Troubleshooting: Metalsub dive light turns on bright but dims within seconds

I’ve got a rechargeable Metalsub dive light that’s about 5 years old now. I thought it was the batteries that needed replacing so I bought a new set of NIMH of the same capacity to swap the batteries in the pack.
Unfortunately it’s still not working right… I turn it on and it comes on really bright like it should, but then within 5 seconds or so it starts dimming and goes so dim it’s barely on. The same happens if I turn it off and on again.
The only other thing of note is that it emits a high pitch squeal that gradually goes down in pitch as it dims.

Anyone have any ideas for troubleshooting the issue?


Which model? There are lots.
Which specific batteries? There are lots. Claimed capacity is NOT a good indicator of quality. Sometimes the opposite.
Could be a funky light, or batteries. Details needed.

I’m not familiar with those lights at all but they look like they’re pretty high quality (and really high priced!). It sounds like the light must be using a boost driver to bring up the voltage from the 2x NiMH cells and adequately supply the emitter with what it wants. This means there is an inductor on the driver and associated other components, and that whine you’re hearing could be a sign that the inductor is failing, unable to boost anymore and thus dimming quickly, where the NiMH cells may not provide the voltage at all, or just long enough to light it up before sagging to the point where there just isn’t enough. Hard to say for sure without trying to diagnose with a meter and such. Unless you’re familiar and skilled with that and with component soldering (and assuming the driver is accessible/removable) I think I’d just contact them with the info you shared and see if they can help with replacement or something.

The model XRE700. I replaced the 4 original Varta 2400mAh AA NiMH with Amazon Basics 2400mAh. Maybe they ’re not up to the job? I replaced the switch a few years back, but other than that it’s all very tidy inside, nothings gone green from salt.

This is what the inside of ‘head’ looks like the PCB at the bottom seems to be adhered to the other side. I’d guess a thermal pad?

I’m pretty handy with a soldering iron if you think it’s possible to replace the inductor? It’s 7 years old and they seem to have discountinued it, so I’m not sure about getting spares for it. I couldn’t find anything on their website

Try emailing The Big Clive and see if he’d be willing to (nondestructively) take apart the driver and do a schematic on it and repair it (or trace the bad component(s)) if he finds out what’s wrong.

Offer some b33r money and/or a large bag of ghost-pepper pork scratchings. :laughing:

From their User manual, the original battery pack is 7.2 volts Li-Mangan(ese). NiMH may not be adequate. link

Sorry that should have said 6 batteries not 4, which makes sense 6 x 1.2v = 7.2v for the pack. With the wrapping removed from the pack it’s just 6 Varta NiMH batteries. The torch in the link is not the same as mine. I think it might actually be an XRE500R. I got the XRE700 from the order confirmation email but that might have been wrong. It looks more like this link

Ok, same battery voltage (and I presume current). As Correllux stated, inductor failure or other as Q3 would be the op-amp (a comparator to steady the current thru the inductor). My knowledge is limited, but given some visibility on this forum, some are much more apt in troubleshooting.

I see it’s a rather expensive light and is a few years past its prime (2012). If no better outcome of repairing, lame defeat, but there are much better lights and at a lower price.

That’s an interesting light. I was browsing their .nl site…thought maybe your NiMH model was long discontinued as they only showed a lithium one available now, but still some NiMH cell/pack replacements. The tail charging is kinda neat…also noticed that they warn not to run the light on high in air, just while underwater. Makes me wonder what construction they have in the head where the led mounts (or if that statement is just out of an abundance of caution).

I would imagine your Amazon cells are just fine…possibly even better than the Vartas that were worn out, considering generational changes that have trickled down into many not-Panasonic cells. It’s possible that they’re weak or shelf-discharged, though….a multimeter won’t check that very well but if you have the means to test them with a load maybe you can see if they’re able to maintain voltage normally. Have you tried throwing in some alkaline cells to see if the light works properly with those?

I don’t know how to diagnose an inductor really, but I would imagine that if you can rig the light to work with the head open like that so you can probe contacts while it’s running, maybe you can see voltage in vs. voltage out at the main wire pads for each. If you can pick the correct inductor values I’m sure those are super inexpensive and looks easy enough to replace for that one. But I don’t think I’d do that without being able to tell for sure if it’s failing (I’m one of those guys that would rather find out with certainty before throwing parts at a problem…learned via automobile repair. lol).

Do you know what led emitter is used in the light? I’m curious now if it’s a normal 3V or if it might have a 6V version in there.

Maybe thefreeman or gchart will stop by this thread and have some more helpful particulars to offer.