robbob2112
Doing more research, mosty harmless
Yes, I write novels (and it took me long enough to write it didn't take and post)
It looks like you built a 12v battery with cells 4p4s using a single 4s BMS. Are the jumper wires you are using between battery clusters large enough to carry the current? I see a 3000w inverter in the picture which is 235amps - which calls for a fuse at 300amps and wire capable of handling that many amps - i.e. 2/0 or 4/0 welding wire. I can't tell from the pictures but that looks like only 2awg or so based on relative size.
If you want to run smaller than that you can, but it needs a fuse to blow if you exceed it.... I would suggest a 3 fuse MRBF holder to be able to break the amps if there is a short. I suggest the 3 holder because it attaches with wire verse being bolted directly to the terminal. And the type cells you have with the double terminal have been reported to have the terminals break off so you don't want to have any force that bends them up and down or side to side.
You need to install the rest of the bolts into the battery terminals or you are asking for corrosion and hot spots. Did you use no-ox-id special A or similar on all of your terminals and bus bars? If not you are asking for trouble down the road.
For your charging issue -
From what you are saying it sounds like you didn't use a bench power supply to bottom balance them before assembly. And you didn't top balance them either. Which means the COVP is going to be hit and you will stop charging. This will happen frequently until you have fully cycled them probably for months.
A couple of other notes -
There aren't any separators between cells in case you rub through the blue shrink-wrap - In any application that is recommended and in a mobile application it is required to have separators.
It looks like the cells are sitting straight on the wood platform - it needs to be lined with something non-conductive and smooth to prevent rubbing damage under them... you can easily cause a vent from rubbing a hole in the bottom - there is a recent thread on the topic where that happened.
Compression and restraint - a hotly debated topic - but the cells expand and contract as they charge and discharge - this is going to cause them all to move apart from each other - rubbing the bottoms and applying force to the bus bars. I can't tell from the pictures if they are just copper with a kink covered in shrinkwrap or if they have a metal braid under there. I suspect just metal from the uniform shape of them all. If so that means they will be constantly pulling and pushing on the terminals everytime you charge/discharge and it will eventually break a terminal off.
So, to fix things to not be a hazard to yourself and your loved ones -
To be honest - you should really have the battery in a case sealed up and vented to the outside - so nothing can go wrong - this might mean rethiking where it goes. I also think if you don't follow all the suggestions above you are asking for a fire.
It looks like you built a 12v battery with cells 4p4s using a single 4s BMS. Are the jumper wires you are using between battery clusters large enough to carry the current? I see a 3000w inverter in the picture which is 235amps - which calls for a fuse at 300amps and wire capable of handling that many amps - i.e. 2/0 or 4/0 welding wire. I can't tell from the pictures but that looks like only 2awg or so based on relative size.
If you want to run smaller than that you can, but it needs a fuse to blow if you exceed it.... I would suggest a 3 fuse MRBF holder to be able to break the amps if there is a short. I suggest the 3 holder because it attaches with wire verse being bolted directly to the terminal. And the type cells you have with the double terminal have been reported to have the terminals break off so you don't want to have any force that bends them up and down or side to side.
You need to install the rest of the bolts into the battery terminals or you are asking for corrosion and hot spots. Did you use no-ox-id special A or similar on all of your terminals and bus bars? If not you are asking for trouble down the road.
For your charging issue -
From what you are saying it sounds like you didn't use a bench power supply to bottom balance them before assembly. And you didn't top balance them either. Which means the COVP is going to be hit and you will stop charging. This will happen frequently until you have fully cycled them probably for months.
A couple of other notes -
There aren't any separators between cells in case you rub through the blue shrink-wrap - In any application that is recommended and in a mobile application it is required to have separators.
It looks like the cells are sitting straight on the wood platform - it needs to be lined with something non-conductive and smooth to prevent rubbing damage under them... you can easily cause a vent from rubbing a hole in the bottom - there is a recent thread on the topic where that happened.
Compression and restraint - a hotly debated topic - but the cells expand and contract as they charge and discharge - this is going to cause them all to move apart from each other - rubbing the bottoms and applying force to the bus bars. I can't tell from the pictures if they are just copper with a kink covered in shrinkwrap or if they have a metal braid under there. I suspect just metal from the uniform shape of them all. If so that means they will be constantly pulling and pushing on the terminals everytime you charge/discharge and it will eventually break a terminal off.
So, to fix things to not be a hazard to yourself and your loved ones -
- remove them all from the bay
- disassemble everything
- bottom balance all the cells - look up what that means as it has been described many times
- top balance things - look up what that means as it has been described many times
- clean everything
- apply no-ox-id special A to bus bars and terminals
- line the wood shelf with something smooth and slick so they can slide without damage
- use separators between cells - there is special foam for this
- re-assemble them using 2 screws per terminal - packs of 4 at a time so you can lift them
- make sure your wire guage is large enough for the connections between or use flat bus bars instead
- use a torque wrench on all the bolts - make sure all the metal is wrapped in electrical tape or heatshrink so you don't cause a short - having both bolts in and as finger-tight as you can before torquing should prevent shear problems
- provide some sort of restraint or compression - with them at middle charge they will be the flattest - so require the least force they expand as they either charge or discharge from the middle SOC - there is a white paper on this to read if you think that is wierd
- fuse with a class T or MRBF as close as possible the the positive post of the pack
- Make sure ALL wires connected to the pack are restrained within 4 inches of it so there is no force applied to the terminals.
- Make sure the battery is attached to the bottom where it sits so it can't slide around as a unit.
- PUT a plastic cover over the top of the battery to shield ALL the metal bits - a single dropped wrench or wire or a bump that touches any part of it to the overhead metal vents and you are looking at Disaster - vent hydrogen, spark, BOOM or kerwhump (the sound it makes when the air catches on fire.... think gas grill that didn't light for a bit, then it catches)
To be honest - you should really have the battery in a case sealed up and vented to the outside - so nothing can go wrong - this might mean rethiking where it goes. I also think if you don't follow all the suggestions above you are asking for a fire.
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