Multiple battery float charger

[GarageGuy89]

I have too many toys with too many batteries. If I had to guess I'd say 12 batteries ranging from car to motorcycle to lawn mowers.

Is there a float charger that I can plug into multiple batteries at once? Or is it okay to wire them all up in parallel and connect to the charger?

Right now I pull out the batteries in the winter and just swap which one gets charged everytime I walk into the shop.

 

[3pedal]

I know you can get a battery tender that can handle 4 batteries at a time, my buddy has one. I have one of their 2 battery units, seems to work well.

 

[Bcom]

Yep the Battery Tender has a model that connects to multiple batteries.

 

[MarlynOC]

Guest Chargers, I used one on boat to keep 3 batteries on charge at dock. They make larger ones as well.

 

[kelving884]

I don't know why you couldn't use a good charger to float multiple batteries. Assume the batteries were all the same type, (i.e. 12V lead/acid) their float voltage would be the same regardless of size. Once batteries reach float voltage, the current draw would be minimal.

So, unless I'm missing something, you should be able to float a bunch of batteries with one charger. Do the winter toys in the summer and the summer toys in the winter.

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[johninct]

BatteryMINDER

 

[jrj3rd]

I don't know why you couldn't use a good charger to float multiple batteries. Assume the batteries were all the same type, (i.e. 12V lead/acid) their float voltage would be the same regardless of size. Once batteries reach float voltage, the current draw would be minimal.

So, unless I'm missing something, you should be able to float a bunch of batteries with one charger. Do the winter toys in the summer and the summer toys in the winter.

Sent from my SM-P900 using Tapatalk

No, if you just hook them in parallel the charger will key in on a single level and you will damage the other batteries. This is why they make multiple bank chargers...each battery must be dealt with separately. Battery Tender makes units that will handle 10, and there may be others that would take more.

 

[kelving884]

No, if you just hook them in parallel the charger will key in on a single level and you will damage the other batteries. This is why they make multiple bank chargers...each battery must be dealt with separately. Battery Tender makes units that will handle 10, and there may be others that would take more.

Could you explain why? I'm the first to admit I'm not a battery expert.

But the way, I understand it, lead acid batteries float voltage should be 2.25 to 2.3 volts per cell. Which is 13.5 to 13.8 volts for a 12 volt battery, (6 cells in a 12v battery). A simple battery charger will try to output 13.X volts. If a battery is discharged it will **** amps until it get to 13.X volts. The closer it gets to 13.X volts the less amps it draws.

Now I can see a problem if you have a bad battery, (ie electrically shorted internally). A battery charger than can only output 20 amps may not blow it up. Whereas 10 battery's in parallel that can output 100 amps total may blow it up.

So, what am I missing? $600 for a 10 bank battery tender seems like marketing gimmicks to me.




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[tvtaurus]

The real question here is how much money are you willing to throw at this project?
In order to use a single unit battery tender with multiple outputs, you would either have to remove all of the batteries, or somehow park the vehicles close enough that cords would reach.

Me personally I just use separate harbor freight chargers. I use this on on my bike because of the quick disconnect.

http://www.harborfreight.com/12-volt-deluxe-battery-maintainer-and-float-charger-62813.html

And I use these on everything else. Just make sure that if you unplug them, unhook them from the wall or they will back feed and drain the battery.

http://www.harborfreight.com/automatic-battery-float-charger-42292.html

 

[tvtaurus]

Could you explain why? I'm the first to admit I'm not a battery expert.

But the way, I understand it, lead acid batteries float voltage should be 2.25 to 2.3 volts per cell. Which is 13.5 to 13.8 volts for a 12 volt battery, (6 cells in a 12v battery). A simple battery charger will try to output 13.X volts. If a battery is discharged it will **** amps until it get to 13.X volts. The closer it gets to 13.X volts the less amps it draws.

Now I can see a problem if you have a bad battery, (ie electrically shorted internally). A battery charger than can only output 20 amps may not blow it up. Whereas 10 battery's in parallel that can output 100 amps total may blow it up.

So, what am I missing? $600 for a 10 bank battery tender seems like marketing gimmicks to me.




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Some info on this:
http://www.batterytender.com/connecting-chargers#series-parallel-battery-packs

 

[GarageGuy89]

$600 for a 10 bank battery tender seems like marketing gimmicks to me.

RIGHT! We're all in the wrong business. I laughed out loud when I saw that price.

To answer your question on why/how. I physically pull all the batteries and put them on my bench during the winter. I have one of those centech chargers that I swap intermittently between all of them when I go in the shop every now and then to keep them all topped off.

Been doing it this way the last 6 years and haven't had to replace a battery yet in all my machines.

To answer another question: I'm willing to spend lets say $30, def. not $600. It's more of a convenience thing than anything.

 

[GarageGuy89]

Now I can see a problem if you have a bad battery, (ie electrically shorted internally). A battery charger than can only output 20 amps may not blow it up. Whereas 10 battery's in parallel that can output 100 amps total may blow it up.

So could this be solved by putting in-line fuses to prevent batteries shorting? I have a feeling the $600 version is not much more than this.

We may be on to something here!

 

[scooternut]

After getting sticker shock from the multi battery tenders, I found several links to buy the Battery Tender Junior dirt cheap on ebay if you buy them like six at a time. Crazy what Battery Tender asks for those things, I guess due to the deep pockets of the dealers who just buy them anyways,

 

[tvtaurus]

RIGHT! We're all in the wrong business. I laughed out loud when I saw that price.

To answer your question on why/how. I physically pull all the batteries and put them on my bench during the winter. I have one of those centech chargers that I swap intermittently between all of them when I go in the shop every now and then to keep them all topped off.

Been doing it this way the last 6 years and haven't had to replace a battery yet in all my machines.

To answer another question: I'm willing to spend lets say $30, def. not $600. It's more of a convenience thing than anything.

So with that budget in mind, I would just look into paralleling all of the batteries and just charge them as a bank with one charger/maintainer. Read the link I posted from the battery tender site.

 

[redmondjp]

So with that budget in mind, I would just look into paralleling all of the batteries and just charge them as a bank with one charger/maintainer. Read the link I posted from the battery tender site.

This will work just fine, so long as the charger you are using switches to a float voltage of a little under 14VDC.

 

[stephen.curle]

I just link them in parallel and they charge ok. That's how a dual battery car and battery forklifts work