Connectors to charge TT from TV battery

[tvoneicken]

I've been reading through umpteen threads about charging TT batteries from the TV but have not found much in terms of actual experience... I hope some of you that do it regularly can chime in here.

I'd like to emergency-charge my TT batteries from my TV when solar doesn't work and I wonder whether there's a simple/cheap set-up that avoids dealing with std jumper cables. Are 100A Anderson powerpole connectors sufficient? I worry about the spark when connecting... Or would I need an additional on/off switch rated >100A in there? Anyone have experience?

Also, is anyone using the "15 minutes engine on, 15 minutes engine off" protocol that Andy describes in https://rvlifemag.com/west-coast-adventure/ and can relate how well it works?

--

Background is that I have 250W solar which works great almost all the time. In the past 10 years I've only used the Yamaha generator that I carry a handful of times (< 4x). Yet I carry this 80+ lbs thing on the trailer tongue (behind the propane tanks) on every single trip and deal with draining the gasoline that I don't use at least once a year to refresh it. I'd really like to eliminate the gen...

The TV is a 4Runner and charging through the umbilical cord doesn't work because the alternator's voltage is controlled based on the TV battery, and since that's typically charged, the alternator just doesn't output enough voltage to help the TT battery. Plus, of course, the cable losses (but that's not the dominant issue).

The upshot is that the simplest fix is to use a jumper cable from battery to battery to bring the TT battery (2x Trojan T-105, 250Ah) up from, say, 50% to 70%-80% in around an hour. That requires 40-50A, which should be quite doable. I'm not trying to get the TT battery to 100%, that's way too inefficient like this.

An alternative to a jumper cable could be to use a DC-DC converter, but that's one more thing to buy and install and manage...

[rmkrum]

Jumper cables are handy for lots of things, and easier to install than the wiring for 100 amp PowerPoles, IMHO.

[Bill M.]

I think you should consider adding a 12 volt to 12 volt converter to your trailer connected by the Anderson connectors. I doubt if you need 100 amp wiring but certainly 30 or so. Bass fisherman use a system like this to keep the boat battery charged while towing. The 12 volt converter takes the TV alternator control out of play and delivers the proper charging voltage just like a 110 converter does. The 12 volt converter will not charge unless the alternator is running so it eliminates the possibility of running down the TV batteries.

[uncle_bob]

Hi

Your truck engine and truck alternator will not be happy running for hours on end to get a useful charge into your batteries. Far better to get a 20 to 30 pound generator for a couple hundred dollars.

Bob

[tvoneicken]

Originally Posted by rmkrum

Jumper cables are handy for lots of things, and easier to install than the wiring for 100 amp PowerPoles, IMHO.

Agreed, they're just not very safe... The TT batteries in particular are nicely recessed into a grounded all-metal box in the trailer tongue. If the positive clamp slips there's a 99% chance for it to touch some of that metal. OK for a quick jump-start, but not so great to have hooked-up for an hour or so.

[rmkrum]

Sigh. That’s scary. My battery box is all plastic, but it’s not OEM. It was swapped out to allow golf cart batteries to fit on the tongue.

[uncle_bob]

Hi

Ok, I'm sitting here on solar in the middle of a farm field. I'm happy that I'm at 83% at 9 AM. I can go down to 0% with what I have so I'm a long way from panic stage.

In order to get me bothered enough to actually haul out the big heavy generator and fire it up, I'd have to be down below 25% at the end of the day. Otherwise, I'll just sing "Sun is Gonna Come out Tomorrow .." and keep on running down the batteries.

I happen to have Lithium's so I can charge them back up fast if I need to. That was one of the reasons for getting them and it *is* part of why I procrastinate ( a very small part ...).

If I had lead acids things would be a bit different.

If I only run them down to 50% before I panic, that's just a different number, no big deal there. I might run further, but even I am not quite that lazy. Once I fire things up, all goes fairly quickly back up to the 70 to 80% point. If they are 200AH (pair of stock AGM's) the typical 30A charge will be a bit over an hour. Getting them up to 100% is going to be another 3 to 5 hours past that.

Keep in mind that since we are going from 50% to 100%, the 70 to 80% point is only "half full". Stopping there is indeed leaving a lot of battery still empty.

This guy is amazingly quiet (and expensive) It weighs 29 pounds:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Slightly lighter and slightly cheaper:

https://www.amazon.com/Yamaha-EF1000...3320&s=gateway

33 pounds and a *lot* cheaper:

https://www.amazon.com/Westinghouse-...gateway&sr=8-3

All of then appear to be able to do a fine job of taking your batteries back up to "full" on a (small) tank of gas. Needless to say, there are a whole lot of others on the market. I have used the Honda. No direct experience with the other two. Compared to most truck engines, I'd bet the Honda is quieter ....

Bob

[ROBERT CROSS]

Bob

That is one heavy 'fluke'...😂

Mine is much 'lighter'...👍

Bob
🇺🇸

[Bill M.]

But if you move from place to place every few days it would be nice to have the TV actually charge the trailer while you are towing it. Maybe the OP meant he wanted to charge the battery with the truck while sitting in a field? I was thinking charging while towing. the 12 to 12 converter would be great for that use. Maybe working your way west through forest service campgrounds, etc. I am dirt cheap and do not boondock a lot. So I have a generator and so far no lithiums.

https://www.amazon.com/Renogy-Batter...gateway&sr=8-3

[pteck]

Originally Posted by uncle_bob

Hi

Your truck engine and truck alternator will not be happy running for hours on end to get a useful charge into your batteries. Far better to get a 20 to 30 pound generator for a couple hundred dollars.

Bob

Originally Posted by uncle_bob

Hi

Ok, I'm sitting here on solar in the middle of a farm field. I'm happy that I'm at 83% at 9 AM. I can go down to 0% with what I have so I'm a long way from panic stage.

In order to get me bothered enough to actually haul out the big heavy generator and fire it up, I'd have to be down below 25% at the end of the day. Otherwise, I'll just sing "Sun is Gonna Come out Tomorrow .." and keep on running down the batteries.

I happen to have Lithium's so I can charge them back up fast if I need to. That was one of the reasons for getting them and it *is* part of why I procrastinate ( a very small part ...).

If I had lead acids things would be a bit different.

If I only run them down to 50% before I panic, that's just a different number, no big deal there. I might run further, but even I am not quite that lazy. Once I fire things up, all goes fairly quickly back up to the 70 to 80% point. If they are 200AH (pair of stock AGM's) the typical 30A charge will be a bit over an hour. Getting them up to 100% is going to be another 3 to 5 hours past that.

Keep in mind that since we are going from 50% to 100%, the 70 to 80% point is only "half full". Stopping there is indeed leaving a lot of battery still empty.

This guy is amazingly quiet (and expensive) It weighs 29 pounds:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Slightly lighter and slightly cheaper:

https://www.amazon.com/Yamaha-EF1000...3320&s=gateway

33 pounds and a *lot* cheaper:

https://www.amazon.com/Westinghouse-...gateway&sr=8-3

All of then appear to be able to do a fine job of taking your batteries back up to "full" on a (small) tank of gas. Needless to say, there are a whole lot of others on the market. I have used the Honda. No direct experience with the other two. Compared to most truck engines, I'd bet the Honda is quieter ....

Bob

Geez Bob. Read the original post. Your inputs are not helping here. There's no concern in running a TV engine every blue moon for this.

[pteck]

Originally Posted by tvoneicken

I've been reading through umpteen threads about charging TT batteries from the TV but have not found much in terms of actual experience... I hope some of you that do it regularly can chime in here.

I'd like to emergency-charge my TT batteries from my TV when solar doesn't work and I wonder whether there's a simple/cheap set-up that avoids dealing with std jumper cables. Are 100A Anderson powerpole connectors sufficient? I worry about the spark when connecting... Or would I need an additional on/off switch rated >100A in there? Anyone have experience?

Also, is anyone using the "15 minutes engine on, 15 minutes engine off" protocol that Andy describes in https://rvlifemag.com/west-coast-adventure/ and can relate how well it works?

--

Background is that I have 250W solar which works great almost all the time. In the past 10 years I've only used the Yamaha generator that I carry a handful of times (< 4x). Yet I carry this 80+ lbs thing on the trailer tongue (behind the propane tanks) on every single trip and deal with draining the gasoline that I don't use at least once a year to refresh it. I'd really like to eliminate the gen...

The TV is a 4Runner and charging through the umbilical cord doesn't work because the alternator's voltage is controlled based on the TV battery, and since that's typically charged, the alternator just doesn't output enough voltage to help the TT battery. Plus, of course, the cable losses (but that's not the dominant issue).

The upshot is that the simplest fix is to use a jumper cable from battery to battery to bring the TT battery (2x Trojan T-105, 250Ah) up from, say, 50% to 70%-80% in around an hour. That requires 40-50A, which should be quite doable. I'm not trying to get the TT battery to 100%, that's way too inefficient like this.

An alternative to a jumper cable could be to use a DC-DC converter, but that's one more thing to buy and install and manage...

I've been toying with the same idea. I already have a large 4 gauge direct (fused) battery wire run along the length of my vehicle. Considering adding a large external Anderson Powerpole plug near the 7-pin for this purpose. One could mount a powerpole connector right off the battery at the front too, as that certainly would be safer than jumper cables to your point.

Separately, as you hinted at, many modern car alternators are now smart alternators. Once the primary starter battery is detected full, they don't hold at the excess voltage like older units did that's really necessary to charge an auxiliary battery. Perhaps if the trailer battery were tied in at start, pulling the voltage down, the alternator will hold a higher voltage to deliver sufficient charging current.

I really don't care to go down the DC-DC charging path. But it may be necessary to effect any real charging, independent of how it's hooked up.

My want for the anderson powerpole connector is less about charging, and more about power support for my 2000W inverter to run large loads. For example, pulling into rest stop for a quick lunch, leaving the tow vehicle running, and utilizing its power support to run the A/C off the trailer inverter.

[Al and Missy]

Why not put an inverter on the TV with the engine running and run an extension cord to the trailer to plug in the shore power. With AC and water heater off, the only load would be the converter. An inexpensive 750 or 1000 watt inverter should run the converter without any problems.


Al

[Adventure.AS]

I use a Warn winch kit with Andersen connector on 2 gauge wire that runs to the rear of the TV. A pig-tail with Andersen connector is wired to the trailer batteries. The power to the cable is triggered by a relay with a switch inside the TV. A fuse or circuit breaker is also a good idea on the positive lead from the TV battery.

[Sport 16 STL]

I was under the impression if you are driving down the road, connected to the tt, my Jeep Grand Cherokee would be charging the trailer batteries. Is this not correct?
I believe somewhere in the owners manual, it stated our solar panels would not be charging the battery if we were connected to the Jeep driving down the road.
A question I have looked for an answer is if you are parked you should always disconnect the trailer pin connector to the Jeep to avoid draining your car battery. Previous owner told us that.

We have a 2018 sport 16, with 2 solar panels.

[rickst29]

Originally Posted by Bill M.

But if you move from place to place every few days it would be nice to have the TV actually charge the trailer while you are towing it. Maybe the OP meant he wanted to charge the battery with the truck while sitting in a field? I was thinking charging while towing. the 12 to 12 converter would be great for that use...

https://www.amazon.com/Renogy-Batter...gateway&sr=8-3

That was a great post. Bill points at the cheapest of several products which pull more current through the Bargman "Trailer Battery Charge" (receiving power at LOW Voltage) then running it through a DC-DC "Boost" Converter, and then use a Solar Controller to reduce the Voltage back down to a correct value for current Trailer battery SOC. The two main parts (Boost Converter and Solar Controller) are enclosed within the single boxed product.

These products (Renogy, Redarc, etc.) are better than a basic DC-DC Regulated-Output "Boost Converter", because they adjust output Voltage (and power) according to your Trailer Battery State of Charge ("SOC"). A basic Regulated-Output "Boost Converter" (such as the Victron Energy Orion-TR 12/12-18A) only does half the job: You can adjust the output to one set value, but it doesn't adjust for battery SOC. And the 20A Renogy costs less money than that Orion does.
- - - -
But the Renogy contains a (cheap) PWM controller, and (SWAG) runs only 85-90% efficient when charging batteries. I think that it's efficiency varies according to the output Voltage: Set for Lithium @14.6, very little power is lost by PWM disconnect behavior. And "Boost Mode" SLA (maybe 14.4V?) would also waste relatively little. But lower output Voltage have lower efficiency. Their manual is very concerned with heat dissipation, and I think that's well justified: Higher-Voltage charging is more efficient, but also pushes more current, while Lower-Voltage charging in less efficient.

The Renogy costs much less than the comparable devices from Redarc. The Redarc devices are lot more expensive, but CAN run with connected Solar Panels at the same time they are pulling power from the TV. They also contain MPPT controllers, providing higher efficiency and generating only 1/3 - 1/2 as much heat. The Redarc machines can be mounted with much less concern for heat dissipation and airflow.
- - - -
However, both of these devices can pull 'somewhat high' current from the TV, through the Bargman cable. When the "20A" Renogy is putting out up to 250W on the battery side, the high current (through the Bargman and TV wiring) creates waste heat along the wires, resulting in "Voltage Drop" at the Renogy/Redarc input terminals. The input current might go as high as 25A. That's why I never recommend the Renogy 40A version - when batteries are at very low charge, it CAN damage Bargman cables.
- - - -
But you already have Solar Panels, and a Solar Charger. If it's a good one (MPPT), then I recommend that you connect the Bargman "12V Battery Charge" into a Regulated Output "Boost" Converter (either 10-17VDC input to 24V regulated output, or 10-17VDC input to 36V regulated output) and also buy a 5-pin automotive Relay. It's not complicated, but you need to read carefully:

Buy a 12V automotive Relay, capable of of higher-than-needed amounts of current. From the Bargman "Trailer Battery Charge", you pull two leads. A small lead goes into the Relay "control +". The big lead goes into the Boost Converter, and output from the Boost Converter goes into the normally-open "power" terminal on the Relay.

You remove your "Solar Panel +" lead from the MPPT Solar Controller, and connect it to the normally-closed (active) power terminal of your Relay. And finally, the Relay "Common" gets connected to the MPPT "Solar Input "+". Then connect all the "-" leads together (to the frame, or to battery "-".

When the Bargman receives ~12VDC from the Tow Vehicle (any tow vehicle), the Relay Coil will close the "normally open" terminal, disconnecting the "normally closed" Solar Panels in the process. Your MPPT Controller will see a change in input Voltage (as if clouds "appeared" or "disappeared"), and it will adjust to the new panel characteristics: A REALLY BIG PANEL, with V(mp) at either 24V or 36V.

You have just three rules to add into your configuration. FIRST RULE: The "Boost Converter" must have higher maximum power capability than the MPPT. (If the MPPT is allowed to draw more power from the Boost Converter than the Converter can deliver, the Converter will die and release a puff of "magic blue smoke". You must never let that smoke escape, it's magical.) SECOND RULE: The current on the Bargman is determined by the maximum current allowed on MPPT output, increased by inefficiencies of the Converter and MMPT, and by
Voltage drop which is seen at the end of the Barman under load. THIRD RULE: Do not exceed 25A on the Bargman, because this is a possibly continuous load.

Here's a calculation for an "OK, but maximum" configuration with 93% efficient MPPT and 90% efficient Boost Converter: 25A (bargman max) * 93% * 90% * 12.2V (SWAG for Voltage at the Bargman end after 'Voltage Drop', under high current) / 14.4V (Maximum MPPT Output Voltage) = 17.8A maximum allowable output current for the MPPT. On modern and decent MPPT controllers, this is programmable, and you need to set it.

Note that your 250W (max) Solar Panels are disconnected when you connect the 4Runner and turn it on, providing Voltage on the Bargman. But you only get 250W under standard test conditions (basically near noon on a cloudless summer day). If your MPPT chooses to charge at "only" 14.2V, you get just as power into the batteries while running from the TV - except that you can get all of that power continuously (even under clouds, or in the dead of night). On the Roadway, I always use my 4Runner.

[uncle_bob]

Originally Posted by pteck

Geez Bob. Read the original post. Your inputs are not helping here. There's no concern in running a TV engine every blue moon for this.

Hi

Well, I beg to differ. Idling a truck engine fast enough to charge a battery and doing that for hours on end is *not* at all a good idea.

Part of the original post *is* talking about not enjoying dealing with an 80 pound generator. Get a smaller / lighter one ....

From

https://www.powerstrokediesel.com/do..._Intervals.pdf

Ford Motor Company defines extended idling as follows:

Over 10 minutes per hour of normal driving Frequent low speed operation

Sustained heavy traffic less then 25 MPH

– One hour of idle time, is equal to approximately 25 miles of driving

If any 6.0L powered vehicle falls into the above categories it is classified under Severe Service Operations .....

Not a good thing.


Bob

[rickst29]

Originally Posted by rickst29

But you already have Solar Panels, and a Solar Charger. If it's a good one (MPPT), then I recommend that you connect the Bargman "12V Battery Charge" into a Regulated Output "Boost" Converter (either 10-17VDC input to 24V regulated output, or 10-17VDC input to 36V regulated output) and also buy a 5-pin automotive Relay. It's not complicated....

The design which I just explained (previous post) tops out at roughly 250W, limited by high current on the Bargman cable (and the 4Runner internal wiring which leads to the Connector, through the firewall and along the driver-side wiring channel). But it needed only one Relay and one Regulated-Output "Boost Converter", both located in the Trailer.

My own configuration is based on the same concepts, but provides nearly double the maximum power. Unfortunately, It is WAY more complicated to install. My DC Booster is under the hood of the 4Runner: https://www.ebay.com/itm/DC-12V-Step...w/172219128794.

Putting it in the TV allows me to completely prevent the problem of high current on the Bargman cable, obtaining about 460W (at my MPPT) while pulling less than 13A through the Bargman. BUT: Under the hood, my power wires from the battery "+" and frame "-" to the Booster input terminals are BIG, and fused separately. Also, because 36V actually appears on the Bargman, I need to control it with a dashboard switch - so that I don't fry other trailers which I pull. (Installing that dashboard switch was, by far, the most time-consuming part of the upgrade.)

And finally, within the Trailer, I needed another Relay - a special "24-36V Coil" Relay. They are not available in high-current 5-pin configurations. So the "detector" Relay opens or closes a +12VDC connection on the "power" leads, and that power goes into the 5-pin "automotive Relay on the coil control input. My way is a bit more complicated in the Trailer, and way more complicated in the 4Runner. But the 4Runner can provide al that power beautifully, and I'm using the original standard alternator (V6, 2007). When recharging in camp, due to bad solar conditions with "excessive" electrical appliance usage, the 4Runner adjusts the alternator and also increases idle speed upwards a bit, in order to reach the minimum operating voltage required by the ECU.


It's sort of like a small generator. Not enough to run the Air Conditioner, but pretty quiet and CARB-compliant. Best of all: It has an 18 gallon gas tank, and I can drive it to a gas station whenever I need to re-fill.

[pteck]

Originally Posted by uncle_bob

Hi

Well, I beg to differ. Idling a truck engine fast enough to charge a battery and doing that for hours on end is *not* at all a good idea.

Part of the original post *is* talking about not enjoying dealing with an 80 pound generator. Get a smaller / lighter one ....

From

https://www.powerstrokediesel.com/do..._Intervals.pdf

Ford Motor Company defines extended idling as follows:

Over 10 minutes per hour of normal driving Frequent low speed operation

Sustained heavy traffic less then 25 MPH

– One hour of idle time, is equal to approximately 25 miles of driving

If any 6.0L powered vehicle falls into the above categories it is classified under Severe Service Operations .....

Not a good thing.


Bob

Sorry, but the duty cycle discussed by the OP is not this. You're talking about contractors and heavy duty users that daily idle for significant periods. And how that impacts the maintenance interval. That's categorically not the same as not being able to idle ones engine.

Especially on occasion. Might as well never drive a vehicle is one is so concerned about a little idling. Perhaps we should start another thread about diesel reliability.

[uncle_bob]

Hi

We're talking about *hours* of idling here (like 5 hours) to get the job done. The Ford stuff is getting bothered at 10 minutes.

Bob

[tvoneicken]

Sigh, looks like some people don't read the original post and simply hit the reply button with some 10 paragraph long canned message... pteck, thanks for chiming in here!

I wrote very clearly that I want to provide an emergency boost to the batteries to go from "almost empty" to "somewhat full". I'm using flooded cells and so going to 100% full takes way too long. Also, this isn't for a daily routine, but the once-a-year when solar is insufficient, for example when stuck in a forest and rainy weather for a few days.

The specific example I gave in the original post is to go from around 50% charge to around 70% charge on two T-105's, that's roughly 50Ah of charge.

The back-of-the-envelope calculation I made is that using Andy'protocol and assuming I get about 50A of current through the jumper cable, the TV would run 2-3x cycles of 15 minutes on / 15 minutes off, assuming the alternator can output close to 100A to put charge back into the starter battery and continue charging the TT battery. The TV has a group 24F battery, which has about a 50Ah capacity (but it's a starter battery).

These are just ballpark figures to check that this is plausible. I was hoping to hear from someone who does this successfully or who has tried and it didn't work.

I did look at the renogy DC-DC converter/chargers. They do look interesting and have the benefit of helping to charge the TT while driving. My concern is that the 20A version is too weak: in order to get a 20% TT battery charge, which is approx our daily consumption, I would need 2-1/2 hours of charging, which is starting to get long. Maybe I could run the TV in 15-minute on / 30-minute off cycles to compensate, dunno... The 40A version would fit the bill power-wise, but it exceeds the capacity of the umbilical cable, so can't help while driving without major cabling work (there's a 5A mode, it seems, but if I make a mistake I end up with a busted fuse...). And I don't see the point of buying and installing the 40A version if a safe jumper cable can work better, faster, cheaper...

I'm not sure what to think about an inverter solution. The double-conversion is bound to have non-negligible losses and so far I have not seen anything close to the 45A charge current that my airstream converter is supposedly capable of. Plus, a 1000W inverter that I'd trust to reliably output at max capacity for over an hour is bound not to be that cheap. I would find the 20A DC-DC converter to be more interesting at about the same price point.