Monday, August 26, 2013

Re: [Electric Boats] AGM Batteries? >> LiIon usage rate??

 

The CA in <1CA or <3CA does not mean continuous amps. The C is capacity. In your example, pulling 1C would be 60 amps because you are talking about a 60 Ah battery.

--- In electricboats@yahoogroups.com, oak <oak_box@...> wrote:
>
> Ok, so I took a quick look at the balqon web site, and see that they offer a 12V, 60Ah Li battery for $300.
> HOWEVER, the web page lists "max discharge current" at "<1CA" - does this mean less than 1 continuous Amp???
>
> I understand if that means I'll only get 60Ah at least than 1A continuous.
> But what is the limit to how much current I can pull out of the battery for a continuous period of 1-4 hours?
>
>
>
> ________________________________
> From: Steve Dolan <sdolan@...>
> To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
> Sent: Monday, August 26, 2013 11:28 AM
> Subject: RE: [Electric Boats] AGM Batteries?
>
>
>
>  
> John, John, John,
> I’m running a bank of 12 AGM’s for the
> last 8 years and they seem to be still going strong. I have noticed the last
> year some degradation thoug so I’m getting close and Yes I will go to LiFePo4’s
> when it’s time so will save for that day
> Only  $2500??
> Replacing my 200AH 144V bank with LiFePo4’s
> will run around $12000. The good news is Bob’s post got me thinking about what
> size I really need.
> Unlike cars and forklifts we are more
> interested in run time at a set speed in boats. Often I’ve found when talking
> to Car Guys they haven’t a clue what we are up against when figuring out pack
> size since we normally maintain a set speed for hours running from point to
> point in adverse conditions, typically using 1C. I couldn’t figure out why all
> of them where going with smaller packs. Bob has me thinking, I didn’t consider
> the difference in Ah rates. Since I would only pull .5C (about 50A max at 6
> knots) on a set of 100 AH LiFePo’s I can get away with ½  the cost I was
> considering (200Ah)
> I might owe Bob a commission…  8O)
>  
>  
> Steve in solomons MD
>  
> 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@...>
> >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@...>
> >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
> > 
> > 
> > 
>  
>  
>

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