The next new project that I’m working on now after finishing off my custom made 1U pFsense router (or at least 95% finished) is my hybrid OBD jump-start car pack.
I actually started saving up for this project in February, as I have a lot of components that I wanted to buy for it, and wanted to get a bit of a jump start on it before writing this post. As I predicted the end cost would be around £600 to build
Please note, this is a live project, so rather than the pfSense one I’m going to update the article as I go along with it. The battery pack is something I want to do last, as it’s the thing I haven’t decided on yet
More to add as I go along with the building
Why do I want to build this tool?
- I wanted something custom built. It gives me a chance to experiment and build something, it’s custom to me, and my car but functional for many and I’m tired of having to carry multiple things for a functional. External jump packs are heavy and bulky, I wanted something compact where I could store all the tools inside the device, or a case that goes with it.
- I don’t like carrying multiple tools. I wanted one thing for my car that’s always there
- I didn’t want to rely on anyone else. How many times have you seen people stranded trying to flag down others or wait for help. The amount of times I’ve had a flat battery on a car and the jump start doesn’t work has been infuriating. I’ve always bought the Cheap lead-acid based jump starts (I have a Clarke Jump Start 1100), however it’s failed to jump both my car and a family members car when I’ve needed them when the battery was dead (although I bet jump starting from another car would work instantly). It doesn’t help with me being impatient, as I wanted something I could hook up. Switch on and be ready to go. Lead-Acid batteries you have to leave for a few mins to discharge before you attempt it. I tried this with the above charger, but it didn’t work for me. LiPo based devices tend to have better luck (Devices like the NoCo are one of the most common for example). So I wanted a device that could provide the full voltage and power instantly with no hold up. With a built in LED it allows me to work on my car with any tools I’m carrying, or if I have a flat battery, jump starting my car without relying on anyone else.
- Lead-Acid batteries have a crap lifecycle. The more modern ones have really good discharge rates, where you can leave them for several months. Lead-Acid batteries require a constant trickle charge. I wanted something I could forget about for months, and grab it when needed.
- I’m tired of devices giving their “Fake” power, advertising they can jump start vehicles “up” to 8 litres in size, or can output 1000A but can realistically only output this number for a couple of seconds then it drops to maybe 140A over a few seconds because their cables or batteries are so small. I wanted a device that would continously pump out the current requested until the batteries were drained.
Why did I choose Anderson connectors?
Anderson connectors people in the 4×4 and Recovery scene are probably familiar with. I know of them because I work in a warehouse, they’re quick change connectors designed for high currents. They’re also genderless, so there’s no male or female socket. It’s also impossible to fit them the wrong way around, because they can only be inserted the right way. As a note you can still wire them up wrong, if you’re being thick and don’t read symbols. Other than that they’re simplistic
Now the connector I have is an Anderson SB350A connector. This type of connector is designed for a rated current of 350Amps continuously (I’m honestly not sure if this is total, or per pole, I’m “assuming” it’s per pole). However, it was the largest one available without looking into the newer Power Pole type connectors, and they’re rated up to 600V. They’re also easy to remove, which fits my setup.
I wanted something portable, easy to disconnect and reconnect when needed and sufficient for my needs. So these fit. If Anderson connectors are good enough for Forklifts and Reachtrucks, they’re good enough for my little booster pack.
Technical data for cables
Here is the technical data of the conductors I’m using. Current rating is 485A per cable, using my own formula I esimate this to be 433A, so my figures are in the approximate ball park.
Sheath Colour: Red (Power) + Black (Earth)
Nominal Conductor Specification: 1014/0.285mm
Conductor Cross Section: 70mm²
Current Ratings: 485 Amps
Maximum Overall Diameter of Cable: 15.6mm
For reference, the cable I’m using in my power pack is Oxygen Free pure copper cable. In theory, they’re rated to carry currents up to 485 Amps (approximately). So regardless, they’re ideal for my jump start station. Whether they can carry more, I’m not sure, I suspect they could (and there’s probably a formula somewhere), but for now I’ll work with what I have.
Making up cables for the Anderson connector
Whilst I haven’t decided the end route yet in terms of how long these cables will be. The only thing I knew for sure, was that I was going to use Anderson connectors, and the cables were going to be as thick as possible for as much current as possible. At the same time they were going to be short to minimise voltage drop. Ideally the end-result for this cable would be capable of 24V jump starts too. I would like it to carry (for a short-time) close to 1000A, however I don’t know the safe limit of these cables. Generally any cables if they get hot it means they’re carrying too much current.
Here’s the procedure I carried out for assembling the Anderson Connectors to my cables. Pictures in order in the gallery below.
- This is just a picture of the Anderson connector, as you can see it’s a simple design.
- The pins do have to be inserted a specific way (if you don’t they will push out when inserting the other half)
- The terminals also have + and – for connections, so you still need to insert the relevant polarity into the relevant slot
- In order to release the terminals for fitting (or if incorrectly fitted) you push on a spring place that releases the locking of the pin
- I measured up the wire against the terminal for the Anderson connector, and cut around it
- After cutting around it, I moved the insulation just up to prevent the cable from splitting
- The connector was then pushed over the cable (first time I did this, so I over measured)
After inserting the wire into the terminal, it was time to crimp it
- Using my Hydraulic crimp tool (YQK-120). I inserted the 70mm dies
- I then manually pumped the trigger to crimp the wire onto the terminal
- This is the first time I’ve used it, so had to gauge it. The dies aren’t really the best either so the cable connector looks poop. I’m happy however if the end result is stable and secure
- As a note, once I felt resistance (when I knew the terminals were adding pressure), I pumped around 9 times for these results
- I then yanked on the terminal, and recrimped it along the tube so I knew it was snug and secure on the cable
After I crimped on the terminal. I wanted to protect it against the elements and make it look a bit more professional
- I used Black/Red heatshrink with a 25.4mm (1 inch) diameter, with a 3-1 shrink ratio
- The heatshrink was also “Marine Grade” (it has glue inside it, so as it melts it applies glue to water proof it)
- I opted for marine grade, so that it minimises water and moisture going inside the actual terminal and rusting it
- I applied the heatshrink onto the cable, covering the connector and the cable (about 2″ long was cut and heated it up)
- Once the cable was shrunk, and the glue was visibile at both ends, it was ready to insert
Insertion is an easy process and fairly self explantory
- Insert the connector (with the point edge facing down over against the flat part of the housing) on the correct polarity side
- Push the connector fully and hard until and audible “click” is heard
- This will be the connector latching onto the spring plate if inserted correctly it will hook slightly under it and will stay in place
- After inserting the negative cable, it was a case of repeat for the positive
- Repeating the cutting, crimping and heatshrink
- I then relatched again into the + of the housing
After this, I give a quick tug test then the cable was finished on one side. Whilst I’m still deciding how long to make the cable, or how I’m crimping the other end. I bundled it together with zip ties and put it to one side.
Assembling the battery cable to Anderson connector
I then repeated the procedure for the internal battery cable as above. This is going to be carrying the high current from the internal busbars to the internal Anderson connector inside of the jump pack.
Procedure was similar to previously. Using the piece of the original cable that I chopped off a section (approximately 10″ long). I then went through attaching an Anderson connector on the end of it by doing the usual procedure by disconnecting the plugs on the other connector, and stripping the cable. It’s easier to get out the Anderson plugs by holding it vertically as you press on the tab, they should release allowing you to pull them out easier
Once I stripped the cable I went about the usual method of crimping the Anderson plugs, onto it and whipping out the big boy YQK-120 hydraulic crimp tool again and crimping the connectors. After that finishing up with Marine grade 3:1 shrink ratio heatshrink
After the connector for the Anderson plugs was done, I then needed to attach eyelets to the other end of the cable which will be attached to the bus bar. Again I’m using high quality 70mm2 copper eyelets. This will simply be bolted directly onto the bus bar and carry the current from the battery/busbar to the jump clamps. Same procedure as previously, strip cables, add old trusty and it’s 12Tonnes of hydraulic pressure and make up some internal connectors. The end result below
Assembling the jumper clamps to Anderson cable
Once I had assembled the internal cable. I set to work on the main jump lead cables.
The connectors I’m using I purchased from a supplier in the UK (Altec Automotive). I’ll update this post at the end with links on everything I’ve used to date. The clamps are pure brass and fully insulated. Rated to 850A of continuous current and designed to handle 70mm2 cable. Perfect for mine.
Procedure for the assembly was same as previously. I stripped back the insulated handle cover and slid it down the cable used for the jumper lead clamps. Once the cable was stripped, I fed it into the brass clamp housing. These clamps are designed to clamp straight onto the cable. I personally don’t like this way, I’d rather crimp / screw it down, but for now it will do. The cable matters just as much as the quality of connection. I may revise/recrimp at a later date.
You receive cables and torx screws with the handle, the torx screws are quite short though so you may struggle adding in 70mm2 cable if you do it this way. I ended up using longer M5 screws to clamp down hard on the cable, then swapped it over to the torx when it was compressed and tightened it up so it was flush
Once I’d tightend it up the covers were then slide back over the cable so it was fully protected and procedure to be repeated on the other side (I haven’t done it on the negative pole yet as I want to get longer machine screws).
Once I assembled the cable, I used my multimeter for a continuity test. The cable from end to end reads 0.002 ohms (2 milliohms) of continuity, this is good. I believe 0.001 is ideal (anything lower would be considered a superconductor anyway). The figure was hovering between 1-2 milliohms when measuring, so I’m fine with this. It didn’t matter whether the Anderson connectors were fitted or not when measuring end to end the continuity was the same. So cable connection is good quality for me. A result so low even the clamp was shocked
– – in progress
Internal bus bar design
Due to this pack being design for high current / low continuity jump starts (in an ideal world anyway). I’m designing this pack to carry 900+ amps on the internal busbar. I originally purchased some cheaper bus bar (10mm x 4mm) which was in multiple lengths, and I was going to sandwich them together. I changed my mind and aimed to beef it up. Although I’ve kept them as I’m thinking of making the pack hotswappable
Eventually I switched out to purchasing a C101 grade (which is a very high purity used on busbars), the exception being Silver busbars have better conductivity but cost a load more too.
As this build is only a small project, and limited budget. I wanted something to suit. The bus bar (flat copper bar), that I purchased was C101 grade, and it’s dimensions were 25mm wide x 10mm thick.
A bus bar of this size “supposedly” and I use that term loosely, has a “Free Air DC” current rating of 695 Amps of rated capacity. As busbars are based on their cross sectional area (width x height), this would give it a 250mm squared cross section. I’ve always worked on the calculation of 1.5A per mm2 of carrying capacity (I read it somewhere, but believe it was related to circuit boards on PCB tracks). Regardless it’s the only information I have to work with. So I base the realistic amp rating capacity of this singular piece to be approximately 375A on a good day.
Now, this is way lower than by 900A + figure. That’s absolutely correct, that’s because I purchased a longer bar with the intention of chopping it up into smaller pieces, and then sandwich them all together for a thicker bus bar (this is accepted afaik). I’m hoping I can figure out a way to use a DC switch so that I can join up 2 internal 12v packs in parallel for when running in 24v mode. That will be a future upgrade. As currently I just want the 12v mode for function
The bus bar was chopped into 6 sections (50mm long), the length is irrelevant. So when assembled my bus bars will be 2 pieces total one for each polarity. All sandwiched together, into a 2 smaller bus bars that are 25mm wide x 30mm thick. This gives them both a cross sectional area of 750mm squared. So following my 1.5A per mm2 formula, this gives me a free air DC rating of 1125A. I could add another 10mm piece later on and this would allow me to go to 1500A .
I don’t have the exact amount to hand, but ratings online suggest this design could carry around 900A. So it’s on the park by what I think. A 25mm x 16mm piece supposedly carries close to 1000A. Someone can do the math and work it out. Based on the technical data for the cables it seems to be approx 1.67A per mm2 so this bus bar in theory can actually do closer 1250A. When I’m finished, I’ll probably hook it up to a 1000W-2000W load resist and then put an amp clamp on to see what it pulls by stalling the motor so it has a lower spin speed to simulate an engine start
to be continued……….
