Dumb question, from Ed....

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Re: Dumb question, from Ed....

Postby mattcarr » Fri Nov 12, 2010 9:41 am

Hi Jeremy, can I ask what the nominal voltage and capacity of your pouch pack is please. Is this a pack you have put together yourself?



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Re: Dumb question, from Ed....

Postby Jeremy » Fri Nov 12, 2010 4:00 pm

Hi Matt,

That pack on the folding bike is a 37V nominal (more like 38 to 39V most of the time) 10Ah pack. It's made from 4 of these LiPo packs: http://www.hobbycity.com/hobbyking/stor ... oduct=8581 (which were about $38 each on sale when I bought them - watch that page on Hobby King, they sometimes make you an offer if you stay on the same item for a few minutes!). Four packs, two 6S capable 5A balance chargers, a handful of connectors and postage came to around £160, delivered to my door.

The pack is simply plugged together, as two pairs of packs paralleled and then the sub-packs connected in series. The packs already have connectors, so all you need to buy are some matching ones to make up the leads to connect the packs together. I made up two 6 way Y leads to connect the balance leads together in each paralleled sub pack, plus some power Y leads to connect the sub-pack power leads in parallel.

I charge the pack as two separate 5S, 2P packs (effectively two 18.5V 10Ah sub-packs), using the pair of 5A balance chargers. The chargers need a 12V power supply - I happened to already have a spare one - and will charge an effectively flat pack in less than two hours. So far I've not used more than about 4 or 5 Ah at a time from the pack, so topping up has only taken less than an hour. The chargers I used are these: http://www.hobbycity.com/hobbyking/stor ... duct=11060 They are cheap, but have a really crappy internal fan - both of mine have given fan problems and I now just have them fitted over the power supply case (which has it's own fan) and blow air through them that way (seems OK so far).

The pack is made up by wrapping the sub packs in thin closed cell foam (the white packing stuff) then tightly binding the whole lot together with reinforced packing tape. I then made up a canvas bag by simply glueing black canvas around the pack using Copydex. The canvas is wrapped just like you'd wrap a present, but with care to keep all folds pointing down or under the pack. Copydex bonds ordinary cotton canvas in a few seconds with lots of strength, making this an easy and quick way to cover something. I left the front partially open with an envelope type flap, so that I can tuck the wires and connectors away inside when it's not being charged. To add some extra protection I glued a bit of wetsuit neoprene sheet on the bottom surface, just to absorb some of the road shock and give the pack a bit better grip on the alloy platform I made to hold it. The pack size is approximately 160mm long, 100mm wide and 85mm high.

All told I'm pretty pleased with it. It's about two thirds the size and weight of the 36V 10Ah Ping pack I've been using for the past couple of years and gives masses more performance. The first time I took the bike out with this little pack I was pretty surprised, as I was expecting it to be slightly slower than the Ping LiFePO4 pack (because its a volt or two lower in nominal voltage). When it popped the front wheel off the ground going up my drive I was more than a bit surprised! It does around 22 to 23 mph on the level and the limit on hills is keeping the front wheel down - being a folder it tends to be a bit light on the front wheel anyway, not helped by having lots of torque from a battery pack that's capable of comfortably delivering around 200 amps (not that I'm using more than 30A).


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Re: Dumb question, from Ed....

Postby ex925 » Sun Nov 21, 2010 6:16 pm

Very grateful for the advice, folks, clarified my thinking, gave me alternatives from which to choose
Next step is to see what the thing is like with 4 YTs / Etek / 5117
Next, with 6 YTs / Etek / 72v Curtis ("Lead-Sled" at least, I expect!)
Then decide whether the bike is worth the cost of Lithium pack:
1 As is
2 Evolved, a bit
3 Not really, start again virtually from scratch with a "Feet-Forward" chassis
Hope to reach 4 YT stage before Christmas
Kind regards for all the help
More soonest

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