Why get a 24v

[offgridcrazy]

I'm wondering if there is a reason to get a single Ampere 24v 100ah vs. 2 Ampere 12v 100ah? It's cheaper to get 2 x 12v's. I have a 24v Inverter that I'm not ready to replace and need to have a 24v bank.

 

[John Frum]

Putting 12 volt batteries in series allows their voltage to drift relative to one another.
This is not a "good thing"TM.

 

[chrisski]

I'm wondering if there is a reason to get a single Ampere 24v 100ah vs. 2 Ampere 12v 100ah? It's cheaper to get 2 x 12v's. I have a 24v Inverter that I'm not ready to replace and need to have a 24v bank.

Either setup will have no significant performance in performance over the life of the battery.

Decision to go with one or two batteries in series has been based off availability of the battery, size, and weight.

For the space I had for my first battery, I put 60 LBS 6 volt batteries 2s2p. More than that was too heavy to lift into the tray by myself.

If the reasons listed above about space and weight were not a problem, I would have went with huge 100 lbs batteries or larger 2.5 volt batteries strung to 12 volts.

Companies like Trojan sell large individual cells 2.5 volts to string into a battery of your choice: 12v 24v 48v etc. That way mere mortals can lift these into place and assemble to a battery.

I replaced it with lithium 2 x 8s cells that took up less space and had 2.5 times the energy.

 

[Checkthisout]

24V drop-in for rigs with 24V systems.

 

[Bobert]

If you are going to switch to 12v later old go ahead with 2 12v batteries it will work fine it’s just more complicated especially if the batteries are lower quality and tend to wander from each other. It’s still doable and works well.

 

[timselectric]

It's not a good idea to put batteries that have BMS's in series. It adds routine maintenance where it would otherwise not be needed. Just buy the proper voltage batteries for your system. If you build a house on a bad foundation. You won't be able to enjoy the house.

 

[chrisski]

It's not a good idea to put batteries that have BMS's in series. It adds routine maintenance where it would otherwise not be needed. Just buy the proper voltage batteries for your system. If you build a house on a bad foundation. You won't be able to enjoy the house.

What routine maintenance?

I do agree that a BMS in series if one trips could be bad.

 

[timselectric]

They will drift apart from each other.
Then they have to be charged individually, to be back in sync again.

 

[Bobert]

They will drift apart from each other.
Then they have to be charged individually, to be back in sync again.

I have a 48v bank (4s) continuously in use since November of 2021. I have a 48v balancer so I don’t have to individually charge the batteries every year or so. It works great. Don’t knock it till you have tried it. It has been done for years out of necessity. As long as the bms is rated for it and you are prepared for extra complexity go for it.

 

[timselectric]

Why add complexity?
Just do it right, from the beginning.
That's what this forum is about. Helping people do it right. I can understand If you are trying to work with what you already have. But if you're starting from scratch. Might as well take advantage of the latest technology. Placing batteries in series is from the days of led acid batteries.

 

[time2roll]

What is the savings after adding a balancer between the two batteries?
I would take 2x 24v in parallel any day.

 

[740GLE]

What the intended use? Are you planning to run these aggressive? Say 100-20% each day?

If the set up will be lightly used I’d have no concerns with two in series knowing I may have to pick up a balancer or apply a “top balance” to a battery once in a blue moon.

Are there storage considerations? Easier to move two batteries for the install vs one?

 

[JJJJ]

Batteries in parallel can be a good mix and provide redundancy if needed.

 

[Pi Curio]

I'm wondering if there is a reason to get a single Ampere 24v 100ah vs. 2 Ampere 12v 100ah? It's cheaper to get 2 x 12v's. I have a 24v Inverter that I'm not ready to replace and need to have a 24v bank.

24V 100Ah, a single BMS regulating all 8 cells simultaneously.

Further down the line, having additional 24V 100Ah in parallel to form a 24V 200Ah battery storage gives you storage redundancy.

 

[jmsol]

I'm wondering if there is a reason to get a single Ampere 24v 100ah vs. 2 Ampere 12v 100ah? It's cheaper to get 2 x 12v's. I have a 24v Inverter that I'm not ready to replace and need to have a 24v bank.

Is it really cheaper?

Looking at 1 pc LFP 24V vs 2 pcs LFP 12V, the prices vary very little. It's likely you already got the batteries by now but if not, I can see no disadvantages with a single 24V.

 

[Rednecktek]

Another thing to consider is the max amperage draw. The 12v batteries most often have a 100a BMS and the 24v may have a 200a limit which can feed 4800w of inverter.

Gotta check the BMS specs.

 

[740GLE]

whereas 2x 12v in series are only 1200w max.

Connecting in series adds voltage, but not amperage, and that includes BMS output.

Umm what? If you run 2x 12v batteries in series for 24v and each of the batteries have a 100a BMS, that’s ~2400 watt output.

It can output that exact same at a single 24v battery also with a 100a BMS, cause that are exactly the same set up.

 

[Rednecktek]

Umm what? If you run 2x 12v batteries in series for 24v and each of the batteries have a 100a BMS, that’s ~2400 watt output.

It can output that exact same at a single 24v battery also with a 100a BMS, cause that are exactly the same set up.

Sorry, you're right. I can new maths! ?

Let me go fix that...

Back to the OP, that is something I've always found frustrating is when 2x 12v batteries are cheaper than 1x 24v when there is less plastic, less assembly, and only 1 BMS which is a significant chunk of a DIY battery build.

Paying for the privelage I guess.

 

[740GLE]

My guess scale of market, everyone loves and can find a use for a 12v battery, not so much for 24v.

 

[Cryptokook]

OP's question is one I am also asking as I am planning a new 24v inverter system for my trailer. The only advantage that I can see in using 2 x 12v in series is that it gives you the ability, in a pinch, to decouple the batteries, put them in parallel, and still be able to charge the batteries and feed the 12v DC loads if your DC to DC converter takes a crap while in the bush. That is if your battery power wires and fusing is sized appropriately. Also, as mentioned already, 12v replacements are much easier to come by in a pinch. I am thinking it might be easier to just carry a spare converter.