Charging in series

Am I correct, when charging in series, to put the positive charger on the last positive terminal (where the cable exits to the starter, engine, etc.) and the negative charger on the negative terminal/cable that runs to the frame?

I have two six volts in series and charged them this way, but it killed the charger and the batteries. I am confused.

Thanks
JimS

that sounds correct to me.

thats correct unless you have a positive ground tractor...you have to go by the marks on battery OR the positive post is always bigger diameter than negative post.

You did connect the two 6 volt batteries, positive and negative cables first. That leaves you the neg of one batt to ground, and the pos to hook to your starter. In effect a 12 volt batt.

You were on 12 volt setting for the charger, correct?

Paul

A battery with internal shorts can ruin a charger, even if it is in series with a good battery. also if there is a drain on the battery the resistance across the battery terminals can also overload the charger. First disconnect the batteries. then check the specific gravity of each cell (if possible) to assure they are similar. 1.260 is good to go and charged. less is OK if discharged but uniform. Charge them with the terminal going to the starter terminal disconnected. Good luck. Jim

Unless the batteries are identical and are known to be at the same state of charge, it's better to charge them one at a time at six volts. Otherwise one battery will be undercharged and the other battery overcharged. You can also safely charge them in parallel.

Of course, once you install them in a vehicle with a 12 volt system, obviously they'll be in series. But once the batteries are both fully charged, it isn't such a problem. Also, vehicle charging systems are regulated, while most battery chargers are not.

MarkB
If your statement is correct & I'll quote you[/quote]how does an alternator charge the batteries on the machine that has a 12 V system utilizing two 6 V batteries? I've charged two 6V or two 12V batteries several times with a 12 V battery charger with no problems.

Jim, you have exactly the same problem with balancing the batteries in a 12 volt vehicle. But the closer the batteries are to being in balance to start with, the less of a problem it is. Which is why should always replace the batteries in pairs. Charging the new batteries individually (or better yet, in parallel) helps to ensure they are in balance.

As I mentioned in my first post, most battery chargers have no real voltage regulation. Consequently a battery in an unbalanced pair can be over-charged much more by a charger than by a vehicle's charging system.

If you want to prove this, just run a six volt accessory off one of your vehicle's batteries. It won't take very long before that battery is discharged and the other battery is overcharged.

MarkB
I fully agree with what you stated on a 24 V system where 1/2 the lights/access are operated on each 12 V battery. Now you name one piece of farm machinery that runs a 6 V operated device on a system with two 6 V batteries as you describe. Can you explain the difference in charging two 6 V batteries(no dead cells) with a good battery cable & connections VS charging a 12 V battery. I'll bet the two 6 V batteries will charge correctly if all the cells are good it's the same as charging a 12 V battery. PLUS some newer higher quality battery chargers have charge regulator built into them

Yes

Thanks for your help.

Yes, that is correct.

Thanks

Understood, but I could see the ground cable connecting to the body/frame, so I thought it was safe to assume that was the ground.

I'm feeling more and more that either the battery failed and destroyed the charger or the charger failed destroying the battery.

By the way, there is absolutely zero charge on either battery, even 48 hours after being disconnected. I'm not sure if I mentioned that there was an extrememly heavy odor of battery acid after the unit being on trickle charge over night.

Thanks

jim

Well sir at the end of the charging cycle measure the voltage across each battery. They will be different unless they are identical. Most of the time the difference is small enough that it doesn't really matter. A lot of charging periods are interrupted when one of the batteries only has like an 85% fill and the other maybe a 89% fill. The voltage will differ by a few tenths of a volt but no big deal. My automatic charger gives a full charge green light with 4 amperes of charge current remaining. It's a Schumacher like you'd buy at TSC. Obviously if you are 4 amperes from a full charge where the current drops to zero, you are going to have different levels on the batteries.

Oh and the "full" charge is an arbitrary number which depends on several variables including temperature, sulfate in the battery, charger controls to name a few. Around here my Full charge number is 12.75v year round. Easy to remember and works for me.

MarkB, I know this is obvious but if you charge them in parallel, you need to use a 6v charger and they are hard to find these days.

On the charger failing, if your batteries were fully discharged and your charger was not the new electronic controlled charge rate variable, you could have put too many amps through it and yes burned up a wire internally.

Mark

Jim, I didn't mean to imply that it is common to run six volt accessories off a 12 volt system. Obviously that's not the case, since there are very few accessories which will run off six volts. Unlike the situation with 12 volt accessories on a 24 volt system, where this problem commonly occurs.

You are correct that if you have two identical, good batteries, there is no problem charging them in series. But getting back to the original post, the other Jim was trying to understand why he damaged his batteries and charger and how to avoid it in the future.

(quoted from post at 05:52:32 05/20/13)m, I But getting back to the original post, the other Jim was trying to understand why he damaged his batteries and charger and how to avoid it in the future.

Click to expand...

Incorrect operation of a battery charger no matter if charging one 12 V or two 6 V batteries connected together will ruin charger and/or the batteries.