ACR ResQlink Battery - Personal Locator Beacon, PLB-375 battery replacement.

[jamie N]

My PLB-375 was bought in 2015, and tested for functionality every year (ish) since. Anyway, despite passing the test again this year, it's pushing it a bit to rely on it further when it's stated to replace after 5 years!
Checking it out, places wanted in the region of £130, to inspect, test and replace the battery.
Not an option.
I bought a new battery from XCELPLUS Security (UK) Ltd, which arrived after a few days.
During the fitting process, I measured the voltage on the old one, which was 9.72VDC, and the new one which was 9.26VDC.
Umhh; this being the case, I contacted the company supplying it, and got this response within the hour:

xcelplustore
Hi Jamie, thank you for your feedback and attention to detail. I'm familiar with these issues raised. I'll address them respectively. Firstly the voltage. Initially it does appear concerning, since the open circuit voltage (OCV) is lower than the original however, this can be described by a process called passivation on the lithium anode of a battery, which prevents self-discharge and ensures a long shelf life. I'll let you look it up, as to be honest, it's all a little over my head and chemistry wasn't my strongest subject. It is quite normal and once a load is applied to the battery pack the OCV will increase. More importantly is the NOM voltage will be higher than the used battery.
Hopefully I've addressed your concerns and you're satisfied with these explanations. If you still have any concerns and I'm able to answer them, I'll get back to you swiftly.
Kind regards
Darren Chapman
XCELPLUS Security (UK) Ltd

There was also a small issue with the connector, but that's irrelevant here.
I self tested the PLB and it responds just fine, so I consider that £100 saved. It should be noted though, that there's nothing at all tricky about this operation, it's 2 screws, a connector and taking care to reseal it, which is very easy to do.

 

[Dockhead]

Do you need to replace the seal? Is it available?

 

[jamie N]

No, the seal is perfectly safe provided adequate care's taken, such as being very gentle with it on removal, cleaning it with a piece of kitchen towel, as well as the grooves that it's seated in, just prior to reassembly. I regreased the seal with some Vaseline, as I didn't have any silicone grease such as MS4, which although it's petroleum based, I've never seen it actually harm an 'O' ring! The grease is beneficial in holding the 'O'ring in place as the 2 halves are remated.
It might help to remember that that small 'O'ring could be the difference between you living and dying.
The PLB's a good chunk of money, and it's daunting to think that one might bugger it up, but it's a very fundamental design, it's not micro surgery, and simply requires a bit of concentration and care.
I didn't do this after I'd reassembled mine, but it could be an idea to test it in a washing up bowl full of cold water. If underwater, and bubbles are coming out, then something's not sealed.
I'm not sure of the availability of replacement 'O' rings, apart from the manufacturer.

 

[Dockhead]

Thanks!

Yes, it could be life and death, but on the other hand, the rather costly device should be good for more than 5 years. Mine is 99% of the time just a backup to my EPIRB and it is not rational to go overboard with cost.

Mine still passes all of its tests although the battery is now way out of date.

I've seen the YTube vids where they show how it comes apart, and it looks quite idiot-proof (i.e., well designed).

Your water test is an excellent idea. The transparent body means you will be able to see whether there are any leaks.

If it leaks, it will ruin it, but I'm ok with that -- in that case I'll toss it and buy a new one.

Probably it makes sense to give these things an immersion test every year, actually.

 

[jamie N]

At work I did the 'bubble test' a number of times on various bits of kit worth many £k's of dosh. On the couple of occasions where the seal wasn't OK, it was quite surprising how little an amount of water did actually enter, and ultimately it's just clean, freshwater, which won't do much harm in this type of 'fail'.
There's a caveat though with the 'water in the sink' trial, in that it only works with Scottish Water. If one was so reckless as to attempt it with Thames Water, or (heaven forbid), Southern Water, it won't work as seeing the bubbles through contamination is quite difficult, and the PLB housing will dissolve.

 

[Dockhead]

Drifting the thread further, I have an ancient steam-powered McMurdo S10 MOB beacon. That one which is in the precise shape of a dildo.

The battery is at least 5 years out of date, if not more. It's been lying in a locker since I have 3x newer MOB1's.

I took it out this morning and did the short and long tests, which it passes with flying colours.

Rather than leaving it mouldering in a locker, I think I will put it in my grab bag, as an AIS MOB signal would be a great thing to broadcast from the liferaft if God forbid etc.

It uses a 6v lithium manganese etc. like the ResQLink. Maybe I will try to find a replacement battery for it.