6 Volt Question

Newport41 · #1 (**permalink**) 03-20-2007

So, I've got six T-105's sitting on my boat slowly discharging. I want to get them all hooked up but I want to make sure there's nothing I'm missing, having never used 6 volt batteries before. I wanted to make three sets of two batteries linked in series to one post to creat one 675Ah 12volt bank. Do I have to treat this any differently than a a regular bank of 12volt batteries? Can I just hook up the charger and charge regulator from the alternator the same?
Another question that I feel I should be able to find on my own but am having trouble getting a straight answer, what size of cable should I link the batteries in series with? I've modified the box so that all the batteries fit right next to each other. I have numerous books telling me what size to use for longer runs but nothing telling me what to use for the 6 to 12 inch runs linking batteries in series.
Well I'm off to start stripping all the wood work of years of varnish abuse. And I mean ALL the woodwork. Prey for me

. Thanks in advance.

sailingdog · #2 (**permalink**) 03-20-2007

No you don't really have to treat them any differently than your old house bank—electrically, the three paralleled sets of two T105's in series is no different in real world usage as a three 12V batteries in parallel.

As to what size cable to use... as big as possible.

This is the last place you want to skimp on cable size. It also depends on the length of the run of the cable. I'd go with 1/0 AWG cable for the series connections between the batteries.

I'd go with either 2 AWG or 1/0 AWG cable for the parallel connection and back to the main DC panel, if the run is less than 4' and 7' respectively, based on the tables here. If the run from the main DC panel is longer than that, I would go with 4/0 AWG, which is good to about 15'.

This is basing the design on having no more that 150 Amps of charging current. It doesn't make much sense to go with more than 150 Amps, due to the limitations on charge acceptance by wet-cell batteries.

I hope this makes sense and helps.

PBzeer · #3 (**permalink**) 03-20-2007

2 6v in series = 1 12v, then as SD said, you parallel the 3 series wired batteries. Then run your positive lead off the first or last battery and the negative off the opposite of the postive, ie: first battery pos., last battery neg.. Assuming you are using a selector switch, you would run the postive lead to the #2 position stud, and the negative to your common ground. If you have a common postive stud that the both lead is connected to, you can then run a 8ga wire to your panel from the stud, and the negative from the common ground.

If you do have a selector switch, to which your current house bank goes to, then all you should need to do is run the appropriate size cables from the new bank to the switch, just as the current house bank is.

dougyoung · #4 (**permalink**) 03-20-2007

I am doing a similar project right now. All the info above looks good. I used 1/0 to connect all the T-105's in paralle and series as stated. I used 2/0 to connect the banks to the switch and DC panel. My runs are averageing between 4' and 8'. I decided to error on going larger.

Where I had questions is on charging, both with an AC shorepower charger and the alternator. I installed one of the new BlueSea battery switchs that isloates both banks from each other. I also installed a BlueSea ACR charging relay between both positive posts of each bank. The shorepower charger goes to the positive post of the house bank (T-105's). The altenator (85 amp) output wire also goes to the postive post of the house bank. The sensing wire from the alternator also goes to the same positive post,(You want the alternator to sense the voltage from your most often used battery bank). The ACR senses the charging current and connects both banks, at certain voltage levels it disconnects them to keep both banks seperate and from both banks discharging at the same time. This is a big advantage over a batterey isolator, (which I had before). The ACR has minimal voltage loss, (unlike the isolator) and both banks are now charging to their full capacity. Look in the most recent BoatWorks magazine. The alternator article explains it more in depth. So far I'm very happy and I didn't burn the boat down to the waterline.

sailingdog · #5 (**permalink**) 03-20-2007

I have the BlueSea ACR on my boat as well...and it is a good beastie to have... makes ending up with a dead house bank tougher..

Newport41 · #6 (**permalink**) 03-27-2007

Just trying to work with what I have here. Would 4 awg be too small for connecting between batteries (runs of 18" or less). I was then going to use2/0 to get to the pannel. Sound alright? The system is pretty light, never going to be more than 100amps going through it. I know it apperas to be alright on most tables but I've never connected batteries in series before.

GordMay · #7 (**permalink**) 03-27-2007

As has been indicated, bigger cable is better - but #4AWG is adequate for 625 Amps at 12 V for an 12" maximum jumper length (24" Cct length).
Goto Wire Size Charts (1 & 2):
http://www.cruisersforum.com/gallery...=500&userid=79
http://www.cruisersforum.com/gallery...=500&userid=79

sailaway21 · #8 (**permalink**) 03-28-2007

Newport,
Hit your search button for the archived threads on batteries. There's enough info in there to, well, kill a battery. Seriuosly though, the battery threads found here can be pretty well considered authoritative. There's a level of information available that would embarass most battery authorities.