Microwave off Inverter. Volt drop with 3 batts parallel

Hint: If you want to run a microwave on batteries or genny, I'd suggest you toss out the microwave in the RV and replace it with a panasonic true inverter microwave. Why? well it is the only microwave that when you drop the power level for cooking it drops the input power as well instead of just cycling between 0% and 100% power.

So...... as an example, I an EASILY run my panasonic on a 1000VA PSW inverter even though it draws 1500VA at 100% power. I just drop the power to 5, and it draws 800VA. yes it takes about 25% longer to heat a cup of water or warm some veggies, or defrost some meat, but it runs fine on a smaller inverter, doesn't sag the batteries as much.

When on shore power or generator I can run it however I want, and when on the genny it doesn't make the genny rev, idle, rev, idle like a regular microwave does.

Hi,

Yes, but even if the banks had the same cell count and same amp-hours the six volt jars would exhibit slightly lower voltage drop.

BTW even when I had 875 amp-hours of battery bank (7 12 volt marine jars, ideal for high amp demands) I still saw voltage drop on fairly small loads such as 30 amps for the 12 volt DC fridge.

lawrosa wrote:


LOL thats funny...

Well with 6 batts i'm sure you don't see voltage drop...

Im talking about the two batt guys... I know they are out there...

Another tidbit..

If I had 6 volts they would each see the 70 amp draw.

My 12 volts only see 35 amps each.

If both banks were the same AH's the 12 volts would last longer...

True?

lawrosa wrote:
Good read

http://yarchive.net/car/rv/golf_cart_batteries.html

http://yarchive.net/car/rv/battery_resistance.html

More than a "good read", rather both are great articles from someone who understands much more than the masses here on this forum about the intricacies of deep cycle battery use for RVs, and which is summarized nicely in this statement which I've copied because most won't want to read through either of these links in their entirety. It sums up what a few of us have been trying to explain anytime this subject comes up - why 12 volt jugs in parallel are often the better choice than 6 volt jugs in series for RV use.

"Brian, if you have any large 12 volt loads such as an inverter I predict you will be disappointed with the golf cart batteries. I'll explain.

Two years ago I accepted the advice here in this group without thinking too much about it and replaced my two paralleled group 27 batteries with a pair of golf cart batteries. I immediately noticed several differences. One, anytime I operated a heavy load the voltage sagged MUCH more than it did with the old batteries. My inverter would trip off long before the batteries were discharged because of this. I'm speaking of terminal voltage and not at the other end of a length of wire. I could no longer fast charge them. The internal impedance was so high that they simply would not accept a fast charge without heating. My cordless battery charger could charge the old pair in an hour. It took several hours with the new one. Cranking the genny would drop the voltage so much that the inverter would trip. I got in the habit of hitting the interconnect switch before cranking so that the start battery could do the job.

I did some research like I should have done in the beginning. I learned that golf cart batteries are optimized for long, moderate rate discharges and are NOT designed for heavy loads. This is a mis application. In RVs that don't have heavy loads and don't need to fast charge it is not a problem."

And this has been just my point anytime this discussion comes up - adapting deep cycle 6 volt batteries that were originally designed for moderate, intermittent long term draw in golf carts is not the best choice when one of the main tasks of those batteries in an RV application is to supply power for short duration, heavy load inverter draws. These 2 articles you've linked to are the best I've seen that explains this in terms that are easy to understand, even for the "6 volt or go home crowd". :R

lawrosa,

You always believe the hydrometer. Voltage is only valid if there has been zero charging and zero use for 24 hours.

For your own personal bank you may wish to develop a table that is voltage vs specific gravity when the batteries are under a moderate load.

Good read

http://yarchive.net/car/rv/golf_cart_batteries.html

http://yarchive.net/car/rv/battery_resistance.html

azrving wrote:
This 6 volt guy is often pulling 20 + amps during the evening off of six gc2 samuals club batteries. Now and then if it's early in the morning and I really want peanut butter and jelly toast I will run the toaster and iirc it will pull about 90 amps DC. DW will run her hair dryer on low sometimes and pull 80 amps DC. That's about it for me, other than that I fire up the Hoonda 3000 remote start.

GC2 are made for long slow rides around the golf course. I haven't ran them but I understand that 12 volt AGM will do better at kicking out higher amps.

I'm talking about pulling that amperage for minutes not hours and this is a 600 + ah bank. Those gp24's are probably doing somersaults when you hit them with that amperage. When you remove the load they probably reach up to wipe their brows and say ahhhhhhhhhhhhhh thank god he quit and a wisp of steam floats out of the caps.

LOL thats funny...

Well with 6 batts i'm sure you don't see voltage drop...

Im talking about the two batt guys... I know they are out there...

Another tidbit..

If I had 6 volts they would each see the 70 amp draw.

My 12 volts only see 35 amps each.

If both banks were the same AH's the 12 volts would last longer...

True?

Delete duplicate

This 6 volt guy is often pulling 20 + amps during the evening off of six gc2 samuals club batteries. Now and then if it's early in the morning and I really want peanut butter and jelly toast I will run the toaster and iirc it will pull about 90 amps DC. DW will run her hair dryer on low sometimes and pull 80 amps DC. That's about it for me, other than that I fire up the Hoonda 3000 remote start.

GC2 are made for long slow rides around the golf course. I haven't ran them but I understand that 12 volt AGM will do better at kicking out higher amps.

I'm talking about pulling that amperage for minutes not hours and this is a 600 + ah bank. Those gp24's are probably doing somersaults when you hit them with that amperage. When you remove the load they probably reach up to wipe their brows and say ahhhhhhhhhhhhhh thank god he quit and a wisp of steam floats out of the caps.

I made another one today....LOL... Pulled 70 amps for an hour to see extreme results off the 3 12 volt batts

This was with toaster over..

What I found.

1. Voltage held well I thought.. I have nothing to compare it with though. I never did this type of test before. I am not sure what I even proved.

2. One batt may be weaker then the other. But this may be a symptom of the large amp pull and that batteries amps got pulled down more then the other. Wiring issue? Or a batt going bad?

3. Truck batt seams worthless. During this amp draw the truck batt was still up there on charge. Strange that I can charge through 7 pin at 16 amps but it will not pull amps from truck equal to RV batts. I know though if I let the batts rest long enough the truck batt will charge the RV batts back up.. My assumption since the truck batt was at a higher voltage after test.

The extra truck batt my belief is for a TC because of 8 ft bed, or was there for emergency roof lights. In construction you can leave truck at construction site with roof lights on and not kill start battery.

4. I should of checked temp of batts . But cant remember everything. Probably not good pulling constant 70 amps from batts..

5. I am assuming the Acid in battery has to catch up to an accurate SOC? Volts and SOC didnt jive in the end... Who do I believe?

5. My last rule of thumb is if the inverter alarm goes off I must recharge. Geez Im beating the hell out of my batts...LOLOL

6. I wish I knew what the 6 volt guys were /are getting for comparison.

I need to make shorter videos I know.. Well I did my best here and as I said I learned a bit of things doing it.

Enjoy...


https://www.youtube.com/watch?v=7p-oNT8YDIs

pianotuna wrote:
lawrosa,

Thanks for taking the time to produce the video.

Voltage drop may be greater in six volt jars because of the relatively thicker plates.

12 volt jars have the advantage of having twice the number of cells. That means 50% less load per cell. The plates are of necessity thinner, too, so there is inherently lower voltage drop.

The biggest issue you have is a not very nice MSW inverter. There are some MSW that do a little better than what you have. I had a nice Cobra 2500 watt that would power up the 13500 btu air conditioner. It showed 118 volts on a Kill-a-watt meter.

I did research on the krieger, and a 90% min eff, and a 3 year warranty sold me on it...

Plus about $105 bucks...

Manual

http://www.kriegermfg.com/wp-content/uploads/2016/01/KR1100_1500_2000_MANUAL_englishV83017.pdf