Inverter problem

[max from alaska]

I have a 2014 R27. When the inverter is run off the house batteries while at anchor (engine not running), I attempt to run the microwave. The voltage before running the microwave is about 13V. When the microwave is run to heat a cup of water or similar, the battery voltage drops to 12.5V immediately, and within about 10 seconds the inverter trips off (the inverter remote monitor shows zero input battery voltage even thought the battery voltage is at 12.5V). Is the inverter defective in that it cuts off at 12.5V (whereas the unit is rated at low voltage cutoff at 10.5V). The unit is a Promariner 1500W model 5150.

During this event the battery voltage never drops below 12.1V during the draw, recovering to about 12.7V afterwards. I assume the problem isn’t a bad battery. Correct?

 

[knotflying]

See what happens when you do it with the engine running. You may have batteries that are marginal and the draw is enough to bring the batteries down below the requirement for the inverter and it shuts down. With the engine running the alternator should compensate. If that works then do a load test on the batteries. Also check that all connections from Batteries to the inverter are good, with no corrosion. That will include the switch and the fuse in between the batteries going to the inverter.

 

[Martin610]

Good input from Knotflying. A couple more things may help.

You could have a capacity problem. If you have the Cuisinart CMW-200 the input power for that on the microwave setting is 1500 watts. Cuisinart confuses people with the specs as the output power is 1000 watts. If you have this model microwave you need 1500 watts from your inverter and batteries. If you have a 1500 watt modified sine wave inverter, which is only about 90% efficient, you are short on power. A pure sine wave inverter is more efficient, but still might be short.

As Knotflying points out, even if you have the specs, if the batteries are older the MW may draw power quicker than the batteries can supply.

If you have different equipment let us know.

For myself, I use a small electric kettle I got off Amazon. It's a 700 watt unit and heats up water for coffee and tea very quickly. Runs just fine off the inverter and it's a lot easier on the battery power.

-martin610

 

[max from alaska]

I double checked the DC connections to the inverter. All good (measured same voltage at the battery terminals and at the inverter terminals at full charge, and wire brushed the terminals). The batteries have two summers on them (about 28 weekend trips total), and they have aged somewhat I can tell. I’ll test it with the engine running next spring (it’s winterized now).
I did call the Promariner rep just now and he thinks the inverter isn’t functioning properly. It shouldn’t cut off at 12-12.5V, and at rest the inverter controller shouldn’t read 50% DC voltage input when the battery voltage is 13V. He advised a new inverter.
I never run the microwave (I use it as a cupboard for storing dishes and bowls)…I did note that it worked long ago when at anchor, so I ran it now to check the inverter system which had cut out while underway last summer from a GFCI trip.
So….I’m due for new batteries soon anyway, and I’ll probably end up changing the inverter too.

Thank you all very much for the input

 

[GaylesFaerie]

The comments above are spot on. And knowing the actual age of the batteries will help. Also you may want to check the electrolyte level. The density or specific gravity of the sulfuric acid electrolyte of a lead-acid battery varies with the state of charge (see table below). Specific gravity is read with a hydrometer. A hydrometer reading will tell the exact state of charge. I use a HydroVolt meter which is very easy to use and read:

https://www.solar-electric.com/midnite- ... 6oQAvD_BwE

FLA BATTERY VOLT TABLE

%CHRG VOLT Specific Gravity
100 12.70 1.265
95 12.64 1.257
90 12.58 1.249
85 12.52 1.241
80 12.46 1.233
SHALLOW CYCLE DISCHARGE LIMIT
75 12.40 1.225
70 12.36 1.218
65 12.32 1.211
60 12.28 1.204
55 12.24 1.197
50 12.20 1.190
45 12.16 1.183
40 12.12 1.176
35 12.08 1.169
30 12.04 1.162
25 12.00 1.155
DEEP CYCLE DISCHARGE LIMIT
20 11.98 1.148
15 11.96 1.141
10 11.94 1.134
05 11.92 1.127

 

[barbeque2]

Promariner are prone to fal, especially that old. They don't make them any more, which should tell you there were flaws in the design. Lucky you got this many years. I have a 2014 31cb that I installed a Xantrex after my charger/ invertor failed. Easy switch and it senses connected to shore power or not. No switching. Works great.

 

[gswearin]

Hi All,
Reviving this so all the other suggestions are in here. I have a 2021 R29, so 2+ years on the batteries. Other than two "oops" situations, they've not gone below 50%. We've had a coffee maker on board since it was new. It is a significant draw for a short period but its worked well for 2 years. In the past two trips the draw from the coffee maker is causing a drop in voltage triggering the alarm. I've looked for any other things plugged in but none. Guess I'll check all the batteries, unless there are other suggestions. Oh battery level was 85% or above each time it happened.