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# Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

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## Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
Hi,
we are replacing an old 30KVAh UPS system for an offshore oil installation. We have been given options of:
- Lithium Iron Phosphate (LiFePO4) Batteries; as well as
- Valve Regulated Lead Acid Batteries - maintenance free (the same as existing ones)
I am aware of the advantages of the LiFePO4 (as published online or on paper) but would like to know first hand experiences using them or probably the reason one has decided not to use them!

My concerns about LiFePO4 batteries would be:

1- Any special charging requirements. Will a typical industrial UPS (e.g. Cutler Hammer, Gutor, APM, etc.)
2- Safety and reliability. I know they are much more reliable than Lithium Ion batteries but will they be more reliable than Lead Acid batteries? In particular a risk of fire cannot be tolerated in our application.

Appreciate if you could share your experiences and thoughts on this.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

I wouldn't pick VRLA for a critical UPS battery. I'm sorry I can't comment on LiPo's in this application.

Any reason why you've disregarded the flooded cell technologies? The newer recombination cells require less frequent topping up than plain vented cells, but retain most of the benefits of reliability and long life and have low rates of hydrogen evolution.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

I gotta disagree with Scotty on this one.
We use VLRA batteries exclusively with UPSs. They work great with no complaints. Use quality ones of course, Trojan or something similar. Stay far away from Interstate.

I would use flooded only on a huge application like substations or power plants. Skip all the equalizing hassles and electrolyte spills and thrills the end result being shortened lifespan unless there's someone actually tasked with battery maintenance.

As for LiFePO4 there's no question they're good batteries. Safest of the Li family. They cost a hefty premium over VLRA batteries. They have a whole lot more discharge cycles in them but in an emergency UPS is that even a factor? How many times in 5 years does the UPS dip below 50% battery capacity? Once? Never? If you use the UPS frequently then I'd use LiFePO4. If you use it only in emergencies, rarely, I'd stick with the VLRA.

Do keep in mind that you'd want the fast discharge LiFePO4 variety for UPS service as compared to the slow discharge variety.

Yes, you'd want a new charger that is LiFePO4 savvy. Also remember that you can total LiFePO4 batteries by over-discharging them once whereas VLRA batteries hate being discharged too much too, but short of loosing some capacity will still function. You need to make sure the UPS cuts-off with LiFePO4 at somewhere above 2.5V/cell.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

For various reasons, all of the batteries that I'd seen in DC Telecoms (i.e. -48V) backup applications in recent years had been Lead Acid AGM batteries. I wouldn't have a problem in using AGMs in similar backup applications. I believe that a fair amount of the substation backup batteries were also AGM, flooded cells were not that common.

There is obviously the caveat (although it applies to flooded as well) that up to a certain size, typical makes of UPS units are not nice to batteries. All the DC Telecoms stuff I saw generally included a low voltage cut out, but were also sized to allow an appropriate amount of backup prior to cutting the batteries off. I don't know if the equivalent UPS gear has similar provisions.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
Thanks Scotty and Freddy.
@itsmoked Keith,thanks heaps for your concise and to the point reply. I really liked it.
Cost is not much of a problem (Odd,I know!), and space is limited, so Watt per cubic inch matters.
Site preference is to have single string of lower voltage, say 120vdc rather than something like 400vdc.
The discharge would be at rare scenario of platform blackout and we need the well-head controls powered for 6 to 10 hrs.
My heart is still with good old lead acid batteries, yet kind of open to newer technologies such as LiFePO4 batteries, should they not add to the risk.
I was looking into deep cycle AGM batteries in particular.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Hi Keith,

My experience with good quality VRLA's (Yuasa brand) on a UPS application saw about three years life before we started seeing weak cells in the string. Plante cells usually survive 10+ years, and flooded Nicad's should see 25+ years. If you maintain them then flooded cells will outlast VRLA, but there's a maintenance cost and labour overhead to look after them.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

I am aware of at least one maritime installation where LiFePO4 were chosen over the previous traction lead acid batteries due to weight and capacity issues. As far as I'm aware they haven't had any significant issues with them, although that was a 24V system, rather than 400V.

Having said that, that same installation used to regularly kill AGM batteries due to overcharging, which is how they ended up with traction batteries.

In your application I'd be checking with both the battery manufacturer and the UPS manufacturer for reassurances on compatibility before considering Lithium.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

LiFePO4 batteries are appearing in aircraft, especially in helicopters where weight is a premium. These batteries have built-in all the charge and discharge protection circuits needed for the cells, including short-circuit protections. These batteries are currently 28V (same as what is called 24V for trucks and marine). In addition to weight and size savings, LiFePO4 have very low internal impedance which means piston engines and turbine engines start faster from these batteries as compared to lead-acid.

The next step for LiFePO4 in aircraft will probably be a 270VDC battery system to follow what Boeing did for the electrical distribution in the Dreamliner. The Dreamliner still uses 28V batteries to start the engines or APU, but the chemistry of this battery is lithium-cobalt.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Howdy Scotty! I totally agree with that.

However I'm talking bigger than Yuasa's I ever see.

VRLA AGMs
Like this.

And, as Freddy points out no battery will last if charged by uncaring doofuses. The charging must be prefect or you're wasting boatloads of money.

Instrument1352; If you really are looking to reduce space than you probably should consider LiFePO4.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

These are the biggest VRLA's I've seen - over 3000AH at the C10 rate. https://www.hoppecke.com/fileadmin/Redakteur/Hoppe...

I'd still pick flooded cells over VRLA, but I agree that incorrect charging and poor maintenance will ruin even the best cells.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Those are pretty dang large Scotty!

I have just the chargers for them too! Here's a shot of five of the nine 1,200amp chargers.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

The fault current from the battery banks in those installations can get somewhat concerning.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Yeah, big batteries are scary - they can throw an awful lot of energy into a fault with nothing able to interrupt the current.

Keith - that's a lot of rectifier capacity!

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Place had six battery banks in a basketball size room. They were about 15feet by 8 feet banks. I noticed yesterday that they'd been cabled up to two busbars that are 4" x 1/2".

Random ground cable hanging from the ceiling:

Was going to connect to this bus bar before job went still-born.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
@itsmoked @Scotty
Thanks for your insight. We selected VRLA batteries. Now there is a second question.

Is there a concern if we split the batteries into two parallel battery strings, each with it's own circuit breaker / isolator?
Both will be connected with a common cable to the UPS.

I'm thinking of the advsbtages, such as easier testing, easier maintenance, probably a short circuit in a single string or when one battery in one string becomes faulty and open circuit will not make the whole system fail. That is more availability, reliability and easier maintenance.

I'm concerned if there is a draw back, e.g. if the charging is not balanced between the two strings and the UPS may not even know about it. Or probably any other drawback.

The whole battery bank will have a capacity of about 250KVAh.

Appreciate if you could share your thoughts on this.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Ah.. the bean counters got wind of LiFePO4 pricing I see.

Questions:
What are the string voltages going to be?

Can you use two chargers?

What would your scheme be to utilize both banks?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
Partially the price and the other is the UPS supplier didn't support this and also lacking other approvals we need in place for offshore use.
The battery string voltage is 120v, single charger and we need both battery strings to have the desired autonomy time. I'm thinking if we lose one string only the autonomy tone will reduce.

The other concern is if the voltage of two strings differ, even slightly, one will take all the charging current and the other one will not be charged and then when we need them both, will not have enough charge.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Dual strings are fairly common so one bad cell doesn't take down the entire battery. Just don't mix cell types between the strings.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Scotty how do they solve the riddle of one drained string and trying to switch to the remaining string. They can't ever be connected as the charged one will uncontrollably discharge into the drained one. You can't switch between strings without interruption.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
Great point Keith,

Other than this, say on the day one, when we want to connect the two strings in parallel; if the two string have a slight voltage difference (which is very likely), there will be a considerable current from one to the other(uncontrolled as you mentioned). That would be also a concern when one string has been replaced for a maintenance and wants to be parallel again.
I am not sure, but do you think a dummy load resistor could help? First the two will be connected via a load resistor and after a while, when the voltages are closer and the current through the load resistor has dropped below a certain valve, then it can be shunt via the tie-in/coupler circuit breaker.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

A resistor will indeed control the current limiting it. But that would still be a waste of energy. I suppose you could run on one bank until you've depleted it then switch in the resistor as you switch banks then open the resistor so you never interrupt the battery power to the UPS.

I'd just diode AND the two battery strings together. This would have them both always ON line. Nothing needs to switch, nothing to fail. They would be completely unable to cross charge each other. Both would drain uniformly into the UPS. If one happens to have a higher potential than the other it will win the ANDing and be the supplier until the two banks come into parity then it they both will provide about the same as they both slowly discharge.

Diode ANDing is what's used for redundant power supplies in critical systems because a diode is so simple as to be much more dependable than any other possible scheme.

I would use two separate chargers since chargers are capable of screwing things up rather easily you don't want one screwing up BOTH banks. Also two can be wired so if one chokes (and they do!) the other could be pressed into charging both banks alternatingly while servicing the failed charger.

Question is how much current will your UPS demand from a 120Vdc source?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

(OP)
Using the diode will have the challenge of charging as we have a single charger only. We have two strings of 120V and the continuous current will be about 150A per string. (120*150*2*0.85=30KW with an assumed UPS efficiency of 0.85)

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

So far every dual-string application I've come across has simply paralleled two identical strings. I agree that if they're in a significantly different state of charge then things could get exciting. In that case I would probably separately charge each string fully prior to paralleling. The UPS can be put to bypass for the brief period for changeover.

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Simply string paralleling is just SO lame it astounds me. Anything shorts a cell in one string and besides that string dropping, the other string is dragged down blowing charge into the problem. Absolutely a pointless waste!

I had a parallel stack, one cell shorted in one bank the other bank dumped into the partially shorted one and the charger tried to bring up the 'dead battery' and in 5 minutes the string with a shorted cell in it was boiling furiously with steam, hydrogen, and oxygen pouring out of it. You could hear it boiling from a distance. The battery case was blazing hot. It was frankly... terrifying.

So, put in a fortune of batteries to keep a critical system up, skip the $100 diodes because we're too cheap to use two chargers as you should. You've just lowered the system reliability by 50%. You might as well directly parallel all the batteries. Don't separate them into strings. Don't forget the fuses. Keith Cress kcress - http://www.flaminsystems.com ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration Yes, the strings are fused separately in case of a major fault - should really have said that. Most VRLA failures I've seen have been high resistance or thermal runaway (melted casing) - haven't in person seen one go short yet. ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration All the big charging applications I've come across use modular charger units and a communications medium for the modules. Effectively its a single big charger, but they've all had some level of redundancy in terms of charging modules and failure modes. I'd have to trawl through my records as to how they managed different strings paralleled together but its certainly possible. LEM among others sell string monitoring equipment, so its then possible to identify the failed string (or cell, depending on how its done) and then drop the offending string. It does require rated DC contactors or breakers though. ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration (OP) Keith, I do understand the potential issues and fully agree with the catastrophic failures you suggested. I have used modular chargers before (as Freddy has suggested), but in this case we have a UPS with single charger and single inverter. I am trying to figure out how to use diodes to fix the problem, however I struggle to understand how that might work with single charger. The terminals to charge the batteries (from the charger) are the same as those to use the batteries (to the inverter). Could you please explain how the diodes can be used? Thanks ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration Ah.. I see your problem. That makes it more complex. It can still be done but the complexity reduces the reliability. With that handicap I recommend you simply parallel each battery to its neighbor. I use a fuse between each paralleled battery so if one shorts a cell it gets disconnected leaving all the rest of the batteries intact. Keith Cress kcress - http://www.flaminsystems.com ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration (OP) Thank you very much! I believe that is the most practical option now. I will put fully rated circuit breakers instead of fuses. Cheers ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration Breakers can work but personally I'd not use them in this case only. Breakers tend to cost way more in DC breaker land than fuses. They often are a little more difficult to mount and wire then fuses in battery settings, possibly increasing cable run lengths, that are always detrimental in battery systems. Example comparisons When you use anything for interruption you need to check what the available fault current maximum is. With big batteries it's not hard to end up with a breaker that can't actually interrupt the available fault current. The last system I did I wanted to be able to cut out a battery. They were ALL paralleled so cutting one out didn't do anything other cut out UPS time. Turned out I could use beakers for each of the batteries but there were no breakers that could disconnect them all at once from the UPS since the fault current was astronomical. I used a fuse instead. Keith Cress kcress - http://www.flaminsystems.com ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration (OP) Thanks again to all of you who contributed to my query. Special thanks to Keith and Scotty. I ended up using an N+1 (in this case N=1) redundant UPS with one common bypass, two supply feeders, two rectifiers, two inverters, two battery banks each with their own cables and DC breakers with shunt trip and one common output side bus. During the normal operation each will have 50% of the load. In case one set fails the other will take over 100% of the load. At any time each one of the UPS can be isolated and worked on (with work procedure and LOTO of course). ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration Inst; Thanks so much for coming back! We appreciate it probably more than you know. Do tell: How is one battery bank detected to have failed and what switches it out? Any chance you have a sketch? Keith Cress kcress - http://www.flaminsystems.com ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration Thanks for the feedback, pleased you got a workable solution. ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration (OP) Hi Keith & Scott, Here is a sketch I made for you: I did not sketch the full UPS side as it is a standard N+1 topology as I explained in my previous post. If we loose independent side e.g. a battery string, say faulty cell, or one inverter, etc. the other UPS will still provide the supply, albeit with reduced autonomy time. From the charging profile, the UPS will pick if the battery is faulty. The circuit breaker in the battery room will also provide some protection against a short circuit of part of the string to chassis. Also it breaks the string into 120V segments which makes it easier in certain fault cases also makes working on batteries easier. Cheers, Hammet ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration OK Thanks! Yeah! I get my two battery chargers! Keith Cress kcress - http://www.flaminsystems.com ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration (OP) Yes, I listen to more experienced guys sometimes! ### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration An interesting couple of follow-ups: Remember these things I put up in ~3 threads? thread238-448323: Yanking a transfer switch. They finished scrapping out the copper from this battery backed server farm and told me about the results yesterday. The 1.5MW Cat Generator was removed. It took a 240 ton crane and a second semi loaded with weights to lift it to a low-boy. The copper included the cable above and much more. 22,000 pounds of busbar alone. Total of$82,000 in scrap copper and transformer iron.
I had no idea. Too bad I didn't get a cut.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

Copper prices must have come down a bit; there was a while when people were breaking into houses to steal the house wiring.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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### RE: Lithium Iron Phosphate (LiFePO4) vs Lead Acid Batteries - Industrial Application & Consideration

I was told $2.20/pound for pure copper like the bus bar. Then there are two discounters. Thick insulation and thin insulation. The cable shown above on the floor reduces the$2.20 down to 90% and the green stuff with much thicker insulation down to 82%.

Keith Cress
kcress - http://www.flaminsystems.com

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