Magicshine MJ-872

TownyDC

Santa was good enough to bring me a magicshine MJ-872 for Chrimbo.
Has anyone any tips to get the best out of this light, I.e maximum run time, when to re-charge.
Wasn't sure whether it should be discharged before it's re-charged etc etc.
How do the power levels vary from low to high, any info would be appreciated.

Dave

Northwind

DIY is your man for battery questions but I've always found lipo cells to be pretty untemperamental, unless you leave them charged over summer. With my 872 i'm just charging, using, recharging.

Power levels- not being funny but just try it! 3/4 power is almost as effective as full power though.

Best results I've found are on the head- it seems like a bar light on paper but I had to stick it on my helmet one day as I'd brought the wrong mounts and it turned out to be way better on its own, than having it on the bars and a second light on the head.

diy

There is no memory in the cells so you can use and top up without damaging it.
There is no balance circuit either, so eventually your cells will get out of balance.
Normal li-ion precautions apply - charge in a fire proof environment and never for more than 4-5 hours without a break.
If your house does not have an RCD circuit use a breaker for this.

.blitz

I have an Open Light battery for mine and there is some useful info on their website www.open-light.de.

They advise that the battery is not stored in a fully charged state or left on charge, or charged and then used immediately.

The MJ-872 itself lights up the woods like a nuclear explosion there is light everywhere up/down/left/right as well as in front. It relies on brute force there is nothing clever going on with the optics but for £100 or so it is amazing.

Level 2 is fine for tooling along fireroads and you can crank it up to 3/4 as required. Used like this it lasts for 3+ hours no problem.

TownyDC

Thanks for the reply everyone, been out once with the light, very pleased with it, mega bright, just need to establish brightness requirement as I had it on full blast for most of the ride.....

composite

There is no balance circuit either, so eventually your cells will get out of balance.

Does this effect how long the battery will last, will it decrease the length of time it will power the light for?

aidso

I've managed to get 3.5 hours from a single charge with most people reporting around an hour less than this. Where I ride, you don't need the unit on full power constantly and when riding on the road I wouldn't have it beyond 75% - 50% can suffice. Be frugal and it pays off .

In relation to "will it decrease the length of time it will power the light for", as like most batteries, they will eventually deteriorate and this is around 500 charges, if that's what you meant.

bails87

On the road, aboslutely NEVER have it on anything above 50%, you'll blind drivers and other cyclists/pedestrians.

I've got the same light, commute down unlit NSL country lanes and only rarely have to put it onto 50%, otherwise it's on the lowest power most of the time.

.blitz

The last mile home from the Chase is on a road and I ALWAYS put it on 100% :P

Northwind

Aim's as important as power tbh. Pointed down-ish full power should be safe.

(my commuting helmet light is an XML torch... It'll burn the retinas out of any driver I point it directly at, so I aim it down- but I can lift my head to fullbeam dozy drivers. Gets their attention...)

diy

The issue regarding the balance circuit is not really due to the life of the cells. The pack contains 4 cells in a 2 parallel, 2 serial configuration giving 2 x volts and 2 x amp output of each cell (so 4 4.2v 2.2 Ah cells gives 8.4v and 4.4Ah). Over time each cell will end up in a slightly different state of charge and discharge as they are effectively tubes of chemicals, where no two are exactly identical. This minor difference grow over time such that eventually you will have a cell at say 70% charge while the other is at say 40% charge. The charger juices each cell evenly and doesn't monitor temp or enable the cells to balance.

Eventually you'll get overcharged and under charged cells leading to a cell failure. It is this that will dramatically shorten the pack's life, not the overall life of each cell. Ideally you want separate charge and discharge circuits (or at least a balance circuit), but the chargers cannot deal with this and it would increase the costs.

When your packs eventually fail or don't take a full charge, rather than replace them you could simply open them up and replace the weakest cells or even give them a good charge in isolation.

bails87

.blitz wrote:

The last mile home from the Chase is on a road and I ALWAYS put it on 100% :P

Really? Why?

Northwind wrote:

Aim's as important as power tbh. Pointed down-ish full power should be safe.

True, but I've always found level 2 to be plenty of power to illuminate the road surface and be seen, so don't bother putting it up to 100%?

Maybe I've just got good eyes?! There are some bits of my commute that I can do by moonlight alone

TownyDC

Well, I managed 4 hours of use before I needed to charge the batteries again but as I said the first 2 hours were on the higher levels as it was brand new and I wanted to show off.
Sunday night was out for about 1.5 hours, ran it on low to middle range for most of the ride, which again is great combined with a hope 1 vision on the bars.
I reckon toggling up and down the levels will get me 3 rides before I recharge it.
Really pleased with the light, i'll see where i am with it this time next year.

Dave

.blitz

bails87 wrote:

Really? Why?

Absolutely no-one pulls out in front of me - in fact most car drivers wait at the junctions to see what it is that is so bright and moving so slowly

bails87

Hmm, I'd be very wary of pi55ing people off, depends on the individual road though. I've had a few bikes come the other way when I've been cycling or driving and I've been completely blinded by them, as bad as a car leaving it's main beams on.

.blitz

Peeing people off? Not in Stafford Bails everyone is very polite - after you, no you first, no you first I insist, are you sure, yes age before beauty hahaha, oh thank you very much, isn't it a lovely day

etc etc

bails87

.blitz wrote:

Peeing people off? Not in Stafford Bails everyone is very polite - after you, no you first, no you first I insist, are you sure, yes age before beauty hahaha, oh thank you very much, isn't it a lovely day

etc etc

.....I've been to Cannock..... :shock:

.blitz

So have I

diy

Don't forget the human eye/brain works much the same as camera lens, the brighter the light the narrower the aperture and the deeper the depth of field. The deeper the depth of field the harder it is to judge speed and distance.