We are all aware that in yacht use the Achilles Heel of lead-acid batteries is that only about 50%1 of the rated capacity can be used on a daily basis.
But now Trojan, a well-respected brand, have released their AES AGM Battery with a claimed life of 1200 cycles to 100% discharge. These batteries are also purported to be able to withstand being left in a partial state of charge for long periods, repeatedly.
This is excellent news. And these batteries are already on store shelves….. I’ve seen them listed as low as $435 CAD ($322 USD) for a 105 Ah Group 31. That’s about a 60% premium over a basic white-label flooded-cell 105 Ah Group 31, but with a 50% gain in usable effective capacity, so very nearly the same price per usable amp-hour…. plus all the advantages of AGM over flooded…. and a Trojan is likely to last many more years before replacement versus a no-name brand.
It’s very telling that Trojan went straight to the rental power equipment market (forklifts, skyjacks, etc.) for the initial marketing release of the AES series. That’s a very demanding market, arguably much tougher than our own, and it’s managed by people who keep excellent statistics on their fleets and who come down *hard* on any supplier who can’t meet their reliability and warranty promises. Trojan is, effectively, placing a massive and expensive vote of confidence in their own technology; this is not a limited alpha-product release with uncertain support.
Hi Matt,
That’s a very good point supporting Trojan’s confidence, that I never thought of. Very comforting, thanks.
100% agree, MM. And very good to hear (as someone who lives on 2 x 6V 225Ah Trojans presently!). I will be keeping an eye out for these in our local market, definitely.
Me, too. These sound ideal and would fit our battery box.
Excellent to hear Trojan have such confidence in them.
Very interesting. Do they require the same equalization regimes that most AGM’s do? that was always a bit of an issue with AGM installations I’ve managed in the past. Any installation over about 600 Ah required a lot of intervention (disconnection/switching of banks to bring overall bank size down to a smaller level) to get properly equalized using any reasonably sized charging system/acceptable time frame. Definitely not a hands-free or set-and-forget operation, and has steered me away from AGM’s since. Not equalizing led to premature death.
I wonder what our local FLA/AGM batt expert at Rolls (Surette Batteries) has to say about this… I think I’ll ask him!
Rolls are a major supplier to the same market; and seem to have an excellent reputation as well. I know I’ve been very happy with my batteries (replaced a set of Trojan T105’s); and feels good supporting a local manufacturer.
…I’ll point Pascal to this article and will report back!
Hi Ben,
I’m guessing not, or not often, given that I’m pretty sure that they are using an improved version of the FireFly carbon foam technology that resists sulphating.
Also I’m confused by your concern about the difficulty of equalizing lead acid AGM batteries. We had 800 Amp hours on the McCurdy and Rhodes 56 and could equalize the whole bank with a single 30 amp charger. As I understand it (from LifeLine) equalization should only start when the batteries are fully charged so in our case the whole bank would only be accepting about 16 to 20 amps (~3% capacity) at 15.5 volts at the start of the equalization period and it dropped off from there. We did this once a month for many years without issues and without disconecting.
Note, we did have the bank split in two with separate chargers and a 1-2-both switch, but that was just so we could use one half while the other was equalizing: https://www.morganscloud.com/2010/10/05/equalizing-batteries-the-reality/
All that said, there are AGM battery manafactures who specificaly forbid equalizing, but in my view that disqualifies them from use on a yacht, at least if not carbon foam.
Hey John – yea, I would imagine you’re correct.
On the equalizing – it was a while ago, but I recall two boats i was looking after in particular – one a Little Harbour and the other a Nordhavn, both of which required me disconnecting one half of the banks manually (pulling a jumper on the bank) to bring the capacity down enough to allow the built-in chargers to do the equalization effectively. I don’t recall the specifics of the bank sizes or chargers but it was all relatively good gear, and the batts were Lifelines. That I remember because the well known and respected Jonathan from Lifeline assisted me in troubleshooting and identifying where to pull the jumper. It worked fine when I did that – but it was a bit off-putting!
They were older boats though, with many ‘alterations’ through the years, and if I recall correctly it wasn’t the only odd thing about their systems!
John, that’s a perfect use profile, IMHO.
There is a Quick Start Guide for Trojan AES batteries in the Resources section of the Trojan website. It has this to say about equalization:
EQUALIZING
■ Trojan AES Batteries do not require equalizing.
WARNING: Do not equalize deep-cycle Trojan AES batteries.
Permanent damage to the battery will occur.
Typo?
I’m not doing much boating at 40C. I’m looking for a chilled drink and the shade of a Palm tree.
“Another benefit is that these batteries can be used down to 40°C,”
It should read negative 40°C. That’s the lowest temperature at which Trojan approves these for operation.
Hi Matt,
Oops, thanks. Fixed now.
Interestingly, -40 degrees Celcius/Centigrade is the same as -40 degrees Fahrenheit. The crossing point of very different scales. Anyway, if the battery compartment of our boat reaches minus 40 degrees, I think we have a number of more serious problems than our batteries starting to fail. 🙂
This is looking very good, I was about to pull the trigger for replacing my 10 years old Trojan 27-TMX. The Trojan 27-EAS looks like a real drop in. It is even a bit smaller. I am a bit puzzle by the Group 27 versus Group 31 though. They look about the same beside the terminal configuration.
It is interesting to compare the two batteries.
27TMX – Capacity 20-Hr Rate / 105 Ah WEIGHT LBS. (KG) 55 (25)
27-EAS – Capacity 20-Hr Rate / 102 Ah WEIGHT LBS. (KG) 65 (30)
With Lead-Acid batteries, higher density/capacity generally means more container weight. This has been explained as thicker lead plates used in true deep cycle batteries compared to starter batteries (high cranking amps). What is it about the EAS batteries that increases the weight but does little to the capacity?
Hi John,
Yes, carbon foam batteries do seem to be a bit heavier for a given capacity (same with Victron, only worse) but that’s offset by the increase in usable capacity, at least with the Trojan.
I am glad to see Trojan entering this market (leadcarbon) I have had excellent results with NorthStar NSBblue+, also lead carbon, although I don’t think they claim 100% discharge. They have had field tests at 4000 cycles at 50%. I think PbC batteries are a good choice for most cruisers that rarely spend more than a couple of months at a time in the wild.
Hi Carl,
Thanks for the report on the NorthStar. Great to see others embracing lead/carbon. And I agree, a great solution for that usage profile, as well as many others.
This would appear to be a response to the Victron Super Cycle AGM introduced 2-3 years ago. I installed 3 of them before the 2023 season & a trip from Maine to Newfoundland. Being a coastal sailor, not living aboard & relatively moderate amp draws; a lithium conversion does not seem to make sense.
They have performed well but I cannot say we gave them much of a test as 2023 was rainy, foggy & calm and resulted in a lot of motoring.
They are rated at 125 ah, the Trojan regular AGM’s they replaced were Grp 27 89 ah. The Victrons are slightly smaller than a Grp 31, so we were able to squeeze them in. I left the Trojan Grp 27 for the start battery. The cost in Jan 2023 was $392 ea. inc shipping.
Victron says:
Tests have shown that the Super Cycle battery does withstand at least three hundred 100% DoD cycles.
The tests consist of a daily discharge to 10,8V with I = 0,2C₂₀, followed by approximately two hours rest in discharged condition, and then a
recharge with I = 0,2C₂₀.
The two hours rest period in discharged condition will damage most batteries within 100 cycles, but not the Super Cycle battery.
We recommend the Super Cycle battery for applications where an occasional discharge to 100% DoD, or frequent discharge to 60-80% DoD is
expected.
Smaller and lighter
An additional advantage of the new chemistry is a slightly smaller size and less weight compared to our standard deep cycle AGM batteries.
Low internal resistance
The internal resistance is also slightly lower compared to our standard deep cycle AGM batteries.
Hi David,
Thanks for the report. I too installed the Super Cycle batteries from Victron and so far we are getting great service.
That said, like you, our usage is light.
My guess is that the Trojans, because they are carbon foam based, will do better than the SuperCycles in situations where the batteries are regularly left partially discharged as is common on full time cruising boats. Note that Victron also has a Carbon foam lead acid battery for this usage profile but it does not have as good an energy density as the Trojans.
Hi John, thanks for bringing this to our attention. I’m considering whether to pursue lithium or not and was wondering what changes you would make to your Battery Capacity Calculator to adjust for these Trojan AGM? Thanks.
Hi Kirk,
You can just adjust the lead acid down by about 25%. So, for example, if the calculator yielded 400 amp hours I think it would be safe to install 300 amp hours of these batteries.
Thanks John, thought it was as simple as that but wanted to make sure I didn’t miss something.
Hello John
Interesting to see that the carbon foam technology is not dead.
When the Oasis Firefly came out and especially after Nigel Calder’s glowing recommendation, I bought 8 of them and installed a 48 volt series parallel bank to power the electric propulsion on my 35′ sailboat,. That was 8 years ago and last year one of them was not keeping up with the others . I was recently offered an irresistible offer on a pair of 48 volt LiFePO batteries from Alberta Lithium. (I live on the west coast of Canada). I took out 650 lbs of lead acid batteries and replaced them with 220 lbs. of lithium. What a difference. I recently discharged them down to 20% and they were still delivering 52 volts and they charged up in half the time. No series connections and maintaining 22 amps charging right up until 100% recharge. They don’t need to taper off for the last 20 %.
I intend to buy a third one in the spring and I will still be less than half the weight of the lead acid
Hi Simon ,
Sure, for propulsion I think lithium is now pretty much a no brainer. But that’s way different from the use case when someone has a simple lead acid house system and wants to replace the batteries without any added complication or changes. In that case these batteries are a great option. Horses for courses.