Do you think this could be made to work as a battery pack?

[petepete]

do the will 100ah cells and smart bms for $200.

its simple to link to alternator for charging or just charge it with a $40 charger.

lifepo4 batteries are absolutely bullet proof and i use my 100ah to run 2 diesel heaters gas heater laptop tv fridge lighting phone charging and even heat water with it never mind use a full size home vacuum cleaner via inverter....

from flat just over 2 hours to re charge via 800w genny.

lol bite the bullet and spend coz piddling around with 9ah aint going to solve the problem lol

 

[SawMaster]

While I was borrowing a vehicle with no ciggie outlet, I used an old 7aH SLA to power a single dashcam. IIRC it was good for ~6 hours recording; a new battery would likely have gotten a lot more.

Phil

 

[thomas-dash]

lol bite the bullet and spend coz piddling around with 9ah aint going to solve the problem lol

You talked some sense into me, lol.

I looked through Will Prowse’s list of batteries again and saw that Ampere Time’s Amazon listing had available stock and would ship to my location.

I bought the battery on 11/10 and it arrived on 11/15. I’m still surprised it actually arrived and I didn’t get an email that they made a mistake and couldn’t ship it to my location.

Total cost was about $530. $400 for the battery, $128 shipping and handling, $24 for taxes, and a $20 Amazon discount.

I bought twenty feet of 6AWG cable over the weekend for the positive side to run to the starter battery. I still need to buy a dc-dc converter, relay, 6 gauge terminal lugs, fuses, crimper, and a battery box w/ straps or some type of metal frame battery holder. I’ll need to pick up a charger to have on hand in case I need to bring the battery inside to charge it.

 

[petepete]

you ll be singing their praises soon and keep us informed.....

 

[thomas-dash]

I'm getting pretty close to the finish line. I have most of what I need. I ordered some 40Amp MEGA fuses to put on my starter and LiFEPo4 batteries. They were supposed to come in last week, but were lost. I asked Amazon for a refund last night ordered some ones and the first order showed up this morning. Unfortunately, one of them looks like it might be a used one. It looks like it has some burn marks from electrical arcing, but I don't know for sure. It didn't come in "Littlefuse" packaging, just a plastic ziplock baggy with an Amazon product number on it What do you think, is someone selling old fuses on Amazon as new fuses?




The one with the significant scorch marks is the one on top in the below photo:



There was another one that looked like it has some type of dried fluid. I guess it could be a part of the manufacturing process, but given the above fuse it seems equally likely to have been used:





They all passed a continuity test. I'll reach out to the seller and see what they say, but I would love to hear your opinions about them.

 

[Nigel]

They look unused to me.

Maybe not from the most high tech western owned factory producing top quality product, but nothing to worry about.

The "scorch marks" are probably just a poor coating or poor cleaning, maybe because it was sitting on the edge of the batch and didn't receive a full dose, that won't affect functionality. The fluid drops are probably from the washing liquid that was supposed to wash off the "scorch marks" and still contained a bit of them when it dried.

 

[thomas-dash]

It appears the ACC and battery wires on the Viofo HK3 hardwire kit need to come from the same voltage source in order to work properly. I installed the 100Ah battery in my car last night and ran two 12 AWG copper wires from my trunk where the battery is to the passenger cabin fuse panel which is located close to the steering column in my car. I figured I would wire the dash cam directly to the battery for now while I get everything else in place for the Victron DC/DC charger. I ran the 6AWG cable that will be going to the starter battery at the same time and left it on the passenger compartment side of the firewall for now.

I thought I was going to be able to leave the ACC cable hooked up to the fuse box and still use it as a trigger to put/take the dash cam into/out of parking mode. When I hooked the dash cam up to the positive and negative terminals of the 100Ah battery, it wouldn't turn on even when I turned my car on to give power to the ACC cable. The dash cam would only turn on when the ACC cable was getting power from the 100Ah battery. It seems I'll have to get a relay tied into an ACC circuit on my car to switch power from the 100Ah battery to the ACC cable on the hardwire kit when the car turns on and to cut the power when the car turns off. I wired the ACC and BATT cable of the HWK together and connected them to the battery for now. This means dash cam will just stay on constantly and not go into parking mode.

Here's some photos. I bought a steel battery tray to serve as the base. I wanted the battery to go into a container of sorts, so I bought a group 31 battery box. If I could have found a decent metal box, then I would have just bought a metal box for it. The battery box is a bit too long for the tray, so the rubber helps raise the box above the lip of the tray. I'm using straps right now to hold the tray in place.

I'll probably replace the straps by screwing the tray onto a piece of aluminum sheet. I'll then find some type of hardware to attach the sheet metal to the same metal rings the straps are attached to. Also, I have a piece of rubber protecting the straps from the tray, but I don't anticipate keeping the strap setup for too long. I'll probably end up doing away with the rubber strips as soon as I can find some suitable aluminum blocks to attach to the tray.





I have a couple of pieces of rubber sitting between the straps and the battery box.



I drilled two holes in the bottom of the battery box for the threaded rods of the tray. The angled part of the rods poke through slots on the side of the battery tray. The rubber strips help align the battery box with these slots as well. The tray came with some brackets that fit over the slotted rods, but they were too tall and I couldn't put the cover of the battery box on with them installed. I cut and drilled a piece of aluminum to size as a replacement to the brackets which hold the battery in place. The rods, piece of aluminum, and battery help to keep the battery box attached to the metal tray.. There's a washer and wingnut on each threaded rod. The threaded rods are just a tad bit too high for the battery box lid to close completely, so I'll need to put some additional material under the battery box to lift it a little bit higher.




Here's the temporary install of the 12AWG cables that I ran to my dash cam. I fused each side of the wire since I wasn't using the vehicle chassis for ground. I'll move the 12 AWG cables to a distribution block once I install the DC/DC converter. I'm thinking about replacing the current piece of aluminum with a wider piece that will give me a convenient place to mount the distribution blocks and the 40 amp MEGA fuse for the LiFePo4 battery. I plan on attaching two pieces of aluminum to the bottom of the batter tray that will extend out towards the open end of the trunk. From there, I'll attach some angle brackets that I will use to mount the DC/DC charger.



Here's the box with the rest of the stuff in my trunk. Eventually I might take the cart and emergency roadside kit out of my car. This would allow me to center the battery box in the back of my trunk right behind the seats. The stuff in the emergency road side kit I could put either in the compartment below the trunk where the spare tire is or in the storage bin.



I'll post some more pictures when I have the DC/DC charger mounted along with the distribution blocks.

 

[Nigel]

It appears the ACC and battery wires on the Viofo HK3 hardwire kit need to come from the same voltage source in order to work properly.

Both sources will need their GND connections connected to the car earth/chassis. The I would expect the ACC could come from a different source to the power.

The ACC can't power the dashcam, it only selects parking|normal modes, the dashcam will always need power on the BAT connection before it will turn on.

 

[petepete]

it has now become apparent some motorhome and boat companies are linking lifepo4 in tandem with lead acid batteries....
this keeps the lead acid at the lithiums 13,2v optimal float charge for lead and the lithium does the general work and the lead kicks in on high loads as voltage drops....
obviously when you run the vehicle the lithium charges fast and you get all the advantages of lead acid and lithium combined...
i ve not tried it yet...
using 4 cameras i measured the current draw 2x mobius 2 x0806 and found it to be only 0.51ah when screens timed off the 0806s.
driving 85 miles a day and a 6ah current draw on cameras overnight 12 hours i concluded i dont need a battery backup.

 

[thomas-dash]

I’m one step closer to be finished with this. I routed the 6AWG cable through the firewall. Unfortunately, I broke a bolt to the wiper motor, but I think it’s stable without it. The windshield wipees are working bust fine without it. At some point in the future I might extract it and put a replacement bolt in, but I’m not in too much of a rush to do so.

@petepete Aren’t they loweringthe life span of the lifepo4 battery by doing that? Seems like if the lifepo4 is full and you you keep on charging it while driving, then you would potentially degrade it.

I already bought the DC/DC charger, do I’m going to stick with it.

 

[petepete]

I’m one step closer to be finished with this. I routed the 6AWG cable through the firewall. Unfortunately, I broke a bolt to the wiper motor, but I think it’s stable without it. The windshield wipees are working bust fine without it. At some point in the future I might extract it and put a replacement bolt in, but I’m not in too much of a rush to do so.

@petepete Aren’t they loweringthe life span of the lifepo4 battery by doing that? Seems like if the lifepo4 is full and you you keep on charging it while driving, then you would potentially degrade it.

I already bought the DC/DC charger, do I’m going to stick with it.

na...
thats an internet mith born out of ignorance..
the lithium on direct alternator charges to zero amps or its bms overvoltage setting of 3.65v or 14.6v ( i have solar conected all time so it varies which stops the charging)
once tripped it sits there doing nothing till it drops to reset voltage which i ve set to about 13.4v

 

[thomas-dash]

Both sources will need their GND connections connected to the car earth/chassis. The I would expect the ACC could come from a different source to the power.

I'll have to test this out. How does the current flow work with two batteries? Does current just return to the closest battery? If my dash cam is pulling 0.50 amps from the lifepo4 battery, and has a ground connection closer to the starter battery, does that 0.50 amps return to the starter battery and a different 0.50 amps that would normally return to the starter battery return to the lifepo4 battery? It doesn't seem like the electrons from the lifepo4 battery would know to return to the lifepo4 battery.

 

[Nigel]

It doesn't seem like the electrons from the lifepo4 battery would know to return to the lifepo4 battery.

I guess they don't know, however assuming that you have the GNDs of the two batteries connected and do not have the +V connected in any way, there will be no voltage to push the electrons from the lifepo4 battery towards the car battery. Electrons will only move if they have something pushing them, you need a full circuit.

Remember that the electrons actually flow from the -ve to the +ve, so the shared -ve has electrons from both batteries sitting in it, any of those electrons could head towards the lifepo4 +ve at around 1 cm per minute, but they will be replaced by ones from the lifepo4 -ve, otherwise the lifepo4 -ve would be at a different voltage to the car -ve and some electrons would need to flow from the lifepo4 -ve to the car -ve to restore the balance.

The ACC is just going to turn on a transistor, doesn't matter if those electrons are traveling around a different circuit to the ones providing the camera power.

 

[SawMaster]

For cam operation with a HWK connect "acc" to appropriate car circuit, connect "batt" to auxiliary +, connect ground to both car ground and auxiliary -. Cam will be powered only by auxiliary battery but will switch in and out of parking mode properly.

The BMS for the auxiliary battery should control it's charging with the car doing it's usual for the car battery.

On those fuses, I'd look with magnification to see if there are any scratches where a nut, washer, or terminal connected as a better indicator of new or used instead of fuse terminal color. And even if used, as long as they spec out correctly I wouldn't be worried about them; they would 'blow' to open circuit if overloaded in a past life so used or new would be the effectively the same except for product description.

Phil

 

[thomas-dash]

I crimped my first 6AWG cable today and it didn't go very well. I ended up binding the lower die and the crimp wouldn't disengage when I released the hydraulics. I had to drill out the lug to get it to release. I tried to avoid drilling into the die, but I ended up drilling a little bit on the side. Fortunately, the set comes with "plus" sizes, so there was a 6+ die which sits between a 6 and a 4 size wise.





The one on the left is crimped with the 6+ AWG die and the on the right is crimped with the 4 AWG die.

 

[thomas-dash]

I have the ground cable ran to the chassis ground on my car now. Tonight should be the last night I have to remove the trim inside my car for a long time. I'm super excited about that. Now I need to finish crimping cables, make a mount for the Victron DC/DC charger, install the fuse boxes and fuses, and install the positive and negative distribution blocks. I feel like I'm pretty close to having this project wrapped up.

The dash cam has been running off the lifepo4 since 1/5/22. The dash cam was disconnected a total of 10.75 hours since then, for a variety of reasons, but the lifepo4 battery has powered the dash cam for about 182 hours now, which is about 7.5 days. The battery voltage was 13.0V tonight which roughly corresponds to 30% SOC according to the AmpereTime manual. I currently have the hardwire kit voltage cutoff set at 11.8. According to the SOC table from the manual 12.8V corresponds to 10% capacity and 10.8V corresponds 1% capacity. 1% is the recommended low voltage disconnect voltage.

 

[SawMaster]

Liking your progress and results! Hoping to do something similar one day...

Phil

 

[thomas-dash]

I'm on the home stretch now. I mounted the victron DC/DC charger and distribution blocks today. The only thing left to do is wiring everything together. Here's some more pictures. The first one shows the 3/8" wire loom I added to the 6AWG cables to give them some protection. The two 12 AWG cables are sitting in 1/2" wire loom, but you can't see it as it's sitting right below the floor mat/cover.



I decided to mount the distribution on the back of the aluminum pieces I cut for the charger. The holes to the right and left of the distribution blocks are where the screw holes for the charger. The holes on the bottom are where the aluminum pieces are attached to horizontal aluminum pieces with angle brackets/corner braces.



The side the Victron charger will be mounted on. The piece of aluminum on the right actually is mounted on the left and vice versa.



Here's the vertical aluminum pieces mounted to the horizontal ones. The horizontal ones are bolted to the battery tray. I used the existing holes on the batter tray and cut two pieces of aluminum to use as washers since the battery tray holes are too big for the #10-32 screws I am using.



Here's a side view.



A picture showing the charger mounted to the vertical aluminum pieces.



A veiw from the top. I drilled the holes for the distribution block to align with the gaps in the charger heat sync.



A side view.



Here's the bottom of the horizontal pieces. I countersunk them to make the screws sit flush with the aluminum pieces. If I was starting from scratch, then I think I would used just a solid piece of aluminum sheet metal and buy a jigsaw to cut it to shape. I then could have bolted found some type of hardware to bolt it to the same attachment points I'm using with the straps. I stuck with the flat bar aluminum because it's wasn't too much to cutting with my 6" hack saw.



Same thing as a picture in a previous post. I put some rubber down which raises the battery box to allow the J hooks to align with the slots in the battery tray.

 

[thomas-dash]

Here's the battery box with the lifepo4 battery inside of it.



A picture showing the battery and charger in relation to the rest of the trunk.



A view of the trunk with everything else in it.



The battery is current at 12.75V which corresponds to less than 10% SOC. I think it might have another 4 - 5 days before it hits the HWK cutoff voltage of 11.8V, but we'll see.

 

[thomas-dash]

I accidentally ran the battery empty. I went to drive my car this morning and the dash cam was off. The battery voltage was at 9.49V or something close. I'm not sure why the HWK didn't turn off the camera at 11.8. The only other thing I can think of is the HWK was still drawing power after turning off the camera and that was enough to drain the battery all the way.

I "finished" installing "all" the cables, fuse boxes, and fuses. The DC/DC charger is working and is charging the battery. I've spent about 30 minutes driving around today. The Victron was drawing about 20Amps when I measured it with a clamp meter and the battery was pulling 18 amps when measured with clamp meter as well. I completely forgot about installing a relay to turn the Victron charger off when the car turns off. It draws about 0.18 amps with the charger, so I think it would take roughly about 30 hours of not driving for it to pull the starter battery voltage down to 12.2V. This is based on my dash cam drawing about .40 amps and taking about 15 hours to hit the HWK voltage cutoff of 12.2.

My initial searches didn't turn up a relay that could support 6AWG cable. I did find a post on some forum saying that with heavier gauge cable you have to start using a solenoid instead of a relay. If I install the solenoid/relay by the factory fuse box, then that would save me from having to run an ACC cable all the way to the trunk of my car.

Here's the fuse box in the engine compartment.