Charging while towing

[Wolffarmer]

So, as I use only a little battery power and don't need a whole lot of charging power. Why not tap into the clearance lights with a resister, diode and fuse to keep from over loading that circuit and drive with the lights on?

I hope that hasn't already been covered as I am to lazy to read the whole thread or any others.

Randy

[absolutsnwbrdr]

So, as I use only a little battery power and don't need a whole lot of charging power. Why not tap into the clearance lights with a resister, diode and fuse to keep from over loading that circuit and drive with the lights on?

I hope that hasn't already been covered as I am to lazy to read the whole thread or any others.

Randy

That could work, if you were charging a pair of "AA" batteries. Vehicle lighting circuits are designed with light gauge wire and are not designed to handle any kind of additional load. Even wiring trailer lights directly to your tow vehicle lighting circuits can overload the circuit and dim your lights.

However, if you were to run wire heavy gauge wire from your battery to your hitch (with an inline fuse close to the batter) and then tie into your lighting system with a relay. The relay would only close the battery circuit whenever your lights are turned on. That would essentially be doing the same thing as the Yandina thing that I Installed, and for 1/10th of the price. The Yandina has a few other features that make it desirable, but the relay tied to the light circuit would be a 'thrifty alternative'.

[WhitneyK]

Vehicle lighting circuits are designed with light gauge wire and are not designed to handle any kind of additional load.

Apparently you didn't see the wiring portion of my build journal (I'm just kidding, don't everybody feel like they have to respond with all the technical detail of automotive design and wiring for crying out loud. It's a joke son, a joke, don't ya get it)

I wired mine up through the 7pin RV plug like "the big boys" do with a relay at the power connection on the TV plus another relay at the camper battery for our recent 2 wk trip out West. I installed a switch between the camper side of the plug and the relay / battery so I could tell it when to charge and not have to unhook and remember to hook up the plug when we just camped for a night at a rest park. (REST park is a miss-statement, what with all the big trucks idling, cars driving around, doors slamming.......) None of the NP's were electric sites, so we ran off battery power the whole time. Now granted we only ran interior lights, charged camcorder, camera, cell phone batteries, etc and powered an external HD for downloading pictures to, but I never ran out of battery. Nor did I flip the switch to charge the battery while going down the road. (although I should have just to see if the silly thing works as planned) By the time I got home it was just indicating that it was around 80% charge. I currently have the largest deep cycle battery AZ sells in my camper.

This tells me a few things,
1. Could have got by with a smaller / lighter battery
2. Charging while towing shouldn't have taken much
3. Should be in fine shape to go for a 1 wk vacation (which they are going to be for a few years)
4. I realize if it's warmer, fan will pull it down quicker AND
5. If it's cold, may be able to support a 12V heating device of some kind without a problem

[Bogo]

There are 12VDC to 12VDC battery chargers. They will obviously limit the amount of current going to the travel trailer battery. Usually they output somewhere from 5 to 40 amps charge current. You would need to set it up on a switched circuit so it only tries to charge the travel trailer when the engine is running. Some have a line that can be connected to the ignition circuit. The downside is they cost $$$ and require installation. If your tow vehicle already has an RV 7 type trailer connector, you can hook up the charger into the battery charge wire.

An option for a severely depleted battery is to use a set of jumper cables to initially get some charge into it so it doesn't suck down that high surge of current over the trailer wiring harness. Start your car up, then connect up the jumper cables properly. Let it charge for 15 minutes or so while the engine is running. Then it may be charged enough that it won't draw to much current.

It is possible to change fuses in cars over to circuit breakers. Catalog page with may types: http://www.waytekwire.com/products/1366 ... -Breakers/ Some even will fit into the blade type fuse holders, but usually they are taller and may interfere with covers. Some are automatic reset, and others are manual reset. Still others include a switch to help control the load.

A example of a 20A 12VDC to 12VDC battery charger: http://www.waytekwire.com/item/80125/SU ... CONVERTER/

I'm using examples from Waytek Wire because they have lots of stuff that is vehicle wiring related, and their prices are reasonable. They are more setup for industry use, but they will sell to us end users.

[Bogo]

Seeing nobody really brought these up, I will. Cooper Bussmann Sure Power battery separators will connect two battery banks together, using a high current relay, when the battery charger is charging, then disconnect them when the battery charger is off. They do this through voltage sensing. When it goes over a certain threshold, which is above resting battery voltage, they will connect the battery banks together allowing charging of both. Before the voltage goes over the threshold, only the battery bank on the charging source side will get charged. They also have a force connect input for jump starting, etc.. If you use an RV 7 type connector on the TV, then you hook this in line with the RV 7 supply wire. It can go either in the car or on the trailer. The units WayTek Wire handles from 100 to 300 Amps so their current carrying capacity is higher than the RV 7 connector pin current handling. One of the two 200 Amp units even handles charging from both sides of the relay so you could charge from the car's alternator, or say a solar panel on the trailer.

The 4 ones Waytek handles: http://www.waytekwire.com/products/1348 ... eparators/

Some people complain about using relays for controlling the connection, but they are cheap in comparison to doing it with the possibly more reliable electronic switch. We're talking significantly less than half the cost. I feel that is debatable because if the electronics aren't properly protected, then they can be more easily taken out by voltage spikes.

Diode based separators have the issue that the trailer's battery bank will never see full charging voltage so it never will get fully charged.

[absolutsnwbrdr]

I remember seeing the SurePower 1315 mentioned on here a while ago, but now I cant find the thread. I think the person had problems with it and returned it.

If you like the features of the SurePower and want a nicer package with the same features, I'd suggest the the Yandina. Paid $65 for mine. The thing I didnt like about the SurePower is that it has exposed contacts and could potentially become shorted out. The Yandina is 100% sealed and waterproof.

[Bogo]

One more post.

For recharging a trailer at a camp site that allows generator use. A small quiet inverter generator can be used, but don't use their built in battery charging circuit. None of them are regulated at all. Instead use the generator to power a standard smart multistage battery charger, possibly one of the standard built in RV battery charger/power supplies. Another thing to consider is the last 5% to 15% of the charging goes at a much slower rate than the main bulk of the charging happens at. When the charger gets into that stage of the charging cycle, turn off the generator and save the fuel. Doing this will also help extend the life of the battery. Most damage to batteries comes when deeply discharged, or during the last few % of the recharge. BTW: if you monitor how much gas it takes to recharge X% of your battery's charge, you can fuel the generator for only that amount, and let it run out of gas to shut if off. I used to do this with gas powered pumps that I used for filling the stock tanks.

[bdosborn]

Seeing nobody really brought these up, I will. Cooper Bussmann Sure Power battery separators will connect two battery banks together, using a high current relay, when the battery charger is charging, then disconnect them when the battery charger is off.

Unfortunately, the sure power is a POS and they are a miserable company to deal with. Mine worked for about a week and then combined anytime there was voltage at any level present. I noticed it was combined as the ~1/2 amp overhead of the solenoid showed up on my Trimetric meter when I wasn't plugged in to shore power. Sent it back and it took no less than 30 (*thirty, I saved and counted them*) emails and several unpleasant phone calls just to get them to return it. They told me it was fine and it promptly combined at 12.8 volts when I put it back in the trailer. Grrr. It's sitting in the garage, you can have it for postage. BTW, it *has* to be installed at the TV battery per the tech I talked to, despite the fact their literature that shows it installed in a trailer.

The Yandina has been working fine for 2 years now.
Bruce

P.S. They have a recall out because of the fires.
http://www.cooperindustries.com/content/public/en/bussmann/transportation/recall_info_NA.html

[absolutsnwbrdr]

Bruce I was pretty sure it was you!! Couldnt find the thread though.

[Mukilteo]

Got this from a post from somewhere here a while back.
I can't remember the orginal post.
I works on my Nissan nicely.
I think a continuous duty solenoid From the auto parts store would be better then the relay that is listed.

Here are the parts you need:

Parts necessary from
http://www.radioshack.com/
1 ea. # 275-226 12VDC/30A SPST Automotive Relay, $6.49
1 roll #278-569 35-ft 10-Gauge Hookup Wire-Black, $14.99
1 pkg #270-1084 25A Blade-Type Automotive Fuses, $1.99
1 ea. #270-1234 30-Amp Inline Blade-Type Fuse Holder, $2.49
1 pkg #278-1632 4" Nylon Wire Ties, $1.99
1 pkg #64-3111 12-10 Gauge Shrink Butt Connectors, $1.99
1 pkg #64-3140 Low-voltage Tap-Ins, $1.99
1 pkg #64-3120 Insulated Ring Connectors, $1.99
2 pkg #64-3137 1/4" Crimp-On Quick Disconnects, $1.99
Combo 7-pin Round/4-pin flat adapter with mounting bracket - Auto Zone $24.99


Here are detailed instructions:

Installation:
If your vehicle already has a trailer battery charge wire routed from
the 7-pin connector to the engine compartment, you can skip steps 1-5.
1. Disconnect the negative cable at the battery.
2. Jack up vehicle and support using stands.
3. Connect 10 gauge wire to "Battery Charge" pin of 7-pin connector.
4. Route the 10 gauge wire under the vehicle to the engine compartment.
Use tie wraps to secure the wire and keep it away from heat and
mechanical hazards.
5. Bring the 10 gauge wire up into the engine compartment near the
battery.
6. Mount the 30A relay near the battery using an existing screw, or
drill a hole for mounting.
7. Cut a 6" length of wire off the end of the 10 gauge wire.
8. Crimp a quick disconnect "female" connector to one end of the 6"
wire.
9. Crimp an ring connector to the other end of the 6" wire using a ring
with a hole large enough for the relay mounting screw to pass through.
10. Put the relay mounting screw through the ring connector on the 6"
wire and mount the relay.
11. Slide the quick disconnect connector onto the low current "ground"
lug of the 30A relay.
12. Locate the positive terminal of your battery.
13. Determine if the positive battery cable already has an unused 10-12
gauge auxiliary wire. If so, simply insert one lead on the 30A fuse
holder into the butt connector provided and crimp it. Skip to step 22.
14. Otherwise if there is no visible auxiliary wire, determine if the
battery uses top mount stud or side mount cables.
15. If it is a top mount stud, select a ring connector with a hole large
enough to clear the batter cable tightening bolt.
16. Crimp the ring connector on one lead on the 30A fuse holder.
17. Put the ring connector over the battery cable clamp bolt, re-install
the nut, and tighten sufficiently. Skip to step 22.
18. Otherwise if the battery uses side mount cables, follow the cable to
the starter solenoid. Disconnect the battery cable from the solenoid.
19. Select a ring connector with a hole large enough to clear the batter
cable stud on the solenoid.
20. Crimp the ring connector on one lead on the 30A fuse holder.
21. Put the ring connector over the solenoid stud, re-install the
battery cable and nut, and tighten sufficiently.
22. Cut a length of wire off the end of the 10 gauge wire long enough to
reach from the fuse holder to the relay. Leave enough to secure the
wire with ties.
33. Connect one end of the wire to the fuse hold using a "butt"
connector.
34. Crimp a "female" quick disconnect to the other end of the wire.
35. Slide the quick disconnect connector onto the high current +12V lug
of the 30A relay.
36. Route the 10-gauge wire from the 7-pin connector to the relay and
cut off leaving enough length to secure with tie wraps.
37. Crimp a "female" quick disconnect to the end of the wire from the
7-pin connector.
38. Slide the quick disconnect connector onto the high current negative
lug of the 30A relay (opposite side).
39. Crimp a "female" quick disconnect to one end of the remaining loose
10-gauge wire.
40. Slide the quick disconnect connector onto the low current positive
lug of the 30A relay (opposite the ground lug).
Now you have done the easy part ;-).
41. Locate a source of +12V switched by the ignition key (i.e. only
"hot" when the key engine is running). For older cars you may find that
another terminal at the starter solenoid will meet this requirement.
For newer cars you can call a local automotive electrical shop, or
possibly get a wiring diagram from the library or a purchased manual.
42. Use the "Low-voltage Tap-in" to connect the other end of the low
current positive wire from the 30A relay to the source of switched 12V
power.
_________________

[Bogo]

That's a bummer on the Sure Power battery separators. They used to be good. All the units I've dealt with in the past have worked flawlessly, but we're talking about ones made well over a decade ago. Looks like they changed parts suppliers or the design.

Oh, on a similar vein, Optima batteries. A few years back they changed manufacturing processes and then manufacturing plants. They are no longer the high quality USA made battery they once were. The newer ones aren't handling high current draws like from winches. Also they are near impossible to recharge or get to keep a charge if they ever get nearly fully discharged. They've gotten a bad name in the off roading communities.

[ntsqd]

I read thru all of this and while I can appreciate the idea that all you need to do is to unplug the trailer while camped I know that eventually I would forget to do that. Or I'd forget to plug it back in when leaving. So.... that option is out for me. Early-on there was mention of "how the RV folks do it." I've seen some of their work, and not just the so-called "service centers" but a couple factories. Count me out of that. Most RV specific electrical parts are such that as a mfg I'd be ashamed to sell them. I go right past all of that and look at marine parts. They're more expensive in general, but how many times do you want to buy something for a single job? I want to buy it once and a failure within this decade is too soon. I consider something 10 years old "just broke-in."

Search out the "HandyBob" blog. It is a long and somewhat painful read about full timing on just solar panels, but his lessons learned (& shared!) are worth digesting as some of it pertains to vehicle electrical in general. The biggest thing that I took away from his blog is that voltage drop (VD) should be avoided at all costs. You don't really have 12 volts to play with. Fully charged most types of batteries sit around 12.6 volts. A 50% discharged battery has a standing voltage of about 11 volts (% discharge is defined as remaining amp-hrs, not voltage) and that is as low as you will want to go if the battery is to have a long life. So you have ~1.5 volts to play with. Suddenly the 5% voltage drop that used to be acceptable isn't very acceptable any more as that 5% VD just dropped you from 12.5 volts down to 11.9 volts or 42% of your margin. Or consider this in the TV to TD charging wire. Most automotive regulators top out at around 14.4 volts. Only the wire going to the TD has a 5% VD in it. So now that 14.4 volts is 13.7 volts at the TD's battery. 13.6 volts is about the minimum possible charging voltage, so you're barely there. Meaning that the system will barely be able to charge the TD's battery(ies). The higher the charging voltage, to a point of damaging the battery(ies), the greater the amps that can be 'stuffed' into the battery. (I'm grossly simplifying a lot of nuances about the care & feeding of batteries.)

At any given state of charge and charging voltage the battery will accept a finite charging rate. It will accept less, but it won't accept more unless the charging voltage is increased. When considering voltage drop the grounding length needs to be included in the total length of the circuit. Looking at Ancor Marine's chart for sizing wires for a given voltage drop (I'll use their 3% VD chart) over a set distance (say 15' battery to battery, so 30' overall) with a specific charging rate (arbitrarily picking 20 amps) I find that a 6AWG wire is called for. Using all of the same numbers, but looking at their 10% VD chart only a 12AWG wire is called for. Quite a difference in wires.

Another thing that I noticed in some of the wiring diagrams posted earlier in this thread was that the trailer frame was used for the ground path. My experience has been that this is an all too frequent cause of trouble with trailer lighting. I don't live in a particularly wet climate, officially I live in a "Coastal Desert", but even here rust and corrosion plays havoc with those grounds. In the future I will ground to the trailer frame, but all lights will have their own ground wire connected to the main ground wire and not rely on the trailer frame to carry the ground for any distance.

[Shadow Catcher]

I have the conventional seven wire trailer connector, lights brakes etc. the wire through that for power to the battery is 10 ga and a line runs to the battery that is that.
One thing often not taken into effect when calculating voltage drop is alternator voltage. The Subaru voltage at the battery is 14.2 volts I have less than a 15' run but will use that for calculations. This gives a voltage drop of .60 volts or 13.6 V at the trailer. However there is the 185W 66 cell high voltage panel stuck to the top of the trailer that will back feed into the TV battery if I were to forget to unplug.
One of the things Handy Bob emphasizes is monitoring battery state of charge and I went with a Victron battery monitor because of its small size and easy set up. Monitoring battery condition by voltage alone does not tell the story, or at least not easily. My feeling is that while you will not get the most charging through the trailer connector how often would you need to. If I need to get it in fast I have a set of 000 welding cable jumper cables that I can run from the TV battery to the trailer battery.

[bdosborn]

I have the conventional seven wire trailer connector, lights brakes etc. the wire through that for power to the battery is 10 ga and a line runs to the battery that is that.

My truck with the factory towing package had a #16 wire back to the 7 way connector. It was basically useless due to voltage drop.

Bruce

[ntsqd]

15' or 30' in your calcs? The ground path needs to be included or the calcs are off.

X2 on a real battery monitor and not just a voltmeter. I went with the Trimetric, but I'm still in the process of setting it up (other things got in the way). After pricing out those T-125's that came with our pop-top slide-in camper I realized that if I didn't want to semi-frequently spend money on replacing them that I needed to step up my monitoring ability.

There is more to this than simply the rate of charge as a low charging voltage will never fully top off the TD's battery. Which will result in poor performance and life span from that battery. BT, DT. IMO adding solar with a quality solar charge controller is the best mod since it will top off the battery regardless of how long you drive or what the wire gauge is between the TD's battery and the TV's alternator. wire it right and you may not even need the TV to TD charging wire.

On our camper I went with 6 ga. charge and ground wires for a total run length of about 24 feet. I did that not for charge rate, but for voltage drop.