Charging 85 Ah Battery with 4A or 2A Constant Current Charger: Calculating Duration (Hours)

I have an 85 Ah battery. A 4A or 2A constant current charger. How long should I charge a weak battery? If the current 10 times lower than the capacity should be taken into account, it follows that 8.5A for 10 hours, i.e. 4A for about 21.25 hours? Please correct me if I am writing something wrong

There is nothing to improve ... correct reasoning, if the charging current is lower, the time should be extended, but not exaggerated.

If we are talking about the appropriate rectifier, the charging criterion is the stabilization of the voltage at the battery terminals (connected to the charger). Much depends on the properties of the battery, but it is worth taking the peak voltage of 14.5 V. In fact, it should not exceed 14.2 V. In practice, often 13.8 V is enough. Stabilizing the voltage means no increase for about 2 hours. During this time, the charging current should not exceed 1 A (in fact, about 0.5 A), but this is the theory because we do not know what charger you have and what is the condition of the battery.

About charging the battery, one could write a book about the electrochemical processes taking place there. The charging voltage should be within reasonable limits and the current given by the manufacturer is 1/10 of the capacity for 12 hours while maintaining these parameters. And it is known that an acid battery has its own properties and charging it with too little current is also not entirely healthy for it, but certainly less than overcharging and boiling it. Good-class rectifiers keep this current, some even have a temperature measurement or after changes in internal resistance (and swings of the current consumed!) They know when it is overheated, give it a rest, and then charge it with a holding current. Remember that the more charged the internal resistance increases and it limits the current to a certain extent, which is used by primitive rectifiers on the transformer and bridge.
http://www.akumulator.pl/forum/viewforum.php?f=2
http://www.akumulator.pl/akumulator/budowa-i-dzialanie-akumulatorow.html
http://vwforum.pl/porady/akumulatory/akumulatory.html
You can find a lot of information on the Internet, this is just a quick example.

SławeK

I have a 50Ah center, which has a standby voltage of 12V, so maybe it would be worth adding a little more ...
how long and with what current to do it ??

At 12V, it is very discharged. Check the electrolyte level, it won't hurt to measure its density with a hydrometer and top up with water or electrolyte. And as the manufacturer writes, connect a charger with a range of 5A for 12 hours with battery control (check the battery temperature every few minutes, which should not exceed 55 degrees and there are no cooking symptoms) or without control on a lower current. After charging, measure the density of the electrolyte again. It is worth reading the manual from the battery and some information from the Internet, and as I showed, there is a lot of it.

SławeK

12V lead-acid battery voltage is not a tragedy yet, only below this value (ie 2 - 1.8V / cell) the battery is considered discharged. We never replenish the battery with electrolyte, always with distilled water, because it is water that is lost due to evaporation, as well as electrolysis - the release of gases from the decomposition of water. Lead batteries are charged with a current of not more than 1/10 of the battery capacity (the so-called 10-hour current), too low current will never hurt, too high current may cause the electrolyte to boil over, with the deformation of the plates and the falling of the active mass from them. When charging, the voltage must not exceed 14.4V (I was taught at school that 14.7V) for lead-acid batteries, 14.9V for lead-calcium batteries. The best indicator of the battery charge is the measurement of the electrolyte density with an aerometer, the value for a properly charged battery is 1.28. And also to my colleague SlaweK - the internal resistance of the battery drops while charging.

Most of them agree, but ... please read the advice from the CENTRA manufacturer, probably a reliable source. The charging current may slightly exceed 1/10 of the capacity, the voltage should not exceed 14.6V with a closed battery, but also 16.8V with an open battery http://www.akumulator.pl/akumulator/porady/ladowanie-akumulatora-bezobslugowego.html
http://www.akumulator.pl/akumulator/porady/tak-aby-nie-przeladowac.html

I agree with refilling the electrolyte, but that's why I recommended measuring it, in principle, you should only refill with distilled water, but there are known cases of boiled batteries where sometimes you need to add electrolyte because water alone will not do anything, but this is the attention of those in a tragic state.

And as for the increase in internal resistance during charging, it is this phenomenon that primitive rectifiers without regulation and stabilization of the charging current use. After connecting such a primitive rectifier, you can observe an automatic drop in current during charging.

With the rest, more than one book has been written about charging and servicing batteries, and there are different schools of how to do it correctly. And attention to the quality, which, supposedly with the progress of more and more perfect technologies, increases and the durability of batteries in practice decreases. A similar battery bought for 4-7 years is 4-7 years old and many bought in Poland fall after 2-3 years, but there is probably something in it.



SławeK

Buddy SlaweK, I have a request not to follow the recommendations contained in the links provided by you, because these are the best methods to destroy the battery, the charging voltage of 16.8V will cause the electrolyte to boil quickly, its accelerated decomposition (gassing), as well as thermal damage to the battery, already with an increase in voltage to approx. 15V, a significant increase in temperature and increased gassing can be observed, the battery charging voltage must never exceed 14.4V. Same with the formula for the charging current 5I20. The given example of charging a 60ah lead-acid battery with 15A current will cause it to "boil", these are not Ni-Cd or NI-MH batteries, which can be quickly charged while controlling the cell's temperature. In addition, I persist in the stubbornness of a maniac that the resistance of the battery decreases during charging, it is related to the phenomenon of electrolysis and the decomposition of the electrolyte into ions. http://www.akumulator.pl/akumulator/porady/tak-aby-nie-przeladowac.html
The above link asked how the voltage will increase after disconnecting the battery while the engine is running, the answer probably best proves the "professionalism" and knowledge of the corresponding issue; it is commonly known that is not allowed disconnect the battery in a running vehicle, because the voltage generated by the alternator can increase to several dozen volts, which may damage the car's electronics. Greetings.

robokop wrote:

Colleague SlaweK, I have a request not to follow the recommendations contained in the links provided by you. In addition, I persist in the stubbornness of a maniac that the resistance of the battery decreases during charging, it is related to the phenomenon of electrolysis and decomposition of the electrolyte into ions. that is not allowed disconnect the battery in a running vehicle, because the voltage generated by the alternator can increase to several dozen volts, which may damage the car's electronics. Greetings.

I confirm the above statements as well. And disconnecting the battery. I personally tested while the engine was running. It was also at night on the route. When I put the gas on, all the currently lit bulbs ceased to exist - a massacre!

Hello. I am not an electronics technician and these professional terms, counting records tell me little (not insulting previous speakers) but I know one thing about charging the battery (from an electronics friend), namely the lower the intensity, the better it will charge - more accurately. This takes time, known as low current = slow charging = longer charging. I have an old CCCP rectifier with a potentiometer and I always charge with the lowest possible current within 0.5A, it takes about (non-stop) 2-3 days but I am sure (of course I check the state of charge with a tester) that it is 100% charged . greetings

Yes, the voltage increase to such a limit is acceptable, but if you observe such phenomena and it will certainly happen, you need to lower the voltage, which will limit the current or simply limit the current. And as for disconnecting the battery while the engine is running, agree, of course it is unhealthy. Theoretically, the voltage regulator should maintain the voltage, but this is just a theory and without the battery load, it will increase and most often cause damage. I had such a case in an old Fiat, the battery died completely and the cables were gone, the old type of mechanical regulator, I started the car to quickly replace the battery with a charged nap. It shocked me quite well when I touched the terminals without the battery to such an extent that I could not tear myself away. What the tension must have been, it must have been considerable.
Many a weaker rectifier without load gives almost 20V and this drops under battery load.


As for the internal resistence, it depends on your look, you look at it as a source, and I look at it as a receiver in the charging circuit, and because it is also a source, it gets interesting. And my colleagues see that one could write a book on this subject without exhausting the topic. I'm trying to coat it over here.

Browse the net, I found one more interesting theoretical material http://www.zkue.ime.pw.edu.pl/~jarek/Diagnostyka/INSTALAC/Instalacja.pdf

And interesting experiments with us
https://www.elektroda.pl/rtvforum/topic396537-0.html

SławeK