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Lifepo with 10 hp Yamaha high thrust outboard engine

Thanks Hugo glad to hear it is all working well for you! So being in parallel you treat it as one bank on a Lifepo4 charge profile? The Lifepo4 just holds the AGM voltage at 13v+? So if the BMS shuts the Lifepo4 off does that mean the AGM will be there to take over?

Cheers!
yes, two lifepos in parallel as one bank, the lifepos hold the voltage and in case they switch off the small AGMs take over. Simpler to fit than a surge protector which needs to be very close to the alternator coil.
 
Why that's a Tiki 38! I'm in the process of finishing mine, where are you based?

As for the charging, you can't really charge Li batteries from the outboard without some kind of external charge regulator. You run the risk of damaging the batteries and/or the alternator. The 10A output is at max RPM and you're not likely to see more than 5 or 6A at normal running speeds, though you can run them both at the same time of course. That will probably replace the starting drain but is not really practical for general charging.

The other, more critical thing is that the charge profile is not safe for the batteries. You can find some details here: https://marinehowto.com/lifepo4-batteries-on-boats/

and a lot more information on safe design parameters here: http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

It's not safe (for the Li batteries) to simply plug them in to replace lead acid. The charging system will need to be set up for the new batteries. Given the surface area you have available and the low cost of panels, more solar is likely the most efficient and effective solution, particularly if your current solar controllers have some excess capacity available.
Well said, i see a lot of lithium 'peddlers' touting 'drop-in replacement' and for automotive thats not the case. as for me, after changing our old 2-stroke 115 for a 100 4-stroke, to get some weight out of the stern i have ditched the 21 kg cranking battery and 25kg 100 ah deep cycle for a 3kg supercapacitor for starting and a 12 kg 130 ah lifepo4 for the electronics. The lifepo4 i can run separate to the motor but i have a 20a dcdc converter for it for the longer hotter days (we like out fridge cold), and to protect the capacitor and alternatir from each other a pair of 'parallel-capable 300 amp welder diodes in the circuit for starting with a 4 ohm power resistor in parallel to allow recharging the supercap, even with a small 8ah lifepo4 battery in there to hold its charge when in storage. All this has yet to be completed and while the outboard specs say it will shut down if the alternator reaches 16 volts or above from what i'm reading i might also put a diode in series with the 'charging' resistor to further protect the supercap which has a maximum voltage of 16 volts. It all sounds pretty rough i know but i'm trying to keep it simple ?
 
I think there's some dangers involved. Probably more to the outboard. If the batteries were full the batteries could possibly over charge or turn off damaging the charging system. I don't want to experiment with expensive equipment. Perhaps the solar panels will supply enough power for your house bank and a small starter battery or two. Ask in another area of this forum and you will probably get better advise. Good luck
I agree with Bubba1 if the Batteries are low the charging circuit might try to put out too much current should blow a fuse. If the Lithium batteries are full the internal BMS might just disconnect damaging the outboard. I have a Yamaha 9.9 for a dingy thinking about this same thing. I'm probably going to use a small seal lead acid like 35 ah about 21 lbs for the starter only. Then use a Lithium 12 volt 100ah battery about the same weight with a 100 watt panel on the small Radar arch for my lights, fish/depth finder etc. These outboard the 9.9 hp only put out about 6 to 12 amps anyway, leave them on the Lead Acid and save the charging system.
 
Why that's a Tiki 38! I'm in the process of finishing mine, where are you based?

As for the charging, you can't really charge Li batteries from the outboard without some kind of external charge regulator. You run the risk of damaging the batteries and/or the alternator. The 10A output is at max RPM and you're not likely to see more than 5 or 6A at normal running speeds, though you can run them both at the same time of course. That will probably replace the starting drain but is not really practical for general charging.

The other, more critical thing is that the charge profile is not safe for the batteries. You can find some details here: https://marinehowto.com/lifepo4-batteries-on-boats/

and a lot more information on safe design parameters here: http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

It's not safe (for the Li batteries) to simply plug them in to replace lead acid. The charging system will need to be set up for the new batteries. Given the surface area you have available and the low cost of panels, more solar is likely the most efficient and effective solution, particularly if your current solar controllers have some excess capacity available.
They have come a long way in two years!
 
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