e-bike battery for hookah dive system

[zeiler]

Thanks to everyone again for your advice and concern. And specifically to Caliban for the link to the Explorer cases. I will follow that up. We were considering using one of our Pelican cases on board which at the moment contain nightglasses and other things but I do not think they are as deep as those Explorer cases you linked. And no, we are seldom in marinas since we are mostly self-sufficient. In any case our crossing of the Indian Ocean next year will seldom give us the opportunity! This will change when we get to South Africa in November 2013.

Also to dnmum; charging the Lithium battery on board our sailboat is not a problem at all. And slow charging will suffice We have about 600 watt Solar capacity and another 400 from a wind generator (if the wind blows). We never use the yachts motor for charging only and have 800 Ah installed AGM LA battery capacity which in these sunny climes seldom drop below about 760Ah. Usage goes up while on passage if the wind is sufficient for sailing which for us it is most all the time. The autopilot, navigation instruments, lights etc and watermaker use add to daily consumption The boat is wired for 110v as we are from Canada and has a 1500w Heart inverter. I think our main usage is keeping beer (and veggies cool (-

And Gordo I believe it was re changing a through hull using a tarp. Good idea but we have no thruhulls if we do not count the prop shaft and the depth sounder's transducer as thruhulls. All hoses empty into stand pipes with failure of any one of them causing a break in the siphon.

Ebent suggestion of the Spare Air backup is excellent of course. Brownie Hookahs can be bought with them as part of the package. We opted not to do so since these cartridges need a high pres compressor to charge them and diving without tanks is one of the attractions of Hookah. Perhaps that is a mistake as these units are for emergency ascents and they may never be used thus one charge would suffice. But then I do not expect to have to dive on my anchor at 20 m very often at least not to the depth required to possibly free it. If I had to do that I would do it with a full battery! But still I am reconsidering the Spare Air.

I hope I have answered all those that asked a question and want to once again say thanks for all your input. Looking fwd to more if anyone has other comments or questions. I will be making the decision on the battery soon.

 

[etriker]

My way of thinking is this.

Li ion cell build quality has more to do with the cell being safe than its chemistry.

This may be safer

http://www.amazon.com/PROTECTED-3100mAh-18650-Industrial-NCR18650A-Panasonic/dp/B0062ANS7O

Than this

http://www.ebay.com/itm/12-PCS-High-power-Lifepo4-18650-cells-A123-18650-Replacement-/190728831029?pt=US_Rechargeable_Batteries&hash=item2c68530035

They all contain stuff that will flame. Some contain it better than others.

I like A123. They are high quality.

http://www.buya123batteries.com/

> 7500 cycles ? WoW !

 

[dnmun]

i would recommend using a wattmeter too in order to follow the state of charge of the battery pack, and also you should have a voltmeter on board in order to diagnose problems when they arise.

we can explain how to install an emergency bypass for the BMS too when you buy a pack. avoid buying a Vpower pack though, they do short out regularly.

 

[Gordo]

One point to remember with any "Spare Air" safety device is they will often fail from being in the water and never used. Our commercial guys kept a thin plastic bag on them (a violation of regulations) because they failed from sand getting in. Test the second stage regulator on the Hooka from time to time.

But still I am reconsidering the Spare Air.

 

[zeiler]

I bit the bullet last night and ordered a 20Ah 24v battery from Cell-Man. He will use prismatic A123 pouches in a 8s1p configuration and include a BMS. It will all be contained in a plastic case which I may waterproof or perhaps put in the Explorer case or equivalent suggested earlier. I also received good feedback from Andy at FalconEV but in the end decided on the A123 cells.

I had been tempted to make my own battery in part from reading information on this site and in part to get an easily stored and waterproof unit using locally available materials. My idea was if I could find circular cells to stack them in layers inside a PVC pipe, separating each layer with a copper disc which I intended to tin to avoid corrosion. (on our sailboat I have found that liberal use of Lanolin does wonders avoiding corrosion and we now use it on anything electric or electronic. There is not a flashlight, LED or otherwise or for that matter anything with a battery in it or a plug into a socket that is not greased up with the stuff.)

PVC pipe is wonderful stuff. Easily machined and available in many sizes with tight caps and in Thailand in bright blue! If I was not able to find copper plate I would cut discs out of Polythene cutting boards, also available in many thicknesses on this island and machine them to hold the batteries in place with a copper washer inbetween each stacked cell.

The desired capacity would dictate the diameter of the chosen pipe and the length the voltage. I would leave the centre free to bring up the negative and possibly store a BMS and use threaded rods to tension the whole assembly between upper and lower discs with a disc of rubber to provide springiness.

The lower cap would have been glued and the upper left removable. Leads would have come out of the top of the cap sealed in with PVC dope and the leads would have been long enough inside to allow removal of the cap and unplugging the unit from the cap.

The whole assembly would have been easily removed from the 'case'.

Of course i was probably reinventing the wheel having never been exposed to the band of enthusiast on this site! (-:

So why did I decide to go with Cell-Man? I had fun drawing up and imagining this kind of thing but in the end I realized that I am too new at this and lack the electronic apparatus to do a reliable job, essential as many of you pointed out, for my application. Paul at Cell-Man pointed out that they carefully match their cells for each pack by measuring the AC impedance at 1000Hz which i could not do on the boat or for that matter on this tourist island! Also I did not know where to find the circular cells I needed until I read the links provided by Etrike and that happened after I told Cell-Man to go ahead (-: . And finally I ran out of time as we will be leaving this island to head across the Indian Ocean in a few weeks.

I hope to be able to report back to this site in about a years time saying everything worked out as hoped. And I suppose I should apologize for being somewhat off topic for this E-bike site. Thanks all again for your contributions.

 

[docnjoj]

Hey zeiler! That battery choice seems like a really good one. We may build our own batteries to run e-bikes, but I would not count on them to run a breathing device underwater. It's a bit more critical tha having to pedal home a few miles. Excellent choice!
otherDoc

 

[SamTexas]

Good choice on the A123 battery pack. I don't think you can find a better battery in terms of performance, quality and safety.

BUT if I were in your shoes, I would skip the BMS. Instead I would ask cell-man to provide 9 sturdy balance wires in addition to the normal 2 power wires. A BMS in my opinion is weakest point in an ebike battery. I would not trust a BMS to either balancing the cells or supplying the power I need when I need it. The last thing I want is for the BMS to cut power while I am 20 meters deep.

And if I don't want to be bothered with manual cells balancing then I would invest in a good balancing charger.