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Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 1:25am
by batpot
Anybody use something like this for multiple battery types (eg 36v, 48v, and 52v batteries?)
https://www.amazon.com/Variable-Digital ... 07YC6LXNT/

This is one of those awesome products that fakespot rates F, and reviewmeta rates perfect.

Anything to look for with power supplies like this?

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 4:27am
by zeccato
CPS-6011 60V 11A Gophert
Not exactly cheap, but it is more powerful, including taxes and shipping about 150$.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 10:03am
by obcd
If someone accidently turns up the voltage or sets it wrong, you can overcharge your batteries.
A good BMS should be able to prevent this. Otherwise, it should work fine, but I would never use it without a BMS.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 12:42pm
by batpot
zeccato wrote:
Jan 24 2020 4:27am
CPS-6011 60V 11A Gophert
Not exactly cheap, but it is more powerful, including taxes and shipping about 150$.
11 amps is overkill; not sure many batteries can take that?
obcd wrote:
Jan 24 2020 10:03am
If someone accidently turns up the voltage or sets it wrong, you can overcharge your batteries.
A good BMS should be able to prevent this. Otherwise, it should work fine, but I would never use it without a BMS.
Right...pretty minimal risk.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 2:14pm
by zeccato
batpot wrote:
Jan 24 2020 12:42pm
wrote:
Jan 24 2020 4:27am

11 amps is overkill; not sure many batteries can take that?



Usually I charger from 4-7 ah and are batteries lifepo4 48v 30ah (8 years old) and 7,5ah a123, and without bms, but I do examine with the balance charger from time to time, to be more secure of the stability of each 16s.
in the future I think I'll buy normal li-ion for the 30ah weight.

But with li-ions, you have to be careful,
preventing flammable things from being near

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 24 2020 6:35pm
by Hillhater
Im sure it will put some charge in your batteries, but remember it is only a power suppy ( CV reg ?) and NOT a CC/CV controlled charger.
Most batteries are charged with CC initially (to about 80%).
A cheap 12/24v power supply, with something like a 7210A charge controller would be safer for the batteries and a similar cost.
https://www.ebay.com.au/itm/MPT-7210A-L ... 310f308416

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 25 2020 3:16am
by zeccato
Hillhater wrote:
Jan 24 2020 6:35pm
Im sure it will put some charge in your batteries, but remember it is only a power suppy ( CV reg ?) and NOT a CC/CV controlled charger.
Most batteries are charged with CC initially (to about 80%).
mine seems to be a CC/CV controlled charger,
charged with CC initially.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 25 2020 7:55am
by obcd
The power supply also has a current control, so you can limit current.
If you set the voltage to the maximum you want to go, you can set the current to the amount you want the batteries to charge.
So, basically, it will work equal to a CC/CV charger.
Good chargers will keep charging, even when the max voltage is reached until the charge current drops to 1/10 of it's normal value and shut off at that point. If you only intend to charge up to 80%, that really isn't needed and it shortens battery life if you do.
The only thing you miss is the power supply switching off when your batteries have reached their voltage equivalent to 80% charge.
You will need to set the supply voltage some fractions of a volt higher, or it won't pump current into the batteries when they nearly reached their 80% charged voltage.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 28 2020 8:44pm
by batpot
zeccato wrote:
Jan 25 2020 3:16am
Hillhater wrote:
Jan 24 2020 6:35pm
Im sure it will put some charge in your batteries, but remember it is only a power suppy ( CV reg ?) and NOT a CC/CV controlled charger.
Most batteries are charged with CC initially (to about 80%).
mine seems to be a CC/CV controlled charger,
charged with CC initially.
So is the one I posted. You can see the indicators on the LCD display.
My understanding is all power supplies on a battery will be CC until the load (battery) reaches the dialed in voltage, then switch to CV at virtually no amps, unless/until the battery drops below the dialed voltage again, and cycle repeats.
obcd wrote:
Jan 25 2020 7:55am
Good chargers will keep charging, even when the max voltage is reached until the charge current drops to 1/10 of it's normal value and shut off at that point. If you only intend to charge up to 80%, that really isn't needed and it shortens battery life if you do.
The only thing you miss is the power supply switching off when your batteries have reached their voltage equivalent to 80% charge.
You will need to set the supply voltage some fractions of a volt higher, or it won't pump current into the batteries when they nearly reached their 80% charged voltage.
Not sure I follow this.
Once the battery hits the dialed voltage, amp output should effectively drop to zero, and maybe will switch back and forth between CV/CC if the volts drop below a theshold (say it loses a 10th of a volt), the charger might kick back on for a bit.

Why would this reduce the battery life?

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 28 2020 11:39pm
by Hillhater
Hmm ?
I would have expected a “power supply”. To provide a constant , preset, Voltage and Current to whatever load you apply...not a variable voltage and current over time ?
Does this unit have a specific “charger” setting option.?

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 29 2020 12:27am
by jonescg
I tried using one of these metal cage style power supplies for charging a small battery and it would constantly wig out.
Image
So definitely go for something with current control.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 29 2020 3:38am
by obcd
I was just explaining how a good lithium battery charger is suposed to work.
If you charge lithium batteries for 100% every time, you will reduce battery life doing so. If you only charge up to 80%, battery life can be 2 - 3 times higher.
In your case, the batteries will never reach the voltage you set to your supply. The current will indeed reduce when the battery voltage comes close to the supply voltage and will become so low that the battery voltage isn't increasing anymore. That's why chargers apply a slightly higher voltage, but they turn it off when they see the current dropped due to the battery beeing fully charged.
So, for charge up to 80%, it's ok. For going up to 100% charge, it's very tricky.

The supply Jonescq tried to use is not having a current limiter. It will simply turn off it's output at an overcurrent situation and turn it on again after a couple of seconds. That's why it can't be used for charging. The internal resistance of a battery pack is so low that a fraction of a volt higher voltage already causes a massive increase in current.

A lab power supply offers you the requested voltage until the maximum set current is reached. It will than reduce it's output voltage to generate that maximum current into the load.
So you just turn it on without load to set it's voltage. Next you short it's output terminals and you set it's maximum current.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Jan 29 2020 8:30am
by zeccato
I'm satisfied with mine, I don't need various battery chargers anymore.
I charger the lifepo4 at 90%, and sometimes check with the test for safety the parallel that increases before the others.
When I need 100% sometimes I finish to charge with the balancer charger to 99%,
I don't trust a lot of Bms (in the balansing), they were giving me trouble, instead i use the cut voltage allarm (When I need sometimes).
However, to avoid risks it is necessary to have everything under control.
Better is to have oversized batteries.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 15 2020 5:55pm
by john61ct
so much misinformation

and then capped by spam

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 7:52am
by zeccato
john61ct wrote:
Feb 15 2020 5:55pm
so much misinformation

and then capped by spam
Can you clear up some misinformation? thanks.
for example: including these good info regarding my power supply Gophert and the lifepo4 battery:
manual see below.

john61ct wrote here: viewtopic.php?f=14&t=40628&start=25
The PSU has no termination logic at all, it is doing no regulation toward the end of the cycle except capping **voltage** only - that voltage is OK BTW.

That is the resistance of the overcharged battery causing amps accepted to fall.

Charge should be stopping at 0.05C or IOW when trailing amps has dropped to a 0.5A rate per 10Ah of bank capacity

or maybe 0.02C but IMO that's too stressful, earlier is better for longevity.

But really a simple HVC is much easier to implement, could increase voltage a bit say 3.55V if doing CC only.

Just allowing overcharge like that is not only bad for the batteries, but risky wrt fires as they get worn out.


Zeccato's question was:
can I charge the battery up to 80% or 95% (without Bms) directly with Gophert without damage? with c.c c.v, without Hvc?

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 9:17am
by john61ct
I'm not willing to go through it all correcting each mistake, doing too much of that already.

But ask specific Qs if you like. The below has all been stated already many times, will repeat again here for you.
zeccato wrote:can I charge the battery up to 80% or 95% (without Bms) directly with Gophert without damage? with c.c c.v, without Hvc?
Forget SoC%, mostly going to be inaccurate, arbitrary anyway for this context.

Use voltage (only, for CC-only charging much easier) and CV / Absorb hold time or endAmps (rarely, only when precision is required)

If you top balance, use the balance charger to do that, at say 3.5V holding CV until 0.05C trailing amps.

For normal charging, no need for such precision, and terminate at lower SoC.

Go to 3.45V and stop is fine. Use an HVC to be safe, you should not rely on yourself nor just an alarm.

If you are monitoring per cell cutting charge based on that directly, that is best.

But if you trust your cells are in balance, then set your pack-level HVC to a voltage so that it cuts out before any of the cells go over say 3.55V.

If you want to add some CV hold time (but why?), go back and do it manually constantly watching current fall until endAmps 0.05C is reached.

But will only add a few % more capacity usage, IMO not worth the trouble.

That's it. Yes can endlessly discuss every factor and variable, but IMO just confuses the issues.


Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 9:39am
by eMark
AGREE!

He just wasted our time on another thread implying he had a 16S battery when in fact he just now says it's a 14S ...
Talk About Misdirection.

What he really needed for his 8 yr ageing battery costs only $15. But know he thinks his problem is best solved with an overcharge alarm/buzzer when he does a "quick charge" on his 8 yr ageing battery at 90 to 97%.

OK, so what he could have purchased 2 yrs ago is the Tenerty 5-in-1 Intelligent 7S Cell Meter (with IR feature) for both cell monitoring and discharge bottom balancing (when needed) before charging. It's only $15, maybe get a couple at that price ...

https://www.amazon.com/Tenergy-Battery- ... B0178P8H9U
https://cdn.sparkfun.com/assets/0/3/a/2 ... manual.pdf



... and he's upset with us when he instead should be upset with himself and the risk of starting a FIRE .

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 9:40am
by john61ct
So tired.

please just stop

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 9:45am
by john61ct
He has 16S batteries, your idea that they are 14S comes from where?

Maybe you think LFP has voltage levels anything like the cells you're used to? they don't.

7S voltage checker will not be useful here.

The packs may or may not be worn, why assume that?

Again LFP lasts 10x longer than the cells you're used to, 3000 cycles may be barely broken in if treated well.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 9:49am
by john61ct
And please do not post that you "agree" with me, it's embarrassing when you clearly aren't bothering to let anything I tell you even sink in.

I would like to just set you on ignore, but hate to imagine the misinformation you'd be spreading.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 10:21am
by zeccato
eMark wrote:
Feb 16 2020 9:54am
For P................
I disagree with that,
John61ct is giving good advice,
Think about it and be more calm.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 12:55pm
by DogDipstick
I have been doing this with a 3Kw power industrial cheapo PLC logid drive supply for about 2 years. 1 year blindly bluntly bulk charging lipos at 8 amps and 80v with a little ingenuity. Charges my half empty pack in an hour.

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 16 2020 5:37pm
by Hillhater
DogD
Many of us use “unconventional” methods and power systems for charging quite effectively.
However tho advise or encourage someone else you do not know the competancy level of, to adopt potentially unsafe methods, ....is not a good idea

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 18 2020 5:07am
by zeccato
john61ct wrote:
Feb 15 2020 5:55pm
john61ct wrote here: viewtopic.php?f=14&t=40628&start=25
Holding Absorb / CV too long is by definition overcharging even at 3.43Vpc, before you were talking until trailing current drops to 0A!

As stated, consequences include reduced pack longevity...........
I'm not sure I fully understand,
can you confirm to me that holding the c.v. too long could have consequences neither for the longevity of the battery?

Then one said to me:
(However, even with a very common Chinese charger the CV phase is not maintained until the absorbed current is zero, the charger turns off when the voltage reaches the preset value even if the cells would continue to draw a minimum of current.)

Re: Using cheap adjustable power supply to get 80% charge?

Posted: Feb 18 2020 5:44am
by john61ct

zeccato wrote:can you confirm to me that holding the c.v. too long could have consequences neither for the longevity of the battery?
Not sure I understand that "neither", but again, holding CV after amps fall too low is overcharging and will reduce longevity.

> CV phase is not maintained until the absorbed current is zero, the charger turns off when the voltage reaches the preset value even if the cells would continue to draw a minimum of current

Yes, that is CC only charging, e.g. "just stop at 3.55V". The C-rate will then determine how far from 100% SoC you are, at a low rate enough might be 98%, but if fast charging might be 88%