Gel or AGM and bunch of 6v or a few 8d's?

[rwidman]

Why? Is it because they're cheaper to buy?

The biggest advantage of AGM is their more rapid charge rate............

For me and a few other folks, the biggest advantage of AGMs over flooded cell is the low/ no maintenance. Replacing my flooded cell batteries with AGMs means I no longer have to remember to climb down beside the engine or prop shaft and use a mirror and flashlight to try to determine the electrolyte level every month. And then figure a way to add water to the correct level.

It's worth the cost for me, better performance is icing on the cake.

 

[psneeld]

While I agree in principle with FF that wet batteries are a "better buy", The big advantages of AGMs are (1) minimal (no) maintenance enables them to be stuffed into (almost) inaccessible spaces; and (2) if you anchor out a lot for extended periods, they charge faster which translates into less run time on the generator -- less fuel, less wear.

based on the generator operation hours thread...many more people need to run their genset more anyway....

 

[Moonstruck]

One big advantage to AGMs is no off gassing thus little terminal corrosion from acid.

 

[Art]

Batteries, their power reserve, charging time, and DC longevity! I keep it simple / productive / cost-wise!

Some times we hang at hook for 3 to 5 days… or longer. On our 34’ Tolly Tri cabin we keep 6 batteries at the ready (all batts new early 09 – still doing great in 13!). We’re often out for days; cruising and hooking. Never stay at dock in decent weather.

Battery Bank:

- 4 – Flooded, lead acid, “semi no-maintenance”, deep-cell, BCI Group 31 batteries: Each 105 amp hrs / 650 cold crank amps / 182 minutes reserve capacity. These batteries are used for engine starting and also general usage. They are charged by motor alternator or by Pro Mariner charger on boat when Kohler genset runs, or by the same charger when hooked to dock AC.
- 1 – Flooded, lead acid group 27 starter battery: For Kohler genset. It is kept charged by solar panel attached to fly bridge front (so genset can always start - to charge any batteries if/as needed); and/or by 1 amp charger mentioned for next battery, or by genset alternator.
- 1 – Flooded, lead acid group 27 starter/deep-cell battery combo: A reserve, completely independent battery hooked to nothing and stored in a separate battery box. It is kept on top charge by a 1 amp trickle charger that sits inside this battery’s box and is activated upon Kohler genset use or dock side AC whenever the 120 in-boat outlet breaker is turned on. The 1 amp charger also has its own easy access on/off switch for if we were to keep boat on dock power for extended period with 120 breaker on.

Total battery cost (early in 2009): $595.00 – Including all 6 batteries, 1 amp charger, large single battery box and taxes. I plan to keep these batteries in good condition for years. Ya just gotta love “Batteries Plus” stores!

Long and short of it… I’m a simple boater who uses DC power (as well as most/all other items) carefully and sparingly on a boat.

When at anchor: We usually run the Kohler genset in morn for about 30 to 60 minutes so we can use the stove for bacon, eggs and coffee; we simultaneously turn on other breakers; e.g., 120 outlets to charge our VCR player’s battery / refrigerator / battery charger / hot water heater. And, we run the genset for approx same length of time in eve to cook dinner as well as to turn on the same breakers. Of course when we cruise battery charging of our 4 mains is well handled by the engines’ alternators.

This schedule affords us all the battery power we need and keeps our other features in useful conditions.

BTW – I don’t use float chargers. Have before, but from experience I feel they too often over charge the batteries and can considerably shorten their life. If batteries are in good condition, fully charged and have all sources of power drain shut down when leaving boat… they will remain substantively charged for months on end. Therefore I always turn every item off; Perko main switches included, and do not even have need to leave our AC dock line plugged in. Upon arriving at boat we immediately plug in dock power, turn on battery charger breaker as well as several other breakers and flip the Perkos on. Works great for us… Everything’s ready by the time we’re set to pull out for days on end of exciting Tolly Fun!!!!

Simple is as simple does! We do love our Tolly Time!! - - > Cruisen, partyen, swimmen, diven in SF Delta’s warm fresh waters – YUM!

 

[deckofficer]

If you cycle your house bank a lot, as in a cruising and anchoring out full time lifestyle, then the cheapest and best battery is LiFePO4 cells. 3000 cycles at 80% DOD vs 500 cycles at 50% DOD, minimal voltage sag under heavy load, and almost zero Peukert effect along with the highest charge acceptance. I've used golf cart 6 volt batteries, L16's, 2 volt 700 a-hr AGM, and none are anything close in performance to the LiFePO4 cells I'm running now. Also 1/3 the weight per given energy density.

Just the difference between 19th century technology and 21st.

 

[deckofficer]

If you desire some math to support my claims, lets start with the best lead acid for this purpose, the 2 volt 900 a-hr AGM, currently available at Lifeline GPL-6CT-2 Volt 900AH AGM Battery for $381.97, so for a 12 volt (10.8 KW-hr) bank $2292. But you have to remember that 900 a-hr rating is based on 20 hours and is quickly derated to less than 800 a-hr at typical inverter loads, i.e. Peukert effect. Now your bank is 9.6 KW-hr, but since you want those 500 cycles you can't discharge deeper than 50% DOD. Usable energy from this house bank is 4.8 KW-hr.

(4) 700 a-hr LiFePO4 cells run $2240. These cells in a 20 hour rating give 25% more than their rating, my cells do and everyone on the Cruiser's Forum report the same. They are very conservative in their ratings. Since Peukert is nil and DOD is 80% for a life of 3000 cycles, you can see the cost savings, not to mention not having to change out batteries for 15+ years.

AGM lead acid, $2292 for 4.8 KW-hr usable, for 500 cycles

LiFePO4 lithium $2240 for 7.3 KW-hr usable, for 3000 cycles.

 

[caltexflanc]

Where are you finding the LiFePO4s for that kind of price? TIA. Here's the best i could find, almost 3 times that price for 600ah.

http://www.lithiumion-batteries.com...ion-battery/12v-300ah-lithium-ion-battery.php

By the way you can cycle good AGMs down 60-70%. I'm a wet cell man myself save the generator start battery; my batteries are extremely easy to service. I got the sam duty cycle out of my wet cell L16's (4 for 24v) of identical capacity to your illustrated 12 volt AGM system. They run about 1200 in todays money. So I think you are underselling the AGMs a bit.

 

[deckofficer]

George,

Here is the link to the wholesaler and he sells to the retail market. Balqon - Advanced Transportation Solution

I have had very good service from all the AGMs that I have used over the years. I used to race an EV I built that used the little Odyssey PC680s, and I pulled over 400 amps on a regular basis from those 15 lb batteries. I have nothing but good things to say about AGM, but there is a much better and cheaper battery out there.

On the Cruiser's Forum we have a thread that has gone to 2488 posts just on LiFePO4 cells for housebanks. About a dozen members there jumped on the Balqon clearance sale when I posted it, and they are flat out loving their battery upgrade. I've never seen outside of my EV group such a passion on batteries as on the Cruiser's Forum. LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks - Cruisers & Sailing Forums

 

[deckofficer]

To give you an idea of how much energy density we are talking about using LiFePO4 cells, I had a recent, very small project for my electric kayak. A group 27 battery would give 16~18 nm on a charge, not near good enough for kayak camping. I put together (2) 12 volt 100 a-hr LiFePO4 packs for the kayak that weigh just a bit less than the single group 27. What I got in range is around 80 nm, more than enough to cruise the entire 75 mile shoreline of Lake Tahoe and still have enough power for my Engel fridge and Coleman LED lantern.

MOV02923 - YouTube

 

[Chrisjs]

What are the charging parameters for the LiFePo4 batts?? Dp you charge them as "wet", "AGM" or "gel". I do not have a LiFePO4 setting on my charger??

 

[deckofficer]

I bought for this purpose an 8 lb fast charger for LiFePO4 cells and would not recommend it for its voltages used on a housebank. My need was to be able to quickly charge during a lunch break at a marina. You have to do a bottom to top balance of your cells, all in parallel with a variable power supply which will take about 100 hours. You need a tight balance because this charger for (4) in series runs 14.9 volts which doesn't give much leeway for unbalanced cells staying below 4.0 volts. There is a ton of info on bulk, float on that Cruiser's Forum link I gave above.

 

[Wxx3]

If you cycle your house bank a lot, as in a cruising and anchoring out full time lifestyle, then the cheapest and best battery is LiFePO4 cells. 3000 cycles at 80% DOD vs 500 cycles at 50% DOD, minimal voltage sag under heavy load, and almost zero Peukert effect along with the highest charge acceptance. I've used golf cart 6 volt batteries, L16's, 2 volt 700 a-hr AGM, and none are anything close in performance to the LiFePO4 cells I'm running now. Also 1/3 the weight per given energy density.

Just the difference between 19th century technology and 21st.

Sounds great. tell me more. How much $$/amp hour?

Richard

 

[rwidman]

To give you an idea of how much energy density we are talking about using LiFePO4 cells, I had a recent, very small project for my electric kayak. A group 27 battery would give 16~18 nm on a charge, not near good enough for kayak camping. I put together (2) 12 volt 100 a-hr LiFePO4 packs for the kayak that weigh just a bit less than the single group 27. What I got in range is around 80 nm, more than enough to cruise the entire 75 mile shoreline of Lake Tahoe and still have enough power for my Engel fridge and Coleman LED lantern.

While you can make an argument that these batteries are better than group 31 AGM batteries, if you ever find yourself in the boondocks needing a replacement, you're likely to be in trouble.

I needed a replacement while on a cruise so while stopped at a marina waiting out a storm, I borrowed their loaner car, drove to Sears, and got my replacement over the counter.

 

[deckofficer]

While you can make an argument that these batteries are better than group 31 AGM batteries, if you ever find yourself in the boondocks needing a replacement, you're likely to be in trouble.

I needed a replacement while on a cruise so while stopped at a marina waiting out a storm, I borrowed their loaner car, drove to Sears, and got my replacement over the counter.

We cruisers live by Fedex.

 

[deckofficer]

Sounds great. tell me more. How much $$/amp hour?

Richard

So far no one beats Balqon on LiFePO4 prices.

Less than $1 per a-hr on 3.2 volt cells from 40 a-hr to 1,000 a-hr. The ones I like for house/propulsion bank are the 700 a-hr because each 3.2 volt cell only weighs 47 lbs, so not a back breaker getting them onboard.

Balqon - Advanced Transportation Solution

 

[rwidman]

We cruisers live by Fedex.

We do?

 

[Art]

So far no one beats Balqon on LiFePO4 prices.

Less than $1 per a-hr on 3.2 volt cells from 40 a-hr to 1,000 a-hr. The ones I like for house/propulsion bank are the 700 a-hr because each 3.2 volt cell only weighs 47 lbs, so not a back breaker getting them onboard.

Balqon - Advanced Transportation Solution

Quote from my post #34

“- 4 – Flooded, lead acid, “semi no-maintenance”, deep-cell, BCI Group 31 batteries: Each 105 amp hrs / 650 cold crank amps / 182 minutes reserve capacity.”

In 2009, under $100 per 105 ah batt = <$1.00 per amp hr (2013 cost is right at $1.00 per ah).

I well understand that these Group 31 Deep Cycle wet-leads mfgd by DEKA East Penn manufacturing co. http://www.dekabatteries.com/default.aspx?pageid=356 and sold under Batteries Plus trade mark “SL132DC Xtreme Deep Cycle Battery” are nothing like LiFePo4 lithium batts... but... they are well guaranteed from the beginning, charge easy, last pretty long (4 yrs so far w/no prob), are primarily sealed with large screw-on access ports to check levels and easily add water if needed. Most importantly they are low cost, available, and once you get in good with owner of local Batteries Plus store – there are perks! http://www.batteriesplus.com/produc...atteries/106979-Deep-Cycle/BCI-Group-31M.aspx

I play the game of low-cost KISS and love to make my life easy... especially regarding our little tri cabin pleasure cruiser, toy boat!

With that said: – Lithium marine batts may be the choice of a group I’m working with. We hope to be able to offer the boating industry some nice items. Nuff Said!

 

[caltexflanc]

That's some cool stuff there thanks a bunch. Keep us apprised of how it all holds up and other findings. How long do you think they will have that close out?

 

[deckofficer]

That's some cool stuff there thanks a bunch. Keep us apprised of how it all holds up and other findings. How long do you think they will have that close out?

Not much longer. Have you checked quantities?

 

[portager]

Sorry for reviving an old thread, but I've been too busy at work to comment for awhile so, …

Hello George;

This is no trifling matter to me either. I've worked as a engineer in the Aerospace Industry for 33 years and I select batteries and configure battery banks for a living. If I'm wrong, I might not be stranded at sea, but I would have a lot of unhappy customers and I’d soon be out of a job. I have read and fully comprehended Nigel Calder's book several times. I agree with most of it, but I don't blindly follow everything he writes.

... In a parallel bank you can just replace one battery and pretty much get away with it. In a series bank you will only get away with it for a very short time until the other batteries are dead, and the new one is dead too. ...

I’m sorry, but that is exactly backwards. As Nigel Calder points out in his book, batteries are primarily recharged by applying current. Voltage defines the state of charge but current determines their capacity. That is why they are rated in amp hours.

In a parallel battery bank the current is divided and it flows through each parallel leg based on the electrical resistance of each leg. If all the batteries have matched resistance, then each leg will receive the same current and they are all charged evenly. However, battery internal resistance increases with age, use and abuse. If one battery fails and you replace it with a new battery, it will have a lower electrical resistance than the older battery (or batteries). In this case the lower resistance leg will receive more current and the higher resistance battery will get less. The charger will shut off when the voltage reaches the preset level. The new battery will be fully charged, but the old battery will be undercharged. This is mismatched charging. Since the old battery is undercharged and it is connected in parallel with a fully charged battery, the undercharged battery will draw current from the fully charged battery until they both reach the same voltage. This will wear out the new battery faster than it should and it will accelerate the demise of the old battery due to sulfation, since it never finishes float charge. You might get away with this for a little while but soon all the batteries will be shot.

In a series battery bank there is only one leg, the same current flows through all the batteries, so they are all charged to the same level. If one battery fails you can replace it with a new battery and they will all be fully charged because they all receive the same current.

On the other hand, if you have a battery bank that you are depending on working properly, like a bow thruster bank, I would recommend a parallel battery bank of no more than two legs. Because if a cell fails open (i.e. like a disconnect) in a serial bank you will have no power and no thruster. However, in a two leg parallel bank, if one cell fails, you will still have full voltage but only half the capacity (in Amp hours). Assuming you determine that one battery failed you can disconnect it and continue to use the remaining leg. Once you are ready to replace the failed battery you will need to replace all the batteries in the parallel bank.

 

[portager]

When comparing batteries of comparable technology, you can divide the cost by the rated capacity in amp hour to get dollars per amp hour provided all other parameters such as voltage, recommended or anticipated depth of discharge and cycle life are the same. However, to accurately compare batteries of different voltages, you need to multiply the voltage by the amp hour capacity to get the energy storage capacity in watt hours or divide by 1,000 to get kW*hrs. Then you can divide the cost by the energy storage capacity to get $/kW*hr.

If the manufacturer’s recommended or your planned depth of discharge (DoD) or the predicted cycle life are different, then you need to multiply the energy storage capacity by the DoD (as a fraction not a percentage), which is the expected energy storage capacity per cycle, and then multiply by the predicted cycle life for that DoD, which is the expected lifetime energy storage capacity (note the units are still kW*hr because DoD and cycle life are unit less). Now you can divide cost by expected lifetime energy storage capacity to compare the acquisition or initial cost of different battery technologies.

 

[Art]

Hi Portager - You're a wealth o' knowledge on dealing w/batts.

I copied your two recent posts and placed in my batt info folder! Could you do me a favor by commenting on my post # 47; this page of this thread. I try to keep things simple as possible... any suggestions as to how I could make it even simpler / less costly / better, easier usage parameters?

Happy Boating Daze

Thanks - Art

 

[Codger2]

................. Now you can divide cost by expected lifetime energy storage capacity to compare the acquisition or initial cost of different battery technologies.

(Whew!) So, being somewhat math challenged, which batteries do you consider to be the best buy?

 

[deckofficer]

(Whew!) So, being somewhat math challenged, which batteries do you consider to be the best buy?

That would depend on your usage. If your full time cruising and anchoring out where you cycle the batteries a lot, then LiFePO4 is cheaper in the long run by far. If you just get out a few times per year, 6 volt golf cart batteries give good bang for the buck. If you don't like flooded, dealing with corrosion, hydrogen gas, etc, then AGM.

 

[sunchaser]

If you don't like flooded, dealing with corrosion, hydrogen gas, etc, then AGM.

I have none of these problems with my LAs, never have in my boating years with enclosed batteries in the ER utilizing good chargers. Look beyond the marketing hype. The only way non LA's get sales from the big kid on the block is to run down the LAs and toss out advertising gibberish. Interesting that new high end cars cars use LAs. My last set of LAs for the house bank went 8 years and were still doing fine!!

I do use AGMs where needed, such as the thruster bank where batteries are in the bilge under the forward head and tough to get at.

This thread is similar to the syn vs dino assumed pros and cons. All will work just fine but advertising BS gets in the way of common sense and passions arise.

 

[deckofficer]

I don't go with ad bs either. I have set up many off grid homes, design and race electric vehicles, and I do know batteries. Like I said, if your cruising full time and are on the hook instead of marinas, where you are cycling your batteries constantly, then you can't get better bang for your buck than LiFePO4 cells period.

For off grid homes I've used 6 volt golf cart batteries, L16s, Rolls, and 700 a-hr 2 volt AGM. Of that group for any given capacity, the AGM has by far the best charge acceptance, allowing a 1C charge rate vs. 0.1C for the flooded. An Odyssey AGM is both a deep cycle and cranking battery, giving much higher discharge rates than any flooded of the same a-hr rating. I can see why they are used as a thruster battery, where else will you find a 15 lb battery capable of 680 amps?

If you have a multi hull sailboat where weight is a penalty, lithium is the way to go. If you cycle a lot, a LA doesn't want to go deeper then 50% DOD if you hope to get 500 cycles from it. LiFePO4 have no problem going down to 80% DOD and still giving 3000 cycles.

Like I said, if your a weekend only boater then go with the LA, but if a cruiser go with LiFePO4.

 

[caltexflanc]

Portager, I still strongly disagree, despite your asserted bonafides. I would like to see a third party citation, as real-life experience as well as theory put forth by everyone else (not just Calder) I can find, but you, are in contrast to your unique position here. For one thing, in a parallel bank, the voltage will equalize across the bank from the strong (new) to the weak (older) battery before a charger even gets into the picture. Then, a charging source will bring them all up to voltage. One of the main reasons for those auto charge relays for charging a starter battery and a house bank. This is why you can "get away with" replacing a single battery in a parallel bank, not by any means ideal but doable. In a series bank, you don't have this equalizing effect. The "same current" running through them means, it will inevitably over charge good (or newer) cells while trying to charge bad cells in an attempt to bring up the entire bank. I've seen the idea of substituting one new battery in an older (> 6 months) series bank fail time and time again, on boats and golf carts and floor polishing machines including my own bow thruster bank. This can be caused by batteries aging or being maintained differently, or the practice of taking a lower voltage tap off I higher voltage bank (say using one of the 12's in a 24 bank for starting a generator). You can overcome this to a large degree on a two battery bank (say those two twelves on a 24) by charging each battery from one leg of a two bank 12v charger. That way each battery is charged according to its individual requirement. You see this done by guys with trolling motors on their bass boat, and in industrial applications (for instance:
Multi Bank Chargers)

 

[MVNoPlans]

To the OP: three years ago after some online surfing at various forums I went to Batteries Plus and purchased 2 six volt golf cart batteries as my house bank hooked up to a 1000w true sine wave inverter by Xantrex. The batteries were inexpensive and have worked fine. As for use, we typically anchor out every weekend Friday to Sunday from June thru October. I hook back up to shore power and recharge through a very basic charger when I arrive back at the marina, though my alternator seems to do the trick on the 1-2 hour run back on Sundays. I have recently spotted Trojan 105s for $110 ea. Mine were about $80 each. I run a small table lamp with fluorescent bulb, mobile phones, laptop, stereo and house lights (non-led) with no problems. I also recharge my cordless drill and some rechargeable flashlights and handheld VHF.

 

[FF]

Trojan 105s for $110 ea. Mine were about $80 each.

Currently $90 CASH , each, with trade in in Ft Meyers FL.

 

[portager]

Previously I discussed the acquisition or initial cost comparison of batteries. Next, I’d like to address the maintenance or life cycle cost of batteries. I’ll leave it to you to address your additional maintenance or watering costs since only you know the value of your time. So, I’ll just address the cost difference of charging. Some people seem to think that if they recharge their batteries while underway or while the generator is already running it costs them nothing. This really isn’t true. Even if the engine is running anyway, it still takes additional power and fuel to turn the alternator. Even if the generator is running under loaded, it takes additional fuel to produce the electrical power to run the battery charger. So how do you determine how much fuel your batteries take and how does your choice of flooded lead acid (FLA) or absorbent glass matt (AGM) impact that cost?

Starting with the batteries, the primary factor is the charge acceptance or charge/discharge efficiency. Charge acceptance or charge/discharge efficiency is defined as the discharge energy output divided by the energy required to fully charge the battery. FLA batteries (other than those intended for stationary applications) use a lead-antimony alloy in the plates. Alloying lead with antimony makes the plates stronger to survide shock and vibration loads, but it increases the electrical resistance and self discharge rate. Lead-antimony FLA batteries are generally reported to have a charge/discharge efficiency of 50% to 92% (see Wiki LeadAcid Batteries ) and due to the wonders of marketing most FLA battery manufacturers claim a charge/discharge efficiency at the upper end of that range (for example see Trojan Battery Company - Technology Info ). It turns out that the charge/discharge efficiency is dependent of the state of charge (SoC) and it ranges from 91% for a SoC from 0% to 90%, but drops to 50% for a SoC from 90% to 100%. So the actual charge/discharge efficiency will vary depending on the DoD your starting at from 50% for 10% DoD to 84% for 100% DoD. Since we plan to use a 50% DoD we will use a charge/discharge efficiency of 78% (91% from 50% SoC to 90% SoC and 50% from 90% SoC to 100% SoC). For AGM batteries we will use the widely published and generally accepted 99% charge/discharge efficiency.

For discussion purposes, let’s assume that we have a 12 volt FLA battery with 100 AH capacity and an 12 volt AGM battery with 100 AH capacity. If we use each battery to 50% DoD we should get about 1,000 cycle life from each battery. So the expected lifetime energy provided will be 100 AH *12 V*.5 (DoD) *1000 cycle life /1000 W/kW = 600 kWhr of energy output. Now to charge each battery over their lifetime the FLA battery will require 600/.78 = 767 kWhr of input energy and the AGM battery will require 606 kWhr of input energy. Assuming the alternator on the main engine provides the input energy while underway and the alternator efficiency is the typical 50%, then the main engine must provide 1,535 kWhr to the FLA battery and 1,121 kWhr to the AGM battery. Using a typical fuel conversion efficiency from diesel engines of 0.055 gallons/HPhr = 0.0737 gallons/kWhr the fuel required to charge the FLA battery 1000 times is 113 gallons over the life of the battery and the fuel required to charge the AGM battery 1000 times is 89 gallons. At a fuel cost of $4/gallon this equates to $453 to charge the FLA battery and $358 to charge the GAM battery or a difference of $95. Now if the AGM battery costs 2x that of the FLA battery and the FLA is around $100, then the actual savings of the FLA battery is ~$5 over the life of the battery or your earning about $1 per year for watering your battery. Repeating the math exercise assuming an AC generator with 80% efficiency and a battery charger with 80% efficiency reduces the cost difference to $74 so the net savings is $26.

It should also be noted that these calculations assume that you’re only recharging while underway or while you’re running the generator for another purpose. If either power source were run just to recharge the battery the recharging cost should include engine maintenance cost and would be higher. OTOH, if you’re recharging at the dock using shore power your recharging cost would be much lower (or zero if you pay a flat rate for power).

One additional factor to consider is where do all the extra energy to overcome the lower charge/discharge efficiency go? It goes into waste heat and it is dumped into the battery partially during charging and partially during discharge. This waste heat increases the operating temperature of the battery, which in turn reduced the life expectancy battery.

In conclusion, if you do the math you will see that the initial or acquisition cost advantage of FLA batteries is nearly consumed by the additional life cycle cost due to the lower charge/discharge efficiency of FLA batteries relative to AGM batteries. When you consider the reduction if maintenance effort and the safety advantages, I think AGM batteries are a clear winner over FLA batteries.