TT batteries

[Grizzly]

Good question... I was wondering this too.



Although it should take minutes, charging through a 10ga wire might take a touch longer... I was wondering if anyone knew about how long.

I believe it would take much longer then that, but it all depends on the amperage output of the alternator on your truck. The alternator will first charge the two batteries on the truck before charging the RV batteries. Exactly how long, I don't know, it depends on how low the truck batteries are and how low the RV batteries are.

 

[steved]

I believe it would take much longer then that, but it all depends on the amperage output of the alternator on your truck. The alternator will first charge the two batteries on the truck before charging the RV batteries. Exactly how long, I don't know, it depends on how low the truck batteries are and how low the RV batteries are.

Think of how long it takes to charge a battery that's been jump started... not long. Its an amp/hour thing... we used to charge deep cycles (trolling motor batteries) with jumper cables in under 15 minutes.



The biggest "restriction" in charging a TT battery is the fact it is getting charged through a 10ga wire...

 

[Loren]

Thanks Loren,

It sounds then, that I have been doing the right thing all along. Maintaining a charge by keeping the trailer plugged into shore power. Since these are new batteries, and it hasnt been plugged in for a week, the smart thing to do would be to charge them with my battery charger, and then plug the trailer into the shore power and leave it.



Which brings up another question. When Im on the road, Im obviously charging the trailer batteries with the truck. Any idea on how long it would take to get a full charge that way ?



TRat

TRat,



Yes, lead-acid batteries like to be kept fully charged, but that's not the same thing as keeping them on a charger all the time. Most RV converters do not have circuitry to properly charge a battery, as has been mention above. Many will overcharge a battery, causing the water to "boil" away. It actually is an electrolysis process that converts the water to hydrogen (an explosive gas) and oxygen (a gas that aids explosions). That's why battery compartments are vented. Charging a battery creates hydrogen and oxygen.



Obviously, boiling away the water in your batteries is a bad thing, so it usually is not good to keep them charging with the converter. A good battery charger (and a top-quality RV converter) will monitor the battery's condition and eventually shut off or go into "float" mode when the battery is fully charged. Many RV converters don't do this.



What I do, which is not best for the batteries, is to remove them during the winter and keep them charged with occasional use of a battery charger. During the RV season, I usually leave the trailer plugged into shore power and leave the converter on, but I know that this is not the best procedure. If I were willing to do the work, the best thing would be to remove the batteries also during periods when we are not traveling. This would absolutely prevent any overcharging.



If you leave them charging in the RV with the converter, be sure to keep a close eye on the water level, assuming that you have batteries that allow you to do this. I use Optima batteries, and you can't check the water on an AGM battery.



There are LOTS of variables that determine how fast your RV batteries will charge when plugged into the truck. Some are: the truck's alternator capacity, how deeply discharged the RV batteries are, how deeply discharged the truck's batteries are, the guage of the wire that attaches the truck to the RV's batteries, and the quality of the connections.



Realize that when you plug your RV into the truck, you now have a four-battery system instead of two, two-battery systems. If the truck is not running and the RV is not plugged into shore power, the higher voltage batteries will immediately start charging the lower voltage batteries. If your RV is plugged into shore power, the RV's converter will charge all four batteries. If the truck is towing the RV, the truck's alternator will charge all four batteries. If you have no power source except for the batteries, it's possible for your RV power usage to drain the truck's batteries too. There are isolators available to prevent this, but if it's a concern, I will just unplug the truck. I then start the truck before plugging the trailer back in.



Here's an example of charging time: Your truck's batteries are fully charged. Your RV has not been connected to either shore power or the truck and the RV's batteries are 50% discharged. Your RV batteries are each 60 amp-hour batteries. In this case, when you plug into your trailer and start down the road, your truck will start charging the RV batteries. IF the RV batteries receive a 20 amp charge (that's a big IF) it will take about three hours to bring them back to a full charge.



Chances are that your RV batteries will not receive a 20 amp charge under the best of circumstances, so I would guess that it would take at least six hours to fully charge the RV batteries in the above case. Keep in mind that 20 amps is the rated maximum current for most 12 gauge wire. Your battery charging circuit should have 10 gauge wire (rated for 30 amps), but it will be rare for you to get this high a current.



There is voltage drop along the wire and at the connections, so the RV batteries aren't getting the full output of the truck's alternator, thereby increasing charging times even more.



The bottom line is that the best way to charge your batteries (any of them) is with a high-quality, sophisticated battery charger. The next best way is probably either the truck's alternator or the RV's converter, depending on the sophistication of those devices. In any case, the answer to, "How long will it take to charge my RV batteries?" is "It depends. "



In a worst case scenario, where the RV batteries are dead, it could easily take three or four hours with a high-quality battery charger at a 20 amp rate. Higher rates are not desireable because this creates heat. I charge my batteries at the lowest practical rate, which depends on how much time I have. With dead batteries and a charger set for a 4 amp rate, it can easily take over 24 hours to charge two batteries.



I hope this helps rather than confuses. Good luck,

Loren

 

[steved]

Chances are that your RV batteries will not receive a 20 amp charge under the best of circumstances, so I would guess that it would take at least six hours to fully charge the RV batteries in the above case. Keep in mind that 20 amps is the rated maximum current for most 12 gauge wire. Your battery charging circuit should have 10 gauge wire (rated for 30 amps), but it will be rare for you to get this high a current.

You make a good point...

I have a 15 amp fuse in my the power lead from the truck... it doesn't blow that fuse when charging (we ran the battery pretty good this past weekend), so that indicates they are receiving less than 15A.

I should note, the fuse is between the trailer to truck plug and the trailer wiring... not in the truck itself.

 

[Bob4x4]

That was a good explanation on truck charging rv batts Loren.



I am sure there are are companies that only ship with one batt but my Airstream and everyone on the lot came with 2.

The batt box is very convenient to access being on the tongue,the downside is I am limited to group 24 batts. The tt has a batt disconect and a 100 watt solar panel so it still works fairly well. I tryed leaving it connected to shore power but the batts did not live any longer. I still only get about 2 years of reliable batt service. Since most of our camping is boondocking I can't complain.



Bob

 

[steved]

I haven't even had the hatch open on mine as of yet... the door was screwed shut by the PO...

I intend on opening it this week at some point to see what kind of battery is even in there...

 

[Tractorat]

Loren,

Thank you for the information. I'm finding it to be extremely useful. I do have one more question though, and it sounds like you may be the person that might have the answer.



When I go to recharge the batteries with my regular battery charger, can I keep the betteries connected in parallel and charge them at the same time ? Oh, and one more thing. The batteries obviously are fully connected to the trailer circuits when traveling and being charged by the truck's alternator. So, is there any reason why I shouldn't just keep the trailer batteries connected on the trailer and just connect the charger to the batteries where they already sit and are still connected ? (I've always been under the impression that batteries (at least car batteries) should be disconnected from the circuit when you put them on the charger)



Thanks,

Mike

 

[AClayton]

Loren explained in detail what I was saying in a previous post. Many converters are not designed to charge a battery,only provide a DC source of reliable power while plugged in to shore power. They're are exceptions and only the higher-line trailers or motorhomes will have the converters that Loren mentions. I will also add that stranded wire of the same gauge will handle a few more amps ... about 5Amps... safely and without overloading a circuit. The #4 terminal is wired through the plug of our trucks with a #10 but,as mentioned by Loren,there are still too many variables to accurately tell how long it will take to charge. Length of wire and losses from bad connections in plug will ultimatley determine the final voltage actually getting to the RV battery.



As a sidenote... . I think more Rv'ers should concentrate just as much effort on their batteries as they do on trailer tires.

 

[AClayton]

Loren,

Thank you for the information. I'm finding it to be extremely useful. I do have one more question though, and it sounds like you may be the person that might have the answer.



When I go to recharge the batteries with my regular battery charger, can I keep the betteries connected in parallel and charge them at the same time ? Oh, and one more thing. The batteries obviously are fully connected to the trailer circuits when traveling and being charged by the truck's alternator. So, is there any reason why I shouldn't just keep the trailer batteries connected on the trailer and just connect the charger to the batteries where they already sit and are still connected ? (I've always been under the impression that batteries (at least car batteries) should be disconnected from the circuit when you put them on the charger)



Thanks,

Mike

I waited for Loren to answer..... he must be off-line. I'm sure he'll agree that both batteries are to be charged... . and load-tested , separately !! As Grizzly mentioned in an earlier post,If one battery is bad or reduced for some reason ,the bad battery will affect the good one's performance. I always disconnect from load while charging and understand that it is better to charge under lower amperage with more time to prevent over-heating of charger and battery. I'm sure Loren will chime in and give us a more informative answer... . he seems quite knowledgeable and explains much better than I do.

 

[Grizzly]

... ... ... .....



As a sidenote... . I think more Rv'ers should concentrate just as much effort on their batteries as they do on trailer tires.

I agree with what you are saying about the importance of RV batteries, however, from a safety standpoint, I believe that the highest concentration of efforts should be with RV tires and hitching.

 

[Loren]

When I go to recharge the batteries with my regular battery charger, can I keep the betteries connected in parallel and charge them at the same time ? Oh, and one more thing. The batteries obviously are fully connected to the trailer circuits when traveling and being charged by the truck's alternator. So, is there any reason why I shouldn't just keep the trailer batteries connected on the trailer and just connect the charger to the batteries where they already sit and are still connected ? (I've always been under the impression that batteries (at least car batteries) should be disconnected from the circuit when you put them on the charger)



Thanks,

Mike

Mike,



Actually this is one issue on which Alan (AClayton) and I disagree a bit. I consider the pair of batteries in our trucks as well as the pair in my RV to each be one large battery rather than two separate batteries. I charge them as a pair. Even when I take them out over the winter I keep them connected with jumpers, and when I charge them, I connect the charger to the pair.



Having said that, I know that one battery will fail before the other. When that happens it is difficult with my method to recognize it. It is also difficult to catch the failing battery before it starts to ruin the remaining battery. Charging each battery separately allows you to catch problems earlier than charging them together. I may change my method somewhat to occasionally charge them separately for just that reason. It makes sense, especially now that my batteries are getting older.



The bottom line is that I expect that either method will work.



As far as leaving the batteries in the trailer is concerned, I expect that that method would work fine as long as there isn't a large load on them. A load on the batteries could confuse the charger into thinking that there is something wrong with the batteries or that the batteries won't come up to a full charge. I charge my truck's batteries in the truck, but I close the hood (to turn the light off) when I do. I don't worry about the small remaining loads. The batteries seem to charge up just fine.



Another issue with charging them in the RV is the converter. You don't want to have two battery chargers (the converter and the charger) trying to charge the batteries at the same time. The charger, if it's a good one, will get confused and probably shut off too soon. I think that you can charge them in the RV as long as you keep the load low during charger and turn off the converter (or unplug shore power).



Last: Don't ascribe too much to my abilities. I have done a bit of reading about batteries and chargers, but I'm not an electrical engineer. (I think Rog (K5IP) is. Maybe he can help. ) I appreciate all the comments, but I'm not the final answer when it comes to batteries and chargers. I just have my opinions, just like the rest of us.



Loren

 

[AClayton]

Loren- You brung up a point that I failed to mention and that is to unplug from shorepower while charging... . or trailer cord while truck is running. You never have two charging sources at one time. This is very important!!

 

[AClayton]

[/I][/B]







I agree with what you are saying about the importance of RV batteries, however, from a safety standpoint, I believe that the highest concentration of efforts should be with RV tires and hitching.

You are right Grizzly... . you have to be able to get to the destination safely before worrying about your RV battery. I was simply suggesting that RV'ers should learn more about their RV electrical systems. Thanks - Alan

 

[K5IP]

Lots of good posts here guys.

As far as charging from the truck is concerned, I have traveled to Alaska for each of the last few summers. I use my single 97AH Interstate battery in the trailer to provide power to run an extra chest freezer (for Salmon) during the night so my trailer battery is nearly depleated each morning. Since I camp in forrest service or provincial parks, no shore power is available so I rely on the truck. The truck is able to provid about an 80% charge during a 6 hour driving day. I have incrreased the size of the charging line by installing an extra #6 wire with a resetable breaker.

Inrush on a depleted battery can exceed 40A and that will occasionally trip the breaker.

Sometimes practical experience helps.

Rog

 

[Gary - K7GLD]

Looks like the 12 volt systems covered in these threads relates to RV's with relatively few appliances/fixtures actually running off 12 volts, and also relatively few batteries active in the system.



On our '88 Kit 24 foot 5er, virtually EVERYTHING except the A/C and microwave operate on the 12 volt system, so battery condition and life are important! I started out with 2 6-volt Trojan 105 deep-cycle batteries in series, and they lasted 10 years, then seemed to not fully charge, or hold a charge, and after as much charge as I could get into them, could only get a bit over 10 volts measured at light fixtures under load at the far end of the trailer wiring. Some of the appliances, Ham gear and TV, etc, wouldn't even operate, due to low system voltage under load!



I replaced them with another brand of deep-cycle batteries - only to discover they did the same as the Trojans just replaced! Turns out, the problem was NOT the batteries, but the factory crimped-on connectors both at the batteries, and scattered in other parts of the trailer wiring. They had internal corrosion not visible from the outside, and provided too high a resistance to current flow.



I ended up cutting off ALL those connectors, and installing new ones that I soldered on - and gained nearly 2 volts at the far end of the trailer circuit! I then found that the original Trojans, charged by my larger charger in the shop, took and held a full charge just fine! I ended up giving them to my dad for his RV - and they functioned fine for another 3 years, until he sold it, and may STILL be in use... :-laf



I had always used a 10 amp shop charger, on a timer, to charge the batteries about an hour every day while the RV was parked at home - and eventually used a 2-amp solar panel to do the same thing, since the trailer usually sat at a distance from a power source to run the charger. I still use that same panel, and also have another larger 5-amp panel we take with us when camping to maintain the batteries, when shore power isn't available, and also have a Honda 2KW genset for the higher power 110 volt appliances.



Seems that if you use good batteries, keep them topped off with distilled water, and fully charged as much as possible, they'll last a long time - I got 10 years off the first set - and now have 10 years on this set, and still going strong!

 

[Grizzly]

Lots of good posts here guys.

As far as charging from the truck is concerned, I have traveled to Alaska for each of the last few summers. I use my single 97AH Interstate battery in the trailer to provide power to run an extra chest freezer (for Salmon) during the night so my trailer battery is nearly depleated each morning. Since I camp in forrest service or provincial parks, no shore power is available so I rely on the truck. The truck is able to provid about an 80% charge during a 6 hour driving day. I have incrreased the size of the charging line by installing an extra #6 wire with a resetable breaker.

Inrush on a depleted battery can exceed 40A and that will occasionally trip the breaker.

Sometimes practical experience helps.

Rog

You and I ought to get together and swap stories about Alaska, which is obviously yours and my favorite place to go. I'm in Albuquerque and I don't know where you are in New Mexico, which is a very large state.

 

[K5IP]

Grizzly,

I'am located in Los Alamos during the summer, but right now in Hawaii.

As a fellow Northwood (Nash) owner I am sure we could find something (hunting, fishing, diving, camping) to talk about.

.

Rog

 

[icman95]

I'd like to chime in on Gary's K7GLD comments about the 6 volt batteries. I've had this setup in my 5er for the last two years (since new) and love it. The dealer suggested to me to put 2 Interstate six volts wired in series in there for some serious power storage. What a great way to go. While I always try to conserve power and water while dry camping, I feel pretty confident that I have plenty of juice from this setup. I leave it on a set of 4 amp solar panels that keep them fresh while in storage. I just installed this same setup in my buddy's RV on Sunday. He had a tiny Napa deep cycle that came with it from the dealer and ran it dead last year a few times-his son playing video games powered by an inverter. Was easy to convince him to go with the 2- 6 volts for extra juice. Going dry camping with him on Memorial Day weekend-will see how they hold up. Can't recommend this setup enough if you have the room in your battery trays!

 

[Loren]

Many RVer's use 6 volt golf cart batteries for the "house batteries" in their RV's. The advantage is the huge capacity and the ability to discharge deeply without undue damage to the batteries.



I don't use 6-volt batteries because the RV is the only thing that would use them. My battery system is a rotation where the newest batteries go into the new truck. The old batteries (or battery, if one has failed) from the truck then move into whatever has the next highest priority. Currently that's the 1995 truck if both batteries are still good, or my wife's car, if I have just one good battery. The batteries from those vehicles move into the farm truck, or the tractor, or the sawmill, or the RV, depending upon how good the batteries are or what equipment needs one. The oldest batteries eventually wind up in the non-critical equipment. If the tractor, for example, won't start, I can always jump it because it's here. If my wife's car won't start, it may mean a trip for me to get her back on the road.



While 6-volt batteries would fill the bill very well in the RV, the remaining good one just wouldn't work in anything else when one of them fails.



In my case, with the Airstream, the batteries are installed in two separate compartments and the trailer is wired so that 12-volt batteries work. I would have to re-wire the connections if I wanted to use 6-volt batteries in series, and a real golf cart battery probably wouldn't fit in the space.



Loren

 

[Okie-Go]

WEll I got home last night and took the battery off the charger. Put it in the trailer and the jacks worked. Wifey was wondering why some of the lights did not come on when the light switch was on. I am glad it didn't appear that something was wrong with the trailer.