RV Trip Planning Discussions

Go Back   iRV2 Forums > TRAVEL TRAILER, 5th WHEEL & TRUCK CAMPER FORUMS > Travel Trailer Discussion
Click Here to Login

Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 02-12-2019, 10:58 AM   #57
Senior Member
 
Join Date: Jun 2018
Location: Los Angeles area
Posts: 174
Quote:
Originally Posted by SV Tom View Post
If the 12 volt outlets on generators that have cables with battery connectors on them are not meant for charging batteries what are the meant for ?
There are versions of the generators sold in other parts of the world that have electric start. They use a battery roughly the size of a motorcycle battery to run the starter. The battery charging connector is to recharge that starting battery. The connector in unusual on purpose.
__________________

__________________
Semi-retired electronics / computer / network / 2-way-radio / ham radio... (WA6ILQ)
1985 Fleetwood 32' Southwind, dubbed "Lazarus" by friends... I resurrected it from the dead...
AnotherMike is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 02-12-2019, 11:14 AM   #58
Senior Member
 
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 296
So, What do we all know now?

We know there are as many different engine 12 volts systems as there are models of engines and years of production.
We know there are as many different RV power management systems as there are RV models and years of production.
We know there are as many different 12 volt demand profiles as there are RV and TT owners.

The original question was about TT's, not RV's. We know that most TT's get some charging current from the tow vehicle. A very few deliver enough 12 power to fast charge a bank of house batteries. Certainly, high draw appliances in the TT require exceptional tow vehicle alternators, exceptional connecting cables, and exceptional electronic power management to both maintain a battery bank and supply the high draw appliances.

Many TT's owners use shore power, standalone generators, built in generators, and/or solar power to charge and maintain charge on their house batteries. Almost all use tow vehicle charging, but do not depend on it to provide charging to house batteries.
__________________

__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
Persistent is offline   Reply With Quote
Old 02-12-2019, 11:14 AM   #59
Senior Member
 
Join Date: Jun 2018
Location: Los Angeles area
Posts: 174
Quote:
Originally Posted by Hangfive View Post
Motorhome alternators do not charge the house batteries. Chassis batteries only!
That's a rather absolute statement and might be true on your MH, and maybe others of the same vintage.

But I can say that my 1985 came stock with a charge splitter that feeds both the chassis and house batteries. The stock GM alternator has an extra input (the "sense line") that is designed for charge splitter situations. The sense line is connected after the charge splitter so the 0.7 volt drop created by the splitter is compensated for by using the sense line to raise the alternator output by an additional 0.7 volts.

The sense line method has it's own set of problems - if you hook it to the chassis side it shuts down the aternator when the chassis battery is up to voltage - and the house batteries won't get fully charged. If you hook it to the house side you risk overcharging the chassis battery. After my roof issues and a few other issues are resolved I'm going to remove the charge splitter and install a Yandina C100 Battery Combiner in parallel with the aux start relay.

That little magic box was designed for sailboats with starting batteries charged by an alternator and house batteries charged with solar panels... it connects the house and chassis batteries together (with a 100 amp solid state switch - no solenoids, contactors or relays!) when ether one is charging... this means that in the case of an RV the alternator will charge the chassis battery and through the C100 will charge the house battery... and the solar will charge the house battery and through the C100 will keep the chassis battery charged.

If this sound interesting go to yandina.com and look up the C100.
__________________
Semi-retired electronics / computer / network / 2-way-radio / ham radio... (WA6ILQ)
1985 Fleetwood 32' Southwind, dubbed "Lazarus" by friends... I resurrected it from the dead...
AnotherMike is offline   Reply With Quote
Old 02-12-2019, 11:35 AM   #60
Senior Member
 
Hangfive's Avatar
 
Vintage RV Owners Club
Ford Super Duty Owner
Rexhall Owners Group
Join Date: Nov 2014
Posts: 199
My motorhome has a switch on the momentary switch on the dash for employing the house battery to start the engine should the chassis battery go dead. Two seperated charging systems as the chassis and house batteries have unique charging parameters. You can charge them however you like, but you will be replacing the house batteries on a yearly basis. My money says RV mfg don't care, you come in complaining of dead batteries, they will check out your system, find nothing wrong, you buy some more batteries, come back a year later and do it all over again. LOL
Hangfive is offline   Reply With Quote
Old 02-13-2019, 08:23 AM   #61
Senior Member
 
Join Date: May 2017
Posts: 255
Quote:
Originally Posted by Persistent View Post
The original question was about TT's, not RV's. We know that most TT's get some charging current from the tow vehicle. A very few deliver enough 12 power to fast charge a bank of house batteries.
I am still standing on my premise that power (current in electronic terms) is not the issue. The problem is VOLTAGE at the TT batteries while the tow vehicle is running down the road. Checking the voltage at the TT batteries shortly after an engine start or at idle is not valid !

Quote:
Originally Posted by Persistent View Post
Certainly, high draw appliances in the TT require exceptional tow vehicle alternators, exceptional connecting cables, and exceptional electronic power management to both maintain a battery bank and supply the high draw appliances.
A better way of stating this would be, is the tow vehicle charging system, including wiring, and the TT wiring to the battery and high draw appliances (inverter) capable of providing >13.2V. If NOT, the TT batteries are NOT gaining any charge. Even if a reasonable TT battery bank (two 6V golf cart batteries) was drawn down to 50% SOC and it is receiving 13.5V do not expect them to be 100% SOC after 8 hours od highway driving.

Quote:
Originally Posted by Persistent View Post
Almost all use tow vehicle charging, but do not depend on it to provide charging to house batteries.
Not without a DC-DC charger in the TT !
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
theoldwizard is offline   Reply With Quote
Old 02-16-2019, 07:03 PM   #62
Junior Member
 
Join Date: May 2018
Posts: 9
Do It Yourself DC-DC booster

TT batteries typically need higher charge voltages than starter batteries. My 4Runner starts high and quickly drops down to 13.2-13.4v. Then subtract the line loss, and it's just a trickle.

I did not want to beef up new 4Runners wiring for so little gain. Instead I added a DC-DC converter to the TT. Output is 13.8v at 15amp, weather sealed with heat sink. It's enough to top off and not to much to be risky.

It is a Chinese brand from Amazon. With all the protection specs I wanted. As an experienced tech, I'm not very trusting.

This additional protection hardware is crucial. 30amp fuses on both ends. 15 amp auto reset fuse on DC output to limit overheating. 30amp relay to isolate output from TT when Tow (input) has no power (to coil). Diodes to squash coil kick back.

It's been working good for a year now.
Pappion is offline   Reply With Quote
Old 02-16-2019, 07:34 PM   #63
Junior Member
 
Join Date: May 2018
Posts: 9
Tow to TT DC Boost from AC Work Around.

This AC mod was considered, but dismissed. My Chalet 1930 internal Parallax DC supply is not a charger. Voltage was a low 13.6v.
Note: I later found a pot to adjust. Then I went tech crazy and added another pot and timer button for 2 hours at 14.2v. The secret dies with me. It's better than you dying.
The idea was to cut, yes cut, the Tow charge line in the TT and feed it to an inverter. That inverter would supply the TT charger. I knew 400W was enough as my 4Runner has a built in inverter, which I used when the sun don't shine. Safety is a big issue with 110vac. I was pricing generator switch relays etc..., I can't allow the 100v plug to be hot!
Pappion is offline   Reply With Quote
Old 02-17-2019, 08:53 AM   #64
Senior Member
 
Join Date: Nov 2018
Location: Beaver Dam, Wisconsin
Posts: 296
Quote:
Originally Posted by Pappion View Post
TT batteries typically need higher charge voltages than starter batteries. My 4Runner starts high and quickly drops down to 13.2-13.4v. Then subtract the line loss, and it's just a trickle.

I did not want to beef up new 4Runners wiring for so little gain. Instead I added a DC-DC converter to the TT. Output is 13.8v at 15amp, weather sealed with heat sink. It's enough to top off and not to much to be risky.

It is a Chinese brand from Amazon. With all the protection specs I wanted. As an experienced tech, I'm not very trusting.

This additional protection hardware is crucial. 30amp fuses on both ends. 15 amp auto reset fuse on DC output to limit overheating. 30amp relay to isolate output from TT when Tow (input) has no power (to coil). Diodes to squash coil kick back.

It's been working good for a year now.
This sounds like a solid design. Can you post model and manufacturer for:
DC-DC chg'er
30 amp relay
Diodes

Where did you tap into TV 12 volts, before after 7 pin connector, before after TT self resetting breaker?

Where does the TT emergency break tap fit in?

Where exactly did you put the diodes and in which direction?

Maybe a wiring diagram for all these front end components?
__________________
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
Persistent is offline   Reply With Quote
Old 02-17-2019, 12:49 PM   #65
Senior Member
 
Gulf Streamers Club
Ford Super Duty Owner
Join Date: Aug 2015
Location: Memphis, TN
Posts: 623
Quote:
Originally Posted by Lstyles View Post
In an RV you can easily use your alternator to charge the batteries as the wire run would be short. However, it would seem to be much more difficult to use the Tow vehicle alternator to charge a travel trailer. I understand that you might get some trickle charge across the wiring harness set up for trailer lights but the gauge would be way too small to get much. Do people fashion thick gauge wire/cable across the hitch point to try and charge the trailer battery? It seems like that would be risky.
Thoughts?
Typical B+ on 7-wire is (12ga PER ETRAILERdotcom) or 10ga, and 20-30a is MORE than sufficient for charging; further TRICKLE CHARGE voltages from your alternator come AFTER it senses that the LOAD is down and (battery charge is UP). THAT IS THE function of the voltage REGULATOR :-)
__________________
99-GS Conquest Limited 6266 Class-C
THenne1713 is offline   Reply With Quote
Old 02-17-2019, 03:43 PM   #66
Junior Member
 
Join Date: Dec 2018
Location: Baraboo, Wi
Posts: 16
I installed a system exactly like heatherdawnc described. So far it works very well. It also includes a circuit breaker, battery isolator, 6 ga wire all the way to the back of the truck, Anderson powerpole connectors to connect to the trailer, 6 ga wire from connector to circuit breaker, to battery.
I will be checking my batteries frequently on our first trip.
__________________
Bob and Dawn married 31 years.
2011 Ford F150 4X4 3.5l EcoBoost Supercrew Max Tow
2017 Viking 17FQ
BarabooBob is offline   Reply With Quote
Old 02-17-2019, 11:45 PM   #67
Junior Member
 
Join Date: May 2018
Posts: 9
Quote:
Originally Posted by Persistent View Post
This sounds like a solid design. Can you post model and manufacturer for:
DC-DC chg'er
30 amp relay
Diodes

Where did you tap into TV 12 volts, before after 7 pin connector, before after TT self resetting breaker?

Where does the TT emergency break tap fit in?

Where exactly did you put the diodes and in which direction?

Maybe a wiring diagram for all these front end components?
OK 1st things 1st. The 7 pin tow connectors Battery Power line in the TT must be cut. The DC-DC Circuity is inserted there. The rest of TT 12v wiring is not touched, including break-away switch.

I used 30amp automotive ATC blade fuses on both ends, input and output. Bought a pack of 10 with water resistant sockets and 12ga wire.on Amazon. I don't trust electronics, they tend to short out HARD when they fail.

The Bussman ATC 15amp Auto Reset circuit breaker fits in the same socket. It is inline with the DC-DC converters output and connects to the relay contacts (C).

The 30 Amp automotive relays other contact (N.O.) connects to 30amp fuse, which connects to TT 12v Battery.
The relays coil is connected to fused 7 pin power and ground. So is diode, with band to +12.
DC-DC module has 4 wires. 2 grounds, just ground them good. 1 input to fused 7 pin power. 1 output to 15amp CB.
Parts:
DC-DC Back in stock. 207W, 13.8v output, 15amp output, 9-14v input. Protections: Input transient, overheating, output current, output short circuit. https://www.amazon.com/DC-DC-convert...st%2Caps%2C282
Relay: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Fuses: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
CB: http://https://www.amazon.com/Bussma...s%2C242&sr=8-9
Diode: Used a diode bridge from junk box. A 1n4001 would do.
Project box: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I'm still searching for the hand drawn schematic. I shreaded a lot before moving.
Pappion is offline   Reply With Quote
Old 02-19-2019, 06:27 AM   #68
Senior Member
 
Join Date: May 2017
Posts: 255
Quote:
Originally Posted by Pappion View Post
OK 1st things 1st. The 7 pin tow connectors Battery Power line in the TT must be cut. The DC-DC Circuity is inserted there. The rest of TT 12v wiring is not touched, including break-away switch.
You do not have to install this setup outside, on the tongue, but it does need to be installed before the house batteries or any other "taps".

Quote:
Originally Posted by Pappion View Post
DC-DC Back in stock. 207W, 13.8v output, 15amp output, 9-14v input. Protections: Input transient, overheating, output current, output short circuit.
13.8V and only 15A is a bit "weak" in my opinion, especially if you are trying to recharge two 6V GC2 battery house bank that is at 50% SOC.

You can find 600W (about 40A) DC-DC power supplies (called "boost" or "buck/boost" power supplies) on eBay for very reasonable price. These are "bare boards", so they definitely need a housing. I would also include a fan on the housing (which means they really must be mounted INSIDE the TT). The bonus is that many of these have programmable output voltage and current with a display.
__________________
Retired. 31 year of automotive engineering for one of the Detroit 3, specializing in Powertrain Control Systems.
theoldwizard is offline   Reply With Quote
Old 02-19-2019, 10:58 AM   #69
Junior Member
 
Join Date: Feb 2019
Posts: 1
Quote:
Originally Posted by Lstyles View Post
Thanks for all the info. Things are as I suspected....limited. Can you tell me if these DC - DC chargers will work with a lithium battery? When I looked at them they seem to be focused on pb batteries.

I have a Redarc multi-stage DC-DC charger on the TT and it will charge Li batteries. I used the Redarc relay with 6awg along the chassis with Anderson PP connectors to the TT. A Victron 712 battery monitor with bluetooth allows me to see charging status as I travel. System works very well for me.
denverduc is offline   Reply With Quote
Old 02-20-2019, 12:24 AM   #70
Junior Member
 
Join Date: May 2018
Posts: 9
Quote:
Originally Posted by theoldwizard View Post

13.8V and only 15A is a bit "weak" in my opinion, especially if you are trying to recharge two 6V GC2 battery house bank that is at 50% SOC...

...You can find 600W (about 40A) DC-DC power supplies (called "boost" or "buck/boost" power supplies) on eBay for very reasonable price.

It's a good bang for the $50 to $75 bucks.
15A is just fine for me. Two size 27 Flooded and later 2 size 27 AGM Outback Nano-Carbon. Generally the Flooded are slow to charge. Meaning they take in less amperage. No issues with my new AGM either. 13.8 is a high float voltage. I am not building a multi phase battery charger. Just want more voltage than my Tow provides.

Do the math, starting backwards from output. 13.8v at 15A is 207W. At 93% efficiency its 221.5W from the Tow vehicle. The current would be about: 17A at 13V, 17.7A at 12.5V, 18.5A at 12v.

I'd buy a similar 20A DC-DC if they had it. 25A may blow Tow fuses.
My Tow is fused for 30A. I would have to rewire my TOW for 40A output. Which might need 60A wiring.

If I wanted to do better I would spend hundreds on a real battery charger.
__________________

Pappion is offline   Reply With Quote
Reply

Tags
alternator, batteries, trailer, travel, travel trailer



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dual Alternator Truck to charge TC batteries cjweener1 Truck Camper Discussion 13 04-07-2017 11:04 PM
Where do you park/store your travel trailer when not in use? SailorDon Travel Trailer Discussion 32 08-23-2015 10:04 AM
House Batteries Do Not Charge from Alternator BandBRetired Freightliner Motorhome Chassis Forum 10 09-03-2014 01:28 PM
Alternator Won't Charge Coach Batteries Captain Morgan Fleetwood Products Owner's Forum 2 12-16-2008 01:13 PM
alternator won't charge house batteries vacation on wheels Workhorse and Chevrolet Chassis Motorhome Forum 11 01-08-2007 12:55 PM

» Featured Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 01:51 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.