Upgrade converter, add bat. bank & trimetric monitor

[Mgittrich]

Background:

The 93 MH is equipped with an Onan Microlite 2.8kw generator, Magnetek 6332 converter and a group 50 house battery as was delivered by Airstream in 93. The cable connecting the starting battery and the house battery has been removed.

There are many issues with this design which includes battery capacity and the ability of the Magnetek to properly charge and maintain AGM batteries. These have been well documented in this forum and a big thanks to all of you that contributed to this knowledge base. It has been most helpful.

My sofa needs to be reupholstered, part of my winter project list, and I figured now was a good time to do electrical upgrades while the sofa is out. So here's what I am thinking about doing. Any advise is greatly appreciated.

Electrical system upgrade goals:
1. add a 12v battery bank under the couch consisting of 2 Optima group 31 batteries in sealed battery boxes by Taylor Cable. I know I will probably need to loose or shorten the drawer under the couch to do this.

2. Upgrade the existing converter to a 55amp Ultra III with an upgrade kit from Bestconverter.com

3. Add a trimetric 2025rv to monitor the new battery bank

4. Add a battery switch to provide selective use of the existing group 50 and new battery bank

To help me get a handle on this I put together this diagram. Everything in dotted or dashed lines would be new as well as the battery selector switch and 100amp fuse to protect the new battery bank.

image.jpg (118.31 KiB) Viewed 12883 times

I'm hoping to have the group take a look at this design and recommend changes. I think this will work but wanted a second opinion before I embarked on this journey.

To add some sanity to this I will perform the upgrades in stages.

Stage 1 - upgrade the converter and verify that it is wired and working correctly. I will probably rough-in the battery selector switch, battery shunt and Trimetric placement and remote cable run.

Stage 2 - add the new battery bank. Attach to the selector switch, shunt and trimetric monitor.

My concerns:

The existing group 50 battery is about 2/3 the capacity of each batteries in the new battery bank and is not an AGM battery. Is this a problem?

Thermal protection. Is a 100 amp fuse the correct size for the new batter bank?

Do I need a breaker coming off the switch running to the converter?

Trimetric installation. I think the wiring is correct but I was hoping someone could verify that? I also think I could attach a fused wire running from the selector switch to the B2 terminal on the monitor to look at volts from the battery in the engine compartment. Has anyone done that?

I know this is a lot of questions and information to absorb. I appreciate any advice anyone has.

Thank you!

[skater]

I'm hoping to have the group take a look at this design and recommend changes. I think this will work but wanted a second opinion before I embarked on this journey.

I don't see any problems (I'm no expert, but this stuff is generally common sense, too).

The existing group 50 battery is about 2/3 the capacity of each batteries in the new battery bank and is not an AGM battery. Is this a problem?

If I understand correctly, you wouldn't be using that battery and the AGM batteries simultaneously - you'd be switching between them for charging and usage. If that's correct, then it shouldn't matter that they're different batteries.

Thermal protection. Is a 100 amp fuse the correct size for the new batter bank?

I think so. In this case - since it'd be next to impossible to draw that much power in a B190 - the fuse is really there for short-circuit protection. 100 amps might be too large; your max theoretical load is probably more like 20 or 30 amps. But as long as your wire can physically handle 100 amps of power (length and gauge considerations - there are plenty of charts on the internet to confirm this), the 100 amp fuse would be fine.

Do I need a breaker coming off the switch running to the converter?

The battery selector switch? I don't think so. The converter itself should have a 120 volt breaker on it, of course.

Trimetric installation. I think the wiring is correct but I was hoping someone could verify that? I also think I could attach a fused wire running from the selector switch to the B2 terminal on the monitor to look at volts from the battery in the engine compartment. Has anyone done that?

I don't have any experience with them.

Good luck!

[EricZ]

I have a somewhat similar setup in my 1993 Airstream 190:

- Three Odyssey PC2150 AGM batteries (100Ah each)
- A PROsine 2.0 inverter/charger (2000-watt inverter, 100-amp charger)
- A TriMetric 2025RV battery monitor

Here are some thoughts and questions:

- Rather than the Optima yellow-top group 31 batteries, take a look at the Odyssey products. I believe they are better batteries, and when purchased with a Sears Diehard Platinum Marine label (PM1 or PM2) they might even be less expensive, especially in dollars-per-amp-hour. (Note that the PM batteries regularly go on sale at Sears; I got my PM1's (relabeled Odyssey PC2150's) for about $200 each. These are exactly the same as the Odyssey-branded products.)

- The Optima D31 batteries look like they now have a 2-year warranty; the Sears PM's have a 3-year warranty. If you do use Optimas, take a look at the other sizes (such as the D34), some of which have a 3-year warranty. (I evaluate batteries largely in "dollars-per-amp-hour;" fewer larger batteries or more smaller batteries can still provide the capacity desired.)

- Despite locating my batteries indoors (under the couch, just as you describe) I didn't use battery boxes; AGM batteries (at least the Odyssey line) are approved for indoor use (even use inside airplanes!).

- Battery boxes or not, make sure the batteries are securely fastened down. Worst case, you want them to stay put in a roll-over accident, lest they short and cause a fire. I used metal brackets in the seat-belt mounting holes and nylon-web straps. I also placed thick vinyl tubing (slit lengthwise) over the metal cross bar under the couch to eliminate the metal bar so close to the batteries.

- Speaking of insulation, I think a much more significant risk then rollover is a metal object landing on top of the batteries. This could happen, for example, if such an object fell behind the couch. I thus carefully insulated all terminals (positive AND negative) and use a short, insulated wrench on the battery terminal nuts.

- I thought about leaving a house battery in the engine compartment space, but decided that it wasn't worth the bother. Yes, it seems nice to have the extra capacity and a backup power source, but I didn't think I'd really use it. And eliminating that battery also eliminates the battery selector switch.

- If you do leave a house battery in the engine compartment, you might not need the Blue Sea 2017 dual powerpost.

- On the other hand, you could probably fit an Optima group 31 in the passenger-side engine-compartment battery space. This is what I did before going to the internal Odyssey batteries. It took minor modification to the edge of the front cross bar (the radiator support), and was still awkward to install, but it did fit. (Note that this was only the Optima group 31. Other group 31 batteries would not fit.) By doing this you could:
- Go with just one Optima 31 (eliminating the indoor batteries entirely),
- or put one Optima 31 in the engine compartment and one under the couch,
- or have three Optima 31's (two under the couch and one in the engine compartment).
(Note that I did none of these things; they're just possibilities that might work for you.)

- I like having the house battery bank charge when the engine is running. I'd consider reconnecting the stock interconnect between your starting battery and your house bank. (I saw in another thread that you found an always-on connection between them when you got your vehicle, but -- at least on my vehicle -- that's not how it came from the factory. On mine the batteries are bridged only when the engine is running.)

- I completely removed the under-couch drawer (rather than shorten it, as you propose). I plan to use the drawer front to cover the opening (probably with snap catches, so it can be completely removed for access).

- I found it very easy to remove the couch bottom for access. I place the couch half way between "couch" and "bed," then remove four nuts from the bottom (two on each side). The cushion then simple lifts away. Reinstalling it is a little more awkward; you need to get the couch mechanism to stay in the in-between state. Probably easy with two people.

- The 60-amp and 100-amp breakers you plan are really there in case of short circuits. I'd thus likely increase each one a bit:
- The 60-amp is pretty close to your converter's 55-amp theoretical maximum output. If you were to power on the converter with the engine-compartment battery deeply discharged, you might briefly reach something close to that 55 amps. Similarly, if you turn the battery selector switch to "Both" you might get a significant surge. I'd consider something around 75 amps. (On the other hand, it is a breaker (rather than a fuse), so you COULD just reset it.)
- The 100-amp is actually not bad. My sense is that it should be a bit larger, but in your setup I really have no reason for that sense. (I use a 350-amp fuse because my inverter can easy pull 200+ amps, but you have no such loads.)
(Note: you mention "thermal protection," but these breakers are really overcurrent protection (even if they do use a thermal mechanism internally).)

I'll address the TriMetric in another post.

Eric.

[Mgittrich]

Skater and Eric thanks!

I greatly appreciate your thoughts and feedback. All things to consider. I'll definitely look at the different batteries you mentioned. I like the idea of using the seatbelt holes as tie downs. They were coming out anyway and this is a good use for them. The batteries certainly wouldn't move around even in a crash.

I like you am concerned about accidental shorts from things falling through the couch so I will definitely pay close attention to this. This is one of the reasons I'm leaning toward battery boxes. The other thing is the potential or battery off gassing even in AGM batteries. From what I have read this looks to be a minimal concern with the Optima's but I will continue to research. I saw another thread where some body had vented the battery boxes out through the generator compartment and was looking at using this approach.

Just out of curiosity did you look t using a heavy duty drawer slide which the batteries would sit on to gain access to them once the couh was reinstalled? I liked the idea but not sure it's possible. I haven't done the measurements yet.

Again, thank you!

Mike

[EricZ]

Mike,

I actually left the seatbelts installed. I just put metal brackets under their bolts to allow a tie point for the battery hold-down straps. I also added extra reinforcement at the other end of the bolts (essentially big washers to spread the load).

You're right, the battery boxes would address the potential issue of things falling through the couch. They take up quite a bit more space, though, and I'm very tight on space. I did initially plan a simple plywood protective cover, but have not yet added one. As for outgassing, I've had no indication of this, even when charging my three Odyssey batteries at a combined true 105 amps (my PROsine is rated at 100 amps, but goes a bit higher).

I did not explore the option of slides for battery access -- I'm finding that it's literally a matter of two minutes to remove the couch seat (okay, and another five minutes to put it back). I leave the nuts finger tight, so I don't even need a wrench. Once the seat's removed I have very easy access to my batteries and wiring.

By the way, you might be able to fit one battery between the generator and the front of the couch (next to the converter/fuse box). This, plus a similar battery in the engine compartment, could get you two batteries without having to remove or modify the under-couch drawer.

Eric.

(In a future posting I plan to address some or all of the following: TriMetric wiring, location of TriMetric and other gauges, size of converter/charger, charger compatibility with AGMs, wire sizes, inexpensive sources for components, and solar.)

[weekender]

All of this is super interesting, but well above my knowledge. One comment, though: I converted the drawer to an open storage area by simply removing the oak front panel from the drawer (no need to even destroy the drawer), flipping it 180 degrees, a couple of hinges and a catch gave me a large storage area with easy access. A lot simpler than trying to modify the drawer, and would provide reasonable access to the batteries. Pictures are in my photo gallery.

Steve

[Mgittrich]

Eric,

Again thanks so much for the info.

Looking forward to where you mounted the trimetric and how you routed the cable. I've been noodling on this for awhile and the only relatively simple solution looks to be mounting it next to the bunk light switch and fantastic fan thermostat located straight up from the converter.

Mike

[Planck]

Mike
I put on deep cycle battery under the sofa, but if you want to sacrifice the drawer you could do 2 like I did one posted in the electrical section. Being non-agm I ran a vent tube to the generator box. The battery box eliminates any shorting concerns. Described here:

http://b190.com/viewtopic.php?f=4&t=724

Phil

[Mgittrich]

Phil,

I have seen this post before it had great information especially the slide piece. I saw the vent hose and thought ALL batteries needed to be sealed and vented to the outside if placed in an interior living space. With help from Ericz and some research i realized that this is not the case at least for certain AGM batteries, Diehard Platinum Marine and Odyssey. So now I'm torn between trays or boxes. Trays take up less space but have a higher short potential then boxes. Trays are also much cheaper. I think the short issue can be easily overcome simply by cutting a piece of 1/4" plywood that covers the entire under seat area. The assumption being that the converter and generator are not producing a large amount of heat. i'd be curious if you considered this approach for dealing with the short issue? I have a feeling that venting was probably what drove you to battery boxes which also took care of the short issue.

Thanks for the post and your reply!

Mike

[Planck]

Mike
Yes, the venting drove my decision the most. I would think the plywood, plus some terminal covers like are found on many vehicles would do the trick for you.

Phil