diy solar

diy solar

280ah Lifepo4 Leisure Battery - Build Thread

Daledevon said:
Has anybody come up with a good case solution for these yet?
Click to expand...

www.hulkenbergshop.nl

Stapelbak met deksel - 400 x 300 x H 250 mm (gladde bodem) - grijs - Transoplastshop

Geheel gesloten grijze stapelbak met deksel. met gladde bodem en gesloten handgrepen. Kunststof dekselbak 400 x 300 x H250 mm met scharnierdeksel en twee snap-schuifsluitingen.
www.hulkenbergshop.nl www.hulkenbergshop.nl

Shipping is around 11 euros if you’re in mainland Europe but you can also find them locally across Europe. Try their chat function on the site if you need a shipping quote, they reply fast.

Otherwise these things are called eurobox shipping containers and they’re the standard here. They’d probably fit 8 of the cells inside as they’re a bit long on the length side But I figure with the bms and some insulation you can make them work.

The problem with every other battery box I’ve researched is that they’re not tall enough for these.
 
mrdavvv said:
I guess the little black things in the positive output of the battery are fuses?, if so.. why not put only 1 to the main line?. Also this main line should be conected to the battery protect, so it can disconect all the loads if necesary.
Click to expand...

Mrdanielmh said:
I thought it made sense to fuse everything seperately so that if 1 fuse blew I still have other charging capabilities.

I thought the Victron Battery Protect was for load, so I only had it attached to the fuse box load so that it would shutdown access to appliance if the voltage of the battery was too low.
Click to expand...

I haven't read through the whole thread so you've probably worked all this out but just in case.
  1. @Mrdanielmh is correctly using the battery protect, it cannot be used the way @mrdavvv describes because (A) its not bidirectional and (B) it cannot be used directly inline with an inverter
  2. You are also on the right track regarding fuses, every time you step down to a smaller wire size, you need a fuse to protect that wire, so unless all your wiring is the same gauge as your main battery cable, you are doing it right. But you may also want a main battery fuse (MRBF or class T ideally)
And then I have an open ended question/thought, IDK what the best practice is or should be for protecting the multiple smaller wires going to and from the BMS. If one or more of those wires shorts or opens (and there are 6 individual pieces of wire and 12 total connections), it seems there is at least a theoretical risk of a situation where too much current is forced through one or more of the wires, and no fuse is sized properly to protect the smaller gauge wire attached to the BMS. How are others with similar BMS' dealing with this? Is this a tempest in a teapot or something to take seriously? Seems as a best practice a fuse on each of the 10AWG wires would be the way to go, but maybe I'm overthinking it.
 
Dzl said:
I haven't read through the whole thread so you've probably worked all this out but just in case.
  1. @Mrdanielmh is correctly using the battery protect, it cannot be used the way @mrdavvv describes because (A) its not bidirectional and (B) it cannot be used directly inline with an inverter
  2. You are also on the right track regarding fuses, every time you step down to a smaller wire size, you need a fuse to protect that wire, so unless all your wiring is the same gauge as your main battery cable, you are doing it right. But you may also want a main battery fuse (MRBF or class T ideally)
And then I have an open ended question/thought, IDK what the best practice is or should be for protecting the multiple smaller wires going to and from the BMS. If one or more of those wires shorts or opens (and there are 6 individual pieces of wire and 12 total connections), it seems there is at least a theoretical risk of a situation where too much current is forced through one or more of the wires, and no fuse is sized properly to protect the smaller gauge wire attached to the BMS. How are others with similar BMS' dealing with this? Is this a tempest in a teapot or something to take seriously? Seems as a best practice a fuse on each of the 10AWG wires would be the way to go, but maybe I'm overthinking it.
Click to expand...
It seems that you may have missed the updated diagram on page 2 where these were removed. The wires you referenced are part of the BMS. They are soldered on the PWB and would probably all receive a ring terminal and be put on the same post. They could conceivably be crimped into a single terminal. Not much chance of single wire failure seeing as though they are only about 8" long.
 
Haugen said:
It seems that you may have missed the updated diagram on page 2 where these were removed.
Click to expand...

Oops yeah, I saw the updated diagram on page 1, not the one on page 2, looks like OP moved away from individual cells, and went with Valence. Points 1 and 2 still apply (and look to still be correct in that diagram).

The wires you referenced are part of the BMS. They are soldered on the PWB and would probably all receive a ring terminal and be put on the same post. They could conceivably be crimped into a single terminal. Not much chance of single wire failure seeing as though they are only about 8" long.
Click to expand...
Yeah the chance of a problem is probably pretty low, but still, I think, possible and unprotected. There are 12 potential points of failure (6 solders, 6 crimps, and if the wires are about 8" 6x8" is 4 feet of wire).
 
Im still going DIY individual cells, the valance was just for demonstration! Interesting point about fusing the BMS cabless, npt something ive read about before!
 
Mrdanielmh said:
Im still going DIY individual cells, the valance was just for demonstration! Interesting point about fusing the BMS cabless, npt something ive read about before!
Click to expand...

Yeah, I haven't heard of anyone fusing the individual BMS wires like that either, however I've seen multiple builds where two smaller wires are used in place of a single main battery cable, and both wires are fused separately at a level that protects the individual wires. Dhowman's design is one example, there is some discussion relevant to this on page 4
 
Honestly, I'm just using PowerPoint :eek:

i'm a bit confused by that diagram, as it doesn't look like the BMS is in between battery negative and input/output connection!

Updated Diagram (Zoomed Out of Battery setup):

1591008742869.png

Zoomed into Battery and BMS Configuration:

1591008782910.png
 
Dzl said:
......IDK what the best practice is or should be for protecting the multiple smaller wires going to and from the BMS. If one or more of those wires shorts or opens (and there are 6 individual pieces of wire and 12 total connections)
Click to expand...
My BMS has internal over current protection for the BMS sensing wires. In a large pack like my 17S 48 volt pack there is a risk of high voltage, the tradeoff of accuracy is important. A fuse will add unnecessary resistance to the sensing wires and result in incorrect voltage measurements. They do not even recommend cutting or extending the sensing wires.
 
Ampster said:
My BMS has internal over current protection for the BMS sensing wires. In a large pack like my 17S 48 volt pack there is a risk of high voltage, the tradeoff of accuracy is important. A fuse will add unnecessary resistance to the sensing wires and result in incorrect voltage measurements. They do not even recommend cutting or extending the sensing wires.
Click to expand...
Ampster beat me to it.
The BMS is already controlling the current and has its own protection. The microvolts of differential between the lines would only be complicated by adding 2 more connections per line with a fuse.
See the pic.
This is literally how long the wires are. If they were 6 FEET long, I would agree that there is a possibility of one wire failing, leaving more current to another. In fact, if additional length is needed, I recommend going to a bus and using a single heavier conductor simply due to the resistance of the wire..
 

Attachments

  • 20200601_113639.jpg
    20200601_113639.jpg
    62.3 KB · Views: 18
Ampster said:
My BMS has internal over current protection for the BMS sensing wires. In a large pack like my 17S 48 volt pack there is a risk of high voltage, the tradeoff of accuracy is important. A fuse will add unnecessary resistance to the sensing wires and result in incorrect voltage measurements. They do not even recommend cutting or extending the sensing wires.
Click to expand...

Just to be clear, I'm not referring to the BMS sensing wires/balance leads, I'm referring to the main wires that pass current.

Adding a fuse would add some resistance and an extra point of failure (taking the total from 12 points of failure to 18).

Haugen said:
The BMS is already controlling the current and has its own protection.
Click to expand...

Your BMS has overcurrent protection, to protect itself, not to protect a 10AWG wire. Overcurrent for your BMS is >120A, but 10AWG can only handle half of that.

The microvolts of differential between the lines would only be complicated by adding 2 more connections per line with a fuse.
Click to expand...

I agree but this is one of the potential problem of going with multiple smaller wires in the first place as I understand it, without fuses there are already 12 connection points that could fail, or that could cause differences between the wires. With fuses you now have 18 points of connection but the wire is protected.

I recommend going to a bus and using a single heavier conductor simply due to the resistance of the wire..
Click to expand...

I agree


Y'all are probably right that the risk is very low, I don't contest that, but I'm still not totally satisfied with leaving those wires unprotected, maybe its a non-issue, but the rule I've heard many times in marine electrical to fuse every time you step down to a lower unprotected wire size has stuck with me and seems reasonable. But I've never considered a scenario like this before, so maybe I'm misapplying the rule, taking it to the extreme, or overlooking something (Or just being a nervous nelly :) ). In either case your system isn't going to spontaneously combust or be drastically less safe either way.
 
Last edited:
q
Dzl said:
Just to be clear, I'm not referring to the BMS sensing wires/balance leads, I'm referring to the main wires that pass current.
Click to expand...
Yes, I understand that. My comment was in response to the OP original question about the sensing wires, but the thread has diverge to talk about the current carrying wires and your point is a good one about changing wire size and the need for over current protection for the smaller wires. I wonder how short they would need to be before being joined to a large conductor and could to be considered safe, or at least a small risk?
 
Alrighty folks, a great update! I have just taken delivery of my battery cells. Im very impressed withcthe packaging. The batteries arenin fantastic condition andnall measuring 3.33v!

IMG_20200605_144506.jpgIMG_20200605_144613.jpgIMG_20200605_144722.jpgIMG_20200605_144751.jpgIMG_20200605_145204.jpgIMG_20200605_145158.jpg

Next step is to hook these up in parralel and get a top balance completes!
 
Exciting! I've been following this thread with anticipation. You ordered the cells mid April, correct? I need to get mine ordered so I can build something in like... August. Haha!
 
Really chuffed with the cells.

Update

Cells were hooked up in parralel overnight
TThis morning i connected them up to the power supply at 3.4v.

Im planning om doing the stepped approach. 3.4, 3.4 and finslly 3.6

Its moving very slowly. Ive been documenting lots over on instagram (harrisvanadventures) but ill post up on here too!
 
You must log in or register to reply here.

Similar threads

M
Buy now or wait? 48v battery build
2
Replies
26
Views
2K
[Au]Ray
[Au]Ray
robbob2112
I asked chatgpt to design a battery
2
Replies
29
Views
1K
robbob2112
robbob2112
Mattb4
My first LiFePO4 build to achieve a cheap 105ah 24vDC.
Replies
16
Views
1K
Mattb4
Mattb4
D
Fogstar Leisure Battery (UK) 280AH vs 300AH
Replies
2
Views
1K
Frugalone
Frugalone
V
Finished my 12v 304ah battery build with heating
Replies
1
Views
402
Partimewages
Partimewages

diy solar

diy solar
Back
Top