Swallow Yachts Association
Swallow Yachts Forum => Technical => Topic started by: Llafurio on 20 May 2021, 11:15
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Hi,
a friend with a Cape Cutter on a mooring has to replace his Pb battery. His power consumption requirement is low, mostly fishfinder and GPS, and some VHF. No space on deck to fit solar panels for recharging so needs to recharge at home.
I recommended him to look at these fairly powerful and cheap Li-Ion "Power Banks" widely available today. Has anyone here tried those yet? For instance: https://www.amazon.co.uk/dp/B00YP823NA?tag=aagbp-21&ascsubtag=trd-us-4673929896086962000-20&geniuslink=true . C.
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I use a couple of 20000mah power banks for emergency phone/tablet power. But at 50000mah that is a pretty good back up. As a main power source that sounds pretty good just need to check the amperage available and required. I can't see anything to stop you using them otherwise, nice thought.
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I have read somewhere (probably an expensive power pack supplier) that cheap power banks have inadequate electronic protection built-in to prevent them overheating and worse, catching fire :-\. I also know international carriers such are increasingly reluctant to transport lithium power packs, especially by air.
I don't know how much of a genuine concern this is.
Matthew
BR20 Gladys
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Tim, Matthew,
thanks.
I have abandoned the idea in the meantime.
Firstly, I read that these powerbanks have an internal voltage of 3.7 V, and they cascade that electronically up to 12 V, but incurring significant losses on the way. So, even if they say to contain 50,000 mAh @ 3.7 V, that figure may well dwindle to 40,000 mAh or less @ 12V DC.
Then, for the example product linked above, the output at 12V DC is limited to 2.5 A, and that will not power an installed VHF during "Transmit".
Re the fire risk of Li-Ion power banks, I think that is something quite remote, and I would not be too concerned about that. We all carry Li-Ion battery powered devices on us and do not really think twice about the inherent risk of that. My waterproof navigation phone has a 10,000 mAh battery, quite near to a power bank, and I would not leave it behind for the theoretical fire risk.
C.
P.S.
I read some more about "mAh". Disappointingly, the seemingly impressive "50,000 mAh" of the quoted power bank, multiplied by the internal voltage of 3.7 V equal an energy content of only 185 Wh, and if that is then cascaded up to 12 V, and counting in the losses incurring on the way, the usable energy content @ 12V is not over 150 Wh. Compare that to the theoretical 240 Wh energy content of the 40 quid 12V 20 Ah Pb battery, and the choice is clear.
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If this idea is resurrected then I recommend a self-contained 12v lithium battery. I used a Tracer battery on my BRe (depth sounder, ballast pump plus charging for phones, etc) and took this off for charging when I wasn't on the boat. This more than met my requirements.
https://www.tracerpower.com/tracer-lithium-polymer-battery-packs.html
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... and there is always the trusted sealed 12 V 20 Ah Pb battery for under 40 quid. Heavier, but still well portable. https://eu.nkon.nl/rechargeable/lead-acid-batteries/12v-vrla/vmf-12v-20ah-loodaccu.html
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If this idea is resurrected then I recommend a self-contained 12v lithium battery. I used a Tracer battery on my BRe (depth sounder, ballast pump plus charging for phones, etc)
Another vote for Tracer, and hang the cost! They claim to be IP64 splashproof, which (without going into embarrassing details) I can confirm. They are also very long lived (so far).
One thing that I don’t understand is that despite the dramatic fall in the cost of lithium cells, the price of Tracer batteries seems to have hardly moved in the seven years that I have had mine.
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... for the example product linked above, the output at 12V DC is limited to 2.5 A, and that will not power an installed VHF during "Transmit". ...
12V x 2.5A = 30 V.A = 30W
Not enough to run a ballast pump.
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I've just used my Tracer 12V 24Ah battery to run my Garmin GPS/fishfinder and Tacktick NMEA transmitter continuously for three days. I don't know how accurate the battery's inbuilt meter is but at the end of that period, it was showing two out of three green bars remaining, with two red ones in reserve.
My back of the envelope calculations suggest that with a typical combined draw of about 0.7Ah for both machines, the battery ought to keep going for around 35 hours. A few hours of recharging in the Kentish sunshine using a 60W solar panel and it was back up to full capacity.
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12 V x 24 A.hr x 3600 secs/hr = 1036800 J ~= 1,000,000 J
3 days = 259200 secs ~= 260,000 secs
Energy available per second (J / sec = W) over 3 days
= 1,000,000 J / 260,000 secs ~= 4 W
4 W at 12 V = 4 / 12 = 0.33 A
[Alternatively: 24 A.hr over 3 days = 24 / 72 = 0.33 A]
[0.33 A at 12 V = 4 W]
But given the accuracy / veracity of the manufacturers' claims it matters not the underlying technology: 24 A.hr at 12 V is the same Pb or Li. Battery weight is a factor if you're having to carry it about for recharging but not really, otherwise, in a boat. Number of recharges per capital cost, resilience to repeated deep discharge, together with veracity of manufacturer's Ah claim, that's the money issue.
Except that for the power bank referenced initially above, the max output is 2.5A at 12V or 30W which means nothing more than 30W can be drawn at any time from the power bank.
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24 A.hr at 12 V is the same Pb or Li.
Not quite. For a lithium battery it is ok to to have a state of discharge of 0% without causing damage, most lead acid batteries will get irreversibly damaged when the state of charge gets lower than 50%. (30% for AGM batteries)
So a 24Ah lithium battery will give you roughly twice the amount of energy compared to a 24Ah lead acid version.
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Not to mention that Lithium batteries frequently have higher voltages.
24A x 14.2V (LifePo4 battery) equals 340.8 VA
24A x 12.6V (Lead acid) equals 302.4 VA
Again the Lithium battery wins, it is not merely a matter of weight and price.
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A 20Ah battery isn't a 20Ah battery unless it can deliver 20Ah. It is true that lead acid batteries are damaged by a discharge which is too deep but if that happens to a "20Ah" lead acid battery after 20Ah has been taken from it then it isn't a 20Ah battery. That one can take a properly labelled 20Ah lead acid battery and destroy it by taking 30Ah from it is true, but it doesn't mean that it doesn't reliably deliver 20Ah. Also, when one's device wants 12V and you deliver 14.2V to it, energy is wasted. Generally speaking, the extra voltage isn't usable by a 12V electronics device, or by a cheap LED driver. Incandescent bulbs will shine brighter (and last only a fraction of the time) on the higher voltage, but are terribly inefficient.
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A 20Ah battery isn't a 20Ah battery unless it can deliver 20Ah
True.
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So a 24Ah lithium battery will give you roughly twice the amount of energy compared to a 24Ah lead acid version.
There are so many advantages to lithium batteries. The only downside I can think of (apart from the high initial cost) is that towards the end of the discharge cycle, if you’re not paying attention you can get caught out as the battery suddently runs out of charge. At least with lead batteries you get plenty of warning as they peter out slowly.
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We’ve been using a caddy lithium battery comes with its own charger, 12v native voltage, 20A delivered power, water safe t-bar electrical connection and it’s tiny. All in with the connector, charger and neoprene case I think it was £160.
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We’ve been using a caddy lithium battery comes with its own charger, 12v native voltage, 20A delivered power, water safe t-bar electrical connection and it’s tiny. All in with the connector, charger and neoprene case I think it was £160.
That sounds like a Tracer battery, in which case you must have bought it several years ago - the 12V 24Ah model with all the features that you describe currently retails for a whopping £355. This is a big increase on five years ago when it sold for about £250. The increase is despite the price of lithium cells falling as more and more lithium gigafactories are opened up.
However, it seems that you get what you pay for. My Tracer battery has been going strong for seven years now in pretty damp and sometimes very wet conditions. Its neoprene sleeve rotted away because of the conditions but was replaced free of charge. By contrast, I also had a much cheaper Ultramax lithium battery of similar capacity. It couldn’t cope with being under my foredeck and its integrated battery manager packed up after only 12 months, making it a useless and potentially toxic brick.
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Is this a "caddy battery" in terms of power for golf trollies/buggies?
Like this?
https://www.planetgolfuk.co.uk/golfstream-caddy-cell-lithium-battery.html
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I’m flabbergasted to receive a ‘Black Friday’ offer of the Tracer 12V 24Ah LiFePO4 battery that I bought for about £280 nine years ago (and still going strong). The offer, which says it is at 10% off, is for a princely £469. And I thought that lithium cells were supposed to be getting cheaper!
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Lithium batteries in "conventional form factor" arrangements (as opposed to "power pack" type units), particularly the "non-smart" type do seem to be getting cheaper, imho?
I recently obtained from Sterling Power (whom I consider to be a reliable UK based dealer, and designers/manufacturers of electrical power products with a good long-term reputation) a 100 AH LIFEPO4 battery for £340. Obviously manufactured in China, as are many of their other products, but SP have been around for years, and are still something of a family firm; excellent to deal with. 5 year warrantee.
This will replace my 100AH ""Rolls" brand AGM lead acid house battery. No idea how old this is, but should still be OK for another season. However the peltier type "picnic box" fridge/heater really hammers it (also spoils your breakfast if you unwittingly press the red "heat" button, rather than the blue"chill" button! >:(
LIFEPO4 only a little smaller, but approaching twice the useable power, at half the weight.
I didn't want want/need a Bluetooth battery monitoring system (I have a Victron BT mains supply/charger, and while the BT is interesting, it's a bit of unnecessary faff, imho). Note also that SPs Blue Tooth BMSs are not covered by the warranty...
I have a hard wired BMS, and a SP 12v 25A Battery-to-Battery charger that cross-couples the start (lead acid) and house batteries, charging the house (now Lithium) from the engine, and the starter (conventional Lead acid) from the solar if/when the power is available from each source. The Victron couples any shore mains to the Lithium, and is continuously rated at 15A.
Not sure that the above setup is appropriate for open boats, but should suit cabin boats?
Suspect any LIFE04 weight savings will be absorbed by the BMS, B2B charger and shore power charger (luckily all in the same relatively central, low down locker)! However, the master plan is that I won't need to so-closely manage Mrs SSs use of the fridge etc!
I'll keep you posted as to how it goes...
What does Swallow fit to a 26 these days?
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While the powerbank which started this thread did not offer enough Amps to power a fixed VHF,
there are now devices which offer plenty of that - Jump Starters.
Like this one here. An agreeable capacity of around 300 Wh, and comes with USB ports. Only € 88.00, where I live.
https://www.amazon.de/gp/product/B0BD36YJVK/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1
C.
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The above mentioned car jump starter has a few drawbacks. The peak power supply of 5,000 Amps comes from a capacitator which is charged fairly slowly. Good for power boost, but possibly not good enough for a prolonged 25 W VHF transmission.
But I think I have now found another power bank better suitable, and not much dearer, at € 120.00. https://www.amazon.de/gp/product/B089VKVYGC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 .
At that price / performance level, these new LiFePo batteries are definitely the way to go.
C.
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We seem to be straying towards this earlier thread, which remains useful I think?
https://www.swallowyachtsassociation.org/?page_id=17&URL=https://www.swallowyachtsassociation.org/smf/index.php?topic=1819
Update on my power banks...the "trad" Ring lead acid long since scrapped. The Jaber brand power pack off Amazon didn't last two winters...It died, rather inconveniently, mid start of my car.
I stripped the unit down (unfixable, obviously!..and I survived, see below... ) and like Llafurio, came to now better understand that it's capabilities derive not primarily from a battery, but some sort of boosting capacitor (luckily, capacitor was recognised due to my experiences, as an Engineer- spectator, with VS Power drives at work). Hence Jaber pack probably not much use in my boat (then a BRex) for powering electronics long term? However, I stand to be corrected; no doubt they have evolved/improved meanwhile.
I later set up a 4AH (18v) cordless tool battery to run a NASA sounder (proprietary adapter shoes are available for most brands) Whilst I had problems, they were not with the battery (but with hull fire-thru), this seemed more successful than the jump start, and gave a steady 12v output as well as a USB socket. I see you can now get 20AH batteries in some brands (but not 12v). My guess would be that it would be this shoe type adapter/voltage "step down transformer" that would be the new weak point?
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I have now moved to a 299Wh LiFePO Power Station with several in- and outlets, especially one 12V DC @ 60W, and one 220V AC @ 300W. The thing is well built, small, and has a carrying handle, very convenient.
For € 101.00, delivered .
https://www.amazon.de/dp/B0CR6GBTXD?ref=ppx_yo2ov_dt_b_product_details&th=1
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a friend with a Cape Cutter .... No space on deck to fit solar panels for recharging
Slightly off topic, but as I have a Cape Cutter I can confirm that at 50W solar panel fits nicely between the forehatch and samson post. I have fitted this one:
https://www.photonicuniverse.com/index.php/en/catalog/full/509-50W-Reinforced-narrow-semi-flexible-solar-panel-with-a-durable-ETFE-coating.html
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I think that the 288Wh Tracer lithium battery that I bought years ago has become ludicrously expensive compared to the competition (£534 delivered) because Tracer products are now used as standard by the film industry, police, special forces etc. Think of a number and treble it.