Ram Promaster Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter · #1 · (Edited)
My inverters are reading around 190V (it doesn't settle, it jumps around, but around 190V) when I plug in a high load appliance, even if I don't turn the appliance on.

I have two PUGU 3000W Pure Sine Inverters from eBay as well as a Cobra 2500W Modified Sine Inverter that I've tried. Connected via 4/0AWG to a 12V 300Ah LiFePO4 rated for 100A continuous.

All three inverters read around 190V from two different voltmeters on the unused outlets when I plug in an 1800W induction cooktop (just plug in, not turned on) OR run my 1500W microwave on 50% power.

The induction cooktop requires pure sine and draws ~350W even when it's off...not sure why, maybe it's 'charging' the magnets or something (that's another story). The microwave should only be around 750W when on 50% power. In both cases, I'm not running too high of a load for my 12V 300Ah LiFePO4 battery rated to run 100A continuous (1200W).

Any ideas why my voltmeters (plural) are reading excessively high voltages from the unused AC outlets on all three inverters? After running for about 5 seconds, the microwave quiets down and the voltage usually drops to ~120VAC.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #2 ·
Voltage at the battery terminals, where the inverter is connected (my battery has separate 'charge' and 'discharge' ports because it's huge), jumps from 13.5VDC to ~96VDC when I run a high load appliance through the inverter....wtf.
 

·
Registered
'16 2500 159 HT Granite Window - OH(io)
Joined
·
375 Posts
Most microwaves running at 50% power means that it if you set it for lets say 2 minutes, it runs at full power for half of those 2 minutes. 30 seconds on, 30 seconds off, 30 seconds on, 30 seconds off. Or something like that.
The high voltage readings are probably caused by the high surge current at startup of the device.
 

·
Registered
2014-159 HR in CT
Joined
·
3,748 Posts
120v ac is about 170v peak to peak. If your inverter creates a slightly non-sine wave, the meter is getting confused by a non-normal waveform (like the one at your outlet in the house)... That probably accounts for the wacky AC reading....

Digital meters are known to do this type of thing... an old needle meter would probably reflect a more accurate measurement.

What does your meter measure in the house?
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #5 ·
Voltmeter shows a steady 123.1VAC on my house outlets and drops to a steady 116.3VAC when I turn on a 1200W appliance.

My battery and inverter on the other hand show fluctuating voltages when under load and the voltage jumps to around 190VAC and 96VCD, inverter and battery, respectively, and moves around like crazy.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #6 ·
I don't have a lightbulb, but I tried a variable temperature heat gun. The invert shows the approximate wattage and it does correspond as I change the temperature on the heat gun.

The voltage is no longer jumping on the battery side, whether I use the heat gun or the microwave. It's no longer jumping to 96VDC. Not sure what changed.

Rather, voltage DROPS now...it's going from 13.5VDC down to as low as 12.9VDC when I run the heat gun or microwave. It holds around 13.3-13.4VDC until I get the heat gun over approximately 750W, then it really wants to drop below 13VDC. II thought LiFePO4 was over 90% charged at 13.5V and is not supposed to sag under load - should it still show 13.4-13.5V when putting out close to 100A? Or is it normal for this battery chemistry to drop voltage when under heavy loads?
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #7 ·
Actually, now that I think about it, my electric skateboard is LiFePO4 and its voltage sags under load: it'll say it's like 90% full battery and then you go up a hill and it could say 10% and then as soon as you back off the throttle it says 90% again, it's basing it's percentage off of purefly voltage and nothing fancy. So, maybe this is normal?

Then again, I though part of what was so special about these batteries is that they're supposed to hold voltage under load...I'm confused.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #8 ·
So, after voltage drops from 13.5V to 12.9V when running the heat gun at approximately 800W, voltage returns to only 13.2V on the battery when I shut the inverter down.

Are my batteries just not charged?
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #9 ·
Battery voltage drops from 13.36VDC to 13.18VDC by just having the inverter turned on with no load.

Of course, just now, the voltage rose to 17.xVDC doing the same exact thing. Nothing is very consistent over here. This multimeter must be crap, or these batteries must be very low, or this inverter is garbage, or all of the above.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #10 ·
If you know of anybody in Southern California whom I can hire to go through my electrical setup, please let me know. I need to have this thing fixed as soon as possible.
 

·
Premium Member
Joined
·
8,845 Posts
Simpson 260 analog. Use mine all the time..... wish I had it here in AZ
[ame]https://www.amazon.com/Simpson-260-8-12388-Analog-Multimeter/dp/B002R6MWL0/ref=sr_1_2?ie=UTF8&qid=1509232246&sr=8-2&keywords=simpson+analog+VOM[/ame]

Here is an inexpensive one you might try.
[ame]https://www.amazon.com/Tekpower-TP7244L-7-Function-Multimeter-Protective/dp/B00MI6T0IW/ref=sr_1_1?s=automotive&ie=UTF8&qid=1509232457&sr=1-1&keywords=analog+VOM[/ame]
 

·
Registered
Joined
·
808 Posts
Simpson 260 analog. Use mine all the time..... wish I had it here in AZ
Wow, you can still buy those things? My father had one, but I think it died and went in a drawer with the slide rules and such (the circular one was my favorite). Not that analog meters don't have their place... you can see things you can't see with a digital meter without an oscilloscope. Now that's something I really miss, access to really good test equipment.
 

·
Registered
Joined
·
640 Posts
Lithium Voltage Drop Under Load

Rather, voltage DROPS now...it's going from 13.5VDC down to as low as 12.9VDC when I run the heat gun or microwave.
You piqued our curiosity so we decided to try the same 'under load voltage drop' experiment.

With our pack charged to approximately 85% and with a very low charge rate of 1.5 amps on the pack, the battery voltage was 13.37 volts. Our lithium pack is 500ah.

We turned-on our electric hot-pot which, today, was drawing 135 amperes. The voltage immediately dropped to 13.18 volts, but after 2 minutes, it had further dropped to 13.06 volts.

These are voltages measured AT THE BATTERY TERMINALS. We assume that you, too, were measuring at the battery terminals - - at these higher current levels, even the shortest lengths of heavy gauge wire will exhibit substantial voltage drop.

Conclusion? Our voltage dropped between 0.2 and 0.3 volts under this 135 amp load. Your drop of 0.6 volts is twice that sum. Whether this is a significant different would depend on the size of your pack and the exact current your heat gun was drawing. Hope this is somewhat insightful.
 

·
Registered
Joined
·
640 Posts
With our pack charged to approximately 85% and with a very low charge rate of 1.5 amps on the pack, the battery voltage was 13.37 volts.
We wanted to add that the 'starting point' of this test may significantly impact the outcome. We have noticed that - - for any given state of charge of the battery pack - - the actual battery terminal voltage can vary several tenths of a volt depending on whether the battery has been under discharge, charge, or resting. We suspect that had we made this test after a substantial period of rest, the starting voltage would have been lower which we believe would have resulted in less 'delta' (drop) in voltage.

In the future, if you are interested, the two of us could set-up a more controlled and identical set of tests to measure and compare our respective 'under load voltage drops'.
 

·
Registered
Joined
·
2,113 Posts
.....cut.....

In the future, if you are interested, the two of us could set-up a more controlled and identical set of tests to measure and compare our respective 'under load voltage drops'.

Can you remind us again which brands of battery packs you and buck would be comparing? Are they the same?

There is no doubt a lot of interest in this new battery technology but I expect all brands don't perform equally.
 

·
Registered
Joined
·
640 Posts
We're uncertain what brand of lithium battery Buck is using.

We have China manufactured GBS batteries with an Elite Power Solutions Battery Management System - - all marketed as a ‘system’ by Starlight Solar of Yuma Arizona.

We appreciate the Elite approach which allows one to ‘spec’ an overall battery (Amp-Hour) capacity, then create a single battery with a single CPU controller and ‘monitoring’ readout.

Our friend, Tom, discovered that the 400ah lithium pack in his new Hymer Aktiv was, in fact, two seemingly independent 200ah batteries. He was given two switches: Pack A on/off and Pack B on/off. Tom doesn’t see this as a problem . . . he treats it like a ‘reserve tank’. When Tank A runs dry, switch to Tank B. We prefer to supervise our house battery as a single pool of available electricity and enable our various charging systems based on the status of our total battery capacity.

Another member of this forum may be using a hybrid of these two approaches. He has two Stark 100ah batteries tied in parallel, but, as we understand his system, both are routed through a single Victron monitoring system that provides voltage, in/out current, and ‘percentage of charge’ information for the two batteries as one. This should work well so long as Stark incorporates sufficient protection ‘inside’ each of their batteries. Battery Management Systems not only provide the user with important ‘status’ information (e.g. percentage of charge), but must protect the battery should any of its internal cells pass beyond acceptable high and low voltage cut-off points. The Elite BMS provides both of these important functions.
 

·
Registered
Joined
·
59 Posts
Discussion Starter · #17 ·
My pack was custom made through SHEN ZHEN YKXBATTERY ENERGY CO. I bought four 300Ah 12V batteries rated @ 100A continuous discharge and 200A continuous charge. Each battery has its own BMS.
 
1 - 17 of 17 Posts
Top