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Renogy Batteries
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The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
They are good at one thing, social media marketing. They will sell you the chrome off a trailer hitch...Oh wait your ball rusted.. Ghosted....
ranger58sb
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Nifty illiustration.
For the thread... I think I made our interest clear: we want as much charge as possible in the first hour (or maybe two), when we're anchored out somewhere. I don't much care about finish time. I know I'll need to top off the batteries when we return to the dock... next week or so... but for this week, "today," that's a minor detail.
In boats we've had, the main battery banks have always been dual-purpose, and I guess so far there aren't many LFP options available for that. AGMs and wet batteries (and gel, I guess) tend to be what's viable. (I think I did see a ref recently to a high voltage LFP, but now I can't find that ref...)
Or... we could probably spend a lot of money to somehow split the battery architecture... but even that wouldn't usually be easy due to space layout.
So it's easier, for us, to just live with AGMs and go boating.
Edit: Hah! Maybe it was a link to Dakota Lithium "dual purpose" LFPs that I saw earlier someplace. Interesting to see that in the marketplace.
https://dakotalithium.com/product/24v-135ah-trolling-motor-battery-set-dual-purpose-marine/
Not enough cranking amps in those for our situation, but I suspect it's good to see some movement in that direction. I note their 24V dual purpose package (1000 CCA and 135 Ah) is marked down to $2299, still about $700 more (near term) than initial costs for a pair of Lifeline 8Ds (1350 CCA and 255 Ah).
-Chris
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sunchaser
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There are additional costs to purchase and install the support equipment for moving from Lead acid to LFPs. Dependent upon one’s current setup the support devices can exceed the cost of LFPs.
But as boaters, new stuff is fun and opens doors we hadn’t thought of. I do marvel at my short cruise distance marina neighbors who rave about their $10k plus LFP and solar arrays while they largely sit at the dock. Cruising plans do matter.
But as boaters, new stuff is fun and opens doors we hadn’t thought of. I do marvel at my short cruise distance marina neighbors who rave about their $10k plus LFP and solar arrays while they largely sit at the dock. Cruising plans do matter.
Wow, thank you for all the replies! This has been helpful and informative. I’m going to try the Renogy’s AGMs. Have a friend that put them on 150ft boat with good luck. We will see. Good points on having a separate bow thruster battery. Certainly risk there if run off the house battery.
ranger58sb
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catalinajack
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This article illustrates just that.. but with AGM so expensive compared to LFP it makes zero sense buying them for house bank use...
https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/
Difference between .2C & .4C
This article illustrates just that.. but with AGM so expensive compared to LFP it makes zero sense buying them for house bank use...
https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/
Difference between .2C & .4C
Rod, since flooded batteries generally have a charge acceptance rate of .2c, would it not take a similar amount of time to charge a flooded battery and an AGM charged at .2c? The reason I ask is because, other than non-technical reasons, I see virtually no reason to choose AGMs vs flooded batteries given that AGMs cost at least double and deliver very little longer lifetime, if that.
As a practical example, it takes 5.5 hours to charge my 920ah flooded bank from a 50% depth of discharge, which is almost identical to your test results on that AGM. It takes 5.5 hours whether on shore power or with the alternators while cruising. What am I missing?
ranger58sb
Guru
Just noting that Trojan ref I posted above suggested charging their flooded batteries at .13C.
Don't know if that's common, didn't check other brands... but maybe Rod will speak to that anyway.
(IIRC from the calculations, your charging rate is almost exactly .13C? Or did I do that math wrong?)
-Chris
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catalinajack
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Geez, Rod, all I know is that three different monitors report 100%, my Magnum controller, a Victron 712, and a Balmar SG-200. What is your experience on charging time for flooded batteries?
sunchaser
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CJ
My thoughts, echoing what has been written on TF for almost a decade now.
The missing information is how far down do you deplete your FLAs. Only guessing but Rod’s testing is based upon drawing down to 50% or more.
Then comes in how is recharging done both by equipment and daily cruising hours. No doubt the east coast and islands lend themselves to shorter day hops and longer days at anchor. This is a perfect venue for LFPs and provides the ability to splurge on at anchor amp use.
For those with sizesble FLAs and modest overnight drawdowns it comes down to how quickly can one replace 150 - 290 amps or so. Replenishing 200 amps is not too tough with FLAs and suitable alternators, generator run time and or solar.
But Rod is right when trying to replace 400 + amps into FLAs, it takes time. Herein lies the beauty of LFPs, they can recharge 400 + amps quickly for over a thousand cycles while drawing way down beyond what is sensible for FLAs.
One’s cruising style, curiosity, pocketbook and sense for innovation opens the door for pursuing new things technical. This is where Rod is, probing those boundaries and advancing his and our knowledge in useful ways.
My thoughts, echoing what has been written on TF for almost a decade now.
The missing information is how far down do you deplete your FLAs. Only guessing but Rod’s testing is based upon drawing down to 50% or more.
Then comes in how is recharging done both by equipment and daily cruising hours. No doubt the east coast and islands lend themselves to shorter day hops and longer days at anchor. This is a perfect venue for LFPs and provides the ability to splurge on at anchor amp use.
For those with sizesble FLAs and modest overnight drawdowns it comes down to how quickly can one replace 150 - 290 amps or so. Replenishing 200 amps is not too tough with FLAs and suitable alternators, generator run time and or solar.
But Rod is right when trying to replace 400 + amps into FLAs, it takes time. Herein lies the beauty of LFPs, they can recharge 400 + amps quickly for over a thousand cycles while drawing way down beyond what is sensible for FLAs.
One’s cruising style, curiosity, pocketbook and sense for innovation opens the door for pursuing new things technical. This is where Rod is, probing those boundaries and advancing his and our knowledge in useful ways.
SteveK
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Care to expand then on how long it would take?
Over the years many have replaced alternators to charge FLA faster. You are saying what appears to be fully charged is actually not fully charged.
ETA: I recall that FLA batteries charge to about 80% quickly. Also that it is suggested to discharge FLA to 50%. Therefore FLA operate between 50 & 80 most of the time.
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catalinajack
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Thanks all for your observations but I am still waiting for a definitive answer on how long it takes to charge a flooded battery to 100% from a 50% SOC. Of course it is dependent on the size of the bank and the charging sources. I stated earlier that my experience is 5.5 hours whether cruising or on shore power. My inverter-charger charges at 125 amps when in bulk. My two alternators (100 amp Balmars) put out 70 amps each when initially in bulk, so about the same. Time to charge to 100% is reported by three different monitors. Battery bank is 920Ah. I'd say that perhaps I am mistaken but I have observed and tested several times, all with the same result. I don't know what else to say.
I would do the test again but the boat has been sold, sale settled today.
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SteveK
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Jack, I am also waiting for some answer from CMS on this as he is the one dropping a bomb without explanation. I always thought a battery off the charger holding 12.6 or more is fully charged.
congrats on the sale.
congrats on the sale.
MacPhid
Senior Member
I would be interested to hear how a "charge cycle" is determined. Even in CMS's link the AGM battery he references the owner estimates 50 cycles. I would think amp hours withdrawn would be a better measure, something that can be shown in the history data of a Link Pro, BMV 712 etc. Our house bank reports less than 150 cycles after 7 years running over 1500 engine hours (3000+ anchored?) and 10,000 miles. Total amp hour draw over that time 33,000 amp hours out, 39,000 amp hours in.
I guess I'm surprised at how many seem to be guessing how many "cycles" they've got from a battery.
James
sunchaser
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Steve and CJ
If you go to the CMS website the logic will pop up on recharging FLAs. Rod is one of the true experts in all things marine battery related if you really have a desire for knowledge as opposed to internet nit picking on this subject email or contact him via website.
Expecting an open forum debate with the pros on social media is asking a bit much. TF has run away too many pros by sophomoric debates on a well established subject; in this case charging regimes and life cycles for marine batteries.
twistedtree
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Datasheets almost always spell this out. You are 100% correct that the REAL measure/determination is Ah throughput, not just cycles. At least as long as you operate the batteries correctly. If you abuse them, your abuse will determine their lifespan. As Rod (CMS) has pointed out, most boat batteries don't die because they wear out, but instead they are "murdered" through misuse.
Lifeline, for example, shows a graph of cycle life vs DOD. The deeper the discharge, the fewer cycles you get, and the shallower the discharge the more cycles you get. Other only show one or two data points rather than a full graph, but it's more characteristic of Lead/Acid, and much less about a particular battery.
LFP is the same. The baseline from a lot of research shows 2000-2500 cycles using 100% DOD. Nobody operates a boat battery that way, so cycle life will be commensurately higher. And if your system is set up correctly, LFP batteries are nearly impossible to murder.
SteveK
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James, why did you quote me, your post is valid but nothing to do with my post.
Sunchaser, if the expert does not want to explain, that is his choice, the question was not a debate but a request for enlightenment. expert or not we should not blindly accept without explanation.
Sunchaser, if the expert does not want to explain, that is his choice, the question was not a debate but a request for enlightenment. expert or not we should not blindly accept without explanation.
MacPhid
Senior Member
Apologies Steve, the connection was tenuous at best.
I was hoping CMS would define a charge cycle and fully charged characteristics as it refers to FLA, AGM and LFP. I don't doubt that a properly installed, used and maintained LFP will get substantially more cycles than an FLA or AGM, but the same holds true for the FLA and AGM, the key being properly installed, used and maintained. As someone quoted a battery doesn't normally die an early death, it's usually murdered. A battery that only lasts two years I suspect has been murdered.
James
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Resurrecting thread since it's been almost a year since you purchased the batteries. Any updates?
