Would Higher Octane Run the Gen Better? UPDATE

[BFL13]

UPDATE 21 Nov page 5

Ongoing saga with my 1700w (continuous) gen trying to run my 75 amp charger at 75 amps. Briggs and Stratton P2200 gen.

Previously posted that it would not (flashing overload red light), then discovered I still had it choked. Next test was to run it with the batteries full, but with an inverter draw of 127 amps, then turn on the charger, but now with the gen choke in the right place. Amps now -52 so 127 minus 52 = 75 amps from the converter/charger. No flashing overload light on gen. So I reported success.

Just been camping off grid, did a recharge with the gen and the 75 amper. No red light at first. 75 amps to battery bank. Then after a few minutes the red light started flashing but gen kept running.(It can shut off with overload.) Switched to the 55 amp charger and no red light.

We know that running a charger as a power supply is easier than doing an actual battery recharge due to the higher battery resistance. Sometimes it can do its full amps as a power supply, but might not be able to do its full amps on the battery. BUT--I thought that if it did its 75 amps as supply that was the same effort as doing 75 amps on a battery.

Here, 75 amps on battery seems to take more effort from the charger than doing supply, so needs more from the generator? 75 is not the same 75?

Also there is some relationship between the generator engine running and the power output, as seen when it was choked and did less 120v power. I am wondering if the gen would run the 75 amper without the flashing overload light if only the engine ran a little "better" (not sure what I mean by that in what the engine would have to do) More revs?

The manual mentions engine getting bogged down with too much load-I did not hear it running slower.

So finally after all that background--would the engine do "better" if it ran on higher octane gasoline? It has 87 now (regular). And if it did, would that make the difference to output power I need where I am just on the edge for running that 75 amper?

Engine is 6.77 cu-in(111 cc), 4500 revs single-cylinder, revolving field, wants 87 octane minimum below 2500 ft altitude.

I will not have an opportunity to try that for a while, so I am asking here to learn if it is worth trying at all. Thanks.

[BFL13]

MEXICOWANDERER wrote:
Yea or no alcohol matters.

You could run 115/145 octane av gas and it wouldn't do squat versus alcohol-free 87 octane gasoline.

I completely don't understand "ethanol(gasohol)" vs "alcohol". What's with that?

[MEXICOWANDERER]

Yea or no alcohol matters.

You could run 115/145 octane av gas and it wouldn't do squat versus alcohol-free 87 octane gasoline.

[BFL13]

PT you must have the Platinum one that also beeps 🙂

Good test Mr Wiz, we are in the ball park on all that.

Interesting exercise in learning a whole bunch of things from guys on here (as usual), but I am no farther ahead with running my 75 amper from my new little gen. Drat. It does run it, but I have no way to know if that flashing red light means I really shouldn't.

Since I don't have to, I won't. Just use the 55. Too bad I don't have the 65. That would be just right for this gen.

I still didn't try it with 91 octane though. Or change to synthetic oil. Everyone says don't bother..... 🙂

[pianotuna]

BFL13,

My KAW beeps as well as flashes.

[MrWizard]

I ran a test with my 100 amp A.C. Power meter DIY kill a watt
Battery condition was too high for a full 75 amps
I did get 67.2 amps charge rate
Input to the converter 114.0 volts, 12.90 amps = 1470.6va
Watts reading 1153.4
Cos/PF 0.771 reading,

But 1153.4/1470.6 = 0.784, don't know why the difference but is not great enough to matter much

How ever when charging got down to 3.6 amps

Input was 120.3v * 1.18 amps = 141.95va
85 watts
Cos/PF 0.59

Got to be careful with them store bought kill a watt meters
You can blow the tiny internal fuse
Been there done that, also repaired it
But I Built the big one three years ago to read generator and shore power
I put it in a HF plastic ammo box, and wired it with 30 amp male and female RV plugs
Using adapters I can do 15a, 20a, 30a, 50a

[BFL13]

Note: The Kill-A-Watt was blinking on shore power too but only after amps got to 15.1, so it is not to do with the red flashing overload lamp on the gen when it blinks. KAW rated to 15a so must be a safety thing it has for itself.
--------------
Got fresh 87 for the gen, still get the flashing red running the 75 amper doing battery charging but not when doing supply at 75 amps.

Supply KAW with charger at 75 amps

119v, 13.65a, 1137w, 1625VA, 0.70PF didn't take battery voltage. No flashing red on gen

Battery Charging at 75 amps (AGM 250AH battery at 73%--12.7v)

118v, 14.49a, 1247w, 1715VA, 0.73PF output 75 x 14.2 rising, red lamp flashing on gen. KAW not blinking.

wait a bit then,
117v, 14.93a, 1278w, 1741VA, output 75 x 14.4 battery

then 116.8 and 15.01 blinking

So that does show rising VA with rising battery voltage during the recharge. I can't do a long run of that with the 75, but could with the 55. I don't think I need more proof there though.

The red flashing on the gen does not mean the output 120 is intermittent, that was just the Kill-A-Watt.

The KAW does show the inverter in the gen doing its "amps creep" as loaded AC voltage drops with the increased load in VA. Same action as an inverter on DC running an AC load, where DC amps go up as battery voltage supply to the inverter falls the longer the 120v load stays on.

The gen manual does not mention the red flashing light, just that the gen will shut down output when overloaded and there is a reset button for that. I don't know if the gen engine would conk out at some point of overload too. My Honda 3000 did with a cold start and too soon hit with a big load. B&S "tech support"= "customer phone guy with no clue" never heard of the flashing red and his supervisor said maybe there was something wrong with the unit.

I think the flashing red is an "early warning" of overload and if you keep going then it will shut down. Don't know (yet?). Anyway I don't like to keep running the 75 with that light flashing, so I will use the 55 when that happens.

Obviously I should have bought the Honda 2200 instead with its 1800VA. Only three times the money! 🙂

[MEXICOWANDERER]

It is that formula I used (I termed it "watts acceptance") to formulate a curve for the 150 amp charger. X amps times desired voltage set point in agreement with generator voltage and Hz determines the actual not theoretical ability of the generator. X amps times volts = va

There is a peak after which generator Hz or AC va starts to slump.

In short battery charge acceptance in va versus generator va available. Difference can be expressed as pf GROSS Power Factor. Energy Efficiency.

Generator harmonic waveform distortion under high loading % is responsible for a lot of discrepancies between apparent power available and actual power delivered by a generator. A high percentage of agreement between generator and charger is necessary in order to obtain the optimum.

This is why I opted for an extremely expensive stator winding in my Kubota / Kato. Simply put, the 15 pounds +, of extra copper allows the KATO to respond like a 15Kw instead of a 12.5Kw this means an ability to develop more power with the same horsepower with an inductive load.

This is not possible never mind feasible with a lightweight portable unit.

But it DOES explain WHY there is an apparent discrepancy in efficiency.

[BFL13]

DrewE that makes sense.

[DrewE]

With the charger connected to the battery, it's actual output voltage and the voltage at the battery are the same. It is true that the output voltage needs to be higher than the resting voltage of the battery to charge it, but during charging that voltage is seen at the battery terminals. As a corollary, under heavy load with both supplying part of the load, the voltage of the battery, and hence the output voltage of the charger, will be below the resting voltage of the battery.

The battery charger's set voltage (the "charger voltage") is just what you're asking it to try to output. It doesn't necessarily actually produce that voltage under all conditions; indeed, in the cases you're talking about, it cannot.

If analogies help, it's somewhat like a cruise control in a vehicle towing a trailer. The cruise control setting is the voltage setting of the charger, and the actual vehicle speed the charger's output voltage, and the trailer speed the battery voltage. Assuming everything is set up properly, the trailer speed and the vehicle speed are the same, and can't differ without someone having a really bad day. If you go up a steep enough hill, the cruise control set speed doesn't change, but the vehicle and trailer speed will drop because the engine simply can't supply enough power to maintain that speed, despite the cruise control asking for more. In terms of power and gas consumption and distance traveled and so forth, the actual speed is what is important, not the speed the cruise control would like to go.

[BFL13]

MrWizard wrote:
Just put the kill a watt, between the generator and the converter
While using the MW
Then again for battery charging,
Charging directly, and also thru house wiring which might shift the pf slightly
You can get watts , VA, PF for all situations

That's the plan, but if the gen's red light starts flashing right away, I can't get any Kill-A-Watt reading. It just blinks on and off in time with the red light flashing.

I could run the charger from the house shore power as long as it does not pop a breaker in the house and get the two Kill-A-Watt sets of numbers for supply and battery charging that way.

[MrWizard]

Just put the kill a watt, between the generator and the converter
While using the MW
Then again for battery charging,
Charging directly, and also thru house wiring which might shift the pf slightly
You can get watts , VA, PF for all situations

[BFL13]

DrewE, you are correct as to how it works.

I do have the converter charger wired to both the battery bank and to the DC fuse panel. The inverter is wired to the battery bank.

For the "supply" test, needed when the batteries are too full to accept all the charger's rated amps so you can test doing straight recharging, I have the RV on inverter whole house (so it can run the microwave). I have the converter only plugged into the generator.

So now I can turn on the MW, get that -127 amps showing on the Trimetric, and then plug in the converter to the gen. Now the Trimetric says -52, so I know the converter is doing 75 amps.

Yes, there is some voltage drop along the converter-battery paths, but not much.

My problem with "output watts" is that I thought the converter's set voltage is what counts, never mind what the battery voltage has got to by whenever during the test. To me, the output is from the converter and it is set at 14.x and stays at that no matter what.

The charger's voltage has to be higher than the batteries' or no amps. The charger is doing the work, so to me it is the charger's voltage that should count in the output watts figure.

It is true that the output watts and so the input required from the gen drops off as amps taper during the absorption stage. But during the constant amps bulk stage earlier, I thought output watts stayed the same.

If not, then as battery voltage rises during the bulk stage, input required from the gen would go up along with battery voltage.

I will do more "observations" during the next test run doing battery charging (not supply) and see what happens in real life.

[BFL13]

full_mosey wrote:
BFL13;

Check the PF of the chargers with the Kill-a-Watt during bulk if possible. AFAIK, .65 PF chargers use more dinosaur farts than the .95+ ones.

HTH;
John

I did a Kill-A-Watt with several different converter/chargers and most of them are in the PF 0.70 area. Only the "PF-corrected" ones I have had PFs in the high 90s. Inverter/chargers seem to mostly have their chargers PF corrected though.

Of course it is the VA that the generator or shore power must supply, not the "watts" figure. "Efficiency" is defined using the input watts figure, which is misleading when there is a PF on the load. Using the watts makes efficiency higher---so that is what the salesmen pitch, not the actual input vs output.

Just look at the so-called specs for the various converters out there of whatever brand. They give the input watts, which is way low compared with the VA with a PF 0.7 not mentioned anywhere in their so-called spec sheets! 😞

[DrewE]

BFL13 wrote:
"If the output voltage is higher, then the power is of course greater...and conversely if the system voltage is lower, the output power is lower, assuming the current remains constant."

I am not clear on the "system voltage". The charger's voltage is set at 14.6v and stays there solid the whole time. 75 is constant the whole time during these two situations.

In "power supply", the battery bank is being drawn down by the inverter pulling 127 amps (MW) and so battery voltage is low. The charger then supplies 75 amps and now the battery draw is 52 amps but its voltage is still low, just not as low.

In "battery charging" the battery voltage is in the 13s at first then climbs. So the charger is facing higher resistance than when doing "supply", but it is still doing its 75 amps.

I have seen it before where a converter will do full amps doing "supply" but not when battery charging. Eg a 7355 in the 5er did 56 amps but only 35 amps battery charging--and on the same wires to the battery.

So I think the charger doing 75 on battery charging could need more input than when doing 75 amps as supply. No?

Brings up an old question I never got clear on--is charger "output watts" using the charger's voltage setting, or is it using the battery voltage in the watts?

I'm assuming your converter/charger/supply is connected directly to the 12V distribution system, as is the battery; if that's not true, then there's a good bit more going on than was obvious to me from your posts and I apologize for giving any misleading or confusing info.

Assuming they are wired together, though, the (actual) output voltage of the converter/charger/supply and the battery voltage are always the same voltage, save for any wiring voltage drops which I can only assume you have minimized. If the battery voltage is 13V, the output voltage of the supply is actually 13V, even if its regulator is set to output 14.x volts; you're running into current or power limits and its output voltage is drooping. Likewise, when the inverter is running and consuming a lot of current, the battery (and converter output) voltage might be perhaps 12V and the converter is supplying it's full 75A; it's solidly in the current limiting part of operation.

If, somehow, the converter or charger or whatever is connected to the battery and maintaining an actual 14.6V while the battery voltage is 13V, you must have a 1.6V drop in the wiring!

[full_mosey]

BFL13;

Check the PF of the chargers with the Kill-a-Watt during bulk if possible. AFAIK, .65 PF chargers use more dinosaur farts than the .95+ ones.

HTH;
John