Alternator Ground - what is the best location?

[buddyseattle]

Greetings all,

I've appreciated all the information and wisdom on this board over the years.

Recently I've used it to help figure out the best way to upgrade systems prior to adding solar and Lithium Batteries.
I am ready to start the installation of a 150A Balmar Alternator, Regulator and Pulley Kit along with a Victron Orion DC to DC charger for the starter battery.

I will upgrade wiring, add fuses, and eliminate the old Battery combiner and the Digital Echo Charge.
I plan to wire directly to the House batteries from the alternator.

Where should I run this ground to?
The ground from the Alternator is undersized so I will upgrade this as well. It currently runs to a ground point, along with some other connection on the engine block about 16" away. Then a larger wire runs to a Ground block near the battery switches and then it connects to the ground switch where it also connects to the house bank ground here.

It seems like there are a few options:
1 - Stay on the engine block terminal
2 - Go to the House bank ground terminal on the Shunt about 5' away?
3 - Go to the ground black about 15' away?

What do you suggest for best performance and safety?

I spent hours today chasing and following wires to understand the system and I think this is the last question to answer before digging into the installation. Any other advice on the project is welcomed!

[Charlie-Bravo]

There are many greater electrical minds around here than mine, but, you could test your potential grounding points for their resistance, they will probably all be similar, with the exception of the one 15’ away which might be a smidge higher due to its cable length. 
If they all read about the same then the choice comes down to convenience and a tidy install, the less joins and cable in everything the better.

Sounds like you have a ground circuit isolator switch, so have many Jeanneau boats, but I wait for the real reason for having one to come along.
Others I believe have disconnected that switch and then wired it to the positives of house and engine battery as an emergency ‘jump lead’ link, I like the idea of just throwing a switch to jump start , and it disposes of the jump leads I have ….. but have never used.
Could be another modification on safety grounds.

CB

[dbostrom]

Seconding Charlie-Bravo.

Sounds like a great setup. You're going to love those batteries.   [it's still a process of adjustment, "no need to obsess over batteries." And all the staging voodoo-- gone!]

[Trevor]

Hello buddyseatle,

That is a pretty serious alternator you are installing and with the lithiums you may well see it really deliver the rated current. I think that may be a Series 6 Balmar alternator with an isolated ground. In that case it may be wise to use heavy cable to attached that isolated ground straight to the engine block. The reason is the engine block represents a very good path to the negative side of the batteries becasue it requires a good path for the starter motor. The starter motor pulls a lot of current instantaneously when first engaged. A very solid ground return path is required for this to be successful and that is a aprt of the original wiring.

I agree with CB that the ground isolator is in my view just another component that can cause voltage drop in the system when heavy currents are concerned.

The Victron Orion is good for handling the starter battery charging. Please remember that the terminal voltage of the Lithiums stays quite high and so the Orion my never switch off. It has engine run detection and those voltages are programmable but when Lithium batteries are used to charge AGMs, that engine detection may remain on always. That may be your plan however and it is quite a good plan.

Also, the lithums do present a very low resistance load to the alternator for nearly all of the charge cycle. They do not surface charge like lead batteries which taper off the charging current quite quickly easing up on the alternator load. Victron have a youtube video showing what can happen for conventional alternators charging Lithium batteries. I'm not sure what Balmar say about this but it is worth mentioning that this constant high load for large Lithium banks can really test the thermal capacity of high current alternators. It may be worth ensuring that the Balmar external regulator has a working alternator temperature sensor connected to ensure the alternator has some protection.

Good luck...it is an exciting setup and will change your life!

Regards,

Trevor....

[mic98034]

I just saw your post about your alternator and Lithium battery upgrade. I have installed a similar setup. I wanted to mention a couple of points for anyone considering same:

- it sounds like you are charging your House (lithium) batteries directly from the alternator. This is good and will use all the current your new alternator can provide. But it is very important that you use the temperature monitor feature on the voltage regulator to prevent cooking your expensive new alternator.

- If there is not provision for the batteries to shut down the alternator before the BMS disconnects the batteries due to a fault condition (ie. over voltage) then it is important to have an "alternator protection device" connected to the alternator. Sterling Power and Balmar make them.

- For lithium batteries, I VERY highly recommend that you consider a voltage regulator that monitors charge current in addition to voltage. When approaching fully charged a lithium battery's voltage will rise very rapidly, possibly causing an over voltage condition. By also monitoring the current going into the battery, better control over the entire charge cycle is achieved. Wakespeed and Electromax sell VRs with this feature. I installed a WS-500 and have been very happy with it.

PS. As long as you have a good solid electrical connection between the alternator, engine block and negative bus bar I don't think it matters if the Alt-neg is connected to the engine block or the negative bus bar. FYI, I have connected all of my major negative cables (including the alternator and engine block) directly to a central negative bus bar. I try to stay any from daisy chained electrical connection paths as much as possible. But 15', twice, is a lot. My distance from alternator to neg bus bar is less than 4'.

-mic