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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Hi all.
Seems that it is feasible to use 3 12V 7Ah in place of heavy 12V 15Ah on an electric bike.
The problem is that I also have a pile of perfectly good but unmatched LiPos totalling 40Ah at 4V or 20Ah at 7.2V
Would it be feasible to make a voltage converter (probably 34063/MOSFET based) that converts this into charge voltage for the lead acid bank? Was thinking around 2A charge current so when the motor isn't being used the batteries are always charging.
As you probably already know you will also need a protection circuit to stop the lupo's cell voltage getting to low. Maby zvs with a diy transformer would work if you can get it to run at such a low voltage
Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156
Not sure it’s a good idea to put unmatched cells in series because of the cell balancing problem. I ain't a fan of lipos for experiential stuff cos they are so fussy and it’s too easy to kill them, though having said that I realise they would have significant advantages for electric vehicles and the like.
Using a battery to charge a battery, may be only be around about 75% efficient for the lead acid type as you have to charge at a higher voltage than you got out, and generally put more amp hours back in than you took out to balance it up, as some is lost as heat e.c.t
The push pull converter tends to be quite popular at low input voltages, But the question is how much effort and time is this, compared to a new battery pack of the right voltage that you could run the motor off directly, or with a change over switch if you kept the existing battery as a reserve.
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Boost charging SLAs from lithium bank?
