My car is sometimes laid up for long periods. Can anyone advise the best way to trickle charge the battery in situ to prevent the alarm and self-discharge from causing a flat battery?
In days of yore, before all of the electronics junk in the car, I would remove the battery and charge it daily for about an hour using a commercial battery charger. The current draw was about 4 amps. I had it set on an applicance timer. Nowadays, you may kill your electronics if you remove the battery.
I had a good read a week ago in a charger manual. The charge protocol they advise for stored units, is to charge until full,then charge some more at a lower current,and after that to wait until self- discharge drops the voltage to something like
12.2 to 12.4, after which you repeat the cycle. There are some chargers,which do this automatically, and have a temperature sensor at one of the poles,because the whole story about charge/discharge is very temp related. I dont remember the brand, but it is a US one(I think) used a lot in marine environment. Extended trickle charge seems to damage your plates somehow, and can spell disaster(ask my friend,he had to clean his entire boat with soda water to remove the evaporated sulfuric acid,at the end of the winter)
What you need is a charger with a "float charge" setting/switch. This holdes the battery voltage slightly lower than on full charge to stop excessive gassing/boiling. I got one of these chargers from a car parts place for £12 about 10 years ago.
Note read the spec check that the float charge is done at reduced VOLTAGE. Some makers say their charger automatically switches to float charging at the end of a normal charge cycle when what they actually mean is the CURRENT reduces at the end of the charge... which it does anyway on a lead acid battery.
You still need to check the water level every few weeks/months.
Look on the Yuasa web site for applications info on sealed lead acid batteries. I know yours probably isn't sealed, but the information is still probably useful.
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