2v VS 12v Batteries

[Farai]

Hi, 

I need your advice. I intend to put together a 3000ah 48v battery bank. I had intended to use 48 x 12v250ah batteries to achieve this however when I asked victron about the best way to balance the bank they strongly advised against using 12v batteries and indicated that 2v batteries should be used in series. 

 

Can anyone shed more light on this issue, 2v VS 12v batteries? 

 

Your advise will be much appreciated 

[Jaco De Jongh]

Welcome Farai

I would rather look at having FreedomWon or similar manufacturers build me a unit like that, I dont want to be close to an installation with 12 strings of 250AH batteries in parallel when something goes wrong. 

Consider lithium, Freedom Won, Blue Nova and the likes, or if you insist on Lead Acid, try Raylite M-Solar 2MTE29F 1655Ah 4V Battery  2 strings of these should do well. 

[Mike]

i use the Raylite Msolr 2volt cells 1050ah, 3 years in on them, once cycled x 1. For me once a month gravity check and top up with distilled water, done..... if my inverters could work with lithiums, i would just for more ease of use, space savings, etc, but hey these FLA's sure work well, totally off grid and fully charged by 11am most days..

[DeepBass9]

For a large bank, it is better to have one string of large batteries, rather than many parallel strings of smaller batteries due to balancing issues.

[Gerlach]

1 hour ago, Mike said:

i use the Raylite Msolr 2volt cells 1050ah, 3 years in on them, once cycled x 1. For me once a month gravity check and top up with distilled water, done..... if my inverters could work with lithiums, i would just for more ease of use, space savings, etc, but hey these FLA's sure work well, totally off grid and fully charged by 11am most days..

I'm with Mike on this. I'm in the market for new batteries and was weighting up my option between Lithium and 2 volt cells. Spoke this week with battery center to get a price on the Raylite ones. "they gave me a good price on 2v cells".  It is expensive if you running a setup like 48v but the cycle life of this batteries are really good and can last years if you keep your hand on them and Ah are super high if you need supply demand. I have 2 family  members that is farming in the middle of the Karoo and they use solar for many years now and are on 2v cells bank.

What nice is about 2v cells is to, if you get a bad battery between 24x2v bank, you can take that battery out and still run on 23 till you replace the bad battery. there is some T'c and S's that go's with that.   

[Gerlach]

But yes, it is possible to run something that size with 12v batteries. This our setup that is running at Bellville Dept with 72 x 12v 230 victron super cycle batteries.

 

 

 

[DeepBass9]

I don't think you will get the same lifetime out of 12V batteries compared to 2V cells. The lifetime on 2V cells should be comparable to lithium if you look after them. @Gerlach, how does the price compare? I would think that for a big bank the price is would be similar for 2v cells or Lithium?

Edited October 31, 2019 by DeepBass9

[Gerlach]

2 hours ago, DeepBass9 said:

I don't think you will get the same lifetime out of 12V batteries compared to 2V cells. The lifetime on 2V cells should be comparable to lithium if you look after them. @Gerlach, how does the price compare? I would think that for a big bank the price is would be similar for 2v cells or Lithium?

@DeepBass9 oooo yes, i'm definitely with you on that one with 12v lifespan compare to 2v cells. 

I got a price on the 3mil15s that is there starting range. It's 530amps per 2 v cell and in it's container "3 of the cells that give's you 6v" will be R10887 with all the cables and stuff that give with it. You need 8 of this containers cells so it will be R87096 . 

Like they state there, expecting life span of 5 years but can be more, and i have seen where they can last really long if you keep a hand on them. 

The one's Mike is using is the 2MLT25s "you can correct me there Mike if i'm wrong", they are 2x2v cells in a container and they are 1050 amps per cell. That's a lot of amps and KW :1050 x 48 / 1000 = 50.4kw

Yes, in know you need to work cycle life and all that stuff but are you going to use all 50.4kw  "25.2kw say if you need to split it in half for the 50% part", who is going to use all that power in the night in one shot if you run your home setup in the right condition/setup. 

[Farai]

Thank you for all your assistance. I will try get the 2v batteries.

How would I keep such a bank balanced? 

[Mike]

6 hours ago, Gerlach said:

The one's Mike is using is the 2MLT25s "you can correct me there Mike if i'm wrong", they are 2x2v cells in a container and they are 1050 amps per cell. That's a lot of amps and KW :1050 x 48 / 1000 = 50.4kw

Yes, in know you need to work cycle life and all that stuff but are you going to use all 50.4kw  "25.2kw say if you need to split it in half for the 50% part", who is going to use all that power in the night in one shot if you run your home setup in the right condition/setup. 

 

you are spot on, on one occasion over a three day bad period i used 497ah, deepest ever, on average in the am, they sit at 87% to 92% charge still and by 10-11am on sunny days, fully charged. they were a blessing to me being off grid and just before lithiums became available albei at a higher price

[KLEVA]

@Farai - If you can, try get 2V batteries that can deliver 3000Ah in a single series string, then there is no need to use balancer.

[phil.g00]

1 hour ago, KLEVA said:

If you can, try get 2V batteries that can deliver 3000Ah in a single series string, then there is no need to use balancer.

I am not sure if there are balancers that go as low as a 2V discrete measurement.

Although overlapping balancers at 4V will probably work.

I can't see how any of the principles that apply at higher voltages to balancing, suddenly don't apply at 2 V though.

 

[KLEVA]

@phil.g00 - The HA02 does go down that low (to 1.5V if I remember correctly). @Chris Hobson, can you confirm?

But anyway balancing on single series string is not ness.

Edited November 11, 2019 by KLEVA

[phil.g00]

@KLEVA My recollection is a 2.4V minimum for the HA02's , but according to @plonkster  the Victron balancers apparently work passively (using resistors, I don't know the specifics), so probably work at any voltage.

I don't know why you say balancing is not needed on a single string.?

Balancing is about equalizing intra-string differences not inter-string, parallel strings will be at the same overall voltages.

 

Edited November 11, 2019 by phil.g00

[___]

1 hour ago, phil.g00 said:

Victron balancers apparently work passively (using resistors, I don't know the specifics), so probably work at any voltage.

Correct. Once the voltage rises above 27.3V (for the pair) the balancer starts to make sure that each side is at roughly half, otherwise it shunts some current past it. So it is limited to 12V batteries and/or 6-cell groups. An HA02 can technically be connected across cell pairs, I don't know if anyone has actually deployed them like that in practice.

My honest opinion of the HA02... I feel a tiny bit distrustful of them. Mostly because we had one member here who lost batteries despite having the balancer on them (making me wonder if they can really do the advertised 2A), and another member who lost the smoke in the balancer itself

I would still like to test one some time. In fact, now is not a bad time. I have 4 x 200Ah batteries standing outside on a pallet...

[phil.g00]

2 minutes ago, plonkster said:

My honest opinion of the HA02... I feel a tiny bit distrustful of them.

I hooked up little voltmeters to give me a visual clue that they were doing anything at all.

My young nephew says they make a high-pitched whining noise, ...I honestly can't hear a thing.

They are apparently working, according to the voltages.

9 minutes ago, plonkster said:

An HA02 can technically be connected across cell pairs, I don't know if anyone has actually deployed them like that in practice.

I vaguely recall someone on the forum has.

[DeepBass9]

I use them across cell pairs. I use 2 on my 6V batteries, one across all of the 12V pairs, an one on one of the 6V batteries in a 12V pair.

When the batteries are out of balance they make a high pitched noise, especially when first connected until things have settled down.

[___]

15 hours ago, DeepBass9 said:

high pitched noise

That's the noise of the DC-DC converter. OK, so they do work at least

I've also wondered about my ability to hear the high pitched noise. Supposedly, as you age, you lose the ability to hear such high frequencies. But one of my colleagues explained it to me: Modern SMPSes have fancy new capabilities like skipping cycles and such, to improve performance even further. This means there is a "skipping" frequency "modulated" on top of the >20khz switching frequency, and this might be what you're hearing.

I have a cell phone charger that is silent when the phone is plugged in, but starts hissing (that is what it sounds like) when you unplug the phone and it goes into a no-load situation. I can hear the PSU of my laptop "tick" as well.

[KLEVA]

I dont have access to a decent drawing tool on my Tablet so have to describe:
8 x 200Ah 12V Lead Crystals in 2 Parallel strings, each 48V (Batt 1-4;Batt 5-8)
2 x HA02 units (HA1;HA2)

HA1 connects to Batt 1,3,5,7
HA2 connects to Batt 2,4,6,8

Note1: This is not the standard, normally you would connect HA1 to Batt 1-4 and HA2 to Batt 5-8, but I like the idea of small balancimg across the banks.
Note2: I swap batteries around in my bank every 1-2 months, so different balancing on different HA's and different banks.

To answer the single string suggestion:
Yes of course you can use balancers on a single string,, but it is paralell strings that get out of balance easily, and it is usually easy to figure out a problem battery on a single string. A single string would show problems before major issues occur, and the parallel charging/usage would mask. Hence the main reason why many say its not ness.

 

[DeepBass9]

You can use 1x HA02 on parallel strings, you must just have interconnections between the strings as well.