Im and idiot, as such sis something stupid and bought 8 EVE mb31 314ah cells and now I have a problem...

[juicedonwheels]

I did the math but I'm just an idiot so I need to ask from some people who know what they're talking about about. The saying goes, in series, you sum the volts.
In parallel, you sum the amps.
I'm series parallel, you sum some both...??

So if I wire 8 of these 3.2v 314ah cells
I have a 24v battery with 2512 amp capacity?
Is this correct? What am I missing here?

 

[ricardocello]

8 cells in series is 8 * 3.2V nominal = 25.6V nominal voltage
you still have only 314 Ah (but at 8x the voltage)

continuous amps for these cells = 0.5C = 157A
Maximum amps for these cells = 1.0C = 314A

If you want to talk energy, 8 * 3.2V * 314 Ah = 8.038 kWh
If you want to talk power, you can do 25.6V * 157A = 4092 W continuously

What fuse are you going to use to keep these safe?

 

[juicedonwheels]

you still have only 314 Ah (but at 8x the voltage)

Ok, but my question is in the series-parallel configuration. I'm reading it increases both amps and volts. What am I missing here? I honestly wouldn't know where to start. Do I wire series first than parallel? Parallel first? Or are you saying the amp capacity won't actually increase, which is contrary to whatever I've been reading that's Google search shoves in my face?

What fuse are you going to use to keep these safe?

Fuses?

...jk. I don't have an earthly idea as of yet. I want to wire these in both series and parallel and charge it up with an auxiliary alternator in my vam but honestly, the number here a are little intimidating so I'm not going to rush it until i know enough to feel confident

 

[MattMan119]

I did the math but I'm just an idiot so I need to ask from some people who know what they're talking about about. The saying goes, in series, you sum the volts.
In parallel, you sum the amps.
I'm series parallel, you sum some both...??

So if I wire 8 of these 3.2v 314ah cells
I have a 24v battery with 2512 amp capacity?
Is this correct? What am I missing here?

So you parallel the volts stays the same and the AH addes together
If you Series, then the volts adds, and the AH stays the same

if you combine you get a combo of both..

So 4S2P would be 4*3.2=12.8v and 2*312=624AH

Hope that helps.. depends on what voltage you need to what options you have!

 

[ricardocello]

Ok, but my question is in the series-parallel configuration. I'm reading it increases both amps and volts. What am I missing here? I honestly wouldn't know where to start. Do I wire series first than parallel? Parallel first? Or are you saying the amp capacity won't actually increase, which is contrary to whatever I've been reading that's Google search shoves in my face?

If you are trying to make a 24V (25.6V nominal) battery, and you only have 8 cells, you can only put the 8 cells in series to get there. no parallel.

If you have 16 cells, and you want 25.6V nominal, you can make two strings of 8 and put them in parallel. This is called 8s2p.
You can double the amps because you have two strings of 8.

You can also parallel pairs of batteries and put those in series, and this is called 2p8s. NO ONE does that however.

Questions:
What voltage are you trying to use (12V, 24V, 48V)?
How many cells do you have?

 

[juicedonwheels]

If you are trying to make a 24V (25.6V nominal) battery, and you only have 8 cells, you can only put the 8 cells in series to get there. no parallel.

If you have 16 cells, and you want 25.6V nominal, you can make two strings of 8 and put them in parallel. This is called 8s2p.
You can double the amps because you have two strings of 8.

You can also parallel pairs of batteries and put those in series, and this is called 2p8s. NO ONE does that however

Ok, herein lies my problem. This was my first conclusion when I looked at this years ago
When I took another, rather more serious look, what I have been reading doesnt convey this at all. I have scoured Google and duckduckgo high and low and I have found lectures explaining the 2p8s config and some straight up wiring a single series of cells in all parallel. It's right there in every single definition , you can wire series AND parallel and have "the best of both worlds". I am alive in wonderland right now.

I was going for a 24v battery. I have 8 cells in coming.

 

[ricardocello]

I was going for a 24v battery. I have 8 cells in coming.

Then your only option is 8s (no parallel).

When you start looking for fuses, please ask for advice here.
These cells store lots of energy, and the instantaneous current can melt wrenches.

 

[juicedonwheels]

Then your only option is 8s (no parallel).

When you start looking for fuses, please ask for advice here.
These cells store lots of energy, and the instantaneous current can melt wrenches.

Ok, but just humor me. Have you ever tried it? What do say would happen if you did? I can find you diagrams from people lecturing on it being possible. I haven't found one single authority that disproves it or even saying it cant be done. I see everyone wiring two separate series of 24v packs together in parallel, but there is nothing in the logic that would explain why. ..not really. You're the first person I've read that says you can't do it. I've been at this for days

 

[sunshine_eggo]

Ok, herein lies my problem. This was my first conclusion when I looked at this years ago
When I took another, rather more serious look, what I have been reading doesnt convey this at all. I have scoured Google and duckduckgo high and low and I have found lectures explaining the 2p8s config and some straight up wiring a single series of cells in all parallel. It's right there in every single definition , you can wire series AND parallel and have "the best of both worlds". I am alive in wonderland right now.

I was going for a 24v battery. I have 8 cells in coming.

2P8S is certainly workable (I'm 21P14S, but that's a very, very different situation), but you lose visibility on ALL cells. Yes, you can see cell pairs, but if there's an issue with a "cell" you won't know which one. You'll have to break the whole battery down to troubleshoot.

The preferred method is 8S2P, i.e., two separate 8S batteries, each with their own BMS that are then paralleled at their main terminals only - like you would parallel a couple of lead acid batteries.

 

[400bird]

Ok, but just humor me. Have you ever tried it?

I have, they are right. You only have one option to get to 24 volts.

What do say would happen if you did?

You won't have a 24 volt pack.

I can find you diagrams from people lecturing on it being possible. I haven't found one single authority that disproves it or even saying it cant be done. I see everyone wiring two separate series of 24v packs together in parallel, but there is nothing in the logic that would explain why. ..not really. You're the first person I've read that says you can't do it. I've been at this for days

You could build two 24 volt packs, but you'd need more cells, in multiples of 8.

 

[ricardocello]

(I'm 21P14S, but that's a very, very different situation)

 

[juicedonwheels]

Yeah, I guess y'all are right. I mean, it was going against instinct to think I could have a 24v 2500 ah battery out of these cells but once I had the idea I couldn't get it out of my head. Now I just think I don't understand what amps are. I was thinking of it as amps being the runtime of the battery riding the lighting(volts). Through the system.. I'm just an idiot after all

 

[juicedonwheels]

You can also parallel pairs of batteries and put those in series, and this is called 2p8s. NO ONE does that however.

Why is this?

2P8S is certainly workable (I'm 21P14S, but that's a very, very different situation),

Yeah, now that dreams of having a 24v 2500 ah van battery are gone, I like the sound of this configuration. Are these cells really that finicky that they become corrupted and fail? Is it a software issue? Both?

 

[robbob2112]

You need to start by watching some videos on basic electricity/electronics. Get a multimeter and an 8 pack of AA batteries.... now arange them and learn to use the meter and it will help your understanding a lot.

You also need to read through the DIY battery section for a few months before assembling the battery. Anytime you are tempted to do it sooner pick and read another thread in the 'up in smoke' forum....because any tiny mistake in assembly or connection will lead to your own post there.

Do ask lots of questions, we as a collective group like to help everyone.

 

[JanisD]

To darken the day - please, do what @robbob2112 suggested.

Some time ago i was lucky to be some 10 meters from car when repair mechanic accidentally shorted 90 Ah car battery.
Short PUFF, bright light and drops of molten lead everywhere. The positive terminal of battery simply evaporated. Luckily there was no easy flammable things nearby and he still has eyesight only by following the rule he and I was told long ago - "when connecting something powerful and not having eye protection, at the last moment turn away". Only some nasty burns on right cheek and holes in heavy overall.

I'm even scared to calculate, how many times more powerful Your battery is/will be, so learn and feel free to ask.

 

[juicedonwheels]

I get what you're saying. I have almost no experience with this and it only really dawned on me how precarious my situation is. I am a point of no-return however as winter has just came in, I am now fully committed to living in a van and I have cells arriving in the next week or two that I have to anticipate. I've ordered a bracket and am going to get a second alternator installed next week so I'll be ready to power this thing sooner than later. Im looking at these voltage regulators and alternator regulators from Sterling power and that's just stuff I was redirected to from reading of threads here. I won't have a ton of crazY appliances hooked up until I haven't all dialed, but I want to run lights, a small heater, and a way to run/charge powertools. I don't have infinite resources so I can't totally feel out on this. What kind of fuses are we talking about about here? Do I need to fuse the individual terminals? What is even the correct material to use to make the terminal connections? Should I ask this is another thread or does me being an idiot cover it?

 

[mikefitz]

going to get a second alternator installed next week

This is a 24 volt alternator, correct? What power rating? Is this the only charging method?
It will need some kind of control system to charge the battery at the correct voltage and current.

The battery cells arranged as a 24 volt battery will need a battery management unit, a BMS, what unit will you be using?

All the stuff you will, be powering off the battery, what voltage and power rating of these devices?

Will you have a 24 DC to 120 AC converter, an inverter, if so what power ?

 

[robbob2112]

I get what you're saying. I have almost no experience with this and it only really dawned on me how precarious my situation is. I am a point of no-return however as winter has just came in, I am now fully committed to living in a van and I have cells arriving in the next week or two that I have to anticipate. I've ordered a bracket and am going to get a second alternator installed next week so I'll be ready to power this thing sooner than later. Im looking at these voltage regulators and alternator regulators from Sterling power and that's just stuff I was redirected to from reading of threads here. I won't have a ton of crazY appliances hooked up until I haven't all dialed, but I want to run lights, a small heater, and a way to run/charge powertools. I don't have infinite resources so I can't totally feel out on this. What kind of fuses are we talking about about here? Do I need to fuse the individual terminals? What is even the correct material to use to make the terminal connections? Should I ask this is another thread or does me being an idiot cover it?

I would suggest you buy a pre-made battery to use. Something like a 24v280ah LiTime battery.

LiTime 24V 280Ah LiFePO4 Lithium RV, Marine Battery Low-Temp Protection

LiTime 24V 280Ah Low-temp. protection battery Max 7168Wh Energy & Up to 15000 Deep Cycles, Perfect for Solar System, Camping, Boat, Home Energy Storage

www.litime.com

And sell your cells to recoup the money. The needed tools and know-how to do it safely takes money and time. Your short time until you need them means you don't have the time to learn.

I say sell verse store because they would need to be carefully charged individually with a bench supply or they will eventually go flat.

I might actually be interested if the price is right and we can arrange a meeting. Post a price here or start a thread in the for sale section...list where they came from...not looking to take advantage.

Heating your van with solar is a non-starter... electric heat consumes so much power you don't have the room to mount enough panels to charge it. You need an external diesel heater or similar. Using the alternator to charge the battery would require a much larger battery bank.

25.6v x 280ah = 7168Whrs
7168Whrs / 1500w heater = 4.8hrs.
The heater cycles so maybe twice that ....

200amp 24v alternator = 4800W per hour so you would have to run the engine 2 hours to charge.

There are losses so 80% of those numbers is more realistic.

If you proceed with building a battery it will cost you another $200 to $300 to get the tools, bench PSU, bus bars, and BMS. Adding compression or restraint will be more on top of that.

Whatever you do you will need a class T fuse, a fuse block for the other circuits, heavy duty wires a either pre-made or a quality crimper ($120) and lugs ($20)... in your case I would suggest careful measurements and order pre-made for the large cables.

Lots to it, and if you start buying stuff before you have a complete plan you will spend more than if you wait, plan, and only buy what you need.

 

[HRTKD]

@juicedonwheels, we're not trying to piss in your pudding. You're in a hurry-up situation and these systems require patience and planning. We don't want you to get hurt, so we're suggesting that you step back from a DIY battery. We can be a very critical bunch but it's usually accompanied by constructive criticism.

 

[MrSparkle]

I'm even scared to calculate, how many times more powerful Your battery is

As Ricardocello said:
If you want to talk energy, 8 * 3.2V * 314 Ah = 8.038 kWh
further:
8.038kWh x 0.86 = 6.9 kilograms TNT (15.2 lb)

Party time!

 

[juicedonwheels]

I tried to return these things before they arrived and they showed up anyway. Im trying to make a grocery list and prices and I feel really dumb. i dont know what materials to use to connect the terminals together for the 8s. They sent 2 different types of busbars and a bag of screws and washers. Is that all I need? What about for the terminal leads? how do I know if the busbars they sent are sufficient. They dont look copper and wouldnt i want copper? sry for being such a rookie but you guys seem pretty cool and i dont trust ChatGPT or AIs to come correct

 

[sunshine_eggo]

I tried to return these things before they arrived and they showed up anyway. Im trying to make a grocery list and prices and I feel really dumb. i dont know what materials to use to connect the terminals together for the 8s. They sent 2 different types of busbars and a bag of screws and washers. Is that all I need? What about for the terminal leads? how do I know if the busbars they sent are sufficient. They dont look copper and wouldnt i want copper? sry for being such a rookie but you guys seem pretty cool and i dont trust ChatGPT or AIs to come correct

If you include pictures of the bus bars, screws, and a close up of the battery terminals, we can help.

 

[juicedonwheels]

i appreciate the help and I apologies if the questions i am asking are already answered out there but i try to make a final decision, its like I come across conflicting or new information thats significant enough to change what I need. So they sent 2 different types us bus bars with these cells. 4 bent ones and 4 flat ones. The application for this battery will be for appliances and backup in a camper-van..

When I tried to look up how to size bars bars for the battery i feel its the most complicated formula for the whole build and requires information i dont have yet. Very hard to find uniformity for the same question when trying to size stuff up for this

 

[sunshine_eggo]

i appreciate the help and I apologies if the questions i am asking are already answered out there but i try to make a final decision, its like I come across conflicting or new information thats significant enough to change what I need. So they sent 2 different types us bus bars with these cells. 4 bent ones and 4 flat ones. The application for this battery will be for appliances and backup in a camper-van..

When I tried to look up how to size bars bars for the battery i feel its the most complicated formula for the whole build and requires information i dont have yet. Very hard to find uniformity for the same question when trying to size stuff up for this

The bent ones are preferred as they allow the cells to expand/contract with charging/discharging without putting stress on the cell terminals.

 

[robbob2112]

Take a closeup of the QR code that is in focus