Lithium Powered Windlass

[swisel]

A friend replaced his manual windlass by installing his new powered windlass. Running the cables was the hardest (and quite expensive) part of the job according to him. It was a while later that I had an idea that I have no use for so I thought I'd post it here to see if it floats...
Instead of going to all that effort why not use a lithium battery pack; the kind used for boosting your car. These things don't way much more than your morning paper so sneakering it back to a convenient place to recharge shouldn't be a problem. For about a hundred bucks you could size one that should be good for two or three anchor retrievals I should think.
I did run this by my friend but he got a little gruff and not very helpful. Curious as to what will follow.

[smac999]

Maybe 10 secs?

[a64pilot]

No reason why it shouldn’t work if the battery is large enough.
Where and how are you going to charge it?
It’s charging is when they usually burn I believe, that or physically damaged.
Honestly the lithium packs for my Milwaukee drill make me nervous, a larger one even moreso
The cables are a bit of a pain and not cheap, but not even close to the cost of the windlass. If it’s the large cables you want to avoid, many remote a battery close to the windlass as the cables to charge it can be much smaller.

[swisel]

[QUOTE=a64pilot;3048675]No reason why it shouldn’t work if the battery is large enough.
Where and how are you going to charge it?

This would pretty much have to be back at the inverter to recharge. I'm not sure how long that would take but it should be ok by next morning to haul anchor again.

[john61ct]

A jumpstarter that fits in your pocket won't run that kind of current for long.

Cranking is very high amps but for half a second only.

A couple tool packs' worth might do it, measure Ah consumed in a worse case "session" and provide 3+ times that capacity.

With LFP 4S matches 12V, but other LI at nominal 3.6 - 3.7 probably want to go to nominal 24V with 7S.

Then you need to get it recharged maybe 29V.

Running wires is a once off pain, maintaining a consumable pack a bigger one, ongoing.

[44'cruisingcat]

How much power does a normal anchor retrieval use though? Maybe 3 minutes at around 50 amps, and a few seconds at 100? Maybe 2 or 3 amp hours?

I

[swisel]

Originally Posted by john61ct

A jumpstarter that fits in your pocket won't run that kind of current for long.

Cranking is very high amps but for half a second only.

A couple tool packs' worth might do it, measure Ah consumed in a worse case "session" and provide 3+ times that capacity.

With LFP 4S matches 12V, but other LI at nominal 3.6 - 3.7 probably want to go to nominal 24V with 7S.

Then you need to get it recharged maybe 29V.

Running wires is a once off pain, maintaining a consumable pack a bigger one, ongoing.

I think we may be looking at different battery packs. What I was looking into was something a bit more substantial than one that fits in your pocket. There wasn't a whole lot in the way of specs on Amazon but it was more like 40 AH @ 12 volts. I'm sure there are bigger ones as well. I may have exaggerated a bit on weighing a bit more than your morning paper but still something that wouldn't break much of a sweat moving it aft from the bow.

[john61ct]

So if your heaviest session uses say 10-15Ah that would be fine.

Just be aware most such units are "optimistically" rated, market's full of lying scammers, so read the fine print and do a cap test upon receipt in case so bad you want to return it. A DIY with good quality cells would be ~$300 or more.

[Rapanui]

Just to add to John61CT comments:

• Most Lithium 12v jump start devices, the Ahr capacity quoted is for the capacity for at the single cell voltage, say 3.4V, so at nominal 12v you have 25% of the stated capacity.
• Nearly all the 12v jump start devices are Lithium polymer and a lot less safe than LiFePo4 plus very few are assembled by reputable names so it makes finding a good one a lottery. It is very instructive to read the 1* user reviews of what can actually happen.

I have considered using 6off 40 Ahr Lithium Titanate (LTO) cylindrical cells to make a 12V pack for local powering of the windlass and engine start batteries. The advantage is that 6S LTO is even safer than LiFePo4, can be floated indefinitely at lead acid charging voltages, has a ridiculous cycle life and works at very low temps. They are bulkier and heavier than LiFePo4 though.

[tkeithlu]

I've tried various work-arounds in various situations, not this one but parallel to it - where you don't have enough power (or the right kind, AC v DC) where you want it. The only ones that really have worked for me are either laying new big cables or placing remote batteries of the same sort as the source (usually the house bank). Everything else gets too complicated and as suggested, one more maintenance item.

The jump-em-off pack would work, but how many times will it re-charge with your using it for lots of amp minutes rather than the expected one-second pulse?

[john61ct]

The nominal (midpoint) voltage of the LI chemistries usually used in the smaller portable powerpaks is 3.6-3.7V, so if rated 18000 mAh (18Ah) that's actually ~4.8Ah at 1S

but IRL usually much lower, you really need to perform a cap test at your usage voltage and current rate.

The only guarantee is that you will be disappointed, given the price you paid.

____
LTO is indeed a fantastic chemistry to use if high density is not required and you can find a good source like Toshiba SCiB reasonably priced.

But 12V nominal is tricky, as with the other non-LFP lithiums, usually 5S

6S being a bit too high for many load devices. 24V at 11S is better.

[a64pilot]

Another problem is the rather large inefficiencies from recharging it, overnight use of an inverter will chew through even a rather large battery bank because you have inverter inefficiencies, Charger inefficiencies and battery inefficiencies, add them all up and I wouldn’t be surprised if you have to have twice the power that ends up being stored in the battery.

[john61ct]

Originally Posted by a64pilot

Another problem is the rather large inefficiencies from recharging it, overnight use of an inverter will chew through even a rather large battery bank because you have inverter inefficiencies, Charger inefficiencies and battery inefficiencies, add them all up and I wouldn’t be surprised if you have to have twice the power that ends up being stored in the battery.

Maybe I missed the references to specific charging arrangements that would be inefficient like that?

Why would an inverter be involved? that would indeed be sub-optimal, I would assume all DC unless required to be otherwise.

And certainly charging from another bank's stored energy is indeed very wasteful should again be avoided unless required for some reason.

All depends on the given setup's details, but it should not be a major problem making the portable pack charging process efficient. Depending on its target voltage relative to the Starter or main House, there may not even be a need for DC conversion and a simple HVC could terminate the charge cycle.

[john61ct]

Originally Posted by swisel

This would pretty much have to be back at the inverter to recharge. I'm not sure how long that would take but it should be ok by next morning to haul anchor again.

Aha, yes this would waste a lot of energy.

Of course if your House is LFP and you usually have lots of easy inputs on demand, that may not be an issue.

But if living off grid mostly solar, you def don't want to do it that way.