Let’s see how quickly I regret making this post.

[Putt-Putt]

The 2 100Ah batteries that you just referenced differ in height only. The first one with its bluetooth is 1" higher.

Neither are close to the dimensions of a Group 31 battery, despite the fact that you called one of them a Group 31 battery.

That in your case is not unusual as you also called a battery that is bigger than a Group 31, a Group 24.

Finally, I have no idea how to answer "What do you think I posted the shot showing its measurements." other than to say, bottoms up.

[newhaul]

Originally Posted by Putt-Putt

The 2 100Ah batteries that you just referenced differ in height only. The first one with its bluetooth is 1" higher.

Neither are close to the dimensions of a Group 31 battery, despite the fact that you called one of them a Group 31 battery.

That in your case is not unusual as you also called a battery that is bigger than a Group 31, a Group 24.

Finally, I have no idea how to answer "What do you think I posted the shot showing its measurements." other than to say, bottoms up.

Ok john I don't really see any meaningful input from you.
I'm posting from the hospital most days as my wife battles cancer so try to be nice .

Also they both are the sizes I stated they are sorry it's not in your preferred mm

[Putt-Putt]

Well I know first hand that the trials and tribulations of a wife's Cancer diagnosis can certainly cloud one's judgement, as 15 years ago it did mine.

I wish all the best for you and your wife's journey through your present challenges and trust that as my wife and I have done, you two will both survive and flourish.

I'm at a loss as to why you referred to me as john.

[newhaul]

Originally Posted by Putt-Putt

Well I know first hand that the trials and tribulations of a wife's Cancer diagnosis can certainly cloud one's judgement, as 15 years ago it did mine.

I wish all the best for you and your wife's journey through your present challenges and trust that as my wife and I have done, you two will both survive and flourish.

I'm at a loss as to why you referred to me as john.

Slip of the fingers on my phone's keyboard. I suppose

[s/v Jedi]

Okay, my recommendations:

- battery: 2x LiTime 140Ah Bluetooth enabled group 31: https://www.litime.com/products/12v-...ithium-battery
They sell two for $490 total but you can find additional discount codes easily… expect another 8% off.

- solar: choose from this range of Victron SmartSolar MPPT controllers: https://www.victronenergy.com/solar-...-100-15-100-20
I recommend you keep using two controllers. Set the absorption voltage to 14.4V as recommended by the manufacturer.

- alternator regulator: if yours is programmable, set it to an absorption voltage of 14.2V which is the manufacturer recommended minimum voltage.

- float voltage: for both solar and alternator set float voltage to 13.6V and use the Bluetooth app to see if they discharge a little in float. This is what you want.

Installation: connect battery positive terminals to #1 and #2 positions of this switch: https://www.bluesea.com/products/600...y_Switch_-_Red
This will be both the main battery switch for the bank as well as an isolation switch so you can use only one when there is a problem with the other one.

After that switch you need a fuse, I expect you already have one but you may want to upgrade to a class-T fuse.

[newhaul]

Originally Posted by s/v Jedi

Okay, my recommendations:

- battery: 2x LiTime 140Ah Bluetooth enabled group 31: https://www.litime.com/products/12v-...ithium-battery
They sell two for $490 total but you can find additional discount codes easily… expect another 8% off.

- solar: choose from this range of Victron SmartSolar MPPT controllers: https://www.victronenergy.com/solar-...-100-15-100-20
I recommend you keep using two controllers. Set the absorption voltage to 14.4V as recommended by the manufacturer.

- alternator regulator: if yours is programmable, set it to an absorption voltage of 14.2V which is the manufacturer recommended minimum voltage.

- float voltage: for both solar and alternator set float voltage to 13.6V and use the Bluetooth app to see if they discharge a little in float. This is what you want.

Installation: connect battery positive terminals to #1 and #2 positions of this switch: https://www.bluesea.com/products/600...y_Switch_-_Red
This will be both the main battery switch for the bank as well as an isolation switch so you can use only one when there is a problem with the other one.

After that switch you need a fuse, I expect you already have one but you may want to upgrade to a class-T fuse.

He will need to keep a lead based start battery and in my opinion he should run the 200 watts solar to that battety and run a small say 10 amp dc2dc to the lifepo4.
Yes his balmar regulator is programable to charge the lifepo4 house.

[s/v Jedi]

Originally Posted by newhaul

He will need to keep a lead based start battery and in my opinion he should run the 200 watts solar to that battety and run a small say 10 amp dc2dc to the lifepo4.
Yes his balmar regulator is programable to charge the lifepo4 house.

Wait, is one of the two batteries the start battery? That means he would only have had 100Ah house bank? I find that hard to believe…

Anyway, my recommendation is as it stands above: if one of the two was a start battery then I recommend a third battery as start battery, using any maintenance free lead acid start battery. And yes, in that case I recommend to charge the start battery with current alternator settings and use the new Victron 50A DC-DC converter to charge the house bank from the alternator, not the other way around.

[newhaul]

Originally Posted by s/v Jedi

Wait, is one of the two batteries the start battery? That means he would only have had 100Ah house bank? I find that hard to believe…

Anyway, my recommendation is as it stands above: if one of the two was a start battery then I recommend a third battery as start battery, using any maintenance free lead acid start battery. And yes, in that case I recommend to charge the start battery with current alternator settings and use the new Victron 50A DC-DC converter to charge the house bank from the alternator, not the other way around.

I am assuming one or both of his agm are set as a start battery.
Yes a grp 24 maintance free lead for start and 2 100 ah lifepo4 for house.
( never heard anyone say they had to much power)

That setup would require2 new solar controllers.

Setting his balmar to charge the lifepo4. And the 200 watts solar to charge the start battery and run a 10 amp dc2dc from start to house . This would be the cheaper way to setup everything.

I have seen several brands of 10 amp dc2dc for under $100 USD.

[lateral]

Originally Posted by Cthoops

We have been living and cruising on our 30’ sailboat since August, 2018. About six months before we left, we installed two Firefly batteries and have ignored them ever since. Time marches on, however, and it looks like we may need to install new batteries soonish.

Unfortunately for us, Firefly batteries shot themselves in the foot with quality control issues and are no longer an option. We are 100% set it and forget it people when it comes to batteries. The subject of electricity is not our strong suit. We’ve lightly researched going with Lithium but they strike us as a bit more complex than we prefer. Plus, we may buy a larger (38 foot maximum) boat in the future so we aren’t sure we want to go down the road of the all-in expenses of lithiums.

We have minimal needs when it comes to electricity. Our boat is 100% 12-volt, we don’t have shore power capability, and although I don’t have our 24 hour usage in front of me, I’m pretty sure I recall that we use a maximum of 30 ah every 24 hours when we aren’t on a passage. It jumps up on a 24+ hour passage because of the instruments.

Having said that, if we bought 2, 100A AGM batteries, and they are kept charged by 2, 100W solar panels plus a 70 amp alternator when we are motoring, how long could we expect them to last? I know they won’t handle a partial state of charge as well as our Firefly batteries do, but they won’t be drawn down much at all. We typically cruise up and down the US East Coast and winter in the Bahamas. Or should we suck it up and deal with the learning curve and higher maintenance of lithiums? Thanks.

For LiFePO4, I like the backup of a fast charging alternator for those cloudy days. The balmar 70A is ok at 77A cold and 65A hot . (60°C) that is only 1hr charging from 66% SOC to full for 200Ahr Li.
I like cost effective so went with the forced external air Bosch alternator off Porsche as it fits Yanmar mount easily and can run 90-100A without wearing out V belts or overheating and derating. A fraction of the cost of the Balmar. Minor mods needed to externally regulate-no soldering or opening the case as VR is external screw on!(you should service a used alt anyways)

You have to define the constraints of your boat to find line of least resistance,
but that meets your needs.
I will never go back to FLA's for house , perhaps SLA's for the start batterys.
We use ~100Ahr/day sailing so have a 460Ahr 4S2P battery with 2xbms.
You might have to climb the curve!

[Cthoops]

This is all very helpful, everyone. Thank you!

We do not have a separate start battery. The two Fireflys are it. I think after reading everyone's posts we have decided to go with the lithium instead of more AGM's. I'm sure I'll be posting more questions once we get ready to order and install. Thanks again for the input!

[newhaul]

Originally Posted by Cthoops

This is all very helpful, everyone. Thank you!

We do not have a separate start battery. The two Fireflys are it. I think after reading everyone's posts we have decided to go with the lithium instead of more AGM's. I'm sure I'll be posting more questions once we get ready to order and install. Thanks again for the input!

Happy to help any way I can shoot me a pm

[Cthoops]

Originally Posted by newhaul

Happy to help any way I can shoot me a pm

Will do!

[SVTatia]

I think you should review your electrical budget before making a decision. The Engel alone prolly needs 4ah yes? That multiplied by 24... plus lights, device charging, etc.
In any case you don't need much and you now have 100ah from the current bstteries, so a 200 ah lithium will almost double that.

My electrical needs are very similar to yours, and I am going hybrid, a lead acid for the engine and 200ah lithium for the house.

[newhaul]

Originally Posted by SVTatia

I think you should review your electrical budget before making a decision. The Engel alone prolly needs 4ah yes? That multiplied by 24... plus lights, device charging, etc.
In any case you don't need much and you now have 100ah from the current bstteries, so a 200 ah lithium will almost double that.

My electrical needs are very similar to yours, and I am going hybrid, a lead acid for the engine and 200ah lithium for the house.

Actually no the Engel would not be 4amp x24hours constant running = 96ah
More like 4amp x12 50% duty cycle = 48ah
Or my technautics about 5amps x 2 3 hour runs a day or 5amp x 6 hours = 30ah
The main mistake people make is thinking in always on when it's not how it is real world.

The op is basing his daily usage on his current bank size and usage.

[SVTatia]

Originally Posted by newhaul

Actually no the Engel would not be 4amp x24hours constant running = 96ah
More like 4amp x12 50% duty cycle = 48ah
Or my technautics about 5amps x 2 3 hour runs a day or 5amp x 6 hours = 30ah
The main mistake people make is thinking in always on when it's not how it is real world.

The op is basing his daily usage on his current bank size and usage.

Of course, you are right and I stand corrected. Although the brochures say the Engel consumes 1 point something, in real life its more, specially in the tropics, but I always round up, hence the 4ah. But even if its 3, that is still 36 amps in one day.