Lead acid vs NiCd batteries for emrgency lighting?

[treez]

Can Lead acids be charge with constant C/10 current sources?
Which of the two chemictrys has the lowest self discharge
Which can be charged back up from 0V without being damaged.
Which is more likely to need individual cell voltage monitoring.

 

[rahdirs]

• C/7 or C/10 is considered the safe-charging current of Lead-acid battery.The higher the current,higher monitoring is required.
• The Lead Acid's retention is best among rechargeable batteries. Whereas the NiCd self-discharges approximately 40 percent of its stored energy in three months, the SLA self-discharges the same amount in one year.
• Some Sealed Lead Acid batteries retain nearly their full charge for two months or more just sitting on the shelf, unattached to a charger. NiCd batteries lose about 1% of their charge per day when sitting on the shelf, due to internal "self-discharge".
• The NiCd is a known to be a battery type that performs well under rigorous working conditions,so i think it should perform better than Lead Acid when charging starts from 0V.

 

[tpetar]

Can Lead acids be charge with constant C/10 current sources?
Which of the two chemictrys has the lowest self discharge
Which can be charged back up from 0V without being damaged.
Which is more likely to need individual cell voltage monitoring.

No lead acid should not be charged with constant current, this type of battery require voltage and current control during charging process, you can check your earlier threads.

Voltage during the charging process increases and current should decrese.

We discuss earlier in one of your thread about 0V discharge, both batteries are damaged at 0V, lead acid for sure, and NiCd have big chance to be destroyed also.

In my country market shops must return lead acid to factory for recharging after 6 months if they dont sell battery. For that time battery voltage falldown to some level when sulphatization process of lead plates can occur.

Lead acid should always be at full level to avoid sulphatization. After discharging look to recharge in next 24h.

You cant monitor individual cell in battery such as starter car battery or many other deep cycle such as for ups. These batteries are maded from cells pack 3-6 in serie, and these cells are internally connected. There is other lead acid batteries in bigger single cells such as tractional cells, but this is not for light sytems what you have.





Best regards,
Peter

:wink: