circuit wanted for battery %charge monitor

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I have built the oately solar battery charger that disconnects battery
when it reaches preset charged voltage and it works well but I want to
find a circuit that monitors a shunt on the battery and tells me what
% has discharged or charged.  I would prefer to build it than buy a
commercial expensive controller.

I have a 12v 220ah gel (2 x 6v M83CHP06V27 batts and 300Wpanel) and
dont want to discharge more than 50% in one day.

Any ideas appreciated.

Re: circuit wanted for battery %charge monitor



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I use the low volt cutout cct set for 11volts. You could set the cutoff to
correspond to the battery volts at 50% discharged, it would be approximate
due to temperature variations but close enough for your purpose and cheaper
than using a pic or whatever to log usage.

Cheers .......... Rheilly P




Re: circuit wanted for battery %charge monitor


Battery monitors are best a guess unless you spend a *bucket* of money.
Even then they are not that flash as the battery ages.  Personally I would
recommend you save your money.
While you are using the battery and the sun don't shine at night, voltage is
an excellent guide when you have a light load on the system.
We seldom get our systems below 12.4V at night and usually 12.5V and never
below 12.2V.

I have extensive experience in small solar systems and never fitted battery
monitors.  If you need more capacity buy an extra solar panel or put in an
extra battery - NOT in parallel.  Split the system.
Hopefully you have a decent quality solar regualtor as that makes a *big*
difference to how close to 100% the batteries get charged.  You can easily
have up to 12% from full battery capacity with cheap solar regulators.

If you want to carry this convo on at a higher level leave your e-mail
address.
Dave.


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Re: circuit wanted for battery %charge monitor



Thanks for the pointers, I will monitor the voltage and not let it get
below 12v or so. (The inverter auto cuts out at 10.5v)

I just need to set the charge voltage with that oately charger
circuit,
My batteries are 2 of these in series
http://www.staabbattery.com/product/UB200-6E-Y.html
http://www.staabbattery.com/mm5/graphics/00000001/pdf/UB200-6E.pdf

The pdf data says
charge voltage  7.25 - 7.45v
float voltage  6.8v - 6.9v

Since there is no float feature on the basic oately charger kit I was
just going to adjust the pot to charge up to 14.9v

One reason I wanted two 6v batts in series is because I wanted a 6v
tap to directly feed my adsl modem which is always running.  plugpack
is 5v at 2 amps but modem is drawing about 1 amp max. Running modem
directly without an inverter
would be most efficient. (5w x 24 hours) .
To load balance and kind of drain both 6v batts equally I will connect
my ipcamera
to the other 6v batt and try to run cam on dc as cam draws about 800ma


Appreciate any other snippets of info. My email is lentildude AT
hotmail.com

thanks

George

Re: circuit wanted for battery %charge monitor


If you are f....'ing around with an Oatley charger kit on modern batteries,
you are *NUTS* putting it nicely.  You cannot mess around with rubbish solar
regulators on modern batteries and especially sealed batteries.  14.9v would
kill your batteries quickly.  You need a precision temperature controlled
PWM solar regulator for AGM VRLA batteries.  On solar you need to spend the
money once, do the job once and damn well do it properly otherwise it will
cost you an ongoing fortune.  Solar done correctly is magic and you use and
forget it. Send you an email.


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Re: circuit wanted for battery %charge monitor



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You'd better make sure the grounds of the modem and ip camera don't meet at some
point...

Tom

Re: circuit wanted for battery %charge monitor


Thanks Dave, will email you in detail but severe budget retraints
means compromising and DIY system.

I guess the compromise would be to set charge voltage cutout at 14.2v
just above recommended float voltage.

Tom, yes I was thinking an earth loop would be disasterous.  The
ipcams ethernet cable plugs into the hub on adsl modem so dont think I
can run them seperately off their own 6v batts safely. May have to
build 12v to 5v inverters but of course wasting power in the
conversion.

George


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Re: circuit wanted for battery %charge monitor


There are PWM voltage reducing units on the market.  These are generally
better than 85% efficiency and about $25.00.  Jaycar have one and cannot
remember the part number and DSE www.dse.com.au has M9889.  Much better
option than taking power off the 6V battery even though you are attempting
to keep it balanced.


Thanks Dave, will email you in detail but severe budget retraints
means compromising and DIY system.

I guess the compromise would be to set charge voltage cutout at 14.2v
just above recommended float voltage.

Tom, yes I was thinking an earth loop would be disasterous.  The
ipcams ethernet cable plugs into the hub on adsl modem so dont think I
can run them seperately off their own 6v batts safely. May have to
build 12v to 5v inverters but of course wasting power in the
conversion.

George



Re: circuit wanted for battery %charge monitor



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Ethernet is dc isolated and usually ok, watch out for some other tricky
connections.
Tom

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