Aldi active energy battery

[ajh]

I have a drill and impact driver with a 20/40V 5.Ah battery that has had
little use. I am very pleased with the drill and driver which replaced
ryobi nimh powered ones that I had re celled already once. Brushed
motors but very cheap compared with Makita brushless ones and good
enough for my domestic use.

However I put the battery on charge yesterday as it was down to 1 bar
and the charger red LED indicated a faulty battery. It is past the 24
month warranty period.

From what I have read the problem is likely to be with the bms rather
than the cells so I am tempted to dismantle it and charge the cells
individually, any pointers?

Its not desperate as I have a spare

[Brian Gaff]

Is this a bit like the sensors in ink carts to stop you refilling them in
this case cycling them too many times?
Brian

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[ajh]

I don't know Brian but there is obviously a sensor in the charger that
sees something wrong. These batteries are in effect two 18V packs and
whether they discharge at 36V or 18V is dependent on the tool they are
fitted to. However the charger is 18V ish and charges the two 18V packs
in parallel. In this instance, from checking voltages one of the 18V
packs has dropped to 14V and the other to 16.5V and I suspect that is
causing the problem but where to turn next?

[Theo]

ajh <ne...@loampitsfarm.co.uk> wrote:
> However I put the battery on charge yesterday as it was down to 1 bar
> and the charger red LED indicated a faulty battery. It is past the 24
> month warranty period.
>
> From what I have read the problem is likely to be with the bms rather
> than the cells so I am tempted to dismantle it and charge the cells
> individually, any pointers?
>
> Its not desperate as I have a spare

It's possible the BMS puts some parasitic drain on some of the cells - eg if
it tries to power itself off a single cell rather than the whole pack, the
pack can get out of balance.

If the pack doesn't give you access to the individual cell terminals,
dismantling them and constant-current trickle charging each up to about 3.6v
would be what I'd do. Then put it back on the charger and see if it'll
charge.

https://www.youtube.com/watch?v=H9Mb5_nCVeo
has a teardown.

Theo

[Rod Speed]

Brian Gaff <brian...@gmail.com> wrote

> Is this a bit like the sensors in ink carts to stop you refilling them in
> this case cycling them too many times?

Not aware of anyone doing that with batterys, let alone Aldi.

[Rob Morley]

On Fri, 29 Jul 2022 14:44:25 +0100
ajh <ne...@loampitsfarm.co.uk> wrote:

> I don't know Brian but there is obviously a sensor in the charger
> that sees something wrong. These batteries are in effect two 18V
> packs and whether they discharge at 36V or 18V is dependent on the
> tool they are fitted to. However the charger is 18V ish and charges
> the two 18V packs in parallel. In this instance, from checking
> voltages one of the 18V packs has dropped to 14V and the other to
> 16.5V and I suspect that is causing the problem but where to turn
> next?
>

Charging each lower voltage cell individually would be my first
suggestion, but mighty tedious and possibly difficult getting to them.
Hopefully that brings everything back to life. Otherwise it's a cell
problem: identify and replace bad cells, or it's a charger problem: get
a new one if there's no obvious damage to fix in the current one.

Actually change that - first step is to make sure the contacts between
the battery and the charger are good, before delving any deeper.

[Peeler]

On Sat, 30 Jul 2022 05:11:41 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

<FLUSH the abnormal trolling senile cretin's latest trollshit unread>

--
Kerr-Mudd,John addressing the auto-contradicting senile cretin:
"Auto-contradictor Rod is back! (in the KF)"
MID: <XnsA97071CF43...@85.214.115.223>

[Brian Gaff]

That sounds like a duff cell or cells, and one supposes that the monitoring
circuit has this on continuous monitor Are the the Lithium sort, that may be
why the system is ultra sensitive, since reverse charging is prevented I'd
guess.

Brian

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"ajh" <ne...@loampitsfarm.co.uk> wrote in message

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[Mark]

> On Fri, 29 Jul 2022 14:44:25 +0100
> ajh <ne...@loampitsfarm.co.uk> wrote:
> from checking
> voltages one of the 18V packs has dropped to 14V and the other to
> 16.5V and I suspect that is causing the problem but where to turn
> next?

The BMS should stop a cell going much below 3volt (18volt for 6 cell)
once they have gone below 2.3volt the are dead and not recoverable


--

[Paul]

They aren't actually, but who is keeping track :-)

Try running a digital camera, which has a single cell in it.
It runs all the way down to zero, then you can recharge it.
The camera does not try to run it down to zero, but it
will self discharge that low.

I don't think single-cell digital camera battery at
precisely zero volts is good for it, but at least the
charger logic does not care. It may shorten the life
or reduce the capacity, for them to go that low.

******

OK, let's draw some packs.

3.7 3.7
3.7 0.0
3.7 3.7
3.7 3.7
3.7 3.7
3.7 3.7

OK pack Want to detect
22.2V when one cell is
reverse-biased
18.5V/6 cells = 3V
approx.

While it looks like I am "stopping the thing from going
below 3.0V", that is not the case. The protective feature
is attempting to tell when a single cell has discharged
before its brothers did. It just happens to work out to 3V.

When a cell goes into reverse bias, metallic lithium plates
out and this is hazardous.

This is why you don't discharge the *pack* by very much,
because you are wanting to keep any single cell from
being reverse biased.

If the BMS could monitor each cell individually, the
rules could be quite different then. Like, if all the
cells tracked exactly, you could continue to draw
energy from the pack when at (6)*3.0v. Versus not
drawing juice at (5)*3.7+0.0. the thing is, no pack
will ever track to the (6)*3.0v state -- not gonna happen.

In the case of a digital point-and-shoot camera with
a single lithium cell, there is no possibility of reverse
bias. And consequently, the single-cell wall charger has
no "rule" against charging a perfectly flat battery.
Whereas the charger for a sic-pack battery, has rules
about "oh, some battery has gone into reverse bias
and is a fire hazard".

This is also why you (partially) recharge batteries
in the off-season. To keep them out of the too-low
voltage zone (the zone where the BMS approximation
does such a shitty job). Check the battery every three months,
to spot any "trends". A 70-80 percent charge is
a good maintenance figure for Li. Leaving them at 100%
is not recommended. "Voltage stress". BatteryUniversity
has details.

Once a cell hits the knee, there is not a lot of
left-over energy to extract, so chasing the pack into
the noise doesn't really help. Drawing finer distinctions
when the pack is almost drained, is a waste of effort.
The not-very-low threshold is functionally good enough
for operating the pack. As long as you keep them out
of reverse-bias country, they will last through quite
a few cycles.

Paul

[ajh]

On 29/07/2022 20:29, Rob Morley wrote:
> On Fri, 29 Jul 2022 14:44:25 +0100
> ajh <ne...@loampitsfarm.co.uk> wrote:
>
>> I don't know Brian but there is obviously a sensor in the charger
>> that sees something wrong. These batteries are in effect two 18V
>> packs and whether they discharge at 36V or 18V is dependent on the
>> tool they are fitted to. However the charger is 18V ish and charges
>> the two 18V packs in parallel. In this instance, from checking
>> voltages one of the 18V packs has dropped to 14V and the other to
>> 16.5V and I suspect that is causing the problem but where to turn
>> next?
>>
> Charging each lower voltage cell individually would be my first
> suggestion, but mighty tedious and possibly difficult getting to them.
> Hopefully that brings everything back to life. Otherwise it's a cell
> problem: identify and replace bad cells, or it's a charger problem: get
> a new one if there's no obvious damage to fix in the current one.

I split it open and measured the two strings of cells, One string
averaged out about 2.8V but with one cell at 1.6V.

The other string was around 3V.

I ordered a usb charger from ebay which took a while to arrive (actually
5 little printed circuit boards with a micro USB input) and I soldered
on the two charging leads. I then proceeded to charge individual cells.

After a while I noticed not only did the cell I was charging increase
voltage but so did the other cells in the string. The BMS must have a
cell balancing function but it wasn't perfect.

The upshot is that the charge indicator on the battery pack shows it is
full, the Aldi charger still shows a fault but the battery appears to be
usable.