daveandmary Posted January 14, 2015 Report Share Posted January 14, 2015 I have an Alpenlite 5er that has 6 house batteries and an inverter, no jenny. The 7 pin plug carries 12 volts from my pickup to the 5er. Both the cord end and plug in socket show 12 volts on same pin. Is driving and towing supposed to recharge the house batteries? Doesn't seem to. Comments? Thanks, Dave Link to comment Share on other sites More sharing options...
trailertraveler Posted January 14, 2015 Report Share Posted January 14, 2015 ...The 7 pin plug carries 12 volts from my pickup to the 5er...Both the cord end and plug in socket show 12 volts on same pin...Is driving and towing supposed to recharge the house batteries?... In theory yes, but in practical application, the too small gauge of the wire and the length of the wire run often results in very little charging if any of the trailer batteries. Link to comment Share on other sites More sharing options...
Guest Pensauncola Posted January 14, 2015 Report Share Posted January 14, 2015 One way to determine this is to put a voltmeter on your house batteries and see what voltage you're getting before connecting the tow vehicle. Then, connect the tow vehicle and have someone rev the engine up to about 1800 rpm's (if diesel engine). If your voltage doesn't go up to at least 13 volts at the house batteries, it's not going to charge them. Link to comment Share on other sites More sharing options...
Kirk W Posted January 14, 2015 Report Share Posted January 14, 2015 Good answers thus far. One problem is that wire size limits current flow just as the diameter of a hose will limit the water that can flow through that. Even with perfect connections if the wire is not large enough it will not be able to supply enough to recharge a large battery bank in an RV in the typical travel time. It might get if done if you towed long enough, but that could mean more than one day. Most RVs have more than one battery, usually at least two and four is quite common. Your tow truck probably has the standard alternator as well and it too has a limited capacity to supply charge current to get the job done in a typical day's drive. While the theory is that the 12V supply through the connector plug will recharge the RV batteries, it really has not changed a great deal since RVs went from typically having only one battery to those of today with 4 or more. Thus if buying a tow truck it is important to also consider what alternator it has first. The chassis battery must be charged first and only the excess capacity of that alternator is available to the RV batteries. Good travelin !...............KirkFull-time 11+ years...... Now seasonal travelers.Kirk & Pam's Great RV Adventure Link to comment Share on other sites More sharing options...
SIBERNUT Posted January 14, 2015 Report Share Posted January 14, 2015 Be sure you have an isolator (or disconnect when you are at a CG). If not, fiver can DIS-charge TV, too. 2000 Volvo 635 A/S, N-14 Cummins"The Phoenix"'03 KA 38KSWB http://s918.photobucket.com/user/sibernut/library/?sort=6&page=1Furkids- Sibe's CH. Sedona & Tseika Link to comment Share on other sites More sharing options...
Rif Posted January 14, 2015 Report Share Posted January 14, 2015 I have an Alpenlite 5er that has 6 house batteries and an inverter, no jenny. The 7 pin plug carries 12 volts from my pickup to the 5er. Both the cord end and plug in socket show 12 volts on same pin. Is driving and towing supposed to recharge the house batteries? Doesn't seem to. Comments? Thanks, Dave The answers above are right on. There is now way you are going to charge 6 batteries through the 7 pin connector. But the thing I'm curious about is why there are 6 batteries and no way to charge them. Does this rig have a solar setup? Six batteries is a substantial battery bank. It is going to take a very good charger to maintain that many batteries. Is the inverter an inverter/charger by any chance? I'm just having a hard time understanding why someone would have 6 batteries with no way to charge them except for being plugged into shore power. Is there a residential refrigerator perhaps? 2000 Volvo 770, 500HP/1650FP Cummins N14 and 10 Speed Autoshift 3.58 Rear 202" WB, 2002 Teton Aspen Royal 43 Foot, Burgman 650 Scooter Link to comment Share on other sites More sharing options...
reed and elaine Posted January 14, 2015 Report Share Posted January 14, 2015 I believe that we got about 10 amps at 12 V (120 W) charging on our old system from the truck at road speeds A lot of folks have only one or two batteries and that connection probably helped quite a bit (we had a small TT at first) and a day's travel charged the two batteries fairly well. Sibernut (post #5) is absolutely correct. If the 7-pin is left connected, the house batteries will cheerfully charge the tow vehicle's batteries. The monitor for our battery bank showed the difference between being hooked up and disconnected and it was noticeable Our grandson used the 12 V power pin to run the rear view camera on the 5th wheel. This means we do not have to doing any hookup/detaching of the camera other than hooking into the 7-pin. It also means we don't charge at all from alternator but as Kirk noted in Post #4, that alternator would probably do nothing for our 9.6 kW-hr battery bank (and since the battery bank is a 48 V nominal bank - a 12 V input is improbable) Reed and Elaine Link to comment Share on other sites More sharing options...
skp51443 Posted January 14, 2015 Report Share Posted January 14, 2015 You can run a pair of heavy wires from the alternator and block ground point (gets the most possible power) back to the fiver's batteries. That will get you some level of charge but voltage losses in the wires cut the charging amps so you need fairly large wires to see many amps. The second issue is that your alternator is seeing both sets of batteries and if the chassis battery is well charged and has a lower resistance connection than the coach batteries the alternator may drop the output voltage thinking the batteries are fully charged. You can add battery switches so that the chassis battery is disconnected, that will usually improve the charging situation but comes at some risk, first overheating the alternator that is not designed to put out the rated amps for longer than it would take to charge the chassis battery, it may not be up to charging a bunch of coach batteries that are at a low state of charge. Second if your charging line disconnects you can find yourself with no battery power and have the engine die if the loads on it exceed the alternator's ability to provide power, think lights on and at idle. Don't skip good fuses on both ends of the battery connecting link! First rule of computer consulting: Sell a customer a Linux computer and you'll eat for a day. Sell a customer a Windows computer and you'll eat for a lifetime. Link to comment Share on other sites More sharing options...
oscarvan Posted January 14, 2015 Report Share Posted January 14, 2015 First and foremost...... Your camper battery or batteries are the power source for your breakaway system, and thus quite crucial. Therefore, any proper setup, and most are, will have the TV charging the camper batteries. That said, your bank sounds rather large, so even though the TV is charging it, it will take a while to bring it from a state of discharge to full charge. The suggestion to measure voltage is a very good one. It tells you that there is charging going on. But the amperage issue is a different one, and also correctly addressed above. My suggestion, especially with a large bank and your apparent dependency on it, is to install a condition monitor which will tell you exactly HOW MUCH charging is going on. You can control what you can measure. Previously a 2017 Forest River, Berkshire 38A, "The Dragonship". https://dragonship.blog/ Link to comment Share on other sites More sharing options...
Bob Cochran Posted January 15, 2015 Report Share Posted January 15, 2015 All the above is correct and great recommendations but I think one thing left out. If your batteries are all in good condition, fully charged and the drain is low during travel. The low amperage maybe sufficient to keep them charged until you get to your full hookup. Now if your boon-docking it will not be the case!!!!! 2019 Thor Chateau 28E on a Ford E450 chassis. Maybe awhile but will get a new picture forgive one up there it is my old rig. Link to comment Share on other sites More sharing options...
rdickinson Posted January 15, 2015 Report Share Posted January 15, 2015 I looked into this a couple of years ago. Bear in mind I am not that electrical savvy, but it goes something like this. Cetek make a device which takes power from the alternator and sends it to various battery banks needing charging..My truck is a 730, not sure if you are a HDT or pickup. I also have an inverter and 4 golf cart batteries. A different board is required in the inverter/charger and a solenoid somewhere. Sounds vague but I will make a call tomorrow. Some hefty cable would need to run to the back of the truck, perhaps same gauge from truck to battery bank, not sure. Forklift plugs were mentioned. Autowreckers use the same receptacles for jumper cables, they are grey. It seems between the smart device and the inverter they figure out which bank needs what power and either splits the charge or does one first then the other. A friend of mine is an electrical contractor and has a 44' Tollycraft, he said there is another device which goes on the battery terminal and senses when the batteries are or are not fully charged. If the alternator senses the batteries are charged and this device thinks otherwise, it tells the alternator to keep sending juice. I know this can be done. This is the general idea. If you like I can provide names and numbers to contact , one in Victoria and the other in Calgary. They could explain it a lot better. Prices are not that bad. Link to comment Share on other sites More sharing options...
daveandmary Posted January 17, 2015 Author Report Share Posted January 17, 2015 Thanks for all the replies and explanations. I understand that little if any measurable charging from the pickup to the RV can happen.\ Thot it would be nice if it did. Oh well! Thanks, Dave Link to comment Share on other sites More sharing options...
Kirk W Posted January 17, 2015 Report Share Posted January 17, 2015 I understand that little if any measurable charging from the pickup to the RV can happen.\ Thot it would be nice if it did. Oh well! There is some, but the amount is limited by both the wire size/length and the maximum output of the tow truck alternator. In theory it does charge but the amount available is small and the distance is great. In a standard configuration you would need to drive long distances and minimize electrical use. In the early days of RV travel it worked well because RVs had only a few electrical appliances and only one battery to supply them. With the smallest RVs having only one battery, it still works pretty well, but we have increased our power demands far beyond what the standard configuration can supply today. Good travelin !...............KirkFull-time 11+ years...... Now seasonal travelers.Kirk & Pam's Great RV Adventure Link to comment Share on other sites More sharing options...
Kiltedpig Posted January 19, 2015 Report Share Posted January 19, 2015 My Honda 2000 has a plug to charge batteries but I was wondering if battery charging would be better if I plugged my battery charger into the Honda and charged the batteries from the battery charger or does it make any difference. Link to comment Share on other sites More sharing options...
rdickinson Posted January 19, 2015 Report Share Posted January 19, 2015 I'm taking a wild guess it would depend on what the built in charger puts out as opposed to what a 110v charger plugged in can deliver. The built in charger on my 7kw diesel generator is not meant to charge up anything else other than its own battery about the size of a loaf of bread. Link to comment Share on other sites More sharing options...
Rif Posted January 19, 2015 Report Share Posted January 19, 2015 My Honda 2000 has a plug to charge batteries but I was wondering if battery charging would be better if I plugged my battery charger into the Honda and charged the batteries from the battery charger or does it make any difference. The built in 12V charger only puts out 8 amps. That's not much of a charge, especially when it doesn't say what voltage it puts out. There is precious little else in the way of specifications. You will be much better served by plugging in a good battery charger. If you are talking about charging the battery in your RV it might be best to just plug the RV into the Honda and let the built in converter or inverter do the charging. 2000 Volvo 770, 500HP/1650FP Cummins N14 and 10 Speed Autoshift 3.58 Rear 202" WB, 2002 Teton Aspen Royal 43 Foot, Burgman 650 Scooter Link to comment Share on other sites More sharing options...
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