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 > Voltage drop on inverter

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phemens

Montreal, Canada

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Posted: 08/10/19 09:15am Link  |  Quote  |  Print  |  Notify Moderator

I have a Samlex 3012 inverter charger that is powered by 4 x 100 ah LIFEPo4 batteries. Each of the batteries is wired separately to a bus bar using 00 welding cable, this bus bar feeds another one that distributes to the inverter, solar, etc. The busses are separated by a cutoff switch. The Samlex pulls from the 2nd bus with 0000 wire.
We are out dry camping and i’ve observed when running high draw appliances (microwave, Tassimo coffee maker) that the voltage reading on the Samlex panel is dropping to between 11.5 and 11.8 V. The microwave is cutting off after 10 seconds, I guess it doesn’t like the low voltage. The funny part is that my Victron monitor, which is wired to the same bus that the inverter is drawing from is holding voltage steady at 13.1 V when the Samlex shows 11.5.
Any idea what is going on?


2012 Dutchman Denali 324LBS behind a 2006 Ford F-250 V10 out of Montreal
1 DW, 1 DD, 1 DS, 2 HD (Hyper Dogs)
1Kw solar, 400 AH LIFePO4, Yamaha EF2000 gen, Samlex 3000w Inverter

pianotuna

Regina, SK, Canada

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Posted: 08/10/19 09:29am Link  |  Quote  |  Print  |  Notify Moderator

Tighten all the connections?


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

DrewE

Vermont

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Posted: 08/10/19 09:43am Link  |  Quote  |  Print  |  Notify Moderator

You would seem to have a poor connection somewhere between the bus and the inverter. It should be pretty easy to figure out where it is by seeing what is getting warm or hot after a (brief) period of heavy inverter usage. Take care not to burn yourself.

(I'm assuming the voltage readings are in close agreement when the inverter is not loaded. If they disagree then, one or the other is out of calibration...or possibly both.)





BFL13

Victoria, BC

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Posted: 08/10/19 09:44am Link  |  Quote  |  Print  |  Notify Moderator

The inverter etc are all on the second bar, but where are the negs? The inverter's neg input might be guilty while the other things' negs are ok wherever they are connected. (monitor shunt?)

DMM to check voltage at each terminal of the second buss bar. Inverter is seeing the drop on its wires to its connection on the bar, not from the whole bar.

Try inverter on a different (working )part of the second bar.

Put inverter on first buss bar.

DMM to check for voltage drop across switches.


1991 Oakland 28DB Class C
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phemens

Montreal, Canada

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Posted: 08/10/19 09:58am Link  |  Quote  |  Print  |  Notify Moderator

Problem solved. There was a setting on the Samlex with a low voltage alarm set at 12V. I lowered it to 11V and everything seems to work fine. Still not sure why the Samlex is showing 11.5V while the Victron holds over 13V, but otherwise it works...
Looks like the voltage readings under load are at odds, but they match when idle.
I checked all the connections, everything seems tight and shipshape.
To the question about the negative side connections, I have bus bars separated same as on pos.

2oldman

New Mexico

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Posted: 08/10/19 10:03am Link  |  Quote  |  Print  |  Notify Moderator

phemens wrote:

The funny part is that my Victron monitor, which is wired to the same bus that the inverter is drawing from is holding voltage steady at 13.1 V when the Samlex shows 11.5.
Any idea what is going on?
If these readings are to be trusted, then it's obvious the problem is between the busbar and the inverter.

Do your batteries have a resting voltage of 13.1? I know Li batteries are pretty amazing, but it's odd they could hold that voltage when under high draw.

time2roll

Southern California

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Posted: 08/10/19 10:08am Link  |  Quote  |  Print  |  Notify Moderator

phemens wrote:

Problem solved. There was a setting on the Samlex with a low voltage alarm set at 12V. I lowered it to 11V and everything seems to work fine. Still not sure why the Samlex is showing 11.5V while the Victron holds over 13V, but otherwise it works...
Looks like the voltage readings under load are at odds, but they match when idle.
I checked all the connections, everything seems tight and shipshape.
To the question about the negative side connections, I have bus bars separated same as on pos.
Problem NOT solved.
Get a voltmeter in there and start checking voltage drop under load.

Consider going to a single bus and dropping the switch depending on what the measurements find.


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2oldman

New Mexico

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Posted: 08/10/19 10:11am Link  |  Quote  |  Print  |  Notify Moderator

I don't get why you have 2 sets of busbars.

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 08/10/19 10:27am Link  |  Quote  |  Print  |  Notify Moderator

One positive

One negative

Excellent practice

This is why I despise unsoldered lugs Don't give a **** if they're squeezed till they fart, this would never happen with soldered lugs.

Oh they look good
Tighter than hell
But it doesn't work

There is ZERO protection between the interior of the lug surface and the stranded wires.

Time to do a point-by-point voltage drop inspection while under full load. Don't forget the negaive side.

phemens

Montreal, Canada

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Posted: 08/10/19 11:09am Link  |  Quote  |  Print  |  Notify Moderator

To clarify, I have 2 complete separate sets of bus bars to keep things tidy. One just to collect the wiring from the battery bank - 4 each pos & neg. From there I have pos going to another positive bus via a cutoff switch, neg to other neg. On those buses, I have the inverter, 2 inputs from solar, output to trailer, and monitor. All the wiring is soldered lugs.
I will check each connection under load when we get home.
Victron indicates voltage steady at 13.05V with microwave running.

* This post was edited 08/10/19 11:27am by phemens *

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