Battery probs (1 Viewer)

[Baden87]

Need some help please got 2 85amp batteries connected in parallel and charged via solar panel they charge fine reaching 13.7volts ish but very quickly die down to around 9 volts when used( ie 1 hours telly) this setup has worked fine for the last couple of years, but now dying. i suspect battery failure but how would i check which one it is likely to be, as i was thinking its unlikely to be both?

 

[johnsandywhite]

Need some help please got 2 85amp batteries connected in parallel and charged via solar panel they charge fine reaching 13.7volts ish but very quickly die down to around 9 volts when used( ie 1 hours telly) this setup has worked fine for the last couple of years, but now dying. i suspect battery failure but how would i check which one it is likely to be, as i was thinking its unlikely to be both?

:Cool: If you had the possibilty to equalise the batteries you may be able to resurrect them. I killed my brand new 2 x 105ah batteries in the USA just after I had fitted them 4 years ago, They are still working good enough to run the TV for 4 hours at night, plus the usual RV 12v systems and lights and TV in the mornings. Prior to this year I could boild kettles all day long and night after being charged by our Solar panels and Solar Boost 2000E controller. :thumb:

 

[hilldweller]

i suspect battery failure but how would i check which one it is likely to be, as i was thinking its unlikely to be both?

Just disconnect one at a time.

Note we've just had a couple of threads on where to buy replacement batteries. Do a search on LUCAS.

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[Baden87]

thanks if i disconnect them one at a time what signs would i find with multimeter when both charged ? and could one bad one be dragging the other one down?

 

[pappajohn]

if they drop to 9v within one hour under very light load they are both knackered.
a bad one will pull the other down but not that quick after being on charge.

12v is, technically, a dead battery.

Terminal voltage
The open circuit voltage, is measured when the engine is off and no loads are connected. It can be approximately related to the charge of the battery by:
Open Circuit Voltage (12 V)Open Circuit Voltage (6 V)Approximate chargeRelative acid density
12.65 V6.32 V100%1.265 g/cm3
12.45 V6.22 V75%1.225 g/cm3
12.24 V6.12 V50%1.190 g/cm3
12.06 V6.03 V25%1.155 g/cm3
11.89 V6.00 V0%1.120 g/cm3
Open circuit voltage is also affected by temperature, and the specific gravity of the electrolyte at full charge.

The following is common for a six-cell automotive lead-acid battery at room temperature:

• Quiescent (open-circuit) voltage at full charge: 12.6 V
• Unloading-end: 11.8 V
• Charge with 13.2–14.4 V
• Gassing voltage: 14.4 V
• Continuous-preservation charge with max. 13.2 V
• After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V
• Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.
• All voltages are at 20 °C, and must be adjusted -0.022V/°C for temperature changes.

 

[hilldweller]

thanks if i disconnect them one at a time what signs would i find with multimeter when both charged ? and could one bad one be dragging the other one down?

You wouldn't even need a meter - charge 1 if it holds the charge it's OK.
Charge 2 if it holds up it's OK.

You could make sure all connections are sound.

But more likely you look at the thread on new batteries.

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