question

harold avatar image
harold asked

Midpoint deviation rising

Hello Techs,
I have a 24V system, with 2 closed (mainentance free) Lead Acid battery's of 220Ah, charged by a Quattro, CCGX controlled.
Last years my mid point devition stayed around 0,1 - 0,2 %, currently it is rising to 0,4 - 0,5 %, even when the Quattro is in Storage mode.

Do I need to do something already?

Harold

MultiPlus Quattro Inverter ChargerBMV Battery Monitorlead-acid
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5 Answers
kevgermany avatar image
kevgermany answered ·

Not necessarily, but good to do. See 4) below.


From the datasheet:

Installation
1) The Battery Balancer(s) must be installed on a well-ventilated vertical
surface close to the batteries (but, due to possible corrosive gasses,
not above the batteries!)
2) In case of series-parallel connection, the midpoint
interconnecting cables must be sized to at least carry the current
that arises when one battery becomes open-circuited.
- In case of 2 parallel strings: cross section 50% of the series
interconnecting cables.
- In case of 3 parallel strings: cross section 33% of the series
interconnecting cables, etc.
3) If required: first wire the alarm contact and the alarm reset.
4) Use at least 0,75 mm² to wire the negative, positive and midpoint
connections (in this order). Additionally, if in your application it is
needed to comply with UL, also fuse these wires near the batteries
with a 10A fuse suitable for DC current (e.g. Littelfuse ATOF series
automotive blade fuse in combination with an inline fuse holder).
5) The balancer is operational.
When the voltage over a string of two batteries is less than 26,6V the
balancer switches to standby and all LEDs will be off.
When the voltage over a string of two batteries increases to more than
27,3V (during charging) the green LED will turn on, indicating that the
balancer is on.
When on, a voltage deviation of more than 50 mV will start the
balancing process and at 100 mV one of the two orange LEDs will turn
on. A deviation of more than 200 mV will trigger the alarm relay.


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kevgermany avatar image
kevgermany answered ·

I had something like this. Probably a good idea to install a battery balancer. They're not perfect, but do minimise the out of balance.

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harold avatar image
harold answered ·

Is this also used / useful for flooded lead acid?

2 comments
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kevgermany avatar image kevgermany ♦♦ commented ·
Very much so.
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harold avatar image harold kevgermany ♦♦ commented ·
Thanks!
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harold avatar image
harold answered ·

Installing a Bat Balancer, do I add a fuse in all 3 line's?

(So : + - and Midpoint?)

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nickdb avatar image
nickdb answered ·

My older gel batteries started to drift, it was because they were undercharging. Once PV was upgraded the deviation started to settle and there were no balancers involved.

A similar site did use balancers and had none of these issues.

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