Building a 24v battery

[Boron]

Ive just finished building an 8s prismatic 50Ah battery inside a robust PVC portable box. It has shown me just how much attention to detail is needed to construct a safe an reliable bank suitable for a golf cart - withstands some vibration from being mobile. Sooooo many things crop up to think of. I am mindful of the xcellent teardown vids @Will Prowse did on proprietary Cheap charlie kit offered on EB an Alix. You are just getting a black box and very little info (or even what BMS is used). My building experience has shown just how much care and attention to detail is needed to arrived at a creditable piece of kit to last for years on a golf cart. Big issue is making all those wiring connections, ring terminals, crimp lugs wiring cable runs etc - a mine field. You dont want you connections working loose and arcing for example. So much fake stuff around.
Im sure there must be many members here who have faced similar issues. We all start out with an AGM mindset and take auto batteries pretty much for granted. You cant do that with a Lithium bank.

 

[time2roll]

Once built and installed I have found maintenance and attention has dropped to about nothing compared to lead-acid.

 

[Boron]

Once built and installed I have found maintenance and attention has dropped to about nothing compared to lead-acid.

Yes indeed, if you designed and built it properly in the first place for unattended lay person use. All components properly sized for max current. All joints fully secured. Enclosed against environment - moisture - critters - ants - lightning and so on, condensation from shed roof, flooding, hurricanes. If its for mobile use - golf carts, EVs, RVs etc then vibration, restricted space, access. Remote monitoring (fuel/range), heat sensor alarms. Emergency public disconnect in event of incident, accident fire.

Imagine say you had to design and build a system for unattended off grid use for a small remote community/school/village hospital. No tame techies around. That would make an interesting challenge for this board - given that Lifepos are now promising a 10 year life minimum.

AFAIK old school tubular Lead acid storage offers that kind of service (at a $$$$$$ price) but need trained but simple maintenance monthly https://www.exidegroup.com/sites/default/files/2018-11/Tubular LMX I&O Manual 2016-10.pdf. Maybe this is achieved by a visiting tech? Under routine use the installation should give 10-20 year uninterrupted use.

What do you reckon ?

 

[aliarifat794]

A high-quality BMS is crucial for safety, longevity, and performance of your lithium battery bank. Choose a BMS that suits the specific requirements of your battery bank.

 

[Delmar]

Ive just finished building an 8s prismatic 50Ah battery inside a robust PVC portable box. It has shown me just how much attention to detail is needed to construct a safe an reliable bank suitable for a golf cart...

What is the amp rating of the BMS?

I recently installed a SOK 100ah server rack battery in my 48V cart. BMS is 100A and my cart will draw 130A+ when accelerating. Works great but my burnout days are over. I did not mind the FLA watering but dealing with the constant corrosion drove me nuts.

 

[sunsurfer]

A high-quality BMS is crucial for safety, longevity, and performance of your lithium battery bank. Choose a BMS that suits the specific requirements of your battery bank.

This seems to big the biggest challenge for DIY builds.

 

[Boron]

What is the amp rating of the BMS?

I recently installed a SOK 100ah server rack battery in my 48V cart. BMS is 100A and my cart will draw 130A+ when accelerating. Works great but my burnout days are over. I did not mind the FLA watering but dealing with the constant corrosion drove me nuts.

My BMS was200A JK bd6a20s10p 100%oversized for my rig but it was $50 so go with the flo. Yup corrosion is a biggie, use STT fittings and fastners, watch out for cheap charlie using iron painted to look like brass - dont mix Al and CU/brass

 

[Boron]

This seems to big the biggest challenge for DIY builds.

IMHO dont go for a cheap BMS, JK or JBD

 

[time2roll]

This seems to big the biggest challenge for DIY builds.

By some of the reviews the BMS seems to be an issue with many drop in batteries too.

 

[Delmar]

My BMS was200A JK bd6a20s10p 100%oversized for my rig but it was $50 so go with the flo.

200A is just right for a 48V golf cart. An older 36V cart may even get close to 200A during acceleration.

My 48V 100A BMS will trip if I floor it from stopped. I may purchase a 2nd server rack for 200A and 10KWH.

 

[robbob2112]

This seems to big the biggest challenge for DIY builds.

I would say the biggest challenge for DIY builds is getting everything perfect.

Every crimp perfect. Every bolt torqued perfect. The wire secured in conduit or fastened down perfect. Perfect bus bars with the right amount of give for the cells to move the right amount. Perfect connections to the correct type fuse.

Sorting out all the good information from the bad information when it comes to videos and design advice. There are MANY folks out there that don't know what they are doing but giving advice that is at the least harmless to the worst of flat out dangerous.

Being hard headed and not listening to good advice. By all means decide how you are going to make your masterpiece your own, but it behoves people to listen, adjust and post changes for comment. Always try to understand the WHY of what is being recommended.

And, thinking you are going to read the forum for a week and build a perfect battery with no mistakes. There are so many gotchas to think about and ways to end up in the "up in smoke" forum it isn't funny.

Example is the house burned down guy - he was doing what victron recommended and using Mega fuses rated at 58v for his battery strings. I doubt Victron thought he would have 7 DIY parallel strings connected and not using their Lynx combiner. Wouldn't have really helped since the battery vent filled the room with an explosive mix of hydrogen and any little spark would set it off. Well it doesn't take more than a couple of videos of destructive tests of Mega fuses to see they erupt in a shower of sparks when they blow. He made several mistakes and all of them were in accordance with the MFG recommendations and best practices of DIY batteries at the time he did them.

 

[Boron]

Yes @robbob2112 its all sound words of wisdom - frighten the hell out of the Noob. Then so much of what is propounded as (armchair) wisdom comes from the trivial grasp of construction fundamentals - getting the perfect crimp for example - that in itself might consume several weeks of research only to discover that you are beset with Cheap Charlie knock offs and what you really need is a semi pro hydraulic crimp toolset plus genuine ring terminals from the maker to get truly authentic results to aircraft/MIL standards (I double down and, with difficulty for AWG6 also solder my crimps as well). As for bolts and torque values - dont get me started, solid busbars no-no for mobile apps and so on.

By some of the reviews the BMS seems to be an issue with many drop in batteries too.

@Will Prowse has done an excellent tear down of these drop in boxes - must view

 

[robbob2112]

Yes, frighten the noob until they learn enough to not burn the house down with their efforts.

Several of the people I have answered questions for fall into the to hard headed to listen catagory. I fully expect that one of them will burn the house down and possibly kill his children in the process of saving $20 on fuses.

I answered anyways and tried to impress on him the danger of a solar setup in a wooden entertainment center in his bedroom with the the kids down the hall. Four batteries in parallel with inadequate fusing. Someone else would have answered in my place so all I could do was try for safety.

 

[Boron]

Indeed @robbob2112 a very full collection of issues to be considered when venturing into Solar systems and battery storage. Its by no means a trivial matter, although the approach of some members clearly show an inadequate grasp of electrical technology. This must stem from exposure to auto electrical systems by Joe Public. It should be recognised that the application of electrical systems to vehicles has been developed for 100 years. Example take the ubiquitous push fit spade connectors and ring terminals. This was developed by Lucas in the 30's. Look closely and see its actually a clever design with a detent built in to prevent loosening. The tolerances and material specs are very important to get the right spring pressure. So its all the more frustrating to see the market flooded by Cheap Charlie knock offs. Beware of those so called auto kits and not the rubbish therein. Then compare with a genuine article.
When considering crimp connection then you really are on very dodgy ground - but enough said.

 

[HarryN]

I am not sure if it is worth building batteries up from cells anymore or not.

It depends on if you enjoy doing it as a hobby or if the goal is to just go use it.

If you price your time at $10 / hr, then you can buy the most expensive battery on the market and still come out ahead.

 

[robbob2112]

I am not sure if it is worth building batteries up from cells anymore or not.

It depends on if you enjoy doing it as a hobby or if the goal is to just go use it.

If you price your time at $10 / hr, then you can buy the most expensive battery on the market and still come out ahead.

From current pricing it is really only worth building from scratch for the larger batteries. i.e. 48v304ah or so, the pre-built are around twice the DIY cost and they are so heavy you need a wench to lift them. Where as DIY can be built in place if the place is chosen carefully.

A number of the current large pre-built batteries contain extenguishers these days. Those are availble to add to DIY as well, but from cost I doubt they are.

For the 48v100ah and smaller the pre-built are either break even or cheaper than the DIY.

 

[Boron]

From current pricing it is really only worth building from scratch for the larger batteries. i.e. 48v304ah or so, the pre-built are around twice the DIY cost and they are so heavy you need a wench to lift them. Where as DIY can be built in place if the place is chosen carefully.

A number of the current large pre-built batteries contain extenguishers these days. Those are availble to add to DIY as well, but from cost I doubt they are.

For the 48v100ah and smaller the pre-built are either break even or cheaper than the DIY.

hi @robbob2112 Think about it. When you start from scratch putting prismatics together (18650s is seriously anal) then you realise what goes into a proper job. If you buy a black box drop in job, you dont know whats inside (battery quality very suspect easy to fake and so on - so many ways for Cheap Charlie to cut costs to a dangerous extent) . Its not like a Car battery where you can buy with confidence from a reputable make.

So DIY building is all about getting known quality NOT saving money

FYI there are no viable fire extinguisher for a Lithium fire, Only tip buckets of sand over it all come back in a month

 

[robbob2112]

hi @robbob2112 Think about it. When you start from scratch putting prismatics together (18650s is seriously anal) then you realise what goes into a proper job. If you buy a black box drop in job, you dont know whats inside (battery quality very suspect easy to fake and so on - so many ways for Cheap Charlie to cut costs to a dangerous extent) . Its not like a Car battery where you can buy with confidence from a reputable make.

So DIY building is all about getting known quality NOT saving money

FYI there are no viable fire extinguisher for a Lithium fire, Only tip buckets of sand over it all come back in a month

Actually the fire extinguisher for lifepo4 does work fine. If a cell vents and the hydrogen gets spark all bets are off, but if that is vented outside all you have to deal with is the heat.

From my brother-in-law, a firefighter, they use a slurry that is primarily salt and water to put it out. A few other ingredients. It acts to cool it off and some will crystallize from the heat cutting off oxygen. Same thing they do with metal fires.

The internal type inhibits combustion inside the case is a similar manner that halon works. They are set off by heat and out gas enough to flood the case and then some.

You are thinking of lithium ion batteries which are impossible to put out once going.


I do agree with you a hundred percent on getting a known quantity

 

[Boron]

@robbob2112 yes good points LFP are so much safer
Q
Actually the fire extinguisher for lifepo4 does work fine. If a cell vents and the hydrogen gets spark all bets are off, but if that is vented outside all you have to deal with is the heat.

From my brother-in-law, a firefighter, they use a slurry that is primarily salt and water to put it out. A few other ingredients. It acts to cool it off and some will crystallize from the heat cutting off oxygen. Same thing they do with metal fires.
UQ
Some nasty gas gets expelled afaik HF. Deadly stuff. If you smell it (burn almonds) you are dead

 

[robbob2112]

@robbob2112 yes good points LFP are so much safer
Q
Actually the fire extinguisher for lifepo4 does work fine. If a cell vents and the hydrogen gets spark all bets are off, but if that is vented outside all you have to deal with is the heat.

From my brother-in-law, a firefighter, they use a slurry that is primarily salt and water to put it out. A few other ingredients. It acts to cool it off and some will crystallize from the heat cutting off oxygen. Same thing they do with metal fires.
UQ
Some nasty gas gets expelled afaik HF. Deadly stuff. If you smell it (burn almonds) you are dead

Almonds is hydrogen cyanide, and hydrogen sulfide is the smell of rot.

Either of which if outside if your battery space is vented. I know that went out the window with agm/fla/etc.

There is a thread on making a flame proof battery room that makes for interesting reading.