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Old 01-06-2020, 02:15 PM
Jim UK Jim UK is offline
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Default 60V 2KW off-road buggy

Hi, I've been watching a few of the threads in here to do with batteries but am still struggling with what to buy: the buggy weighs around 70kg without driver/batteries and I was originally going to add 5 x 22Ah AGM batteries at 6 6kg each. I'm now concerned that with all that weight (I'm 80kg, the nephew that I actually built it for is only 25kg, so max weight with me and no batteries would be circa 150kgs), it wont have the power or torque to climb hills (running 5.3:1 ratio). I'm an aircraft engineer but have little experience of working with battery systems and none whatsoever of LiPo batteries! Any advice on whether to go deep cycle AGM/gel/SLA/LiPo much appreciated, already spent a lot on this project so can't really spend more than around 300 on batteries... James
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Old 01-06-2020, 03:32 PM
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the 22ah AGM are probably your best choice if wanting to stay cheap. Best would be the lipo, hoverboard refurb batteries or leaf cells. Or if you can find them cheap enough cordless powertool batteries.

What motor and controller combo are you running? Edit: Read it in the title.
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Old 01-06-2020, 04:53 PM
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I'd pop over on various versions of ebay and see if anyone has electric vehicle battery for sale or look for wrecked electric motorcycle batteries like Zero. The Zero on a bike can get from about 105km to over 350km. Granted this is city vs highway, but I'm sure you can find a wrecked electric motorcycle for cheap.
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Old 01-06-2020, 08:55 PM
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If you are using the little 2k Chinese brushless motor you can get a 10T sprocket for it vs the 13T that comes on them for a little more torque.
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Old 01-07-2020, 08:41 AM
Jim UK Jim UK is offline
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Thanks guys, no electric motorbikes in the UK at all, broken or otherwise! Think I'll have to stick with AGM, was just worried about the current draw when using little 22ah batteries...
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Old 01-07-2020, 10:34 AM
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with 22Ah batteries make sure to buy a high quality cell,
and get the datasheet for it to see what currents can safely be drawn.
(and at what cost.. usually a higher current draw will reduce the useable capacity)

without any documentation the rule of thumb would be to stay above one hour to depletion.
(ie. for a 22Ah cell, to draw less than 22Amps continuosly)
to stay on the safe side and get a decent mileage.

scorn used mighty max batteries
I'll attach their diagrams below
and as you can see they're still reasonably safe at 60A of current drawn (dropping to less than 9Ah of useable capcitance though)
such info will help finding the right battery.

AGM are great, but for powering motors I'd go with classic wet cells or SLAs instead.
the glass mat is not working in your favour here.

'sid
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71aI2x8s0fL._SL1500_.jpg   716SNzI7gYL._SL1500_.jpg  

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Old 01-08-2020, 03:12 AM
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Thanks Sid, can't get MM batteries in the UK though. Sounds like I'd be better going for 30Ah batteries and accepting the weight penalty. Any idea why most of the mobility scooter batteries seem to be AGM?

---------- Post added at 04:12 AM ---------- Previous post was at 04:04 AM ----------

Perhaps something like this?https://www.halfords.com/webapp/wcs/...&storeId=10001
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Old 01-08-2020, 09:25 AM
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I just added the info as an example for what kind of info you ought to be looking for

Mobility scooters have a low power motor usually
most are 250Watts some 750Wats versions for obese riders,
but I never saw any higher powered mobscooters..

So current draw isn't exactly a main issue they need to deal with.
reliably is.. aaaand more importantly for commercial products:
AGM cells are generally considered to be safer than wet cells.
in case they tip over they do not spill as easily.

Also they're cheaper than gel cells (as safe or safer)
and so they're the "perfect compromise" for cheap batteries on commercial products
mobility scooters, kids toys, cheap kick scooters etc.etc.

Since everything listed above is designed for "cruising speeds"..
so the actually expected currentdraw is even less
to keep a mob scooter at walking paces on level road for example
you will need no more than maybe 90 Watts.
Only when you need to go uphill, are on uneven terrain or start to get moving a more significant power is needed,
So yeah they don't care too much about current draw at all

Now back to your batteries..
a wet cell is mostly lighter than an AGM (the glass mat weighs a few grams )
I doubt you can gain a noteworthy weight benefit from that though.

With motorcycle batteries I know that some 9Ah batteries share the exact dimensions (and weight +/- a few grams) with some 12Ah batteries
So maybe try and increase the Ah for your search in single Amphour steps
maybe you're lucky.

taking of which:
I never had a problem with a Yuasa battery (had them on motorcycles for ages [wet cells].. a storage fault on my behalf rendered the last one defunct..has been replaced with a noname AGM battery since it was in store.. not a big fan.. self discharged in 2month to nonstarting condition)
to be sure.. not an AGM fault.. a no-name company crap quality fault.
So if yuasa is on your list..
I buy them without hesitation for motorcycles (if they're any good for electric powered vehicles IDK.. I'd give them a shot though)
Still, check to find a charge/discharge diagram for the specific cell and size.
just to be sure

And if you want to go fancy
you can still hunt on ebay for used but full capacitance Leaf or Ampera Cells
which usually still pack a significant punch at a good size (and usually price).

'sid
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Old 01-08-2020, 01:10 PM
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Thanks Sid, very comprehensive! Always used gel odyssey batteries on my bikes as I have a friend in the industry so get them free, problem is that he can only get me up to 12Ah. They are excellent batteries though! I'll go for 36Ah Yuassa I think, can get 20% off RRP on those and they have a 5 year warranty, just a shame about the 9.3kg x 5 weight penalty. Will also keep an eye out for Leaf cells, though none around at the moment for less than 500, and I'm a little worried about charging them.
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Old 01-10-2020, 01:09 AM
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Why not run the 12ah in parallel and series? Start with 24aH and move up to 36aH if needed.
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Old 01-11-2020, 05:41 AM
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I'd considered it, but 2 x 12Ah weigh 30% more than 1 x 24Ah. Doing everything I can to keep weight down...
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Old 01-11-2020, 10:29 AM
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How much of a pain would it be to have something shipped from the states to the UK? I can find EV battery modules on the US ebay all day long. Other than HAZMAT, weight, could it get through Customs without many issues? https://www.ebay.com/sch/i.html?_nkw...ttery&_sacat=0
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Old 01-20-2020, 12:53 PM
Jim UK Jim UK is offline
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Wow they're cheap there! Even though I work in DC lot tax and shipping are very expensive, plus I wouldn't know how to be safe wiring them up and using/charging them.
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Old 01-20-2020, 08:16 PM
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I'm sure someone on here could help find a wiring diagram for that and how to get a charger setup for it to be safe.
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