Whats wrong with this system??

[msalari]

Perfect, thanks

[msalari]

I'd say you need to rethink the whole system. I'd say you need 3 of those panels, a real charge controller, and a battery bank of 2, 6V 100ah golf cart batteries (wired in series for 12V)

Thanks Mike90250
Lets assume for a second that the MPPT charge controller is real. If I did decide to go with the 6V battery plan. Can I charge them with my 24V/115W panels ? The charge controller has a setting for 12/24V systems - so regular 12V batteries are fine - but the system will still work OK with parallel-connected 6's ?

Thanks

[Mike90250]

Thanks Mike90250
Lets assume for a second that the MPPT charge controller is real. If I did decide to go with the 6V battery plan. Can I charge them with my 24V/115W panels ? The charge controller has a setting for 12/24V systems - so regular 12V batteries are fine - but the system will still work OK with parallel-connected 6's ?

Thanks

No. Parallel 6v battery will not work. My original suggestion was

battery bank of 2, 6V 100ah golf cart batteries (wired in series for 12V)

6ga wire is marginal, I would use at least 4ga, it's the starting surge that's killing you, and you have to get that resolved.

[msalari]

Sorry, I meant series, I'm so used to wiring the 12s in parallel for the amps. But good to know the controller won't know the difference. Thanks again.

[joerossjr]

Sorry, I meant series, I'm so used to wiring the 12s in parallel for the amps. But good to know the controller won't know the difference. Thanks again.

Just to be clear... you mean the Controller will not know HOW you connected the batteries, only the Voltage/current it see... THAT"S what you understand and were repeating back?

[msalari]

Yes correct, i should have been more clear:
I have an opportunity to buy some AGM batteries at a great price - same AHrs that i have today but they are 6v instead of 12.
Wiring them in series, sounds like my controller should not know the difference. So thanks again.

Next question: I'm reading lots of advantages for AGM: seems like AGM could have put up with my undercharging current (if I didn't already invest in the new panels - oh well doesn't hurt).
And they can put up with freezing too - I'm hoping this means that I could leave them at the cabin for the winter and only cause marginal damage. Hauling batteries in and out of the place every year was proving to be a real pain.
But I cannot find ANY disadvantages for AGM, other than cost. Seem to good to be true?
Thanks guys

[SunEagle]

Yes correct, i should have been more clear:
I have an opportunity to buy some AGM batteries at a great price - same AHrs that i have today but they are 6v instead of 12.
Wiring them in series, sounds like my controller should not know the difference. So thanks again.

Next question: I'm reading lots of advantages for AGM: seems like AGM could have put up with my undercharging current (if I didn't already invest in the new panels - oh well doesn't hurt).
And they can put up with freezing too - I'm hoping this means that I could leave them at the cabin for the winter and only cause marginal damage. Hauling batteries in and out of the place every year was proving to be a real pain.
But I cannot find ANY disadvantages for AGM, other than cost. Seem to good to be true?
Thanks guys

AGM's cost more than FLA and can have a shorter life depending on how they are used. Not if those "cons" are worse then the "pros" but for some people it is.

[Sunking]

Next question: I'm reading lots of advantages for AGM: seems like AGM could have put up with my undercharging current (if I didn't already invest in the new panels - oh well doesn't hurt).
And they can put up with freezing too - I'm hoping this means that I could leave them at the cabin for the winter and only cause marginal damage. Hauling batteries in and out of the place every year was proving to be a real pain.
But I cannot find ANY disadvantages for AGM, other than cost. Seem to good to be true?
Thanks guys

Every battery has advantages and disadvantages. You hit on the main disadvantage, but do not realize what it really means.

• AGM cost more than FLA, about twice that of FLA for a given capacity. But you missed they only last about half as long as FLA. So in the end using AGM is about 400% higher in cost.
• Cannot accurately determine battery health and state of charge because you cannot access the electrolyte.
• Prone to thermal runaway. That leads to venting , fire, and explosion. Using Temperature Compensate can help minimize the risk, but added cost.
• If over charged and vents, permanent damage and capacity lost forever. Again due to you cannot access the electrolyte.

If you use AGM you need to understand that so you can justify the cost. Learning that lesson after the fact can be quite painful. So what are some of the reasons to use AGM?

• In rough handling mobile applications where a spill is not acceptable. This is why they were invented for the aerospace industry
• Where extremely high Charge/Discharge rates are encountered. As a general rule AGM can handle C/4. But there are models made that can go as high as 4C used in UPS or Rocket Engines.
• In extreme cold climates. By cold I mean -40F. Even a FLA can withstand extreme cold if fully charged and kept charged on a Float charger.
• Enclosed cabinets where hydrogen accumulation could be dangerous. This is one reason why UPS use them because the batteries are often inside an equipment cabinet.
• Although the gain is small, AGM has higher Energy Density meaning it is a little lighter in weight than an equal capacity FLA. Also a little smaller in volume.

So there are significant disadvantages to using AGM. You just were not looking for them very hard. AGM certainly has its place and applications, but you need to know what you are asking for.

[msalari]

Thanks again guys - I am certainly willing to deal with all of these potential issues. Again, I'm talking about a cabin running ~30 cycles per year. And if these last me 6 years instead of 12, I'm good.

thanks

[SunEagle]

Thanks again guys - I am certainly willing to deal with all of these potential issues. Again, I'm talking about a cabin running ~30 cycles per year. And if these last me 6 years instead of 12, I'm good.

thanks

I would expect those batteries to last maybe 3 to 4 years but hard to imagine 6 and never 12.

[Raul]

I got yuasa agm that have been in ups for 4 years . Bought them used and hammered them on a of grid for nearly 2 ears now , gues what ? They still as strong as I got them and the new bank I bought to replace I think I done it to soon as this agm's are not giving up. They start and run my 1100w well pump with a 1200w inverter and hardly any voltage sag.
If the batteries are looked after can have a longer life than predicted .

[SunEagle]

You have an interesting set of batteries. Most of the ones found in a UPS last about 5 years if they are not discharged more than a dozen times. But if yours work then you have something other than normal.

[jflorey2]

I got yuasa agm that have been in ups for 4 years . Bought them used and hammered them on a of grid for nearly 2 ears now , gues what ? They still as strong as I got them and the new bank I bought to replace I think I done it to soon as this agm's are not giving up. They start and run my 1100w well pump with a 1200w inverter and hardly any voltage sag.
If the batteries are looked after can have a longer life than predicted .

Then you have a different experience than everyone else who uses them. (And many of those people look after their batteries.)

[Raul]

They been use as back up for a big server, so, 4 years on float with a handful of cycles, then I got them I made sure I get a complete absorb at least every other day , PV large enough to cover my day use and charging capacity ; most days go into absorb by 10-11am and they can take c/5 so it must be the fact that they stand a better chance of fully charging within a narrow window.
When I get to my holiday place , I will take some pictures of the old set up before I install my new bank. I will dig my old thread and update there.

[Sunking]

I got yuasa agm that have been in ups for 4 years . Bought them used and hammered them on a of grid for nearly 2 ears now , gues what ? They still as strong as I got them and the new bank I bought to replace I think I done it to soon as this agm's are not giving up. They start and run my 1100w well pump with a 1200w inverter and hardly any voltage sag.
If the batteries are looked after can have a longer life than predicted .

I bet you have never done a Discharge test.They cost several thousand dollars to perform.