1 8D or 2 6v batteries?

[Mwilliamshs]

Custom build, starting from scratch. Which would you use, $ being no option, two 6v golf cart batteries or one 8D? The only big differences I can think of is wiring a single battery would be simpler (and cheaper) and tying one down would be simpler, fewer cells to check the levels in (assuming flooded), etc. One of the 2 smaller batteries would be easier to lift and move than the 1 big battery.

 

[JaSAn]

I went with 2 x GC2 FLAs. My reasoning:

1. Cheaper - I have less than $180 in my batteries (IIRC paid $86 each in 2015).
2. Easy to find - I bought mine at Sam's Club. 12V deep cycle batteries are harder to find.
3. True deep cycle batteries - a lot of the labeled 12v deep cycle are actually marine batteries (if they aint real heavy they aint deep cycle).
4. Easier to manhandle - at 62 lbs each for the GC2s a comparable 12V deep cycle would be ~120 lbs. At my age that's important.

Oh, and two 6V batteries and one 12V battery have 6 cells to check SG and add water to (2.1V per cell).
I also have one strap over the box the batteries are in, I'd do the same as for a single battery.

jim

 

[dwh]

2 6s.

 

[DaveInDenver]

Electrically it's the same number of cells, you're going to end up with 6 cells to get a 12V bank. By going with 1 x 12V battery the factory has provided a larger case and internal bus for all the cells for you. The downside to a single 12V is weight and size mostly. At noted, it's also easier to find high amp-hour 6V batteries (e.g. golf cart types that do 150 and 200 amp-hour) and so for a given capacity it's usually easier to configure a suitable bank using 2 x 6V. Bottom line is that there's no reason that 1 x 12V vs 2 x 6V will really matter performance-wise if you're able to match capacity and weight. So it's more about your convenience, physical constraints, etc. There may be a slight edge in reliability to the 1 x 12V because there's one less cable, but this is very marginal and truly splitting hairs. Personally I'd do 2 x 6V over an unwieldy big 8D sized single, but depends on your mount and ability to manhandle it.

 

[luthj]

With cash being no option, I would opt for an 8D 12v AGM battery (lifeline brand are superior). Better performing in most ways, easier to wire etc.

Pros
Higher charge efficiency
No offgasssing
Charges faster from alternator or high current source
Can be mounted on side if needed
No adding water
Better vibration resistance
higher cycle life (when charged and treated well)
more compact (less volume than flooded GC2)

Cons
Heavier than a single 6V (harder to move around)
More expensive
Cannot measure SOC with hydrometer (good SOC meter suggested)


GC2 batteries are a good option, I have used them in the past. They will need watering, and ideally a vented enclosure. They have a higher internal resistance so they will charge a bit slower, and have higher charging losses. They are much cheaper than AGM. They will tolerate outright abuse better than AGM in general.

The physical separation provided by AGM batteries glass mat makes them more resistant to shell shorting. This allows for more plates per cell. This means in generally they can accept higher charge currents, and supply higher discharge currents. This is why many AGM deep cycle batteries can double as starting batteries, as they have sufficient surface area to make good cranking amps.

If you have enough charging, space, and weight capacity, 4xGC2 in series/parallel will provide a 400AH bank. Obviously you need sufficient charging, otherwise sticking with ~220AH is best.

 

[Joe917]

2X6v flooded, Trojan or Crown, but they must be vented, easily accessed to maintain water levels and equalized regularly.
If they can't be mounted that way or you are poor at maintenance then go with 2X6v AGM such as Trojan.

 

[dwh]

This allows for more plates per cell. This means in generally they can accept higher charge currents, and supply higher discharge currents. This is why many AGM deep cycle batteries can double as starting batteries, as they have sufficient surface area to make good cranking amps.

You are confusing AGM, with TPPL AGM.

Only a few AGM batteries, such as the Odysseys, are built using the thin plate design. In Odyssey's case, they also use pure lead, hence, "Thin Plate, Pure Lead" (TPPL).

Most AGMs aren't built that way.

But they can still be used for cranking. Any deep cycle battery can. They just have a bit lower cranking amps rating than a cranking battery of the same size.