Are Trojans that much better?

[cpa]

I have used both Rolls and Trojan in the past. Neither ever worked that great for me. I had six 6v Deka batteries on my last boat for 5 years with no issue. My current boat has had Deka house and engine batteries for 2 years with no issue.

[redsky49]

Originally Posted by colemj

Maybe I didn't understand this part, but the only cables required in addition to those for a 12V battery system would be a single very short cable connecting each pair into series. These are typically <12" and not complicated to install.

There should be no significant voltage drop, loss of current or greater demands placed on them unless you are using lamp wire.

If you are concerned, use solid bar to connect - that's what we use because it is more convenient than short cabling.

The wiring used to connect to the loads should not be any different size between 6V and 12V cell systems because there is no difference between current drawn from 12V parallel cells and that drawn from 6V series/parallel cells (in practice, all of these systems are 2V series/parallel cell systems).

Mark

I don't think this is quite correct.

In my application I have used various battery approaches - 6V and 12V, gel cell and flooded. Currently using (4) Duracell/East Penn 6V in series/parallel configuration for house bank - 460ah.

For the series connection, the current flow will be less (roughly half) than the current flow of the paralleled batteries. In my case I am using 2/0 for the positive to negative series connection (cables with light blue coding). Since batteries may vary according to the placement of their terminals, I am using a rather longer cable for this purpose. The bespoke cables I created earlier for a particular battery configuration didn't fit the current set up and were obsolete (aaggghh...). Photo below shows the wiring. Hopefully the added length will allow any and all future requirements. Note that my batteries are all end-to-end. More frequently batteries are in a side-to-side configuration, and less challenging to wire.

From the paralleled batteries I am using even heavier cables, including some 4/0, and for the primary runs (including inverter) have the big mama 350 MCM cable. That's the black cable (on the bottom) in second pic that looks like a fire hose, with a 4/0 that is paralleling the batteries on top. One issue with heavier cable is that the lugs become thicker and the battery posts start to become too short - note battery post nut.

On none of the primary wiring are any conductors undersized and all go to a fuse that is rated for the smallest gauge wire.

I have very little line loss as a result!

I have 32 months experience with the Duracells and so far am satisfied. I paid about $105 each back in 2012. Target service life for me 72 months so I am almost halfway there. To date there is no noticeable capacity drop. Equalizing done every 4-6 months depending on if I have been drawing them way down and then having to recharge more heavily. Extensive recharging also impacts the watering schedule.

I originally would have gone with Trojans but would have had to order them, and at about a 50% cost premium over the Duracells. Duracell certainly seem to be a cost effective alternative to Trojans, and more importantly, a better deal, ah/$, than gel cell or AGM.

Just my opinion.

[colemj]

Originally Posted by redsky49

I don't think this is quite correct.

In my application I have used various battery approaches - 6V and 12V, gel cell and flooded. Currently using (4) Duracell/East Penn 6V in series/parallel configuration for house bank - 460ah.

For the series connection, the current flow will be less (roughly half) than the current flow of the paralleled batteries. In my case I am using 2/0 for the positive to negative series connection (cables with light blue coding). Since batteries may vary according to the placement of their terminals, I am using a rather longer cable for this purpose. The bespoke cables I created earlier for a particular battery configuration didn't fit the current set up and were obsolete (aaggghh...). Photo below shows the wiring. Hopefully the added length will allow any and all future requirements. Note that my batteries are all end-to-end. More frequently batteries are in a side-to-side configuration, and less challenging to wire.

From the paralleled batteries I am using even heavier cables, including some 4/0, and for the primary runs (including inverter) have the big mama 350 MCM cable. That's the black cable (on the bottom) in second pic that looks like a fire hose, with a 4/0 that is paralleling the batteries on top. One issue with heavier cable is that the lugs become thicker and the battery posts start to become too short - note battery post nut.

On none of the primary wiring are any conductors undersized and all go to a fuse that is rated for the smallest gauge wire.

I have very little line loss as a result!

Maybe I didn't express myself well, but what you wrote seems to be the same as what I was saying - not much more complication to 6V, no significant losses or demands in the series connectors, and the parallel connectors need to be sized correctly regardless of 6V or 12V cells being used.

Mark

[botanybay]

On my 24v bank I use 8 golf cart batteries (us battery 2200xc) in two strings of four batteries each.

Wiring is such that from the bus bar to each string is doubled 2/0 cable, intercell interconnects are doubled 2/0.

As overkill each string has its own bmv702 monitor checking amperage and midpoint voltage independently.

So far system has about 20 cycles to 50% and recharge. Voltage variation across the batteries is less than 0.1% (a couple of mv) battery to battery.

Late in absorption it might get as high as 0.5% variation from top to bottom half of each string.

Currently on 10 day cruise, have not fully charged all week and only seeing a 3% drift in calculated charge state between the two strings.

[GrowleyMonster]

I didn't mean to put down a 6v setup, because that is exactly what I use. Just pointing out that there is more wire and more connections, making wire and lug choices more important. I have 8 6v batteries in series for 48v and I am satisfied that I got the best deal for my money.

I use 2/0, by the way. I actually considered copper bar, but didn't want to take a chance on putting stress on the battery terminals due to motion or vibration. Obviously from purely an electrical standpoint, copper bar would be superb and simple, with no sweging or crimping needed, just drill holes and done.