HDJ81 Dual Battery System (1 Viewer)

[Douglas S]

I'm nearing the end of this installation, so I thought I'd throw together a quick write-up for anyone interested.

This whole project came about because the original 4.5kw, 24V starter in my truck shorted out earlier this year, killing both batteries and leaving me stranded. I wasn't going to get a better opportunity to get this project out of the way.


12V Starter Conversion
This part of the project was fairly straightforward. I purchased a new 2.5kw 12V starter and replaced the original one. I had to rewire the ground circuit on the starter solenoid because the original ground passed through the now-removed series/parallel solenoid and timer.

Battery Selection
I chose to go with a group 31 AGM (Deka) as the main/accessory battery and a group 34 Odyssey as the starting and winching battery. The group 31 required some minor trimming of the battery tray and a new hold-down. I also weighs about 80lbs so be prepared to lift that into the engine bay of a raised truck.

I would have gone with Sears Die Hard Platinum batteries if they were available to me, but Sears does not offer them in Canada.

System Selection
Choosing a system was one of the hardest parts of this project. There are a lot of really good options on the market (National Luna, Hellroaring, IBS, etc.). In the end I narrowed my options down to the Blue Sea 7622 (with a National Luna battery monitor) or the IBS system.

I chose to go with the Blue Sea unit for a couple reasons. Firstly the the Blue Sea ACR has a continuous current rating of 500 amps at 12V, meaning that combining the batteries to power my winch is not going to present any problems. Secondly, the Blue Sea unit also has manual controls in the event of complete failure of one of the batteries. The IBS requires an additional relay to operate in low-voltage situations and will not function at all if the controller battery is completely flat.

The downside to the Blue Sea unit is that it is not a fully integrated package, meaning that the install is more involved than say the IBS or National Luna systems.

Mounting
Because my truck originally came with a 24v starter, there was a series/parallel switching solenoid mounted on the LHS fender. This presented the perfect location to mount the Blue Sea ACR. I drew up a bracket in Inventor, which should be ready next week. This will get mounted to the original solenoid bracket.

Wiring
As mentioned above, the Blue Sea ACR is not a full integrated system. This meant that I would have to make my own wiring harness. I love wiring, so this didn't really concern me. I ordered some multiconductor wire and Deutsch connectors, and put one together. The control switch should arrive next week.






So that's where it currently sits. I have 15ft of 2/0 welding cable, an assortment of adhesive lined heat shrink, and a hammer crimper sitting on the workbench waiting for the last few items to arrive. I'm planning to have everything finished up in the next few weeks.

 

[BCR4619]

Very nice, I was looking into doing something similar as I thought something was messed up in my electrical system around the parallel switch but it turned out to be a loose connection on my battery so I never got further with this.

I don't every go off-road or camping much so i don't know if this wold benefit me, Camped for a 4 days in Aug last year and just ran the ARB off the stock batteries no problem, this year I will have solar thou.

 

[greentruck]

Nice craftwork.

Deka makes good batteries. Powered most of the forklifts where I used to work in a previous career.

 

[B Point]

This is something I have considered as well. I will reference this thread should my 24V starter ever crap out or I start taking my camping trips to the next level.

 

[Enigma]

Just curious, why would you have the winch powering off your starting battery and not off the accessories? Wouldn't you somewhat f yourself in an intense winching session?
I converted mine to 12v start a year or so ago, no issues so far. Didn't go quite as fancy as you have done, kept the original starter as mine was fine but changed out the nose cone from a 12v unit.
I do have a winch or two I've been meaning to install, hence the battery selection question.

 

[Douglas S]

Just curious, why would you have the winch powering off your starting battery and not off the accessories? Wouldn't you somewhat f yourself in an intense winching session?
I converted mine to 12v start a year or so ago, no issues so far. Didn't go quite as fancy as you have done, kept the original starter as mine was fine but changed out the nose cone from a 12v unit.
I do have a winch or two I've been meaning to install, hence the battery selection question.

I'm actually still not completely decided on which battery the winch will go to. Either one should work fine in this setup, I was thinking of using the starting battery just because it's easier to wire like this the way my bay is set up. I will always parallel the batteries when winching so they really just act as a single large battery in that situation.

I also need to do something about the charging voltage in my truck. Before any of this I would see ~13.9v, which isn't enough for AGM's. I'm going to see what the charging voltage is with all new cables and clean grounds, but if it isn't enough I'm going to try putting a diode in the charge sense circuit to bump the voltage up.

 

[IanB]

I got a new Pioneer headunit a few months ago, which has a volt meter on the display, and I find that on a cold start I'm only getting about 13V, and once you start driving it settles in at about 13.9-14.1V, I've never seen it output more than 14.1V. I should be seeing 14.4V, but I haven't gotten past this point in my diagnosis process.

 

[CycloSteve]

I got a new Pioneer headunit a few months ago, which has a volt meter on the display, and I find that on a cold start I'm only getting about 13V, and once you start driving it settles in at about 13.9-14.1V, I've never seen it output more than 14.1V. I should be seeing 14.4V, but I haven't gotten past this point in my diagnosis process.

There is a voltage drop between the battery and other parts of the vehicle. Unless you have your meter directly at the battery, or are running a large gauge wire, the reading will be lower. Take a reading with your voltage meter at the battery, and it likely will be closer to the 14.4v reading, while your head unit may still only read 14.1v.

 

[Douglas S]

There is a voltage drop between the battery and other parts of the vehicle. Unless you have your meter directly at the battery, or are running a large gauge wire, the reading will be lower. Take a reading with your voltage meter at the battery, and it likely will be closer to the 14.4v reading, while your head unit may still only read 14.1v.

My 13.9v reading was taken at the battery. It is within normal range for the truck, but at the lower end of that normal range.
Alternator was recently rebuilt.

 

[Douglas S]

So as a low quality, picture-free, update I have had everything installed in the truck for some time now. The Blue Sea ACR works flawlessly and I picked up .2V by cleaning/upgrading all of the cables and connections in the system.

I mounted the National Luna battery monitor on the side of the center console, but have yet to wire it in and I am still searching for the best location for the ACR control switch (the ACR functions in Auto mode with it disconnected).


I will update with pics sometime this weekend hopefully.

 

[coax]

Very nice! Your wiring looks much better than mine I've been very happy with that Blue Sea ACR. Just put 25k miles on it in South America and it worked perfect. I too wired it similar to yours with the winch on the starting battery for exactly the reason you mentioned (that I'll parallel both batteries in the event of any winching). Looking forward to the finished install. (Also, with a little filing on the remote switch it fit into one of the switch blanks left of the steering wheel)