Should my chassis battery charge on shore power?

[Rocinante Sunrader 88]

I have an 88 Sunrader with what appears to be a solenoid-based isolator setup (little cylinder that looks like the old Ford starter solenoids, four wire).

My problem is that when it sits for weeks not being used, plugged into shore power, the chassis battery will be dead and I will have to jump start the vehicle. When I check voltages, running the engine charges both chassis and house batteries, but shore power charges only the house battery.

Is this how it is supposed to work? If so, is there a workaround so that shore power also charges truck battery while still maintaining isolation when disconnected?

If this is not how it is supposed to work, any suggestions on troubleshooting?

I should add that about two years ago I was having a problem with the chassis battery discharging overnight. I took it to an auto electric shop, which told me that my radio was discharging the battery, disconnected it, and told me that I needed a new isolator (identical in appearance to the solenoid-like one that I had had before.) The one that they sold me looked just like the old one and I hooked it up. I have since reconnected the radio and do not have the problem with the chassis battery discharging overnight, so I think that they were full of it on that, just finding the minimal current that keeps memory going in the radio. Long story short, I am pretty confident that the isolator, being pretty new, is not faulty, not to say that it is hooked up right.

[Derek up North]

The same way the isolator stops your coach from running down your chassis/cab battery while boondocking, it should/will also isolate the cab battery from you charger. If you often park for extended periods you could bypass the isolator while parked with a 'jumper'.

Your cab battery might also be getting near the end of it's life.

[zero]

4 hours ago, Rocinante Sunrader 88 said:

 

My problem is that when it sits for weeks not being used, plugged into shore power, the chassis battery will be dead and I will have to jump start the vehicle. When I check voltages, running the engine charges both chassis and house batteries, but shore power charges only the house battery.I

That's the way the isolator is supposed to work.  You either need to put a jumper wire on it when parked, or just buy a separate dual-output, isolated, marine-type battery charger. I have the latter in all my RVs.

All batteries self-discharge.  Depending on type and age, some lose 10% per month even if hooked to nothing. Then you have the added problem of phantom current draw that can be from a leaky diode in the alternator, the radio memory, alarm system, etc. Only way to know is check it with a milliamp meter.  You can buy one from Harbor Freight for $5.   80 milliamps of draw is about the max acceptable for an older vehicle like a Toyota RV when turn off and parked.  Many newer vehicles have even more draw when parked and will go dead in 30 days if not started up to recharge.   

[Bob C]

I have not had a problem with the starter battery discharging while sitting, but if I did, I would do as Derek suggests.  You could make a jumper out of a piece of wire and two open ended crimp on connectors.  Just loosen the nuts on the isolator for the wires that go to the batteries and slip the open ended connectors onto the post and retighten the nuts.  I don't think I would use alligator clips because one end may slip off and short out.  Just make sure that when you are using the RV, you remove the jumper so that you don't wake up and find that you coach has killed you starter battery.

[Totem]

beware jumping a solid state isolator... can ruin it.

[Rocinante Sunrader 88]

6 hours ago, jdemaris said:

That's the way the isolator is supposed to work.  You either need to put a jumper wire on it when parked, or just buy a separate dual-output, isolated, marine-type battery charger. I have the latter in all my RVs.

I am much more interested in the dual-output, isolated, marine type battery charger. What capacity do I need, and more or less what do they run? Also, I am assuming that for an 88 I need to run an exciter wire? Anything else specific that I need to know about hooking it up?

Thanks a lot!

[Rocinante Sunrader 88]

1 minute ago, Rocinante Sunrader 88 said:

I am much more interested in the dual-output, isolated, marine type battery charger. What capacity do I need, and more or less what do they run? Also, I am assuming that for an 88 I need to run an exciter wire? Anything else specific that I need to know about hooking it up?

Thanks a lot!

Also, I am guessing that I would want to hook that up back by the fridge where the electrical panel is? Do I then have to run a separate set of heavy gauge wires to the second battery?

[Rocinante Sunrader 88]

So if the shore power is not supposed to charge the chassis battery, I am wondering if I could just hook up a 110v relay in the engine compartment with a line from the electrical panel 110v circuit that would close to jump the two batteries whenever shore power was connected and then open again when shore power was disconnected. Has anyone tried that?

BTW, I assume that the chargers in these things have a trickle function so that they won't screw up the battereis if you are hooked up to shore power long term. Is that correct?

[Derek up North]

Or keep things simple and buy one of these:-

http://www.harborfreight.com/automatic-battery-float-charger-42292.html

[Derek up North]

But if you want nothing but the BEST:-

http://www.ebay.co.uk/itm/Brand-New-Genuine-Honda-Optimate-5-Battery-Charger-Optimiser-Conditioner-/170800835371

[Wade]

On 5/26/2016 at 6:18 PM, Derek up North said:

But if you want nothing but the BEST:-

http://www.ebay.co.uk/itm/Brand-New-Genuine-Honda-Optimate-5-Battery-Charger-Optimiser-Conditioner-/170800835371

Newbee question?

Given the number of Honda dissing posts, is this supposed to be sarcastic? Not sure of the differences between different battery chemistries but if the description is accurate could be a valid point for the crazy $. For LiOn and LiPO batteries at least charging profiles  are critical and common cheap chargers are anything but cheap!

Wade

[zero]

On 2016-05-26 at 6:27 PM, Rocinante Sunrader 88 said:

I am much more interested in the dual-output, isolated, marine type battery charger. What capacity do I need, and more or less what do they run? Also, I am assuming that for an 88 I need to run an exciter wire? Anything else specific that I need to know about hooking it up?

Thanks a lot!

You cannot buy a better setup then a dual-output charger.  Hardwire it in and that is that. When you park the RV, all batteries (coach and cranking) are maintained.  No relays to jump, no clips to stick on battery posts, no boiling batteries, etc.  Mine was $100 on sale when I got it.  $130 is more the norm.  Brand name used to be Guest and now it is Marinco.

[zero]

Here's a photo under the couch on my Minicruiser.  Guest dual charger hard-wired in.  When I put my RV in storage (parked, not camping) - I just plug it in and all three of my batteries are maintained.  Two in the coach and one under the hood.

[Maineah]

You can also replace the isolator with a combiner and use the charging system that is all ready there. http://www.littelfuse.com/smartbatteryisolators?utm_source=colehersee.com&utm_medium=redirect&utm_campaign=colehersee-lf

[zero]

Yes, but that means a relay having to be energized, all the time.  If it was a "latching" relay it would be different, but it is not.

[Maineah]

On 2016-06-18 at 9:30 AM, jdemaris said:

Yes, but that means a relay having to be energized, all the time.   If it was a "latching" relay it would be different, but it is not.

True but if it's plugged in who cares?

[DanAatTheCape]

I just disconnect the negative terminal on the start battery when it is going to sit for a while.  I drive the camper at least once a month.  I also run my generator every month.  When it runs, I use it to charge the start battery while it is running.

 

As for all the rigging to try to get the power converter to charge both batteries, I would shy away.   To much trouble - keep it simple.   KISS works for me.

[zero]

The fact remains that all lead-acid batteries "self-discharge" regardless if hooked to anything or not.  If a vehicle is driven once a month, then it is a non-issue. If a vehicle gets garaged (or barned) every winter, then it IS an issue.  5-10% discharge per month is common.  If a vehicle sits from Dec to June like mine - that means the battery gets low, sits that way, and that shortens the life of it.  My rig has three batteries.  So in my scheme of things - just unhooking and leaving would be foolish.  I used to have two cheap Duracell maintainers. I'd hook one to the rear bank (has two batteries) and one to the front cranking battery.  One problem with this sort of setup.  They are only rated 1.5 amps and that is just barely enough to maintain one large battery in good shape.  When hooked to a pair, it could not get to the 14 volt high-limit to shut itself off and ran all the time.   I have over 20 battery maintainers plugged in, all the time. On four vehicles that are parked for the summer and also many tractors, backhoes, dozers, etc. I see them as Godsends.  But with my Toyota RV?    Putting in the marine charger worked nicely. Has a 10 amp charge rate instead of 1.5 amps and keeps the house batteries totally isolated from the front cranking battery when charging.   If I had an on-board converter-charger and rigged it to charge all my batteries - that has all three connected in parallel when charging. Something I wish to avoid.  Yes, that IS what happens when I drive.  But the majority of the time my rig is parked and my pair of deep-cycle house batteries should not be connected in parallel to a dissimilar cranking battery long term.  Just my way of doing it. No right or wrong here.

[Maineah]

I leave mine on a 3 stage charger all winter if I didn't the batteries would last about 5 years if I do they last about 5 years.

[grandview bill]

a simple dash mounted switch to energize the solenoid when paralleling is needed is what I have,the stock system of paralleling the two dissimilar baterries  when the ignition is on ,shortened the coach battery life

[zero]

On 6/20/2016 at 10:39 AM, Maineah said:

I leave mine on a 3 stage charger all winter if I didn't the batteries would last about 5 years if I do they last about 5 years.

5 years either way for you?  Has not been my experience.  On a maintainer, I'm still using batteries that are 10 years old.  However, the old ones do not hold a charge very long. If left off a maintainer, they go dead in a week or two.  Still work fine in much of my equipment that sits in a barn most of the time. 

Battery life in anything depends much on it's voltage when sitting.  Many modern vehicles have a small but steady drain on the battery 24 hours a day and  with some, a new battery will go dead in 4-5 weeks if a car is not driven.  That sort of situation severely shortens battery life unless a maintainer is used.   

My 1988 Toyota has zero battery drain when parked, so the only battery-killer involved when it comes to storage is "self discharge" that any lead-acid battery has.  Average is around 5%-10% per month.  Does not sound like much but adds up for an RV that might be garaged 10 months a year.

Long story short - if you drive your RV every week or so, 12 months a year, a maintainer will likely offer no gain in battery life.  If your RV gets parked or stored much of the time, a maintainer is a must for best battery life.