Battery Charge from Tow Vehicle

[Wardinbb]

Greetings folks, I have a question that I couldn't specifically find the answer to. I've replaced a perfectly operational Univolt with the Intellipower 9160 and actually got it all wired up property. I also installed the WestMarine 12 station fuse bus and yes the screws are a bit dainty for the A/S supplied wires, but you only have to do it once.

The question is about the charge wire from the tow vehicle. Is there some way to regulate the charge to the battery?

If you start on a trip with a fully charged battery and the charge wire is charging while you're on your way, won't it overcharge the battery or lend to boiling over? My charge wire comes directly off an accessory 30 amp lug at the fuse box under the hood, connects to the TV harness, passes through to the trailer where it flows through a 25 amp circuit breaker in the front belly pan and then hooks to the battery using the second lug of the 9160 as a bridge, where it connects on the loop to the battery. It seems to me that the TV charge just doesn't know that the trailer battery is fully charged. Is there a fix for this?

Thanks,
Ed

[john hd]

your voltage regulator in your tow vehicle will regulate the voltage to the battery just fine.

it would be the same as running two batteries under the hood. my '00 siverado has been running this way for quite a while with no ill effects to truck or trailer.

john

[john hd]

btw

here is how i did mine

http://www.airforums.com/forum...ead.php?t=3770

john

[RoadKingMoe]

It depends on your vehicle's voltage regulator setting. Many these days only output 13.8V or so because of higher underhood temperatures, and that's no different than the Magnetek converter. You'd want to use a relay to keep the trailer from draining your tow vehicle battery.

However, if it's in the 14.5-15.0V range, it CAN overcharge your battery. If it's that high, you could use a high-current diode that drops 0.6V in the line to get it down some. In fact, many diode-based isolators have that much voltage drop, and you could use that instead of a relay.

It would be nice to have the higher voltage if your batteries were deeply discharged and you wanted to give them some bulk charging. In that case, you could use a 30A switch to bypass the diode for awhile.

[Wardinbb]

Thank you all.

I'm old enough to be of that previleged school age set when shop class still existed in Junior High. The first day of Electric Shop, Mr. Hellsley, as the name implies, hooked me up to those copper wands that you were suppossed to hold on to until the 'fish out of water dance' amused the other kids and instructor. Never did like that class and so I've been electrically challenged somewhat ever since.

Ed

[bryanl]

One of the more interesting ideas I have seen for effective house battery charging from a vehicle while driving is to use a charge controller. These things convert input power using whatever voltage and current is available to a battery charging current and voltage that is appropriate for the battery's state of charge.

Kinda' pricey, though.

[john hd]

'fish out of water dance'

here in wisconsin we call that the "crappie flop"

john

[RoadKingMoe]

Originally Posted by Leipper

One of the more interesting ideas I have seen for effective house battery charging from a vehicle while driving is to use a charge controller. These things convert input power using whatever voltage and current is available to a battery charging current and voltage that is appropriate for the battery's state of charge.

Kinda' pricey, though.

I've seen these used in marine installations. They can have a 3-stage algorithm including bulk, absorbtion, and float. Can't remember the manufacturer off-hand though.

[mswartz]

I have the Analytic Systems Ltd BCD605 12V controller for the AGM batteries in my A/S. This provides close charge regulation and avoids overcharging the trailer batteries by the tow vehicle. It is expensive but I feel it is justified to avoid damage to my batteries.

See their website at www.analyticsystems.com/products/bcd605.htm. A very well built Canadian product.

[87MH]

Originally Posted by Wardinbb

The question is about the charge wire from the tow vehicle. Is there some way to regulate the charge to the battery?....My charge wire comes directly off an accessory 30 amp lug at the fuse box under the hood, connects to the TV harness, passes through to the trailer where it flows through a 25 amp circuit breaker in the front belly pan and then hooks to the battery using the second lug of the 9160 as a bridge...

Some of the Airstream service Manuals I have seen recommend an 8 guage wire for the Tow Vehicle to Trailer hookup - that may be too small for the longer Tow Vehicle/Trailer hookups - especially for trailers with a rear mounted battery.

Reference:
http://www.windsun.com/Hardware/Wire_Table.htm (and others).

An 8 guage wire should be the MINIMUM for a 20 amp charge/useage rate. #6 for a 25 amp charge/useage rate. #4 wire for a 30 amp charge/useage demand.

Even though each tenth of a volt over the steady state voltage of the battery helps charge the battery, installing a too small interconnect wire certainly defeats the purpose utilizing the Tow Vehicle to charge the Trailer battery.

[john hd]

dennis

that would make sense if your second battery under the hood was your only source for the trailer.

#4 wire would be a bit of over kill by even my standards! (i always say go big or go home!!)

my rough guess is that in a state of discharge each trailer battery would draw around 2 to 6 amps. judging by what they do when i pull them out of the trailer at the end of the year, letting them sit on my work bench for a couple of weeks, then charging them one more time before putting them away. (this is how i discovered one of them had a shorted cell btw.)

without actually putting an ammeter in series on the charge line we are all just guessing at best, i gotta think even a #12 charge line is better than nothing!

john

[87MH]

Originally Posted by john hd

.......without actually putting an ammeter in series on the charge line we are all just guessing at best, i gotta think even a #12 charge line is better than nothing!

John:

I agree, a #12 IS better than nothing. The comment on a heavy gauge wire was made for two reasons -

One, a couple of Forumers indicated that they have some fairly spendy 12 volt controllers - I would have to assume that the reason for this is that they rely on the TV to charge their batteries during boondocking - as you are aware, your alternator could be putting out 250 amps, but with a #12 wire streched out 30 feet or more, barely a trickle would make it to the battery.

Two, I charge the MoHo batteries with a 40/200 amp charger every couple of weeks instead of relying on the Univolt. The "start" charge is always 15 amps or better - the batteries are a couple of years old now. Again, I assumed that the initial charge to a fairly discharged trailer battery would be pretty heavy.

I was trying to point out that, if you are spending the bucks for a (fairly) expensive charge regulating system for the trailer to get a charge from the TV (especially while boondocking) - don't let the kid at the service station run a 12 gauge wire from the alternator tie in point to the umbilical connector. The Umbilical will probably be no more than 10 guage, and I think the wiring from the umbilical tie in on the Sovereign from the connector to the fuse panel is also 10 guage. With the voltage loss induced by the connectors, the umblical line, and the in-trailer wiring, trying to save a couple of bucks running (for example) 12 gauge wire to the connecting point on the TV is simply not worth it.

Absolutely, the best way to size the wires to the trailer from the TV charge system is to properly size for the anticipated amperage draw. If you start with an almost fully charged battery, and you just want to "top it off" during the 4 hour drive to the campground, 10 guage wire may well be adequate. On the other hand, if you are going to rely on the TV charge system to keep the battery charged (running the engine for a minimum amount of time) during an extended boondocking session (for example, hunting season where the furnace may be running a lot during the night), 8 guage might be undersized.

The reason for my initial post was to make those (newbies?) who may be anticipating installing a TV/Trailer charge line aware that a roll of 12 gauge wire off of the shelf at MegalaMart may not be the wisest choice for their unique requirements.

[john hd]

The reason for my initial post was to make those (newbies?) who may be anticipating installing a TV/Trailer charge line aware that a roll of 12 gauge wire off of the shelf MegalaMart may not be the wisest choice for their unique requirements.

dennis

good one!!! i beleive it is meglalowmart!!!

you are exactly correct, you are not going to be able to either draw full current or fully charge without going full size on the charge line.

in a perfect situation one would need a seperate connector for the charge line, i doubt you would be able to connect a #4 wire to a 7 pin connector. let alone run 30 amps through it for any extended time.

my 10 gauge system works well for keeping my batteries topped off or recharging during drive after a night of running the furnace.

again, without putting an ammeter in line we are all just guessing!

but, my gut reaction is that you are closer to the ideal than the megalowmart 12 gauge route!!

john

[john hd]

dennis

btw,

not to change the subject, my new bucket truck at the power company has a 2500 watt inverter for power tools.

it is connected to the battery bank with 2/0 wire! i hooked a cheapo microwave to it so i can have hot lunches!

like i said, go big or go home!

john