Jonathan Gazeley

Building a bottle battery

If you read my blog, you’ll have seen my recent review of my RSP Asteri 2 bike lights. I talked about making a bottle battery, and now I have.

Unfortunately I forgot to take photos after the first couple of steps but never mind.

What you’ll need

I used the following parts, but you can use whatever you like.

Qty	Part	Notes	Store	Price
1	Bottle	I bought a PwrTek bottle for mixing protein shakes. It had a wide neck and an offset “spout”	ASDA	£4.00
2	D rechargeable NiMH 8000mAh 2pk	You can use any type you like. Check the mAh rating.	Maplin	£25.98
4	Battery holder	Optional. I just didn’t fancy soldering directly on the battery.	Maplin	£3.16
1	DC connector 2.5/5.5mm		Maplin	£0.99
1m	Single core cable	Should be flexible for use inside the bottle	Maplin	£0.69
1m	Twin core rounded cable	For use on the frame.	Maplin	£0.69
			Total	£35.51

A note on batteries

It doesn’t matter what kind of rechargeable batteries you use – NiCd, NiMH and Li-Ion are all fine.
It doesn’t matter what size of batteries you use. If you wanted to make a smaller “pouch” of batteries you could use C type.
You must have precisely 4 batteries in each series loop, but there’s nothing to stop you using 8 batteries and having two series loops in parallel.
The capacity (measured in mAh) is an indicator of how long the batteries might last.
- The batteries that come with the RSP Asteri 2 are AA NiMH batteries; 1600 mAh each. The manufacturer reckons you can get 1-2 hours on full power and 6 hours on flashing.
- Inexpensive D type batteries might give you around 3000 mAh, which immediately doubles your battery life.
- My D type batteries give a claimed 8000mAh. Scaling up the manufacturer’s estimate, I might be able to get 5-10 hours on full power, or 30 hours flashing. This basically gives me the ability to do a week’s commuting on full power without recharging until the weekend.

Building it

I cable-tied the battery holders back-to-back as they happened to have holes in the right place. A pair of D batteries just about fitted through the neck of the bottle if I squeezed the bottle. I attached the batteries in two pairs so they could sit on top of each other.

I soldered the battery holders together in series using the single-core wire. I used fairly long stretches of wire (about 8″) between the upper and lower pairs of batteries, to make it easier to feed the batteries into the bottle.

I taped up the exposed solder with insulating tape so there was no chance it could make a short circuit if the batteries moved around once in the bottle. I packed the batteries into place with bubble wrap so they wouldn’t rattle and risk damaging the solder.

At the neck of the bottle, I terminated the two single cored with a terminal block and connected the twin-core cable to the other side. I threaded it through the spout of the bottle and screwed the cap on. The terminal block also allows you to easily reverse the polarity of the circuit if you accidentally wire it back to front for your LEDs. 😉

I measured the trailing cable to make sure I had the right length, before trimming it and soldering the DC power connector on the end.

The screw cap seemed tight and waterproof so I left it alone, but I plugged the gap around the cable through the spout with hot-melt glue gun.

The batteries I bought claim to come fully charged so I was able to test it immediately. Which brings us on to our next section.

Recharging

Obviously it’s going to be a bit of a pain to remove the batteries to recharge them, so we will charge them through the neck cable. Buy a female DC socket to match the plug you bought for the bottle battery. Also buy a female connector to match the RSP charger’s plug. Solder them together and ta-da! You have an adapter cable to connect your battery to the charger. Watch the polarity here, or you might set fire to your house.

If you don’t want to take the risk of breaking your original RSP charger, any DC power supply capable of supplying 7.5V with at least 300mA should do the trick.

Considerations

The original RSP battery had a warning LED for low battery. You don’t, so be careful you don’t over-discharge the bottle battery or you might damage the NiMH cells. As soon as the LEDs start to go dim, switch them off. You would, of course, be wise to keep a regular battery light in your bag in case of emergencies. I keep a small Cat Eye HL-EL510 for situations like these.

The original RSP battery had automatic charging shutoff when it was full. You don’t, so be careful not to overcharge the batteries. Probably 12-18 hours will be enough. Check the instructions that came with your batteries.

You can get around both of these considerations if you pilfer or copy the PCB in the top of the original RSP battery pack. Again, depends if you are willing to sacrifice your original battery pack, and if you can be bothered with the effort.

Autumn sunset

Autumn this year seems to have brought with it some fantastic sunsets looking south from Kingswood, Bristol.

I would like to point out that the colours of these photos have not been enhanced on the computer. What you see is exactly what I downloaded from the camera.

A weekend in Hereford

Hannah and I went to Hereford this weekend. The weather was nice, and we had a really nice time relaxing. I managed a few photos too. The golden Autumn sunlight cast a lovely glow over the city.

First we visited the cathedral. It seemed rude to take photos inside, but I managed this photo of various roof decorations from outside.

Walking in Castle Green, I spotted this dandelion.

Victoria Bridge leads out of Castle Green, across the River Wye.

Hereford’s famous Wye Bridge.

Some more distants shot of the cathedral, seen from across the Wye.

Photoshop disasters

In the past, I’ve enjoyed reading Photoshop Disasters. Today I was delighted to spot my own Photoshop Disaster in Dorothy Perkins.

Looks to me as though they’ve just chopped her fingers off to resemble pockets.

Halifax

I have a secondary current account with Halifax, which I use for paying bills and rent.Today I received a letter from them. Here’s an extract:

From 6th December 2009 we’ll no longer be paying the 0.1% AER/gross interest we pay you on the balance in your account, or charging you debit interest on any overdraft you use. Instead, we’re introducing new, simple and easy-to-manage overdraft fees.

If you use an arranged overdraft up to £2,500, we’ll charge you £1 a day

If you use an arranged overdraft over £2,500, we’ll charge you £2 a day

If you use an unarranged overdraft, we’ll charge you £5 a day

We won’t charge you any interest on an overdraft, whether it’s arranged or unarranged.

I’m no financial expert and I’m sure Halifax have their reasons for implementing this policy. But to your man off the street, the expected way that banking works is quite simple.

You are rewarded for saving with a bank
You are penalised for borrowing from a bank

By these rules, it seems that Halifax have increased their penalties and totally stopped their reward. So there is now no incentive to have a current account with Halifax. My account is almost never in overdraft but I don’t wish to be charged £5 every time my broadband company sends a larger-than-expected bill. I also don’t wish to go without my 0.1% interest, as a matter of principle.

Surely they realise that people will flock away from such a proposal? I for one plan to close my account immediately and move it to a different bank. No doubt a run on the bank will cause them to collapse, and demand a bail-out from the government, but oh well.

Various Nagios plugins

I’ve now written several Nagios plugins and submitted them all to MonitoringExchange.

Here’s a quick summary:

check_temper for monitoring the temperature with a TEMPer USB thermometer
check_kernel for checking that the currently running kernel on an RPM-based system is the most recent installed kernel (not necessarily the latest available kernel in the repository)
check_aql_balance for monitoring the number of SMS text message credits on your AQL account^[1]
check_k8temp for monitoring the temperature of an AMD K8 (e.g. Athlon or Sempron) CPU

[1] See my blog post if you are interested in setting up SMS alerts with Nagios

A short walk at sunset

I love the odd colours and coarse film grain in this shot of Cossham hospital. I think it looks rather retro.

Some 35mm macro shots

I took these photos with a 35-70mm lens, using an additional macro lens.

A pink lily

Cotton reels

A crystal of aragonite

Unfortunately the developing lab treated my negatives pretty badly, as I wrote about on my blog earlier today. Here’s a close-up of some of the scratches on the second aragonite photo, which I think are really distracting.