrs so far.

 

https://www.amazon.com/CTEK-56-353-12-Volt-Battery-Charger/dp/B000FRLO9Y/ref=sr_1_3?ie=UTF8&qid=1466542493&sr=8-3&keywords=ctek+chargers

 

 

Reading its specs, I'd say there's no need for you to change anything - it's designed to work with AGM as well as other types of lead acid battery.

 

In the case of the Battery Tender vs. Battery Tender Plus, the "Plus" model is allegedly more intelligent, which is somehow better for AGM - according to their marketing literature. Either one would probably be OK with AGM, for our purposes in this context.

[zilch0md]

I'm not sure where the 20V came from but the absolute maximum voltage on a REGEN is 16V. And I wouldn't recommend running at 16 for long periods of time. If you run it at 16V all the time the life expectancy is going to go down significantly. A few days at 16V is all right, just don't make it a habit. If you go over 16V the life expectancy goes WAY down very quickly.

 

John S.

 

Thanks John. I'll take your word for it. :-)

 

Quoting the USB Regen FAQ (second to the last paragraph) - which needs to be revised?:

 

If you know that your DAC does not need any bus power at all—or for sure only just for initial handshake—then you really don't have to worry. Our USB hub chip and clock together draw about 50mA at 3.3V, so it would be almost impossible to overheat that second regulator. Even 20V dropped to 3.3V will, at 50mA be only about 0.84 watts.

[zilch0md]

Hello

 

I bougth the same battery in an other brand : Batterie lithium fer phosphate UN38.3 6V 4.5Ah T1 - AML9142 | All-batteries.fr

 

It seams to be a perfect deal.

 

I bougth a lead battery charger given for 6v (i check it outputs 6,8v).

Did i make a mistake ? I did not found specific 6,4v lifepo4 charger ...

 

I need 5v outpu, so I bought a tps lineat regulator TPS7A4700 on ebay noise < 40 microV.

Is ther a risk to damage the regulator if the voltage comes under 6v ?

Do you know if such a regulator will change the battery output impedance ?

 

 

About to unplug the battery during the play :

I check and loader redistance is not infinite whrn it is unplugged. The loader should be disconected from the battery, otherwise there will be DC leakage am i right ?

 

Do disconet it, i should disconnect both wires except if charger is unplugged from the wall ?

 

Thank you for your help

 

Bernard

 

 

 

Sent from my iPhone using Computer Audiophile

 

Tplink optical bridge/etalon streamer/audiogd nfb29/linn klout/athom sirrocco + athom rafale v38 hypex

 

Please, do not use that lead-acid battery charger with your LiFePO4 battery. That's dangerous. You could start a fire using that charger.

 

The same vendor who sells your battery offers this 1.3A smart charger for 2-cell LiFePO4 chemistry:

 

Chargeur Lithium-ion pour 7.4V (Pack 2S) 1.3A - CEL5101 | All-batteries.fr

 

---

 

As I had written in the post you quoted, a two-cell LiFePO4 battery has a nominal rating of 3.2V per cell (6.4V total) but when fully charged, they can be as high as 3.33V per cell (or 6.67V total). When discharging under a load, the battery's protection module will shut down the pack at 4.6V total (2.3V per cell).

 

If you need 5V for the USB Regen, because you are powering a DAC via the USB Regen's 5V regulator, you can just connect the battery directly to the USB Regen, allowing the USB Regen's built-in voltage regulator (which is low-noise, state-of-the-art), to shut down when the battery voltage becomes too low. You will not hurt the built-in regulator by under-powering it and you do not need to insert an external voltage regulator into the power line - this would only create more noise.

 

You only have to disconnect one of the battery leads to prevent discharge.

 

Mike

[zilch0md]

Oh, that's good, then. All you need is the right charger for your battery.