Using engine battery to recharge camper battery while driving

[Sunlanders-86]

I found a Pathfinder 100 on craigslist for $100. Solid combiner for an 86 Sunland Express?

I recently bought my Toy and aside from a little wiring and lighting i've been researching battery options. Just wanted to make sure this would be a good option for a couple of 12V, true deep cycle batteries running in parallel. I'm of the understanding that a 3 or even 4 stage charger is the best way to get life out of your batteries. But i read this:

Yes, as I stated at the outset - such a thing exists but is very pricey. A simple $15 isolation relay works well enough and is much simpler and cheaper. True that an automotive alternator cannot properly charge a deep cycle battery -but what it CAN do is good enough for most uses. When you use a rectifier isolator or a relay isolator - the fact remains that the deep cycle battery will only get 95% charged. Not a huge issue. When not traveling or camping - just plug it into a small charger designed for it. I only posted the battery-to-battery charger to illustrate its existence. I'd never bother with in any of my RVs. I've got RV batteries near 10 years old so obviously my camping trips using the alternator to charge them on the road hasn't hurt anything. I am NOT a fan of rectifier-base isolators either. There is always a voltage drop across them. You get NO drop with a relay.

and it tells me that a continuous bulk charge followed by the eventual trickle charge wont really effect the battery life by a significant amount.

I guess the question is do you recommend this C.L. combiner, or a relay as well as a stand alone A/C trickle charger?

Thanks for your time guys.

[Maineah]

I think this is the one your looking at http://www.yandina.com/c100InfoR3.htm if so you should buy from them on sale for $64.95! Yes that is a standard combiner or smart relay. There is nothing special with that device beyond being a combiner it does allow your alternator to charge the truck battery first before combining with the coach battery(ies) and drops out when the coach batteries voltage falls to 12.6 volts. I did not take a real good look but I would say it is also bidirectional meaning if you are using a charger it will combine and charge the truck battery also. I use a combiner to charge both coach batteries and have never had any issues. It is better then a standard relay but there is no magic it's just a smart switch it most likely has a bypass that would allow you to boost your truck battery if it's low with the coach batteries also. You can use a battery tender if the MH sits for a good while it will keep the batteries from freezing, fully charged doubtful and with a combiner the coil draws power when it combines so a 1 amp tender won't cut it. But with out a doubt the best up grade you can do is a modern 3 stage charger/converter they can be had for less then $200 for a 45 amp unit.

[zero]

I found a Pathfinder 100 on craigslist for $100. Solid combiner for an 86 Sunland Express?

I recently bought my Toy and aside from a little wiring and lighting I've been researching battery options. Just wanted to make sure this would be a good option for a couple of 12V, true deep cycle batteries running in parallel. I'm of the understanding that a 3 or even 4 stage charger is the best way to get life out of your batteries. But i read this:

and it tells me that a continuous bulk charge followed by the eventual trickle charge wont really effect the battery life by a significant amount.

I guess the question is do you recommend this C.L. combiner, or a relay as well as a stand alone A/C trickle charger?

Thanks for your time guys.

I prefer a relay. Not because it does a better job. More because it's cheaper and works just as well when used correctly. The only slight drawback to a simple low-draw relay is this situation. You've used your "house" battery night. Come morning you go to start your engine. The instant the ignition key hits "on" the relay connects your cranking battery to your "house' battery. So immediately, your cranking battery is sending charge power to your "house" battery . . . even before the engine starts. Usually not a problem but - having a simple $3 "on-off" cut-out switch works well in this situation. After a night of camping and you go to start in the morning - flip the switch to "off", start the engine, let it charge the cranking battery back up, and then - flip to "on" so the "house" battery gets charged.

The alternator in the truck is not capable of thoroughly charging a deep cycle battery. It will bring it to 90-95% charge and that's no big problem. Just shortens battery life in the long run unless the RV battery gets brought up to full charge once in awhile. That's one reason why you should have a good AC powered battery maintainer when grid power is available. Both for the RV battery and the cranking battery. All lead-acid batteries self-discharge when sitting. The rate they go dead on their own varies from 5% to 10% per month. To make things worse, newer trucks with computers constantly draw a small amount of power 24 hours a day. That brings the discharge rate up to 20% per month or some newer trucks and cars. So, unless you drive your camper every week, it ought to have a maintainer hooked to both batteries. A $25 two-amp 3 or 4 stage maintainer won't handle two batteries very long. Too small. Maintainers must reach around 14 volts before the fall into a float/maintain mode. 2 amps is not enough to do that on a large battery or two smaller ones. Especially as they age. A separate 2 amp maintainer on each battery will work, or . . . I prefer to use a dual output 5 amp total maintainer. It charges the cranking battery and RV battery separately but can divert a full 5 amps to either when needed. Mine is a marine model made by Guest. After having many small 2 amp chargers go bad - or fail to shut off, I changed over the Guest and now have several. They work great! Even on my diesel RV that has two cranking batteries and two deep-cycle "house" batteries. Some of my batteries are approaching 10 years old so I know I must be doing something right. After having many 1.5 and 2 amp maintainers fail in less then a year I research what boaters were using . . . since many bigger boats are just floating RVs with cranking and house batteries. Guest was pretty much the #1 choice when I checked for reliability. I'm not sure they still make the dual-output 5 amp model. I think it's now a 10 amp dual output at pretty much the same price. $100-$110 if you shop around and well worth it. Guest model 2610A.

http://www.islandmar...anks_p_195.html

Other makes:

Dual Pro RS2, dual output with 12 amps total:

http://www.islandmar...er-_p_1663.html

Minn Kota MK-210P dual output with a total of 10 amps:

http://www.islandmar...er-_p_1663.html

[stamar]

ya the isolation relay really doesnt work lol.

the instance you are describing happened to me in my 79 dolphin a few times because it came with a bad coach battery.

after a few jumps the starter battery died and i had to replace it.

the batteries are not isolated from eachother. they are temporarily seperated... then they are directly attached.

In a perfect world youre not draining your coach battery to zero for any reason in the first place.

and batteries exploding in toyhomes is too common, or in any camper van with the exact same set up. what happens is the driver battery is dead, and then they jump it whcih then kicks in the coach battery for too many amps too one battery.

all things considered what it does good, which is make sure the starting battery has a chance if you mess up the coach battery....isnt a lot different than what it does bad.

It prevents the regular use of the starting battery for lights and stereo lets say, and draining it down more than it should for your electrical but it doesnt guarantee a start like a real isolater does.

its something used to extend battery life and it probably does more so than if it wasnt there but im sure it loses compared to a real isolator.

depending on usage.

[kayakthecoast]

I put in a marine battery relay between my batteries with a manual switch on my dash, it can be set to automatic or manual. When boon docking I isolate the starter battery from the coach. When driving I combine them both for the alternator to charge both.

http://www.bluesea.com/products/category/Remote_Battery_Switches/ML-Remote_Battery_Switches/featured

You do want to make sure what your altenator output is. If it's a stock altenator it's probably around 40 amps, you can get new ones that double the output! I have a 100amp and charging my batteries takes half the time it used to.

[DanAatTheCape]

I have a 93 winnie warrior - my house battery is installed with the positive terminal outside - closest to compartment door. I can hook my standard jumper cables end to end making one long cable that will reach from that + terminal on the cabin battery to + terminal on the engine start battery.

Not fancy but could be useful. I had a cabin battery going out a few years ago while my generator was dead & I was taking power the other way. At the time I was in seawall cg at Arcadia NP so there where plenty of people around to jump me if I killed the start battery. Went to Ellsworth Walmart & got a trolling battery to use for my cabin - improved quality of life significantly. When I got home I got a Honda 2000 - life improved a lot more..

[Nam]

I thought of doing exactly the same...by adding a small 120VAC coil relay that automatically connects to the cab's battery whenever I plug the AC in so I don't have to worry about forgetting to flip the SW, in turn could drain my cab's battery then I can't start the engine.

When I find time, this is next on the list.

Connecting your coach battery to your truck battery is easy, just turn on your ignition. :-)

I've been considering installing a bypass switch on my dash. This would allow me to connect the two batteries together thru a 15 or 20 amp fuse or breaker. This switch isn't to be used for starting, but to be used for keeping the truck battery charged while plugged into shore power for long periods of time (weeks/months)

John Mc
88 Dolphin 4 Auto

[Nam]

I am second on the Honda EU2000i. It even runs my Jack Hammer!

I have a 93 winnie warrior - my house battery is installed with the positive terminal outside - closest to compartment door. I can hook my standard jumper cables end to end making one long cable that will reach from that + terminal on the cabin battery to + terminal on the engine start battery.

Not fancy but could be useful. I had a cabin battery going out a few years ago while my generator was dead & I was taking power the other way. At the time I was in seawall cg at Arcadia NP so there where plenty of people around to jump me if I killed the start battery. Went to Ellsworth Walmart & got a trolling battery to use for my cabin - improved quality of life significantly. When I got home I got a Honda 2000 - life improved a lot more..

[Nam]

I wish they make higher output alternator for V6. My stock one (60A) I think actually runs my mini refrigerator thru the 1000W inverter while driving...but higher output would work better

I put in a marine battery relay between my batteries with a manual switch on my dash, it can be set to automatic or manual. When boon docking I isolate the starter battery from the coach. When driving I combine them both for the alternator to charge both.
http://www.bluesea.com/products/category/Remote_Battery_Switches/ML-Remote_Battery_Switches/featured
You do want to make sure what your altenator output is. If it's a stock altenator it's probably around 40 amps, you can get new ones that double the output! I have a 100amp and charging my batteries takes half the time it used to.

[Pete1122]

Interesting that you mentioned the alternator, I found that running my fridge through my 1000 watt pure sine inverter while driving was actually a losing battle for my alternator. It couldn't keep up with the draw and would drain my batteries.

[zero]

Interesting that you mentioned the alternator, I found that running my fridge through my 1000 watt pure sine inverter while driving was actually a losing battle for my alternator. It couldn't keep up with the draw and would drain my batteries.

Shouldn't be a problem. Not unless something is wrong with your setup. I've been running a 5 cubic foot Samsung AC refrigerator for years in a 4WD RV I have with a 60 amp alternator. Runs off an AIMs 1200 watt modified-wave el-cheapo inverter. Also works fine off a Harbor Freight 2000 watt mod-wave inverter I got for $99. Draws 12 amps when running @ 12 volts DC (RV engine not running). Draws 11 amps @ 14 volts DC when the RV engine is running and alternator charging. A stock 60 amp alternator puts out 30 amps at engine idle speed. Having a "pure sine wave" inverter might make it work better or might make it work worse. It's a crap shoot and varies by brand and model. None of the smaller ones make a real sine wave. All have steps that simulate - but some do a better job then others. What is the current draw on your setup? What is the original watt rating on the refrigerator? Most of the small ones I've seen are rated 120 watts.