24v to 48v Conversion

[D90Don]

I currently have a 24v Off-grid System. Battery bank is 24v Rolls FLA and it is about 9 years old. Getting Cloudy up here this time of year and the generator is running more than usual. I have a FM60 Outback Controller and an FX2024 Outback Inverter. I definitely plan on going LiFePO4 for the new battery bank and I'm leaning toward the SOK Brand. And I'm fairly certain I can use my current FM60 Controller for a 48v System. But my big question is should I stay loyal to "Outback" for the new 48v Inverter (since I already have the FM60 Controller), or are there better options out there. I'm not married to Outback, but they seemed to have performed well over the past 9 years, so that has built some loyalty on my part.

I know I will also probably have to upgrade to the Mate3S, as well if I go 48v. Outside of the LiFePO4 battery bank, we are probably looking at $2500 minimum for the 48v Outback Inverter and new Mate3S. I'm not sure what is the most logical path at this point. Stick with 24volts on the SOK battery bank since I already have the Controller and Inverter set up for 24v? Or go all in, and purchase the new Inverter and Mate3S with the 48v Battery Bank?

Open to all input and options. Thanks everyone in advance.
Don

 

[sunshine_eggo]

I'm a HUGE fan of sticking with what works. Do you need 48V or more power?

Outback is a good company. My neighbor has two FM80 controllers that have performed very well running 2kW PV each into his 24V 1000Ah FLA.

 

[Supervstech]

Are you running genny more because of battery capacity? Not enough sun.?


Do you struggle with loads with your existing 24v setup?

 

[KITROBASKIN]

We lost our 24V Outback inverter to lightning. It was a simple plug and play to get the updated inverter, having the Midnite Solar back panel with necessary bus bars and breakers. The updated interface box (Mate) was an expense but everything works.

My suggestion is to stick with your inverter until it falters. Purchase LFP batteries in a configuration that will allow you to use them as a 24V system OR 48V. (not an odd number of 24V batteries)

You can price the option of going with 48V batteries and down-converting the voltage to 24V for now(?)

Congratulations on the long life of your flooded lead acid batteries.

 

[SparkyJJO]

If You replace the inverter with another outback, I see no reason to replace your existing Mate3S. Those are not voltage specific.

 

[chrisski]

I just got an Outback 8048 Radian. I have done some load testing and this has turned on a 4 ton 240 volt AC unit with a motor rated at 20 amps running and over 100 amps starting. The only thing limiting me is the amount of batteries I'm willing to buy to run to keep that heavy load running in the summer.

A couple of days ago I "moved" to that Outback grid tied system for my house from a much smaller RV Victron setup, and there is a bit of a learning curve.

If permitting is an issue, than the Outback could be the way to go to simplify things.

For the Victron I have in the RV, I upgraded from 12 volts. I thought about a 48 volt system, but a lot of what I had put in for the 12 volt build could not handle 48 volts. Not only were the MPPTs I purchased not 48 VDC compatible, but the fuses and the Blue Sea switch. I also needed step down to run 12 volt accessories at 50 amps. I could not find a reputable brand at 48 volts. 12 volt accessories are easy to find, 24 volt accessories few and far between, and you're blazing new trails finding accessories at 48 volts. For me a 48 VDC upgrade would have been a bit of work.

 

[D90Don]

Are you running genny more because of battery capacity? Not enough sun.?


Do you struggle with loads with your existing 24v setup?

Yes, we have an 8kw Generac (older model), and have had to run it every 2 days to bring the Rolls FLAs up to charge. Last winter, We ran the generator only once per month and that was more to exercise the Generac than charge the batteries. We only have the LED lights, fridge, and washing machine in the cabin, so not a huge draw, but it seems FLA Batteries are showing their age.

 

[D90Don]

I'm a HUGE fan of sticking with what works. Do you need 48V or more power?

Outback is a good company. My neighbor has two FM80 controllers that have performed very well running 2kW PV each into his 24V 1000Ah FLA.

Thanks for your input SunshineEggo. Sticking with a 24v system definitely seems to be the cheapest route and least brain cells burnt. But those 48v SOK Racks look so tempting. Price of the new batteries doesn't so much bother me, but buying new 48v inverter does, not sure why.

 

[D90Don]

If You replace the inverter with another outback, I see no reason to replace your existing Mate3S. Those are not voltage specific.

I have the original "Mate" or Mate 1.. I thought that the original Mate wouldn't handle 48v systems.

 

[D90Don]

I just got an Outback 8048 Radian. I have done some load testing and this has turned on a 4 ton 240 volt AC unit with a motor rated at 20 amps running and over 100 amps starting. The only thing limiting me is the amount of batteries I'm willing to buy to run to keep that heavy load running in the summer.

A couple of days ago I "moved" to that Outback grid tied system for my house from a much smaller RV Victron setup, and there is a bit of a learning curve.

If permitting is an issue, than the Outback could be the way to go to simplify things.

For the Victron I have in the RV, I upgraded from 12 volts. I thought about a 48 volt system, but a lot of what I had put in for the 12 volt build could not handle 48 volts. Not only were the MPPTs I purchased not 48 VDC compatible, but the fuses and the Blue Sea switch. I also needed step down to run 12 volt accessories at 50 amps. I could not find a reputable brand at 48 volts. 12 volt accessories are easy to find, 24 volt accessories few and far between, and you're blazing new trails finding accessories at 48 volts. For me a 48 VDC upgrade would have been a bit of work.

Crisski, Glad to hear you are happy with your 8048 Radian. I'm not grid tied, but do have 8kw Generac, PV array, and a Hydro DC Gen input. So yes there is a learning curve. I'm reading more about this combo Invert-Controllers. Some of them seem half the price of just the Outback 48v Inverter. Still on the fence, but starting to lean toward staying 24v with LiFePO4s. Or temporarily stay with 24v with keeping the door open to future upgrade as @KITROBASKIN suggested.

 

[D90Don]

If You replace the inverter with another outback, I see no reason to replace your existing Mate3S. Those are not voltage specific.

Ok, Thank you for that. Not sure why I went down that path thinking I would need a newer Mate.

 

[D90Don]

We lost our 24V Outback inverter to lightning. It was a simple plug and play to get the updated inverter, having the Midnite Solar back panel with necessary bus bars and breakers. The updated interface box (Mate) was an expense but everything works.

My suggestion is to stick with your inverter until it falters. Purchase LFP batteries in a configuration that will allow you to use them as a 24V system OR 48V. (not an odd number of 24V batteries)

You can price the option of going with 48V batteries and down-converting the voltage to 24V for now(?)

Congratulations on the long life of your flooded lead acid batteries.

Kitrobaskin, Thank you for the well thought out recommendation. Since the technology is moving forward so rapidly, get an even number of 24v LiFePO4s and wire them in parallel for now. I can always wire them up in series in the future if I decide to go 48v or if the current 24v Inverter fails. Thanks again! One a side note, is it a consideration, if the LiFePO4 batteries are 2-3 years old, and then you decide to tie them into newly purchased batteries? Would doing so, reduce the life of the new batteries when they try to "balance?" Is this a consideration for LFP or only FLA?

 

[SparkyJJO]

I have the original "Mate" or Mate 1.. I thought that the original Mate wouldn't handle 48v systems.

Ahhhh ok. I don't know about that.

 

[yodamota]

I think if you are looking to spend some cash, Id suggest getting another 60 amp outback charge controller along with a set of panels.

 

[D90Don]

I think if you are looking to spend some cash, Id suggest getting another 60 amp outback charge controller along with a set of panels.

I hear what you are saying, yodamota. I'd like to upgrade the panels as well, but the (6) 240 watt Panels seem to do a great job when the sun is out (May - Nov). Seven days straight of overcast in the Pacific Northwest, on the other hand, not so much. (6-8) 400 watt panels definitely would be "more" better, but possibly more than I currently would use. I guess it just boils down to how much cash do I want to spend to upgrade everything, or just fix the battery storage problem that the older FLA batteries are currently giving me. I had not considered the FM60 Controller's limitations, but from what you recommend, I'm seeing the FM60 can only handle about 1500 watts from a PV array in a 24v system. Thanks for pointing that out.

 

[Q-Dog]

If the existing inverter meets your needs I see no reason to go to 48 volt.

 

[KITROBASKIN]

Perhaps another member will provide more details regarding adding on more LFP after a few years. While not ideal, I think it is doable, especially with a reconfiguration that equalizes old with new?

Asking that then brings up the question whether you anticipate needing more for future increased loads. If you are very much going to get more devices that need power, then perhaps you can get the batteries you need now? Of course money is a factor, but if you get more batteries when your funds replenish (every 6 months or so?) then the relative age difference would be ok I would think.

I’m going to ping @Hedges

 

[yodamota]

I hear what you are saying, yodamota. I'd like to upgrade the panels as well, but the (6) 240 watt Panels seem to do a great job when the sun is out (May - Nov). Seven days straight of overcast in the Pacific Northwest, on the other hand, not so much. (6-8) 400 watt panels definitely would be "more" better, but possibly more than I currently would use. I guess it just boils down to how much cash do I want to spend to upgrade everything, or just fix the battery storage problem that the older FLA batteries are currently giving me. I had not considered the FM60 Controller's limitations, but from what you recommend, I'm seeing the FM60 can only handle about 1500 watts from a PV array in a 24v system. Thanks for pointing that out.

Living in the PNW I know what you are talking about, we just had 11 days with no sun...

The biggest upgrade for us has been adding more panels. We went from 2000w to 6500w this year. Made a huge difference. The next upgrade will be lithium for us.

 

[Hedges]

I don't use lithium, but I don't think having old and new (or larger Ah and smaller Ah) in parallel is a problem.
But perhaps is will affect current sharing. If all you want is capacity, not a problem; they should catch up at the knee of the curve if not before. If you need significant current from all banks because you draw too much from one, I'd think over-current trip more likely.

Make sure voltage is similar to avoid high current, maybe connect through a resistance, even long run of wire.

 

[D90Don]

I don't use lithium, but I don't think having old and new (or larger Ah and smaller Ah) in parallel is a problem.
But perhaps is will affect current sharing. If all you want is capacity, not a problem; they should catch up at the knee of the curve if not before. If you need significant current from all banks because you draw too much from one, I'd think over-current trip more likely.

Make sure voltage is similar to avoid high current, maybe connect through a resistance, even long run of wire.

@Hedges, Thank you for your input! Don