Battery relocation project - BF10.4

Does anyone know if you can cut in this compartment on the 2500 series BF? I have a basement model 2500 9.6 but there is no access door where you are showing.

I am happy to be whatever help I can.

I've never heard of VTE, they look like they have a lot of wiring supplies. I usually buy all my stuff from online retailers, often in the boating industry. Defender.com for example has normally reasonable prices, or closer to you is Fisheries Supply. For cable I like the Anchor brand, its a bit more expensive but always very good quality, fine stranded, and tinned. Its widely distributed at boat and some RV supply outfits, West Marine for example as well as the above e-tailers. Good thing about West is they are bricks and mortar, you can walk in a have a look at something. Anchor sells lugs for large cable, and an inexpensive hammer operated crimper for them, up to about 4/0, works pretty well. For large switches, relays, etc, I like Blue Sea, again widely distributed. Not that the others are necessarily bad, but I know I can trust a product from either Blue Sea or Anchor.

Surprisingly, batteries themselves can be had via e-tailer. Many of them in the states ship for free, not sure about the Great Frozen North. AGMs can be shipped normal package delivery like UPS. If you do that though, be sure to inspect them carefully on receipt, they are heavy and if not packaged well can get damaged. Unlike a retail store an e-tailer will not ask for a core charge.

HMS Beagle, thanks for all the detailed info and help, with my battery move/upgrade. I really appreciate it. When I get it done, I'll try to get some pics up. I'm going to get the batteries any day now, then I can gather the supplies to do the install. I was thinking of buying some stuff from here:

https://www.vtewarehouse.com/index.php

Do you know of any other online retailer for battery install supplies?

I've tried to change my profile, but it will not allow me to without adding my full address etc. which I prefer not to do - I get plenty of junk mail already.

The Happijac install literature says "connect to camper chassis ground". However it looks like originally they ran both a power and ground to the battery from the jacks, then thought better of it and connected power to the disconnect (and cut out the visible remaining power wire) and left the ground. I found remnants of the power wire here and there. The Happijac controller draws a small amount of idle current, so having it the far side of the disconnect makes sense.

This morning I temporarily powered up the Magnum inverter and discovered that it draws around 80 mA when everything is powered off. They suggest a disconnect so I guess that is why. Looks like I will be putting in another disconnect for it, but it needs to be around 200A capacity. I should be able to wire it so the same switch, so one switch will operate both.

I agree on the isolator - if there is a worry about some day needing to run on one battery, it would be better simply to put in a manual paralleling switch, leave it on most of the time, and turn it off only when you need to.

I would add on our camper nothing would turn off power to jacks.
Giving up after searching camper-got out the jacks install literature, said to wire jacks directly to battery. So looked and sure enough-power & ground went directly to batt junction terminals with 2 inline thermal breakers (front & rear). I added inline 50 amp toogle switches. So if camper mfg follows jack mfgs recommendation-(Atwood in my case) not unusal to find them wired directly, though I think most have ability to disconnect power.

to BCBigfoot106-I wouldnt add the isolator- You will get longer run times & better battery performance running in true parralel, treating as one big battery.

HMSbeagle-Great project. Though I usually notify author by PM you dont accept pms- added to the TCU thread.

The compartment is not vented. Most AGMs (and certainly Lifeline AGMs) will vent only under very extraordinary circumstances, like severe overcharging. If they vent, you have probably ruined them. In normal use they do not vent, fume, corrode, or spew acid. Lifeline suggests putting them in vented space but it is very common in the boating world to install them inside the living space unvented, and I am quite comfortable doing so myself.

I did finish the wiring and actually went camping last weekend. Most interesting part was the accordion stairs would walk up just a little bit while moving around inside, blocking the door shut! Twice I had to go out the Heki vent (which is a bit of a struggle), across the frosty roof, and down the ladder to get out. Another thing on the list....

Anyway the wiring: I ran a #8 around to the existing DC disconnect under the galley. I pulled the Magnatech converter wiring out of the panel, ran a #8 ground from the batteries to the Bat - terminal. If you remove the panel circuit board there is an addition Bat +/- terminal behind for the converter, I swapped the existing ground to that one. It runs from the original battery compartment. So the original wiring is preserved, I could add more batteries or emergency batteries or whatever to the original compartment at any time. I taped off those leads though, and secured them unused. While I was at it I ran a #2 red and black from the battery to the converter location under the bed step. This week I am going to pull the (now disconnected) converter and replace it with a Magnum MM612AE charger inverter in the space created. The #2 wire run is about 4 feet or a bit less. The remote for it will go in the panel under the closet door. This inverter was chosen because A) it is not made by Xantrex, and B) it has sufficient power for what we want to do (mainly powering laptops and phones, etc.) while having a fairly low idle power draw. It can be set up for proper 3 stage AGM charging.

There were a couple of complications: the Happijac ground wire was run straight to the battery terminal, it's a mystery why. I reran it to the chassis grounding lug under the bed step, since the batteries would no longer be there. BF had tapped into that line midway along for the ground connection for the DC disconnect relay - so I had to run an independent small ground from the relay harness to the grounding lug. This is how it should have been done at BF, but then there is a lot of wiring there that is ...well.... "not according to Hoyle". Another complication is that the AC/DC panel cover is screwed to the converter chassis, when I remove it I will have to bend a couple of bits of sheet metal to recreate the mounting holes.

A complication with the inverter: Magnum says it has a "20 amp AC transfer relay". While this might be true, it has an 8A input circuit breaker and a 7A output circuit breaker, so you can never use the 20A capacity. Seems disingenuous, but I confirmed with them over the phone. So I will have to split the AC panel and run just the wall plugs from the inverter output, leaving the AirCon and microwave circuits connected to the shore power input. Now I really don't want the refer AC (which is on the same breaker as the wall plugs) running from the inverter either so I may rewire the outlet for the refer to an unused breaker sourced from shore power. I usually only run the refer from AC when I am cooling it down while loading up for a trip anyway so it may not be worth the bother to change - but I don't want it switching to inverter power automatically. I don't have air con or a microwave, so if for some reason I needed to run a very power hungry device from shore power, I could plug it into the microwave outlet. Other outlets would only source 7 amps, (less if the charger is working hard).

The largest DC draw in my camper (besides the inverter) is the Happijacs I think. The controller has 20A fuses for each motor, I run only two at once so that would max at 40 amps. However BF installed inline 30 amp breakers, and it works fine that way. Given that you are unlikely to operate the jacks with a lot of other things, I think you could consider those or the charger to be the highest current your wiring will see. If you have a 60 amp charger, then I would consider running #6 wire directly from the charger to the batteries with 80 amp fuses at the battery (the charger is considered to be a current limited device). Then power the house from the existing #8 wire with a 30 or 40 amp fuse (or breaker). If the charger feeds into the panel or somewhere other than the batteries, then all that wiring really should be upsized, otherwise a short somewhere could see 60 amps on your #8 wire. I think that is a little over the edge of legal.

No, i'm not running two battery banks. I'm thinking of doing as you have done, and relocating 2 batteries to the inside front of the camper.

I thought that maybe, by adding an isolator, it would protect each battery from cross discharging. This would be in the case of one battery goes bad. I'm still learning when it comes to understanding how the RV 12v system works. So, running them in parallel, so as to limit the discharge level makes sense too.


With just one battery bank and no inverter in the system. I guess I have 60 amps going to the battery bank. What would be the largest draw be? Just trying to figure out the wire size needed. I know the wire size is based on amp draw and the length of run. Once the wire size is determined then you can pick a fuse size?

I have the same camper and use AGMs. Thought the same thing when I removed the cover to the area you are using and saw all that empty space. Not only does it shift weight forward but it also moves it from the heavier passenger side to the lighter driver side. I'm better at woodwork and plumbing than I am at electrical though so wasn't sure what to do with the wiring. I'm interested in seeing how you work that part.

Nice install! Is that new compartment vented? I believe AGMs still vent hydrogen gas when charging.

BCBigfoot106 wrote:
I was thinking of using a battery isolator to seperate the two batteries. To prevent any cross draining between batteries. I was thinking of using a 90 amp isolator. It has 3 posts. One for each battery and one labeled, "Alternator", which would go to the converter? I'm guessing it's a diode based one, like you described. You said they cause a voltage drop?

Yes, that is how they are connected, and yes, they will always have some voltage drop. If the charger has a remote sense wire you can put that around the isolator and it will compensate - at least for the one being measured. But most RV chargers don't seem to have remote sense.

Are you running two battery banks in the TC? The modern thinking is to just parallel them and run them as one large bank. There is a good argument for doing so, it minimizes the depth of discharge and thus maximizes lifetime. However you may have other reasons. If two banks, I would use an automatic charging relay rather than the diode isolator. This is an ordinary relay with a simple circuit that senses when charging voltage is present (more than around 13.5V or so) and closes the relay. Whenever you are charging, they banks are parallel, whenever not, they are separated. Blue Sea is a good brand but there are many that do the same thing. Some have a manual override so you can parallel them with a switch if you need the full capacity for some reason.

As far as fuse size, at the battery. Does this need to be slightly larger than the largest draw on the batteries? I think my Happijacs have 2x20amp fuses. So 50 amp fuse?

I'm going to use AGM's and I have a PD 9160 converter. I have some #2 wire to do the runs to the converter.

Usually you choose fuse sizes to protect the wire. Any connected device should have its own overcurrent protection, if needed. So if the smallest connected wire is #2, you might use a 200 amp fuse. Of course you can go smaller. The idea is in the event of a short, you blow the fuse rather than burn the wire (and your camper), i.e., the wire always has higher current capacity than the fuse. My Happijacks seem fine on a 30 amp fuse (and have their own fuses as well). If you have a #2 running from the battery to the charger or an inverter and also a #8 feeding the DC panel (typical in a TC and what mine has) then you really want to fuse the two lines separately, as close to the battery as possible. I am using a 50 amp for the #8 and a 200 amp for the #2. This is a very convenient way to do that (though as others have pointed out the fuses are expensive at around $15 each). Two high current independent fuses right at the battery terminal.