4@12v = 24v

EsoxLucius wrote:
Is there room for two more?

Yup.

Is there room for two more?

Nice batteries!

mena661 wrote:
Sweet! Which AGMs did you get?

Got these. They got here in 2 days because I'm close to the warehouse in Los Angeles.

BFL13 wrote:
so it would not be crazy to get those other two now so they are all the same age.

Yah.. they're just so darned expensive! I just want to make sure I can fully charge them every day.

Was mention of getting two more and going back to six. ISTR OP went down to four so they would all have chance to get to a high SOC in the one day, where the six would not

But you do need a big bank to get you through a few overcast days or else it is generator time (which some people regard as a major set-back in their lives :) )

In this case six 80s is only 480AH, so it would not be crazy to get those other two now so they are all the same age.

Sweet! Which AGMs did you get?

My 4-12v 80ah AGMs are in and working nicely. Admittedly I could use more ah, but, these seem to be working just fine.

After a night of 5 hours of TV, I can easily brew coffee next am @ 1200w for 10 minutes without going below 24v. At 8am there's only minimal help from the sun.

Edit: Oh, and I was noticing the voltage was fluctuating by .1 volts, and when using the inverter the voltage was all over the place. Turns out I broke the 250a inline cat fuse, so I replaced it.

pianotuna wrote:
If I were in 2oldman's shoes I'd sure look at AGM 12 volt in series parallel with disconnect switches between the twin banks. Normal operating would be all four wired in a balanced manner. Switching would allow him to condition one set of batteries while using the other

..which on the surface sounds like I'd be doing a lot of making sure both banks were equally charged. I'm trying to cut DOWN on the maintenance. :)

Salvo wrote:
I kind of think a shorted cell in a parallel application would be blown open. But I think most shorts are soft shorts.

I like redundancy. There's no redundancy in a single string.

If you're concerned about imbalance then parallel is the way to go. You got a shot at equalization when in parallel, not in series.

Sal

I've seen many instances (three of them that I was able to verify personally) where a cell will short and drag the rest of the bank down. Usually it manifests itself as a bank that loses a lot of capacity overnight, and you'll find one battery (I usually work with 6v batteries) that reads 4.x volts and is warm to the touch. The electrolyte in the one cell will usually be low, too, from the extra heat.

Redundancy is good. Most banks of any size (esp. ones using 6v batteries) use series-parallel connections, so you will have some redundancy. Rolls and other battery manufacturers recommend against excessive parallel connections in their user manuals ("Multiple parallel connections create unequal string resistances, resulting in possible cell damage or failure.").

Equalizing is intended for series-wired batteries (including the series-wired cells within the batteries). Parallel-wired batteries tend to self-equalize.

I kind of think a shorted cell in a parallel application would be blown open. But I think most shorts are soft shorts.

I like redundancy. There's no redundancy in a single string.

If you're concerned about imbalance then parallel is the way to go. You got a shot at equalization when in parallel, not in series.

Sal

lorelec wrote:


There are advantages and disadvantages to both. A battery that has a shorted cell (fairly common failure mechanism in older batteries) will become a sink and can drag down an entire bank of parallel-wired batteries. A shorted cell in a series string will simply reduce bank voltage by ~2 volts.

Personally I would choose series over parallel. Assuming you start will all new batteries of the same capacity, and you maintain them properly, there is probably less of a chance of an imbalance developing in the first place.