Lithium Battery Primer
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Deployment planning with our lithium battery packs is simple. Use the same planning tools you would use with standard alkaline packs, but triple the planned duration. You can adjust this ratio up or down depending on how conservative you feel you must be with your deployment. If you have a good idea of the typical temperature of the instrument during deployment, you can adjust the duration accordingly. If you routinely implement similar deployments, you can monitor how much of your battery pack you deplete (see below), and adjust your planning according to your experience. Of course, feel free to call or e-mail us if you have questions.

Because alkaline packs exhibit wide variability, planning tools must be conservative--usually too conservative for lithium packs. While the design of these lithium packs is more complicated than the design of alkaline packs, the result is that the lithium packs perform more consistently than alkaline packs. The usable capacity of alkaline packs depends on the temperature and on how the energy is used (i.e. the size of the current surges drawn from the pack). Our lithium packs’ capacities also depend on these factors, but they vary considerably less than alkaline packs.

When planning deployments with our alkaline battery packs, treat them the same as you do your standard alkaline battery packs. Because we use Duracells in our packs, you will find that they have at least as much capacity as the standard packs, and you may find that they have more.

While it is not easy to tell in advance how conservative your planning tools are, your experience will enable you to obtain most of the capacity of your lithium packs.

Estimating how much battery capacity your deployment consumed

Figure 1 shows a normalized voltage profile that is typical for Tadiran lithium batteries. The interesting feature is the nominal 10% voltage drop about 80% of the way through the life of the pack. This voltage drop is a reliable characteristic of these batteries, and you can use it to forecast the ultimate capacity of the cell to within a few percent. Both Workhorse ADCPs and Nortek instruments record the battery voltage (the Workhorse records the voltage in one of its ADC channels), and you can use this to find the change in voltage. If you do not see the change, then your deployment has more than 20% of its life left.

Figure 1. Lithium battery voltage over the duration of a deployment.

Aanderaa current meters do not record the battery voltage, but you can use a volt meter to record the voltage after you start it up and again when you recover it to at least make a guess. The easiest approach may be simply to measure its voltage before you remove it from the instrument.

Ocean Batteries, 12344 Oak Knoll Road Suite E, Poway, CA, 92064
858-486-4077