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Deep Cycle - Damaged Plates ?

PostPosted: Wed Sep 26, 2018 10:49 am
by manga
Details:

I have a Century N70T 100Ah flooded deep cycle battery being charged through a charging controller via 2x 60W solar panels.

I went overseas for an extended period and asked a friend to top-up the water levels every month.
Said friend forgot to top-up at some stage and mentioned when he did remember to top-up with water, almost 2L of water was used (normally every month only requires ~150ml).

Upon my return I see the plates have buckled somewhat and there is some minimal bulging at the ends of the battery.

~~~~~~~

Charging the battery now has the following symptoms:

- Never reaches full charge
- Gets warm to the touch after a few hours charging (never did this before) @ 2.5A, very warm @ 5A
- Seems to have lost capacity
- Battery is 12.4V after charging, 11.6V after standing overnight (about 14 hours) without charging

~~~~~~~~

Questions I have are:

1) Can I rejuvenate the battery some how ?
2) Would it still be safe to charge, or do I risk it exploding one day due to it getting hot ?

Re: Deep Cycle - Damaged Plates ?

PostPosted: Wed Sep 26, 2018 12:16 pm
by Gordon-Loomberah
What happens to the voltage if you apply say a 10A load?

If it quickly drops below 11V, then one cell is probably stuffed (and others may be on the way out too).

Dropping to 11.6V after resting overnight following a charge indicates you have a very sick battery, probably on its last legs.

You could try chagrging and discharging at low rates a few times to see if things improve, but I suspect it is unlikely that the battery will be of much use now. The plates must have been exposed for quite a while for the battery to require 2l of water to refill. How long was it between top-ups to the 2l fill?
Was there much load on the battery while you were away?

Re: Deep Cycle - Damaged Plates ?

PostPosted: Wed Sep 26, 2018 4:22 pm
by manga
What happens to the voltage if you apply say a 10A load?

Battery resting voltage 11.6V.
Connect 2x 50W halogens (~ 8.2A load) for 1 minute.
Voltage drops to 10.2V
After disconnect, voltage rises to 11.4V after 30 seconds.


How long was it between top-ups to the 2L fill?

Probably 2 or 3 months


Was there much load on the battery while you were away?

Just some garden LED lights, about 1A for most of the night, using up approx. 15Ah per day.
Then a recharge during the day and repeat again.

Re: Deep Cycle - Damaged Plates ?

PostPosted: Wed Sep 26, 2018 4:35 pm
by Gordon-Loomberah
OK, one cell is basically dead. If you want a decent amount of storage at 12V, you'll need a new battery.

The battery should not go through 2l of electrolyte in 2 or 3 months, unless it was being overcharged.

Re: Deep Cycle - Damaged Plates ?

PostPosted: Wed Sep 26, 2018 7:38 pm
by Privatteer
It may not be the fault of the friend as such.
A cell failure may have occurred in the battery during this period. With the solar charger unable to get it to full voltage it will keep supplying current to the battery. The constant charging causes the electrolyte to evaporate faster as excessive voltage is applied to the non failed cells.
The bulging sides etc are all symptoms of a failed cell.

While it would pay to monitor the replacement battery to ensure the charger is working and dropping back to float properly I suspect the battery will be at fault.