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 > Inverter in repurposed generator locatoin with agm batteries

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dave17352

Ne

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Joined: 09/20/2004

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Posted: 06/28/19 05:15am Link  |  Quote  |  Print  |  Notify Moderator

Thanks all for the opinions. I have ordered my new Epever 30 amp mppt controller and new solar panel. Going in series and mppt should double my panel output. [emoticon] WAX I may put the mppt in the cabin for just your reason. I have ordered a 12 volt fan for the comppartment temperature controlled. All though all this may not get much use it sure is fun. I enjoy messing with solar!
thanks
Dave


2005 Forrest River Cardinal 29rkle FW
1998 Lance 980 11'3" TC
2017 CHEVY 3500 SRW 6.0
[email protected] turnover ball @ companion Hitch
Honda eu3000 generator mounted on cargo rack
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Crestliner 1850 Fish Ski boat mostly fishing now!
Renogy 200 Watt solar

2oldman

Ca

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Posted: 06/28/19 12:19pm Link  |  Quote  |  Print  |  Notify Moderator

dave17352 wrote:

Going in series and mppt should double my panel output.
not sure what you mean by this..

Adding another panel will double your output.

dave17352

Ne

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Posted: 06/28/19 04:29pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

dave17352 wrote:

Going in series and mppt should double my panel output.
not sure what you mean by this..

Adding another panel will double your output.


Right now I have 2 100 watt panels with a pwm charger so max I can get is about 10 amps. With 3 100 panels and ( I am adding one) and a MTTP charger I can utilize all the volts. So lets say I am drawing 270 watts /13 volts roughly 20 amps. The mttp charger makes all the difference. I guess I should have said by going with the mttp and adding one panel I can harvest twice the energy. [emoticon]

2oldman

Ca

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Posted: 06/28/19 04:51pm Link  |  Quote  |  Print  |  Notify Moderator

It's mppt, and they help harvest more amps, but not as much as you may think. 10 to 40% is the usual gain, of course your Pwm could be a dog. I thought you said you were going series..

MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 06/28/19 05:03pm Link  |  Quote  |  Print  |  Notify Moderator

AGM batteries WILL VENT (out gas) under "extreme overcharging". If they did not, they would explode.

Recombinant caps that change vapor back into liquid really subdues pressure build up. You've got to, with your own hands, work with these batteries to get a better understanding of the subject. And the likelihood or not of malfunction.


I have rehabilitated many different group sizes to above 17 volts and only two, vented. Both were not Lifelines. Do not rehab an AGM while still in the rig.

The last battery explosion I saw was on an older Tioga. Owners started the generator, connected a transformer battery charger, then ventured to a beach bar. Gor plastered. People started yelling. They heard a pop and then a sulfur reek covered the beach like Yellowstone Park. it was unbreathable near or inside the rig. The batteries were outside.

What a mess.

They were in no mood to discuss anything the next day. They fiddled with the batteries, got a jumo start then headed north.

BFL13

Victoria, BC

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Posted: 06/28/19 05:31pm Link  |  Quote  |  Print  |  Notify Moderator

dave17352 wrote:

2oldman wrote:

dave17352 wrote:

Going in series and mppt should double my panel output.
not sure what you mean by this..

Adding another panel will double your output.


Right now I have 2 100 watt panels with a pwm charger so max I can get is about 10 amps. With 3 100 panels and ( I am adding one) and a MTTP charger I can utilize all the volts. So lets say I am drawing 270 watts /13 volts roughly 20 amps. The mttp charger makes all the difference. I guess I should have said by going with the mttp and adding one panel I can harvest twice the energy. [emoticon]


Actual results--three 100w panels in parallel with PWM aimed at high sun, you get 6.2 amps (same as Isc) each for 18.6 amps. Swap to an MPPT controller with them in parallel--still 18-19 amps, change to series with the MPPT, still 18-19 amps.

You lose panel watts from panel heating, so your MPPT "advantage" disappears. You can get a little more amps with MPPT when the battery is low, but not enough to change your day's haul of AH that you would notice between battery 13 and 14.5 volts like you see RVing.


1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
See Profile for House electronics set-up.

dave17352

Ne

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Posted: 06/28/19 06:02pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

dave17352 wrote:

2oldman wrote:

dave17352 wrote:

Going in series and mppt should double my panel output.
not sure what you mean by this..

Adding another panel will double your output.


Right now I have 2 100 watt panels with a pwm charger so max I can get is about 10 amps. With 3 100 panels and ( I am adding one) and a MTTP charger I can utilize all the volts. So lets say I am drawing 270 watts /13 volts roughly 20 amps. The mttp charger makes all the difference. I guess I should have said by going with the mttp and adding one panel I can harvest twice the energy. [emoticon]


Actual results--three 100w panels in parallel with PWM aimed at high sun, you get 6.2 amps (same as Isc) each for 18.6 amps. Swap to an MPPT controller with them in parallel--still 18-19 amps, change to series with the MPPT, still 18-19 amps.

You lose panel watts from panel heating, so your MPPT "advantage" disappears. You can get a little more amps with MPPT when the battery is low, but not enough to change your day's haul of AH that you would notice between battery 13 and 14.5 volts like you see RVing.


dave17352

Ne

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Joined: 09/20/2004

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Posted: 06/28/19 06:31pm Link  |  Quote  |  Print  |  Notify Moderator

dave17352 wrote:

BFL13 wrote:

dave17352 wrote:

2oldman wrote:

dave17352 wrote:

Going in series and mppt should double my panel output.
not sure what you mean by this..

Adding another panel will double your output.


Right now I have 2 100 watt panels with a pwm charger so max I can get is about 10 amps. With 3 100 panels and ( I am adding one) and a MTTP charger I can utilize all the volts. So lets say I am drawing 270 watts /14 volts roughly 20 amps. The mttp charger makes all the difference. I guess I should have said by going with the mttp and adding one panel I can harvest twice the energy. [emoticon]


Actual results--three 100w panels in parallel with PWM aimed at high sun, you get 6.2 amps (same as Isc) each for 18.6 amps. Swap to an MPPT controller with them in parallel--still 18-19 amps, change to series with the MPPT, still 18-19 amps.

You lose panel watts from panel heating, so your MPPT "advantage" disappears. You can get a little more amps with MPPT when the battery is low, but not enough to change your day's haul of AH that you would notice between battery 13 and 14.5 volts like you see RVing.


I am going to be going in series with these panels now. My Panels are rated and 5.29 amps at 18.9 volts. I have used these panels for two years and the most I ever get is 10 amps. With these panels in series at peak light I hope to get close to 270/14= 19.28 amps. I think I will gain about 5 amps overall. But we will see and I will update how many amps I see. I have done a lot reading on the net and it seems to be the concensus that series and mppt will net me a worthwhile gain.

You seem to be saying the extra voltage over the charging voltage is of no value. Interesting.

2oldman

Ca

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Posted: 06/28/19 06:39pm Link  |  Quote  |  Print  |  Notify Moderator

dave17352 wrote:



You seem to be saying the extra voltage over the charging voltage is of no value. Interesting.
I'm not sure what he's saying, but the general idea is that mppt does a better job of conservation of watts. I personally like to feed them as much voltage as they can take.

BFL13

Victoria, BC

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Posted: 06/28/19 06:58pm Link  |  Quote  |  Print  |  Notify Moderator

With PWM you get Isc value for amps to the battery. Flat on roof will not get as many as aimed.

With MPPT it is all about watts. Let's say you have 300w aimed (series or parallel makes no diff) You lose 10% of your watts due to panel heating. So now you are at your 270 watts. Lose say 2% wiring loss from array to controller (which is pretty good) Now at 264.6 watts. Controller efficiency say 97% (it could be more like 95%) so now at 256.7 watts output.

Amps to battery is output watts/ battery voltage (assuming no wiring loss on that leg)

258/13 = 19.8
258/13.5 =19.1
258/14 = 18.4

With panels flat on roof you start with less than 300 then lose the 10% for heat and go from there.

The PWM does not lose amps from heat, in fact amps go up slightly, so you don't lose. Still get same as whatever Isc is at the time.

Only good reason to get MPPT instead of PWM for that sort of work is if you get one 300w panel instead of three 100s. Now you must have MPPT to get the buck converter in it so you can go from 24v panel to 12v battery.

And, in the above calculation where controller efficiency is mentioned, don't forget the efficiency is lower when dropping voltage, so 24-12 loses more than 12-12. That might be a good reason to stay in parallel with the three 100s and MPPT.

However, it can be wiring gauge that makes a practical difference to your installation plan. Just don't expect a bunch of amps that won't ever happen in real life.

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