Lights various

flecc

Member
Oct 25, 2006
45,940
22,582
JohnInStockie has Derrick. Here's the link to his posting on these:

Reelights

The thread has lots of added details.
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derrick7

Pedelecer
Aug 22, 2007
107
0
Llanberis LL55 4TD (Snowdonia)
Lights various pt2

Having read all the info. on Reelights I have decided not to buy them, but I have 19 D cells from my old Lafree battery (assuming it was just 1 cell that caused it's premature end) & will have to design a system that can make use of some of them.
Anyone got any ideas?

Derrick - Llanberis
 
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derrick7

Pedelecer
Aug 22, 2007
107
0
Llanberis LL55 4TD (Snowdonia)
Brainwave

I have 20 cells, all separated (I have prised the links off) from my old Lafree battery & I presume one cell is a dud, I also have a redundant Windsor case, because I took the battery pack out of it to re-cell my Lafree. The way the Lafree suddenly faded, 23 miles one week 4.5 the next would point to that.
How can I determine which is the dud cell (if that's the case) & if so can I buy a new cell similar ( in capacity) to the present healthy cells & make up a battery pack & fit it into the Windsor case?
I am retired so I have lots of time but little money & it wouldn't cost me much; do you think it's worth a try?

Derrick - Llanberis
 

flecc

Member
Oct 25, 2006
45,940
22,582
Normally a cell that has failed in this way will have a markedly lower voltage than the rest, so measurement with a meter usually shows that up.

Adding a new cell to an existing chain in series will often lead to failure, and the older the existing cells, the more likely that is. NiMh battery manufacturers take care to only include cells from one manufacturing batch in each pack, and the best manufacturers/suppliers always select the cells by matching before assembly. The major US supplier Batteryspace came unstuck in this way by failing to do that and getting a bad name for failures. They now do select for matching and their prices have shot up as a result.

So what you're proposing is not recommended.

I have added cells to existing packs in some limited circumstances with both success and failure, so if you do still try this, here's some tips.

Estimate the capacity of the existing cells by calculation from their age. At about three years old, well looked after cells will have around half the original capacity as a guide. Then use a cell of the same estimated capacity.

Before adding the cell, precharge it to the same measured voltage level.

Then make the first pack charge a short part charge, and use the pack for a short while only, never to empty.

On the second charge/discharge, extend those a bit further.

Then use the pack normally. By following that procedure throughout you stand the best chance of bringing the cells all up to a matching balanced state. It's imbalance that can result in reverse charging of one cell by the others, with sometimes disastrous results.

P.S. Alternatively you could just use the 19 cells as an extra pack to extend range, using wired connections. When new and freshly charged, a 24 volt pack will reach around 29 volts, and when discharged, 24 volts. Your 19 cells fully charged will reach, depending on age, around 27.5 volts, so still able to drive the Lafree for some distance before voltage drops to cutout level.

One user who has added a range extending battery in a similar way using a Powacycle pack is pedelecs member "Grandad", and his mod is described here.
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Branwen

Pedelecer
Oct 2, 2007
97
1
Has anyone had any exprience of the Reelight system advertised on Bikefix - the bike shop on your desktop
My Lafree has a bottle dynamo, which does the job, the two problems with it (as most of you will know) is the drag & when you stop so do the lights.

Derrick - Llanberis
I had to have the dynamo removed from my LaFree in the end as it was too problematical, but I am missing the brightness of this light now I have to cycle through an unlit park to get home. I have the brightest battery powered light I could find, but it still seems inadequate. I saw a 10KW bike light that comes with a rechargeable acid lead battery for £35 but dont really know if it is suitable. Maybe else knows?
 

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