PVC leisure battery isolation.

[Happy Jack]

Hi all.
Slightly different to the post from Dee 101 earlier.
I have 320A solar going through Victron 100/30 into 190A of AGM batteries. These feed various items through fuse boxes including fridge/freezer, Maxxfan deluxe, Diesel hob & Diesel heater as well as lighting etc. Also have hook up and Sargent px100 charger just in case.
However, I have the leisure system totally isolated from the van.
I see that if one of the + cables were to rub through and touch bare metal of the van, then bother can occur.
My query is :- What possible bother, and could I simply run a cable from the negative of the leisure batteries to a suitable earth point in the van body.
Thanks,
Happy Jack.

 

[Mikeco]

I have 2 separate cables earthing the leisure battery to the chassis, I thought that that was standard practice.

 

[Happy Jack]

Please state why you thought it is standard practice and I guess 2 cables are for " belt and braces" .

 

[peterc10]

I have 2 separate cables earthing the leisure battery to the chassis, I thought that that was standard practice.

I don't think that is standard. If you want to measure the amps going in or out so that you know the state of your batteries you will need to set it up so that all the negatives go through one shunt to earth.

 

[Mikeco]

Please state why you thought it is standard practice and I guess 2 cables are for " belt and braces" .

No idea, but I know that vehicle batteries are earthed so common sense told me to do it.

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[Happy Jack]

Pertec, I think you are replying out of context.
my query has nowt to do with battery monitoring.

 

[peterc10]

Pertec, I think you are replying out of context.
my query has nowt to do with battery monitoring.

I wasn't replying to your post. I was replying to the post from Mikeco, as can be seen by the fact that I quoted his post, not yours. My post explained why that was not correct. You may not want to know what state of charge your leisure batteries have, but a lot of us do.

 

[Mikeco]

I wasn't replying to your post. I was replying to the post from Mikeco, as can be seen by the fact that I quoted his post, not yours. My post explained why that was not correct. You may not want to know what state of charge your leisure batteries have, but a lot of us do.

Hang on, I was only earthing my batteries not trying to find out how much I was using, anyway I can tell what’s going in through the Renogy Solar control, unless I’m doing that wrong as well.

 

[Just smiffy]

Well This is a negative thread isn’t it……

 

[peterc10]

Hang on, I was only earthing my batteries not trying to find out how much I was using, anyway I can tell what’s going in through the Renogy Solar control, unless I’m doing that wrong as well.

No good knowing about the amps going in if you don't know what are going out. If the solars are putting in 5A but you are using 10A you are running down your batteries.

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[Mikeco]

No good knowing about the amps going in if you don't know what are going out. If the solars are putting in 5A but you are using 10A you are running down your batteries.

I never knew that. but give me a bit of credit having had leisure batteries in Caravans and motorhomes for 50 years. End of post.

 

[Happy Jack]

Pertec, forgive me if I'm wrong but I am branspanking new to the forum. I thought Mikeco was replying to my post and for you to reply to one of his within mine would be wrong?
Anyway, still not got an answer as to "Is it OK to simply connect the negative of the leisure battery directly to a suitable earth point of the van, or what can happen if not earthed.

 

[stevewagner]

Hi all.
Slightly different to the post from Dee 101 earlier.
I have 320A solar going through Victron 100/30 into 190A of AGM batteries. These feed various items through fuse boxes including fridge/freezer, Maxxfan deluxe, Diesel hob & Diesel heater as well as lighting etc. Also have hook up and Sargent px100 charger just in case.
However, I have the leisure system totally isolated from the van.
I see that if one of the + cables were to rub through and touch bare metal of the van, then bother can occur.
My query is :- What possible bother, and could I simply run a cable from the negative of the leisure batteries to a suitable earth point in the van body.
Thanks,
Happy Jack.

In answer to the positive cable touching earth it would blow the battery fuse if you have one. If not it would seriously damage the batteries

 

[autorouter]

It is normal in motorhomes and campervans for the leisure battery negative to be connected to the chassis, in the same way that the vehicle battery negative is. One practical reason for this is that often the leisure battery is charged by the alternator when driving.

A common arrangement is a relay that connects the two battery positives together when the engine is running, and disconnects when the engine stops. For this to work, the negatives need to be connected to the chassis.

Does your leisure battery get charged from the alternator when the engine is running?

 

[autorouter]

However, I have the leisure system totally isolated from the van.
I see that if one of the + cables were to rub through and touch bare metal of the van, then bother can occur.
My query is :- What possible bother, and could I simply run a cable from the negative of the leisure batteries to a suitable earth point in the van body.

Actually, if the leisure system is totally isolated from the van body, then one of the positive cables touching the bare metal of the van would have no effect. However if the battery negative is connected to the van body, touching a positive cable to the body makes a short circuit, which will cause very high current, overheating, melted insulation and possibly a fire. That's why there's a fuse which blows to prevent this.

But with basic precautions this problem can be prevented, so as I said MHs normally have the battery negative earthed to the chassis.

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[Happy Jack]

Autorouter, sorry it took so long getting back to you.
Been busy.
Will be fitting a b2b but was thinking of an isolated type, although they are more expensive.
I could run a cable from leisure battery bank earth to van earth and could then use non isolated b2b.
All my circuits have fuse protection.
Keith