Battery Tender Installation, Light Flicker and Fuel Pump Cycle

[Strike18]

Hey guys, I recently purchased a 2022 mustang GT and was setting up the battery tender using the fuse box as seen in these two pictures. Fuse Box / Ground.

While installing the positive cable to the fuse box the lights flickered a few times and the fuel pump cycled 4-5 times until the bolt was snug. Just wondering if this would have or could have damaged anything? Nothing seems wrong but I'm just probably being paranoid so I thought I would ask...

This is where I got most of the info from regarding this process (not sure where I went wrong):

https://www.mustang6g.com/forums/threads/installing-battery-tenders.73725/

Thanks

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[SSally]

I did this same hook-up to my 2020 GT several years ago. Kind of freaked me out when the lights flickered, etc. I don't remember any negative effects. I have since sold the 2020 and recently purchased a 2022 GT and was reviewing the postings you reference. I haven't added the battery tender yet, and am curious to see what other members have to say to your post.

 

[The Chairman]

Hey guys, I recently purchased a 2022 mustang GT and was setting up the battery tender using the fuse box as seen in these two pictures. Fuse Box / Ground.

While installing the positive cable to the fuse box the lights flickered a few times and the fuel pump cycled 4-5 times until the bolt was snug. Just wondering if this would have or could have damaged anything? Nothing seems wrong but I'm just probably being paranoid so I thought I would ask...
https://www.mustang6g.com/forums/threads/installing-battery-tenders.73725/

I’m guessing you removed/used the nut already holding the red cable to the fuse box? That would create an intermittent contact for all accessories. This would cause the items you mention to flicker/cycle.
I added an additional nut on that post to not have to remove the other one. But what you did shouldn’t hurt anything.

 

[Strike18]

I’m guessing you removed/used the nut already holding the red cable to the fuse box? That would create an intermittent contact for all accessories. This would cause the items you mention to flicker/cycle.
I added an additional nut on that post to not have to remove the other one. But what you did shouldn’t hurt anything.

Yeah I used the nut that was already on the fuse box, next time I'll try using a nut on top and that way the line stays secured. I don't think it harmed anything, mostly just being paranoid I think. I'll take it off in spring and see what happens...

 

[Skye]

Welcome to the forums.

The connections are in the right place.

It reads like you installed the tender while the battery was still connected at both posts? If so, that could cause the conditions you mentioned. If you had disconnected the battery prior and then installed the tender, when you reconnected the battery, the same events would have happened.

When I reconnected my battery, all kinds of gizmos clicked, spun up and powered back on, over a period of minutes.

Anytime I work on anything involving the car's electrical system, I always disconnect the battery first, to help protect car and self.

It does sound like "normal" events and that you did no harm.

If you're not already familiar with the topic, and with the work accomplished, consider a BMS reset.

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

Again, welcome.

 

[Qcman17]

Same thing happened when I did mine as the extra nut I bought to use wouldn't stay on so I used the factory nut by disconnecting it and it of course flickered several times. Spooked me at the time. That was over 3 years ago and never a problem as a result of the flicker. You're fine

 

[tosha]

You should disconnect the battery before doing any electrical work on a car.... well, same applies to any electrical work - always cut the power first. You wouldn't change receptacles at home without first flipping the breaker, right?

 

[Strike18]

Welcome to the forums.

The connections are in the right place.

It reads like you installed the tender while the battery was still connected at both posts? If so, that could cause the conditions you mentioned. If you had disconnected the battery prior and then installed the tender, when you reconnected the battery, the same events would have happened.

When I reconnected my battery, all kinds of gizmos clicked, spun up and powered back on, over a period of minutes.

Anytime I work on anything involving the car's electrical system, I always disconnect the battery first, to help protect car and self.

It does sound like "normal" events and that you did no harm.

If you're not already familiar with the topic, and with the work accomplished, consider a BMS reset.

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

Again, welcome.

Firstly thank you for the warm welcome. This seems like a great forum and community!

I’m definitely going to keep in mind disconnecting the battery next time I fiddle with anything. For that can I just take the negative off the battery or do I have to do both posts?

Also the BMS thread is a great read and I will keep that in my back pocket as well. Thanks for the help and advice, it’s much appreciated!

 

[Strike18]

You should disconnect the battery before doing any electrical work on a car.... well, same applies to any electrical work - always cut the power first. You wouldn't change receptacles at home without first flipping the breaker, right?

Yeah I think I’ve learned my lesson for sure, when I was following the previous thread no one was really having issues and they were doing it to bypass dealing with the battery cover and battery itself. So I guess I was just being a bit naive in the end. Thanks

 

[K4fxd]

when I was following the previous thread no one was really having issues and they were doing it to bypass dealing with the battery cover and battery itself.

The reason for hooking it up in the fuse box is to keep the BMS sensors working with the outside charger.

 

[Skye]

For that can I just take the negative off the battery or do I have to do both posts?

Just the negative cable. The - side of the battery is where the excess of electrons reside, versus the + side.

Keeping one hand free, use another to loosen the cable at the negative post and remove. You'll be fine then.

After repairs and when returning the cable to the post, use one hand when placing the cable back on the post, while keeping the other hand free.

Using a one-hand principle reduces or removes risk of electricity flowing through you and across your chest.

You might see a minor spark on reconnect; that's OK. The clicking and buzzing will occur and then stop once the car has re-energized.

 

[ice445]

Yeah I think I’ve learned my lesson for sure, when I was following the previous thread no one was really having issues and they were doing it to bypass dealing with the battery cover and battery itself. So I guess I was just being a bit naive in the end. Thanks

Nothing is going to get damaged from a temporary inconsistent connection, luckily. As far as why people use the fuse box, it's just to keep the car clued into the battery charging process. There's an inductive current sensor on the main ground cable to the battery that measures amp draw, and the car uses this to determine its charging strategy and infer battery charge level. If you connect directly to the battery, it has to figure it out the long way which requires sitting for 8+ hours.

 

[Johnny Rockit]

What size nut do I need for the tender connection on the positive terminal? (I would

guess my missing 10mm tools will be required). Is it a dealer part?
Also, my battery was replaced at the dealership before the sale and the battery cover had only one rubber pin(?) and I lost it when I picked up my ride today.

ETA: Installing my tender wires tonight. There is a lot of good info in this thread and the others that are linked. This site is a great place to learn the answer to any question regardless of topic.

 

[pt's21]

I connected my charger/tender cable to the battery clamps using the clamping nuts/studs. Battery never lost connection in any manner.

 

[gww52]

M6-1.0 nut required.

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