Multi-pack battery voltage monitor
in [Design]
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From: Gary Lynch on 21 Jul 2010 07:15 +------+ I am looking for an economical way to measure | _|_ terminal voltages of individual SLA batteries --- | ? | in a stack up to 72 packs high. Atmel & Linear = |___| Technology make products that ALMOST do | | this--allow direct connect to battery +------+ terminals to steal power, serial output with | level shifting so they can be cascaded, +------+ etc--but tout them only for Li-Ion technology. | _|_ It appears they cannot straddle a potential --- | ? | greater than 5 V. = |___| | | I read another post that claimed for a low-end +------+ appliances such as mine, it was cheaper to : replace the batteries every 3 years than to : watch for 'slackers.' +------+ | _|_ Any other ideas? --- | ? | = |___| Thanks. | | +------+ ============================================================ Gary Lynch To send mail, change no$pam gary.lynch(a)no$pam.com in my domain name to ieee. ============================================================
From: PeterD on 21 Jul 2010 07:33 On Wed, 21 Jul 2010 07:15:53 -0400, Gary Lynch <bookworm(a)execpc.com> wrote: > +------+ I am looking for an economical way to measure > | _|_ terminal voltages of individual SLA batteries >--- | ? | in a stack up to 72 packs high. Atmel & Linear > = |___| Technology make products that ALMOST do > | | this--allow direct connect to battery > +------+ terminals to steal power, serial output with > | level shifting so they can be cascaded, > +------+ etc--but tout them only for Li-Ion technology. > | _|_ It appears they cannot straddle a potential >--- | ? | greater than 5 V. > = |___| > | | I read another post that claimed for a low-end > +------+ appliances such as mine, it was cheaper to > : replace the batteries every 3 years than to > : watch for 'slackers.' > +------+ > | _|_ Any other ideas? >--- | ? | > = |___| Thanks. > | | > +------+ >============================================================ >Gary Lynch To send mail, change no$pam >gary.lynch(a)no$pam.com in my domain name to ieee. >============================================================ I guess when you say 'pack' you are referring to a multi-cell battery (12 Volts?) Why not just off-set the Atmel device by 7 to 10 volts or so? 3
From: John Devereux on 21 Jul 2010 08:34 Gary Lynch <bookworm(a)execpc.com> writes: > +------+ I am looking for an economical way to measure > | _|_ terminal voltages of individual SLA batteries > --- | ? | in a stack up to 72 packs high. Atmel & Linear > = |___| Technology make products that ALMOST do > | | this--allow direct connect to battery > +------+ terminals to steal power, serial output with > | level shifting so they can be cascaded, > +------+ etc--but tout them only for Li-Ion technology. > | _|_ It appears they cannot straddle a potential > --- | ? | greater than 5 V. > = |___| > | | I read another post that claimed for a low-end > +------+ appliances such as mine, it was cheaper to > : replace the batteries every 3 years than to > : watch for 'slackers.' > +------+ > | _|_ Any other ideas? > --- | ? | > = |___| Thanks. > | | > +------+ > ============================================================ > Gary Lynch To send mail, change no$pam > gary.lynch(a)no$pam.com in my domain name to ieee. > ============================================================ Hi Gary, So is that 72x12V batteries? What sort of accuracy do you need on the measured voltage? -- John Devereux
From: Paul Keinanen on 21 Jul 2010 08:55 On Wed, 21 Jul 2010 07:15:53 -0400, Gary Lynch <bookworm(a)execpc.com> wrote: > +------+ I am looking for an economical way to measure > | _|_ terminal voltages of individual SLA batteries >--- | ? | in a stack up to 72 packs high. Atmel & Linear > = |___| Technology make products that ALMOST do > | | this--allow direct connect to battery > +------+ terminals to steal power, serial output with > | level shifting so they can be cascaded, > +------+ etc--but tout them only for Li-Ion technology. > | _|_ It appears they cannot straddle a potential >--- | ? | greater than 5 V. > = |___| > | | I read another post that claimed for a low-end > +------+ appliances such as mine, it was cheaper to > : replace the batteries every 3 years than to > : watch for 'slackers.' > +------+ > | _|_ Any other ideas? >--- | ? | > = |___| Thanks. > | | > +------+ >============================================================ >Gary Lynch To send mail, change no$pam >gary.lynch(a)no$pam.com in my domain name to ieee. >============================================================ How much can you load those batteries ? How about a voltage divider across each 12 V battery, producing a voltage less than 5 V ? The voltage divider could consist of a 7 V zener (the upper leg) and a resistor (the lower leg), thus the battery voltage swing would go into the IC without attenuation..
From: Jim Thompson on 21 Jul 2010 11:09
On Wed, 21 Jul 2010 07:15:53 -0400, Gary Lynch <bookworm(a)execpc.com> wrote: > +------+ I am looking for an economical way to measure > | _|_ terminal voltages of individual SLA batteries >--- | ? | in a stack up to 72 packs high. Atmel & Linear > = |___| Technology make products that ALMOST do > | | this--allow direct connect to battery > +------+ terminals to steal power, serial output with > | level shifting so they can be cascaded, > +------+ etc--but tout them only for Li-Ion technology. > | _|_ It appears they cannot straddle a potential >--- | ? | greater than 5 V. > = |___| > | | I read another post that claimed for a low-end > +------+ appliances such as mine, it was cheaper to > : replace the batteries every 3 years than to > : watch for 'slackers.' > +------+ > | _|_ Any other ideas? >--- | ? | > = |___| Thanks. > | | > +------+ >============================================================ >Gary Lynch To send mail, change no$pam >gary.lynch(a)no$pam.com in my domain name to ieee. >============================================================ Once upon a time � I designed (for California Micro Devices) a LiIon charge/discharge controller that tested and equalized all the cells (3) in a pak. I think it's used internally in present-day LiIon paks. I have previously posted the back-to-back PMOS current-direction controller that was used. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | |