2 12v or 1 24v Battery Tender?

[fireman5214]

Hello all,

I talked with a Battery Tender representative and they said a 24v battery tender would be used on a 2-battery system but I don't think they understood what I meant about the startup of the M1028 being 24v and the rest of the vehicle running on 12v. My dad is thinking two 12v battery tenders (one for each battery) would be best.

(I did search and see other threads on battery tenders on SS but they were not for M1028's so I was not sure if it would work the same or not, that is the purpose of this post)

So with that being said, what would be best?
2) 12-volt battery tenders
1) 24-volt battery tender

 

[CBrinker]

I don’t personally use battery tenders on my cucvs because they get used often, but my cousin has a m1028 and a m1009 and he uses 2 12v tenders on each and my grandfather uses 2 12v tenders on his m1009

 

[sue]

I would respectfully recommend one 24V

 

[NDT]

I use two 12 volt tenders, they are more readily available and I can rotate them to other machines.

 

[MarcusOReallyus]

I would respectfully recommend one 24V

Please share your reasons.

 

[155mm]

I suggest this one. I have bought and used 4 of these, very happy.

NOCO Genius G7200 12V/24V 7.2 Amp Battery Charger and Maintainer https://www.amazon.com/dp/B004LWTHP2/ref=cm_sw_r_cp_tai_ccZhEbA31QXTR

 

[fireman5214]

I don’t personally use battery tenders on my cucvs because they get used often, but my cousin has a m1028 and a m1009 and he uses 2 12v tenders on each and my grandfather uses 2 12v tenders on his m1009

Well these are fire apparatus both for brush fires and winter emergencies so they are not used daily. Once a week if you are lucky at times. Depends on the type of call and how many we have a year. Thank-you for your input on the other CUCVs, I was not sure if they were all the same setup or not with dual systems.

 

[fireman5214]

I would respectfully recommend one 24V

can you elaborate more on why? There is a huge price difference between 24v and 12v and we are a non-profit working on a budget.

 

[tennmogger]

Managing each battery separately should be best, using two 12 volt units. Batteries are never exactly the same. Each battery needs handled according to its state of charge and physican condition, age, etc. If maintained in series (24v unit) each battery will not get what it needs. This is especially true in vehicles that have both 12v and 24v loads.

A simple test: use a 12v charger on each 12v set of batteries in a 24v system. Note the time to reach full charge. The sets/pairs will require different times to charge.

 

[Curtisje]

I recommend 2 12 volt tenders. The rear battery maintains a higher state of charge since it is only used during startup. I recently did some cleaning up under my hood. I pulled the batteries and put them each on a trickle charger. It took about an hour to charge up the rear battery to 12.6v. It took 4 hours to charge the front battery to 12.6v.

This would be a problem for a 24v charger (or so I'm told) as it wouldn't charge the batteries equally. Ine would get overcharged and the other undercharged.

 

[Daybreak]

Howdy,
Because you stated it was fire equipment... You might have different personel rolling. You will want the KISS system

Keep the batteries charged via the 24v slave receptacle. Easier to unplug and roll.

24v charging through slave port

 

[sue]

A lot “wife’s tells” and rumors and I had a friend
who had a friend story’s out there. When you
Tie two 12v batts together they effectively
become one 24v. Yes you can get 2 12v tenders
But then you have to disconnect them.
After about the 3rd time you will wish you had
a 24v tender. If it’s about cost I understand,
when I was younger my family had to cut cost
and in turn we had to let one of the upstairs
Nanny’s go.

 

[fireman5214]

Howdy,
Because you stated it was fire equipment... You might have different personal rolling. You will want the KISS system

Keep the batteries charged via the 24v slave receptacle. Easier to unplug and roll.

24v charging through slave port

This is a good option but I have no idea if that is even hooked up yet. This truck was out for 2 years to get painted (long story, they did it on their own time) and came from the forestry service. I would have to check and see if it is still hooked up.

 

[Curtisje]

Reference

Connecting Batteries & Chargers In Series & Parallel

www.batterytender.com

7. Two Batteries in Series, Two Chargers

Two 12 Volt batteries connected in series. The resulting battery pack voltage is 24 volts. Each battery is connected to a single 12-volt charger. This is probably the best way to ensure that each battery is completely recharged to its full capacity after each time that the battery pack is discharged. This eliminates most of the problems associated with cycling batteries connected in series strings.

Good luck. Either way I think you will be fine.

 

[Jbulach]

can you elaborate more on why? There is a huge price difference between 24v and 12v and we are a non-profit working on a budget.

Sounds as if you already know your answer but I’ll bite. I’m with sue, and Daybreak.

$70 for the noco genius g7200, does 12 and 24, float thru your slave, yank it out and throw it on the floor when the truck has to go out, use it on 12v to balance the batteries individually every once and a great while, will also charge a dead battery fairly quick.

$60 for two 12v battery tenders, fiddle with disconnecting when a call comes in, not good for much other than floating.

$80 for two 12v battery minders, still fiddle with disconnecting when a call comes in, floats, and desulfates.

Not really a “huge price difference” after all, and if you looking at cheap $5 float chargers just send me $10 for saving you a headache, and forget the idea all together.

I use my minders a lot in the winter when the batteries are pulled from the farm equipment, and do believe the desulfation helps extend the battery life. Also use the heck out of my Noco for a little bit of everything. But in your application floating 24v thru the slave port is a no brainer.

 

[98G]

I recommend 2 12 volt tenders. The rear battery maintains a higher state of charge since it is only used during startup. I recently did some cleaning up under my hood. I pulled the batteries and put them each on a trickle charger. It took about an hour to charge up the rear battery to 12.6v. It took 4 hours to charge the front battery to 12.6v.

This would be a problem for a 24v charger (or so I'm told) as it wouldn't charge the batteries equally. Ine would get overcharged and the other undercharged.

I agree with this. On a hmmwv or a deuce or a 5ton I'd say just go with a 24v through the slave port.

But on the cucv's bastardized 12/24 system I'd charge each separately.

Not a huge difference either way.

 

[chevymike]

I would have to agree, 2 12v chargers. As mentioned, a 24v charger hooked to 2 12v batteries (versus a native 24v battery) will not properly charge both batteries. Chargers are looking at voltage to determine how to charge or stop charging. You could have one battery at 11 volts and one at 13 volts but the charger will think it is fully charged because the combined voltage equals what it is looking for. I have seen this happen.

Even though it is more work to connect/disconnect the two chargers, you will actually get both batteries properly charged as each one will have it's own independent voltage and hence each charger will be based on its charge rate of that single battery.

My .02 worth.

 

[NDT]

On the ex-military fire equipment I maintain, I fixed mounted the two BatteryMinders with a 110v whip cable that the fire crews know to disconnect just like on the pumpers.

 

[fireman5214]

I agree with this. On a hmmwv or a deuce or a 5ton I'd say just go with a 24v through the slave port.

But on the cucv's bastardized 12/24 system I'd charge each separately.

Not a huge difference either way.

That was actually my next question, we do have a deuce that is needed a tender as well that's going to be 24v. There is a 3rd battery on it for 12v accessories so I think that will need a 24 & 12v tender.

 

[fireman5214]

On the ex-military fire equipment I maintain, I fixed mounted the two BatteryMinders with a 110v whip cable that the fire crews know to disconnect just like on the pumpers.

That is our exact thing we are going to do, we have a battery maintainer on a John Deere Gator set up for EMS stuff on the Appalachian Trail & 1600+ acre state park. Just unplug it on the trailer and go.