Thoughts on Using LTO Battery for Cranking.

[SOLAR SUPPORT]

12-24 volt large DC motors that draw high current from the batteries. They work with the starter motor that starts the engine, windlass, bow thruster, electric winches. The dc motor current required to simultaneously start moving the internal combustion engine elements is quite high. It is the starter motor first movement that needs the biggest current. If the engine is bigger then the DC starter motor power should be higher too. The amount of energy used during this short-term operation for 30 hp diesel engine is approximately 1/25~1/250 of the energy consumed by a small refrigerator throughout the day.

Max. Power and Energy calculation:
(It is assumed that there are no losses in power transmission cables and no Phuckert effect in batteries)

Five seconds operation of the 1100Watt starter motor that starts a 30 Hp diesel engine:
Max. Power: 12V x 350A(max) = 4200W (max)
Energy: 12V x 200A(avg) x (5/3600)h = 3.3Wh (0.27Ah)

Windlass, ewinch, bow thruster etc. that operate for 2 minutes with a 1000 Watt DC motor:
Max Power: 12V x 120A(max) = 1400W (max)
Energy: 12V x 80A(avg) x (120/3600)h = 33Wh (2.7Ah)

The medium-sized refrigerator is 60% on and 40% at rest throughout the day.
Max power: 12V x 30A(max) = 360W
Energy: 12V x 4A(avg) x (24h x 60%) = 691Wh (57Ah)

According to these calculations, there is a need for batteries with the capacity to meet the instantaneous high power required by large electric motors operating with 12V and to store the relatively low energy that these consumers need throughout the day. LTO or AGM batteries with high CCA capacity can be used.

If you have a large LFP service battery bank and the sum of the continuous max discharge and short-term peak discharge current values ​​of these batteries' BMS is sufficient, it is possible to do all the heavy electrical work on the boat with the LFP battery bank. It is undoubtedly safer to have an isolated, independent battery to start the engine.

LTO manufacturers promise that the cells can be discharged with a 10C continuous current and a 20C short-term current. Average start-stop AGM battery manufacturers promise short-term 10C. It is possible to calculate the battery capacity required for the starter motor in line with these values ​​promised by the manufacturers. For the example above, based on the maximum instantaneous peak current discharge capacity values ​​of LTO and AGM batteries, a 30Ah capacity LTO or 60Ah AGM battery will be sufficient for starter motor operation. LTO batteries, which are long-lasting, safe, resistant to extreme hot and cold environments, and stand out with high peak current values, may be preferred. With a high performance 6s LTO battery, you can run two diesel engines, windlass and bow thruster engines, but not at the same time.

6s LTO battery with active balancer (6x2.4V=14.4V) can be charged with a 12V alternator without the need for BMS. The charge level of the LTO battery can be monitored with a simple volt meter.

When we go back to the calculation example above and look at the calculated energy consumption amount (Total: 3Ah), after starting the engine with the LTO battery and anchoring, the alternator set to a capacity limited to 60A will put approximately 3 Ah of the energy used from the LTO battery back into the LTO battery in three minutes. 12V x 60A x (3min/60)h = 36Wh(3Ah)

It does not make sense to use LTO batteries as service batteries , which have lower energy density than LFP batteries, due to their high energy capacity cost. Therefore, it is much more logical to use LFP batteries, which have very affordable costs per Ah, to operate electrical devices other than the high-power electrical energy consumers mentioned above. LFP batteries, whose discharge voltage graph is almost flat, are preferred due to their safety, high energy density and high performance.

Your Thoughts on Using LTO Battery for Cranking.

[rocks]

I have 2 x 315 hp motors each starting from their own set of 6 x 40ah LTO for the last 4 years. Each set has an active balancer we do not have a BMS.
The only draw back is 40ah will not run the Glow Plugs, as we are in the tropics we have disconnected the Glow Plugs. The motors start with in 2 seconds. To charge we use 10 watt solar panels, and the motor’s alternators.