24 or 48 volt Solar system?

[Madoxen]

Hi all just wondered if any of you might have some input as to the possible downfalls of a 48v solar setup rather than a 24v one.

I was looking at the Victron multiPlus -3000 or 5000 with 1800 to 2000w of panels on a 20' roof, The reason behind the 5000w version was that it would be nice to be able to drag my little ac/dc tig welder around the world with me for any possible repairs as i can link the multi plus to a small gen and it combines the out put to enable the high flow needed . ( not sure if 5000 would be possible with a burst rate of 10,000 or if it would need the 8000 with a 16,000 for short while. )
putting the Tig to one side we have a MB 1835 truck which is 24v the hab will be on Lithium home built bank to either suit 24v or 48v system , we are not electronics crazy as far as entertainment as we get all that from the out side world but we both love tools and fixing things so would like the ability to power them, although we are on 36v battery power tools, In the future we would also like to beable to charge E-Bikes either moto x or mountain bike style so would need to charge at least 2 at a time.

sorry if I have missed out any Key info please let me know if I have .

p.s ahh yes the 48V Multiplus is a reasonable amount cheaper than the 24v one.

 

[john61ct]

You will definitely need more 12V buck converters, but can find those cheap.

Maybe worth doing a whole separate 12V circuit for normal consumers, leave the 48V wiring dedicated for the specialist high power stuff.

Does not mean another bank, but then maybe you want to capture alt output.

Could be completely separate then, a 48-12V DC-DC **charger** is likely pricey.

My preference is stick to 12V for under 30-40' rigs, unless some special load device requiring higher, is itself really compelling.

Unless using high V DC for propulsion anyway. . .

 

[dreadlocks]

Higher Voltage with bigger systems is ALMOST always worth the trouble, however if you've already got a 24v truck, doing lithium, 2kw of solar, and expect rather frugal energy needs there is a strong argument for stopping at 24v and just building from there on out.. 12v loads can be on their own circuits but they need to remain rather small, large appliances like inverters, compressors, etc would be better suited by needing less amps, cabling losses, heat losses, etc.

If you were to do any bigger tho your almost at the tipping point where most would jump to 48v, especially with heavy AC load consumers like a friggin welder.

 

[Peter_n_Margaret]

For welding, I carry a Ready Welder 2 which is a 24V DC powered mig. Great bit of kit.
It can run on 36V DC but only for very heavy welds but can NOT run on 48V.
It is light, compact and does not need an inverter. Power direct from 2 standard 12V batteries in series, or from a 24V battery system , if you gave one.
US made.

Cheers,
Peter
OKA196 motorhome

 

[dreadlocks]

I'm not sure a lithium BMS would appriceate running a DC welder directly off the battery..

 

[Peter_n_Margaret]

That depends entirely on the BMS.
If it can run a 5,000/10,000W inverter it should have no problem with the welder.

Ready Welder » FAQs/ Manuals

readywelder.com

"A fully charged pair of these batteries will normally yield a minimum duration of about 45 minutes when welding 1/2″ steel or 3/4″ aluminum @ 175 amps, "
Cheers,
Peter
OKA196 motorhome

 

[dreadlocks]

those inverters only run at 48v to keep the amps down, and LFP dont really self regulate amperage output like a lead battery will, they can go into the danger zone and dump far more than is considered safe for them.. and as far as I can tell that welder has no current control, its just full power the battery will give.. so in the case of a decently large LFP bank would likely burn through everything you tried to weld, or just trigger a BMS shutdown after a whole second of welding.

 

[john61ct]

Sure y'all talking solar here?

Those big amp loads usually need a genset for input. . .

 

[1000arms]

... and as far as I can tell that welder has no current control, its just full power the battery will give...

Voltage input 18V (3x 6V golf-cart batteries in series) to 36V, welding wire diameter, and wire speed do give a lot of control with the Ready Welder. One can also use a tow chain as a dropping resistor depending on how much length one passes the current through. Hang the chain, clamp the input high, and clamp lower on the chain to create the resistance one wants.

That being mentioned, I'd be careful about welding with lithium batteries to avoid drawing too much current.

From the Ready Welder website:
"AMPERAGE RANGE: The Ready Welder welds very thin metals using a 12 and a 6 volt battery, (18 volts) or very thick metals with 36 volts DC, (three 12 volt batteries) yielding from 45amps, up to 350 amps."

Ready Welder

readywelder.com

 

[Peter_n_Margaret]

Sure y'all talking solar here?
Those big amp loads usually need a genset for input. . .

Batteries deliver amps without a problem (your single crank battery can deliver 600-1000A typically) and most of these big loads are for short durations so the energy is not so large and solar can easily replace it.
When the sun is shining, we heat our HWS with a 750W element and run a bread maker regularly and there are plenty of systems bigger than ours. The next step is an induction cook top.
Cheers,
Peter
OKA196 motorhome

 

[Madoxen]

sorry for my absence I have been a bit too busy with work :-(,

Thank you for your responses, on this, It would sound like the 48V system would be the way to go. which I think from the sounds of it will open more doors than it will close and will also let me run slightly smaller cables? as a plus the 48v multi is about $600 cheaper to buy. but i think i will burn that saving with the extra DC to DC 12 and 24v boxes.

The Batteries I have ordered or will have very shortly are 3.2v 280AH LiFeP04 times 32 of them although I might stop at 16, combined with 4x 550w mono solar panels working at 21.4% efficiency.
I like the idea of the small welder but I will not be purchasing another welder I already have 3 of the blooming things and do not want to add a 4th to my collection the one I would take with the truck is a Kemppi Mastertig MLS 2300A ACDC

 

[Madoxen]

ended up with 32x 3.2v 280 AH batteries which will either be 24v @ 1120 AH or 48v @ 560AH. not sure if my math is correct though.