SiO2 batteries - opinions?

That's the wiring plan I was planning, with all wires equal length to buss, they're all 0000 gauge, so I think I'm ok there.

Yes, I should have been more clear.

In method 3, for three batts, the three pos links need to be equal and the three neg links need to be equal, but the pos links don't need to be the same as the neg links.

However, the three links for each do need to be able to carry the total current without adding a lot of resistance. The danger point for that is the junction where the three links have their lugs stacked. Better to use a buss with three ins and one out I suppose, to avoid stacking.

So loads and chargers to a buss with little or no stacking, then a single fat wire from buss to the junction buss with the three equal links from that to the batteries.

BFL13 wrote:
It doesn't matter if the pos and neg sides are unequal because it is a circuit.

Not true - assuming we're talking about the same thing.

Voltage drop through the wiring to/from EACH battery has to be the same during either charging or discharging of each battery in order for each battery to be treated identically, electrically, in any 12V multiple-battery paralled setup called "balanced".

Note "Method 3" in this link - that is the method to be used for three(3) 12V batteries if one wants to hook them up in parallel in a balanced way - so as to ensure absolute maximum life of the three(3) batteries: http://www.smartgauge.co.uk/batt_con.html

The link above is all about equal circuit voltage drops for each battery due to the current passing through the wiring resistance to/from each terminal of each battery. The entire contents of the link should be carefully read and understood before taking on the additional time, effort, and money to hook up 12V RV batteries in a completely balanced way.

Of course the approach shown in the link has to also be used when wiring up multiple two-battery 6V sets (to make 12 volts per set) into balanced 12V battery banks.

pnichols wrote:

phemens wrote:
Confusingly, the battery is called a 240 but actually provides 210 ah. I will be wiring each battery to a junction post as recommended in that link, thanks!

Note the most important thing is: Each battery must be wired to the junction post using the SAME LENGTH of wire. :)

The Trimetric shunt makes it impossible to have the pos and neg sides equal, but that is not the requirement. As noted, the battery to shunt (neg side) links need to be equal, and the pos links need to be equal to their junction.

It doesn't matter if the pos and neg sides are unequal because it is a circuit.

Also the shunt might not take all three links due to its short bolt, so you might need to run a fat wire from shunt to neg junction and then have the three neg links.

Note that the outer end of the shunt also has a short bolt so you could need a neg buss on that side to take all the load/charging wires. For ampacity gauge of the wires, the single fat wire from the shunt has to take the total amps of all the individual input wires to the shunt. Then in turn, the three links have to take that total amongst themselves, but you can't be sure each will take exactly 1/3, so over-do their gauges a bit, but still make them the same as much as possible.

Same with the pos side except no shunt, but instead now you have fuses. No fuses on the three pos links to junction, but then you will have individual size fuses per each input pos wire gauge. You could have bolt length issues there too for stacking lug terminals, which means another buss and wire (fused) from buss to junction.

Should be fun to organize all that! :)

phemens wrote:
Confusingly, the battery is called a 240 but actually provides 210 ah. I will be wiring each battery to a junction post as recommended in that link, thanks!

Note the most important thing is: Each battery most be wired to the junction post using the SAME LENGTH of wire. :)

Also you need a second 2000w gen and a second PowerMax adjustable to recharge all those AH in a reasonable time. :)

Confusingly, the battery is called a 240 but actually provides 210 ah. I will be wiring each battery to a junction post as recommended in that link, thanks!
I also have a victron battery meter with Bluetooth to monitor all this, I think I'll spend way too much time checking that than I will need to.

Balancing three batteries is an issue for sure. The middle one is neglected when you pretend it is like two. There is a way to do it right linking each batt to a common buss for pos and neg. The guy here says it is only worth doing it right if the batts are expensive and if they are low internal resistance.

http://smartgauge.co.uk/batt_con.html

I am jealous of your new battery bank. Very nice! :)

Typo--210 not 240.

I pulled the trigger on 3 x Rolls 12FS-240 batteries, giving me a total of 630 ah (315 usable) at a total of roughly 400 lbs, this was by far the most cost effective solution ($$2.50/usable ah vs double that for AGM). I've got plenty of real estate in the basement. I don't think I have enough separate use of inverter to justify a parallel set-up, I think that would complicate things unneccessarily.
For wiring of the batteries, I'll be re-using the 0000 wiring I had (between batteries, distribution posts and inverter), but I'm wondering if I'm better to wire the batteries in parallel (balanced) or just wire each individually to the distribution posts. Any advantage either way?

I still don't have a price for T-1275s but I do note that while 600AH for four T-1275s weighs 328lbs, 600AH of my 100AH 27 size AGMs at 64lbs each weighs 384lbs for six of them.

Another thing to consider is footprint real estate. Six 27s vs four T-1275s. The T-1275s must be outside and are tall too, But (some of) the AGMs could go inside, so that is an advantage for finding room for them all.

Then you have the problem of making up a bank with six 27s that is "balanced". Needs lots of fat wire. Now you might look at my method of having the big inverter on its own bank, and having the rest of the 12v rig on its own bank. Makes wiring each bank (two and four?) balanced easier.

But now you need two converters and two solar sets (which I have from left-over equipment from previous rigs)

I can see looking at the new options when it comes time to replace the old battery bank. Been doing that myself. However, if what you have works, the temptation must be to just replace it as is if everything gets too complicated.