Safely Handling A123 Battery Packs

[TheHappyNomads]

I'm moving slowly here to take any/all safety precautions with my battery bank build so please be patient and excuse any juvenile questions. I've posted here before about working on these A123 packs but this is slightly different topic and wanted to open a different thread.

I have two questions re: handling of these packs:

(1) What precautions should I take in moving/handling these units particularly with the connectors hanging off of each end. When they were first delivered I could have sworn that I felt a little buzz on my bare arms when I picked them up to relocate them to my garage from the driveway. I can only imagine it was from my skin touching the terminals on both sides simultaneously. I would like to avoid any unnecessary shock or surprises when moving these around. What precautions am I overlooking when it comes to handling?

(2) Some of the packs are labeled POS like the one in the pictures. I have a few others that are labeled NEG. When it comes to connecting these together to build 18s 48v packs what is the most efficient way to do so? Do those stickers mean the entire module is positive or just the side the pack that is labeled?

Thanks!

 

[Korishan]

What precautions should I take in moving/handling these units particularly with the connectors hanging off of each end.

Take some masking tape, preferably painters tape, to cover the contacts. This type of tape is very easy to remove and doesn't leave behind a residue.
You can use electrical tape, but it will eventually leave residue behind, especially if it gets pretty warm, such as if the unit is sitting in direct sunlight for a few hours

When they were first delivered I could have sworn that I felt a little buzz on my bare arms when I picked them up

Yup, you most likely did get zapped slightly. With just a slight tad bit of sweaty palms, you can make sufficient electrical conductivity for even 12VDC to make a connection path. I've gotten "bitten" when replacing car batteries while working at the autoparts store a few times. Sweaty palms/shirt and leaned on the frame, belly made solid contact with the frame of the vehicle, and then I had metal tools touching the positive of the battery. Zing! Made me back off and reposition myself.

The higher the voltage, the stronger the bite.

I would like to avoid any unnecessary shock or surprises when moving these around.

I had put together a 48VDC battery replacement for my rackmounted UPS. I picked up the battery with bare hands, altho dry, I still got a bit of a nip as the ends I was picking up where the bus bar ends. The corners dug deep enough into my skin that it still made contact. I didn't have painters tape on hand, so I used some Kapton tape and wrapped the ends so I didn't get bit again.

Do those stickers mean the entire module is positive or just the side the pack that is labeled?

Just the end of the module the sticker is on. You can't have a battery pack that doesn't have both Pos and Neg exposed. Otherwise you couldn't get power from it.
The labeling is there probably because when they are installed in their proper housing for usage, those are the ends that are visible to the mechanic/electical-engineer to work on and to remind them which end is which. You don't want to connect the opposing end to a battery that is capable of delivering 1000's of amps in sudden discharge mode. Best case is they have to change their pants. Worse case is they have to replace the worker.

 

[TheHappyNomads]

Wow thanks Korishan!

One last question: are those contacts there for connecting the batteries together? It seems to make the most sense. If so, then when connecting them together what is the best/most conductive material for nut and bolt in this setting?

 

[Korishan]

You probably could connect them together that way. In their designed application, it's possible that they were bolted to a large contactor of some sort so that each one could be energized separately. This is just purely speculative.

The bolts used to make connections are really the biggest thing to worry about other than you want something similar to what's already used, or stainless. Reason being you don't want electrolysis between different metals. Most cases, you'd go with stainless steel or nickel coated bolts. Don't use galvanized or generally any other metal. You could use brass, but they'd be expensive and would still corrode over time. I'd recommend stainless, tbh

It looks like some of the tabs are already threaded. So you'd want to match up the threads if you want to use those. Otherwise drill them out and use a bolt all the way through. I'd also recommend using lock washers to make sure the bolts don't want to back out (or the nuts if drilling out)

Then the connector that makes the physical connection is the most important part here. On the copper contacts you can use copper or nickel/tinned coated lugs. Tinned coated lugs are pretty inexpensive. If you want to use copper lugs, you can make these from old copper water tubing if you have some "junk" pieces laying around. Save you some money. Otherwise you can buy those too.
You'd want to use crimps ideally on the wires to connect the lugs. Don't solder them if don't have to. You want a solid connection and solder may not do a good enough job alone. Crimping is pretty much the best way at this scale, as you'd be using pretty beefy wire gauge. I'm guessing at least 4 awg

 

[TheHappyNomads]

You probably could connect them together that way. In their designed application, it's possible that they were bolted to a large contactor of some sort so that each one could be energized separately. This is just purely speculative.

The bolts used to make connections are really the biggest thing to worry about other than you want something similar to what's already used, or stainless. Reason being you don't want electrolysis between different metals. Most cases, you'd go with stainless steel or nickel coated bolts. Don't use galvanized or generally any other metal. You could use brass, but they'd be expensive and would still corrode over time. I'd recommend stainless, tbh

It looks like some of the tabs are already threaded. So you'd want to match up the threads if you want to use those. Otherwise drill them out and use a bolt all the way through. I'd also recommend using lock washers to make sure the bolts don't want to back out (or the nuts if drilling out)

Then the connector that makes the physical connection is the most important part here. On the copper contacts you can use copper or nickel/tinned coated lugs. Tinned coated lugs are pretty inexpensive. If you want to use copper lugs, you can make these from old copper water tubing if you have some "junk" pieces laying around. Save you some money. Otherwise you can buy those too.
You'd want to use crimps ideally on the wires to connect the lugs. Don't solder them if don't have to. You want a solid connection and solder may not do a good enough job alone. Crimping is pretty much the best way at this scale, as you'd be using pretty beefy wire gauge. I'm guessing at least 4 awg

Ok cool, I was thinking stainless would be the way to go so I'm grateful for that confirmation.

I actually do have some scrap 1/2" copper water pipe laying around! Really? I can use that to make copper lugs? For wire I found some incredible deals on eBay for 2/0 and 4/0 to use with my batteries and inverters. I also bought a hydraulic crimper a while ago to ensure strong connections.

 

[OffGridInTheCity]

I actually do have some scrap 1/2" copper water pipe laying around! Really? I can use that to make copper lugs? For wire I found some incredible deals on eBay for 2/0 and 4/0 to use with my batteries and inverters. I also bought a hydraulic crimper a while ago to ensure strong connections.

Originally, I did some lugs out of copper pipe - beating 1/2 flat and the other end for crimping. But as the number of lugs added up over the years I started buying SELTREM from Amazon - they come in all sizes .... - https://www.amazon.com/gp/product/B06XKY75XJ/ref=ppx_yo_dt_b_search_asin_title
and they're not that expensive.

But I do use/beat copper pipe flat and drill holes for bolts for buss(s) for my powerwall