duffer1960

[This original post was made in 2009. It's nine years on & I found it when searching. Made an update post, below.]

I bought a CygoLite Rover II. It's on its way now.

Already I'm thinking of getting a bigger battery. The NiMH water bottle battery it comes with is only good for 2 1/2 hrs on high. My max night ride is about that long, maybe longer sometimes. The battery is 4.8 V. Don't know the mAh capacity. The light is a 255 lumen total two LED. I think I read somewhere the battery is about 2500 mAh but I can't find that reference now. Does that square ( 4.8 watts ~= 255 lumens) ? EDIT - In another thread I see 1 watt ~= 40-50 lumens, so this is about right.

Question for the board: Is it OK to assemble a 4 x D cell (~ 10000 mAh) 4.8 V NiMH and just plug it in to the CygoLite? Would this give me about 10 hrs if it's a typical ~250 lumen LED light?

Question II: Does batteryspace.com give good service and sell good stuff? Will the batteries & charger last as expected?

Thanksalot!

-Duffer

bicycleflyer

Can"t help you with your technical question, but FWIW I have used batteryspace.com and have been very happy with them. I wouldn't recommend you use Alkaline batteries. They don't handle the higher loads very well. In addition when the temperatures start to fall their reliability drops to zero. But if you plan to use a rechargeble D-cell, then I would say go for it. What do you have to lose. Even if it is a miserable failure, you will have learned something. You should see the shoe box I have of my "failures".

Also take a look on ebay. There are several dealers selling water bottle batteries that are Ni Cad, NiMH, and Li Ion that have higher mAh ratings and thus longer run times. Take your pick which kind of battery you want.

duffer1960

Yes, thanks for the recommendation for batteryspace. NiMH cells for sure. Going to get an extra set & also use them in a radio. Wondered whether the batteries were really good for "500 cycles" as claimed, and whether the smart charger was really smart enough not to kill them young.

Specifically, if the 'smart charger' detects negative delta V, has two settings 1 A and 2 A, and recommends changing between 1 A for batteries < 2000 mAh and 2 A for > 2000 mAh... will it have a problem detecting (a slower to change?) -dV for a 10000 mAh pack?

EDIT - OK so I've been inspired to google for answers - here's an interesting site - https://www.powerstream.com/NiMH.htm. Says -dV is not reliable. Says charging efficiency is typically ~66%. (1.5 Ah of charging gets 1.0 Ah of charge). Also says if charging at <= C/10, don't have to worry about overcharging. So I'll get the 600 mA charger ( =C/17 for 10000 mAh D cells ), and charge for over 24 hrs or so w/o worrying about overcharging. Is this OK?

Edit 2 - I got over the fear and cracked open the water bottle battery case. There is a 4/3A x 4 battery pack in there. These are marked '2500 mAh' while at batteryspac*.com the new 4/3As are good for around 4000 mAh. So I'm not sure how many mAhs are actually there, but I'm sure that AAs will work well enough, given that NiMHs are happy giving current at least up to C/1. Connector looks like a 'Mini Tamiya' with female pins male housing. I've ordered two 4xAA holders and two connectors and 12 new NiMH AAs, already have a smart charger for AAs. I'll be ready for a much longer night ride than I can imagine doing.

Edit 3 - It's a nice light. '255 lumens' or whatever, it's more than enough for me. I haven't challenged the battery enough yet to know if it's good for the claimed 3 1/2 hrs.

duffer1960

Update after nine years of light-duty use. I use it on a 20 minute commute about 1/2 of the year. Just broke it out of storage for the dark season. Fully charged the original battery, turned it on. Ran for 2 hours 20 minutes on the normal brightness. According to what's written above, the batteries are still near their rated capacity of about 2500 mAh.

I did make 4*AA NiMH packs for this, but only ever used them to test them. (I thought I'd ride more but have not). The light when running on normal brightness gave the low battery signal immediately. The holders I bought had small-diameter lead wires, which may have caused enough voltage loss to light up the low-battery warning light.

Warning for anyone wanting to hack these. The mini-Tamiya connectors for the battery pack to bottle lead connection are wired in reverse polarity vs. the info I ran across when I ordered them. Verify polarity before hacking.

I see new lights with about twice the brightness, with the same or better run time, with USB automatic charging, are available for around $50. Even less if wanting to go cheep. Still, this will be good indefinitely with fresh set of 4*AA NiMH, as long as I don't mind the low-batt warning. But I don't have to worry about that yet. The original, nine year old batteries are still good!