Pb-C - Lead Carbon cells vs Lifepo4

Aussie_Dude

New Member
Hi all, there doesn't seem to have been any lively discussion, about Pb-C (Lead Carbon) battery technology.

To Will Prowse::) Pb-C comparison tests please!

I'm putting together a system for my home, and I'm quite impressed with the look of Pb-C especially when comparing to LifePo4 batteries prices.
I would be interested to see similar tests and/or comparisons done on Pb-C as has been done on LifePo4 batteries.
With both technologies being capable of many thousands of cycles, and no need for BMS on Pb-C, what am I missing?
The Pb-C batteries are heavier, but that is not an issue for a static installation.

If anyone has experience with this technology, please comment.

Do you need to Balance cells? if so what procedures?

Cheers from Down Under
Sydney, Australia
 
Last edited:

fratermus

Solar Enthusiast
I think carbon (firefly, etc) got betamaxed by LFP. Similar performance, similar $/kAh over their lifetime. LFP won the horse race, I think, with much wider production and falling prices.

There's a decent amount of talk about carbon-Pb on the marine/sailing forums where the technology has found more of a foothold.

what am I missing?

Carbon is also not affected by the "no charging below freezing" issue.


Tangent: After the big Firefly noise a few years ago Trojan and some others are doping with carbon in their solar ("RE") series; the addition is claimed to make them better in PSOC operation, resulting in +15% cycles. Since the cost premium is greater than the +15% increase I won't be buying any.
 

Substrate

Solar Addict
Balancing those cells? Follow standard procedure for ANY lead acid battery:

It is best to give ANY lead-acid battery an individual full charge before assembling into a bank. This ensures that not only are individual bank batteries relatively balanced in regards to each other starting out, but also cells INSIDE each battery, especially when first received. Unlike LFP, this is a natural process of any sealed vrla when reaching the absorb stage and recombining. LFP doesn't recombine so other steps are taken.

I've seen this "needs no balancer" sales-schtick bullet-point in other lead-chemistries too, which are threatened by LFP, grabbing at straws.

The worst thing these marketing bullet-points do, is leave the uninformed with the idea that you can just slap things together with total disregard, and then needing rescue from deep in the outback.

Also note that PB-C does not mean absolute freedom from never obtaining a full charge. You are not advised to use permanent PSOC style operations without doing a proper power-budget calculation first.
 
Last edited:

SolarForU2

New Member
WE have been using a smaller 24v bank of PB-C 6v cells for the past 2 years as in interim solution prior to installation of a larger 40KW bank same batteries. I also have a 45Kw bank of 400AH Lifepo4 cells in another system.

The PB-C bank is no where as efficient as the LifePo4 setup, the PB-C system essentially performs same as all Lead batteries, fast to charge to 85% then takes forever to get to 100%, suffers from high voltage drop on heavy loads and being sealed have limited max charge rate. They don't suffer as high a self discharge as other Lead types, but they are still lead and only 85% efficient, unlike Lifepo4's 95-98%. They have to be fully charged at least once per month, which may mean running a generator in winter. Lifepo4 couldnt care less what state of charge its left in for day to day use.
The PB-C cells will not need balancer's if initially new and setup correctly from the get go.

To setup a bank, wire all cells in parallel and setup an accurate digital current limit power supply and charge to the correct end point voltage, then series up the batteries as required; note this is exactly same procedure as Lifepo4.

The Lifepo4 bank is brilliant, can accept huge amounts of charge current, charges to 95% very quickly to 3.47 volts per cell, we stop charge there and switch to a lower voltage of 3.35 volts per cell, then as loads on the system drop the cell voltage, if there is enough sun all load power comes from the PV array. You will require an active balance system with feedback to the charger, that trips in at the 3.45 - 3.47 volt mark and has at least 5-10 amp cell load capability.

I would never install another PB of any sort bank, unless you can get the batteries cheap..

Cheers
Mike
 

Steve777

New Member
I think quite a bit depends upon the nature of your system (grid tied or off-grid; and stationary or mobile).

For off-grid, I think that LiFePO4 is worth the extra cost because it handles partial discharges better and as SolarForU2 mentioned is more flexible in how it can be charged (although the industrial Pb-C batts can handle a lot of charge current). For grid-tied, where the batts will be kept in float most all of the time, I am not sure the LiFePO4's advantages come into play much, if at all; and I think it is worthwhile to put the lower cost Pb-C's into a larger bank (or just save some bucks). And of course for mobile setups, the weight advantage of Li (as well as it likely being an off grid setup) heavily biases to Li.

I recently replaced my aging AGM bank in my stationary grid tied system, and opt'ed for Pb-C. Mostly because the life expectancy of the two were comparable (probably a bit better for Pb-C in the case where the batts were rarely drawn down), and I stumbled upon a great deal on some industrial Pb-C batts. Too soon to say whether this will turn out to be the right choice or not, but from the spec sheets I think it was the right way to go.

Although I would agree, would be nice to see some detailed side by side comparisons of the two chemistries.
 

SolarForU2

New Member
I would agree with Steve777, those 2 volt LD-C batteries are very robust and can handle a lot of charge current, with a long life.

We are using 3 parallel 48 volt strings of the 6 volt 300AH LD-C batteries, each with their own 60 amp PV charger, would have liked to have used the 2 volt ones but would have cost a lot more; so now limited to 180 amps max charge current and the longer re-charge time.
Unfortunately LIfePo4 would have cost more again, so opted for the lead batteries and a bigger PV array.

Repeating the exercise I would opt for a smaller LifePo4 bank and a bigger PV setup as a better option, for NZ climate anyway.

Mike
 

wholybee

Solar Addict
The lead carbon are basically an AGM with the benefit of not loosing capacity from sulfation. However, in order to achieve this, they need to be charged at a relatively high rate (0.4C) from a low state of charge weekly, with an occasional "refresh" charge similar to an equalization charge. That is recommended practice with most Pb batteries, it is just more effective with lead carbon. In most other respects, they are the same as an AGM.

From the manual:

"Periodic Fast & Complete Charge Cycle Recommendations: Note that periodic fast (high current) charging from a low state of charge can help restore usable capacity after periods of repeated slow charging (less than 0.2C) or deep discharge cycles. It is recommended that the battery goes through a complete charge cycle from a low state of charge every week if they are being heavily cycled or at minimum every 30 days. Ideally the batteries will be charged at a current of 0.4C (46 Amps for an Oasis G31) but a minimum of 0.2C (25A per G31 battery) is acceptable. For applications lacking fast charging capability, contact OPE or for alternative restoration procedures."

and:

"As stated, Firefly Batteries can operate in a partial state of charge for long periods of time without sustaining any permanent damage. The usable capacity will decrease, however, with each cycle within a partial state of charge, up to a point. In order to regain the full original capacity and in some cases more, it is necessary to perform a restoration charge. To perform the restoration charge: charge the G31 to 14.4V or the 4V/450AH to 4.8V and continue to charge until the current drops to 0.5 A on the G31 or 3A on a 4V/450AH. Fully discharge the battery to 10.5V (G31) or 3.5V (4V/450AH), and then repeat the same charge cycle."

So if you are considering them, make sure you are able to meet those charging requirements. Solar might not be able to charge at the 0.4C rate, and you might run out of daylight before a restoration charge is done.

 

Substrate

Solar Addict
I would say it would be ludicrous to even consider them for solar, except as a lark, or perhaps someone gave you one that is already knackered.

Look at all those maintenance requirements! LFP has none of that.

Leave Pb-C to it's primary application: Start / Stop vehicles. There, the psoc type of operation can be a help since nobody maintains their vehicle battery.

And for solar? No way. Essentially you'd be paying more than a cheaper conventional agm for a psoc feature you ideally won't use.

That's the true beauty of LFP: none of these chess-playing tactics to maintain your lead-based battery is needed. For amateurs, or those who are just tired of being wedded to maintenance, LFP is a real boon.

I guess the summary of the thread title could be answered "There is no comparison, because LFP doesn't sulfate" - which relieves one of all these specialized maintenance headaches needed with lead-based batteries. And that's just for starters! (no pun intended) :)
 
Top