Internal Battery Dead

[Ferenc]

Hey guys, just emailed BioSemi (then I saw this site) - we have a bit of a major issue and was hoping someone could help.

Currently, we are unable to send the equipment in question for repair/replace it - we will definitely be looking at doing this in the future.

So the basic issue is:

Our active two battery box is quite old now (it’s been here for a long time, well before I started).
So we believed the three sealed lead acid batteries had gone completely – a simple voltage test across the three was showing that they were no longer outputting anywhere near the required voltage. The charger wasn’t charging – it constantly had the green LED and the batteries weren’t retaining any charge. Believing this to be a battery issue (inside the battery box), we decided to order some 2V 4.5Ah batteries – the cyclon ones – now made by Enersys rather than Hawker. We couldn’t find a supplier that supplied a shrink wrap pack of three, so we three separate cells that we’ve connected with appropriately rated wire (16AWG) and are attempting to charge.

However, despite seeing that with a multimeter that the batteries are being charged (or I assume they are as their voltage is going up slightly), when we turn the battery box on, it does the same as it did with the old batteries – goes green for a few seconds with ‘Ready’ and then goes into ‘Shutdown’ - despite hours of charging the batteries.

The charger did recognise on the new batteries that they needed charge (it went immediately to the red ‘Full charge’ light and a parallel measure shows that it is charging).

We are midway through some EEG testing. I have verified that the charger is working fine - but both of our batteries seem to have gone within a few weeks of each other. Considering that they are strictly alternated and have been since they were bought many moons ago, it does make sense that their internal batteries have gone as the SLA batteries don't last forever and obviously get to a point where the chemical reaction can't be completed anymore - think we used up it's shelf life/battery cycles.

Have we missed anything obvious here?

I did a quick forum search and found a few similar topics but was hoping that someone may be able to help us with a temporary fix.

The replacement internal cells definitely did elicit a different reaction: when you plugged in the other cells, no matter how charged they were, it would stay with the green light on the charger and not charge at all. When we plugged the new cells into the circuit, it definitely came up with the red light and recognised that the new cells needed charging. Just been testing the charging today (had it on for two hours so not sure yet if it will hit that yellow light to recognise the 90% charge yet).

Many thanks,

Ferenc

[Ferenc]

Update: It has hit yellow so the batteries are being recognised by the charger (as far as I can tell with the multimeters as well) as charging up and they're now being trickle charged. Will see what happens next.

[Ferenc]

Still on yellow after 3.5 hours (so I'm guessing between the 90-100% state).

Batteries are currently at 7.55 volts while charging, 6.7 in their regular state so definitely supplying enough for the circuit. No idea why the box is still going into shutdown mode when I test to turn it on.

Let's see if the battery can get to full charge and then cycle? Not that should change anything.

Edit: Hit green. Turned battery on, ran for roughly 20 seconds before going into Shutdown mode again.

Not sure what I'm missing and why the shutdown mode is being triggered if there's enough voltage and the batteries have been charged.

[Ferenc]

So the charging part of the circuit seems fine - it seems the discharging part isn't. Batteries are charged (tested in another basic circuit) - they supply power. Suspect one of the ICs or potentially one of the other parts of the circuit has gone or been damaged - will test the parts individually as well as the resistors. It charges fine, the charger works, the batteries work, they supply what's needed - the issue rests with the rest of the circuit.

Essentially, circuit turns on and works for between 5-10 seconds before going into 'shutdown' - something must be tripping whatever trips the shutdown mode which I suspect is either triggered by the voltage or the current and the rate it's measured at by a component to signal it to shutdown.


Also to clarify - what voltage and amps should be coming into the charger box/leaving exactly? Want to make sure what we have is correct. We have an old charger (bought well before I started) and I suspect it's a little on the high side as I've been reviewing the other threads - it was stated that it's meant to be 9v?

Edit: so yeah, after multiple tests, it seems to be that the safety circuitry is shorting unfortunately. The batteries are fine and the charger appears fine.

Would a higher than 9v wall adapter cause issues for the charger/circuit? I have a sneaking suspicion that one of those adapters (we have two) is 12v DC (not confirmed).

[Coen]

The battery should go into shutdown at 5.5 V. If your battery shuts down at a higher voltage, then the shutdown circuitry must be defect. Please send the box for repair.

There should be two batteries with the system, please compare with the other battery.

Charger operating OK (7.55 V is a bit high but not alarming)

Best regards, Coen (BioSemi)