Swallow Yachts Forum > Technical
"Power Bank" to replace Pb battery?
Llafurio:
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.
TimLM:
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.
Matthew P:
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
Llafurio:
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.
Jonathan Stuart:
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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