I.R.I.S. QP-1800 - Manual (Page 20)

QuietPower 1800 Inverter Owner’s Manual Rev 15 OCT 01 Page 20
11. Appendix A. Technical Addendum.
Equipment Runtime
We have heard questions about a “short” operating runtime with this equipment. In field tests at Camp
Pendleton, we measured and verified conversion efficiency of the QP-1800 to be approximately 90%, well
within specifications. The QuietPower 1800 equipment, by its very design, can demand a large current
drain from the vehicle electrical system (75 to 90 Amperes depending upon battery voltage and load). A
high conversion efficiency means that it is not the cause for wasted energy.
We then inspected the HMMWV vehicle batteries and observed loose and corroded battery connections,
measured batteries to be “weak” or “dead”, and have seen low outputs from vehicle alternators. It is not
adequate to measure the voltage across the vehicle batteries in an unloaded condition. Lead acid
batteries recover to relatively high voltages even if they are weak or damaged. It is important to measure
the holding voltage across these batteries while loaded and typical battery testers do that.
To operate effectively, all connections within the vehicle electrical system must be clean and very secure.
The battery health is critical, too. In speaking with Exide, the manufacturer of the 6TL and 6TMF
batteries, the rated value is 100 Ampere-Hours (AH). That is to say that a 20 Ampere load should run for
5 hours (20 A x 5 H = 100 AH). This is a temperature dependent parameter, too, and Runtime v Load
data is provided below for varying temperatures.
Exide 6TL & 6TMF Runtime to Cutoff @ 10 VDC
0.1
1
10
100
1 10 100 1000
Amps
Hours
+80F
+32F
0F
-25F
-40F
-65F