The batteries pictured are Rolls S6 250 flooded cells, nominally 281 a/hr. They came with the boat and are of unknown age but currently seem to work OK. They are not the cell I would pick as they are a lightweight battery. The clue is that the spec sheet gives a CCA number. True deep cycle cells don't have that. The taller L16-EX is rated at three times the cycle life, about 3,750 cycles to 50% DoD compared to these at 2,000. You really do need to look at the full spec to know what you are getting! In Canada these are currently around $320 com-pared to the L16 at $590. The black battery is the starter battery which is a simple H/D car battery that starts the engine and supplies the windlass. (Photo/ Roland Stockham)
Replacing a battery bank on a cruising sailboat requires a myriad of choices—driven by one overriding goal. What are you hoping to power with your new capability? And what's the best way to get there?
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Selecting the battery chemistry is just the beginning. You also need to consider the rest of the electrical system that supports it. My approach has been contrary to what is popular…that is, to minimize my electrical needs or KISS (Keep It Simple Stupid). My initial batteries were 2x8D GEL and lasted 15 years including a roundtrip to Hawaii without having to run the diesel for charging…the boat has 560W of solar. When I replaced them in 2019, I considered alternatives but went with my wining experience, Gel again.
Not sure where you are getting your cost comparisons… I just checked Renogy, a 100Ah LiFePO4 battery is $300, and can be discharged to very low capacity. A flooded 200Ah battery at Amazon (since you want to discharge to no less than 50%) is $355. While that’s is a bit more capacity to use (LiFePO4 should not go down to 0), it’s very much in the same range.
Another consideration. Who can guarantee that their bank will never be totally discharged by accident. All it takes is a careless passerby at the dock for your electrical connection to be cut off, resulting in a huge loss of lifetime for the bank. Lithium gives great peace of mind in this respect.
Great article Roland. You provided a nice comparison of the options and things to consider. I have a LA system currently with two 6V Trojan T105 house batteries that are approaching their end of life (they were purchased in 2016). I have been thinking of replacing them with Lithium but this will require many expensive upgrades to my current system. To date, the LA battery system has served me well. Your article has been great in helping me evaluate my alternatives. Cheers
I was hugely disappointed the PS would even publish this without more thoroughly checking the facts presented. Firefly does not exist anymore in any practical sense due to problems with their products and lack of response from the company. The information on lithium is so out of date it does not even make any sense today especially in regards to pricing and skills needed to install. This misleading column might seriously lead someone new to sailing to make totally wrong decisions in setting or improving a battery bank.
Good article and seemingly a through examination of the different chemistries, although I believe that Firefly is currently gone. 5 yrs. ago I got a new (to me) 40′ cat. For the house, I replaced the two automotive FLAs with 4-120AH LifePo4’s. They are charged exclusively by 500W solar. There is a 2500W inverter, with microwave, 42″ flatscreen and 110V refrig (7 cu. ft.) as the main big draws, plus autopilot and chartplotter when moving. Water heating is on-demand propane. All internal and external lights are LED. Occasionally there is some “boat project” requiring a 110V circular saw (15A), jig saw (5A), heat gun (15A), etc. There is also a 1500W pressure washer that I use every couple of months for an hour or so, which pulls the batteries down to 60-70% and they recover by the next day. Cost for the batteries with internal BMS was $400 each (5 yrs. ago) direct from the Chinese factory and that included $100 apiece for air freight. Prices have since come waaaay down since, to where they are advertised for $100-$200 for 100ah. The batteries so far have operated flawlessly, they just sit there and put out, no maintenance. I periodically open the hatch and look to see if they are really there and clean the dust off the tops. We are not liveaboards, mostly day sailors, with a couple of weeks a year at Catalina, but even then, the batteries recover the next day, or day after if it’s particularly cloudy. They never need shore power or engine charging, just solar.
A couple of explanations. Carbon foam batteries are still on sale in Canada but as ‘discontinued’ items with no warrentee. (They were still listed when I wrote the article.) It is an interesting technology but I apologize for being a little out of date on this one
I did make clear in the article that I wanted to compare like with like, so for price comparisons I only including premium North American battery suppliers. Yes you can get cheaper lithium batteries from China which may be a good deal or may not. I suggest you look very carefully at both the type and grade of cells and the BMS on these. I do buy stuff from China and have had some excellent deals but it is very much a ‘buyer beware’ situation and warranties may be useless. I would not consider it a good comparison to put against a manufacturer like Rolls or interstate
I was close to going ahead with a LiFePO4 battery replacement project last week for my three existing Firefly batteries. I pulled the plug definitively on this after double-checking with my insurer. I was advised that the underwriter is no longer issuing or renewing insurance for boats with lithium batteries due to the fire concern. Probably there are other underwriters out there, but my broker thinks it’s only a matter of time until they all pull insurance on Li (this is in Canada; I have no idea whether the US industry will be similar). While I appreciate the distinction of the FePO4 variant of lithium chemistry, it’s not clear the insurance industry will do that. Also, give your head a shake before installing a low-cost, Chinese Li battery in a boat. Fine for your bicycle, maybe even a car, but you risk death if that catches fire on the water, whether cruising or at anchor. The fire cannot be extinguished – the boat will be lost for sure.
Also, the technical challenges of this switch were a little greater than mentioned here. For example, my older inverter-charger would have had to be changed to an updated one to handle the different voltage profile of the Li chemistry, along with a new battery monitor, upgraded cabling, etc. Ka-ching, ka-ching. I’m pretty handy and have rewired my own house without any worries, and no concerns about wiring the 12V system in my boat, but I would be leery of messing something up for a Li installation in a boat due to the fire concern, burning out the alternator, etc. All in with professional installation, quality batteries and all the additional gear required this was going to be a C$7,000 to C$10,000 project for 3 x sched 31 LiFePO4 batteries. Less in US$, I know, but still pricey for what you get.
Selecting the battery chemistry is just the beginning. You also need to consider the rest of the electrical system that supports it. My approach has been contrary to what is popular…that is, to minimize my electrical needs or KISS (Keep It Simple Stupid). My initial batteries were 2x8D GEL and lasted 15 years including a roundtrip to Hawaii without having to run the diesel for charging…the boat has 560W of solar. When I replaced them in 2019, I considered alternatives but went with my wining experience, Gel again.
Not sure where you are getting your cost comparisons… I just checked Renogy, a 100Ah LiFePO4 battery is $300, and can be discharged to very low capacity. A flooded 200Ah battery at Amazon (since you want to discharge to no less than 50%) is $355. While that’s is a bit more capacity to use (LiFePO4 should not go down to 0), it’s very much in the same range.
Another consideration. Who can guarantee that their bank will never be totally discharged by accident. All it takes is a careless passerby at the dock for your electrical connection to be cut off, resulting in a huge loss of lifetime for the bank. Lithium gives great peace of mind in this respect.
Great article Roland. You provided a nice comparison of the options and things to consider. I have a LA system currently with two 6V Trojan T105 house batteries that are approaching their end of life (they were purchased in 2016). I have been thinking of replacing them with Lithium but this will require many expensive upgrades to my current system. To date, the LA battery system has served me well. Your article has been great in helping me evaluate my alternatives. Cheers
I was hugely disappointed the PS would even publish this without more thoroughly checking the facts presented. Firefly does not exist anymore in any practical sense due to problems with their products and lack of response from the company. The information on lithium is so out of date it does not even make any sense today especially in regards to pricing and skills needed to install. This misleading column might seriously lead someone new to sailing to make totally wrong decisions in setting or improving a battery bank.
Good article and seemingly a through examination of the different chemistries, although I believe that Firefly is currently gone. 5 yrs. ago I got a new (to me) 40′ cat. For the house, I replaced the two automotive FLAs with 4-120AH LifePo4’s. They are charged exclusively by 500W solar. There is a 2500W inverter, with microwave, 42″ flatscreen and 110V refrig (7 cu. ft.) as the main big draws, plus autopilot and chartplotter when moving. Water heating is on-demand propane. All internal and external lights are LED. Occasionally there is some “boat project” requiring a 110V circular saw (15A), jig saw (5A), heat gun (15A), etc. There is also a 1500W pressure washer that I use every couple of months for an hour or so, which pulls the batteries down to 60-70% and they recover by the next day. Cost for the batteries with internal BMS was $400 each (5 yrs. ago) direct from the Chinese factory and that included $100 apiece for air freight. Prices have since come waaaay down since, to where they are advertised for $100-$200 for 100ah. The batteries so far have operated flawlessly, they just sit there and put out, no maintenance. I periodically open the hatch and look to see if they are really there and clean the dust off the tops. We are not liveaboards, mostly day sailors, with a couple of weeks a year at Catalina, but even then, the batteries recover the next day, or day after if it’s particularly cloudy. They never need shore power or engine charging, just solar.
A couple of explanations. Carbon foam batteries are still on sale in Canada but as ‘discontinued’ items with no warrentee. (They were still listed when I wrote the article.) It is an interesting technology but I apologize for being a little out of date on this one
I did make clear in the article that I wanted to compare like with like, so for price comparisons I only including premium North American battery suppliers. Yes you can get cheaper lithium batteries from China which may be a good deal or may not. I suggest you look very carefully at both the type and grade of cells and the BMS on these. I do buy stuff from China and have had some excellent deals but it is very much a ‘buyer beware’ situation and warranties may be useless. I would not consider it a good comparison to put against a manufacturer like Rolls or interstate
I was close to going ahead with a LiFePO4 battery replacement project last week for my three existing Firefly batteries. I pulled the plug definitively on this after double-checking with my insurer. I was advised that the underwriter is no longer issuing or renewing insurance for boats with lithium batteries due to the fire concern. Probably there are other underwriters out there, but my broker thinks it’s only a matter of time until they all pull insurance on Li (this is in Canada; I have no idea whether the US industry will be similar). While I appreciate the distinction of the FePO4 variant of lithium chemistry, it’s not clear the insurance industry will do that. Also, give your head a shake before installing a low-cost, Chinese Li battery in a boat. Fine for your bicycle, maybe even a car, but you risk death if that catches fire on the water, whether cruising or at anchor. The fire cannot be extinguished – the boat will be lost for sure.
Also, the technical challenges of this switch were a little greater than mentioned here. For example, my older inverter-charger would have had to be changed to an updated one to handle the different voltage profile of the Li chemistry, along with a new battery monitor, upgraded cabling, etc. Ka-ching, ka-ching. I’m pretty handy and have rewired my own house without any worries, and no concerns about wiring the 12V system in my boat, but I would be leery of messing something up for a Li installation in a boat due to the fire concern, burning out the alternator, etc. All in with professional installation, quality batteries and all the additional gear required this was going to be a C$7,000 to C$10,000 project for 3 x sched 31 LiFePO4 batteries. Less in US$, I know, but still pricey for what you get.