From GpsWiki
Power FAQ
What kind of batteries can I use in the PN-40?
You can use disposable AA batteries, either alkaline or lithium. You can use rechargeable AA NiMH batteries. Or you can use a rechargeable RCRV3 Li-Ion battery pack.
How does the PN-40 know what kind of batteries I installed?
It can auto-sense alkaline and Li-Ion. You must manually set up for other types. Even when using alkaline or Li-Ion, you should verify the setting whenever you change battery types. Menu->Device Setup->System->Battery Type. In order to get maximum possible run time, the correct battery setting is very important.
Which type of battery is best?
- Lithium disposables last longest, are light weight, and work well in cold weather. However, they are expensive and contribute to the landfill. Many people use rechargeables but carry lithium for backup, and for use in cold weather.
- Normal alkaline disposables are relatively cheap and convenient. But they provide the least runtime and contribute to the landfill.
- NiMH rechargeables and the Li-Ion pack provide more runtime than the alkalines, but less than the lithiums. In the long run, they are more economical than disposables and do not contribute to the landfill. They don't perform as well as the lithiums in cold weather.
OK, but how many hours on a set of batteries?
This is hard to predict since it depends on the conditions (particularly temperature), personal preferences (backlight settings, north up/heading up, zoom level, etc.) and battery capacity. //Very// roughly (your mileage may vary):
- Alkaline disposables -- no more than 5 or 6 hours, if that.
- Li-Ion rechargeable (DeLorme travel pack) -- 5 to 7 hours.
- NiMH rechargables -- 8 to 10 hours.
- Lithium disposables -- 11 to 12 hours.
What can I do to extend the battery life?
- Put the unit in power saving mode. Menu->Device Setup->System. Under GPS settings, select Power Saving. This turns off the backlight, steps down the processor speed and disables WAAS. It does not affect track logging. The device "wakes up" when you press any button. The most noticeable side effect is slower map drawing.
- Minimize backlight use.
- Do what you can to minimize map redrawing. Use North-up. Zoom out as much as possible. Better yet, leave the unit on the trip info page if you don't need the map.
Can I recharge batteries in the PN-40?
The PN-40 will recharge the Li-Ion pack when connected to the computer or to a 12-volt vehicle power source. The Travel Power Kit from DeLorme also includes an AC charger. The PN-40 will not recharge NiMH batteries. If you use NiMH frequently, you may want to invest in a smart charger.
Where can I get a suitable RCRV3 battery pack?
Officially, you should only use the pack provided by DeLorme. Packs purchased at retail may not fit the unit since the battery compartment also accommodates AA batteries. Unofficially, forum users report good results with a third-party pack designed specifically for the PN-series. More information is available here.
Does the unit use battery power when connected to the computer?
Not by default. You can control this behavior through device setup. Menu->Device Setup->System. To power the device from the USB connection while connected to the computer, set USB Power to Enabled. To use battery power while connected, set to Disabled.
The PN-40 gave a low battery warning. Why aren't the batteries really dead?
The PN-40 gives you an "early warning" so you will have time to change the batteries without losing data such as your track log. To decide when the batteries are nearly dead, the unit uses a voltage profile which is specific to the battery type. Individual batteries don't necessarily match the profile exactly. The unit is being conservative in detecting end of battery life, so the batteries will have some residual life. Also, the batteries may briefly recover when removed from the unit. Because the PN-40 sometimes fails to power on after battery exhaustion (see below), it's a good precaution to heed the low battery warning and change batteries at that time.
Why won't the unit shut off? When I press the power button, it just reboots.
You're holding the power button down way too long. To power down, press the power button //briefly// and when prompted, press Enter to power off. Press Quit or wait 5 seconds if you didn't mean to power down. Holding the power button for about 2 seconds invokes backlight adjustment mode. Approximately 3 seconds temporarily turns the backlight off. Approximately 7 seconds resets and reboots the unit.
How much power do various features use?
The following figures are courtesy of HorseTrailRider. All figures obtained using a bench power supply delivering 2.57V to the battery terminals (typical voltage of Ni-MH batteries).
| PN-20 | PN-40 | Conditions |
| 155 mA | 200 mA | GPS On, 0% Backlight |
| 167 mA | 214 mA | GPS On, 20% Backlight |
| 180 mA | 228 mA | GPS On, 40% Backlight |
| 194 mA | 244 mA | GPS On, 60% Backlight |
| 202 mA | 260 mA | GPS On, 80% Backlight |
| 220 mA | 274 mA | GPS On, 100% Backlight |
| 124 mA | 155 mA | GPS Off, 0% Backlight |
| N/A | 200 mA | GPS On, Compass and Barometric Sensors Off |
| N/A | 202 mA | GPS On, Sensors On, SD card installed |
| 157 mA | Power Save Mode, Tracking, 0% Backlight, Sat Page |
NOTES:
- The PN-40 uses the same amount of current in Normal Mode whether position fix is No Fix, 2-D, or 3-D.
- While the screen is being redrawn, the current jumps from 200mA to approx 240mA in Normal Mode, and jumps from 157mA to approx 170mA in Power Saving Mode.
- Since the PN-40 uses a switching power supply, current varies with voltage. Voltage varies according to battery type and charge condition. However, the PN-40 typically uses about 520mW (200mA x 2.57V). The PN-20 typically uses about 400mW.
I can't power my PN-40 on! What can I do?
The PN-40 seems prone to an often-reported problem of not powering on. This seems to happen most frequently after powering down when batteries are exhausted, possibly not having enough power to complete the procedure properly and consequently crashing. It may occur in other circumstances. Regardless of the cause, the symptom is a failure to power on despite using known-good batteries, or even connecting to external power. Often times this can be recovered from by pulling the batteries and letting the PN-40 sit overnight, although a much quicker process accomplishing the same effect is to pull the batteries and hold the Power button down for 45 seconds. Reinstall batteries and power on. It is believed that both processes drain a capacitor to fully power down, allowing the PN-40 to reset.
If this does not solve the problem, contact DeLorme Tech Support.
Should I take the batteries out when I'm not using the unit?
No. It is true that the unit draws a tiny amount of power even when it is off. The power is used to run the clock. If you remove the batteries for a long time, the clock stops. When you next try to use the unit, it will take a long time (perhaps as much as 5 or 10 minutes) to acquire a fix. The annoyance is not worth the very, very small addition to battery life.
What does power saving mode do?
In a nutshell:
- Disables WAAS
- Limits backlighting to 10% for 15 seconds
- Slows the processor, which increases redraw times
CPU speed reduction does not kick in until 15 seconds after the last button press, so the unit remains responsive when you are actively using it. Other than the loss of WAAS, there is no decrease in accuracy. There is no effect on track logging.
