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Big mistake I guess

Posted: Jan 18 2020 1:03am
by ebike11
Hi guys
I was watching a youtube video where someone was adjust the potentiometer adjusters inside their battery charger to increase voltage rather than paying more for a higher voltage rated charger. I opened my 72V charger up and noticed 88V stamped
So since I have a 20s pack, I increased the voltage to around 82V. I failed to notice that the charging amps of the charger was rated 4A, and I stupidly turned up that pot adjuster to 6.5A. 20 min. later of charging, I heard a pop and the charger turned off and no longer works. Buying another one isnt a problem, just wondering if the damage is commonly repairable or off to the garbage heap??
Thanks

Re: Big mistake I guess

Posted: Jan 18 2020 2:07am
by goatman
if you put volts up, amps should go down. ive had a couple fried chargers from that. you know where the power chord plugs into your charger from the wall. that receptacle is soldered to the board. look there to see if its smoked/burnt. ive had to resolder that once. look at the components attached to the heatsinks or charger case for burnt legs. I call them mosfets but other things look mosfets so if it has a burnt off leg google what it is and replace it and hopefully it works. good luck

Re: Big mistake I guess

Posted: Jan 18 2020 6:46pm
by markz
open up the charger, and see if there is any black marks indicating a bad component, also check the fuses
that is the easy part
the hard part is do you replace the parts, and solder them in and see if it works, because something else down the line may have fried as well. I fried a few Meanwell chargers.

Re: Big mistake I guess

Posted: Jan 18 2020 11:04pm
by ebike11
markz wrote:
Jan 18 2020 6:46pm
open up the charger, and see if there is any black marks indicating a bad component, also check the fuses
that is the easy part
the hard part is do you replace the parts, and solder them in and see if it works, because something else down the line may have fried as well. I fried a few Meanwell chargers.
Hi..I see black residue on a large yellow componant, not a capacitor though. Not sure if its worth fixing though.

Re: Big mistake I guess

Posted: Jan 18 2020 11:29pm
by markz
Then its not worth the time nor effort when you can just buy another one.

Re: Big mistake I guess

Posted: Jan 19 2020 6:59am
by dogman dan
On the bright side, you did not burn your house down, overcharging your battery to 4.4v per cell. That would have at least, ruined the battery in one charge.

84v maximum, which is where your 72v charger was set to begin with.

Re: Big mistake I guess

Posted: Jan 19 2020 11:22am
by wturber
ebike11 wrote:
Jan 18 2020 11:04pm

Hi..I see black residue on a large yellow componant, not a capacitor though. Not sure if its worth fixing though.
Snap a photo and post it. Sometimes it is fun to fix something just to see if you can. Also, you could use it as a spare if you get a new one anyway and it is one tiny bit less bit of junk in a landfill somewhere.

Re: Big mistake I guess

Posted: Jan 20 2020 12:30am
by ebike11
dogman dan wrote:
Jan 19 2020 6:59am
On the bright side, you did not burn your house down, overcharging your battery to 4.4v per cell. That would have at least, ruined the battery in one charge.

84v maximum, which is where your 72v charger was set to begin with.
Hi..the charger itself was a 72V and rated 4A from the factory. However my pack that I got recently is 20s so I thought to increase the charger voltage to 82V or so (4 1x20 cells)
The charger had 88V printed on one of the larger componants inside the charger. If I had left the amps at 4A and only increased the voltage, wouldnt that be safe and ok for a 20s pack??

Re: Big mistake I guess

Posted: Jan 20 2020 1:01am
by amberwolf
a device (charger, power supply, controller, etc) that converts from one thing to another has a wattage rating it can handle, beyond which the heat it creates begins to damage things.

so generally you end up needing to decrease the current output if you increase the voltage output.

however, the charger failure is probalby not from that, it is probably from a component that could not handle the higher voltage.

just becuase one component in a device has a certain rating does not mean that any other component in there has a rating that high.

in order to use a device at a certain voltage/etc., *all* components that see that voltage/etc must be capable of it.

so you have to reverse engineer the device, trace out the whole circuit, to see which components will see what voltages, currents, etc., to be able to safely turn up the voltage / etc.

you can make a guess taht if the major parts like caps and fets and power diodes all are rated for the voltage and current you're turning it up to, the device will probably work...but there's no guarantees. ;)

Re: Big mistake I guess

Posted: Jan 20 2020 3:30am
by ebike11
amberwolf wrote:
Jan 20 2020 1:01am
a device (charger, power supply, controller, etc) that converts from one thing to another has a wattage rating it can handle, beyond which the heat it creates begins to damage things.

so generally you end up needing to decrease the current output if you increase the voltage output.

however, the charger failure is probalby not from that, it is probably from a component that could not handle the higher voltage.

just becuase one component in a device has a certain rating does not mean that any other component in there has a rating that high.

in order to use a device at a certain voltage/etc., *all* components that see that voltage/etc must be capable of it.

so you have to reverse engineer the device, trace out the whole circuit, to see which components will see what voltages, currents, etc., to be able to safely turn up the voltage / etc.

you can make a guess taht if the major parts like caps and fets and power diodes all are rated for the voltage and current you're turning it up to, the device will probably work...but there's no guarantees. ;)
Thanks a lot for your helpful advice.
The chargers arent that expensive so at least I could experiment. So on average..its fairly safe to increase the voltage as long as i turn down the amps?? Just good to know for future reference. As u said..all componants should be able to handle the power levels so it still could be risky

Re: Big mistake I guess

Posted: Jan 20 2020 10:56am
by TommyCat
I've found this thread very informative on the operation and adjustment of chargers.

https://electricbike.com/forum/forum/kn ... d-advanced

Re: Big mistake I guess

Posted: Jan 20 2020 1:47pm
by wturber
ebike11 wrote:
Jan 20 2020 3:30am
So on average..its fairly safe to increase the voltage as long as i turn down the amps??
Re-read his post. What he's telling you isn't that simple.

Re: Big mistake I guess

Posted: Jan 21 2020 7:37am
by dogman dan
I missed it where you said 82v. A 72v nominal charger should have come set to 84v anyway. If it was outputting 72v, its really a 60v charger, or thereabouts. So that would be pushing it a bit, to set it to 10v more.

Bear in mind,, even good stuff just sometimes has a weak link built in. It passed test at factory, but still can't run a very long time. You may have just had a part about to fail early anyway, and then turning it up fried it. Unfortunately, you voided any warranty when you tweaked the pots.

But yeah, in simpleton terms, if the thing is intended to run at x watts, and then you turn up the watts, it fails sooner. So if you jack up volts a lot, you should turn down the wattage, ( turn down its amps) back to spec. That's better than taking a 200w charger, and running it at 250 or 300w.

But in your case, you were running at around 300w, and turned it up to 530w. I would expect a fail doing that.

Re: Big mistake I guess

Posted: Jan 21 2020 4:38pm
by ebike11
dogman dan wrote:
Jan 21 2020 7:37am
I missed it where you said 82v. A 72v nominal charger should have come set to 84v anyway. If it was outputting 72v, its really a 60v charger, or thereabouts. So that would be pushing it a bit, to set it to 10v more.

Bear in mind,, even good stuff just sometimes has a weak link built in. It passed test at factory, but still can't run a very long time. You may have just had a part about to fail early anyway, and then turning it up fried it. Unfortunately, you voided any warranty when you tweaked the pots.

But yeah, in simpleton terms, if the thing is intended to run at x watts, and then you turn up the watts, it fails sooner. So if you jack up volts a lot, you should turn down the wattage, ( turn down its amps) back to spec. That's better than taking a 200w charger, and running it at 250 or 300w.

But in your case, you were running at around 300w, and turned it up to 530w. I would expect a fail doing that.
Thx again..yes lesson learned
Since my 20s pack is 72v (84v fully charged)
I just ordered an 84v 3A charger and wont touch it. Well...ill leave the amps at 3A but ill turn the voltage pot down a bit to 82V so 4.1v per cell to extend the pack life

Re: Big mistake I guess

Posted: Jan 21 2020 9:11pm
by markz
You could do a split battery pack, get two 84v3a chargers and charge up the battery in half the time, if the C-rating is healthy.

I have a 36V 27Ah split into halves, using Dell chargers of 20.50V and 8A, cheap $10-$15 Dell laptop chargers. So I only get 41.00V out of 42.00V. I could use a step up converter to get that extra volt. Another option for me is I could get chargers that are 20V and 12 or 15A but those chargers are $50+ each.

Something to consider if your rocking your own battery pack.

The Meanwell chargers HRP were bulky but spat out plenty of amps at an adj voltage. Not as durable as LED psu's which then get you down to single digit amp rating, and pricing aint that appealing.

Re: Big mistake I guess

Posted: Jan 21 2020 9:41pm
by ebike11
markz wrote:
Jan 21 2020 9:11pm
You could do a split battery pack, get two 84v3a chargers and charge up the battery in half the time, if the C-rating is healthy.

I have a 36V 27Ah split into halves, using Dell chargers of 20.50V and 8A, cheap $10-$15 Dell laptop chargers. So I only get 41.00V out of 42.00V. I could use a step up converter to get that extra volt. Another option for me is I could get chargers that are 20V and 12 or 15A but those chargers are $50+ each.

Something to consider if your rocking your own battery pack.

The Meanwell chargers HRP were bulky but spat out plenty of amps at an adj voltage. Not as durable as LED psu's which then get you down to single digit amp rating, and pricing aint that appealing.
Hi
I wont be able to do that nor want to risk it. Its a pack i just got from em3ev so im hoping ill get long life from it.

Re: Big mistake I guess

Posted: Jan 22 2020 7:53am
by dogman dan
If you charge that battery to 4.1v all the time, it will never have enough charge to get the bms to balance it. So once in a while, you will have to turn it back up, and do a few cycles charging it full, to get fully balanced again.

You will know when its time, when the battery won't hold even 80v after you unplug from an 82v charge. At that point, you may have some cells that are at 4.25v each charge, and some at 4v. But when the charge finishes, the bms will drain the high charged cells to 4.2v. But meanwhile, you got some groups that never reach 4.1v. So if you can't hold 79v, when normally you see 81, its needing a balance.

It should normally drop some voltage by morning after a 4.1v charge. What I mean is when that gets to be more overnight voltage loss than you normally get, its telling you its waaaaaay out of balance then. Same thing if you notice it cuts off at higher voltage than usual.. if the bms stops early, its because one cell group is completely empty.

Re: Big mistake I guess

Posted: Jan 22 2020 4:40pm
by ebike11
dogman dan wrote:
Jan 22 2020 7:53am
If you charge that battery to 4.1v all the time, it will never have enough charge to get the bms to balance it. So once in a while, you will have to turn it back up, and do a few cycles charging it full, to get fully balanced again.

You will know when its time, when the battery won't hold even 80v after you unplug from an 82v charge. At that point, you may have some cells that are at 4.25v each charge, and some at 4v. But when the charge finishes, the bms will drain the high charged cells to 4.2v. But meanwhile, you got some groups that never reach 4.1v. So if you can't hold 79v, when normally you see 81, its needing a balance.

It should normally drop some voltage by morning after a 4.1v charge. What I mean is when that gets to be more overnight voltage loss than you normally get, its telling you its waaaaaay out of balance then. Same thing if you notice it cuts off at higher voltage than usual.. if the bms stops early, its because one cell group is completely empty.
Ok thanks!!
The reason I set it to 4.1v is I read on here that the cells will have a longer life and there isnt a need to get to the max 4.2v..but ill do as u mentioned and fully charge now and then.
What about the very first charge cycle of a new pack? Should it totally be fully charged then totally discharged to 3.6v? Or does it matter
Thanks

Re: Big mistake I guess

Posted: Jan 22 2020 8:19pm
by markz
You might want to search out Justin_le's posts because he's mentioned the life expentancy of cells. I remember reading that todays cells its not really an aspect. I cant find it off hand.

Life expectancy is more correlated to DOD so lots of shallow discharges from say 4.20V down to 3.90V as apposed to deeper discharges from 4.20V down to 3.20V.

The BMS will only balance once it hits a certain level, so above 4.10V it starts to balance. That too will make the battery last longer.

Newer cells, charging to 4.20V vs 4.10V will be good to confrim if it really makes a difference.

ebike11 wrote:
Jan 22 2020 4:40pm
Ok thanks!!
The reason I set it to 4.1v is I read on here that the cells will have a longer life and there isnt a need to get to the max 4.2v..but ill do as u mentioned and fully charge now and then.
What about the very first charge cycle of a new pack? Should it totally be fully charged then totally discharged to 3.6v? Or does it matter
Thanks