Doubled Battery capacity/storage

[Uncle G]

This last weekend I picked up my new 2022 geo pro 15tb, I decided to run/test all the 12v equipment and soon realized I needed more battery storage/capacity. It came with one 12v interstate battery rated at 63 amp hours. I bought an identical Noco group 24 snap top battery box which was on amazon for $22-$24. I found the same box at walmart for $8. Purchased an additional HD24-DP Interstate 12v battery for $103.
Broke out the dremel and had to make some modifications to the battery boxes top covers so the would fit end to end and to make room for the positive and negative cables from the trailer. Nothing blew up and everything still works.

[Uncle G]

No idea why all my photos uploaded sideways. I also drilled some mounting holes for both battery boxes and used bolts with lock washers and nuts to secure them to the frame/hitch. Probably going to add ratchet straps to hold down the top covers because the cloth straps that come with the battery boxes are not confidence inspiring.

[NavyLCDR]

You might also want to drill a couple of drain holes in the bottom of the battery boxes. Even without the added cutouts in the boxes, I have found an inch of water in the bottom of mine for putting in a couple of small drain holes.

[eric1514]

Hard to tell, but it looks like your positive and negative take offs are on the same battery. You don’t want to do that. Take neg from one battery and pos from the other

[mikeyk101]

Originally Posted by eric1514

Hard to tell, but it looks like your positive and negative take offs are on the same battery. You don’t want to do that. Take neg from one battery and pos from the other

You have to be careful about doing that. If you do what you are suggesting, the volts will jump from 12v to 24v. Now if you are using 6v golf cart batteries, that would be the preferred way to get 12v using both batteries.

https://www.batterystuff.com/kb/arti...-tutorial.html

[NavyLCDR]

Originally Posted by mikeyk101

You have to be careful about doing that. If you do what you are suggesting, the volts will jump from 12v to 24v. Now if you are using 6v golf cart batteries, that would be the preferred way to get 12v using both batteries.

https://www.batterystuff.com/kb/arti...-tutorial.html

What eric1514 is saying is the proper way to connect 2 12 volt batteries in parallel. You want two jumper connection between the two batteries - positive to positive and negative to negative. Then you want the positive going to the trailer/RV to be connected to the positive terminal of one battery and you want the negative connection to the trailer (usually to the frame) to be connect to the negative terminal of the OTHER battery.

This equalizes the load and charging between the two batteries. If you connect both RV/trailer leads to the same battery, then the battery the RV/trailer leads are connected to will be charged and discharged more heavily than the battery that only has the jumper cables connected to it.

This is the correct way to wire 2 12volt batteries in parallel:



This is the wrong way to wire 2 12volt batteries in parallel:

[eric1514]

Originally Posted by NavyLCDR

What eric1514 is saying is the proper way to connect 2 12 volt batteries in parallel. You want two jumper connection between the two batteries - positive to positive and negative to negative. Then you want the positive going to the trailer/RV to be connected to the positive terminal of one battery and you want the negative connection to the trailer (usually to the frame) to be connect to the negative terminal of the OTHER battery.

This equalizes the load and charging between the two batteries. If you connect both RV/trailer leads to the same battery, then the battery the RV/trailer leads are connected to will be charged and discharged more heavily than the battery that only has the jumper cables connected to it.

This is the correct way to wire 2 12volt batteries in parallel:

Attachment 262679

This is the wrong way to wire 2 12volt batteries in parallel:

Attachment 262682

Exactly. Thanks.

[jcrevs]

Originally Posted by NavyLCDR

This is the wrong way to wire 2 12volt batteries in parallel:

Attachment 262682

but the correct way to add a battery to the kids powerwheels

[mikeyk101]

Ah, ok. Now I understand. Thank you.

[War Eagle]

Originally Posted by NavyLCDR

What eric1514 is saying is the proper way to connect 2 12 volt batteries in parallel. You want two jumper connection between the two batteries - positive to positive and negative to negative. Then you want the positive going to the trailer/RV to be connected to the positive terminal of one battery and you want the negative connection to the trailer (usually to the frame) to be connect to the negative terminal of the OTHER battery.



This equalizes the load and charging between the two batteries. If you connect both RV/trailer leads to the same battery, then the battery the RV/trailer leads are connected to will be charged and discharged more heavily than the battery that only has the jumper cables connected to it.



This is the correct way to wire 2 12volt batteries in parallel:



Attachment 262679



This is the wrong way to wire 2 12volt batteries in parallel:



Attachment 262682

Are those not wired exactly the same just drawn differently?

[mikeyk101]

Originally Posted by War Eagle

Are those not wired exactly the same just drawn differently?

No. On both, the positive is wired to positive and negative to negative. The difference is how the connection to whatever the batteries are connected to. In the first one, the main positive wire is connected to one battery and the negative is connected to the second battery. Thus allows both batteries to be equalized the same. But in the second graphic, the main positive and negative connections are to the same battery. That means that instead of providing equal charge and discharge to both, the second battery is basically parisiting off the first main battery.

Just to add, I am not an expert so I may not be completely accurately describing what is occurring but hopefully you understand what I am trying to say...

[TitanMike]

Originally Posted by NavyLCDR

What eric1514 is saying is the proper way to connect 2 12 volt batteries in parallel. You want two jumper connection between the two batteries - positive to positive and negative to negative. Then you want the positive going to the trailer/RV to be connected to the positive terminal of one battery and you want the negative connection to the trailer (usually to the frame) to be connect to the negative terminal of the OTHER battery.



This equalizes the load and charging between the two batteries. If you connect both RV/trailer leads to the same battery, then the battery the RV/trailer leads are connected to will be charged and discharged more heavily than the battery that only has the jumper cables connected to it.



This is the correct way to wire 2 12volt batteries in parallel:



Attachment 262679



This is the wrong way to wire 2 12volt batteries in parallel:



Attachment 262682

This becomes more of an issue when battery banks are subjected to huge loads and connecting wires are marginal.

If batteries are connected with low resistance conductors any imbalance in discharge current among batteries is insignificant. A bigger issue in huge off grid solar installations.

A bigger consideration is to use battery connecting conductors large enough to carry MORE than the maxjmum current draw with minimal voltage drop. Short length of jumpers will reduce voltage drop as well.

[Uncle G]

I appreciate all of your positive feedback.

[corn18]

I used 4/0 wire to parallel my 2x206Ah LiFePO4 batteries and hooked it up the recommended way. After working with 4/0 wire for a day, I am convinced it has negative resistance. It is so darn thick and the end connectors are about the size of a smart car.