Lithium powerbanks vs marine lithium batteries

[Gedimin]

I shall state the obvious first: electrics is not my strongest side.

To give you background, on my small sailing boat, I have 2 lead batteries and an outboard engine to charge it. The plan is to add solar panel, so that I can stay off the grid (my home pontoon does not have power either). In the process, I realised that my batteries will not serve me for long, time to replace it.

I can obviously replace like for like and buy new lead batteries, about £80 each. Old technology, heavy, low efficiency. Looked at AGM and Lithium - way too expensive given the fact that I barely use electricity on board. I can start the engine with a cord, I rarely sail at night (barely any need too power navlights), don't have a fridge. Batteries do power my VHF and GPS, but these are backed up by portable radio and phone. Cabin lights - again, I have portables. This leads me to a point that I only need a powerbank to charge all of my portables.

And then I see a massive difference in cost:
- regular 20Ah powerbank costs about £30
- marine 20Ah lithium battery is £400-£500.

So my questions are:
- why on Earth this thing costs 15 times more?
- what is the right solution for me?

 

[Catalina36]

If you can replace the lead/acid battery more than a dozen times for the price of the lithium alternative, ie for at least the next 30 - 50 years, the right solution seems obvious.

 

[MarkCX]

Is the 20Ah regular power bank 5v or 12v?
If 5v and the marine is 12v, the marine one stores more than twice as much power. Doesn’t account for the price difference, but despite both being lithium, they may have quite different chemistries. As I understand it, the lithium batteries in a ‘device’ are quite different to the lithium ones used on boats.

 

[MonniotC]

Fit a 20 watt solar panel and pwm controller - about £50 in total. Problem solved.

 

[Poey50]

A powerbank generally refers to a battery delivering 5 volts to charge up mobile phones. I think you mean a 12 volt lead acid compared to a 12 volt lithium.

I don't think Catalina36's reply can be improved on. You do need to ensure that your can bring your lead acid back up to completely full charge preferably at least once every two weeks otherwise your battery will go downhill with sulphation. Your best bet, as others have said is solar. But the size of panel depends on how depleted your battery is when you leave it and how long before you use the battery again. Personally I'd be looking at something around 50 watts rather than smaller. That will give you a bit of headroom if leaving the battery fairly depleted.

 

[Gedimin]

Is the 20Ah regular power bank 5v or 12v?
If 5v and the marine is 12v, the marine one stores more than twice as much power. Doesn’t account for the price difference, but despite both being lithium, they may have quite different chemistries. As I understand it, the lithium batteries in a ‘device’ are quite different to the lithium ones used on boats.

I do mean regular 'device' powerbank with 5V. But I think storage is measured in Ah and it is the same, it's just voltage is different

 

[Gedimin]

Fit a 20 watt solar panel and pwm controller - about £50 in total. Problem solved.

What would you power with this setup? Standard lead batteries?

 

[MarkCX]

I think storage is measured in Ah and it is the same, it's just voltage is different

Using nominal values:
5v x 20Ah = 100Wh
12v x 20Ah = 240Wh

Power is in Watts which is independent of voltage. The 12v one stores more ‘power’.

If you connected a usb socket, to the 12v battery, it would last roughly twice as long.

 

[Gedimin]

I see there is a bit of a confusion, so I'll just reiterate my alternatives:

1. Same type of lead batteries, just buying new ones.
2. Get marine Lithium battery (prohibitively expensive, but lighter, more usable capacity, less trouble)
3. Get rid of any big batteries and power everything with portable powerbank (quite radical, but very affordable)

Solar energy is the way to top up anyway.

 

[Poey50]

Deleted as posts crossed.

 

[Poey50]

I see there is a bit of a confusion, so I'll just reiterate my alternatives:

1. Same type of lead batteries, just buying new ones.
2. Get marine Lithium battery (prohibitively expensive, but lighter, more usable capacity, less trouble)
3. Get rid of any big batteries and power everything with portable powerbank (quite radical, but very affordable)

Solar energy is the way to top up anyway.

If you can manage it then go for 3. The idea that lithium is less trouble is wrong. There is a mass of marketing kool aid around about drop-in lithium batteries. They have advantages but 'less trouble' is definitely not one of them. But as others have said lithium has nothing to offer in your circumstances other than a lighter bank balance and a potential world of pain.

 

[Poey50]

Sent in error.

 

[JumbleDuck]

Lithium powerbanks are generally only capable of small loads, typically 2.1A maximum. Almost all of them fiddle their specs by giving the "capacity" at 3.7V (the voltage the cells run at) and not at 5V (USB output) or 12V (sometimes). A lot of the adverts just plain lie anyway.

 

[TernVI]

Lithium powerbanks are generally only capable of small loads, typically 2.1A maximum. Almost all of them fiddle their specs by giving the "capacity" at 3.7V (the voltage the cells run at) and not at 5V (USB output) or 12V (sometimes). A lot of the adverts just plain lie anyway.

Very true.
I've got a lithiium power bank which claims to '5000mAh'. It puts out 5V, but the 5Ah is the size of the 3.7V or whatever battery.
I have another one which was sold as 4000mAh, which has a 2000mAh or so battery in it.
Still very useful and good value, I'm not complaining!

 

[MonniotC]

What would you power with this setup? Standard lead batteries?

The existing lead batteries.

 

[billcole]

A 12v lithium golf cart battery might be an option worth considering, and would be a middle cost option between your cheap powerbank and expensive "marine" battery.

 

[Poey50]

A 12v lithium golf cart battery might be an option worth considering, and would be a middle cost option between your cheap powerbank and expensive "marine" battery.

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.

 

[MarkCX]

If it’s only being used to charge a phone, tablet or whatever, and maybe run some interior lights, not a problem. But start using it for important stuff like VHF and navlights and other essential stuff, not good.

Even if you’ve got a handheld VHF, I know what I’d rather have in a tricky situation.

 

[GHA]

- marine 20Ah lithium battery is £400-£500.

Available much cheaper, £117.95
BMS built in.

I got a 6Ah and very happy with it, very useful for fiddling with electronics onboard - bought mostly to have a play with LiFePo4. Holds the voltage high right to the end. Gets charged with an ebay buck/boost.

LiFePo4 Battery 12.8V Lithium-Ion Iron Phosphate 12V Deep Cycle Heavy Duty | eBay

 

[Poey50]

If it’s only being used to charge a phone, tablet or whatever, and maybe run some interior lights, not a problem. But start using it for important stuff like VHF and navlights and other essential stuff, not good.

Even if you’ve got a handheld VHF, I know what I’d rather have in a tricky situation.

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.