Lithium to power thruster

[jordanbigel]

I am also interested in this question - my bow battery is nearing end of life and I would consider replacing my AGM battery with Lithium if it was cost effective, or even cost-adjacent.

My current 4D AGM provides 210ah and 1100 amps CCA, so it has no problem supplying power to my 12v 5hp thruster (or the 12v windlass).

I would love to know which BMS can deliver 500+ amps and how big a LifePo battery I would really need to feed this thing. My sense is the cost would be easily 150% of the cost to just replace the 4D (about US$750).

[CharlieJ]

I would love to know which BMS can deliver 500+ amps and how big a LifePo battery I would really need to feed this thing. My sense is the cost would be easily 150% of the cost to just replace the 4D (about US$750).

None that I know of. You can work around that with relays but...the fundamental problem is that the BMS may see a big surge as a short circuit and shut down.

[Networker]

I have 1200 AH of cheap (but good quality) drop-in Ampere Time batteries and they work fine when I run the bow thruster and electric windlass at same time. Voltage drops a lot momentarily, but other than that, seems to work with no issues.

[Whatta Life]

Originally Posted by jordanbigel

I am also interested in this question - my bow battery is nearing end of life and I would consider replacing my AGM battery with Lithium if it was cost effective, or even cost-adjacent.

My current 4D AGM provides 210ah and 1100 amps CCA, so it has no problem supplying power to my 12v 5hp thruster (or the 12v windlass).

I would love to know which BMS can deliver 500+ amps and how big a LifePo battery I would really need to feed this thing. My sense is the cost would be easily 150% of the cost to just replace the 4D (about US$750).

i had same issue, here is how I got around it. I built my own lfp battery with bms. 500a bms is available but expensive. Used a smaller bms for charging and balancing but hooked the bow thruster directly to battery. I don't use the bow thruster for more than 30 seconds at a time so there is no way I'm going to drain the battery too low. Nothing else is attached to drain the battery so don't have to worry about it. Bms handles charging protection and balancing( you can use a small bms)

[Wotname]

Originally Posted by Camille1

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.

If your principal concern is leaving your battery unattended for winter, simply use a good quality AGM starting / deep cycle battery for the bow thruster. They have a very low self discharge and provided they are fully charged, they can sit for 6 months without problems - especially in winter time temperatures. Some will last up to two years with minimal self discharge e.g. Odyssey

[kirklkjb]

Can you figure out what the actual peak and sustained current is. That will go very long way in defining what you need.
Most every BMS will shutoff if it detects a short or what looks like a short.

The direct connection could be boat burning dangerous without some sort of short circuit protection like a resettable fuse.

[d design]

better off with supercapacitors

[OceanStateTunin]

Originally Posted by Whatta Life

i had same issue, here is how I got around it. I built my own lfp battery with bms. 500a bms is available but expensive. Used a smaller bms for charging and balancing but hooked the bow thruster directly to battery. I don't use the bow thruster for more than 30 seconds at a time so there is no way I'm going to drain the battery too low. Nothing else is attached to drain the battery so don't have to worry about it. Bms handles charging protection and balancing( you can use a small bms)

How is this working out? I was thinking of running 4 eve cells next to my bow thruster directly to the battery (obviously with a fuse/breaker) and the rest of the cells to s very small say 50amp bms with a 6wg wire going to my existing lifepo4 bank so everything charges off my victron multiplus and solar and also gives my house bank extra capacity. Would this work? Thoughts?

[JustMurph]

Why not just run some decent size wiring from the house bank? Lighter, cheaper, easier.

[OceanStateTunin]

Originally Posted by JustMurph

Why not just run some decent size wiring from the house bank? Lighter, cheaper, easier.

150mm2 over about 25'x2 would not be cheap.

[Baronkrak]

Originally Posted by Networker

..... Voltage drops a lot momentarily,...

This is essentially what causes a BMS to disconnect.

[JustMurph]

Originally Posted by OceanStateTunin

150mm2 over about 25'x2 would not be cheap.

Surely cheaper than a whole new LFP bank and everything that goes with charging and protecting it. And much much simpler.

How much current does the bow thruster draw?

[OceanStateTunin]

Not with the price I'm seeing tinned copper at? Do you have a better source? Even if I undersized it with only 4/0, tinned copper would still be more then a battery up front and well it would be undersized wire.

Also as I was saying, keep a small wire to parallel between my existing lifepo4 house bank by using a small bms on the thruster battery so it will charge off my multiplus and solar. Also will add some extra capacity to my house bank should the thruster bank not be depleted. 4 eve 280ah cells, building a case and a small bms will be under $600.

[JustMurph]

AU$14/m for tinned double insulated copper 50mm^2 last time I bought it from my local in Australia. Six runs over that over 7.5m is AU$640, so a bit over US$400.

Even if it was the same cost, I'd still go for the simpler setup, personally. But I can see why the extra 280AH changes the value proposition. Fair enough.

[s/v Jedi]

Good info is in the thread but drowned in silly comments. So to put the two best options back in the spotlight:

- Odyssey TPPL AGM

- DIY 6s LTO cells

and for bonus a third option that uses LiFeYPO4 and actually works with 100A continuous and 1,000A peak capacity: https://en.winston-battery.com/stati...5160831837.pdf

These options charged using a programmable dc-dc charger.