T-Pain Is On A Boat: Re: [Electric Boats] AGM Batteries?

I think the decision on which battery technology to go with depends on a number of factors. Money just being one of them. Also how and where you will use the electric boat being another. I'm still not convinced that I would repower with LithIon when my AGM banks says it's time. They are still holding up well after six years. I know LitIon will be lighter than the 8A4D's I have now but, my worst case scenario is cruising down the Intercoastal waterway and one or more of my batteries needs to be replaced. I probably could have new AGM ones delivered to the boat within twenty four hours. Lead time for LithIon replacements is sometimes weeks last time I checked. Not an issue if your boat is at your home dock but, big $$$ if you are a transient boat on a cruise paying dock fees waiting for LithIon batteries to arrive. I'm also concerned about the adding the complexity of the BMS as my AGM bank has been pretty trouble free and requires very little babysitting these days. Of course I also have a sizable investment in chargers setup for my AGM bank too. I'm keeping an eye on the technology but, so far I have not seen enough reason to change from the AGM bank already installed.

Capt. Mike

http://biankablog.blogspot.com

From: Roger L <rogerlov@ix.netcom.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, August 27, 2013 9:34 AM
Subject: Re: [Electric Boats] AGM Batteries?

I suppose sometimes battery type comes down to time versus money.

Boats are my hobby, so time doesn't count.

But running dead batteries back and forth to Walmart comes perilously close to being work - and unpleasant work at that. At any rate, it's close enough to make me figure hourly wage into that argument.

YMMV,

Roger L.

.......

...............

----- Original Message -----

From: oak

To: electricboats@yahoogroups.com

Sent: Tuesday, August 27, 2013 7:23 AM

Subject: Re: [Electric Boats] AGM Batteries?

I was talking to my "boat neighbor" in the slip next to mine last night - he related the same experience that I have had:

In central and south Texas, the thing to do is go to Walmart, buy a battery, put the receipt some place safe. Walmart batteries aren't the best, but they're cheap. And they had 5 year warranties. On a boat in this heat with a charger, the battery would be cooked in 2-3 years regardless of HOW much $$ you spent on it. With the Walmart batteries, they were VERY GOOD about taking the old battery back and prorating for the next one... would typically cost about $30 every 2-3 years to replace the battery. <grin>

My neighbor added another element. I used to very carefully keep the receipts in a file at home. He recalled that for a while, they would put the receipt in a plastic sleeve that was attached to the battery itself. But then they discovered the heat from the engine was turning the thermal paper completely black, so you couldn't read it anymore... :)

I'm used to batteries not lasting very long. That's why I hate to spend a huge investment on them. I have yet to see an ROI.

But I've also never used batteries for such high and long term power demands. The cheapest car battery I could find was always OVERKILL for powering the radio, a few running lights, and MAYBE starting a small engine.

Now I need to be able to pull 10-25A constant for over an hour. It'll be interesting to see if AGM batteries are up to this.

After looking at the Balqor web site, Li may be more approachable. If Li would truly give me a battery that will run much longer, be much more reliable, maint. free, and last many times more cycles, I'd love to try it. Up till now, it's been a matter of sticker shock, and some trepidation about the complication and expense of very expensive chargers and BMS systems for each cell in a bank that would require many, many cells.

Though, it sounds like the care and feeding of Li batteries really doesn't have to be THAT complicated. I have plenty of voltmeters. It would seem that if I bring a lead from each cell out to a terminal strip that's easy to access, it should be an easy thing to periodically check each of the cells.

I would assume that in NORMAL usage, if I watch the voltage of the bank, and don't run it into the ground - then I shouldn't have to CONSTANTLY monitor the individual cells. And if I'm using a small charger, and have plenty of time, then charging need not be either complicated nor terribly expensive.

Will see...

John

From: Roger L <rogerlov@ix.netcom.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, August 27, 2013 7:39 AM
Subject: Re: [Electric Boats] AGM Batteries?

I don't think that lead/acid is dead either. It seems to be a very mature technology. But I think that flooded cells are out of date. They are an unnecessary maintenance headache compared to AGMs. The gel style AGM is simply a more efficient and abuse-resistant way to use the same lead acid technology. AGMs are only slightly more expensive initially, much more resistant to impact, tilt, and charge/discharge cycles, are non-fuming, and last enough longer to more than make up for the difference in price.

Caveat: I live in a cool to cold climate. Things might be different in warmer climates.

Roger L.

...........

......................

----- Original Message -----

From: Carter Quillen

To: electricboats@yahoogroups.com

Sent: Monday, August 26, 2013 12:33 PM

Subject: Re: [Electric Boats] AGM Batteries?

Few will dispute that LiIon technology rocks and that flooded lead acid kind of sux but if you can get to the grocery store in Hundai and can't afford a Bently, you're not going to go hungry because you don't like the ride.

Until the price of LiIon come down significantly, Lead will not be dead!

And although it is highly debated using some very broad assumptions, lead acid is still quite competative against LiIon IMO. Especially if you're strictly looking at Watts/$$$ and not performance capabilities. If you've got the room, get the good stuff like Trojan or Rolls, design your system well and treat your FLA batteries right, I think you will find in a thorough economic analysis that lead acid is very economically competative against LiIon for marine propulsion applications. I would go so far as to say it is most likely a better deal, especially when you simply consider storage capacity per dollar.

Plus the economic risk factors are much lower with FLA because it doesn't hurt that much if you fry $1000 worth of lead acid batteries but a mistake that trashes your liIon system could put you into bankruptcy.

Having said all that, I will admit that I although I'm content with my Toyota Corolla,(that has over half million miles on it btw), that doesn't mean I don't wish I could afford to drive a Bently.

Carter

http://www.shipofimagination.com/

From: Robert Lemke <robert-lemke@att.net>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, August 26, 2013 12:08 PM
Subject: Re: [Electric Boats] AGM Batteries?

From: Roger L <rogerlov@ix.netcom.com>
To: electricboats@yahoogroups.com
Sent: Monday, August 26, 2013 8:38 AM
Subject: Re: [Electric Boats] AGM Batteries?

I quit using flooded cells and went to AGM about 15 years ago for everything on the farm and in the boats as well. All the cars, tractors, and trucks. Much better batteries.

Roger L.

----- Original Message -----

From: oak

To: electricboats@yahoogroups.com

Sent: Monday, August 26, 2013 9:32 AM

Subject: Re: [Electric Boats] AGM Batteries?

John,

Maybe you aren't taking into account the major difference between usable a-hr capacity between AGM and LiFePO4. Since you quoted $200 per AGM, I'm assuming these are no bigger than 100 a-hr. When you calculate for usable a-hr, the AGM shouldn't be pulled down more than 50% DOD, the lithium can be pulled down to 80% DOD for 2000 cycles vs 400 for AGM. How they get their a-hr rating is also different, an AGM is pulled to 100% DOD at a 20 hour rate vs a lithium being pulled to 80% DOD at a 1 hour rate. If the AGM was pulled at a 1 hour rate, the the a-hr rating would be 1/2 of what it is at the 20 hour rate due to Peukert effect. An easy rule of thumb, what ever a-hr worked for your needs with lead, you can size the LiFePO4 bank at 1/2 the size for the same usable a-hr. 200 a-hr lead bank could be replaced by a 100 a-hr lithium bank. I have (2) 12 volt 100 a-hr Winston banks and each ran $440, so again, much cheaper than lead.

Bob

Bob,

If I did the full lifetime analysis, I'd probably agree with you the Li batteries were (long term) a better deal.

The issue is that for me to fund a single 24V bank, I'm looking at around $2500.

For my larger boat, it's $5000 for the 48V bank.

Even assuming $200 per 12V battery for AGM, it's sooo much more affordable on the budget, even if I know I will most likely have to replace the AGM bank a couple of times over the next 10 years. If I spend $1000 on AGM batteries every 2 years, I'd break even on a Li purchase after 10 years. Given that I typically don't keep boats for more than 2 years, certainly not as long as 10 years, it's just too long of a period for ROI. And there's no way I'd begin to expect to get much on resale of used batteries of any type.

If I end up sticking with my C-22 LONG term, and sticking with the electric motor LONG term, I might eventually try a Li pack as the primary battery for that boat, and keep a AGM or possibly even FLA as backup, just because it's soooo much cheaper. But it'll be a while before I can afford another $2500 of hobby bucks.

Again, I'm not disagreeing with you technically. I'd LOVE to try out a LI bank and see how well it really works. It's just the initial investment plunge that's holding me back.

John

From: Robert Lemke <robert-lemke@att.net>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, August 26, 2013 10:15 AM
Subject: Re: [Electric Boats] AGM Batteries?

John,

I used to use Odyssey AGM for my electric kayak for a 16~18 mile range. Last year I switched to LiFePO4 and the same weight in batteries, now have a 80 mile range. When you consider cycle life, these Winston lithium cells give the best bang for the buck.

http://www.balqon.com/store.php#!/~/category/id=0&offset=0&sort=priceAsc

Bob

From: oak <oak_box@yahoo.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Monday, August 26, 2013 6:06 AM
Subject: [Electric Boats] AGM Batteries?

I recently noticed that a number of my deep cycle marine flooded lead acid batteries had been pretty much cooked dry from the Texas sun and the relatively moderate discharge cycles of the Torqeedo motors.

The batteries are Exide batteries, group 27, 160 reserve minutes. After re-filling the batteries, they would charge, but certainly won't take a load for very long. The batteries came with a 2 year replacement warranty - and at this point are less than a year old.

I went by the place where I bought them, and noticed they had Exide Vortex AGM batteries (group 24, 100 reserve minutes) on sale for $119.

I pulled two of the most problematic FLA batteries (would take a charge, but at less than 25A were dead in 5-10 minutes), and returned them. The store gave me a full refund, which I turned around and put toward purchasing two of the AGM batteries to give a try.

I have discovered that "maint. free" deep cycle batteries aren't. And they can't begin to take the heat of a Texas summer. However, the power density was ok for my needs. When they were new, and performing well, I could get over an hour run time out of them at moderate power (though this was still far below the rated 160 minutes at 25A rating!)

Will I get better results from the AGM batteries??

Is it realistic to expect with AGM batteries rated for 100 Reserve Minutes (which I understand means I can run them for 100 minutes at 25A load) that I can actually pull 10-20 amps for over an hour, and then charge them back up on a fairly regular basis?

John