4S Battery final touches: terminals, box and compression

[Pez]

I've finally got round to swapping the two 10+ year old gel batteries on our camper to a 4S LiFePO4 280ah DIY battery.

The final swap happened in the middle of a field but seems to have come out not bad considering.

While it's a bit hacked together, it's working fine, but I'd like to make some finishing touches.

Namely:

• Reading online, it seems best to slightly compress these cells rather than spacing them
• A box around the raw cells, to protect them, hide any exposed wires and reduce risk of shorts
• Battery terminals rather than direct connection to the cells for the 12v system

To that end and considering that I'm extremely space limited under the passenger seat:

• What are the options for compressing the cells? Would removing the spacing foam and wrapping the whole lot in Kapton tape be good enough?
• How have you protected your cells? Would some ply or something else be good enough? What about the top?
• Has anyone sourced or built their own battery terminals? (EU based if relevant)
• If I'm removing the battery foam, should I add another insulator? I see some people using cutting boards

Finally, any other tips or best practices that I should be following?

 

[Samsonite801]

Search here on the forum for battery clamp assembly or similar. There are quite a few threads on them. Also to be mindful of a heating solution for Winter time cold temps to keep the cells above freezing so you can charge in the cold.

Here is just one example of how I did mine. Note that mine are double-wide clamps (8-cells each dual 12v battery module), you can build a clamp much smaller (at half-width) that just holds a 4 cell stack...

Pictures - Battery bank clamp assembly

I finally got around to putting together my 12v and 48v battery banks (holder/clamp assemblies)... Just thought to post some pictures of it as a couple people had asked me before here. Still have to mount the BMS's, install the heat pads on bottom plate, thermostats, wiring, etc... But it's...

diysolarforum.com

 

[HRTKD]

The blue cables that are stacked on the cell terminal has a balance lead that looks like it might be below the lugs of the blue cables (between the lugs and the cell terminal). The picture is a bit fuzzy so I could be wrong.

The foam spacers aren't necessary. The flexible cutting board works as a good way to insulate electrically between each cell. It's not a thermal insulation layer.

In the summer I remove all insulation from around the battery to allow heat to dissipate.

 

[S Davis]

Is the battery held down? I would be really worried about the cells moving around and causing bad connections/heat/fire. Hit a good pot hole and a 50lb mass is going to move if not secured.

In the beginning for me I was unsure about compressing the cells but after reading a few fire threads I decided it was important to keep the terminals as stable as possible. I went diagonal with my connections and used flexible buss bar as well as compression and mounted on vibration dampers.

If you don’t have one I would get a fuse as close as possible to the battery.

 

[Pez]

Search here on the forum for battery clamp assembly or similar. There are quite a few threads on them. Also to be mindful of a heating solution for Winter time cold temps to keep the cells above freezing so you can charge in the cold.

Thanks for the links and the heating reminder, looking into it!

The blue cables that are stacked on the cell terminal has a balance lead that looks like it might be below the lugs of the blue cables (between the lugs and the cell terminal). The picture is a bit fuzzy so I could be wrong.

Will check that when I'm back in the van as I'm also not sure!

The foam spacers aren't necessary. The flexible cutting board works as a good way to insulate electrically between each cell. It's not a thermal insulation layer.

Sounds good, looks like I'll be making a trip to Ikea. I wonder if I could use the flexible board to make a box mounted directly to the cells with double sided tape given my very limited space, just to give a bit more protection.

Is the battery held down? I would be really worried about the cells moving around and causing bad connections/heat/fire. Hit a good pot hole and a 50lb mass is going to move if not secured.

It's wedged into the old metal battery holder (you can just see it in the second photo) and we didn't have a problem with the lead acid ones, but good point, I'll put a strap over the top.

In the beginning for me I was unsure about compressing the cells but after reading a few fire threads I decided it was important to keep the terminals as stable as possible. I went diagonal with my connections and used flexible buss bar as well as compression and mounted on vibration dampers.

If you don’t have one I would get a fuse as close as possible to the battery.

That battery looks great, thanks for the ideas. I like the idea of vibration dampers! There's a fuse now mounted ~10cm after the positive terminal outside the battery added after the photos when I swapped the red cable to significantly increase the surface area and added tape over any exposed metal.

Did you build those studs? Is it just M8 thread + nuts?

 

[Samsonite801]

That battery looks great, thanks for the ideas. I like the idea of vibration dampers!

Always put longer loops/bends into cables (connecting from vehicle to pack) and zip-tie them to prevent excessive movement (without fully restricting all movement)... Pretend you can see vibration and imagine how to keep it still but not too stiff and rigid in any one place.

Vibration is a weird creature, because there are lots of different frequencies of vibrations. Metal (cable materials) have a tensile strength, you can only bend the material back and forth so many times before they break. Stranded cable offers better tensile strength, but still has a tensile limit.

 

[Pez]

Does anyone have suggestions for battery terminals? (for a more professional + safe look)

 

[Zwy]

Finally, any other tips or best practices that I should be following?

One member here had a fire under a seat in a van setup similar to yours. The problem is the seat base isn't that high, your photo shows the seat base at the same height as the cells. In the case of the fire, the member had sat on the seat and thought there was clearance. The problem was when hitting a bump, the seat compressed enough to hit the battery terminals. It wasn't a short, but the cell terminals were damaged and later lead to catastrophic failure.

 

[boywonder]

Does anyone have suggestions for battery terminals? (for a more professional + safe look)

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