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mikereed100 · 14-01-2023, 09:50

I am planning on replacing my recently assassinated AGMs with a 400 ah LFP bank using 2 x 200a KiloVault HLX+ drop ins. "Current" (I am not proud of myself) wisdom says that drop in LFPs should not be used for large loads like a windlass as the in-rush current will exceed what the BMS can handle. OTOH, battery specs show that each 200a battery can handle 500a peak discharge current for < 3 seconds. With 2 batteries in parallel this would be closer to 1000a, no? My windlass is 1000w, roughly 85a at 12v. Even given an in-rush current 5x normal operating current this would be roughly 425a. Close to the capacity of a single battery but well within parameters for 2 batteries in parallel.

Just wondering how others with LFP banks handle windlass loads. My start batteries are sealed FLA that sit over 40' from the windlass, so they are not much help and I would rather not install a dedicated battery for the windlass as that makes charging complex, although that could be option.

senormechanico · 14-01-2023, 09:58

If you can, why not just wire the windlass circuitry directly to the battery bank, bypassing the BMS? The battery should have no problem running the windlass.
If the BMS is built into the battery, oh well...

rslifkin · 14-01-2023, 10:07

Quote:

Originally Posted by senormechanico

If you can, why not just wire the windlass circuitry directly to the battery bank, bypassing the BMS? The battery should have no problem running the windlass.
If the BMS is built into the battery, oh well...

Nothing on an LFP bank should ever bypass the BMS. You risk destroying the bank if there's a load the BMS can't cut off.

wholybee · 14-01-2023, 11:24

I know of several sailors using a 1000w windlass with a 100A Daly BMS without problems. They are definitely pushing it and at risk of a problem, but it works fine. Given that Kilovault is a higher quality drop-in, and that it is rated for (both in parallel) 1000A surge, you should be fine as well.

The BMS (and kilovault uses a better one) should protect itself and stop current before any damage takes place. The BMS should survive a direct short of thousands of Amps. It will shut down, but survive. You should also have a breaker in the system, which should trip after exceeding its rating for a few seconds?(150A ish?)

The danger is if the motor stalls, not inrush from starting. When a windless starts, the chain is usually slack. You should be able to pull that in by hand, and little current is needed. When it stalls, current will go through the roof. If the motor starts to load up and your anchor doesn't come free, stop the windless and deal with the stuck anchor, don't just keep hitting the up button.

mikereed100 · 14-01-2023, 11:56

Quote:

Originally Posted by wholybee

I know of several sailors using a 1000w windlass with a 100A Daly BMS without problems. They are definitely pushing it and at risk of a problem, but it works fine. Given that Kilovault is a higher quality drop-in, and that it is rated for (both in parallel) 1000A surge, you should be fine as well.

The BMS (and kilovault uses a better one) should protect itself and stop current before any damage takes place. The BMS should survive a direct short of thousands of Amps. It will shut down, but survive. You should also have a breaker in the system, which should trip after exceeding its rating for a few seconds?(150A ish?)

The danger is if the motor stalls, not inrush from starting. When a windless starts, the chain is usually slack. You should be able to pull that in by hand, and little current is needed. When it stalls, current will go through the roof. If the motor starts to load up and your anchor doesn't come free, stop the windless and deal with the stuck anchor, don't just keep hitting the up button.

Good point. We usually bring the chain up tight and either let wave action break the anchor loose or bounce on the chain between the windlass and the roller.

sailorboy1 · 14-01-2023, 12:17

Even though the windlass is pretty high amps, mine has a 50a breaker. I would like to believe my 4 drop in LFPs that have an allowed 100a/ea discharge spec would be fine. But I can not now run my windlass off the house bank so for me it doesn't matter anymore.

donradcliffe · 14-01-2023, 12:30

Quote:

Originally Posted by wholybee

I know of several sailors using a 1000w windlass with a 100A Daly BMS without problems. They are definitely pushing it and at risk of a problem, but it works fine. Given that Kilovault is a higher quality drop-in, and that it is rated for (both in parallel) 1000A surge, you should be fine as well.

The BMS (and kilovault uses a better one) should protect itself and stop current before any damage takes place. The BMS should survive a direct short of thousands of Amps. It will shut down, but survive. You should also have a breaker in the system, which should trip after exceeding its rating for a few seconds?(150A ish?)

The danger is if the motor stalls, not inrush from starting. When a windless starts, the chain is usually slack. You should be able to pull that in by hand, and little current is needed. When it stalls, current will go through the roof. If the motor starts to load up and your anchor doesn't come free, stop the windless and deal with the stuck anchor, don't just keep hitting the up button.

You just said that the windlass should have a 150 amp breaker. I you keep hitting the up button, the breaker will open and limit the current from going through the roof. That's its job, and it should trip before even one Kilovault 2400 BMS.

Captain Bill · 14-01-2023, 12:43

I run 3 100ah drop-ins for my house bank using only the built in BMSs and run a Maxwell 1200. The built in BMSs are rated at 100a continuous and 285a for 3 seconds peak. So I can sustain 300amps from my house bank. Since I have the whole bank fused for 300a I'm pretty sure that the fuse won't last 3 seconds if I try to pull more than that. The windlass draws 85a continuous and runs through its own 135amp breaker. I returned from a 8 month cruise, anchoring out most nights. I never once had a problem pulling up the anchor with this setup. I should note that I never never ever try to un-stick the anchor with the windlass. I have a heavy duty chain stopper and when the chain gets vertical we lock it with the chain stopper and power it out with the engines. That being said, when we were in the Hospital anchorage in Norfolk Va, I snagged a 2.5 inch diameter abandoned towing cable on the bottom and had to lift it using the windlass. This was an extremely heavy lad and while the windlass complained a lot it did lift it to the surface where I could get a rope around it to unhook it from the anchor. Since it never tripped the breaker I guess I never pulled more than 135a sustained for any period of time. The batteries had no problem handling this. I wouldn't think your set up would have any problem.

rslifkin · 14-01-2023, 17:24

When it comes to windlass loading, as a safety I always keep the clutch set so it'll slip before the windlass stalls and pops the breaker. That way I get an indication on deck of pushing it too hard and can stop before I need to make a trip below to reset the breaker.

**noelex 77** · 14-01-2023, 18:30

The specifications for anchor windlass motor draw currents is very nominal.

My own windlass is rated at 2kw but under maximum load according to Maxwell it will draw over 450A @24v (over 10kw). This is not the start up current, but rather the steady state draw at (or just below) the maximum load.

That is not to say your proposed battery system will not drive the windlass, but a theoretical calculation using the nominal wattage of the windlass is not much help in resolving the issue. Using the value of the windlass circuit breaker is probably a better starting point, but you need to know the tip curve and compare this to the BMS specifications.

Also consider that two batteries in parallel will not share the load exactly evenly so you cannot simply double the maximum draw available from a single bms.

rslifkin · 14-01-2023, 18:37

Quote:

Originally Posted by noelex 77

The specifications for anchor windlass motor draw currents is very nominal.

My own windlass is rated at 2kw but under maximum load according to Maxwell it will draw over 450A @24v (over 10kw). This is not the start up current, but rather the steady state draw at (or just below) the maximum load.

That is not to say your proposed battery system will not drive the windlass, but a theoretical calculation using the nominal wattage of the windlass is not much help in resolving the issue.

Good point. I'd probably want to be able to support at least triple the breaker rating (as that'll trip most breakers within a couple of seconds).

mikereed100 · 15-01-2023, 09:54

Quote:

Originally Posted by noelex 77

The specifications for anchor windlass motor draw currents is very nominal.

My own windlass is rated at 2kw but under maximum load according to Maxwell it will draw over 450A @24v (over 10kw). This is not the start up current, but rather the steady state draw at (or just below) the maximum load.

That is not to say your proposed battery system will not drive the windlass, but a theoretical calculation using the nominal wattage of the windlass is not much help in resolving the issue. Using the value of the windlass circuit breaker is probably a better starting point, but you need to know the tip curve and compare this to the BMS specifications.

Also consider that two batteries in parallel will not share the load exactly evenly so you cannot simply double the maximum draw available from a single bms.

Good points. The trip curve for my breaker matches pretty much exactly the 3 second capacity of a single KiloVault 2400. Adding the second battery should give me a comfortable margin, even if the load is not shared precisely evenly. We always have both engines running when using the windlass, which allows the alternators to share a small bit of the load.

In the 13 years we have had an electrical system onboard (we cruised for a couple of years without electricity) the windlass breaker has never tripped despite hauling up some monstrous clumps of debris. Like rslifkin we also loosen the clutch a bit to prevent hard jerks.

I suspect that my system should do alright as long as I don't abuse it. If not, we have plenty of room for another 200ah battery.

ThereAndBack · 15-01-2023, 10:15

Has anyone actually experienced a problem? I have 4 x 100ah 12v drop-ins and a 1000w windlass and have never had an issue and I've punished my windlass, brutally.

senormechanico · 15-01-2023, 16:27

Quote:

Originally Posted by rslifkin

Nothing on an LFP bank should ever bypass the BMS. You risk destroying the bank if there's a load the BMS can't cut off.

Imho, the risk of damaging a 100 amp BMS is a lot greater than the risk of the properly wired and circuit breaker/fused windlass destroying the battery bank.

If you leave the boat, turn off the windlass breaker if you think it's going to go nuclear on you.

Edit: I wrote that before reading any replies.
Bottom line for me, fuggidaboudit. There are more important things to fret about.