# Batteries

• posted
Is there anyone that have some experience on charging 2 lead batteries (12V)
in series ?
I do not mean the circuit, but if the batteries will be correctly charged or
will they have some long time problem ?
Enzo
• posted
Never answer a question with another question, but where do you think that your 12 V batteries come from, and why, indeed, are they called batteries instead of just cells?
Your 12 V batteries are made up of 6 2V cells in series.
Why should there then be a problem with 12 such cells in series rather than with only 6?
(Not intended to be a scornful reply, sorry, can't be bothered to recompose it)
• posted
If the two batteries are brand new (exactly same characteristics in both charge & discharge performance so that when you charged them with 27VDC charging voltage, each battery gets exactly half 13.5VDC and same discharge curves are followed so that say when you shutoff at 22VDC, then exactly 11.0 VDC is on each battery, then both batteries will last nearly as long as a single battery charged at 13.5VDC and discharged to 11VDC before shutdown.
This "balanced" or "equalized" battery charge/discharge is the key to long battery life. With 2 batteries, it is not that hard to achieve this balance, but with 4 batteries (48VDC battery bank), it is more difficult and by the time you have 10 or more batteries in series, it becomes nearly impossible to keep all 10 batteries charging & discharging the same way. That's why most UPS systems with higher than 48VDC battery voltage must use a "battery equalizer" circuit - otherwise, very short battery lifetimes will be the end result.
• posted
Why bother posting a response if you cannot also bother to make it useful? The above answer is so vague as to be misleading.
Two *similar* batteries can be charged in series. They must be at approximately the same charge level. That basically means you can operate a string of similar cells as a battery if both the charge and discharge are the same for all cells.
Dissimilar batteries can be charged in parallel.
• posted
Telephone companies use 48 VDC battery strings, and typically expect to get 20-25 years of service from them.
The difference is that they monitor the charge on each individual cell, and take corrective action if any one cell gets out of sync with the rest of the string. That type of adjustment is rarely done, but every 3-4 years is the difference between a battery string that lasts 4-5 years and one that makes it 20-30 years.
• posted
I asume that you are doing this because you have a 24 volt charger which is what you wuld need to do this with.
The lectrical system on my boat is amde up of two 6 volt batteries in series to make a 12 volt bank and charge them with a 12 volt charging sustem and they work fine that way.
• posted
To "Airy": Yet another useless response from you.
To the op: You have to be very careful when charging batteries in series. Basically you must ensure they are as identical as possible, by identical I mean both the model of the battery and it's "condition", if you try to charge two batteries of the same model, one on it's last leg and one brand new you will not get the result you want.
Frankly, unless you are sure they are the same batteries and in the same condition I recommend either charging them seperatly (best) or charging them in parallel (not as good but still far better then in series).
TTYL
• posted
It is very possible to insert a new cell into an old string. The fact that one is old and one is new does not prevent them from being used in series. They don't actually even have to be same model, though they do have to be _essentially_ identical models. Over time it is possible to adjust the specific gravity to allow an old cell and a new cell to work together in series.
Not that the above is a "good" idea, just that it can be done. It usually is not worth the effort required. However... if the cells are large and expensive, it is!
There is *no* difference between charging two cells separately and charging them in parallel.
• posted
I would charge the two batteries in parallel using a special isolation diode with a very small voltage drop. This is how it is normally done in motor homes and other similiar applications.......good luck....Ross
• posted
On Tue, 30 Dec 2003 16:25:50 GMT, "Ross Mac" Gave us:
No diode is needed.
In parallel, they both see the same charging voltage. One just has to be sure to check the battery voltages and remove the battery(s) from the charger as they become fully charged.
The reason that split charging systems are used on applications like that which you describe is because the charging apparatus (alternator) cannot handle charging both together.
• posted
True that the diode is not necesary if you want to handle it manually. That is why I said "I would" instead of "You Have to". I mentioned the split charge diode because it would be simpler and prevent backflow from battery to battery. It will also allow you to run one battery down without affecting the starting battery. Not alot of information given here. We don't know the charger voltage, amperage or the application. I just thought I would toss that out there in the case it would be helpful....Ross
• posted
As usual, DimBulb hasn't a clue. The diodes (a.k.a. battery isolator) are needed if the batteries have different uses (I.e. a starting battery and a utility battery in an RV). Connecting a discharged Lead-Acid battery to a charged one isn't something that one wants to do. The diodes allow the alternator to charge the batteries regardless of state. Shottkeys work nicely here.
• posted
message
No surprise here....Dimbulb does his google search and posts from there...and yes...there are some pretty slick diode modules with almost not drop out there to do the job....Ross
• posted
On Tue, 30 Dec 2003 21:07:11 -0500, Keith R. Williams Gave us:
It ALSO has to do with the alternator's total available, reliable output.
JUST like I said. NO diode is needed in a standard charging situation of two like batteries, and that includes their charge state. JUST like Floyd said as well.
Fuck you, Keith Retard Williams. You are a twit that follows people around like a little cockroach, which is all you are.
• posted
On Wed, 31 Dec 2003 05:28:52 GMT, "Ross Mac" Gave us:
No. I do not, dipshit.
And in the situation in question, they are not required... at all.
• posted
Read the post....it never said the diodes were "required".. And was repeated in a follow up post....
• posted
Once again, read the posts....it never states the diode is required.....
• posted
Why bother posting a response if you cannot also bother to make it useful? The below answer is so vague as to be misleading.
Dissimilar batteries of 12V and 24V can be charged in parallel?
Bwahahahahahahahahahahahahahaha!
• posted
Two dissimilar 12V batteries, which is what was being discussed, can be charged in parallel.
• posted
Sorry, OM. but your post did not mention two 12V batteries. It only mentioned dissimilar batteries.
Why bother posting a response if you cannot also bother to make it useful? The answer you gave was so vague as to be misleading.
You didn't respond to the original question, but only sought to score points by attacking those who did. Shame on you.
Unfortunately your childishness showed up all too well.
I didn't need to make a fool of you, you did it so well by yourself.

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