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BFL13

Victoria, BC

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Posted: 10/03/20 04:10pm Link  |  Quote  |  Print  |  Notify Moderator

With the battery starting at 12.2 and your charger is set for say 14.6v, first you get 80 amps Bulk and battery voltage jumps to say 13.6v. Then battery voltage slowly rises while amps stay at 80 amps until you see perhaps 14.2v battery--BUT that voltage is with voltage drop due to the 80 amps.

Close to then you see amps start to taper. With that tapering you get less voltage drop and gradually as Absorption continues, battery voltage gets closer to 14.6. It does not reach charger voltage of 14.6 until amps have stopped flowing so both read 14.6 and the battery is full.

Since input watts is highest required when output watts is highest, that is just before amps taper when battery voltage is 14.x at 80 amps.

Output watts is battery voltage x amps, but I am unclear which voltage to use --the one as seen with the voltage drop to it as measured at the battery, or the "real" voltage 14.6 as set on the charger.

Say you use the one as seen at the battery. So output watts is 80 x 14.2 = 1136w. Charger efficiency 85% typical, so input watts is 1336w

PF is 0.7 so demand on the generator is 1909VA. That is over the 1800w running spec for the Ryobi 2200 gen.

OP should use his big gen for recharging at 80 amps until amps start to taper at the start of the Absorption stage. Then he can switch to the 2200 for that long run at tapering amps.


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time2roll

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Posted: 10/03/20 05:10pm Link  |  Quote  |  Print  |  Notify Moderator

I thought the Honda was rated 2200 VA for 30 minutes. This should get the OP into absorption. OEM is probably just two batteries and not going to to be at full 80 amps very long.


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BFL13

Victoria, BC

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Posted: 10/03/20 06:54pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

I thought the Honda was rated 2200 VA for 30 minutes. This should get the OP into absorption. OEM is probably just two batteries and not going to to be at full 80 amps very long.


Could be, but OP says he has a Ryobi 2200. No idea what it does. Not clear if it has a 20a plug in. Specs say it is 15a AC.

https://www.ryobitools.com/products/details/2200-watt-inverter-generator

time2roll

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Posted: 10/03/20 07:02pm Link  |  Quote  |  Print  |  Notify Moderator

Yes of course. We will have to wait for a trip report....

BFL13

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Posted: 10/04/20 11:51am Link  |  Quote  |  Print  |  Notify Moderator

Bunch of numbers for those who like them! [emoticon]

Mr Wiz did his calculation using PF 0.7 but not converter efficiency of 85%. Sometimes you see these two things ttreated as being the same or at least where PF is part of the efficiency figure.

I think I can resolve this from using both and then comparing with what my Kill-A-Watt got in a real example:

Starting with the 75 amper doing 75 amps from a Honda 3000 with battery voltage seen as 14.08---

75 x 14.08 = 1056 output watts. Say 85% converter efficiency, input would be 1242w and with 0.7PF demand from the gen would be 1775VA

Kill-A-Watt said 123.8v, 13.64a, 1241w, 1690VA, 0.73PF so not so much VA being 1690 vs 1775. But the watts was close at 1241 real vs 1242 in theory.

Using just the input vs output watts ( how they do efficiency) it was

1056/1241 = 85% so that is on spec for the 75 amp converter (PowerMax)

Using 0.7 instead of 0.73 VA would be 1773 vs 1701--KAW said 1690.

So it looks like you should do the efficiency separate from the PF to get VA.

Another live measurement, this time with the B&S P2200 gen on the same 75 amper the Kill-A-Watt said:

119v, 13.67a, 1150w, 1626VA, 0.70PF. I do not have the battery voltage at the time, but using the 85% efficiency, output would be 1150w x85 = 997w and 997/75 = 13.3a (would be near the start of the recharge)

What comes up there is the different gens for loaded voltage and the results from that. The Honda 3000 was 123.8v vs the 2200's 119v but amps was still 13.64 vs 13.67. PF was different at 0.7 vs 0.73

The Ryobi's loaded voltage with the 80 amper would be a factor in whatever a Kill-A-Watt would say about it all, but the general idea seems valid for estimating about 1900VA as posted earlier in the thread.

* This post was edited 10/04/20 12:33pm by BFL13 *

AllegroD

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Posted: 10/04/20 12:45pm Link  |  Quote  |  Print  |  Notify Moderator

Here is what we did. As someone recommended, if you can, test timing and draw in your driveway. Look at the RR data plate. Our Samsung RF18 sips at 3 amps. Some do sip a little more. Our MH had 2 GC2s at 230ah and a Tripp Lite rv1250ulhw inverter/charger. With nothing running but the RR (and parasitics), we last 10-12 hours, with outside of 75 degrees, in the sun. Fridge stays 34 and freezer at -2.

Our last off grid was only 4 nights. We had to run the Onan 7K 2 hours a.m. and 2 hours p.m. to bring batts back up

We recently changed to 2 Battleborn, 100A batts. Have not tested, yet.

What RR is in the rig?
How many and what batts do you have?

jaycocreek

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Posted: 10/04/20 12:59pm Link  |  Quote  |  Print  |  Notify Moderator

There's another option that some do,a stand alone portable battery charger...Something like the Noco genious 2600 would charge your batteries quickly and run in echo mode on the Honda..A top shelf portable charger...


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ajriding

st clair

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Posted: 10/05/20 10:09am Link  |  Quote  |  Print  |  Notify Moderator

Wow.
What a difference a couple 100w panels makes. None of this will ever be an issue for those of us with even the simplest of solar systems.

I just ordered a friend solar panels (200 watts total) and MPPT controller for $178 shipped. He has batts and only needs to wire it all up. Done! For the next 15-20 years he will have batts being charged and maintained. so, 178 divided by 20 = less than $9 per year... In 15-20 years one gallon of gas could be more than that.

Generator is only for running the AC now.

time2roll

Southern California

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Posted: 10/05/20 10:29am Link  |  Quote  |  Print  |  Notify Moderator

ajriding wrote:

Wow.
What a difference a couple 100w panels makes. None of this will ever be an issue for those of us with even the simplest of solar systems.

I just ordered a friend solar panels (200 watts total) and MPPT controller for $178 shipped. He has batts and only needs to wire it all up. Done! For the next 15-20 years he will have batts being charged and maintained. so, 178 divided by 20 = less than $9 per year... In 15-20 years one gallon of gas could be more than that.

Generator is only for running the AC now.
I have read reports 500+ watts solar is needed with a residential fridge to avoid using a generator.

Otherwise yes 200 watts goes a long way to reduce generator run time.

ajriding

st clair

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Posted: 10/05/20 07:06pm Link  |  Quote  |  Print  |  Notify Moderator

time to roll, 100 is plenty for a propane fridge. Almost nobody will boondock with residential electric appliances. You could probably use a few Duracell C or D batteries to run a propane fridge.
Propane packs more power than a battery ever will. Gasoline packs a lot of power, but is not efficient way to run a propane fridge on 120v. The propane is just a little candle flame, and that is all that is needed to have a fridge.

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