Battery recommendation - anchor windless

[NotCook]

I need to replace my 2 12V batteries, to make 24V, and wanted to see what the current thinking is about the best battery type for this application. Lead acid, AGM, Gel, what? I’d appreciate the rationale behind any recommendation. Thanks.

 

[Foswick]

Lots of follow-up questions. How many amp-hours do you need? Is space limited? Do you need to start your motor with this battery, or is just a house bank? How much continuous and peak output do you need (in amps)? Is initial cost a major consideration (versus long-term cost)?

I think that, these days, it really comes down to one of two choices: AGM or LiFePO4. I can't think of anything that would make any other choice a good recommendation - except in some unusual circumstances.

To my mind, there are only two reasons to choose AGM over LiFePO4, these days:

• Initial cost is more important than life-time cost. (LiFePO4 is more expensive but lasts longer, making it usually a better long-term cost.)
• You need more than about 100 - 200 amps output - like to crank an engine. There are LiFePO4 batteries that are up to the task, but most are not. Those that are can be quite expensive (making it no longer an economical choice, for most).

Why AGM and not a flooded or gel battery? Well, flooded batteries are just too problematic in a boat. About the only thing to recommend them is that their initial cost is the lowest (I think). Gel batteries are a fine choice, for performance, but they are more finicky about charging and need to be charged more carefully. If you are relying on your alternator to charge, a gel battery could be continuously damaged without some additional regulation.

Why LiFePO4 and not some other lithium chemistry? Well, there are other safe/stable chemistries. It is just that LiFePO4 has been the most popular formula, so far, when needing something safer than LiPo (lithium-ion polymer). And, although LiPo is cheaper and denser, it is also generally considered unsafe for use on a boat (for good reasons).

 

[Davidasailor26]

What’s the chemistry and charging arrangement for your other banks? Generally a windlass battery doesn’t need to be discharged much. It just provides some buffer to briefly give more amps than the alternator can provide. Flooded lead acid should be fine for that, especially if your house bank is flooded so you’re already dealing with battery watering. If your house bank isn’t flooded I’d probably get AGM for the windlass bank as a lower maintenance alternative.

 

[Screen Saver]

The short answer is go Lithium. Rational is simple, you get far more useable amps out Lithium and if looked after will last longer. Now days even in Australia which is an expensive country they aren't much more expensive. There are much better places than here to consider the pro's and con's so if your nervus search out some forums specially about Lithium. If you read this Lithium–LifePo4 | Screensaver you will see I broke most of the rules that you will read about. People made all sorts of wild statements, but 4 years on everything is good. I did NOT follow the masses as you will see. Because for me at the time it was to be a learning curve, a test and never meant to become the final thing I was to keep, I bought cheap individual cells and basically threw it together with no other changes to hardware and tried many things that everyone said you cant or shouldn't do. The purist would be quite horrified I guess if I'm honest, but I went for a practical and logical approach and looking for why people had the idea's they did and was this applicable in my case.

 

[dlochner]

LiFePO4 batteries are not typically appropriate for high load devices such as anchor windlasses, starter motors, and bow thruster. The initial current draw of these devices often exceeds the batteries ability to deliver the current without damaging the BMS. It is possible to use LFP, however the battery must be able to handle a max discharge current of 200-300 amps, many can not do that.

 

[Screen Saver]

LiFePO4 batteries are not typically appropriate for high load devices such as anchor windlasses, starter motors, and bow thruster. The initial current draw of these devices often exceeds the batteries ability to deliver the current without damaging the BMS. It is possible to use LFP, however the batter must be able to handle a max discharge current of 200-300 amps, many can not do that.

Mine run all of the above, but it is one of the advantages of building your own configuration of individual cells with ones own BMS, as opposed to a drop in version. It also gives you much more detailed control.

 

[shemandr]

I avoid posting on battery threads because the subject is out of my lane. But I'll add an observation here. Golf carts. My course has replaced the old lead acid carts with lithium carts. They suck. 'though well charged they have no umpf - that's an engineering term - when starting from a stop. Once they go for a bit they build up speed. I've hypothesized that the poor performance at start up is due to whatever lithium technology they use. I think that observation is in line with Dave's statement above.

 

[American_Mainsail]

I need to replace my 2 12V batteries, to make 24V, and wanted to see what the current thinking is about the best battery type for this application. Lead acid, AGM, Gel, what? I’d appreciate the rationale behind any recommendation. Thanks.

What is the make and model of the windlass? How is the bank currently charged?

 

[Screen Saver]

I avoid posting on battery threads because the subject is out of my lane. But I'll add an observation here. Golf carts. My course has replaced the old lead acid carts with lithium carts. They suck. 'though well charged they have no umpf - that's an engineering term - when starting from a stop. Once they go for a bit they build up speed. I've hypothesized that the poor performance at start up is due to whatever lithium technology they use. I think that observation is in line with Dave's statement above.

Yea could be new carts. Lithium batteries have far better initial current than any other conventional technology. I have had an oscilloscope on mine and a hit of 120amps on 12v makes little impact when you look at the initial start. Same goes for my windlass, or electric winches, engine starting etc. its also clearly noticeably better, if you have a high-powered sound system with bass notes you can tell, or HF radio on full power at nights the lights dont drop at all etc. However, all that said the point that Dave makes above is the BMS has to be able to deal with it. Keep in mind they are used in electric cars so when someone stomps on the go pedal they can't have a lack of umpf.

 

[dlochner]

Yea could be new carts. Lithium batteries have far better initial current than any other conventional technology. I have had an oscilloscope on mine and a hit of 120amps on 12v makes little impact when you look at the initial start. Same goes for my windlass, or electric winches, engine starting etc. its also clearly noticeably better, if you have a high-powered sound system with bass notes you can tell, or HF radio on full power at nights the lights dont drop at all etc. However, all that said the point that Dave makes above is the BMS has to be able to deal with it. Keep in mind they are used in electric cars so when someone stomps on the go pedal they can't have a lack of umpf.

The problem with high current draws on LFP banks used on boat is not the LFP cells inability to deliver the current, the problem is the BMS's ability to survive that kind of current drain. Some batteries use that can handle higher loads than other batteries. The point is these are not like LA batteries, it is important to know and understand the particular limitations of the installed battery.

Lithium based batteries used in electric cars have a different chemistries, that is an important distinction to make.

 

[mermike]

It depends on the windlass requirements. LFP at first glance seems like the best solution, but as @dlochner says, the current draw through the BMS is the limiting factor. I run my windlass from my 12v 400 AH house bank, but I made sure the current draw was well within the BMS spec, amd I run the engine when pulling the anchor regardless, to add the alternator output to the available current.

 

[mermike]

I will add that several companies offer dual purpose LFP start/house batteries. Epoch and Dakota are 2 that I know of. 2 Epoch 105 LFP start batteries wired in series should work very nicely.

 

[jssailem]

For most of my windlass usage I am running the auxiliary with the alternator providing a charge to the battery. I would get a battery that can be serviced from the regular charging off the alternator.

If this charge source is designed for 12v flood acid then I would get two FLA batteries to power the windlass. No reason to add a new charging system if the current one is functioning.

 

[American_Mainsail]

@jssailem This is my thought as well, which is why I asked what OP’s existing charging setup is. For the house bank, there are huge benefits to switching to LiFePO4, but for something that’s used intermittently, I think there’s still a good argument for staying with FLA or upgrading to AGM.

 

[Screen Saver]

Yea the above views are not uncommon, and I readily admit that for most I am possibly of a different view. Many have just followed so called experts, and sadly many "experts" are not, so we all must make our own assessment. For mer persoanly I try these things and apply logic to the theory. A quick google will reveal the chemistry in some cars is the same as what we are talking about. " Yes, Lithium Iron Phosphate (LiFePO4) batteries are increasingly used in cars, especially in electric vehicles (EVs). " Along the lines stated above its not the LifePo4 thats the problem with high start current. Its the BMS. Mine deals with all of the above and has done for 5 or so years, and I do not always start my engine to assist the windlass. There is no reason for me to do it, as long as the BMW will deal with it, which it will. This is an American boat with heavy loads, 6 electric winches, microwave etc and all the normal starting loads. Lets look at the other commonly stated problem, ie blowing diodes perhaps because the BMS disconnects the battery. I dont know your boats but the chances of my boat not haveing a load would be extremely rare, be it fridges, nav gear audio etc. In my early days of testing for protection purposes mainly due to all the rumor mongering I reduced the cut off load from what I consider was very extreme (800 amps) down to 100amps. This caused a number of disconnects during charging at 80-120amps. I probably did this in the early stages 10-15 times as I slowly cranked the disconnect current up. No days yep if the anchor is coming up and someone uses the microwave it will still disconnect, but that is my choice. People talk about special fusing on the batteries. Bascily if you have any sort of working fuse or breaker system ( so long as it works) there is no great need to make any changes. My boat already had 300amp battery fuses, which I in fact reduced. The bottom line here (in my personal view) you have far more control over your power source with a decent BMS. You can control low shutoff, low charge, high shutoff, high charge, max load for x seconds, etc All things you can't control with other batteries. I actually ran my AGM batteries on there own BMS connected to LifePo4 as test, then later with my start battery, which gives you far more control. The last misnomer as far as Im concerned is the charging side of things. Basically in very simple terms for the live aboard cruiser he need not change a thing in the charging setup (assuming he has at least 3 stage technology) unless they are trying to get the maximum benefit LifePo4. All of your existing charging setup for 99% of cruisers will be less than that of Lithium, the only potential issue is float voltages carried over to Lithium. Having said that I know many will disagree, so send me any setting from your non Lifepo4 batteries that you think would damage lifepo4 batteries if simply carried across.

 

[dLj]

I like AGM's for start batteries and AGM's for my bow thruster and windlass. I prefer Lifeline AGM's because they are the only AGM;s that I'm aware of that publish an equalization cycle for their AGM's. I prefer AGM's over flooded lead acid in my case as they do not require monitoring water levels. Lead acid batteries handle the large amp draw for this application without having to worry about the BMS system of lithium.

My boat is set up with house LiFePo batteries. All charging systems charge the house batteries - shore power, my alternators (I have two), my solar and my wind generator all charge the house batteries. If I were to add any more charging systems, like a water turbine, or more solar panels, they would all charge my house batteries.

Then I have a circuit that pulls from my house bank to charge my starter battery, and another circuit that charges my bow/windlass batteries (I have two AGM's up there). These are two separate system, hence the two charging set-ups. That way I can monitor all systems through monitoring my charging and discharging through my house bank. I always know exactly my state of charge of my entire system. Doing it this way also always keeps my start battery and my bow/windlass batteries fully charged at all times. As sulfation is what typically kills lead acid chemistries, keeping those fully charged all the time minimizes that problem. Keeping lead acid batteries full charged instead of a partial state of charge, and having the ability to perform equalization cycles on my Lifelines means I'll likely get 12 to 15 years of life out of my lead acid batteries.

In this way all charging systems for the house bank run the same charging profile appropriate for my LiFePo batteries, they can take large charging currents. The two separate charging systems are optimized for the AGM's. It may sound complicated, but in fact it is quite simple.

Works for me....

dj

 

[mermike]

People talk about special fusing on the batteries. Bascily if you have any sort of working fuse or breaker system ( so long as it works) there is no great need to make any changes. My boat already had 300amp battery fuses, which I in fact reduced.

This statement is misleading at best, and dangerously wrong at worst. The high discharge capabilty of LFP requires a similarly high AIC rating for the main fuse. This is why Class T fuses are used. Other fuse types do not have a sufficiently high rating and can weld themselves closed, which will deliver all the energy in the battery bank into a dead short. Please don't promote such foolishness, even unintentionally..