another battery question

trouto · Senior Member

another battery question

Peter_n_Margaret · Guru

Yes you can, BUT....
The cables need to be appropriately sized - that means BIG. I suggest 35mm2.
For safety you should fuse the active cable at BOTH ends, near each battery. I suggest manually resettable circuit breakers of say 50A minimum (depending on what loads you intend to draw from the batteries).
Cheers,
Peter

Whenarewethere · Guru

It would be better to run the cable to positive on one battery & negative to the other. If you have a light load & charging I wouldn't worry too much. But at least put heavy gauge cables between the two batteries.

Peter_n_Margaret · Guru

Whenarewethere wrote:
It would be better to run the cable to positive on one battery & negative to the other.

That is very misleading unless you describe WHICH cables you are talking about as it could mean that you are suggesting that the batteries be wired in series which the OP does NOT want to do.

Cheers,

Peter

trouto · Senior Member

thanks Peter

didnt give a breaker a thought

better be safe then sorry

ill chuck one on

trouto · Senior Member

Whenarewethere

thanks Whenarewethere

so your saying + on the new battery to- on the older battery

and - on the new battery to + on the older battery

also while im picking brains

at the moment everything [ wiring] is running to the older battery

all the + wires to the + on the battery

and all the - wires to the - on the battery

should i once i put the new battery in

should i run the + wirering to the + on say the older battery

and the - wires to the - on the newer battery

that way they are both [ batterys ] are working the same ?????????????

i really hope that that makes some sence

Whenarewethere · Guru

It is not misleading because if the other cables are not there the battery is disconnected.

Anyway I have got 2 x 26 AH batteries connected as I suggested. Later I added a third 26 AH battery & added it simply connected to the first 2 batteries so I have a combination of both. I am only running a fridge & only have a 120 solar panel so I am not going to stress about the situation.

The only time is if I use the 3 batteries to run my compressors at 100 amps or backup jump starting. But for the short runs using 6AWG it is not worth stressing over.

As said earlier, since you are running new cable to the new battery the extra cost of overkill cable costs less than the time doing the job. Do that part right for the future. Put in heavy cable & colder all the connections. If your soldering iron is a bit under size, drill a hole in a block of wood to hold the connector, which in itself helps reduces heat loss. 120 watt soldering iron is boarder line for 6AWG wire.

T1 Terry · Guru

Don't ya just hate it when a post just goes off into the ether.
I'll try again, when connecting a 12v battery to another 12v battery so you still have a 12v system, big cables and positive to positive and negative to negative.
As far as the 2 cable, one going to the negative on one battery and the other going to the positive on the other battery, this is referring to the load/charging cables. The idea is to share the charging and load across the 2 batteries. It is still a compromise, but a lot better than connecting the load/charging to one battery and just piggy backing the second battery to it via long leads.

T1 Terry

Whenarewethere · Guru

My dog's breakfast but I am not stressing out over it as I am only running a fridge typically 2.5 to 3.1 amps, so about an amp per battery. Charging off solar or car 8 to 10 amps, so about 3 amps per battery, all 6AWG 3 metres (6 metres +&- )

Baz421 · Guru

Trouto

Please read this easy to understand.

http://www.smartgauge.co.uk/batt_con.html

Cheers Baz

trouto · Senior Member

Thanks Baz

and thanks to everyone that answered

tomorrows project

Hetho · Senior Member

This works. I wired it myself.

Regards.

Hetho

Baz421 · Guru

Hetho wrote:
This works. I wired it myself.
Regards.
Hetho

Curiosity here,,,, what current in/out is that wiring rated at????

Bobdown · Guru

If you wire 2 x 120 Ah batteries

+ to - on both batteries you will end up with 24 v at 120 Ah which is series.

If you wire the same batteries

+ to +
- to - you will end up with 12 v at 240 Ah which is parallel

which is the preferred way for caravans.

Cheers Bob

Aus-Kiwi · Guru

Yep cable is a little light between batteries . But Id load is taken evenly off both ? Its not an issue . Besides total amperage possibly is that high its storage over time ( A/H ) your really after .

T1 Terry · Guru

Aus-Kiwi wrote:
Yep cable is a little light between batteries . But Id load is taken evenly off both ? Its not an issue . Besides total amperage possibly is that high its storage over time ( A/H ) your really after .

Not the way it is wired in Hetho's photos, one battery is doing the work and the other battery is just piggy backing off it. Just because the voltage is the same doesn't mean the load is the same on both batteries nor will the state of charge be the same. The high internal resistance in a lead acid battery is the reason why such a set up will not load share. I think the Smartgauge article Baz421 liked to explains what will happen and the better way to wire it.

T1 Terry

Sorry, auto correct messed with Aus Kiwi's post I quoted so I changed it back

-- Edited by T1 Terry on Sunday 27th of January 2019 06:27:21 PM

Baz421 · Guru

T1 Terry wrote:
Aus-Kiwi wrote:
Yep cable is a little light between batteries . But Id load is taken evenly off both ? Its not an issue . Besides total amperage possibly is that high its storage over time ( A/H ) your really after .
Not the way it is wired in Hetho's photos, one battery is doing the work and the other battery is just piggy backing off it. Just because the voltage is the same doesn't mean the load is the same on both batteries nor will the state of charge be the same. The high internal resistance in a lead acid battery is the reason why such a set up will not load share. I think the Smartgauge article Baz421 liked to explains what will happen and the better way to wire it.

T1 Terry
Sorry, auto correct messed with Aus Kiwi's post I quoted so I changed it back

-- Edited by T1 Terry on Sunday 27th of January 2019 06:27:21 PM

Agree Terry. I learned this lesson in the 80's on my yacht,,, kept killing one battery in bank of 3 ,,, 2 year warranty in those days,,, dealer told me to f*** off in the end.

Also I don't like 2 wires joined to take current,,, experience in real life too,,,,, only takes a low resistance in one wire to overload wire,,, ie create hotspot,,, there fore a risk IMHO

Aus-Kiwi · Guru

Ahh . If load is taken off the centre no issue . What I meant buy fitting cables so pulls off each battery, load balancing . Works the same when charging . One pic the cable was smaller . Of course it depends on total load ? But most are low amperage over time as in TVs, lights etc . With enough solar, good regulator ? Shouldnt have issues . Often wander when motor batteries are connected via VSR it effects balance ? Between the two types of batteries .