8x100ah vs 3x280ah?

[skmt7000]

Looking at prime deals to make a 12v 800ah bank from the cheap chinese brands. Cold protection is of no concern.

I'm wondering if i'm better off with 8 x 100ah or 3 x 280ah. I see some of the 100ah say max 4 batteries in parallel -- is that a hard rule to stick too?

One advantage I see in 8 batteries is these companies seem to be a crapshoot for warranty, and consistency/longevity of product is uncertain. So, breaking the bank in 8 pieces, if one 100ah battery goes defective and they won't replace, then not as big a loss as if a 280ah is junk.

Also would you pay an extra $240 total for bluetooth? Seems like alot proportionally. And it's hard to find in batteries above 100ah.

Here's a few options i'm looking at, lmk in if you have any info:

Wattcycle 100ah. $160 x 8 = $1280
Elefast 100ah bluetooth. $190 x 8 = $1520
Chins 280ah. $414 x 3 = $1242
Newtipower 300ah. $447 x 3 = $1341
Eco-Worthy 280ah. $391.66 x 3 = $1175

 

[BentleyJ]

If you decide to go with 8 batteries, they can all be connected in parallel using a bus bar like this which adds cost and complexity.

PowerBar 600A BusBar - Eight 3/8"-16 Studs - Blue Sea Systems

Provides compact high-amp busing.

www.bluesea.com

Personally I would prefer fewer, high capacity, quality batteries over a bunch of cheap junk that was expected to fail frequently.

 

[wpns]

Definitely get some kind of BMS comms, wires, BT, whatever, then you will know when things start to go south.

 

[ScrotpusGobbleBottom]

I second that. You need to know the voltage of the cells.

I wouldn't buy any battery unless I could see the individual volts of all the cells.

 

[skmt7000]

If you decide to go with 8 batteries, they can all be connected in parallel using a bus bar like this which adds cost and complexity.

PowerBar 600A BusBar - Eight 3/8"-16 Studs - Blue Sea Systems

Provides compact high-amp busing.

www.bluesea.com

Personally I would prefer fewer, high capacity, quality batteries over a bunch of cheap junk that was expected to fail frequently.

Why can't I just use cables from battery post to battery post like normal?

 

[BentleyJ]

Why can't I just use cables from battery post to battery post like normal?

Because is more difficult to keep the current balanced between each battery.

 

[Bananaman321]

Judging by the prices I assume this is a 12v system you're talking about here

That being said I don't see any benefit to building a 12v system of any size we might as well go with a 24 or 48 Volt

That being said the cabling alone is gonna offset the savings associated with buying these small cheap batteries

 

[skmt7000]

Because is more difficult to keep the current balanced between each battery.

The amount of cable i would need to use a common buss bar would be uneconomical.

If you had to choose between 8 x 100ah in series (post to post) with bluetooth vs. 3 x 280ah (no blueooth) in parallel, then which would you choose?

 

[skmt7000]

Judging by the prices I assume this is a 12v system you're talking about here

That being said I don't see any benefit to building a 12v system of any size we might as well go with a 24 or 48 Volt

I don't have a house. It is a boat which is already 12v.

 

[Bananaman321]

I don't have a house. It is a boat which is already 12v.

got it didn't catch that part that clarifies things thank you

 

[wpns]

The amount of cable i would need to use a common buss bar would be uneconomical.

If you had to choose between 8 x 100ah in series (post to post) with bluetooth vs. 3 x 280ah (no blueooth) in series, then which would you choose?

Do you mean parallel? I’d go with BT unless the 280ah have RS485/RS232/CAN

 

[740GLE]

What loads will the batteries be sourcing?

I’d much rather have 3 batteries vs 8.

 

[skmt7000]

Do you mean parallel? I’d go with BT unless the 280ah have RS485/RS232/CAN

Yes meant parallel

 

[Suijkerbuijk]

Why can't I just use cables from battery post to battery post like normal?

Think like this .
Power is like water so it always thake the way with the les resistance.
Thank to that your battery will not charge or discharge the same way .
Special if you use cable to cable .
A lead battery is more forgivable thanks to its internal resistance.

So the best is use of bus bar and the cable's all the same type and length.
On a lifepo4.

 

[Bananaman321]

Personally I'd like to have a way to isolate a single battery if there were a problem (circuit breaker) you're putting a lot of faith in those BMSs

Even more so with cheap batteries not to mention being on a boat is all the more reason for concern. If there happened to be a short in one pack you'd have the currant of all of the other packs well you get the picture.

See if you can't find a tear down video on a battery you might be considering make sure has an internal fuse for protection if the BMS were to fail in a short situation.

 

[Suijkerbuijk]

Personally I'd like to have a way to isolate a battery if there were a problem (circuit breaker) you're putting a lot of faith in those BMSs

Even more so with cheap batteries not to mention being on a boat is all the more reason for concern. If there happened to be a short in one pack you'd have the currant of all of the other packs well you get the picture.

If you set the system correct .
And a good top balance.
Never will the bms shutdown the charge or discharge.
Its a lest safety systeem to protect the cells .
So use only 90% and you will not over use the bms.
Its still a relay combo or mosfet that is use .
What switch on and of under load .

 

[skmt7000]

What loads will the batteries be sourcing?

I’d much rather have 3 batteries vs 8.

Basically a constant 12 amps 24/7. In the summer that bumps up to 25-30 amps constant. And then occasional short draws for tools, microwave, toaster up to 1500w.

I do have 1500w solar. So generally the largest constant draw coming out of the batteries is about 27a at night durimg summer.

 

[Suijkerbuijk]

I don't have a house. It is a boat which is already 12v.

I use on my boat 2x150ah .
So it do what it need to do.
Run fridge and freezer with out problems
On a boat i go for good stuff .
On sea you are on your own.

My own battery cost 1000 euro for 1 x150ah grade a cells (come from Franse and are Victron support)
I do not thake Risk.

 

[Bananaman321]

I'm just saying there's what you can do and what you should do. Consider all the options and points of failure and what could happen. We do not live in a perfect world i promise you sh*t will fail.

 

[Bananaman321]

It's suggested place to start that's money you'll spend on your system

He also has a ton of videos and online schematics free

 

[skmt7000]

So the primary benefit of bluetooth is I can see if cells are becoming imbalanced? And in that event, then what? What can really be done to repair the battery?

At $160 (and dropping), it seems like it would need to be a cheap/easy fix or else just replace.

 

[Suijkerbuijk]

So the primary benefit of bluetooth is I can see if cells are becoming imbalanced? And in that event, then what? What can really be done to repair the battery?

At $160 (and dropping), it seems like it would need to be a cheap/easy fix or else just replace.

A lot .
You can see that the volt are out of balance and than you can slow charge the battery and with some rest it will balance it self

You can see that charge or the discharge is safety mode.

Well see attach files of my battery than you can see what can do.

The last 2 picture are from a battery that is now balance the cells .

 

[Bananaman321]

If you set the system correct .
And a good top balance.
Never will the bms shutdown the charge or discharge.
Its a lest safety systeem to protect the cells .
So use only 90% and you will not over use the bms.
Its still a relay combo or mosfet that is use .
What switch on and of under load .

And if per se a mosfet were to fail in a short situation you would have to disassemble a loaded circuit. Not to be argumentative or anything but I live in a world where sh*t Fails and it's never in a good way.

Throwing caution to the wind with high amperage cheap products is never a good idea.

Murphy's law is one that I live by

Always have redundancy in your system safety is our first priority.

Just consider what can happen will happen and act accordingly to prevent it.

 

[wpns]

So the primary benefit of bluetooth is I can see if cells are becoming imbalanced? And in that event, then what? What can really be done to repair the battery?

As others have mentioned, when something starts to fail, you can figure out why, and then you can take corrective action. A battery that is getting out of balanced can be held at a (higher?) voltage for a period of time in order to get back in balance.

If you are going with cheap batteries, you are definitely going to want to have a high-quality breaker(or a cheap breaker and a high-quality fuse.) so you can take individual batteries off-line for maintenance or repair.

 

[Bananaman321]

If you set the system correct .
And a good top balance.
Never will the bms shutdown the charge or discharge.
Its a lest safety systeem to protect the cells .
So use only 90% and you will not over use the bms.
Its still a relay combo or mosfet that is use .
What switch on and of under load .

Check out this video Will Prowse just release today