it's time to upgrade the battery bank to start my 10Hp diesel and also run reasonable lights, VHF, (gps, etc. My 2 flooded cells are dead ( and I hate slogging 2 hrs each way to the yard to charge them and top them up in the dead of winter . ) I'm looking at the Renogy AGM s , 100 aH group 27 . ($200. ) as a house battery, more aH for the $ . ) I've had good luck w Optima blue Top but can't justify their high current price $$$ $320 . the Renogy Group 27 is $200 , only con Is it is pretty heavy at 62 # (same dimension as other group 27 's but a lot heavier.. . ) 'Bass pro ' got a great r review on some guy's website 'best marine batteries' but the reviews by actual owners said they were dreadful, didn't even last a season. So far in my last 2 decades of 3 different boats, I've had: Lifelines ($$$$, heavy, not any longer life than Deka -East Penn or Interstate; ) Optima which I loved BUT costs $$$ now. Renogy has a 3 yr guarantee on its AGM gels. but my charger setting says to put start gel only 1 battery type - either gel or a gm or flooded. so I guess I'd need need a gel start battery if I go with the Renogy. my boats are on the hard on the frozen shores of erie Oct. 10 April. ) . all thoughts welcome. . .
best 'dual purpose' AGMs , max Group 27, for start and house use ?
- Thread starter MitchM
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There is a direct relationship between battery weight and amphour capacity in lead acid batteries. The heavier the battery, the more lead, the more capacity.
Renogy receives mixed reviews, they are cheap and of questionable reliability. Basically, you get what you pay for. Mainsail did an evaluation of AGM batteries, his results are on his website www.MarineHowTo.com and in Practical Sailor. Reading his review will be more valuable than anecdotal stories on the web.
Renogy receives mixed reviews, they are cheap and of questionable reliability. Basically, you get what you pay for. Mainsail did an evaluation of AGM batteries, his results are on his website www.MarineHowTo.com and in Practical Sailor. Reading his review will be more valuable than anecdotal stories on the web.
You seem to be under the mistaken impression that weight is undesirable. Weight is lead which is amp hours. Not necessarily reliability, just amp hours.
I also steered away from Renogy for an AGM battery that I bought last year based on reputation. I was wondering why it is half the price of reputable brands like Odyssey & NorthStar. It appears that the 100 Ah is based on 10-hr capacity. The standard testing capacity is C-20 hr. It seems that advertising gimmicks may be at work. I'll agree with @Captain Larry-DH , you may not always get what you pay for, but for sure, you never (honestly) get what you don't pay for!
I'll agree with anybody who says that buying batteries is about the trickiest component that you can deal with on a boat! Just understanding who manufactures what is confusing. I bought an AGM battery from Batteries Plus with the brand name X2 Power. It turns out that X2 Power is a Batteries Plus exclusive brand manufactured by NorthStar, which is a subsidiary of EnerSys (who manufactures Odyssey deep cycle batteries for marine use). I found that the brands X2 Power, NorthStar, and Odyssey are basically identical batteries with varied graphics. The pricing of all 3 is virtually identical as well. I found Batteries Plus had a convenient location and lowest pricing (pricing differences were very small for these high-priced batteries). A Grp 27 90 Ah X2 Power costs $450. (That's about $70 higher than I paid last year, btw)
In reading some of Maine Sail's more recent postings, it seems that he recommends that there is no reason to consider AGM batteries when the additional expense for LiFePO4 is more economical in the long run and all-round better choice. I did see that X2 Power sells an 80 Ah LiFePO4 in Grp 27 size selling for $750. (Gives me direct pricing comparison between AGM & LiFePO4) Consider that the lithium battery is far less weight, almost double the capacity (AGM discharge is only 50%), and faster charging rate, the $300 purchase price differential is not looking so bad after all.
I'll agree with anybody who says that buying batteries is about the trickiest component that you can deal with on a boat! Just understanding who manufactures what is confusing. I bought an AGM battery from Batteries Plus with the brand name X2 Power. It turns out that X2 Power is a Batteries Plus exclusive brand manufactured by NorthStar, which is a subsidiary of EnerSys (who manufactures Odyssey deep cycle batteries for marine use). I found that the brands X2 Power, NorthStar, and Odyssey are basically identical batteries with varied graphics. The pricing of all 3 is virtually identical as well. I found Batteries Plus had a convenient location and lowest pricing (pricing differences were very small for these high-priced batteries). A Grp 27 90 Ah X2 Power costs $450. (That's about $70 higher than I paid last year, btw)
In reading some of Maine Sail's more recent postings, it seems that he recommends that there is no reason to consider AGM batteries when the additional expense for LiFePO4 is more economical in the long run and all-round better choice. I did see that X2 Power sells an 80 Ah LiFePO4 in Grp 27 size selling for $750. (Gives me direct pricing comparison between AGM & LiFePO4) Consider that the lithium battery is far less weight, almost double the capacity (AGM discharge is only 50%), and faster charging rate, the $300 purchase price differential is not looking so bad after all.
In short @MitchM , it seems that purchasing high-quality AGM batteries may not be the best option. If your priority is purchase-price, then find some good FLA batteries. If weight and performance is highest priority, then look at LiFePO4.
This is really over simplified. A standard OEM alternator will not last long due to the high charge acceptance rate of LFP batteries. The batteries will take as much current as the alternator will provide which will over heat the alternator and fry it. An high output externally regulated alternator is necessary which may also require the addition of a larger V-belt or installation of a serpentine belt kit.
The most important part of the LFP installation is the BMS for the batteries and their ability to communicate with each other. Less expensive LFPs often have an inferior BMS.
And finally, many pros recommend the use of a LA buffer battery connected to the LFPs by a battery to battery charger.
The cost of these modifications to a stock charging system can be quite high.
Agree with @Scott T-Bird and @dlochner on all points above, plus @MitchM mentioned in his OP that he's concerned with winter charging in a northern climate. Most LFPs shouldn't be charged below 32F (or severely limited in charge current). I don't know what he needs to run over the winter, but if he can let them sit without any load the LFP batteries will sit very comfortably with extremely low self-discharge if disconnected for the whole winter, without charging.
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Good observation. That’s weird though - lead acid usually has less capacity at higher discharge rates. If they have 100 AH at 10 hours the peukert exponent suggests they actually have a little more than that at the typical 20 hour rate.
Good points. In my case, I have an upgraded alternator, external regulator & serpentine belt kit already installed. I have decided to upgrade my AGM house bank to LiFePO4 once they are kaput. I have 2 4D size batts for house bank installed in 2015, so 8 seasons so far and still doing well as far as I can tell. Don't know when I will pull the trigger!
If @MitchM is not going to make that commitment to Lithium now, but may be thinking about it in the future, even more reason to get for now with FLA. AGM's still require a bit more attention to charging protocol than FLA, no? Spending money on good AGM batteries at higher price may not make sense.
If you have the space and want the biggest $$ for your buck, I am a fan of 2 six-volt golf cart batteries.
I picked up 2 of these Duracell branded (Deka mfg) golf cart batteries at Sam’s Club a couple of years ago. 215 AH at 12 volts.
I don’t remember what I paid for them, but a bargain I think for the capacity, and no charging system upgrades required. About as bullet proof ans simple as it gets.
Greg
I picked up 2 of these Duracell branded (Deka mfg) golf cart batteries at Sam’s Club a couple of years ago. 215 AH at 12 volts.
I don’t remember what I paid for them, but a bargain I think for the capacity, and no charging system upgrades required. About as bullet proof ans simple as it gets.
Greg