24v Bank Dead - upgrade to 24v LiFe or scrap system for 48v - WANTED recommendations

[robbertwilliams]

Hi,

Current system:
Solar array 1700w wired s/p to get about 60v at the charge controller
8 L16 FLA Batteries wired s/p to get 740ah (installed in 2013)
Midnite Solar Classic 150
Schneider Electric SW2524 Inverter

Situation:
Off grid yurt - we consume about 2-2.5 kwh/day and hope to use more in future (add full size fridge) The batteries are pretty much toast - cases are deforming and low voltage shutoff happening when running coffee kettle next morning after a previous day of full charge. This is more or less a somewhat temporary living situation we are currently in but if an actual structure is built - we will remain off grid here for years to come. There is also an electronics smell - I have not been able to isolate it to the inverter or charge controller - so quite possible one of the two are on their way out.

Been looking at replacing with (2) eg4 24v 200ah (version 2). But I don't see too much of a future with 24v options in the solar market - so I'd hate to get these batteries and have the inverter die on me and be limited with replacement options in the future.

Looking for some perspective...different than mine - it seems I get my blinders on when researching this on the laptop...not quite the same as in person shopping nor does it appear that there's a one stop shop to view/analyze all the options. Anyways, would love recommendations - should I stick with the 24v current setup w/new batteries (also, if someone has another battery to recommend for same price point? not going to DIY it)? Or make switch to 48v and have to get batteries, charge controller, inverter (suggestions please on all)?

I'm sure I've left out some necessary details.

Thanks

 

[sunshine_eggo]

Do you ever expect the system to provide more than 4000W of power?

If not, 24V is fine. The Schneider is a solid unit, and it sounds like just your batteries are broken. In good conditions, your array should be able to provide 8kWh/day. In winter... maybe 2-3kWh. Of course, this assumes you have high solar availability and aren't dealing with shade/partial shade.

 

[SoggyShoes]

I don't think 24V is going away anytime soon. Right now it seems to be a sweet spot in RV (kind of a Goldilocks between 12V & 48V). In fact, over the last couple of years it seems there are more 24V batteries and options on the market, not less.

 

[50ShadesOfDirt]

The existing system seems to be old? If the existing 24v inverter wasn't high quality to start with (a LF magnum, etc.), then this would be an ideal time to flip over to 48v & LiFePO4, unless the higher costs of 48v are holding you back. In that case only, a 24v system might be appropriate.

I'm running a LF 24v magnum (4024), and it is still going strong after 5+ years. But, 24v limits me to my current battery-bank size of 2x 12v300ah batteries in series (LiTime, and they also offer now a 400ah size), and I parallel two of those banks with busbars to get 600Ah total. And that about maxes things out, unless I do more busbar magic, and hope it all stays balanced. That's roughly 14kWh, so you can decide if you'll never exceed that, and perhaps 24v would serve you as well. We run the entire house on 24v, 4000w, and have a gennie behind the magnum, if ever a larger load needs power.

Otherwise, go 48v from the start, as you can keep slapping 48v100Ah batteries into the rack-mount, almost indefinitely ... whereas, with 24v, sooner or later the battery-bank configurations max out ...

Hope this helps ...

 

[Mattb4]

... But, 24v limits me to my current battery-bank size of 2x 12v300ah batteries in series (LiTime, and they also offer now a 400ah size), and I parallel two of those banks with busbars to get 600Ah total. And that about maxes things out, unless I do more busbar magic, and hope it all stays balanced. ...

While the bus bars might limit the maximum amps available to feed loads it does not really limit the total battery amp hours. At 600 amps your loads would be limited to 600a X 24vDC =14.4kW.

Keeping your batteries balanced however is another story. I suspect the best practice here is to always avoid series connecting lower battery voltage units to get the needed 24vDC ( 2 -12vDC batteries with their own BMS) and also watch how you wire the 24vDC batteries in parallel.

 

[robbob2112]

The existing system seems to be old? If the existing 24v inverter wasn't high quality to start with (a LF magnum, etc.), then this would be an ideal time to flip over to 48v & LiFePO4, unless the higher costs of 48v are holding you back. In that case only, a 24v system might be appropriate.

I'm running a LF 24v magnum (4024), and it is still going strong after 5+ years. But, 24v limits me to my current battery-bank size of 2x 12v300ah batteries in series (LiTime, and they also offer now a 400ah size), and I parallel two of those banks with busbars to get 600Ah total. And that about maxes things out, unless I do more busbar magic, and hope it all stays balanced. That's roughly 14kWh, so you can decide if you'll never exceed that, and perhaps 24v would serve you as well. We run the entire house on 24v, 4000w, and have a gennie behind the magnum, if ever a larger load needs power.

Otherwise, go 48v from the start, as you can keep slapping 48v100Ah batteries into the rack-mount, almost indefinitely ... whereas, with 24v, sooner or later the battery-bank configurations max out ...

Hope this helps ...

If you don't already have it, get an active balancer to prevent them from drifting apart. They are pretty inexpensive and save a lot of trouble.

 

[robbob2112]

Do you ever expect the system to provide more than 4000W of power?

If not, 24V is fine. The Schneider is a solid unit, and it sounds like just your batteries are broken. In good conditions, your array should be able to provide 8kWh/day. In winter... maybe 2-3kWh. Of course, this assumes you have high solar availability and aren't dealing with shade/partial shade.

I'm with Eggo here for the most part.
If you have the money to upgrade to 48v and every think you will need higher power then do it now verse later.
If you KNOW you will never want more power think hard about it then stick with the 24v

That said I lean towards 48v, but my needs are not your needs.

 

[Q-Dog]

The existing system seems to be old? If the existing 24v inverter wasn't high quality to start with (a LF magnum, etc.), then this would be an ideal time to flip over to 48v & LiFePO4, unless the higher costs of 48v are holding you back. In that case only, a 24v system might be appropriate.

I'm running a LF 24v magnum (4024), and it is still going strong after 5+ years. But, 24v limits me to my current battery-bank size of 2x 12v300ah batteries in series (LiTime, and they also offer now a 400ah size), and I parallel two of those banks with busbars to get 600Ah total. And that about maxes things out, unless I do more busbar magic, and hope it all stays balanced. That's roughly 14kWh, so you can decide if you'll never exceed that, and perhaps 24v would serve you as well. We run the entire house on 24v, 4000w, and have a gennie behind the magnum, if ever a larger load needs power.

Otherwise, go 48v from the start, as you can keep slapping 48v100Ah batteries into the rack-mount, almost indefinitely ... whereas, with 24v, sooner or later the battery-bank configurations max out ...

Hope this helps ...

I don't know why you think this. There is no reason one can't keep adding batteries to a 24 volt system, same as a 48 volt system.

I have 800ah of 24 volt batteries and have no reservations adding more if I need to.

 

[50ShadesOfDirt]

The complexity involved in 48v rack-mount batteries is: ... add another one, done.

The complexity involved in my 24v battery-bank (of 12v batteries) is: series the 1st two, add busbars, series the next two, parallel both series.

Pairing (paralleling) the first two sets of batteries was ok, but not as easy as dropping another 48v in the rack. Ensuring that all series'd batteries are doing the right thing (charge or recharge) after the 1st two sets, adds more complexity.

They make loads of 12v (not rack-mount) and 48v (rack-mount) batteries ... not as many options in 24v, and even fewer in rack-mount form; it's moot for me as I started with a pair of 12v, with 1000's of cycles left to go. OP seems to have started with something similar, and I think he's now leaning towards a single 48v (rack-mount) battery to start.

If only I could trade in my 12v's, like some folks trade in their older cars, for a new 48v ...

 

[sunshine_eggo]

The complexity involved in 48v rack-mount batteries is: ... add another one, done.

The complexity involved in my 24v battery-bank (of 12v batteries) is: series the 1st two, add busbars, series the next two, parallel both series.

Pairing (paralleling) the first two sets of batteries was ok, but not as easy as dropping another 48v in the rack. Ensuring that all series'd batteries are doing the right thing (charge or recharge) after the 1st two sets, adds more complexity.

They make loads of 12v (not rack-mount) and 48v (rack-mount) batteries ... not as many options in 24v, and even fewer in rack-mount form; it's moot for me as I started with a pair of 12v, with 1000's of cycles left to go. OP seems to have started with something similar, and I think he's now leaning towards a single 48v (rack-mount) battery to start.

If only I could trade in my 12v's, like some folks trade in their older cars, for a new 48v ...

This is self-imposed limitation of your chosen configuration. It's not a property of 24V systems.

The OP is proposing using 24V/200Ah rack mount batteries. Capacity expansion should be no more complex than your perception of adding more 48V rack mount batteries.