7dayshop 8-way NiMh AA/AAA smart chargers back in stock @ ?9.99

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HerbertMans

New member
jarvist said:
The 7dayshop 8-way NiMh AA/AAA smart charger is back in stock again (@ ?9.99 delivered):

http://www.7dayshop.com/catalog/product_info.php?cPath=777_3&products_id=101271

It makes a great personal / backup charger, particularly if you're upgrading from a dumb charger.
Not as clever or well made as the Maha brand, but seems fairly reliable.
The included 12V cigarette lighter adapter makes it a pretty useful setup...
Click to expand...
Seems like very fair deal.. It is bit old thread but I would love to get the product soon.
 
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Hammy

Member
I was excited for a moment then as I thought the V8 Supercharger was back in stock but I realise it's an old thread!

I have two already and they have been reliable and fast - I sometimes have to recharge a lot of AAA batteries in a hurry and the other ones I have bought have been unreliable and significantly slower so another couple of V8s would go down very well.
 
jarvist

jarvist

New member
Hammy said:
I was excited for a moment then as I thought the V8 Supercharger was back in stock but I realise it's an old thread!
Click to expand...
Me too, and I started the original thread!

I think the Vapextech 8 cell smart charger (~?17) is probably the best replacement, but this is only by repute - I don't own one & haven't used one. Does anyone out there in the caving community have one? If so, could they have a look at the mains power adapter + report back on what sort of connector / voltage + current it supplies? The V8 are great in running off a standard +ve pin plug at 12V - for off-grid Photovoltaics on expedition & vehicle charging situations.

My V8 is still ticking along, though the AAA battery springs are slowly getting damaged by catching on AA cells.

http://www.amazon.co.uk/gp/product/B008ETHO7G/ref=ox_sc_sfl_title_9?ie=UTF8&psc=1&smid=A2FRKKMHRJRROY
 
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Hammy

Member
Ah...the Vapex is the other charger I have.

I've got two of these. One is now only working on only four of the eight charging 'ports'. I would estimate that they take about half as long again to charge the batteries, but that's only an impression I get, no science involved.

https://www.dropbox.com/s/dpbkry0cp6fu3jc/2014-08-05%2013.25.15.jpg
https://www.dropbox.com/s/pvo392413pysbjt/2014-08-05%2013.25.02.jpg
https://www.dropbox.com/s/6w4hmygujuydawu/2014-08-05%2013.24.52.jpg

Hopefully these links to photos will answer your questions.
 
jarvist

jarvist

New member
Thankyou Hammy - very informative!
So the power adapter is 9W (0.5A @ 18V), but the charger can run on 12V directly, but it's not obvious whether it would be any slower in that case.

It then has that weird splitting of current, so it's only a fast charger if you have 2 or fewer cells in each of the two channels. So it seems a bit weak...

The old 7Day Shop charger is 20W (12V @ 1.7A), and promises 0.7A per cell (i.e. 3 hour charge from flat) independent of number of cells. So it's probably still better for bulk charging, as you have observed.
 
H

Hammy

Member
Tangent_tracker

Tangent_tracker

Active member
I would not use this as your primary charger though - only when required... It is not intelligent and obviously charges two cells in series, not a bad thing in emergencies but over time could be problematic for weaker cells...
 
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potholer

New member
The 2-cells-per-channel would be a drawback for many people, possibly particularly so on an 8-cell charger*, but the:
This high specification unit gives fast charging times and provides optimal battery care and performance, and features over-load and temperature protection as well as bad cell detection.
Click to expand...
would seem to suggest some intelligence - it'd be hard to say that with a straight face about a dumb or timer-based charger.

(*)Typically, an 8-cell charger seems to be the kind of thing for either a group, or for someone like me with a lot of cells, who may be particularly likely not to keep cells collected into sets which are used and charged together.

With my old V8, I often have 8 cells continually charging, and a pile of mixed cells-to-be-charged next to it ready to replace cells as they finish. I also often frequently use cells in 3s and 4s, as well as less often singly or in pairs, so a pair-based charger would be little use to me.
However, I guess it could be some use to someone who only ever used cells in even numbers, and who could keep used cells in sets until charged, especially if they had a proper single-cell-per-channel smart charger to deal with mingled cells, or single cells and those left-over from odd-numbered usage.
 
Tangent_tracker

Tangent_tracker

Active member
potholer said:
The 2-cells-per-channel would be a drawback for many people, possibly particularly so on an 8-cell charger*, but the:
This high specification unit gives fast charging times and provides optimal battery care and performance, and features over-load and temperature protection as well as bad cell detection.
Click to expand...
would seem to suggest some intelligence - it'd be hard to say that with a straight face about a dumb or timer-based charger.
Click to expand...

I doubt it - I should imagine over temp protection and bad cell is alone enough for some to call it intelligent but I would remain skeptical. If the cells were balanced it would put that in its sales but it hasn't... Like I said perfect for a backup or emergency use but otherwise best to stick to something that will look after your cells, and (one of my hates) not charge them too quickly. I recently suggested a nice looking delta V charger with user selectable current levels and capacity indication to a friend for about ?22 will see if I can find it...
 
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potholer

New member
Tangent_tracker said:
If the cells were balanced it would put that in its sales but it hasn't...
Click to expand...
I'm not entirely sure what you mean by 'balanced' there.

It could be thought odd that it doesn't say 'smart' if it is smart, but it would also seem odd to bother with temperature sensing and bad cell detection in a dumb or timer-based charger, and hard to claim either such types of charger were even vaguely 'optimal' for cells (leaving aside the fact that series charging of cells couldn't really be called 'optimal' anyway).

Tangent_tracker said:
Like I said perfect for a backup or emergency use but otherwise best to stick to something that will look after your cells, and (one of my hates) not charge them too quickly. I recently suggested a nice looking delta V charger with user selectable current levels and capacity indication to a friend for about ?22 will see if I can find it...
Click to expand...
For a smart charger with capacity readouts, there are the various BC-700/BC-700 models around from mid-?20s upwards. They've been around for a while and seem to have been well-received (and as far as I'm aware, they didn't seem to have the melting issues that some of the 1Amp '1000' variants had some years ago).
 
Tangent_tracker

Tangent_tracker

Active member
One immediate thought is, that if the charger rejects a group of two batteries, and bear in mind there is one indicator per group, does the user reject both or have the sense to swap each with a known good discharged cell so they can establish which cell is actually bad?

Balancing is a technical term where the majority of current flows in and out of the main battery terminals and the charger has access to each cell via secondary terminals to allow batteries to be treated individually... You normally have the main positive and negative plug plus a multiway connector that corresponds to the number of cells in the battery (number of cells -1). It would be possible to monitor the each battery in this case but I would have thought the blurb would have mentioned that, as it is quite significant!

Anyway, I stick to my original observations, although it is cheap and has over temp compensation so that is at least something :)
 
P

potholer

New member
Tangent_tracker said:
Balancing is a technical term where the majority of current flows in and out of the main battery terminals and the charger has access to each cell via secondary terminals to allow batteries to be treated individually... You normally have the main positive and negative plug plus a multiway connector that corresponds to the number of cells in the battery (number of cells -1). It would be possible to monitor the each battery in this case but I would have thought the blurb would have mentioned that, as it is quite significant!
Click to expand...
I know what balancing means in that context (like series charging of Li-Ion packs) where cells can't be charged individually by parallel independent circuits, and the series nature of the pack needs to be 'worked around' to charge without overcharging (overcharging generally being rather more of a safety issue for lithium-based chemistry than nickel-based).

While I'm not claiming to be an expert, balancing like that would seem to make little obvious sense for a charger for loose cells of any chemistry, since it would seem likely to require about as much (if not more) circuitry than independent charging would.

The whole point of 2-cells-in-series-per-channel loose-cell NiMH chargers (even smart ones)is to make them meaningfully cheaper to make than similar 1-cell-per-channel ones would be for the same number of cells.

But this is getting a bit OT.
 
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