We have the usual setup on our Beneteau 323; there are 2 banks, one a house bank of 2x 80Ah group 24 agm batteries connected in parallel and a start bank of one 80Ah group 24 agm battery. At 9 years, they are approaching there end of life. Our power needs are pretty modest; refrigeration is the big draw and I leave it running full time when we are on the boat. I rely mostly on solar to charge. We have 260 watts from 2 flexible panels connected in series to a Victron mppt controller. In practice, I use the house bank for everything from starting the diesel, running the windlass and the house loads. When we are out for a few days, I find the batteries are usually on float by early afternoon, sometimes later if it is overcast. Bank 1 and 2 are connected in parallel, to the alternator but the battery charger charges both banks when connected to shore power. We have the original Xantrex 20 amp charger with no custom or lithium option. When I started looking to replace my batteries, I was surprised to see that I could buy a 100Ah LiTime or Wattcycle group 24 LiFepO4 for $60 less a piece than my original Nautilus agm batteries. So more power, less weight snd less money. I'm kind of torn because if I upgrade my charger for LiPO4 and add a dc to dc charger, I will have the the LiPO4 advantage but it will be another $1k on top of the cost of the batteries. More power would be nice. We have a little air conditioner for the dog that we run off a Jackery that I could run off an inverter instead and I have an ePropulsion outboard for the dinghy that it would be nice to supplement the solar charging after a few days of back and forth with the dog. I know the simple solution is just drop in new agms but it's tough to spend more for older, heavier technology. I really think the Xantrex charger on one of the agm settings would be OK for a LiPO4 house bank but both LiTime and Wattcycle said no.
Thoughts on replacing 9 year old agm batteries on a B323
- Thread starter Phil Mac
- Start date
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,746
9 years on an AGM battery, that is damn good.
Your house bank has two AGM 80Ah batteries that means you have about 100-120. amp hours of power. Two of Wattcycle 100Ahr mini batteries (20 lb a piece at about $400 usd perhaps less if on sale) will give you 140-150 amp hours of usable power. The solar can be used to charge the LI batteries. The BMS on the batteries is great with bluetooth app to monitor each battery. You can get a simple FLA froup 24 battery to serve as the starter battery. It will buffer (protect) the alternator from shut down power spikes, and can be connected to the LI bank to provide charging help via a DC to DC charger. Victron makes one. Your house bank has two AGM 80Ah batteries, that means you have about 100-120 amp hours of power. Two of Wattcycle 100Ahr mini batteries (20 lb a piece at about $400 USD, perhaps less if on sale) will give you 140-150 amp hours of usable power. The solar can be used to charge the LI batteries. The BMS on the batteries is great with a Bluetooth app to monitor each battery. You can get a simple FLA Group 24 battery to serve as the starter battery. It will buffer (protect) the alternator from shut-down power spikes, and can be connected to the LI bank to provide charging help via a DC to DC charger. Victron makes one.
Victron also makes some inexpensive plug in chargers when you have AC power to the boat.
Victron Energy Blue Smart IP67 Smart Marine Battery Charger 12V 25A, Float & Trickle Charger and
Desulfator for Boat, ATV, RV, Lithium and Deep Cycle Batteries
That only leaves you looking for an inverter if it is needed on your boat.
I bought 3 of the Watt batteries last November. They are going on the boat this season.
Your house bank has two AGM 80Ah batteries that means you have about 100-120. amp hours of power. Two of Wattcycle 100Ahr mini batteries (20 lb a piece at about $400 usd perhaps less if on sale) will give you 140-150 amp hours of usable power. The solar can be used to charge the LI batteries. The BMS on the batteries is great with bluetooth app to monitor each battery. You can get a simple FLA froup 24 battery to serve as the starter battery. It will buffer (protect) the alternator from shut down power spikes, and can be connected to the LI bank to provide charging help via a DC to DC charger. Victron makes one. Your house bank has two AGM 80Ah batteries, that means you have about 100-120 amp hours of power. Two of Wattcycle 100Ahr mini batteries (20 lb a piece at about $400 USD, perhaps less if on sale) will give you 140-150 amp hours of usable power. The solar can be used to charge the LI batteries. The BMS on the batteries is great with a Bluetooth app to monitor each battery. You can get a simple FLA Group 24 battery to serve as the starter battery. It will buffer (protect) the alternator from shut-down power spikes, and can be connected to the LI bank to provide charging help via a DC to DC charger. Victron makes one.
Victron also makes some inexpensive plug in chargers when you have AC power to the boat.
Victron Energy Blue Smart IP67 Smart Marine Battery Charger 12V 25A, Float & Trickle Charger and
Desulfator for Boat, ATV, RV, Lithium and Deep Cycle Batteries
That only leaves you looking for an inverter if it is needed on your boat.
I bought 3 of the Watt batteries last November. They are going on the boat this season.
Thanks. I was surprised at the current price of lithium batteries and unhappy that the agms have just gone up. I find the solar does a really good job of maintaining the house batteries. I don't run the engine to charge the batteries so it's either solar or shore power and since we don't leave anything running when we are off the boat, the primary function of the battery charger is to maintain the start/emergency battery. I'm really happy with the combination of my Ecoworthy panels in series and the Victron controller. When I get up in the morning it's. nice to see the batteries are already charging after sitting all night.
Don't be deceived by appearances. The solar is doing OK because the batteries are old and have lost a lot of capacity.
Your solar array is good for about 750 Wh a day on average. The power they produce will be more efficiently used by the LFP batteries because of the flat charge/discharge curve. The panels on Second Star now rarely go into float or absorbtion because the LFP batteries can accept all the power they are making.
There is lots of misinformation and incomplete information out there on LFP batteries. For a simple system that might meet your needs take at look the article below by Rod Colllins. It does have limitations, especially for longer term cruising, however for many of us it will be fine. While you are on the site take a look at the other articles on electrical and other boat systems. All good reliable information.
Easy LiFePo4 Conversion - Marine How To
Easy LiFePo4 Conversion Before reading this article please read the 101 article on Drop-In's: Drop-In Batteries Be An Educated Consumer Hardly a day goes by where we don't see or hear
marinehowto.com
You can use an older charger with AGM/gel settings for LFP, but you have to monitor it and turn it off when the batteries are fully charged. You can't rely on the absorbtion or float stages.
The Marine How To article @dlochner quoted is the easiest and cheapest way to convert, but even that does require some extra components.
The Marine How To article @dlochner quoted is the easiest and cheapest way to convert, but even that does require some extra components.
Thanks. I will have a look at the article. Our usual trips out are 4 or 5 days at anchor and maybe one extended cruise in a season. We can only lean on our neighbours to look after our house for so long 
I was hoping for shortcuts but I know that it isn't really likely. I am upgrading my solar this year to 2x200 watts with a 100/30 Victron charge controller so it would be awesome to have LiFePO4 to take advantage of the extra power. I swapped out all of our lighting for LEDs but we carry a 1000Wh Jackery power pack to pick up spare charging, run the little ac unit from time to time and boost the outboard battery if the folding solar panel on the dinghy doesn't keep up with our trips ashore, especially with a busy dog. It would be nice not to have to bother with the Jackery and save it for home use. It's hard to justify spending more on agm batteries for less power and more weight. Appreciate the input.
I was hoping for shortcuts but I know that it isn't really likely. I am upgrading my solar this year to 2x200 watts with a 100/30 Victron charge controller so it would be awesome to have LiFePO4 to take advantage of the extra power. I swapped out all of our lighting for LEDs but we carry a 1000Wh Jackery power pack to pick up spare charging, run the little ac unit from time to time and boost the outboard battery if the folding solar panel on the dinghy doesn't keep up with our trips ashore, especially with a busy dog. It would be nice not to have to bother with the Jackery and save it for home use. It's hard to justify spending more on agm batteries for less power and more weight. Appreciate the input.There is a short cut, you can just replace your house bank (with a class T fuse).
Keep your AGM start battery, and rewire a bit so that your alternator only charges the start battery and your solar/shore only charges your house bank This is step 1 and step 2 as described in the article. Essentially you isolate your engine start/charging system to itself. This eliminates the biggest cost issues of LFP incompatibility with older alternators. You don't even really need the fancy dual circuit combiner switch in the article, you just need a second battery disconnect of some sort, but the dual circuit switch isn't frightfully expensive.
It's not perfect, as without a dc-dc converter you can't reliably charge your house bank with the alternator. You can, in an emergency, if you keep a close eye on the charge state and alternator temperature. You can, in an emergency, combine your LFP and start battery which should charge the AGM enough to start.
Since you are upgrading your solar and your battery capacity it might work just fine for you as two separate systems.
Good point. I hadn't thought to notify my insurance company. That might be a good place to start.
The battery banks are wired in parallel to the alternator so depending on which bank you choose, the alternator only charges the bank selected. I generally just use the house bank all of the time and the start battery is a spare/emergency start.. Right now, the shore charger is wired to both but my solar only charges the house bank.
If you go with LFP, you'll want to change this because your internally regulated alternator will not last long when connected to the LFP batteries. The charge profile for the typical stock alternator has a bulk and absorption voltage of 14.4v which is too high for most LFP batteries, which generally want a 14.2v or lower charge voltage.
The shore power charger also needs to have a LFP setting for a similar reason. The AGM settings are too high and they have a float stage. LFP batteries generally don't like to be floated. The BMS may be able to take the batteries offline into a "standby" status when fully charged, mine do. This occurs when there is still a charging voltage present and there is a load on the system as might happen when motoring for a long distance.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,746
Be prepared to deal with their demand for a marine electrician needed to do the installation.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,746
Explore the limits of your LI battery bank. There are reported issues regarding the use of LI battery banks as starter batteries.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,746
Will you be planning to sail in the Pacific Northwest during the winter months? Not all LI batteries work well when the weather turns cold. Some have separate heating elements for the batteries when the temperatures drop below freezing. Additionally, when there is solar power to charge the batteries, if the batteries are at a below-freezing temperature, things may not go smoothly.
Yes, that's been one of my considerations. I could theoretically use a lead acid battery as a start and switch to the house bank when the boat is anchored if the house banks were lithium but that's kind of opposite to what we do now where I just use the house bank for everything. I was hoping I could just use my Xantrex charger set to agm on warm and 2 stage charging for both banks if I add lithium house batteries but both LiTime and Wattcycle said no to that. I appreciate that the charge profiles are different but I had assumed that if the vast majority of the charging was from solar, it would be OK. I don't mind wiring in a DC to DC charger. I had thought I might just use one of the LiTime 20 Ah starting batteries and wire in a DC to DC charger to protect the alternator but LiTime said it wasn't approved for a diesel inboard. I have the stock alternator so I have no doubt that a lithium battery would smoke it in no time.
I sail on Lake Ontario and the 1000 islands. Generally by the time the temps get too low, we are ending our season although I can recall more than a few late October days with frost. It gets cold here in spring and fall. We launch May 7th which seems close since my pool is still under a layer of ice and my lawn is still covered in snow. More than a few of our boats get towed to the haulout spot in spring and late fall when the diesels won't turn over.
For the casual coastal cruiser, I can’t see the financial justification for LFP conversion.
Mainail’s recommended additions & modifications to the electrical system including battery switch, charger, alternator/controller, batteries, etc + labor costs a few thousand. On the other hand, if you’re a full time cruiser, I can appreciate the benefits.
I would replace the AGMs with Gp 31 (105 amps ea.) FYI, Duracells from Sam’s club @ $215 ea. have worked well for me.
Mainail’s recommended additions & modifications to the electrical system including battery switch, charger, alternator/controller, batteries, etc + labor costs a few thousand. On the other hand, if you’re a full time cruiser, I can appreciate the benefits.
I would replace the AGMs with Gp 31 (105 amps ea.) FYI, Duracells from Sam’s club @ $215 ea. have worked well for me.
I am going to contact my insurance company today and ask. I'm at a sailing club, not a marina so that will be a complicating factor even ignoring the cost.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,746
My bad, I got confused. The idea of LI batteries on a boat is a popular subject.
I have been finding my way through the weeds of this transition to LI and the use of Solar. Your solar performance may be better than we typically see in our waters. That said, there are many advantages. Esthetically, I find the boat coverd with solar panels a bit of an eyesore. Just seems to be one of the boating compromises.
I ask myself, do I really need all this electricity.
I have been finding my way through the weeds of this transition to LI and the use of Solar. Your solar performance may be better than we typically see in our waters. That said, there are many advantages. Esthetically, I find the boat coverd with solar panels a bit of an eyesore. Just seems to be one of the boating compromises.
I ask myself, do I really need all this electricity.