Lithium powerbanks vs marine lithium batteries

[KompetentKrew]

I have four of these 26000 power banks, which are brilliant - I can run my laptop off one for hours (maybe 4 hours off a full charge, I guess?) and can charge my phone multiple times from one. When I had poor reception in an anchorage I plugged my phone into one, put them in a plastic bag and I hoisted it up the mast - pages loaded noticeably faster.

They won't hold a candle to full-sized lithium batteries though - they have just the same energy density, they're just smaller. Probably the reason that power banks appear cheaper (per watt) is that the battery management circuitry deals with much lower currents. Also they're manufactured in much larger numbers. And, like @JumbleDuck, I've never believed the sellers' numbers anyway - they're competing on Amazon where people (me included) buy whatever product shows the biggest number for the cheapest price.

I don't believe there are really three choices here, @Gedimin, only two - lead acid or lithium, and what size of battery you can afford.

 

[billcole]

Here's some blurb from a golf-cart LFP on Amazon.

"These batteries can be stored in any state of charge without worry of degradation. Another advantage is that running the battery completely down will not damage the battery at all, unlike the SLA and Gel batteries, since it has a low-voltage disconnect circuit."

What should the OP do when it unexpectedly disconnects? The internal BMS only has the job of protecting the battery, it doesn't care about the user. These are put back on mains charge after a round or two of golf and swapped for a charged one. The worst that can happen is you walk back to the clubhouse.

But any battery will run down and stop powering things, whatever the chemistry. you wont get much use out of a VHF thats connected to a dead lead acid battery either.

 

[Poey50]

But any battery will run down and stop powering things, whatever the chemistry. you wont get much use out of a VHF thats connected to a dead lead acid battery either.

You can recharge a lead acid battery straight away. LFP drop-ins do not separate their charge and load terminals (none that I know of, anyway) so a BMS high voltage disconnect means you can't discharge it with any loads and a low voltage disconnect means that you can't recharge it straight away. This is a well-known problem with drop-in LFPs in marine installations except (apparently) to all those seeking to market their drop-ins to boat owners. If you want to charge one from an alternator then then a sudden high voltage disconnect can take out the alternator diodes and expensive electronics if they share a circuit.

This from Rod Collins of 'Marine How To' covers it when reviewing problems of drop-ins.

"#5 Non-Communicable BMS – This one is perhaps the most frustrating aspect on-board a cruising boat. For a trolling motor, who cares? It’s not powering anything critical. For a house battery, on a cruising boat that ventures off-shore, and is powering critical navigation and safety equipment, this can create a dangerous situation. A non-communicable BMS is one that can not communicate externally with the vessels charge and load systems, or even you the owner. It has no means of externally communicating or sending/sounding warning alarms or activating relays/triggers to properly and safely disconnect charge sources or give ample warning of an impending BMS disconnect. Some batteries are now featuring Bluetooth monitoring but this still requires you the owner to be watching it."

 

[billcole]

Yes, if you don't have it powering anything essential then fine. My point being that you have to plan for it giving up, and for a time, being unreachable.

But presumably if the regulator on the outboard alternator was good enough, or a suitable external regulator was added to it, then that chould be a source of power if the battery was flat, either that or use two batteries and a change over, although from the description in the original post it doesn't look as if that would be necessary.

 

[Gedimin]

Ok, I think I made my mind thank you everyone!
I'll replace current SLA batteries 85Ah with similar ones, one by one. Then install removable 50W solar panel along with 10A MPPT charger to keep batteries topped up between sails or at anchor. Am I right that this type of battery can't be fully drained, but is doing fine when plugged to solar for prolonged time? MPPT should regulate that too, right?

 

[Poey50]

Ok, I think I made my mind thank you everyone!
I'll replace current SLA batteries 85Ah with similar ones, one by one. Then install removable 50W solar panel along with 10A MPPT charger to keep batteries topped up between sails or at anchor. Am I right that this type of battery can't be fully drained, but is doing fine when plugged to solar for prolonged time? MPPT should regulate that too, right?

As well as new kit you need to learn more about the use and care of batteries on boats. They are easy to kill if you don't understand the issues and you will be back to square one. Someone will probably be able to recommend some reading.

 

[Gedimin]

I'd love to find some simplified reading on this. My knowledge of electric is very fragmented and dates back to school as you can see ))

 

[Poey50]

I'd love to find some simplified reading on this. My knowledge of electric is very fragmented and dates back to school as you can see ))

Spend an hour Googling and browsing and find the right level of information that fits onto your present knowledge. Youtube has instructional videos on almost everything.

 

[JumbleDuck]

I'd love to find some simplified reading on this. My knowledge of electric is very fragmented and dates back to school as you can see ))

"Don't flatten the batteries."

That's about it, really.

 

[MarkCX]

Lots of people suggest not going below 50% charge - I try not to go below 60%.

A (very) crude method is with a simple voltmeter. If a rested battery is <= 12.1v don’t use it, charge it. A fully charged battery will be >=12.6v. Like I say, it’s crude but better than nothing. I used to do this and my batteries were fine for several years. I now use a proper battery monitor.

I’ll leave it to others to give better suggestions.

 

[Catalina36]

You can recharge a lead acid battery straight away. LFP drop-ins do not separate their charge and load terminals (none that I know of, anyway) so a BMS high voltage disconnect means you can't de-charge it with any loads and a low voltage disconnect means that you can't recharge it straight away. This is a well-known problem with drop-in LFPs in marine installations except (apparently) to all those seeking to market their drop-ins to boat owners. If you want to charge one from an alternator then then a sudden high voltage disconnect can take out the alternator diodes and expensive electronics if they share a circuit.

This from Rod Collins of Marine How To covers it when reviewing problems of drop-ins.

"#5 Non-Communicable BMS – This one is perhaps the most frustrating aspect on-board a cruising boat. For a trolling motor, who cares? It’s not powering anything critical. For a house battery, on a cruising boat that ventures off-shore, and is powering critical navigation and safety equipment, this can create a dangerous situation. A non-communicable BMS is one that can not communicate externally with the vessels charge and load systems, or even you the owner. It has no means of externally communicating or sending/sounding warning alarms or activating relays/triggers to properly and safely disconnect charge sources or give ample warning of an impending BMS disconnect. Some batteries are now featuring Bluetooth monitoring but this still requires you the owner to be watching it."

I'm grateful to you for that information. I knew that there were some complications attached to operating some Li systems but I had no idea just how complicated. Simple soul, me. Discharge the battery, recharge it. I really couldn't be done with all that nonsense.

 

[Poey50]

"Don't flatten the batteries."

That's about it, really.

Ha ... sums it up. Plenty think a bit about the bottom end, not so many the top of the curve. See also the missionary work of GHA.

 

[Poey50]

I'm grateful to you for that information. I knew that there were some complications attached to operating some Li systems but I had no idea just how complicated. Simple soul, me. Discharge the battery, recharge it. I really couldn't be done with all that nonsense.

Genuinely, one of the advantages of lead acid over LFP is that they will take a fair bit of neglect.

 

[Plum]

. Batteries do power my VHF and GPS,

You said the batteries only power your VHF and GPS and your outboard has a cord start, so why do you need two 80Ah batteries? You can get two 25Ah mobility scooter batteries for £80 the pair, keeping one as backup, plus a 20W solar panel, should be plenty for those two devices plus phone charging. These are deep discharge batteries so you can get more out of them.

Www.solocoastalsailing.co.uk

 

[billcole]

You said the batteries only power your VHF and GPS and your outboard has a cord start, so why do you need two 80Ah batteries? You can get two 25Ah mobility scooter batteries for £80 the pair, keeping one as backup, plus a 20W solar panel, should be plenty for those two devices plus phone charging. These are deep discharge batteries so you can get more out of them.

Www.solocoastalsailing.co.uk

And at least one of your two could even be a lithium mobilty scooter/golf cart battery.

I really think the disadvantages of Li are being overstated here. The built in Battery management will prevent it being over charged or over discharged. As long as you don't connect it to a higher voltage charging source than specified by the manufacturer (for example by trying to use a regulator designed only for lead acid batteries) then all will be fine.

Lithium batteries are way lighter than lead, and don't have to be kept upright in use or in transit, which means in your circumstances, that taking the battery home to recharge it is an easy option. Conversely if you choose to leave it on the boat then it won't self discharge anywhere near as quickly as a lead one would.

I accept the disadvantage of lithiums is that the stability of the output voltage means that you can't just stick a voltmeter across it to see how charged it is, since the voltage doesn't vary as much a a lead battery, however, if you have two batteries (not necessarily even of the same capacity) then you can keep a reserve in case you flatten one. The golf cart batteries have a very quick to use spring loaded T shaped connector which you can't connect the wrong way round, so are easy to remove for swapping or for off boat charging.

 

[Poey50]

And at least one of your two could even be a lithium mobilty scooter/golf cart battery.

I really think the disadvantages of Li are being overstated here. The built in Battery management will prevent it being over charged or over discharged. As long as you don't connect it to a higher voltage charging source than specified by the manufacturer (for example by trying to use a regulator designed only for lead acid batteries) then all will be fine.

Lithium batteries are way lighter than lead, and don't have to be kept upright in use or in transit, which means in your circumstances, that taking the battery home to recharge it is an easy option. Conversely if you choose to leave it on the boat then it won't self discharge anywhere near as quickly as a lead one would.

I accept the disadvantage of lithiums is that the stability of the output voltage means that you can't just stick a voltmeter across it to see how charged it is, since the voltage doesn't vary as much a a lead battery, however, if you have two batteries (not necessarily even of the same capacity) then you can keep a reserve in case you flatten one. The golf cart batteries have a very quick to use spring loaded T shaped connector which you can't connect the wrong way round, so are easy to remove for swapping or for off boat charging.

I wonder what disadvantages of drop in LFP you think are overstated? Is there anything I've described that is factually incorrect? As said, if used for non-essential systems then fine. If you can safely cope with the unpredicted withdrawl of a shut down battery and can swap it over when convenient and at no risk .. also fine. If you want to charge onboard and have charging that you can fully control with no long absorption period, no temperature compensation, no float, and no equalisation, thats fine too. A lot of ifs, though.

 

[billcole]

I wonder what disadvantages of drop in LFP you think are overstated? Is there anything I've described that is factually incorrect? As said, if used for non-essential systems then fine. If you can safely cope with the unpredicted withdrawl of a shut down battery and can swap it over when convenient and at no risk .. also fine. If you want to charge onboard and have charging that you can fully control with no long absorption period, no temperature compensation, no float, and no equalisation, thats fine too. A lot of ifs, though.

So to precis...don't have anything that you can't sail without for 45seconds or so while you move the T-bar connector across then, and use a lithium specific charger or charge regulator to supply the power for your lithium battery's built in charge management electronics.

In the OP's case, referring back to his OP, we see that the devices he's got are unlikely to discharge a 20something Ah battery in a day's, or even a weekend's sailing, so unexpected shutdown is unlikely to happen, and anyway, he's unlikely to get lost in 45 seconds or be unable to wait that long to make an essential VHF call, which is what I meant by overstating the disadvantages, not that anything you said was actually untrue.