Sealey BT102
Unlike most of my off-grid contemporaries, my storage bank is a rag-bag assortment of old car batteries. Not for me the neat shiny row of brand new, deep-cycle, perfectly matched accumulators. Mine came from old cars, were donated by friends and even found left in a car park. They all work though, more or less.
And that’s the problem, some work better than others. Testing them though was a problem. Attaching a 55 watt headlight bulb shows that the battery will hold a charge and deliver a few amps of current. But to check the capacity, the bulb needs to be left there, certainly for hours, possibly for days and constantly monitored. Impractical, to say the least.
So step in the Sealey BT102 Battery Tester. This is a convenient little device which gives a very quick and apparently accurate indication of the condition of the battery.
Start by connecting the battery clips to the battery terminals and the 4 digit LED display initially shows the battery voltage accurate to one hundredth of a volt. Press enter and you can input the battery type and Cold Cranking Amps (CCA) in either SAE, DIN, EN, IEC or CA. The test runs and instantly shows the actual measured CCA and a good/bad assessment on red, yellow and green LEDs. By comparing the measured CCA to the value printed on the battery label you get an idea whether the battery should be kept or discarded (recycled).
Nothing is said in the instructions about how the tester actually works, but I get the sense that the device has been well designed and I’m inclined to trust it. An LCD rather than LED display would have better as the display is difficult to read in bright daylight, but this is a minor gripe really.
So I’ve used the BT102 to weed out a couple of poorly performing batteries and satisfy myself that the rest are still usable.
The tester has no internal battery as it uses the battery under test to power the electronics.
LED Lenser M5 Torch
There’s something rather satisfying about turning harvested sunlight back into its native form, and an LED torch is one of the best ways to do this.
I’ve standardised mostly on AA rechargeables to store energy outside of my lead-acid battery bank, so my choice of torch reflects this.
The LED Lenser M5 torch uses a single AA cell, stepping the voltage up internally to power the LED. This works well, although as the cell becomes discharged, the microcontroller functions can become erratic.
The M5 is exquisitely small. It’s about as small as it could be, given that it has to house an AA battery, a microcontroller switch and a LED with focusable lens. It’s substantially smaller than LED Lenser’s other 5 series (single AA) torches; the P5, T5 and the bulky L5.
The variable focus lens is a joy to use. It slides forwards a few millimeters to focus the beam into a bright square spot. The square shape is a reasonably well focussed image of the LED itself, in fact you can almost make out the connecting wires. Slide it back for a large clean circular flood beam of light, ideal for finding your way round the house at night.
The microcontroller functions are sensibly simple. There are 3 modes; bright, dim and strobe, the latter useful for dazzling hostile assailants (particularly those with photosensitive epilepsy). Dim is similar to strobe except that the rate of switching is faster – too fast for the eye to see. When you wave the torch from side to side in dim mode you can see the switching process quite easily. In bright mode, the LED pumps out 108 lumens, apparently.
So how bright is 108 lumens? It’s not something that can be easily described… Certainly do throw away that nasty old torch which uses a 3 volt bulb and a couple of C cells, but don’t gouge out you car’s headlights and replace them with LED Lenser M5s.
The battery lasts for an hour or two in bright mode and around 4 to 6 hours in dim.
This is probably my favourite LED torch. It’s bright enough for most tasks, easy to operate and requires just the one AA cell. It’s not the brightest LED torch available, but a sensible compromise between brightness and running time has been chosen, I think.
Wire straighteners
When the four lengths of red, yellow and black wire come off their reels, they have a considerable curl in them. I needed to find a way to lay them straight for a few days before production – it makes soldering them to the PCB a lot easier.
The solution is a set of panels of Corex, a fluted plastic board used to make estate agent ‘for sale’ signs. The wires lie straight, the curl is removed.
Click the image for a closer look.
So far, around 300 controllers have sold to locations around the globe. I’m keeping a list of countries that I’ve posted to. Here it is.
- United Kingdom
- Ireland
- Sweden
- Finland
- Denmark
- Latvia
- Netherlands
- Belgium
- Bulgaria
- France
- Switzerland
- Spain
- Portugal
- Italy
- Malta
- Malaysia
- Singapore
- Philippines
- Indonesia
- Australia
- Canada
- United States
and now…
- Greece
- Tahiti
- Austria
Electric cars are coming, slowly! Here are some thoughts about how the industry will develop.
Battery charging is not the whole story
Batteries must be replaceable as well as rechargeable. The idea of re-charge points in filling stations is frankly laughable. Waiting 6 hours for a fill up is nonsensical. Re-charge points in shopping centres make more sense. Charging batteries at home is fraught with problems. If there’s no off-road parking where you live, there’s no way draping live cables across the pavement will be acceptable. Even if you are off-road, you’ll want to be behind a gate if you’re to avoid problems with vandalism and theft of electricity. Charging at the work place will only be possible if your employer is willing to provide charging points and off-road parking.
Battery replacement is the only viable model for filling stations
Instead of a petrol pump, there will be a recharge wall. You’ll lift the bonnet, remove all the dead batteries with a simple twist and pull action. Dead batteries will have a red light. You’ll put the dead batteries into spare holes in the recharge wall. You’ll then take out the same number of charged batteries (with a green light showing) and put them in your car’s battery block. Then you’ll approach the kiosk and pay. This won’t take any longer than filling a tank with petrol.
Batteries will be a standard size and fitting
Large cars may have 48 or 64 batteries under the bonnet, small cars may have just 16. For filling station recharge walls to become commonplace, standard sized batteries are a must.
Batteries will be lithium based
Lithium is the lightest of the metals, lead one of the heaviest. Lead-acid is fine for fixed, non-mobile installations. Lithium will be used for vehicles.
Batteries will be used sequentially
When accelerating hard, several batteries may be used simultaneously (in parallel). At the minimum throttle setting, only one battery would be in circuit. Once a battery is depleted, it would be flagged as empty by the power management system. The fuel gauge would use this information to indicate remaining power availability. Each battery would contain a microcontroller which would monitor state of charge and communicate that to the power management system.
In-wheel motors will prevail
By putting electric motors in the wheels, all the energy waste in conventional transmission components is eliminated. Electric cars don’t need a clutch, gearbox, prop shaft, differential or constant velocity joints. In-wheel motors can perform all the tracking and stability functions with suitable software. Four wheel drive, two wheel drive (and 3-wheel and 1-wheel drive for that matter) can be implemented easily.
The National Grid will need a major overhaul
If significant numbers of electric cars are plugged into the grid, capacity would be quickly reached. For vehicles charged overnight, rooftop solar would be of no benefit.
Road pricing is inevitable
If you’re able to charge your batteries at home, you can benefit from energy that is free of excise duty and is subject to VAT at just 5%. That’s very cheap energy. It will be difficult for the government to justify high levels of taxation on electricity provided at filling stations – people who can’t recharge either at home or at work will be unhappy. So the taxation model will have to change. Road pricing is inevitable.
Road pricing need not be very hi-tech
There could be a simple online or paper based form to fill in once a month declaring your mileage, coupled with an online payment system. When your vehicle is due for MOT, the mileometer reading could be cross-checked against your declarations. Not many people drive any significant distance off-road and toll road prices could be subsidised to compensate for their use.
It was always my intention to follow up the design of the PWM5 with a MPPT (maximum power point tracking) charge controller. But it hasn’t happened – for a number of reasons.
Firstly, there’s a simple economic argument. The 30% or so of extra power that MPPT squeezes out of a solar panel can be obtained another way – by buying a bigger solar panel. One will be cheaper than the other. Generally, the extra expense of an MPPT controller is less than the extra cost of a 30% bigger panel. But panel prices are coming down, so the situation may well change.
Secondly, from my point of view, an MPPT controller is a difficult thing to design. There are likely to be problems with reverse polarity protection, with RFI and the peturb and observe algorithms won’t be easy to write.
But MPPT has another benefit. The DC to DC converter functionality lets you use a 24 volt solar panel with a 12 volt battery. If there were ever a surplus of 24 volt panels, this type of charge controller would be very useful.
Rooftop solar in the UK is almost exclusively grid connected. If our electricity grid ever becomes unreliable (due to rolling blackouts or rationing for example), rooftop solar won’t fill the gaps.
How does the Powerex Maha MH-C9000 Wizard One Charger/Analyser compare with the Technoline BL700 Battery Charger.
Which is the faster charger? – The Powerex C9000 has a higher default charge rate, so if you just drop batteries in and don’t press any buttons, the C9000 will do the job much more quickly. However, you have to be careful – for many AAA cells (some are as low as 300mAh), 1 amp is an aggressive charge rate. The C9000 also has a higher maximum charge rate, so if you are in a hurry, this is the charger to use. At the maximum 2000mA charge rate, a set of 2000mAh eneloops will be ready in about an hour.
What happens if you don’t press any buttons? – Both chargers default to the basic charge algorithm. The C9000 defaults to 1A charge rate and the BL700 to 200mA. This makes the Technoline the safer of the two.
Which charger has the better feature set? The chargers really only differ in their multi-cycle modes. The C9000′s ‘cycle’ mode charges and discharges the batteries a specified number of times. The BL700′s ‘refresh’ mode charges and discharges until no more capacity can be squeezed out of the cell in question.
Which charger is easier to use from a 12 volt vehicle or solar power source? Definitely the C9000. That’s because the BL700 requires a 3 volt power supply so a vehicle power adapter is needed. The C9000 operates directly from 12 volts.
Which charger is better at terminating? I’d say they’re equally good. Both chargers do make the occasional mistake, but it’s by no means common, these chargers are streets ahead of cheap chargers in terms of accurate termination. Early termination is easy to spot – the float voltage will be unusually low and the mAh count will not be as high as you’d expect. Remove and re-insert the offending battery and the charger will finish the job.
Which charger handles flat batteries better? – The Powerex C9000 wins this one. Cells that are at or near zero volts aren’t detected by the Technoline and can sit in the charger indefinitely, with the display showing NULL. The C9000 is able to detect a completely flat battery and will apply a 125mA charge rate for as long as it takes to bring the cell up to voltage.
Which charger has the best display? – Neither and both. They’re very different. The C9000 has a large, brightly lit display that’s easy to see in the dark and from a distance, but only looks its best when viewed head on. Move your head even slightly above or below the optimum position and all the unlit segments become visible. However, it’s mostly filled with words and only has one 4-digit section for numerical data.
The BL700′s display is smaller and has no back illumination, but each battery has it’s own 4-digit data area so you can get
Which charger do I use most? – Probably the Technoline BL700. The default 200mA charge rate means it’s safe to drop any AA or AAA cell in and not worry about the best charge rate to use.
How could the Powerex C9000 be improved? – The C9000 is a top notch charger. Its performance, reliability and accuracy are all first rate. However it’s let down by its user interface.
How could the Technoline BL700 be improved? – The BL700 is a reliable, trustworthy and precise battery charger that, for the most part, just works. One thing I would take issue with is the 3-volt power adapter. A 12-volt input would make it much easier to use in a vehicle or with an off-grid solar power installation (which is of course my main area of interest).
Now rated at 100W
The PWM5 is now rated for use with solar panels up to 100 Watts. By upgrading the external diode (the one in the yellow wire) I’ve brought the maximum current handling up to 6 amps.
If you look at the label on the back of a 100 Watt solar panel, you’ll see Isc is around 6 amps. This is the maximum current the panel can produce under any load conditions and therefore the maximum current the panel can push through the charge controller into the battery.
24 volt system
I was asked recently if the PWM5 can be used in a 24 volt system. If the 24 volt battery is actually two 12 volt batteries (connected in series) then the answer is a qualified yes. Qualified because this can’t be done with a single solar panel. The diagram shows how it should be configured.
Two solar panels are needed, preferably identical, as are two charge controllers. In effect there are two separate systems here. Each battery is separately charged and monitored. This has the advantage that both batteries are optimally charged which isn’t necessarily the case if a single 24 volt charge controller is used.
Bootstrapping is the process of picking one’s business up by its own bootstraps, or in other words, using one’s own products or services to increase business efficiency.
My product controls the process of charging lead-acid batteries from solar panels which gives me free electricity. So to bootstrap my business, I need to use that free electricity to manufacture and market my product.
During manufacture I use various tools; soldering iron, glue gun, heat gun. Sales and marketing requires computers of course and there are a few other electrical devices used for product development and testing. How many of these could be switched to solar power rather than using mains electricity?
My soldering iron uses a fairly meagre 18 watts, so no problem there, and 12 volt soldering irons are available too. The glue gun initially draws a couple of hundred watts, but this quickly drops to around 15 watts after 10 minutes or so. More problematic would be the hot air gun at 1500 watts and the kettle (for pre-shrinking sleeving) at 3kW (although 1kW kettles are available).
I host my own website which until recently used a mac mini. At around 20 watts, this could be a difficulty as 24/7 operation is required. I’ve now moved it to a Qnap server which draws just 7 watts. My desktop computer uses around 300 watts, a pretty hopeless case for solar power. But a new iPod is helping, letting me check for emails before having to switch the computer on. The iPod has been charged using solar since day one.
It’s conceivable that this entire operation could be powered using solar energy although I’d need a dirty great inverter for the power tools (1500 watt pure sine perhaps) and quite possibly a few more solar panels.
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