AGM 12v or 6v?

[wackerb]

So 3 of the 4 140 ah Tudor took a total of 7 liters of water when I filled them. Now they get really hot charging, lots of bubbles and the charger never seems to shut off. I certainly wouldn't want to sleep in the bunk that is just over them. So I've decided to replace them I'm in Southern France, so not a big selection.

My question is if the preference for hooking two 6v batteries in series is still valid for AGM's. I have a choice between the following:
4 x Lucas Deep Cycle 12v, 180 Ah, 56kg for 546€ each
4 x Stormline Deep Cycle 6v, 330 Ah, 49kg for 559€ each

The Stormlines would require some cable changes and I don't have the equipment to make cables if I couldn't use the existing ones.

What would you do and why?

And a related question. Is battery box necessary for AGM's?

[ranger58sb]

Originally Posted by wackerb

My question is if the preference for hooking two 6v batteries in series is still valid for AGM's. I have a choice between the following:
4 x Lucas Deep Cycle 12v, 180 Ah, 56kg for 546€ each
4 x Stormline Deep Cycle 6v, 330 Ah, 49kg for 559€ each

And a related question. Is battery box necessary for AGM's?

What physical size are those?

If the Lucas batteries are equivalent to our Group 31, I'd have expected about 100 Ah each, about 400 Ah for the bank. If 8D equivalent, I'd have guessed about 245 Ah per battery... if 4D perhaps about 210 each...

If the Stormlines are equivalent to GC2 golf cart batteries, I'd have expected about 220 Ah per pair, about 440 Ah for the bank.

???

In any case, presuming this is a house bank, I'd be going for max Ah in the available space.

Our AGMs are not in a battery box, but they're also not within living quarters. They can off-gas a small amount from time to time, evidenced by eating away some clothing after sitting on them (inadvertently). It's not much, though.

FWIW, I'd prefer a battery box, but that's more for sitting on -- me, and sometimes things like tools when I'm working. But none of our model boats nor any by the same manufacturer (that I'm aware of) were delivered with battery boxes for the original flooded batteries, just trays and hold-downs. I presume that's an indication.

You might investigate various watering systems; flooded batteries with a watering system might be fine... especially if in a box under that bunk...

-Chris

[wackerb]

These are the largest AGM batteries available that will fit in the space under the bunk without stacking them. I agree on going for the highest Ah, but had heard the 6v work better over time. I also assume that comparing Ah's you have to correct for voltage, otherwise the 4 x 6v would be unreasonable higher.

[ranger58sb]

When you link 6V batteries together in series, voltage doubles to 12V and Ah remain the same. If you're starting with ~220 Ah 6V batteries, the bank of two at 12V would give you 220 Ah.


Wiring a pair of those pairs together in parallel would keep you at 12V and the Ah double, to 440 Ah if extending that same example.


Lots of on-line refs about wiring in series, in parallel, and in series/parallel; search is your friend.


Over here, just because a 12V battery says "deep cycle" on the label... apparently it's usually not. That's what often leads to a preference for 6V deep cycle batteries. Search battery threads here where MaineSail has contributed (among others).


I see Lucas AGMs identified on line, but can't tell which candidates you might mean that are 180 Ah. I see a 220 Ah battery for £450 here 200Ah Lucas AGM Deep Cycle 12v Battery | 12 Volt Batteries although I realize that's maybe not useful in southern France. A quick glance at dimension makes me guess maybe it'd be a 4D equivalent size, or similar...


-Chris

[StuM]

Originally Posted by wackerb

I also assume that comparing Ah's you have to correct for voltage, otherwise the 4 x 6v would be unreasonable higher.

Correct. The actual energy available from a battery should be measured in Watt hours when comparing different voltages.

4 x 12V x 180Ah = 8640 Wh
4 x 6V x 330Ah = 7920 Wh

[smac999]

I would choose 6v.

I use a lot of AGM L16's. (~400ah @6v)


I'm guessing the 12v are 4D's.

I'm not sure what the 330ah 6v's would be.

[wackerb]

smac999, would you mind explaining why 6v with a lower overall capacity?

[exMaggieDrum]

The weight of each battery is a big issue for me. When I replaced my last set of batteries I put in 6-6v AGM batteries. They are much easier to deal with although you have to put in the cables to put the batteries in series, which is actually not much extra work or expense.

The batteries you mentioned are 180Ah for the 12v batteries and 165Ah for the 6v batteries. So there isn't as much capacity in the smaller ones but it isn't a big difference.

I will be replacing my 8D size AGM batteries and I am dreading it because they weigh 156 pounds each (78kg). 56kg is much easier so it really is up to you. AGMs can be placed on their sides if needed by space considerations which may be a factor.

In any case, they should be absolutely secured so they cannot move even if the boat were to go upside down/capsize. Even in battery boxes they need to be strapped or bolted down.

[cwyckham]

It's all about convenience (layout and carrying) and final total Ah. No other real difference.

Edited to add: I think the reason people talk about 6V so much is that 6V Flooded golf cart batteries are an excellent price point, good deep cycle performance, and a convenient form factor, so a lot of people like to use them. There's nothing inherently important about the fact they're 6V, though.

[AvalancheAK]

Generally going with a series string works out better, but it's only for cabling. This isn't a lot of batteries, so whichever works better for your space. (I work in renewable energy and put in systems with 20-100 batteries sometimes. Then cabling considerations become important).

An AGM does not off gas in normal use, and it should not. They are sealed, once they lose moisture by gassing, they are losing capacity. If they are gassing you are charging them too high. Most installations I do with AGMs both on land and in boats do not have battery boxes or special ventilation. By contrast, wet cells in larger shore systems get a battery box and an exhaust fan to exhaust the hydrogen gas when charging.

[wackerb]

Thanks, all. I've ordered the Lucas. They're supposed to do 700 discharges to 50% so should last a good while if treated right. And I found the adjustment on my Cristec chargers for AGM so it should be and easy replacement with existing cabling.

[ranger58sb]

Originally Posted by wackerb

Thanks, all. I've ordered the Lucas. They're supposed to do 700 discharges to 50% so should last a good while if treated right. And I found the adjustment on my Cristec chargers for AGM so it should be and easy replacement with existing cabling.

Guessing it must be this one? Interesting form factor; looks to be slightly smaller than a 4D...

-Chris

LSLC180-12 12v 180Ah Lucas AGM Cyclic and Standby Battery

Manufacturer: Lucas
Brand : Lucas
Range: Lucas VRLA AGM Standby and Cyclic Battery
Voltage : 12v
Capacity : 180ah
Weight : 56kg
Dimensions : 494mm X 206mm X 209mm
Battery Type: AGM battery
Lucas LSLC180-12, 12v 180Ah Sealed Lead Acid / VALVE REGULATED LEAD ACID Battery

Dimensions : 494mm Long X 206mm Wide X 209mm High (Over Terminals).

Terminals : Screw down terminals

Battery Type: Standby and Cyclic battery

Can be used to replace: LSLC180-12

Design life : 3 - 5 Year design life when used in standby applications.

Commonly used in Alarm Systems, Emergency Lighting, Ride on Toys, Torches, UPS systems and other electrical systems