Reply With QuoteNot all batteries are created equal,charge it and see ,a healthy 12 v battery charged should be about 13 v.
Despite asking the internet I can’t seem to get a definitive answer so asking the TZ collective seems like a good idea.
If you drain a brand new 12v battery so it’s got about 10v’s left, assuming it’s rechargeable (in this case a motorbike battery) will it be OK or have I ruined in for use in said Motorbike which requires at least 11.5v to be any use?
Some of the internet says it will not be any use ever again, some say it should be fine. Not sure if this is a Motorbike thing particularly as I’ve definitely had dead car batteries before and they’ve been OK.
I guess bike batteries are a lot smaller but still need a decent amount of charge to crank the engine.
Thanks in advance.
Not all batteries are created equal,charge it and see ,a healthy 12 v battery charged should be about 13 v.
An AGM battery should recharge from 10v okay.
But - if you are worried long term - charge it fully stick it on the bike, and try a load of starts.
Once happy that it is fine - take it back off, charge fully and store it in the utility room for the winter. If you have a proper battery 'tender' - leave in the bike and attach the battery tender.
Thanks both.
I would just charge it and see what happens, I think it will be fine
I’m not a battery expert but from experience with both cars and bikes, 9 out of 10 times having come back to a dead battery, they have always come back to good life with a charge and or use.
Depends on your battery charger/ tender. Some of the modern ones charge up then run a series of discharge then charge cycle to give your battery an electronic “ workout”
Find someone with a Cetek, Optimate, etc. charger.
The higher price ones run a rejuvenate cycle that will reclaim a dead battery (probably).
I have rescued several 12v batteries using mine. It wasn't cheap (£80ish) but does the job if at all possible. Not guaranteed but definitely worth a go.
If you pass Manchester you are welcome to stick it on mine. It takes a couple of days to run the full cycle.
you can try a home charger and if that fails i take it to a garage that has a big expensive charger that costs hundreds and if that fails get a new battery
Thanks, I have just purchased an Optimate from Amazon and will give it a go. I was always going to get one to see me through the winter anyway.Originally Posted by unclealec
I’ll leave getting a new battery until I know if it’s necessary. I guess it will probably be OK initially and I may just have (hopefully) shortened its overall life a bit.
Let us know how you get on.
Overdischarging a lead acid battery can cause loss of capacity and can reduce the cranking current that it can supply.
Two things can happen inside the cell.
- Sulphation
Sulphur can get gummed onto the negative electrode. As the battery discharges it's normal for sulphur in the electrolyte (liquid) to combine with the lead in the the negative electrode (plate) to form lead sulphite. But when left over discharged the process goes too far and doesn't easily get reversed when the battery is charged. The sulphate hardens and won't come off.
The effect is a battery that doesn't charge easily. Lead sulhate is an electrical insulator. Capacity is reduced as the amount of sulphur available to move between sulphuric acid in the electrolyte and lead suplhate in the negative electrode is reduced. Because the plates are gummed up they have less active surface area, which reduces the amount of current the battery can supply.
The battery will still charge to 13.8V, but you'll notice that the battery doesn't turn the engine as quickly when fully charged (it can't supply enough current). It will quickly go from fully charged to flat.
This process is reversible, but with a boggo standard charger it can take 30 to 40 charge / discharge cycles. Smart chargers like the Optimate use an alternating current to charge-discharge-charge-discharge the battery, allowing them to recover the battery in a single session.
- Loss of lead
Sadly lead can literally drop off the electrodes when a cell is overdischarged. It happens when overcharged or charged too quickly too. Hydrogen gas forms on the electrode and displaces the lead.
The lead collects at the bottom of the battery in sectioned trays, the trays are designed to stop the lead in the bottom from building up and forming a short circuit between the electrodes.
If this happens the cell will read 0V and your fully charged 12V battery which contains 6 cells, will drop in voltage by 2V for each shorted cell.
Assuming things never get that bad, loss of lead from the electrodes will lead to a reduced ability to provide current. At first it probably won't give a loss of capacity as there's generally more lead than sulphur available.
Again you'll notice that the battery doesn't turn the engine as quickly when fully charged (it can't supply enough current). But it doesn't go from fully charged to flat as quickly as a sulphated battery.
Sadly there's no way to get the lead sludge from the bottom of the battery back onto the plates, so this process is not reversible.
Other things the battery can suffer from is evaporation of water in the electrolyte & loss of water through gassing (hydrogen at one terminal, oxygen at the other). These lead to a loss of capacity and ability to supply current, as there's less electrolyte (capacity) and the electrodes aren't fully immersed (less area in the electrolyte= less current).
What's actually happened to your battery will depend on how quickly it was discharges, how long it was left discharged for, how low the voltages went, what the temperature was, the internal construction and how the manufacturer may have tweaked the chemistry.
TLDR:
There's no way of telling if the battery is knackered, or recoverable. It may be recoverable enough to be usable, but could suffer loss of capacity and lower ability to supply the 100's of amps needed to turn a starter motor.
Putting it on a smart charger like the Optimate is absolutely the best chance you've got of restoring it to health.
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