I don't know how many parts this will be all together, but writing up a guide to getting a solar power kit together is something I've been meaning to do for a while.
In today's instalment, we'll be looking at how to prepare for a trip.
This is really intended for fieldworkers who don't have ready access to power in the field. But the information is still useful if you're using the battery from a truck, or a petrol generator. With fieldworkers increasingly carrying larger and larger amounts of digital equipment into the field, access to juice in a low power situation becomes critical for day-to-day fieldwork. I'm an advocate for recording everything too. If you're recording digitally, and you've got enough storage space, why not?
First of all, this is a rough guide. And I'll try not to delve into the technicalities too much. Second of all, if I've made a mistake, please let me know! I'm not an electrical expert.
OK, so you need to gather all your equipment together. Everything, from your torch to your video camera. Work out (a) what needs AA batteries or similar, and (b) what must be plugged in to a wall socket to work.
For all the (a) items, you need to test whether they work with rechargeable batteries. Rechargeables have a lower voltage than the disposable (usually alkaline) batteries you buy at the store. This means that if the device you're putting them into isn't expecting rechargeables, then it either wont work, or the batteries will seem to drain much faster. Mag-lites, for instance are designed to work only with alkaline batteries. Some digital cameras are designed specifically to work with either and will have an option to switch between them (make sure you set this option too, or you might find your camera suddenly switching off!). The Marantz and Nagra audio equipment that we use at PARADISEC are designed to work with both, and the Nagras have an inbuilt charger (which is great, it'll help you cut down on equipment). If you're going in to the field for a long time you will probably need extra batteries for your mic. If you're using rechargeables in your mic, make sure that it runs properly on the lower voltage! In the end it's often easier to carry in a few high capacity disposables for the mic, as they consume power very slowly. For torches, many LED based ones work well with rechargeables. Read the back of the box to check. When purchasing rechargeable batteries, spend a bit of extra money to get the good ones. The best power-to-weight ratio battery is the Nickel Metal-Hydride (or NiMH) type batteries. Well, it's not the best, but of the common types of rechargeables its the best. Their capacity is measured in milli-amp hours (or mAh's): the higher the better. As of writing this article, ~2400mAh is about the best you can get. Beware of cheap brands! Charge and use your batteries before you head out... sometimes there are duds.
For all the (b) items, the situation is a bit more complex. Our solar power system is going to work exactly like the cigarette plug in your car. So you have two options. Find a cigarette lighter adapter for each device, or purchase an AC-DC inverter like this one. Inverters come in different sizes. Choosing the right one will be a topic in the next part of this series, on estimating your power consumption.
Generally speaking finding a cigarette lighter plug adapter is going to be more efficient than using an inverter. Also, the total weight of the power adapters and the inverter is probably going to be heavier than the cigarette lighter plug adapters. If you can't find an adapter, try heading into a jaycar or similar hobby electronics store and see if they can help you. Jaycar sells an excellent multi-purpose adapter, which can really cut down the number of adapters that you take, but you must be careful with these as its a quick way to destroy your equipment if you don't know what you're doing. Roughly speaking, you can use an adapter with devices that have a "DC IN" plug on the side. Again, ask at the store. To get an adapter for a laptop, you'll probably have to go somewhere like this too. For battery charging I recommend a slow charger, these will ensure that your batteries are charged to absolute capacity.
So at the end of all this, you need to test everything! It would be terrible if you ended up in the middle of nowhere with critical part of your power chain not working. Of course, we don't have a full set yet, so you can't really test it. Before you purchase your solar panel(s) you need to estimate how much power you are going to use every day... to be continued!