Charging 24 volt battery setup

[Getting_started]

I'm about to re-do the wiring for my 80 lb thrust trolling motor and was wondering about a couple of things.

1. Its a 24 volt motor and I have 2 12 volt batteries wired in series. I charge the batteries using a 110 volt charger at home in the driveway. Question - Does it make any difference if I leave the batteries in series and charge them both at once, or disconnect them and charge them individually?

2. There will be a trolling motor recepticle connected to the battery. Does it matter if I leave the receptical connected to the batteries while they are being charged? The trolling motor is unplugged while charging.

Ideally, I'd like to make it as simple as possible. Leave the trolling motor recepticle connected to the batteries and charge both batteries at once.

 

[glenn property of pam]

Re: Charging 24 volt battery setup

1/ unless you gave a 24v volt charger you can not charge them in series or both at the same time. keep it simple just charge one at a time with a 12v charger.
2/ neither the battery or the charger cares what is attached to the battery while charging as long as it is turned off while charging.

unless you have a switch that is designed for charging next to you trolling motor plug just keep it simple and charge one battery at a time.

 

[Jlawsen]

Re: Charging 24 volt battery setup

1/ unless you gave a 24v volt charger you can not charge them in series or both at the same time. keep it simple just charge one at a time with a 12v charger.
2/ neither the battery or the charger cares what is attached to the battery while charging as long as it is turned off while charging.

unless you have a switch that is designed for charging next to you trolling motor plug just keep it simple and charge one battery at a time.

Of course you can, I do it all the time. The charger is in parallel, the batteries are in series, they charge just fine without disconnecting anything.

 

[glenn property of pam]

Re: Charging 24 volt battery setup

Of course you can, I do it all the time. The charger is in parallel, the batteries are in series, they charge just fine without disconnecting anything.

re-read the op post mate as he wants to charge both batteries at the same time while they are in series. i never said to disconnect anything i said to either use a 24v charger to charge both at the same time or a 12v charger to charge one at a time.

"Question - Does it make any difference if I leave the batteries in series and charge them both at once"

 

[Jlawsen]

Re: Charging 24 volt battery setup

Yes I did read that and yes they will still charge just fine. Connect the charger to the first battery to charge both at once or get two chargers and put the second one on the second battery and charge them twice as fast.

Seriously, I always thought it was the way you think it is until I got my first onboard charger and was freaked out about my 24v system. I called Guest and they straightened me out and remined me that it was a series/parallel circuit when the charger is attached. The second battery will equalize with the first as it's being charged. The first battery is 12v and so is the second, it's the sum of the total series ckt that makes it 24v.

 

[fishrdan]

Re: Charging 24 volt battery setup

re-read the op post mate as he wants to charge both batteries at the same time while they are in series.

JL is right, the 24V bank can be charged with independent 12V sources,,, if the charger is capable. I have 2 boats, both with 24V series connected battery banks and both of them get the 24V bank charged without breaking the series connection. One of the boats has a MK330 3 bank onboard charger with independant outputs, the other boat I use 2 separate Schumacher portable battery chargers, 1 connected to each battery simultaneously. Works fine.

Now, if a mutli-bank charger does no have independent outputs, you could be in for some problems, fireworks, lots of smoke...

 

[Jlawsen]

Re: Charging 24 volt battery setup

Now, if a mutli-bank charger does no have independent outputs, you could be in for some problems, fireworks, lots of smoke...

LOL so you had one of those old battery tenders too! (notice I said had)

 

[fishrdan]

Re: Charging 24 volt battery setup

YI called Guest and they straightened me out an remined me that it was a series/parallel circuit when the charger is attached.

Series/parallel? That would have all the terminals of the batteries connected to a common point, lots of fireworks and smoke. I think they told you wrong, even though it will work since their charger (most likely) has independent outputs, the outputs don't see each other so there is no parallel connection made through the charger.

 

[fishrdan]

Re: Charging 24 volt battery setup

Ideally, I'd like to make it as simple as possible. Leave the trolling motor recepticle connected to the batteries and charge both batteries at once.

Simple? The simplest solution would be installing a multi-bank charger with independent outputs (most chargers have independent outputs now, but verify it). Leave everything connected as-is, add the charger outputs, charge away!

Another option would be to use a Marinco 12/24 socket and plugs. Series jumpered plug for the 24V trolling motor, parallel jumpered plug for the 12V charger. I wouldn't do this unless you needed to replace the plug anyway as the socket/plugs are kind of expensive, probably as expensive as a 2 bank charger....

 

[fishrdan]

Re: Charging 24 volt battery setup

LOL so you had one of those old battery tenders too!

Nope, but I did let the smoke out of lots of electronic components in tech school or set-up people to let the smoke out of their electronic components :facepalm:

 

[Jlawsen]

Re: Charging 24 volt battery setup

Nope, but I did let the smoke out of lots of electronic components in tech school or set-up people to let the smoke out of their electronic components :facepalm:

Me too, had a lot of fun with that.. I just got in from off site where I found 110vac on a phone system. My probe went nuts from about 5 feet away. Found out the dogs had been digging in the yard and had dug up a direct burial that was chewed bare and laying against the ground rod for the phones. You would think it would have blown the breaker but the earth was dry and the ground rod was for the phones only so it didn't. Had it rained, or somebody watered there would have been smoke.

P.S. The dog's are already goofy so no change in them..

 

[glenn property of pam]

Re: Charging 24 volt battery setup

Yes I did read that and yes they will still charge just fine. Connect the charger to the first battery to charge both at once or get two chargers and put the second one on the second battery and charge them twice as fast.

Seriously, I always thought it was the way you think it is until I got my first onboard charger and was freaked out about my 24v system. I called Guest and they straightened me out and remined me that it was a series/parallel circuit when the charger is attached. The second battery will equalize with the first as it's being charged. The first battery is 12v and so is the second, it's the sum of the total series ckt that makes it 24v.

im confussed as this is what i said in the beginning to charge one at a time using a 12v charger. im trying to keep this simple for the op as he seems to have a battery charger not a 2 bank unit with auto connect or anything like that, its proberly a basic good old fashion car battery charger with croc clips. so using a car charger you charge one at a time, if you have 2 car chargers you can use both at the same time on diffrent batteries.......correct?

 

[fishrdan]

Re: Charging 24 volt battery setup

so using a car charger you charge one at a time, if you have 2 car chargers you can use both at the same time on diffrent batteries.......correct?

Yup

 

[bruceb58]

Re: Charging 24 volt battery setup

if you have 2 car chargers you can use both at the same time on diffrent batteries.......correct?

Maybe...depends on if the output of the charger is floating from its ground connection.

The OP should use a 2 bank charger and just charge both at the same time.

 

[Silvertip]

Re: Charging 24 volt battery setup

You simply cannot have a series/parallel 24 volt system. You have a series system to provide 24 volts. You have a 12 volt system with two batteries in parallel. Now lets discuss what it is the OP really wants to accomplish or know! We cannot do that until he tells us what type of charger he has.

1) Yes -- he said he has a 12 volt charger. That is not definitive enough.
2) Does this charger have one set of outputs, two sets of outputs, three sets of outputs, --- what?
3) If this charger is a single bank, it can ONLY output 12 volts and therefore there is no option of charging both at the same time. Each battery must be charged separately. Attempting to charge both will indeed not work.
4) If the charger has two or more outputs, you simply connect each pair to a separate battery.
5) As Bruce indicated, be very careful about using two separate (as in two totally separate chargers) to charge a 24 volt series setup. Keep in mind that the POS and NEG on charger #1 will be connected to POS and NEG on BAT #1. Now follow this -- is not the NEG on BAT #2 also connected by the series jumper to the POS on BAT #1?????? Of course it is. Therefore when you connect a separate charger to BAT #2 the NEG lead is connected electrically to the POS of BAT #1 as well as the NEG of BAT #2. If there is NOT total isolation electrically between those two charger negative leads, you just made an arc welder.
6) From what we know and can gather, the OP has a single bank charger. No options -- charge each battery separately

 

[Outsider]

Re: Charging 24 volt battery setup

Popcorn, anyone? Jeez, this ain't rocket science:

1) Forget about the receptacle, it's of no consequence unless you plan to charge through it.

2) You can charge both batteries together if you have a 24v charger, or ...

3) You can charge both batteries together from a single 12v charger if the charger has multiple output leads.

4) You cannot charge both batteries at the same time from a single output 12v charger unless you do some creative wiring.

Who's got the beer ...

 

[sschefer]

Re: Charging 24 volt battery setup

4) You cannot charge both batteries at the same time from a single output 12v charger unless you do some creative wiring.

Actually, if the charger is connected to the first battery it will be in parallel with the first battery which will charge it. The second battery will charge also because it is connected in series with the first battery. If you were to connect the second battery to a second charger in parallel then you would simply double your charging current and charge both batteries faster. This is how a dual battery charger works. If you would like, you can download the manual for one of the popular marine multiple battery chargers and it will show you how they are hooked up.

One way to understand this is if you were to take two 1.5v batteries and put them in a flash light. 1 of the batteries is fully charged and the second is dead. The flash light will still work because the full battery will use it's energy to charge the dead battery. The flashlight will only stay lit half as long as two fully charged batteries and when you take the batteries out both will be dead. The proof of that is that the bulb is connected to the - of the first battery and the positve of the second. If you were take the batteries out at some point in between you would find that the dead battery was no longer dead but in fact did have a charge. This is you clue to quit paying a bunch of money for rechargeable batteries and just buy the charger. Regular batteries are rechargeable too but wont cycle as many times as a battery rated for recharging.

Think of it like this.. Let's call the charger a battery for a moment because in a sense, it is. Now suppose I instead of thinking I'm hooking up chargers I'm thinking I'm hooking up 4 batteries. I take the first two batteries and put them in parallel and the second two batteries and put them in parallel. Then I put a battery cable from the +12 of the first battery set and put it on the -12 of the second set. Now if I take a cable and put it on the + of the second battery set and put a cable on the - of the second set and then measure the voltage I across those two I will have 24 vdc. If I take one battery away from each set (disconnect the chargers) then I still have 24vdc at the output cables of the second battery. So you see, it does work and it works just fine.

 

[glenn property of pam]

Re: Charging 24 volt battery setup

dual bank chargers have a isolation transformer for each bank which in effect means they have no relationship to each other. +12v is a relative term used to discribe the potential between the possitive and negative of a battery. as a example if you put a meter from the pos post of the starting battery of the boat and the negative of your truck there is no relationship between the 2 so you will not read any voltage even thought you know that both batterys have a 12v charge. it was easier in school when we were shown a dc voltage being used on the same wire that ac voltage was being carried on. the charging you are on about between 2 batterys in series is sympathy charging and you are correct in that a dead battery will show a charge but if you was to try to use a battery that was charged in this manner you will find that the charge is nothing more than a capacity effect on the battery plates and a load test will show the battery as flat.

 

[dwparker99]

Re: Charging 24 volt battery setup

There is a ton of bad info given to the OP in this thread. When a charger is hooked to one battery in a series setup, it will NEVER charge the other battery. When put under a load, two 12v batteries connected in series will not equalize. Each battery much provide equal current to maintain the 24v. If you hook a fully charged 12v battery in series with a discharged 12v battery and hook to a 24v load, you will not charge the discharged battery. In fact you will further damage the discharged battery by what is called "reversed charging." Think about it. Why are we told to never let a battery discharge below a certain level. A 12v batteries has six 2v cells hooked in series. Each cell must be able to provide energy to maintain 12v. If you discharge to the point that one cell drops out, you will be driving current through it in the opposite direction than you would when charging. This is bad for the cell and will eventually permanently damage the battery. Google "reverse charging a battery" and this will make more sense.

 

[Silvertip]

Re: Charging 24 volt battery setup

Actually, if the charger is connected to the first battery it will be in parallel with the first battery which will charge it.

Ahhhhh -- NO!

Here is a 24 volt series setup with a 12 volt circuit off the battery on the left. Just pretend those two wires are from a single output 12 volt charger charger. Please show us who know nothing about this how the battery on the right gets charged.