Powering Your Resistograph

The Ni-Cd Alternative:

After using a Resistograph in my business for a year Ive found myself frustrated with the standard 1.7 AH, Ni-Cd battery pack. The Ni-Cd batteries frequently die while I am drilling. Installing a fresh battery is simple enough but I wonder how the drop in power, just before the battery dies, effects the reading. When freshly charged I get between four and five drillings depending on wood density and drilling depth. For most of my work, two batteries are not enough and waiting an hour to recharge a battery is inefficient. While the rapid charger significantly reduces charging time, where do you plug it in? If you use a 12 volt to 120 volt converter and the rapid charger to charge batteries in your car, recharging to many Ni-Cds could leave your with a dead car battery.

Oliver Hein, General Manager of IML-USA, suggested that I purchase the adapter connection cable (available from IML-USA) and use a motorcycle battery to power my Resistograph. Since lead-acid batteries are heavy, I had to think about the versatility of this option. At first, the thought of lugging a heavy battery around was about as appealing as carrying a boat anchor and lets not forget the potential for acid spills. After all, motorcycle batteries are lead acid, just like your car battery. Considering all the positive and negative aspects of this option I had an idea. I could put the battery in a padded camera bag and carry it over my shoulder with relative comfort (see Photo 1 & 2). This solution seemed to offer the best balance between power and freedom of movement. Besides, I could always set the bag on the ground and take advantage of the nine foot long adapter connection cable-no extra weight to carry. Now all I needed was a sealed lead-acid battery.

Finding the Right Battery and Charger:

I began my no leak battery quest at the local Sears Automotive Center. While their sales people were very knowledgeable all their 12 volt batteries, even the sealed variety, had the acid packed separately. This means the batteries have caps you must remove to add the acid and caps have the potential to leak. Next I went to the Interstate battery distributor and talked to an expert. After I described how I was going to use the battery, he showed me a variety of 12 volt batteries ranging from 6 - 18 AH. Best of all these batteries are truly sealed-no caps, no leaks. I chose the 18 AH, PC12180NB. This battery weighs twelve pounds, is 6.5x7x3 inches (HxWxD) and fits perfectly into a small camera bag. Actually I purchased two of these batteries so I would have a spare for big jobs. The batteries come with hardware for attaching different types of connectors. To allow for quick batteries changes, I replaced the connectors on the adapter connection cable to slide on, female blade type. I then attached the male connectors with nuts, bolts, and washers (all supplied with the battery) to the battery posts.

In the Field:

I already had a Lowepro ®, Mini Mag camera bag for carrying the battery. To cushion the load, I replaced the camera bags standard shoulder strap with an Op/Tech ® bag strap. In the field this setup is working great. My movement is unrestricted and the weight of the battery, on my left side, balances the weight of my Resistograph which I operate on my right. The continuous flow of power is a welcome relief as well and 15 drillings only depletes the battery reserves by about half.

Battery Care:

If you decide to get the adapter connection cable and a battery, what follows should be helpful. To charge your lead acid battery you will need a trickle charger. Sears has a great selection with prices starting at $20.00. The best model I found was the 6/2 Amp, 12 Volt charger, #71206 for $30.00. This charger is the least expensive model with an Amp meter, a nice feature to have because it indicates the level of charge on the battery. The 71206 also allows you to switch between 2 or 6 Amp charging rates. This is important because lead acid batteries rated between 6 and 18 AH should be charged at the slower 2 Amp rate. Because of their grater capacity, lead acid batteries do take longer to charge. You can expect 1 hour of charging time for every 2 AH of capacity. This means that an 18 AH battery, will take up to 9 hours to recharge when nearly exhausted. Unlike Ni-Cd batteries, lead acid batteries dont have a memory problem so they can be topped up (charged) at any time. In fact lead acid batteries love to be charged, just like your car battery. With Ni-Cd and Ni-Mh batteries, its best to run them until their totally dead. Dont do this with lead acid batteries because they may become damaged after a total discharge. Its unlikely you will do that, however, because as the power gets low you will notice a reduction in the Resistographs drilling speed.

Conclusion:

While the setup describe above, has made my work easier, dont throw your rechargeable batteries away. You wont want to carry that 12 pound battery into a tree if you need to test a branch.

Your needs may vary so be innovative. However, if your intrigued by what youve just read, here is a list of resources to help you get started.

Interstate Batteries: http://www.interstatebatteries.comfor dealer locator. The battery I purchased was the PC12180NB priced at about $40.00.

Planet Battery: http://www.planetbattery.comsells a variety of sealed led acid batteries through the internet. Their # 718069 (PM12180F2) is similar to the interstate battery I purchased and sells for $48.00 plus shipping.

Camera Bags and Op/Tech ® straps are available at many photo retailers and by mail order. The Lowepro ® Nova Mini is similar to the bag Im using and other brands may work just as well. B&H Photo and Video http://www.bhphotovideo.com is a good source for photo related equipment.