House battery for '95 RoadTrek

[Crank]

Greetings, I appreciated the wealth of information on this site as I prepared to buy a ’95 RoadTrek 190. Having pulled the trigger, I’m going to restrain myself and ask only about one subject at a time: coach batteries (all my aging brain will accommodate).

I should mention I am not new to RVing, having owned a tow camper for many years, during which time I have seen a few batteries destroy themselves (doubtless partly due to lack of informed care between uses; I now use a Battery Tender/4-step charger between trips: I guess I’ll need 2 of them for the B starting and house batteries). I admit I am not the kind of person who is likely to remember (find time, or bother with) checking something – fluid level - once a month (more like once a trip, maybe).

The RoadTrek came with one new 12v Interstate deep cycle/cranking hybrid: SPM-24, 550 CCA, 690 MCA battery; the cheapest they make). That gives me about 40 amp/hours before recharging, and so limits my boondocking options (although I do have a generator; I have not estimated my daily 12v power consumption yet). I may get rid of the Interstate and go to one or a pair of AGMs because of their efficiency and their tolerance of many of the problems that affect other battery technologies. One Lifeline 100 AH might do. Comments?

I have read quite a bit on recharging and care of batteries on the road and between trips (www.batteryminders.com is informative, but I remain pretty confused. Somewhere I read the Onan is slow to recharge the house battery: maybe that’s a function of the charger. I know next to nothing about my built-in RV charging system (no manual), but I’m willing to bet the rectifier/charger output has no temperature compensation, and I don’t know if it senses full charge and stops charging, especially if the same system charges the starting and deep cycle batteries. (I assume the system behaves the same way whether the charging source is the Onan or shore power). I have read that in general it is better to use a dedicated charger designed for an AGM house battery: any consensus on that?

The Interstate is housed in a small compartment INSIDE the coach under the bed – a nice spot for sulfation! An AGM would be OK inside, but I have not looked for a location for a second one because I don’t know the dimensions yet.

Thanks for any insights anyone may be able to offer. (I have craftily concealed several questions in this post).
Please remember - there are no dumb questions!

[markopolo]

Sounds like you've done your research and have a good idea as to what is involved.
Note: Battery Sulfation occurs from chronic undercharging.

Wet cell batteries can out gas when being charged. Does your battery compartment vent to the exterior of the van?
An upgraded converter / charger would be a nice improvement. Check the battery wire gauge size on your existing installation. That might limit your options if the wires are small size. Randy at Best Converter http://www.bestconverter.com/index.html would probably know if there is an easy upgrade for the converter that is in your van now. Make sure to give him the make / model of the converter / charger that you have now.

I have AGM batteries in my van. It's not ideal as it is still possible for them to out gas. It is less likely to happen though.

[olddodgevan]

A battery box vented to the outside would be a good idea.

[Davydd]

You could put a wet cell battery inside your van. You might want to enclose it in a box and you could vent it out the floor. They sell caps and vent tubes for batteries. This is an example of an auxiliary battery Mercedes Benz put under the passenger seat of a 2004 Sprinter. It is about a 1/4 inch plastic tube that sticks through a rubber grommet through the floor.

[Crank]

Thank you both for you comments and suggestions. It has been too hot here (100F by 9.00 am) for me to look into issues such as alternative battery locations, so I have being doing research instead on several issues. (I should have mentioned that my control/charger unit is a Magnetech PR 7298: I have not been able to find any on-line info for this model, only the 7100 and 7300 series.)

I agree if a flooded wet cell is in the coach, it has to be vented to the exterior, but if I switch to AGM, my impression is that outgassing is not a significant issue. (The primary reason for considering an AGM is the much higher effective capacity, and the fact they are more forgiving than the flooded wet cell type).

I believe (based on my reading) that batteries frequently never get fully recharged due to chargers that do not have a proper 4-stage charging profile, or do not have the correct set points for the charging mode changes and battery type. Some other factors are interaction with solar cells (which I don't aspire to) and undersized wiring, as you mentioned.

One other point I have run across is the importance of accurate battery monitoring, so one knows EXACTLY what is going on. The Trimeric 2025 is prized for this.

So it appears to me that 20 year old technology probably needs to be upgraded to get a properly functioning, dependable and long-lasting house battery system. That may be a fairly costly, but worthwhile investment. Unfortunately, while I might be able to determine what I need (with some advice), I am probably incapable of installing it correctly, and I don't know of anyone in this corner of New Mexico who can: maybe someone here knows someone competent in Albuquerque or El Paso.

I am thinking that with the Onan, a 1 battery AGM system, if managed properly, might be sufficient for two careful adults to dry camp until the tanks are empty (or full). What do you think?

In this boondocking context, can a barbecue-type propane tank be connected into the horizontal OEM tank system to provide supplemental fuel?

[booster]

(The primary reason for considering an AGM is the much higher effective capacity, and the fact they are more forgiving than the flooded wet cell type).

These are reasons that AGM salesman use, IMO, but all the real technical information that I have found would say that AGMs will have the same effective capacity (for the same 20 hr rating) as a wet cell. 50% of rated for longer life, 80% discharge maximum. Good wet cells will have a bit more rated capacity for a given case size compared to AGMs. The same is true for being more forgiving. The are actually a bit more likely to be damaged by long term high voltage, and will also lose capacity like wet cells if short cycled without getting totally full regularly. Not to say you shouldn't get AGM, as they have their plusses, just don't expect them to do all the things that the salesmen tell you.

[eric1514]

Talk to the folks here http://www.bestconverter.com/ to see if they can get you an upgrade kit for your Magnatek. I think if you had a good converter with a "smart" charger and conserved electricity, maybe install some LEDs, you should be fine for a day or two on one battery, provided you don't run the furnace. I don't think you need to spend extra for an AGM.

[Crank]

Randy at BestConverter does indeed have a good upgrade for my present converter/charger system (4-level charger), and lots of other useful advice. Probably I should install a Trimetric monitor so I always know the state of charge, unless you know a better way.

I can't find any exterior location to mount one or two batteries for the 95 RoadTrek 190 P. The interior one is not in a vented battery box, so I will probably go with AGM.

Many thanks for the valuable suggestions!

[mikgills]

I have a 95 RT210 and have done mostly what you are asking about. I added the trimetric monitor, the smart charger, extra batteries. works great. The original magnetek converter is junk. Charges so slowly you never get it charged up. the progressive fits in the magnetek metal case perfectly and all outputs are regulated. My single battery was under the bed. I just tore the compartment apart and made it bigger for 2 batteries side by side, using the original ventilation. I put both batteries in marine battery boxes, so no spills or weeping can come in contact with the metal floor. Converted to LED lights. My usage is now so low, I don't use the generator i installed! Only need it for air conditioner/microwave which I rarely use. What really made a difference is, i built a 150Amp HD alternator with 75A rated diodes. This really charges bulk charge fast. The rectifiers are external on a huge heat sink as the regulator. Has 4 times the mount of cooling fins and extra fan. Original 105A alternator will fry. Its only designed to top off a starting battery (10% or less) not charge 2 deep cycle deep discharged large batteries. The original 105A was garbage and would only put out 30A when hot (not 105A). Alternators loose their charging ability as they get hot, so go to a overly large that doesn't get that hot and you will have a decent charging system. I added the generator afterwards and found out i didn't need it. You can also get a smart regulator for the alternator.
Works perfectly. No worries with constantly depleted batteries when boon docking. Mike G mikgills@icloud.com

[Crank]

Thanks for a host of useful facts, Mikgills. I would like to request some additional details. (I have not proceeded with my electrical system upgrade because of other priorities, but it is now almost spring - and an old man's fancies...)

"What really made a difference is, I built a 150Amp HD alternator with 75A rated diodes."

It seems like a good idea, but I have no idea how to build such a thing, and would have to find someone with experience to do it. What kind of cost would I be looking at (excluding labor)?

You are obviously very happy with your system. But since I already have the Onan, I'm not sure if the cost is justified, considering I will also be buying a converter/charger, a Trimetric and batteries. Advantages are the redundancy and eliminating the Onan's noise, much greater than the Dodge engine).

Can you say where to get a suitable generator, (rebuilt perhaps?) and provide specifications and sources for the diodes and smart regulator/rectifiers?

Did you have to replace anything between alternator and charger, given the higher load?

What capacity are your batteries, and about how long does it take to recharge them, engine idling? Faster than the Onan? (The charge rate is limited by the stepped charging system of modern chargers, unless the Onan can't keep up with the demand).

[Crank]

I thought I should draw a line under this old thread.

The discussion continues in two later ones:

http://www.classbforum.com/forums/f8...se-b-3891.html

http://www.classbforum.com/forums/f8...mode-4100.html

It became clear in the next thread that the important question turned out to be not what battery to choose, but how to charge it correctly: a lot of key information was reviewed and a number of options were discussed, but a satisfactory solution was not reached.

I learned that my Magnetek 6300 series charger/converter was junk (it quickly killed my new battery because it did not limit charging time or power); the slide-in upgrades may be an improvement, but they do not charge batteries properly or completely either. After much discussion on this site, it became clear that none of the cheaper upgrades do an adequate job.

Both threads are full of interesting and valuable technical information, discussion of various trade-offs. etc. As a result, my expectations and requirements evolved.

The bottom line is that you can't have a really efficient charging system that will take care of your batteries without spending a little more.



I knew from the beginning I wanted AGM batteries, mainly because, being sealed, they don't leak and require monthly cleaning and topping up with water, which in my case is a pain to do because they are in a closet under the bed, and getting to them is getting harder with age, and because I know myself well enough to realize I will not keep to a monthly schedule. Their main downside is that you cannot measure their state of charge by measuring specific gravity: but there are other, more convenient means of determining it.


Eventually I decided to invest in a system: batteries, charger and monitor that would work efficiently together. The second thread cited above ends with a very good (but thankfully not the most expensive) solution.

Had I had solar cells installed, I might have arrived at a different solution. This continuing discussion generally assumes that solar collectors of significant size are not installed.

Crank