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SLA battery charge indicator

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fjpompeo

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Is it possible to build a 6V@4A sealed lead acid battery charge indicator using LM3914 with 10 LEDs?

Regards,

Fernando
 

wizpic

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yes it possible but it would only be a rough giude

if you search on google you should find what your after, I would do it with a PIC16F876 with 10 LEDS but it can easily be done wiht lm3914

there is no 100% way of telling how much charge there is left in a battery.

letas say if your battery was 4AH and your load was 200ma then it would take 20hrs to discharge it but if you was to say that you discharged it at

battery cap discharge current time
4 / 200ma 20hrs True ? yes

but's let say if the continuous dischaege was 500ma you wouyld then say that it should last 8 Hours TRUE or FALSE

answer is FALSE because you have got something called the Peukert's effect and my calculations would say that the battery would only last 6hhrs 2hrs shorter

T=C(C/R)N-1/IN works like this c =capacity R is rating 20/5hrs n is the exponent and I is dishcharge current like this below

4*(4/20)^(1.3-1)/0.2^1.3 = 20hrs

but say if the discharge rate was higher then it would look like this

4*(4/20)^(1.3-1)/0.5^1.3 = 6.07hrs and not the expected 8hrs if you worked it 4 devided by .5 = 8hrs

Hope I've not bored you to much but hopefully it wil give you a rough guide when chosing a battery :))

wizpic
 

nguyennam

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