Questions on upgrading solar on travel trailer

[Mcstiggens]

They're not more efficient per se.

The inverters and equipment are about as efficient as the others. The benefits come from:

1) needing less copper for the same efficiency.
2) needing less MPPT charge current for a given array power.

Yea that. And also less time to recharge batteries. That is huge.

 

[Mcstiggens]

So now it comes full circle back to this; what are the limitations to the stock Furrion 25amp charge controller that is installed on my trailer and is it worth messing with? Can I get by with it while using 400 ah battery bank running my 12v fridge, furnace, lights and periphs?

Problem is, I still need to shop for an inverter/charge controller/ and on and on it goes. So now I'm basically BACK to square one

So,,,,can anyone recommend a good all in one Inverter/charge controller/transfer unit for a 12V system? Everything I see that matches the description is only for 24V and up

 

[sunshine_eggo]

Yea that. And also less time to recharge batteries. That is huge.

Nope.

An array won't output more power at 12V, 24V or 48V. It will replenish the same amount of kWh over time. It simply needs less output current to do so at higher battery voltages.

1200W outputs 100A at 12V
1200W output 50A at 24V
1200W output 25A at 48V

 

[sunshine_eggo]

So,,,,can anyone recommend a good all in one Inverter/charge controller/transfer unit for a 12V system? Everything I see that matches the description is only for 24V and up

Not many 12V AiO options out there.

 

[Mcstiggens]

Nope.

An array won't output more power at 12V, 24V or 48V. It will replenish the same amount of kWh over time. It simply needs less output current to do so at higher battery voltages.

1200W outputs 100A at 12V
1200W output 50A at 24V
1200W output 25A at 48V

I see. I was basing that off of this from Litime:

4X Charging Speed & Save 1/2 the Space】LiTime 48V 100Ah LiFePO4 battery has a max. 4.8kWh energy which equals to 4*12V 100Ah LiFePO4 batteries connected in series. It greatly reduces charging time from 20hrs to 5hrs (with 20A charging current), as you don't need to charge the 12V 100Ah battery one by one, and meanwhile saves you 1/2 the space, with fewer connection wires tangled to bother you.

But I guess they are referring to the fact that it is not multiple batteries, not that the 48V is faster at taking charge?

 

[sunshine_eggo]

I see. I was basing that off of this from Litime:

4X Charging Speed & Save 1/2 the Space】LiTime 48V 100Ah LiFePO4 battery has a max. 4.8kWh energy which equals to 4*12V 100Ah LiFePO4 batteries connected in series. It greatly reduces charging time from 20hrs to 5hrs (with 20A charging current), as you don't need to charge the 12V 100Ah battery one by one, and meanwhile saves you 1/2 the space, with fewer connection wires tangled to bother you.

But I guess they are referring to the fact that it is not multiple batteries, not that the 48V is faster at taking charge?

Let's say ANY 100Ah battery is rated for 50A charge.

That means:

a 12V/100Ah can take 12V * 50A = 600W
a 24V/100Ah can take 24V * 50A = 1200W

etc.

They can TAKE more POWER due to the higher voltage, but not more current.

 

[Mcstiggens]

Ugh... I'm getting dizzy from all this information overload. Think I'll just go take a nap and plan on using a generator for now

 

[sunshine_eggo]

Just remember that NOTHING comes for free.

POWER (Watts, kW) and ENERGY (Watt-hour, kWh) are NOT flexible.

Volts and Amps are flexible but only so much that Volts * Amps = Power

 

[sunshine_eggo]

@Mcstiggens

Alright buddy. I went and done it. I purged and reloaded my cart half a dozen times. Talked myself into and out of it... My sell job was so bad, the only reason I got sign off from the wife is that there was something about the same price that she's wanted (and I knew about it) for at least a year.

Whelp... we agreed we got each others' Xmas presents...

 

[JamesRich]

Thanks James for chiming in and sharing that. When you say 4 batteries? What size? Are they the 100 ah? If so, that is the same as I am starting out with (2X 200ah Litime batts). I don't need to run an A/C thankfully, just the furnace and fridge. I think I should be alright to get started. BUT now I really should look into the 24 VS 48 system. The longer this drags on, they more I realize I don't know/need to know. I hate hasty decision making.

Yes I have 4 100 ah litime batteries connected in parallel with 2aw jumpers I made myself. So yes the same capacity you will have with your two batteries. If you don't stay with 12 volts I'd jump straight to 48v. You will need a step down from 24 or 48, might as well go for 48. You could also go 48 and let your factory 12 volt charger power the 12 volt appliances. Only problem there is the inverter would have to be on all the time. Or run a separate single 12v house battery and run the inverter to charge it. Or dedicate a couple of panels and a separate mppt charger for just the 12 volt house battery.
James

 

[sunshine_eggo]

Whelp...

Mostly just posting to document my goal with this stoopid PowerMr unit...

I've tested 27 of 70+ LFP cells, and I'm on track to have about 5kWh available as I'd hoped. Results are pretty mixed - these are old abused CALB cells. They will be fine for these <400W average loads, but they'll probably perform poorly when I push them.

7.2kWh/day used in my office between two large desktop PCs, two medium end routers, modem, NAS, etc. Both outlets were monitored for over 48 hours, so it should be a decent approximation. This should be an upper end as I had a couple of small fans running most of the time that are only used intermittently.

Since I'll need at least 4 panels to attain minimum voltage for MPPT, that will put me at just over 1.1kW, which should perform very well to meet most of that 7.2kWh. I have 18 panels, so if I need more, I'll be good up to 9S, which will over-panel the MPPT.

 

[Daddy Tanuki]

only on the first page but think this needs to be said. anything that is "solar ready" from the factory in an RV is simply put, hot garbage. the wires are never beefy enough for a 12 volt system, and generally speaking not enough for even a 24 volt system. they might barely qualify for a 48 volt system.

that being said, if in the future you are considering going 48, then just do it. the savings in cables and connections alone will pay for the difference in price between 24 and 48. not only the that but the 48 volt inverter will be more efficient.

i will read the rest of this and comment more. @sunshine_eggo (waffle boy) knows his stuff pretty good. So if he and i give differing opinions go with his as we work differently.

PS: 12 years of solar camper in japan starting out at 12 volt and rapidly changing my mind when I could afford it, 8 years of solar cabin which I went straight to 48 with no screwing around.... (learned my lesson.)

 

[Pappion]

24v would be easier than 48v. More selection of inverters, solar controllers, and DC-12VDC converters. DC can sustain an arc, so the selection of a 48v (58v) battery cutoff switch needs attention. Same for fuses.
As for batteries, series wiring is not ideal. Battle Born will sell you a matched set. They also sell 24v batteries.