Charging with a "Battery Tender" while traveling

Offtrail

Member
Have had great success with "Battery Tender" over the years. Leave our other car on them when we travel for months at a time and one was on my motorcycle for 2+ years and all was fine. https://www.batterytender.com/Battery-TenderR-Plus

We have an AC outlet in the bed of our 2020 Titan SL. We could plug in a battery tender while driving to insure fully charged batteries for boondocking. It would never overcharge our 2 Group 29 deep cycle wet batteries alone, but how would it react with the charge coming through the 7 pin connector from the truck engine? Not sure if that is a smart charger or a trickle...or its amps?

Thanks,

Chas
 

danemayer

Moderator
Staff member
If you had a solar installation on the trailer, I think it would be a similar situation with two 12 volt power sources and not be a problem. Some people run an on-board generator (for air conditioning) while towing. That also would fire up the trailer's power converter and you'd have two 12 volt power sources. I'm not aware of either scenario causing problems, so I think you'd be ok,

If using clip on connections to the batteries, road shock and vibration could be a problem though. You might want a pluggable connection using ring connectors at the batteries.
 

CoveredWagon

Well-known member
Re: Charging with a "Battery Tender" while traveling

I recommend you call Deltran and talk to their techs, I don't think your idea makes sense. When towing your converter is generating AC from the batteries which you want to convert, through the battery tender to dc to charge the batteries.
 

RoadJunkie

Well-known member
Just make a mating connector from your BT to the solar prep connector on your rig. There is no active circuitry at that input. Make sure the entire wire string, and fusing, is adequate to support the current from your BT unit.
 

danemayer

Moderator
Staff member
Re: Charging with a "Battery Tender" while traveling

I recommend you call Deltran and talk to their techs, I don't think your idea makes sense. When towing your converter is generating AC from the batteries which you want to convert, through the battery tender to dc to charge the batteries.

I think he's saying his tow vehicle is supplying 120V AC to the battery tender, which he intends to connect to the trailer batteries. The trailer Power Converter is not getting any 120V AC while towing.
 

wdk450

Well-known member
Re: Charging with a "Battery Tender" while traveling

I recommend you call Deltran and talk to their techs, I don't think your idea makes sense. When towing your converter is generating AC from the batteries which you want to convert, through the battery tender to dc to charge the batteries.

This is akin to the idea of "perpetual motion machines" which fail because there is always friction of some sort - air, mechanical or other. Your inverter is only about 90% efficient, so that 10% of the input power from the batteries to the inverter is lost in the inverter, so you only get 90% of the power input at the 110 VAC inverter outputs.

I have a 3500 watt true sine wave inverter wired into my generator transfer switch's (no generator ever installed). When I switch on inverter power, I make sure to turn off the AC breaker to the converter/battery charger, so I am not wasting battery capacity trying to simultaneously charge the batteries.
 

centerline

Well-known member
Have had great success with "Battery Tender" over the years. Leave our other car on them when we travel for months at a time and one was on my motorcycle for 2+ years and all was fine. https://www.batterytender.com/Battery-TenderR-Plus

We have an AC outlet in the bed of our 2020 Titan SL. We could plug in a battery tender while driving to insure fully charged batteries for boondocking. It would never overcharge our 2 Group 29 deep cycle wet batteries alone, but how would it react with the charge coming through the 7 pin connector from the truck engine? Not sure if that is a smart charger or a trickle...or its amps?

Thanks,

Chas

this would work... but not feasibly or economically. the output isnt high enough to make it worth the trouble.

one still needs power to run the battery tender, so, you are going to have to run the generator to power it, or run it from a cord coming from the inverter from your tow vehicle.... which running the generator makes the most sense, in which case you dont need a battery tender, as your onboard charger will do all the work..

as ive said, running a battery tender from the small inverter on the tow vehicle STILL requires a wire to be run to the trailer from the tow vehicle, which running a permanently installed 12v circuit of 8-10awg size would make the most sense.....

another thing to consider is, the "2 amp" battery tender is rated at its highest output, which will be what it puts out if the battery is low, but like any other stage charger, as the voltage in the battery gets higher, the input from the charger drops off.... which means if the battery is at 85%, you may only be getting less than an amp from the tender into the battery, which will take a very long time to top a battery up.
a properly sized, dedicated 12v circuit from the tow vehicle would do better than that....

solar is the ultimate in battery charging.... no, it doesnt work at night, but its a dependably working unit ALL day, EVERY day, no matter the status of whether you are connected to a tow vehicle, power post, or nothing at all..... ALL without any need for you to do anything more than service the batteries like you are doing now...
 

Oregon_Camper

Well-known member
The Battery Tender will provide ~1.5amps...at best and you have to deal with getting AC power to it.

Your best solution is a 100 watt panel on the roof. On average a 100w panel will about 6 amps per peak sun hour, or about 30 amp-hours per day. Plus it will work every day with no action on your part.

Here is a video I did on using two 100w panels for my portable solution. You could do two on your roof (not portable like my video show), but start with one to see if that covers your needs. Adding another one (if needed) is easy.

https://youtu.be/N4Mm3pPU5W4
 

Offtrail

Member
Re: Charging with a "Battery Tender" while traveling

I think he's saying his tow vehicle is supplying 120V AC to the battery tender, which he intends to connect to the trailer batteries. The trailer Power Converter is not getting any 120V AC while towing.

This is correct. Thank you:) Sorry I didn't make it more obvious.

The truck inverter coverts DC to AC with 2 normal looking AC female receptacles. One is in the back seat and one at the very back of the bed, drivers side. They work well and have powered a heating pad for cold folks in the rear seat. Engine must be running.

I imagine a simple AC extension cord plugged into the bed outlet to get the Battery Tender to the trailer batteries at the front of the trailer, which we will only operate when we are towing. If others utilize 2 charging feeds to the trailer batteries, especially when one is a "smart" charger, sounds like will give it a try. Am also attempting to reach Deltran support.

We do not have solar and yes it is in our future.

If this works, won't be available in wet weather as the Battery Tender has grills to release heat. They have a waterproof version but it only delivers .8 Amps.

One other question. We have a old style 6 amp, non intelligent, Sears charger. Not for use in the specific application we are discussing, but is it worth carry this with us for general battery charging? Do most folks find them valuable enough to bring along?

Thanks all.
 

Offtrail

Member
The Battery Tender will provide ~1.5amps...at best and you have to deal with getting AC power to it.

Your best solution is a 100 watt panel on the roof. On average a 100w panel will about 6 amps per peak sun hour, or about 30 amp-hours per day. Plus it will work every day with no action on your part.

Here is a video I did on using two 100w panels for my portable solution. You could do two on your roof (not portable like my video show), but start with one to see if that covers your needs. Adding another one (if needed) is easy.

https://youtu.be/N4Mm3pPU5W4

Thanks. Interesting location for the panels, tonneau cover of the truck!
 

danemayer

Moderator
Staff member
Re: Charging with a "Battery Tender" while traveling

One other question. We have a old style 6 amp, non intelligent, Sears charger. Not for use in the specific application we are discussing, but is it worth carry this with us for general battery charging? Do most folks find them valuable enough to bring along?

Thanks all.

It's handy to have a higher output battery charger with you. If the trailer's Power Converter were to fail, assuming you have shore power available, the battery charger will keep your batteries charged and keep you from cutting a trip short. Even without shore power, if your truck supplies enough power to its outlet, you could run the truck to charge the battery - although if you have the reach, jumper cables might be more efficient.

Our Converter came unplugged on our first trip. I picked up a battery charger at the nearby Walmart and used that until I found the problem. I've since used it several other times when something failed and I wasn't ready to go home.

I would not use the unintelligent charger however.
 

Oregon_Camper

Well-known member
Thanks. Interesting location for the panels, tonneau cover of the truck!

LOL....that does seem strange, but it was the PERFECT location to capture the morning sun. Here in Oregon we have a LOT of large....LARGE trees...so I find myself moving my portable setup a few times a day
 

Offtrail

Member
Re: Charging with a "Battery Tender" while traveling

It's handy to have a higher output battery charger with you. If the trailer's Power Converter were to fail, assuming you have shore power available, the battery charger will keep your batteries charged and keep you from cutting a trip short. Even without shore power, if your truck supplies enough power to its outlet, you could run the truck to charge the battery - although if you have the reach, jumper cables might be more efficient.

Our Converter came unplugged on our first trip. I picked up a battery charger at the nearby Walmart and used that until I found the problem. I've since used it several other times when something failed and I wasn't ready to go home.

I would not use the unintelligent charger however.

Would you have a recommendation on a "smart" higher output battery charger?

Not really related, but we do carry and jump starter.

Thx
 

danemayer

Moderator
Staff member
Re: Charging with a "Battery Tender" while traveling

Would you have a recommendation on a "smart" higher output battery charger?

Not really related, but we do carry and jump starter.

Thx

Mine's 10 years old so it's probably not even available today. My Landmark has an 80 amp Power Converter. The charger I think has 40 amp output which has been enough to keep things going in a pinch.

Alternatively, shop a 60 AMP Power Converter and add wires/clamps and plug if necessary.
 

Oregon_Camper

Well-known member
We could plug in a battery tender while driving to insure fully charged batteries for boondocking.

Perhaps I am missing something here, but a battery tender output is ~1.5amp. You'd have to drive 10 hours to put back in 15amps. I'm guessing your truck will deliver more than that via the 7-way plug.

Seems like a lot of effort to get 15amps into your battery, by driving 10 hours, or more realistic 7.5amps by driving 5 hours.

Perhaps adding another battery would provide the extra amp hours you're hoping to achieve.
 

centerline

Well-known member
Perhaps I am missing something here, but a battery tender output is ~1.5amp. You'd have to drive 10 hours to put back in 15amps. I'm guessing your truck will deliver more than that via the 7-way plug.

Seems like a lot of effort to get 15amps into your battery, by driving 10 hours, or more realistic 7.5amps by driving 5 hours.

Perhaps adding another battery would provide the extra amp hours you're hoping to achieve.

just an FYI.
a battery tender rated at 1.5 amp will NOT deliver 15 amps in 10 hours, but nearly so if the battery is fairly low, in which case giving it a trickle charge to bring up the low battery is unhealthy for the battery....
a trickle charger is for maintaining a fully charged battery, and if its a quality maintenance charger, it will reduce its output as the battery voltage increases, the same as any other good charger... and when the output is reduced, it takes longer to put an amp into the battery, in addition, any normal battery charger is only about 80% efficient, which means there are more amps being created from it than the battery is taking in... anytime power is moved from one place to another, there is a loss in the process of moving it....
 
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