Inverter in repurposed generator locatoin with agm batteries

[dave17352]

I am thinking about upgrading my solar some and this is my plan.

I will locate my 2 agm deep cycles, 30 amp mppt solar controller and 2000 watt inverter all in the old generator location that I removed several years ago. Presently there is just one agm in there now.
The generator comppartmment is well vented as the orignal door is on the compartment. There is plenty of room for this equipment and air movement.

My concerns are

All though agm's should not out gas except if extreme overcharging occurs. It still makes me a little nervous.

The second concern is The propane compartment is above the genrator compartment. That kind of makes me nervous. Like what if the propane leaks and falls and kinda get side tracked into the generator compartment below. Of course the original design had the generator running below the propane:).

So what do you all think?

This is on my 98 Lance Truck Camper

Thanks
Dave

[marcsbigfoot20b]

The best part of MPPT and series panels is that 3 100 watt panels in series will be around ~57volts.
In parallel around ~18 volts.

Now throw in major overcast skies.

MPPT maybe half panel output......let’s say 27 volts.
PWM parallel half output .... maybe 9 volts.

MPPT will at least charge some amps.
PWM at 9 volts = nothing.

Even 3 amps is better than nothing for X hours.

[dave17352]

Ambient cooler and or cloudy days will still make for a cooler panel. Which will make for higher voltage. But of course if it is cloudy we won't be getting much current 😞

[BFL13]

With 6.2 Isc, you would get 12.4 aimed at high sun. Flat on roof is less due not being aimed. How much less depends on how high the sun is anyway, where you are at that time of year.

In May at 49N with a single 130w panel (8.2 Isc) and PWM I got 8.1 aimed and 5.1 flat at 10 am, and 8.3 aimed and 7.2 flat at high noon.

If you were there then, your 12.4 would be 7.2/8.3 x 12.4 = 10.75 at high noon.

Flat vs aimed less diff going South so at 23N on 21 June sun is overhead no diff.

Don't confuse ambient cool temps with panel heating temps. The panel gets hot in the sun even when it is not that hot out ambient. Just put your hand on the panel! I took some temps with my IR gun on the back of my tilted up panel aimed at the sun at different ambients, so I have seen how that works.

Yes, solar is interesting, plus it is even useful! 🙂

[dave17352]

BFL13 wrote:
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.

Well we will see. The higher voltage will have less resistance. I payed 89 bucks for the mppt and I can go from series to parallel if I want to get to the nitty gritty. But knowing that I was seeing 10 amps before if I see 18 to 20 now I will call it a win! 🙂 It is not always extremly hot when I am camping. Many times it is nice and cool which would negate the panel heating loss. All in all in will be a interesting experiment. Solar is fun that I know for sure.

[BFL13]

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.

[2oldman]

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.

[dave17352]

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. 🙂

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.

[dave17352]

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. 🙂

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.

[BFL13]

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. 🙂

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.

[MEXICOWANDERER]

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.

[2oldman]

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..

[dave17352]

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. 🙂

[2oldman]

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]

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. 🙂 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