Batteries in parallel .

[loanrangie]

I'm replacing the single 150ah battery in my van with 2 x 100ah, i will need linking cables but not sure what size SQmm i need ?

[drivesafe]

Hi Loanrangie, it all depends on location of the two batteries and what is likely to be the heaviest charge and discharge current loads.

Discharge current loads are usually the highest current loads encounter, so look at what you are likely to be using.

For instance, 12v to 240vac inverters are probably the highest loads you will need to cater for.

Next is the location of the two batteries. Are they going to be side by side, one battery on one side of your van and the other on the opposite side of your van.

If you can use something like 6B&S ( 13.5mm2 ) for both the Positive ( + ) and the Negative ( - ) cables, as 6B&S can safely handle a continuous current load of just over 100 amps, you should pretty well cover any event you are likely to come across.


Where high current handling cable is concerned, bigger is always better.

[loanrangie]

Hi Loanrangie, it all depends on location of the two batteries and what is likely to be the heaviest charge and discharge current loads.

Discharge current loads are usually the highest current loads encounter, so look at what you are likely to be using.

For instance, 12v to 240vac inverters are probably the highest loads you will need to cater for.

Next is the location of the two batteries. Are they going to be side by side, one battery on one side of your van and the other on the opposite side of your van.

If you can use something like 6B&S ( 13.5mm2 ) for both the Positive ( + ) and the Negative ( - ) cables, as 6B&S can safely handle a continuous current load of just over 100 amps, you should pretty well cover any event you are likely to come across.


Where high current handling cable is concerned, bigger is always better.Thanks Tim, batteries are side by side and I just bought a 2000w inverter so that will be the highest load.

Also, do you know what these fitting are called? They fit into the junction box on the house type solar panels I have on the van but can't find where to buy them from.
I thought they were the same as MC4 connector pins but they are slightly smaller.https://uploads.tapatalk-cdn.com/20230416/38b7149fb232cbcd1fabb9828f02523c.jpg

[Graeme]

Best to have an air gap between the batteries.

[drivesafe]

Hi again LoanRangie, those type of terminals are call Bootlace crimp terminals and they come in a variety of size and shapes.

There are very common and you should be able to get them in places like JayCar.

[loanrangie]

Hi again LoanRangie, those type of terminals are call Bootlace crimp terminals and they come in a variety of size and shapes.

There are very common and you should be able to get them in places like JayCar.I looked at bootlace crimps but these have little springs on them and are a snug fit, will try jaycar tomorrow and see what they have.

[drivesafe]

Sorry LoanRangie, I did not realise it had the fluting on the terminal.

They are called BANANA PLUGS and again, you should be able to get them at JayCar.

[p38arover]

Yep, banana plugs, e.g.,

Black Banana 4mm Plug | Jaycar Electronics (https://www.jaycar.com.au/black-banana-4mm-plug/p/PP0402?pos=3&queryId=8ec3b4689b6bc426344967e05d13255a&sort=relevance&searchText=Banana%20plug)

[loanrangie]

Yep, banana plugs, e.g.,

Black Banana 4mm Plug | Jaycar Electronics (https://www.jaycar.com.au/black-banana-4mm-plug/p/PP0402?pos=3&queryId=8ec3b4689b6bc426344967e05d13255a&sort=relevance&searchText=Banana%20plug)

Very similar but without the flat shoulder where the screw clamps it into the fitting like the ones i have.

[p38arover]

You can buy solder types and screw types. I think i linked the solder type.

[loanrangie]

You can buy solder types and screw types. I think i linked the solder type.

The top part fits but no shoulder to hold them in place, nothing else in the store that would fit.
I didn't think it would be this hard to find them since its a pretty common panel fitting.
https://uploads.tapatalk-cdn.com/20230417/9f7e8242ac79739e51db2aef1c3d8008.jpg

[BradC]

I searched high and low looking for crimp terminated banana plugs that could hold a large gauge cable. Best I came up with was these : Red Insulated Type Banana Plug - Altronics (https://www.altronics.com.au/p/p9286-red-insulated-type-banana-plug/)

If you throw the plastics away the connector itself looks much like the one in your picture. The only problem is the brass is pretty brittle, so crimping on anything less that about 8awg (which is a snug fit in the female end) can be dicey. If you soldered the wire in then it'd be pretty close to what your picture shows.

[loanrangie]

I searched high and low looking for crimp terminated banana plugs that could hold a large gauge cable. Best I came up with was these : Red Insulated Type Banana Plug - Altronics (https://www.altronics.com.au/p/p9286-red-insulated-type-banana-plug/)

If you throw the plastics away the connector itself looks much like the one in your picture. The only problem is the brass is pretty brittle, so crimping on anything less that about 8awg (which is a snug fit in the female end) can be dicey. If you soldered the wire in then it'd be pretty close to what your picture shows.


I had a look at similar ones in jaycar but they didnt look suitable without me buying one and opening it up, the tips are fine just the rest is not quite up to it.

[johnp38]

Why not convert to mc4?

[loanrangie]

Why not convert to mc4?


Because MC4 doesn't fit in the junction box or the fitting the cable goes into as per the pic above, and if you look at a house panel it will have the same fitting.

[BradC]

I had a look at similar ones in jaycar but they didnt look suitable without me buying one and opening it up, the tips are fine just the rest is not quite up to it.

I've made several sets of cables from the guts of the one I linked. 2 soldered (6mm2) and one crimped (8mm2).

[johnp38]

Because MC4 doesn't fit in the junction box or the fitting the cable goes into as per the pic above, and if you look at a house panel it will have the same fitting.

Sorry I wasn't clear, I mean add mc4 pigtails, so make it same as house panel with cable out of the diode box with mc4 on end.

[loanrangie]

Sorry I wasn't clear, I mean add mc4 pigtails, so make it same as house panel with cable out of the diode box with mc4 on end.

They don't fit, tried that first and the fittings i need are house panel diode box connectors as per my pic.

[DiscoDB]

They don't fit, tried that first and the fittings i need are house panel diode box connectors as per my pic.

I think johnp38 meant make up a set of pigtails using the old cable and fit MC4 connectors at the other end.

Or you could find a junction box that is the same with the MC4 pigtails and disassemble and use the pigtails.

Junction Box Solar Pv Rigid Carbon Fiber Photovoltaic 180w-300w Solar | Google Shopping (https://www.google.com/shopping/product/1?q=solar+diode+junction+box&rlz=1CDGOYI_enAU800AU800&hl=en-GB&biw=375&bih=631&tbs=vw:l&prmd=isvn&prds=num:1,of:1,eto:9073368110286723165_0,prmr:1,p id:9073368110286723165,cs:1)

Does the junction box have a part number?

[loanrangie]

I think johnp38 meant make up a set of pigtails using the old cable and fit MC4 connectors at the other end.

Or you could find a junction box that is the same with the MC4 pigtails and disassemble and use the pigtails.

Junction Box Solar Pv Rigid Carbon Fiber Photovoltaic 180w-300w Solar | Google Shopping (https://www.google.com/shopping/product/1?q=solar+diode+junction+box&rlz=1CDGOYI_enAU800AU800&hl=en-GB&biw=375&bih=631&tbs=vw:l&prmd=isvn&prds=num:1,of:1,eto:9073368110286723165_0,prmr:1,p id:9073368110286723165,cs:1)

Does the junction box have a part number?

The panels came with cut lengths that i used with screw terminals to join into the rest of the cabling but i want to delete join to make it neater and more moisture resistant, wires are in conduit so not a big problem.
Seems pointless using the MC4 connectors if they aren't going to be removed .

[DiscoDB]

I would imagine the solar panels had a proprietary fitting prior to MC4 being adopted as the standard in 2008.

Possibly an obsolete MC3 plug end could be made to fit (the male end is 3mm diameter instead of 4mm used in MC4). You would just use the metal core, and retain your original screw cap.

Otherwise just splice your old and new cables with solder and use heat shrink.

[loanrangie]

I would imagine the solar panels had a proprietary fitting prior to MC4 being adopted as the standard in 2008.

Possibly an obsolete MC3 plug end could be made to fit (the male end is 3mm diameter instead of 4mm used in MC4). You would just use the metal core, and retain your original screw cap.

Otherwise just splice your old and new cables with solder and use heat shrink.I have spliced them for now, they did have MC4 plugs on a couple of the cables but I didn't want them.

[loanrangie]

A mate made me a pair of 16sqmm linking cables so i got the 2 x100ah batteries mounted in the van, went away for 4 days and the solar worked well keeping the batteries full up to 14.5V in full sun then down to 12.7V at night after using lights,range hood and a 240V radio via a 2000w inverter .Also used a toaster on the inverter and that dropped the batteries below 12V but they went back up to 12.7V once the load stopped.

[loanrangie]

Looking at electric low watt kettles and i came across this little singer .9L 1100w on amazon, gave it a test run and it used less power than the toaster we used while away.
While heating the batteries dipped to 12.1V but went straight back to 12.7V once boiled.
https://uploads.tapatalk-cdn.com/20230427/596a77ddf43dfb6ad2f86c66031f346a.jpghttps://uploads.tapatalk-cdn.com/20230427/015dd3bede03017d070e3e698cd5ae18.jpg