Finished my 280Ah @24v marine battery installation

[TimE]

Finally got my 8no CATL 280Ah cells installed in my boat. The system is complete with JK BMS, Victron Smart shunt and Class T fuse. I used 1" cutting board as compression plate material and 6no stainless steel threaded rods.
Plastic hydraulic pipe covers the threaded rod. I fitted stainless steel eye bolts to the floor of the battery box and used webbing to attach to the eyebolts with small shackles. To tension the webbing with used 1.5mm dyneema kite lines as a lashing. This worked well.
We have 720w of solar on a 44ft monohull.
We have bean running the system for the last 10 days in the Caribbean. We have not used any propane to cook with apart from on the oven. We are using an electric kettle, induction hob, immersion heater for hot water and running the 220v watermaker with 1.9kw load all through the 3kw inverter. We haven't used the diesel generator at all. All power has come from 720w of solar plus a wind turbine.
Our daily harvest is just under 4kw with the wind turbine contributing a little bit more. We have kept our 4no Trojan t105RE batteries for now so we have a back up but we will ditch those in the future for a second smaller lithium bank of 8no 120Ah (or there abouts) cells and a seperate BMS

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[sunshine_eggo]

anything between the cells?

Keeping FLA as "backup" is only useful if the FLA is kept on float. Ideally, you want to keep them floated at 6.60V in parallel. The power required to keep them floated at 100% should be < 10W. I have larger Rolls S-605 (6V, 468Ah), and they only need about 6W to keep them floated.

 

[TimE]

anything between the cells?

Keeping FLA as "backup" is only useful if the FLA is kept on float. Ideally, you want to keep them floated at 6.60V in parallel. The power required to keep them floated at 100% should be < 10W. I have larger Rolls S-605 (6V, 468Ah), and they only need about 6W to keep them floated.

The Trojans are kept on float with a Victron MPPT as per manufacturers float recommendations. The generator battery alo under the same set up. A third Victron MPPT provides charging from the engine battery when the engine is running.
The Trojans also have Victron battery balancers and Sterling desulphators installed from new

 

[sunshine_eggo]

The Trojans are kept on float with a Victron MPPT as per manufacturers float recommendations.

The generator battery alo under the same set up.

Powered by PV or a continuous source? If PV, I would allow a brief daily absorption with their adaptive algorithm.

A third Victron MPPT provides charging from the engine battery when the engine is running.

An actual MPPT or a DC-DC?

The Trojans also have Victron battery balancers and Sterling desulphators installed from new

Nice!

 

[TimE]

Powered by PV or a continuous source? If PV, I would allow a brief daily absorption with their adaptive algorithm.



An actual MPPT or a DC-DC?



Nice!

Sorry, B2B not MPPT?

 

[E. Cho]

Looks great. What wire size did you customize from your JK BMS to negative and as your battery positive?

For even lower energy consumption, I use an 3L Instant Pot Duo pressure cooker for much of my cooking, although I'm not on a boat. The Instant Pot greatly reduces my use of the induction hot plate and the energy use is much more direct and efficient as less is lost to ambient surroundings. Often I pre-cook one thing for X minutes, release the pressure, then add other foods to cook and restart at a lowered time and this 2nd addition takes very little energy to get back up to pressure as it already has nearly boiling hot water inside.

The smallest Instant Pot pressure cooker is large enough for 2 people and draws a max of 670 Watts but only long enough to build up pressure by boiling the water (usually 5-8 minutes if water starts near 20 deg C), then uses short energy draws if pressure is needed to be maintained. I can reduce the energy use of the Instant Pot even further by reducing the boil to pressure time, by using pre-heated water either from my wood stove or even water that was sitting in a black container in the sun when it's too warm to use the wood stove. The Instant Pot is really useful for me to use for cooking some foods ahead of meals when the sun is shining, and to then leave them in the Instant Pot to cook using barely any energy at all to maintain pressure. The downside, is that it might be awkward to secure in use on a moving boat but might be worth the effort due to the energy savings.

Instant Pot pressure cookers can be found for really low cost used as many people give up on them or Amazon or Walmart often have 50% off sales for new. One does not need the fanciest model which are fancy only because of more "pre-set timers" for specific foods. Really one could get away with just one pre-set button, such as the Pressure Cooking button, for cooking and then the up down buttons for pressure levels and or time.

 

[TimE]

Looks great. What wire size did you customize from your JK BMS to negative and as your battery positive?

For even lower energy consumption, I use an 3L Instant Pot Duo pressure cooker for much of my cooking, although I'm not on a boat. The Instant Pot greatly reduces my use of the induction hot plate and the energy use is much more direct and efficient as less is lost to ambient surroundings. Often I pre-cook one thing for X minutes, release the pressure, then add other foods to cook and restart at a lowered time and this 2nd addition takes very little energy to get back up to pressure as it already has nearly boiling hot water inside.

The smallest Instant Pot pressure cooker is large enough for 2 people and draws a max of 670 Watts but only long enough to build up pressure by boiling the water (usually 5-8 minutes if water starts near 20 deg C), then uses short energy draws if pressure is needed to be maintained. I can reduce the energy use of the Instant Pot even further by reducing the boil to pressure time, by using pre-heated water either from my wood stove or even water that was sitting in a black container in the sun when it's too warm to use the wood stove. The Instant Pot is really useful for me to use for cooking some foods ahead of meals when the sun is shining, and to then leave them in the Instant Pot to cook using barely any energy at all to maintain pressure. The downside, is that it might be awkward to secure in use on a moving boat but might be worth the effort due to the energy savaings.

We use a pressure cooker on our induction hob regularly. We really don't se3m to suffe4 from a lack of power but we do plan to add a couple of 100w flexible panels for when we are at anchor so we can boost the charging a little when it's cloudy. We still have a propane cooker and generator as back up so no real issues.
Our boat is 24v so our wires are a lot less cross-section than you need in a 12v system. Ditton the 200amp BMS handles twice the load due to the 24v system. Wire s8ze on negative and positive to the battery is 35mm2

 

[E. Cho]

The Instant Pot vs regular pressure cooker are like night vs day in energy use due to direct and insulated "in the pot" heating vs transfer heat from the induction plate and energy loss to ambient air temperature and especially due to it's safety, as well as convenience, due to the Instant Pot timer functions. No more forgetting to turn it off, no more boil overs, no more boil dry, etc..

As well, the Instant Pot was less expensive than my other 2 manual pressure cookers, 1 aluminum and 1 steel, both which I stopped using once I got the Instant Pot.

Safety was my #1 concern and energy efficiency was #1A. Maybe I've had too many senior memory lapses but I have had many scary close calls using other cooking methods and the really high energy efficiency was also required in my off grid remote cabin, especially during dark overcast short winter days when solar was minimal and it was too cold to start the diesel generator for battery charging.

I have a 24V system as well and am just starting to build my 305 AH 24V pack. I'll have to look at my newer JK BMS to see if I can or if the BMS wires need to be made bigger, though the BMS. There is a cover plate over top of the BMS connections so I'm not sure if the Mfg wires are soldered or screwed in to the BMS.

Safe Travels! Thanks for sharing too!

 

[TimE]

The Instant Pot vs regular pressure cooker are like night vs day in energy use due to direct and insulated "in the pot" heating vs transfer heat from the induction plate and energy loss to ambient air temperature and especially due to it's safety, as well as convenience, due to the Instant Pot timer functions. No more forgetting to turn it off, no more boil overs, no more boil dry, etc..

As well, the Instant Pot was less expensive than my other 2 manual pressure cookers, 1 aluminum and 1 steel, both which I stopped using once I got the Instant Pot.

Safety was my #1 concern and energy efficiency was #1A. Maybe I've had too many senior memory lapses but I have had many scary close calls using other cooking methods and the really high energy efficiency was also required in my off grid remote cabin, especially during dark overcast short winter days when solar was minimal and it was too cold to start the diesel generator for battery charging.

I have a 24V system as well and am just starting to build my 305 AH 24V pack. I'll have to look at my newer JK BMS to see if I can or if the BMS wires need to be made bigger, though the BMS. There is a cover plate over top of the BMS connections so I'm not sure if the Mfg wires are soldered or screwed in to the BMS.

Safe Travels! Thanks for sharing too!

I did some Googling and can find no suggestion that the Instant Pot is more energy efficient than a conventional pressure cooker. The benefit of our stainless steel pressure cooker is that it can work on the induction hob and the gas hob.

 

[featherlite]

Nice and tidy install ... I like! ?

 

[Marinepower]

You may want to keep some of your existing lead acid to power your windlass and start motor. These big inductive loads are not FET based BMS friendly.

 

[TimE]

You may want to keep some of your existing lead acid to power your windlass and start motor. These big inductive loads are not FET based BMS friendly.

We have a pair of 12v lead starter batteries, wired in series. We are a 24v boat. In addition, at the turn of a switch we can swap the whole load over to 4x Trojan T105RE batteries. The Windlass load runs through the BMS. We also run the 220v watermaker through the BMS. The load is about 90A at 24v. The BMS is rated at 200A.

 

[sunshine_eggo]

We have a pair of 12v lead starter batteries, wired in series. We are a 24v boat. In addition, at the turn of a switch we can swap the whole load over to 4x Trojan T105RE batteries. The Windlass load runs through the BMS. We also run the 220v watermaker through the BMS. The load is about 90A at 24v. The BMS is rated at 200A.

The concern is that electric motors have a surge about 5X the run current, and that commonly overwhelms a BMS.

 

[TimE]

The concern is that electric motors have a surge about 5X the run current, and that commonly overwhelms a BMS.

The inverter is a 3kw unit. It has a maximum surge rating of 9kw. The inverter was sized to be able to run my 1.5kw watermaker motor. Something it does without problem. The BMS is rated at 200amp. The maximum discharge current of the BMS (2min rating) is 350amp. 24v boat
Am I missing something?

 

[sunshine_eggo]

The inverter is a 3kw unit. It has a maximum surge rating of 9kw. The inverter was sized to be able to run my 1.5kw watermaker motor. Something it does without problem.

Not sure how the inverter is relevant to DC motors.

The BMS is rated at 200amp. The maximum discharge current of the BMS (2min rating) is 350amp. 24v boat
Am I missing something?

What is the surge current of your windlass?

 

[TimE]

Not sure how the inverter is relevant to DC motors.



What is the surge current of your windlass?

My watermaker is 220v 1.5kw motor runs through the inverter off the lithium.
No idea of the surge current of the windlass motor.

 

[TimE]

I haven't seen more than 50amps when running the windlass. 5 times that is less than the 350 limit so withing the rating of the BMS.
I might swap it over to run on the engine batteries since it is an easy job, just to be safe

 

[sunshine_eggo]

My watermaker is 220v 1.5kw motor runs through the inverter off the lithium.

The watermaker has 1.5kW motor?

No idea of the surge current of the windlass motor.

You might be fine, but the above means you haven't evaluated your loads against system capabilities.

I haven't seen more than 50amps when running the windlass. 5 times that is less than the 350 limit so withing the rating of the BMS.

5x is an approximation. They can be a little lower or even higher. If you have a clamp DC ammeter with a MAX function, it's worth checking.

Visually, your BMS is a FET based BMS (no external or integral relay), and I would be hesitant to trust the surge rating. Many believe that even trusting the max continuous current rating is potentially too aggressive, and they should be derated, i.e., if you need a 150A BMS, upgrade to the 200A to be safe.

I might swap it over to run on the engine batteries since it is an easy job, just to be safe

Lead-acid are highly tolerant of brief surges of large current. It's why lead-acid is still almost the exclusive choice in starter batteries.

You may be fine as-is. If a measurement confirms the surge is typical or preferrably even under 200A, you've done the work, and you can safely say it's within limits.

 

[TimE]

The watermaker has 1.5kW motor?



You might be fine, but the above means you haven't evaluated your loads against system capabilities.



5x is an approximation. They can be a little lower or even higher. If you have a clamp DC ammeter with a MAX function, it's worth checking.

Visually, your BMS is a FET based BMS (no external or integral relay), and I would be hesitant to trust the surge rating. Many believe that even trusting the max continuous current rating is potentially too aggressive, and they should be derated, i.e., if you need a 150A BMS, upgrade to the 200A to be safe.



Lead-acid are highly tolerant of brief surges of large current. It's why lead-acid is still almost the exclusive choice in starter batteries.

You may be fine as-is. If a measurement confirms the surge is typical or preferrably even under 200A, you've done the work, and you can safely say it's within limits.

I will swap the windlass over to the start batteries. It's easy to do.
I plan to build a second lithium bank in the next 12 months. I will use the same JK 200a BMS. Halving the load will be useful and provide some redundancy. Thanks for your input, much appreciated