Originally Posted by wrcsixeight
Any 'maintenance' charger is intended to keep a healthy fully charged starting battery fully charged by negating the self discharge f a lead acid battery, and to counteract the parasitic draw of vehicle electronics while the vehicle is parked.
The Ideal float voltage is temperature dependent
This ideal voltage is specific to a given battery, and all batteries vry to some degree as to what is ideal..
Too high a float/maintenance voltage will increase water usage and palte erosion
Too low a F/M voltage will allow the battery to discharge and sulfate.
A maintenance charger is NOt designed to recharge a battery to full.
Some are limited to 0.5 amps, and perhaps 13.8v, but a given battery might require that 0.5 amps just to be held at 13.2, and as such might never rise above that no matter how llng, A healthier battery might be pushed upto 14.2v by 0.5 amps, if there is no voltage limiting.
I think these maintenance chargers are a solution for a non existent problem, in many cases.
many people do nto realize tat the self discharge of a battery is extremely low, in low temperatures, and if the parasitic draw is eliminated by unhooking a battery cable the fully charged stored battery in a northern climate will still he happy and healthy in the spring.
It is very possible the battery will be happier and healthy if it were stored fully charged and then disconnected from paraistic loads by removing the ground cable, compred to if it were plugged into a low amperage maintenance charger, or one with too low a float voltage for low temperatures, or one lacking both temperature compensation and is too low a voltge for the given battery/temperture..
Obviously on some newer vehicles disconnecting the battery is a Non Starter, and such a vehicles battery stored for months on end is not going to be happy and healthy when asked to work again.
There is no Across the board one size fits all solution to keeping the battery in as good of condition as possible with stored undriven vehicle, but there are many ways that are far from ideal.
The fully charged cold battery will not freeze until something like -46F, and it will discharge very little in that time at those temperatures.
if I could run a power cord to a vehicle stored in the winter , I'd prefer a powersuppy set to a voltage such as 14.1, be on a timer for 15 to 30 minutes a day, as opposed to a mainteance charger trying to hold it at 13.1 to 13.4 24/7. all winter long..
On a side note, An Equalizaton charge is an intentional overcharge, designed to get the specific gravity of all the cells back up to their maximum, and highly respected Deep cycle battery makers Rolls Surrette and trojan recommend a EQ voltage of 16.2v, on a 77f battery. This EQ charge is intended to be closely monitored by a human with a temperature compensated hydrometer, and ended once the Specific gravity of the electrolyte maxes out at the expected maximum, or simply stops rising, otr te battery gets too hot(north of 110F), or if the amperage required to maintain voltage starts rising.
The EQcharge itself is absusive to the battery, but can and does desulfate the battery to some degree. trojan says to perform an EQ charge when the cells vary by more than 0.015 on the hydrometer. I'd not really recommend people perform EQ charges unless they can control voltage manually, an dmonitor the electorlyte density and battery temperature. An eQ charge performed on a battery that does not need one is simply causing the shedding of positive plate material, and staryng batteries have thin plates to start with.
If a flooded battery sits, the denser electrolye will sink and the sulfuric acid will be stronger on the bottom of the battery. Any gassing voltage, which is temperature dependent will DESTRATIFY the electrolyte, but EQ voltages are NOt required to perform destratification., and it only requires about 10 to 15 minutes to DEstratify the electorlyte at gassing voltages.
While the Concrete floor/battery myth is still continued long after asphalt battery casings were phased out, a cpmcrete floor can cause the battery electrolyte to stratify faster, allowing the bottom of the battery's plates to get chewed up faster.
No single voltage maintenance charger is Ideal for each and every battery in each and every temperature.. The ideal maintenance charger would have temperature compensation and the ability to float at user programmable voltages, if th battery were 77F, and adjust accordingly.
The Maintenance free flooded battery, regular starting battery, and AGm battery all have slightly different fully charged resting voltages, different manufacturer recommended float voltages and wil lrequire different amounts of amperage to achieve and be held at those ideal voltages.
So the One size fits all marketing, is more like One size fits ONE specific battery, in a narrow band of battery temperature.
Beware of product marketing, and those with absolute trust in their purchase.
A battery will accept as much or little amperage at the voltage at the battery terminals, upto the maximum output of the chrging source, and no two batteries are exactly the same.
LED power supplies with a voltage range of 10.5 to 15vDC capable ofupto 30 amps, are about 20 to 30$ . Their voltage adjustment potentiometers are only rated fo r 25 to 50 cycles though. Fire one of these up 15 to 20 minutes a day via a timer at a gassing voltage will insure the battery is both fully charged, and destratified, and healthy battery is stilly healthy and fully charged, when the key is turned to start.
Do note many of these cheaper adjustable voltage power suplies have no current limiting. If set to a high voltage and hooked to a depleted battery, the depleted battery might suck up more than 30 amps and it will not take long for the magic smoke contained witin, to be released.
But if closely monitored and the voltage potentiometer adjusted from low, upwards as thre battery charges, can be used as a 30 amp charger. Use a good ammeter and voltmeter. voltagealone is almost meaningless, but seeing how many amps the battery is accepting at the voltage is extremely enlightening
There are several Adjustable power supplies with constant current limiting on overload( charging a healthy depleted battery is an overload), but they should have their ventilation increased if asked regularly to reach their maximum output by charging a well depleted battery. They are of course manual chargers, and need to be removed once the specific gravity is maxed out, or have their voltage lowered to an acceptable 'float' level for that specific lead acid battery, Which Might be 13.1 for a 65F maintenance free battery made by east penn, or 13.5v for a 68f capped starting battery by Johnson controls, or 14.07V for a 45F degree Odyssey agm.
One float voltage fits all is like saying one oil fits each and every engine in each and every climate so don't worry about it
My vehicles tend to lose some charge by the nature of Subaru's (and likely many others') charging algorithms.
I have a garage = very easy to hook-up (literally takes 30 seconds)
I have a DC power supply, though I would worry too much about it being on a timer. If this maintainer works well enough, I'll move my PSU charging to every few weeks instead of weekly to bi-weekly.
Having something like this seems way cheaper for every-other-day hook-up overnight.
I'm a nerd = I'll spend a night monitoring a new product that I've never used, which has some bad reviews.
I'm an enginerd = I don't mind monitoring this charger at least once every time I use it, to ensure it's not draining the battery when it should be filling up the losses from Subaru's stupid battery algorithm and maintaining it.
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