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Hi Folks

Postby g7pvs » 21 Nov 2012, 12:37

Hi,
I've been researching replacing sealed lead acid batteries on my mobility scooter (somewhat modified Wispa) with LiFePo4 and the only relevant info I could find on the net was this site. I've ordered 8 off 40152S 15Ah batteries with a Battery Monitor and charger with I should just about be able to shoe-horn into the battery compartment of my scooter (to replace the two 12ah 12V batteries)
As I use my the scooter (which is very small) around my house as well as when I go out I've decided more ground clearance and squishy tyres would be good and am thinking of doing a narrower scooter version of BM3.
I can walk very short distances (although with pain), so can manage with the scooter, but because I use it so much improving the ride quality and ground clearance would make a big diffrence.
I have a spare scooter, so that when my main scooter breaks I can repair the broken one whilst using the other one as I wouldn't be able to manage around my house without a working scooter.
The main reason for changing the batteries is weight and cost, being lighter makes other peoples life easier - those who lift my scooter - either fully assembled or broken down into cars/taxis sometimes find the weight excessive (I'm now too ill to drive myself) and I should no longer need to replace the batteries every year as the LiFePo4 batteries should have a much longer life (2000 cycles should only reduce the capacity to 80%).

Best Regards

Trev
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Location: Stafford, UK

Re: Hi Folks

Postby Burgerman » 21 Nov 2012, 14:02

(2000 cycles should only reduce the capacity to 80%).


Only if looked after well. Hopefully you are not using a BMS and a dumb charger?

You should also get about double the range too. Or charge half as often. So 2000 cycles at say 3 charges a week is 12.8 years! If you do not discharge as deeply as that, you may get 5k charges...
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Re: Hi Folks

Postby g7pvs » 21 Nov 2012, 21:19

Hi,

I'm afraid what I've ordered is a BMS and what I believe is a fairly simple charger:

http://eclipsebikes.com/lifepo4-battery ... -1036.html

- should arrive tomorrow along with the batteries and BMS.

I had thought that it would be OK - I'm not bothered how long the batteries take to charge as I currently charge the batteries overnight - up to this point I've only flattened batteries during the day if they are past their best and am on a long day out ( in which case I can take a couple of spare batteries with me).

Is there a reason I shouldn't use the BMS?

Best Regards

Trev
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Posts: 110
Joined: 21 Nov 2012, 11:58
Location: Stafford, UK

Re: Hi Folks

Postby Burgerman » 21 Nov 2012, 21:28

Yes. They "work" in that they allow a dumb charger to charge your cells. But they allow cells to go too high, (very small balance capability) and cannot slow down the charger. So the cells will have a hard life.

And... BMS systems really need to be engineered to suit a specific system. Because they also have amp limits under load (and cut out or fail) as well as try to protect the batteries by guessing when they are discharged. But voltage varies with load and they dont know either the load, or cell type, C rate or capacity...

See how it goes.
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