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Old 15-04-2021, 00:40   #1
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Lithium to power thruster

Should I use a bank of lithium cells to power my bow thruster. Might there be overheating or problems with the battery management system?
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Old 15-04-2021, 01:05   #2
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Re: Lithium to power thruster

That would depend on the capacity of your LiFe bank and the current draw of your bow thruster.

I personally try to limit the current draw on my LiFe bank to 50% of capacity (so 200amps from my 400Ah bank), for this reason I keep a lead acid start bank that also runs my windlass. No bow thruster but if I did have it would also be off the lead acid bank.

Having a lead acid bank also makes charging via alternator safe and easy (alt - lead acid - dc/dc - LiFe)
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Old 15-04-2021, 06:11   #3
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Re: Lithium to power thruster

My own lithium bank is rated at 1C, I choose to limit it to 0.5C for longevity.



I also charge to max 90% (13.6V) when on the boat and max 70% (13.2V) when not on the boat - discharge is electronically limited to 20% SOC even though they can be fully discharged without immediate (noticeable) damage.


All the above is done in the name of longevity because they cost a lot of cash and I want to look after them as best I can.


So can you run your bow thruster off your LiFePO4 bank? In my opinion yes if the operating current of all concurrent loads remains below 0.5C, otherwise I would advise against it.


If you have a lead acid bank for starting then use that for your bow thruster. If you only have LiFe and it is rated to start your engine then by all means use it to run the bow thruster as well (but not at the same time!)


From Solarcity INC -
How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries

"How fast those lithium ions get yanked hither and yon has an effect on cycle life as well. In light of the above that should be no surprise. While LFP batteries will routinely do charging and discharging at 1C (i.e. 100 Amp for a 100Ah battery), you will see more cycles out of your battery if you limit this to more reasonable values."




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Old 15-04-2021, 09:39   #4
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Re: Lithium to power thruster

Another thing to check is the voltage of the bow thruster. A LiFePO4 battery will maintain a much higher voltage and higher current than a lead acid battery will. This will produce more power to the thruster which can result in higher temperatures of the thruster motor.

Another thing to consider would be to use a remote battery bank closer to the load for the windlass and the bow thruster. Nigel Calder does this so he doesn't have to run large cables to the front of his boat. Might do some research on what Nigel is doing as he is very familiar with LI battery usages and backs it up with experience.
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Old 15-04-2021, 10:35   #5
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Re: Lithium to power thruster

Actually P=VI=I2R, so higher voltage will result in lower amps and less heat.

This is one of the main reasons why voltage drop is a big problem for motors, low volts + high amps to produce required power = high heat = burnt motor.
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Old 15-04-2021, 11:43   #6
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Re: Lithium to power thruster

from a technology standpoint, a lifepo4 bank that powers the thrusters is almost an ideal set up. High amperage output, high amp restore. Bow thrusters arent meant to be run much, but when they do, its pretty high amperage - which is why a lot of thrusters have battery banks near them for minimizing heavy cable runs with the high amperage they need.
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Old 15-04-2021, 12:05   #7
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Re: Lithium to power thruster

LiFePO4 is great for this application. Lithium Titanate perhaps even better.

I've done some testing with Headway HP cells. One reason if you are assembling your own to use something like the HP cells is that the internal construction is such that they are optimized for heavy current pulses (less than oh say 20 seconds per pulse).

I do not have a thruster but do have a windlass. I did measure the total AH draw for pulling in my entire 230' chain and 85# anchor in 25' of water. The draw was minimal, Something like 6 AH if I remember correctly. This was pulled from a 32 AH Headway battery I assembled.

With a remote battery powering your thruster and a dc to dc charger for the remote battery you could use a 24 volt or 48 volt thruster. The dc to dc charger takes care of any voltage change ( e.g. 12 house to 24 v thruster). This would reduce the current needed for any given HP thruster.

This link is to some options that we discussed here on CF.
https://www.cruisersforum.com/forums...ts-234714.html
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Old 15-04-2021, 12:28   #8
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Re: Lithium to power thruster

Quote:
Originally Posted by anthem00 View Post
from a technology standpoint, a lifepo4 bank that powers the thrusters is almost an ideal set up. High amperage output, high amp restore. Bow thrusters arent meant to be run much, but when they do, its pretty high amperage - which is why a lot of thrusters have battery banks near them for minimizing heavy cable runs with the high amperage they need.

As much as I dislike lead acid batteries, for engine starter motors and thrusters they are pretty much the perfect application. They deliver excellent short time high current capacity, easy integration into the boat electrical system and are also quite cost efficient. When going lithium look at the battery management system AMP rating which is generally the limiting factor. If technologically inclined you may want to look into a 48V thruster motor as used on electric boats which sits well with lithium but this is another can of worms.
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Old 15-04-2021, 13:59   #9
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Re: Lithium to power thruster

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Originally Posted by tomsnrg View Post
As much as I dislike lead acid batteries, for engine starter motors and thrusters they are pretty much the perfect application. They deliver excellent short time high current capacity, easy integration into the boat electrical system and are also quite cost efficient. When going lithium look at the battery management system AMP rating which is generally the limiting factor. If technologically inclined you may want to look into a 48V thruster motor as used on electric boats which sits well with lithium but this is another can of worms.
Like Tom says ^^^^^

Li batteries for a bowthruster are a flagrant waste of money--for no benefit in the real world.

Of course it is YOUR money... so feel free.
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Old 15-04-2021, 14:00   #10
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Re: Lithium to power thruster

Bow thrusters are around 500a.

So for the drop in ones you’d need 5-10 of them... as they Likly max out at 100a each.

External bms bank would handle it better if done right.
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Old 15-04-2021, 16:12   #11
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Re: Lithium to power thruster

Quote:
Originally Posted by parachute View Post
Lithiumm batteries have caughfire in planes and and cars and everything else with a Lithium battery including phones.

Lithium-ion batteries commonly used in consumer electronics are notorious for bursting into flame when damaged or improperly packaged. ... "If the battery is damaged and the plastic layer fails, the electrodes can come into contact and cause the battery's liquid electrolyte to catch fire

List of UK Lithium battery fires: https://resource.co/article/lithium-...llion-annually
But seriously, only silly people would use other than LiFePO4 batteries on a boat and re-hashing old tales about lithium ion fires is also not useful.
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Old 16-04-2021, 12:16   #12
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Re: Lithium to power thruster

Thanks, Guys for some really useful info.

I know lead acid has its plus points but I voyage around leaving my boat wherever I stop for the winter. Yards in the Med I have found will not allow you to leave your battery charger running on tick-over (Fire insurance risk for the yard) so this year, in particular, with no 2020 sailing my lead acids are all likely caput. I know,--- solar or wind generators. In the winter, I think wind may be best. I am fitting one now as I am moving back to Northern Europe.
Thanks again.
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