AGM Batteries

[Martinb]

Happy New Year All!

 

We are in the process of looking to replace 3 leisure batteries and are considering AGM batteries.   We currently have 120AH leisure's which are no longer holding their charge.

 

We have shoreline when not out and about but also in addition run solar 200w in total.

 

As always the standard google searches provide a wealth (or not) of suggestions and the more you look the more confusing it becomes.  I am therefore looking for suggestions as to a good AGM battery to meet our needs that doesn't cost the earth. (ideally)

 

Thanks in advance

Martin

[Alan de Enfield]

How long have your existing batteries lasted ?

 

 

[Martinb]

Appx 3 years max.  Sadly we were incorrectly advised on charger settings and they have slowly been ruined over the last few years.

[Briss]

Without wishing to sound patronising, this is a very good read to help you get the most out of your new batteries. You may have already seen it.

 

Battery charging primer: 

 

[Alan de Enfield]

But now you know what charger settings to use you'll get (maybe) 5 years.

 

3x £100 for FLA = £2/week over 3 years (less than a cup of coffee) or £1.15 per week over 5 years.

 

Personally (other opinions are available) with your set up of mains and solar they are not going to get over discharged and I'd just go for FLA.

Edited January 4, 2022 by Alan de Enfield

[Martinb]

Thanks, worth a thought.   I was suggested AGMs as they are better at discharging and general maintenance?

10 minutes ago, Briss said:

Without wishing to sound patronising, this is a very good read to help you get the most out of your new batteries. You may have already seen it.

 

Battery charging primer: 

 

Thanks will take a read through

[Tony Brooks]

25 minutes ago, Martinb said:

Thanks, worth a thought.   I was suggested AGMs as they are better at discharging and general maintenance?

Thanks will take a read through

 

Starved electrolyte batteries like AGMs are supposed to have a slightly better high discharge current performance and possibly recharge but I doubt either is significant enough to make s significant difference. As long as you get lead calcium plates then flooded LAs are unlikely to need much topping up at all  and are easy to test by hydrometer. that will show fault cells and when compared with inferred state of charge from rested voltage will give a fair idea about the degree of sulphonation.  Lead Antinomy flooded LAs are likely to need more frequent topping up with modern alternator charging voltages but they can be equalised. It would be  foolish to try to equalise an AGM because you can not top up the water that will be driven off by the higher voltage.

 

AGMs should be more resistant to plate shedding and the resultant cell shorts but pocketed plates in a flooded cell LA battery will give a similar advantage.

 

Flooded calcium LAs for me because they are far easier to diagnose.

[Martinb]

thanks for all the comments, more food for thought.

[cuthound]

My boat is now 14 years old and was fitted with Lifeline AGM's from new.

 

These are quality AGM's which can be equalised. They still have over 50% of their original capacity left.

 

However there is one problem, the cost is eyewatering, the domestic battery (4 x 6 volt 225Ah batteries in series/parallel) will cost over £1600 to replace.

 

When they eventually need replacement I will have to see what is available. It might be cheaper to fit Lithium's.

[Up-Side-Down]

I would investigate:

 

1) Lead Carbon batteries

2) Victron Super Cycle AGMs which can accommodate 100% DOD, albeit with a reduced life cycle: https://www.victronenergy.com/batteries/gel-and-agm-batteries (see the Super Cycle pdf at the bottom of the page)

 

More expensive to purchase but whole life cost works out considerably cheaper.

[nicknorman]

I think AGM is a good idea if you want to stick with lead acid batteries. They get used a lot in cars these days, mainly because of the resistance to sulphation as modern cars don't fully charge their batteries (to leave space for regenerative braking). Resistance to sulphation has to be a good idea for domestic boat batteries!

But I think there is a wide variation in quality of AGM and unforunately, as usual you tend to get what you pay for.

 

18 hours ago, cuthound said:

My boat is now 14 years old and was fitted with Lifeline AGM's from new.

 

These are quality AGM's which can be equalised. They still have over 50% of their original capacity left.

 

However there is one problem, the cost is eyewatering, the domestic battery (4 x 6 volt 225Ah batteries in series/parallel) will cost over £1600 to replace.

 

When they eventually need replacement I will have to see what is available. It might be cheaper to fit Lithium's.

It would be cheaper to fit lithiums! 600Ah at 12v cost about the same (although as you know, you would need a BMS and modified charging arrangements as well). You could have 400Ah, which would give much more usable energy than your 450Ah of lead acid, for £1k or so.

Edited January 5, 2022 by nicknorman

[Up-Side-Down]

400Ah of lithiums for £1k or so: where please?

 

[nicknorman]

22 minutes ago, Up-Side-Down said:

400Ah of lithiums for £1k or so: where please?

 

These are the ones I bought 

https://blslifepo4battery.com/collections/3-2v-batteries/products/grade-a-calb-3-2v-200ah-lifepo4-rechargeable-batteries 

which admittedly would be £1160, but you could also get these ones https://blslifepo4battery.com/collections/3-2v-batteries/products/3-2v-200ah-lifepo4-battery?variant=32511661604944

for around £900. Of course this is just for the bare cells, you need to know what you are doing with regard to a BMS and charging.

[Up-Side-Down]

Thanks Nick.

[CanalRetentive]

26 minutes ago, nicknorman said:

These are the ones I bought 

https://blslifepo4battery.com/collections/3-2v-batteries/products/grade-a-calb-3-2v-200ah-lifepo4-rechargeable-batteries 

which admittedly would be £1160, but you could also get these ones https://blslifepo4battery.com/collections/3-2v-batteries/products/3-2v-200ah-lifepo4-battery?variant=32511661604944

for around £900. Of course this is just for the bare cells, you need to know what you are doing with regard to a BMS and charging.

 

What makes one set more expensive than the other I had a glance and the specs look similar? Can you recommend a good BMS for them? I'm still in the research phase but definitely going for lithium upgrade soon as seems far easier than trying to convince the other half we live on a boat and not in battersea power station. 😂

[nicknorman]

25 minutes ago, CanalRetentive said:

 

What makes one set more expensive than the other I had a glance and the specs look similar? Can you recommend a good BMS for them? I'm still in the research phase but definitely going for lithium upgrade soon as seems far easier than trying to convince the other half we live on a boat and not in battersea power station. 😂

Yea good question! I think it’s mostly just a supply and demand thing. I went for the CALB type cells because the casing seems more robust. No need to strap them all together. The other type seems to have a thinner aluminium case which looks more prone to swelling. In my totally unqualified opinion! The guts are probably much of a muchness and even if one is a bit better quality /longer lasting, they last so long anyway that it probably doesn’t matter.

 

I designed my own BMS so no experience of a commercial one, but the REC BMSs seem popular. There is a mahoosive thread about BMSs on here, if you have a few spare weeks to read through it! Alternatively I would recommend getting in touch with Ed Shiers at four counties marine, he knows his stuff. https://fourcountiesmarineservices.com/lithium-batteries/

As to Battersea power station, I am still struggling to use enough power to justify the 600Ah we got. Electric kettle, washing machine, immersion heater etc are failing to challenge them!

Edited January 5, 2022 by nicknorman

[cuthound]

1 hour ago, nicknorman said:

I think AGM is a good idea if you want to stick with lead acid batteries. They get used a lot in cars these days, mainly because of the resistance to sulphation as modern cars don't fully charge their batteries (to leave space for regenerative braking). Resistance to sulphation has to be a good idea for domestic boat batteries!

But I think there is a wide variation in quality of AGM and unforunately, as usual you tend to get what you pay for.

 

It would be cheaper to fit lithiums! 600Ah at 12v cost about the same (although as you know, you would need a BMS and modified charging arrangements as well). You could have 400Ah, which would give much more usable energy than your 450Ah of lead acid, for £1k or so.

 

What are the dimensions of your lithiums? If they are the same size or smaller, so that they fit in the same battery box, then I will definitely consider them at replacement time.

 

Might need to pick your brains re BMS and alternator mods though. 🤔😄

[nicknorman]

1 minute ago, cuthound said:

 

What are the dimensions of your lithiums? If they are the same size or smaller, so that they fit in the same battery box, then I will definitely consider them at replacement time.

 

Might need to pick your brains re BMS and alternator mods though. 🤔😄

The ones I got are:
(L*W*H):183*72*280mm, 3 x 4 200Ah cells. So quite tall, but a smaller footprint than the 450Ah of Trojans we used to have. And of course 40kg lighter, which can affect the trim of your boat if they are all at one side (which ours were).

 

[cuthound]

Just now, nicknorman said:

The ones I got are:
(L*W*H):183*72*280mm, 3 x 4 200Ah cells. So quite tall, but a smaller footprint than the 450Ah of Trojans we used to have. And of course 40kg lighter, which can affect the trim of your boat if they are all at one side (which ours were).

 

 

Thanks Nick, I'll do some measuring up.

[nicknorman]

12 minutes ago, cuthound said:

 

Thanks Nick, I'll do some measuring up.

I think for most people, 400Ah would be enough, ie 2 x 4 cells.

[cuthound]

5 minutes ago, nicknorman said:

I think for most people, 400Ah would be enough, ie 2 x 4 cells.

 Indeed, we currently have 450Ah of AGM's fitted, which have lost almost 50% of their original capacity. As we tend to move every day when out on the boat the reduced capacity is adequate, but we can no longer linger for a second day without running the engine.

[nicknorman]

18 minutes ago, cuthound said:

 Indeed, we currently have 450Ah of AGM's fitted, which have lost almost 50% of their original capacity. As we tend to move every day when out on the boat the reduced capacity is adequate, but we can no longer linger for a second day without running the engine.

Well 450Ah not taken down below 50% = 225Ah. 50% of original capacity = 112.5Ah. With 400Ah of Li, you have at least 350Ah of usable, and of course due to the slightly higher voltage 350Ah of Li is worth more than 350Ah of LA in terms of energy.

[Richard10002]

3 hours ago, nicknorman said:

Well 450Ah not taken down below 50% = 225Ah. 50% of original capacity = 112.5Ah. With 400Ah of Li, you have at least 350Ah of usable, and of course due to the slightly higher voltage 350Ah of Li is worth more than 350Ah of LA in terms of energy.

 

I tend to use my Valence Li batteries between about 90% and 20% State of Charge, so only get 70% useage, compared to 50% with my previous Lead Acid bank. Your suggestion seems to leave 12.5% to be shared at the top and bottom of SOC..... 94% to 6% SOC?

[nicknorman]

38 minutes ago, Richard10002 said:

 

I tend to use my Valence Li batteries between about 90% and 20% State of Charge, so only get 70% useage, compared to 50% with my previous Lead Acid bank. Your suggestion seems to leave 12.5% to be shared at the top and bottom of SOC..... 94% to 6% SOC?

Yes. Although if you look at Mr Cuthound’s intended usage it’s not something he would do very often. There has been a lot of talk about 80% to 20% or whatever, but I don’t really buy that and it’s not based on evidence, only opinion. I am more inclined to think that one just keeps off the knees. Once the cell voltage starts to get above say 3.4v (13.6v) you are very close to fully charged, say 97%. And on discharge when the voltage starts to fall rapidly (goes below 3v (12v) you are around 10% or less.

 

And anyway, how can you assess the SoC unless you synchronise the battery monitor from time to time, by charging to 100%? If you are planning to spend a couple of days without running the engine, that is the time to charge to 100% to synchronise the SoC.

 

Peterboat of this parish has supplied information that suggests that Valence batteries have different behaviour in terms of charge voltage vs SoC but I am unable to verify or refute that!

Edited January 5, 2022 by nicknorman

[TheBiscuits]

3 hours ago, nicknorman said:

Peterboat of this parish has supplied information that suggests that Valence batteries have different behaviour in terms of charge voltage vs SoC but I am unable to verify or refute that!

 

I've always suspected he measures the voltage while the active cell balancing is taking place inside the magic black box on his Valances.