Home » Public Forums » GMCnet » [GMCnet] Interesting electrical/battery issue
| [GMCnet] Interesting electrical/battery issue [message #259803] |
Fri, 22 August 2014 13:00  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
|
Senior Member |
|
|
And the culprit is......the inverter microwave. Matt nailed it!
I used a 12ga three wire appliance extension cord to run the 1994 Sharp Convection microwave in the Clasco from the four six volt wet cell battery bank and Xantrax SW2000 inverter from the Royale. It ran just fine with the following readings:
On the Xantrax battery monitor in the Royale - 13.1 volts at rest (had been on float charge) sagged to 11.6 while the Sharp microwave was running, and it was drawing 152 amps. The display on the front of the inverter showed 11.4 volts drawing 1711 watts. It ran for the whole two minute cycle heating a cup of water. As soon as the microwave turned off the voltage returned to 12.5.
I then ran the extension cord from the 1500 Samlex PST 1500-12 sine wave inverter in the Clasco to that same microwave. That inverter is attached to a 4D AGM with a rated 220 amp hour capacity. The microwave again ran just fine. The battery monitor in the Clasco showed resting voltage of 13.4 (again, was on float charge all night). With the microwave running voltage sagged to 11.9 volts, 161 amps and the inverter panel showed 1570 watts. Not bad for an inverter rated at only 1500 watts to begin with. Again, the microwave ran for a full two minute cycle and never sounded labored. As soon as the microwave turned off voltage returned to 12.7 volts. That is a 0.8 volt sag under a very heavy load. And, the battery cables and inverter cables in that set up are all 1ga, not the much heavier 00ga in the Royale.
So, a couple of observations based on these tests:
1) I think the Samlex sine wave inverter is a lot better than the Xantrax sine wave inverter in terms of tolerating a high watt draw that is near (slightly over in the case of the Samlex) the rated capacity of the inverter. The Samlex only claims a continuous output of 1500 watts while the Xantrax claims an output of 2000 watts for five minutes and then 1800 watts continuous.
2) the AGM batteries appear to be more forgiving of a heavy amp draw than are the wet cell batteries and if they can be discharged to 80% without harming service life as Matt's experience would suggest, they are well worth the cost difference.
3) the inverter microwaves simply won't work with the high frequency switching sine wave inverters. The non-inverter microwaves are just fine.
4) if I ever get around to it I will increase the AGM bank in the Clasco, perhaps by adding a second 4D in parallel, or if I can find something to do with this current 4D I likely would change to two of the very tall 6v deep cycle AGMs
5) way easier to turn on the generator to run the microwave than all this fiddling around. The batteries would likely be depleted after a half hour or so of microwave anyway.
6) the heavy 00ga wire would likely help the 0.8 volt sag in the current Clasco set up, but I don't think it is worth changing unless/until I increase the AGM battery capacity
Thanks for all who offered suggestions.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
,,,,,,,,,,,,,,
Jerry,
The dance is over and I hope you are ready....
First: The draw-down could be either an in sufficient connection or the Peukert problem.
Have you done the experiment where you actually put the meter right on the lead of the battery posts??
- If no, Try that and tell me what you find. Because if the terminal (at the posts) does not sag as much, then you have to restart chasing this
problem there.
- If yes, then it is the Peukert exponent coming to get you. Newer batteries might do better, but that "snap back" is a result of internal resistance
that is a combination of sulfation and circulation in the cells. The internal resistance will also increase with temperature that is a normal result
of working the cells. Flooded cells (with caps and visible electrolyte) count on the circulation to get the most out of the chemistry. Sulfation
just happens to old Lead Acid batteries and there isn't a lot that can be done about it if the bank is ever discharged, and even banks that are never
discharged seem to have this problem.
Next: Do you remember how much that old Heart inverter/charger weighed???
It had a transformer and a circuit tuned to 60Hz. It did a pretty clean sine. The new "Pure Sine" devices are not. If you know about audio
equipment, one of the thing that used to be talked about was harmonic distortion. What you may be fighting is the digital war that is going one
between the microwave and the inverter.
Unfortunately, without being there with a small heap of analysis gear, I can't be any more help than that. I can tell you that I had a similar
go-around with a vary similar system on an owners cruising sloop a few years back. What won was an isolation transformer between the two. Like you
need another 40#.
Good Luck
Matt
--
Matt & Mary Colie - Members GMCMI, GMCES
'73 Glacier 23 - Still Loving the Applied Rear Brake Control Arms
SE Michigan - Twixt A2 and Detroit
,,,,,,,,,,,,,,,
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jerry & Sharon Work
78 Royale
Kerby, OR
|
|
|
|
Current Time: Sun Sep 29 21:14:54 CDT 2024
Total time taken to generate the page: 0.00959 seconds
|
GMCforum
Search
Help
Register
Login
Home
