Jump starting from DIY LIFEPO4 battery pack..

BorealOverland

Active member
Hi guys, i have a question and hope you fine folk can help me out a bit..

Earlier this year i build a DIY Battery pack, see link:

So far the pack is working fine.

My question is:

Can i use the 125A ANDERSON connector to hook up some fairly beefy jumper cables with an ANDERSON connector
and jump start my or any car that way..?

1. We can do this by letting the battery's be connected to each other and let the low 40AH (acid) battery balance and hopefully have a high enough voltage to start..
disconnecting the DIY LIFEPO4 pack first before trying to start the car.

2. Or leave it connected to the DIY LIFEPO4 pack and jump start it like you normally do with a "normal" jumpstarter.

Problem i see with method 2. is i could blow the 125A fuse behind the ANDERSON plug, damage the 200A relay, the 200A main power switch
and or blow up the last 400A fuse between the Main switch and LIFEPO4 pack.

Here are some photos to show you how i have the ANDERSON plug connected:

BorealOverlandIMG_4714.JPGBorealOverlandIMG_4715.JPGBorealOverlandIMG_4720.JPG

The Victron Battery Protect in the photo is not in line with this ANDERSON plug,
it only powers the 200A Relais that powers the ANDERSON plug from busbar.

What i also can do is neglect the 125A ANDERSON plug and just put a normal set of jumper cables directly
on the beefy 3 way M8 busbars you see on the left (+) en right (-) of the pack.
If i do that there is "only" the 200A Main switch and the 400A fuse in line..

So what would be the best way to go about this..?

Hope you guy's can give me some advise on this matter.

Thanks for your help, stay safe!

Steve
 
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BorealOverland

Active member
Come on guys...
where all the electric guru's hanging around that can give me some solid advise on this one?

Stay safe,
Steve
 

Chris Boyd

Explorer
I’d go with option 1.

Momentary amperage on a starter could go much higher than 125 and probably 200, risking blowing the protection you have built in. I don’t run fuses between my dual batteries for this purpose (and winching). I just have the battery separator (ML-ACR) to break the circuit if needed.

Maybe do something like get a small jump pack for this task. They are less than a hundred bucks these days. You’ve got a lot of nice work in the DIY system, would be a shame to wreck it. The jump packs use a capacitor to spool up energy and feed the momentary surge.
 

Chris Boyd

Explorer
The inter webs just spit this up:

Autowit SuperCap 2 - allows for slow draw from LifePo and storage in the capacitor for cranking power. Maybe a bit better than a jump pack to keep charged.

Not tried it myself, but curious that the YouTube pushed to me after I posted up here. Eek.
 
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BorealOverland

Active member
I’d go with option 1.

Momentary amperage on a starter could go much higher than 125 and probably 200, risking blowing the protection you have built in. I don’t run fuses between my dual batteries for this purpose (and winching). I just have the battery separator (ML-ACR) to break the circuit if needed.

Maybe do something like get a small jump pack for this task. They are less than a hundred bucks these days. You’ve got a lot of nice work in the DIY system, would be a shame to wreck it. The jump packs use a capacitor to spool up energy and feed the momentary surge.

Hi Chris, thank you for your response.

Yes you are right.. i have a pretty penny invested in my battery pack and it would be painful to break it like you said,
and have no way to fix it when on a road trip..
I am looking at a couple jump pack options, the Noco GB40 for example should do the job for me.. or i'll go 1 larger.

Someone on Overland Bound forum suggested using a DC to DC charger as a safe way to charge the flat battery back up.
I was thinking of getting the Victron Smart DC to DC unit in the near future, to charge my battery pack in the back of the car while driving.
So this would be a option as well, maybe connect the unit with Anderson plug so i can reverse battery's and charge the flat starter with the Lifepo4 pack.. but without having alternator power of course..
This idea is nice but cost a bit more than say a Noco and the Noco i can use for other cars as well so that might be the most cheap and simple option for me right now..

I was just looking at the possibilities i have with the gear i all ready own,
but there's no need to make things more complex than needs to be..

Thanks!

Steve.
 

BorealOverland

Active member
The inter webs just spit this up:

Autowit SuperCap 2 - allows for slow draw from LifePo and storage in the capacitor for cranking power. Maybe a bit better than a jump pack to keep charged.

Not tried it myself, but curious that the YouTube pushed to me after I posted up here. Eek.

I am going to check that out... thanks!
 

Chris Boyd

Explorer
I am going to check that out... thanks!

It definitely looks interesting. Amazon shows both the supercap2 and a lite version. I’m going to do a bit more research, but I might retire my lithium jump pack for this, as my pack is aging and the jump feature is hit or miss.

I usually have someone else around, or if not, have my trailer with its own battery on board.
 

jonyjoe101

Adventurer
I build my on 4s lifepo4 jump pack using 24x a123 cells. The only time I had to use it in anger to try and jumpstart my astrovan v6 engine it failed me, it wouldn't crank it over, but I also tried a 27ah agm battery to jumpstart it and it also failed. The battery was completely dead. Even leaving the battery connected for 15 minutes didnt help. Eventually I just removed the start battery and put in the 27ah agm in its place and that worked.

One year later I still have the 27 ah agm as my start battery. I bought a 16ah oddessey agm and now I use that as a backup to jumpstart or in worst case scenario installed it as a start battery.

I still got the lifepo4 jumppacks and will try that first. I've jumpstarted a small 4 cylinder engine with it, so it does work, just won't work on a completely dead battery.

I built a boost/buck converter and set it to 14.7 volts/2 amps output and its in the back of my van. I use the house battery to top off the start battery every other day to keep the start battery in peak condition. I get a strong crank every time. Highly recommend something similar to everyone especially if you park for extended periods without starting your engine.

10ah lifepo4 jump packs, I built 3 of them.
1 jump packs lifepo4.jpg

My 16ah oddessey agm, I use this as a backup battery. Better to have a battery and not need it then need a battery and not have it.
1 16ah oddesey.jpg
 

Jman99

Member
What Id like to know is why are you asking this if you built that pretty advanced system? LOL
In my experience jump starting implies battery neglect, I have never had to jump start my own stuff because I want long life out of my starters. They are always near 100% and replaced when aged.
but imo the best jump starter you can build in with headway lifepo4 in plastic container, no bms required, no balancing, just a fuse. keep them at about 60% and they should hopefully start as they pack so much punch its crazy, may last 8years + while those li-ion jump starters will probably be useless in 3-4years.

other ways to charge a flat starter, are put a solar panel on starter battery direct for a few hours. with a good starter battery maybe 30mins is all thats needed.
 

BorealOverland

Active member
What Id like to know is why are you asking this if you built that pretty advanced system? LOL

Well that i manage to build a nice battery pack does not make me an expert.. LOL
And i do have a pretty good idea what i can do with it and it's limitations,
thats why i suggested the 2 options.
But it's always good to hear the opinions from other maybe more experienced people in the field
who has figured out these sort off things all ready..

I hear you about the neglect part.. and we should keep our rigs well maintained,
but that doesn't mean things can't happen.
A bit like carrying a (big) fire extinguisher, you never need it until that day comes..

Yes a portable solar panel (depending on output voltage) is also a option indeed (if the sun shines and not in a hurry),
in fact 1 carry a 100W foldable solar panel with me to hook it up to the battery pack if needed.

Like Chris Boyd said, i think i am going to pull the trigger on the Autowit Supercap2
That thing gets good reviews. Should work in a pinch and when the starter battery is to flat i can "pre-charge"
the capasitor via another car battery, my battery pack, usb or at home before you leave on a road trip.

Thanks for your input J.
 
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BorealOverland

Active member
What is the current limit on your BMS? That is likely to be the limiting factor.

Hi,
The BMS is 40 Amp... but NOT a limiting factor because of the way i build my battery pack.
I have a 100 Amp Victron Battery Protect (VBP) build in the box..
The VBP connects or dis-connects all out going power outlets and relais for the 50A and 120A Andersons.
(The 50A and 120A connect via a relais that is powered by the VBP to the - and + busbar.)
The BMS is connected to the VBP as the - negative input, when the BMS cuts off, the VBP disconnects as well.
That way you can have high amp outputs but use a tiny 40 amp or smaller BMS.
 

Rando

Explorer
Hi,
The BMS is 40 Amp... but NOT a limiting factor because of the way i build my battery pack.
I have a 100 Amp Victron Battery Protect (VBP) build in the box..
The VBP connects or dis-connects all out going power outlets and relais for the 50A and 120A Andersons.
(The 50A and 120A connect via a relais that is powered by the VBP to the - and + busbar.)
The BMS is connected to the VBP as the - negative input, when the BMS cuts off, the VBP disconnects as well.
That way you can have high amp outputs but use a tiny 40 amp or smaller BMS.

These seems like an odd way of doing this. Doesn't this disable all the current based protections on your BMS? It seems like it would be cheaper and easier to use a 120A BMS: https://www.lithiumbatterypcb.com/p...munication-with-60a-to-120a-constant-current/. You could also get rid of the battery protect and the cell monitor and even the capacity monitor, and relays, greatly simplifying your box/wiring and reducing your parasitic power consumption.

If you need a higher current jump starter, buy one of any number of lithium polymer jump packs they are inexpensive, work well and would give you redundancy. I have good luck with this one, but sold under a different brand: https://www.amazon.com/Arteck-18000mAh-Portable-External-Automotive/dp/B01LXC8SPF/
 

BorealOverland

Active member
These seems like an odd way of doing this. Doesn't this disable all the current based protections on your BMS? It seems like it would be cheaper and easier to use a 120A BMS: https://www.lithiumbatterypcb.com/p...munication-with-60a-to-120a-constant-current/. You could also get rid of the battery protect and the cell monitor and even the capacity monitor, and relays, greatly simplifying your box/wiring and reducing your parasitic power consumption.

If you need a higher current jump starter, buy one of any number of lithium polymer jump packs they are inexpensive, work well and would give you redundancy. I have good luck with this one, but sold under a different brand: https://www.amazon.com/Arteck-18000mAh-Portable-External-Automotive/dp/B01LXC8SPF/

Hi,
Yes i could have build my pack in a more simple way with that kind of BMS,
and you are right about parasitic draw from the relais although that only comes on when the 50A or 120A are powered.
However a year or more ago when i started looking into and ordering the BMS stuff at least i didn't find any
that had Bluetooth and features like that and 120A -150A capacity.
Most Daly brand 120A -150A BMS that i looked at were more expensive than the Victron Smart Battery Protect that i bought on sale.
I like the sturdy Victron components and because i all ready had some that could connect to Bluetooth i went that route..
With more and more BMS options coming out now for a next build i would consider them indeed.

Yes i think i'll leave my "Jump start from battery pack idea" for what it is and have a look at a decent jump pack to go with it.

Thanks for your response and links..
Steve.
 

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