Two battery packs to one fuse???

[knight3136]

Hello everyone,

I'm trying to connect two battery packs which require 10 amps, 12V each . I want to connect both of them to an empty slot on my fuse box of my 2020 rav4. Since each needs 10 amps, I will add a 20 amps fuse on the empty slot with a fuse tap. I would run 14 awg wires from fuse tap to the first battery pack solder an XT60 connector for the first battery pack. I would then connect the 14 awg to a buck booster transformer that will increase voltage 12V at 10 amps and for the remaining 6 feet that would be connected to another buck booster 12V at 10 amps. The output of the second buck booster wlll have another xt6o cable that will connected to the second battery pack. When I connected them it was working. Today I went to startup my car and they weren't charging, I check the apps and it was showing zero voltage and amps for both battery pack. The second battery pack was showing 8V /9.1A but it immediately went down to zero and I got a message saying low voltage. The cars battery was 12.8V, I would like to know if I should go with a 25 amps fuse instead of 20 and why it work at first and then stop working. Any suggestions will be appreciated.

 

[Nigel]

buck booster

What is the purpose of the buck booster? Is it actually connected to the fuse tap as shown?

Might help to know what sort of battery pack you are using?

 

[SawMaster]

If the 20A fuse didn't blow, a larger fuse isn't needed. It's not clear to me what you're trying to accomplish but generally you don't want one converter feeding into another; better to use a single converter capable of doing the whole job by itself. And batteries used in series need to be closely matched.

If you're trying to power cams from the batteries while parked, this isn't the best way to do it.

Phil

 

[knight3136]

I'm connecting cellink neo and thinkware battery packs for dash cams. Buck booster if they get voltage lower lower than 12v then it will increase it to 12 V. There is 4 feet cable connected to the fuse box. I solder XT60 connectors for the first one and cable goes into the buck booster after that the out put of the buck booster sends power at 12v 10 amps for 6 feet to the back of the car that will go into another buck booster the out of the second has XT60 cable that is connected to second battery pack.

 

[knight3136]

If the 20A fuse didn't blow, a larger fuse isn't needed. It's not clear to me what you're trying to accomplish but generally you don't want one converter feeding into another; better to use a single converter capable of doing the whole job by itself. And batteries used in series need to be closely matched.

If you're trying to power cams from the batteries while parked, this isn't the best way to do it.

Phil

What I'm trying to accomplish is to charge the batteries packs while im driving and then has them power the dash cams while the vehicle is parked. The only way to have dash cams running while parked is to have batteries pack. Connecting them to the vehicle directly will drained your car battery.

 

[Nigel]

Buck booster if they get voltage lower lower than 12v then it will increase it to 12 V.

The fuse will always be above 12v if the engine is running, normally it will be around 13.8, so the Buck booster is not required...
Also, the battery packs probably will not charge at 12v, I would expect them to need above 13v before they charge.

 

[knight3136]

The fuse will always be above 12v if the engine is running, normally it will be around 13.8, so the Buck booster is not required...
Also, the battery packs probably will not charge at 12v, I would expect them to need above 13v before they charge.

The battery has two option 5v through cigarette port or 13.8 volt hardwire. I have been able to charge at 12V.

 

[SawMaster]

The Cellink already has the necessary switching and charging circuits (and probably the Thinkware too) and as they're designed to connect to the car's 12V that's what I'd do with them with no buck/boost converter involved. The way you have it now the converters and batteries may not be compatible with each other, especially the battery's voltage sensor circuitry which controls charging. If they're not getting the needed voltage to charge while driving, then you've got problems elsewhere and the converters won't fix that.

Always best to use things as they were designed to be used unless you know as much or more than the engineers who designed them

Phil

 

[knight3136]

ok, tomorrow i will try installing the same way i have it in the picture except i'll remove the buck boosters. But I think due to almost 12 feet of cable i will be running from fuse box to the second battery that the voltage will decrease.

 

[SawMaster]

ok, tomorrow i will try installing the same way i have it in the picture except i'll remove the buck boosters. But I think due to almost 12 feet of cable i will be running from fuse box to the second battery that the voltage will decrease.

Using those wire sizes, the voltage drop won't be a problem.

Phil

 

[Leonauto]

I can suggest looking at another option, according to which scheme you can connect a second battery

BlackVue 750S connect to PowerBank [Plug help]

Hi Dashcam People! I have read in this forum that using a PowerBank could solve my issues when installing a BlackVue Dashcam DR750S-2CH in my Toyota C-HR (Hybrid 1.8) and want to use park mode? The car battery goes low quick (probably due to I don't drive very much and when I do it's normally...

dashcamtalk.com

Perhaps this will help you a little.

There is also a ready-made option: Dual Battery Isolator Kit

Spoiler

VOLTAGE SENSITIVE RELAY - The Automatic 140 Amp Dual Battery Isolator is all you need to charge Two Battery Systems. Voltage Sensitive Relay (VSR) cuts in at 13.3 volts and cuts out at 12.8 volts to ensure your primary battery is always charged and ready to start your vehicle. It's like having two separate power sources for each battery while only having one alternator!

or: Dual Battery Isolator Kit - HORSMILE 12V 140Amp Voltage Sensitive Relay & Wiring Cable Kit, Complete VSR Double Battery Automatic Charger

 

[knight3136]

I found out that i had blown out fuse. I guess both batteries were pulling too much power even though it had a 20 amps fuse. So what I ended up doing was putting in a 25 amps fuse. So far I driven the car 5 times and it has been working. I kept the buck boosters so I can 13.8 volts.