Converter 110 volt Input Current

Very much appreciate everybody's input!

Although everything appears to be operating just fine in my TT, I did some further checking of the battery and converter voltage/current in my TT just to satify my own curiosity. I'm no electronic whiz, so feel free to correct or comment.

First off, I incorrectly stated my 12 vdc lighting load in my original post. It's much higher than I realized (Salvo, your post got me thinking, thanks!). My TT uses 12 vdc 921 bulbs, which I believe are rated at 1.4 amps each. About 6 or 7 921 bulbs (approx. 9-10 amps 12 vdc) are wired to each light switch. Switching on one light switch (with the converter ON) forces the converter's 110 volt input current to increase approx. 2 amps as shown by the PI EMS (Progressive Industries - Electrical Management System). Switch on a second bank of lights and the converter's 110 volt input current jumps up another 2 amps, total 4-5 amps. With two banks of lights on (assuming 1.4 amps per bulb) total 12 vdc current should be approx. 18-20 amps.

For comparison, I put a maximum load on my 600 watt PSW inverter (rated at 650 watts for 20 min.) with a 650 watt coffee maker. With the converter OFF, using a freshly charged battery (12.75 volts), and the coffee maker running (650 watt load on inverter), I read 11.9 volts on the battery terminals. With the converter ON, a freshly charged battery (12.75 volts), and the coffee maker running (650 watt load on inverter), voltage at the battery read 13.5 volts. During this test, the converter's 110 volt input current ramped up to 15 amps (only rated at 12 amps!!) as shown by the PI EMS.

I believe the inverter with a 650 watt 110 volt load is drawing approx. 65 amps, 12 vdc. The converter 110 volt input current increases to 15 amps to support the dramatic increase in 12 vdc load. On the other hand, turning on 18-20 amps of 12 vdc lighting forces the converter 110 volt input current to increase from 0-1 amps to 4-5 amps. The increase in current (12 vdc and 110 volt) in both scenarios (inverter vs. lighting) appear proportional and would seem to indicate the converter is operating properly. Everyone agree?

Additional info/comment: With the battery fully charged (12.75 vdc) and all 12 vdc lights and appliances turned off, the converter's 110 volt input current is less than one amp. Also, I tend to believe the PI EMS is displaying a reasonably accurate current reading. With only the 13,500 BTU Dometic a/c running, with fan on high, (all other breakers off) the PI EMS shows a current drain of 13-15 amps (data sticker on the a/c says 2 amps for the fan motor and 12.5 amps for the compressor). The inverter is wired directly to the battery. BTW, the inverter output voltage is very stable--116.0 volts under no load--115.8 volts under maximum load (650 watts)!!

That doesn't sound normal. I believe a double bulb light fixture takes 3A dc, or about 39W. Converter efficiency is about 80%.

AC power is 39W/0.8 = 49W
AC current is I = 49W/120V = 0.4A

I would check the meter accuracy. Plug a 100W light into the ac receptacle. AC current is 100W / 120V = 0.83A.

Sal

otrfun wrote:
I just noticed as I turn on each 12 vdc light, the input current reading on the PI EMS (110 volt line side) to the converter jumps up approx. 1 amp for each light.

A good idea to scan converter temp occasionally with IR or with your hand. What comes out must go in if the converter is doing it's job. A 20% loss however at 480 watts is a bit too high. 96 watts of heat is a lot of heat.

Converter is only about 80% efficient so you will always draw 20% more than you use.

The actual amperage measurements would be interesting (maybe I missed it?). If the converter is drawing a minimal amount of current because the batteries are fully charged, the power supply would probably swing current draw as more 12v devices are used. I would think this could be totally normal.
It may also be that the EMS measuring circuit is funky. If you have a clamp meter, it would be interesting to see how the two correspond.

Thanks.

Yeah, my Prosine would make big jumps to 100amps @ 12v when anything was turned on, even on full batts. It would settle back quickly.

2oldman wrote:
First time I've heard of someone being able to measure the input amps to a converter. What sort of meter setup do you have?

I just installed a Progressive Industries 30 amp hard-wired Electrical Management System between my outside 30 amp L5-30 connector input and my breaker/converter panel. The remote display gives realtime input voltage, current, and line frequency, in addition to all the protection it provides. Very cool device.

In any case, I should mention I turned off all the breakers except the one feeding the converter when I made these observations. Bottom line, everything appears to be working fine. The battery is new and load tests just fine. The converter charges and recharges the battery just fine. I just noticed as I turn on each 12 vdc light, the input current reading on the PI EMS (110 volt line side) to the converter jumps up approx. 1 amp for each light. With a fully charged battery, the converter current (110 volt line input side) hovers around 0-1 amp with NO lights turned on.

enblethen wrote:
A standard amprobe will read input amperage. Of course it must be on the wire.
OP:
What kind of rig do you have?
What meters are you using to read the amps and voltages?

A lot of us use our killowatt meters..

Jim

A standard amprobe will read input amperage. Of course it must be on the wire.
OP:
What kind of rig do you have?
What meters are you using to read the amps and voltages?

First time I've heard of someone being able to measure the input amps to a converter. What sort of meter setup do you have?