Where to attach booster cables?

[ColinB]

The battery in my car is now over 9 years old and whilst it still seems OK, I'm going to invest in a lithium booster pack (Noco or similar) ready for when the car won't start. According to the handbook, the positive cable needs to be attached to the battery, and the negative (-ve) cable needs to be attached to an earthing point over on the other side of the engine compartment. But I can't find a booster pack with cables that long. I understand that the -ve cable can be attached to any earth point, but I'm not actually sure where that would be ... all the easily accessible locations closer to the battery seem to be either very flimsy or plastic. So, if there's anyone with experience of using a booster pack, where exactly did you attach the -ve cable? Or does anyone know of a pack with cables long enough to reach the "official" earth point?

[UKjim]

There are quite a few metal brackets/ bolts etc quite near the battery, just try attaching the negative terminal to any of them & if the battery pack works it’s a good enough earth point.

[Steve_M]

If it’s a booster pack with an on/off switch, then you can just attach it to the positive and negative terminals directly on the battery. The reason to connect to an earth point on the engine as this is the final connection point which may spark with jump leads, so any spark is away from any flammable battery fumes. A switching booster is not live when connected so no spark.

[ColinB]

If it’s a booster pack with an on/off switch, then you can just attach it to the positive and negative terminals directly on the battery. The reason to connect to an earth point on the engine as this is the final connection point which may spark with jump leads, so any spark is away from any flammable battery fumes. A switching booster is not live when connected so no spark.

Understood, but isn't there also something about NOT bypassing the battery sensor on the cable from the negative terminal? Hence the need to use an earth point, to ensure current passes through the sensor?

[His_name_is_robertpaulson]

Buy a CTEK MX10 battery charger, it will pay for itself after one use

[ColinB]

Buy a CTEK MX10 battery charger, it will pay for itself after one use

Not practical for owners who do not have private off-road parking.

[aphybrid]

There are quite a few metal brackets/ bolts etc quite near the battery, just try attaching the negative terminal to any of them & if the battery pack works it’s a good enough earth point.

Should the negative connection be made on the engine block rather than any bracket attached to body?

[Steve_M]

Understood, but isn't there also something about NOT bypassing the battery sensor on the cable from the negative terminal? Hence the need to use an earth point, to ensure current passes through the sensor?

Just for Jump starting it would not matter, if you are charging the battery, that's a different matter and can normally just put it on the body side of the senser.

[jazzaro]

The battery in my car is now over 9 years old and whilst it still seems OK, I'm going to invest in a lithium booster pack (Noco or similar) ready for when the car won't start. According to the handbook, the positive cable needs to be attached to the battery, and the negative (-ve) cable needs to be attached to an earthing point over on the other side of the engine compartment. But I can't find a booster pack with cables that long. I understand that the -ve cable can be attached to any earth point, but I'm not actually sure where that would be ... all the easily accessible locations closer to the battery seem to be either very flimsy or plastic. So, if there's anyone with experience of using a booster pack, where exactly did you attach the -ve cable? Or does anyone know of a pack with cables long enough to reach the "official" earth point?

Connect the negative cable to the part pointed in green or in every metallic part of the engine block or gearbox, not directly in the negative lead.
Bypassing the BMS, the car will start but it will cause some troubles to the start&stop system, since the system will lose data about the real quantity of charge. 

[ColinB]

Connect the negative cable to the part pointed in green or in every metallic part of the engine block or gearbox, not directly in the negative lead.
Bypassing the BMS, the car will start but it will cause some troubles to the start&stop system, since the system will lose data about the real quantity of charge.

That makes sense, thank you (although I don't have a green arrow printed on my battery ). I wonder why the handbook doesn't say that, rather than directing you across to the other side of the engine? Maybe that's "belt & braces" advice associated with the risk of explosion if the battery is venting. But, as pointed out earlier, if the powerpack is switched that's not an issue.

Now to order the booster pack.

[jazzaro]

Maybe they send you to the left part of the engine to reduce the risk of sparks and explosions, or the risk of shorts if you touch one clamp with the other, or the risk of damaging the BMS sensor, or because the resistance is a bit lower if you directly connect the clamp to the engine and not to the BMS .. to be honest I don't know. In this techical bullettin you will find the tip about the correct charge mode for hondas with BMS, https://www.civinfo.com/attachments/46-pdf.294254/ page 3-4, the sensor is slightly different but we can easily understand the reason under the method.