Lifepo with 10 hp Yamaha high thrust outboard engine

[Hugo]

I plant to use the lifepo house battery (2 x 12 V 280 Ah in parallel,( https://diysolarforum.com/threads/waterproof-case-for-4-280ah-eve-or-lishen-cells.17740/ ) ) in combination with a 10 hp Yamaha high thrust outboard, for charging the battery and for starting the outboard. Is there any experience how the outboard engines work with a lifepo battery?

The charging circuit is using simple coils, a rectifier and a regulator (see attached picture), the coils can generate max. 10A. I may reduce the max voltage by using two high power diodes in rectifier configuration to cause a voltage drop of 1 V to the battery in order to be at a safe voltage below 14 V for charging.

 

[Bubba1]

What kind of boat? Sailboat? Why so much battery?

 

[JeepDaddy]

Keep in mind that your outboard's 10 amp max rating is probably at close to full throttle. Small electric start outboard motors typically are designed to charge only what the starter consumes, maybe a bit more. I'm not sure what other solar/generator setup you have, but charging that much battery from only an outboard will be a challenge I would think.

 

[Hugo]

What kind of boat? Sailboat? Why so much battery?

it is a 38 foot sailing catamaran with two outboards

Keep in mind that your outboard's 10 amp max rating is probably at close to full throttle. Small electric start outboard motors typically are designed to charge only what the starter consumes, maybe a bit more. I'm not sure what other solar/generator setup you have, but charging that much battery from only an outboard will be a challenge I would think.

the outboards might help charging, there is otherwise 400W peak solar on the boat. The question is whether thereis a riskk either to batteries or outboard charging sytems in the setup since there is no additional srter battery.

I am replacing two 200Ah AGMs.

 

[Bubba1]

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

 

[Picasso]

Might be best to use a charge controller before the power gets from the outboards to the batt..

 

[Aaron_85]

i would get a DC DC charger. 560ah will toast a 10A alternator if let loose on it.

 

[Hugo]

Can you recommend one?

 

[JeepDaddy]

i would get a DC DC charger. 560ah will toast a 10A alternator if let loose on it.

I don't disagree with that, but I'm not sure how that would work with the starter motor. Maybe just adding a small LA starting battery with a DC-DC charger to the LiFePo4 bank would be best.

 

[willo]

Stick a small starter battery in there, then add a dc-dc charger between the starter and lifepo4 pack. Victrons can sense when the engine is running. The small battery will act as a buffer.

 

[willo]

I use a victron smart unit so I can control it via Bluetooth. It also supports control from my BMS via a remote trigger input.

 

[Micky]

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.

 

[willo]

I’m going to second the above - do the math in watts and you’ll find that a minor charge isn’t really that much.
A wind generator will serve you better than trying to pull 5a (@12v) is only 60 watts and only when running. Yeah it can help, but really it’s not much. I tow my camper all day and the charge offset from my truck just helps offset the fridge load. (I get 250w from my tow connector and the fridge eats 400)

We’re I you, I’d take a serious look at expanding or rebuilding that solar array. 300 and 350w cells are now easily accessible.
Fit 3-4 of those and you’ll be in great shape. Add a 200-400 watt wind generator and you’ll be cherry IMO.

That hard bimini has quite a bit of space.
I’d also evaluate the rigging of that dhingy, quite a bit of space there...
Solar panels are getting cheaper and cheaper. You can get some great deals on slightly used panels too.

 

[Hugo]

Id di some more checking and experimenting on it. The output of the outboards is perfectly suitable for charging the Lifepos (it is a simple charging coil anyway) and it will charge with 10 A per outboard. The solar is setup that the lifepos are normally only charged to 50% that there is plenty of headroom in case that the outboards run for a long time. Even then it would be unlikely that they damage the lifepos because they cannot reach the maximum voltage. However I do not want to rely on it, the BMS in the batteries is set to switch off at 13,8 V, which leaves the remaining risk of a surge in the system damaging the diodes in regulator of the charge coils. Initially I wanted to fit a surge protector close to the coil of the outboard, but this was to complicated to fit. So I opted now to put one each 20Ah AGM in parallel to the lifepos and this is working fine, they are always kept at the same voltage as the lifepos, they are light enough and they can start the outboards in case the lifepos are switched off.
In case the BMS switches off then the charge of the outboards is getting dumped into the smaller AGMs.
The advantage of this setup is that no additional regulation, relays etc are required.
The main source for energy on my setup is solar not the engines, however they, the batteries and the circuits need to be protected in case they keep running for a long time.

PS I have read all the above references https://marinehowto.com/lifepo4-batteries-on-boats/ and http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/, an additional good source is Emily and Clarkes adventures on Youtube.

 

[Hugo]

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.

I am based close to Berlin, where do you build?

 

[Micky]

I'm in the desert of the SW USA. Getting to with a couple of months of launching after many setbacks unrelated to the boat.
I have built in 900w of solar from 5 panels with a small LiFePo starting battery and a larger house bank. I don't plan on using the outboards for anything other than replacing their own starting drain though they can be used in an emergency if the main system fails.
Your additional batteries to limit surge is a great idea, giving you backup for starting too. I went with a different motor choice but from what I remember the Yamahas put out 6A each? And I will look for the adventures of Emily & Clarke, thanks.

 

[Hugo]

I'm in the desert of the SW USA. Getting to with a couple of months of launching after many setbacks unrelated to the boat.
I have built in 900w of solar from 5 panels with a small LiFePo starting battery and a larger house bank. I don't plan on using the outboards for anything other than replacing their own starting drain though they can be used in an emergency if the main system fails.
Your additional batteries to limit surge is a great idea, giving you backup for starting too. I went with a different motor choice but from what I remember the Yamahas put out 6A each? And I will look for the adventures of Emily & Clarke, thanks.

10 A with the HT Yamahas

 

[Popao]

Id di some more checking and experimenting on it. The output of the outboards is perfectly suitable for charging the Lifepos (it is a simple charging coil anyway) and it will charge with 10 A per outboard. The solar is setup that the lifepos are normally only charged to 50% that there is plenty of headroom in case that the outboards run for a long time. Even then it would be unlikely that they damage the lifepos because they cannot reach the maximum voltage. However I do not want to rely on it, the BMS in the batteries is set to switch off at 13,8 V, which leaves the remaining risk of a surge in the system damaging the diodes in regulator of the charge coils. Initially I wanted to fit a surge protector close to the coil of the outboard, but this was to complicated to fit. So I opted now to put one each 20Ah AGM in parallel to the lifepos and this is working fine, they are always kept at the same voltage as the lifepos, they are light enough and they can start the outboards in case the lifepos are switched off.
In case the BMS switches off then the charge of the outboards is getting dumped into the smaller AGMs.
The advantage of this setup is that no additional regulation, relays etc are required.
The main source for energy on my setup is solar not the engines, however they, the batteries and the circuits need to be protected in case they keep running for a long time.

PS I have read all the above references https://marinehowto.com/lifepo4-batteries-on-boats/ and http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/, an additional good source is Emily and Clarkes adventures on Youtube.

Hi Hugo,

We have the same Yamaha 9.9HT engines on our 37' Easy Catamaran. Had a lot of issues with high voltages 15v+ when both motors are running. Not so bad when the batteries were low and could soak it all up but if they were floating and we had to motor a lot it would send the voltage sky rocketing. Just looking to replace our FLA with Lifepo4 and was wondering how your setup was going?

Cheers,
Michael.

 

[Hugo]

Hi Michael,
I have my lifepos known in operation this season with the 2x 20Ah AGMs in parallel and this is working extremely well (no extra starting batteries). Motoring for two days in a row and the batteries never switched off. I also never got them above 13.6 V as well. Since I set the photovoltaic that they stops charging above 13,5 V and the outboard engines only do the supplying work and they seem mostly occupied with keeping the navigation, lighting, pc, iPads and fridge fed.
With the 2x 200 Ah AGMs I used before, everything was set to higher voltage and I also noticed voltages over 14 V.
Setting the lifepos as I have it now I may not be able to use the full capacity (currently limited to about 400 Ah), I could still charge them higher if I see darker days without sun coming up. This summer I never went below 50% SOC.

 

[Popao]

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!