Simultaneous battery charging

[dozer1013]

I charge my trolling motor batteries at the same time by connecting them in parallel. They are both the same brand/type battery and get used at roughly the same rate (used in serial for 24V)

I also have a cranking battery and deep cycle battery used as a house battery.

My question is can those two batteries, the cranking and the deep cycle, also be charge at the same time if connected in parallel? Both are 12v of course but I wasn't sure since one is a cranking and one a deep cycle.

Thanks

 

[Silvertip]

Re: Simultaneous battery charging

Oh boy -- you opened a can of worms. You will get all sorts of theories but if you think about it, over the road trucks may have a mix of battery brands and sizes in their battery racks and they live just fine. A single output battery charger cannot determine if "either" battery is topped off individually but that doesn't matter. The charger is looking at the "system" voltage so it doesn't matter if there is one battery or 15 in parallel. It will charge until the system level matches whatever values the charger was built to. What does matter is the "battery technology". You wouldn't want to mix flooded lead acid batteries with gel for example. A battery bank with a bad cell in one battery or even a bad battery in the bank would not allow the system to fully charge so an error indication on the charger, or failure to reach full charge condition would result.

 

[Splat]

Re: Simultaneous battery charging

^^^^ this.

 

[dozer1013]

Re: Simultaneous battery charging

Oh boy -- you opened a can of worms. You will get all sorts of theories but if you think about it, over the road trucks may have a mix of battery brands and sizes in their battery racks and they live just fine. A single output battery charger cannot determine if "either" battery is topped off individually but that doesn't matter. The charger is looking at the "system" voltage so it doesn't matter if there is one battery or 15 in parallel. It will charge until the system level matches whatever values the charger was built to. What does matter is the "battery technology". You wouldn't want to mix flooded lead acid batteries with gel for example. A battery bank with a bad cell in one battery or even a bad battery in the bank would not allow the system to fully charge so an error indication on the charger, or failure to reach full charge condition would result.

That was my thinking...as long as they are the same voltage and type (flooded lead acid) and because they are connected in parallel so to make a single system, then it should be ok

 

[UncleWillie]

Re: Simultaneous battery charging

That was my thinking...as long as they are the same voltage and type (flooded lead acid) and because they are connected in parallel so to make a single system, then it should be ok

As long as all the IF's match it will work just fine. This is how the Typical ACR System operates.

What are you charging them with? The Alternator or a Shore Powered charger?
The starting battery likely needs very little charge.
So the bulk of the charge is going to go to the house battery.

 

[dozer1013]

Re: Simultaneous battery charging

As long as all the IF's match it will work just fine. This is how the Typical ACR System operates.

What are you charging them with? The Alternator or a Shore Powered charger?
The starting battery likely needs very little charge.
So the bulk of the charge is going to go to the house battery.

Shore Powered charger, it's a standard charger made by Die Hard

 

[glenn property of pam]

Re: Simultaneous battery charging

will it work...yes
is there down sides especially if one battery has a fault....yes

better idea is to consider a 3 bank on board charger that will treat each battery as individual and it would not require you to do any rewiring which could lead to a mistake. As a added bonus it only takes 30 seconds to plug in then you can forget about the batteries as it will take care of them.

 

[dozer1013]

Re: Simultaneous battery charging

will it work...yes
is there down sides especially if one battery has a fault....yes

better idea is to consider a 3 bank on board charger that will treat each battery as individual and it would not require you to do any rewiring which could lead to a mistake. As a added bonus it only takes 30 seconds to plug in then you can forget about the batteries as it will take care of them.

I like the idea of plug and forget...

Can I assume that I would need a 4 bank charger since the two trolling motor batteries are usually connect in serial for 24v use? I only connect them in parallel when I'm charging them.

 

[fishrdan]

Re: Simultaneous battery charging

So you have:

- 2 batteries in series for the trolling motor
- 1 house battery
- 1 start battery

Correct?

Then yes, a 4 back charger would be best, and easiest. Connect each output to a battery, plug it in and let it run, no monkeying around with swapping wires around or flipping switches.

(Just make sure the charger has independent outputs, a modern 4 bank charger should have independent outputs.)

 

[Catback]

Re: Simultaneous battery charging

Minn Kota has an awesome product out called the on board alternator charger . it wires to you motors charger and charges all you batteries while the motor is running , so no need for charging you house battery or trolling motor batteries from a shore charger while on a weekend trip or a week trip or what ever . this thing is great . I hope i posted the link right .


Minn Kota? On-Board DC Alternator Charger : Cabela's

 

[Silvertip]

Re: Simultaneous battery charging

Minn Kota has an awesome product out called the on board alternator charger . it wires to you motors charger and charges all you batteries while the motor is running , so no need for charging you house battery or trolling motor batteries from a shore charger while on a weekend trip or a week trip or what ever . this thing is great . I hope i posted the link right .


Minn Kota? On-Board DC Alternator Charger : Cabela's

Beware of advertising hype. There is one very important factor in devices that claim to be a solution to charging issues. The factor is CAPACITY or OUTPUT. While there is no doubt "some" charging will occur regardless what motor you have, you cannot get more OUT of devices like this than you put INTO it. In other words an alternator with 20 amp output cannot possibly "fully charge" four batteries, two of which are likely deeply discharged. Running a 24 volt troller at a fairly high speed will easily suck 20 amps from the battery bank. That current must be replaced and if a 20 amp alternator is all you have, that means running wide open for an hour is required. Even with a 60 amp alternator on an I/O that time would still be in the 1/2 hour range and there are still two other batteries to deal with. So run the numbers. Perpetual motion has not been invented yet.

 

[bassman284]

Re: Simultaneous battery charging

Yup, everybody is looking for the Magic Cookie but it doesn't really exist, as far as we know.

 

[metriccrescentwrench]

Re: Simultaneous battery charging

So run the numbers. Perpetual motion has not been invented yet.

Dang, that pesky science and those laws of physics keep getting in the way of good ideas (or maybe I should say good schemes).