LDV Convoy Minibus. Question about Jump Starting (Dual Batteries). Any experts?

Frank_Sebem

Hi all

This is a question that started out as an innocent conversation in the Pub last night. Now it has turned into a £100 Bet, with about twenty different people giving their views. It has now turned into a £100 bet.So, I suppose this thread will SAVE someone £100.

Here goes...

My mates Sister is a member of a Dance Troupe that use an LDV Convoy Minibus to take them to comps etc. Yesterday they came to the van to find the Battery had gone flat. So, they lifted up the Bonnet to find 2 batteries next to each other. So one of the guys attached Jump leads to the Outer battery (the one closest to the wing).

This is when it all the arguments started...

A guy in the Pub said he should of connected the Jump leads to the inner Battery (the one nearest the Engine Block). Then another guy jumps in and starts saying it doesn't matter which battery you connect the leads to because they are connected, similar to a Fork Lift that has lots of connected Batteries. Then someone else piped of saying that the inner battery is only for the lights in the rear of the Minibus and takes a trickle charge from that main battery. Then someone said that while both batteries appear the same they have different Amperages etc?????

After 25 minutes of the Jump Leads being connected to the OUTER battery the van started, but the bet is now this..

Does it matter if those leads would of been connected to the inner Battery for 25 Minutes? (Would the Van of still started?)

Can anyone clear this up and solve this £100 Mystery.?

Does it matter which Battery you connect the leads to?
Are the Batteries different?

Help.............................

espresso

Not enough information provided. It depends on how the aux battery has been connected.

There should be an isolator fitted between the two batteries to prevent the main starter battery from fully discharging when the engine is not running and the aux battery is the main supply. This could be an automatic voltage sensing electronic switch that controls when the aux battery is connected and charged or a simple solenoid that connects the aux battery when the engine is running.

If the two batteries have simply been connected in parallel to increase the capacity, then it makes no difference which battery the jump leads are connected to.

The main battery may simply need replacing or the problem may be the charging system, which will charge both batteries.

scheming_gypsy

leave the lights on overnight and then try the jump leads on the other battery.

pitkin2020

they are connected in series if they are both for the engine so it shouldn't matter. We actually took the 2nd battery out of our van and replaced it with 1 decent battery. The 2nd battery usually is there for help with starting especially on cold mornings etc but its far more economical to buy one extremely good battery than 2 average ones.

marlot

pitkin2020 wrote: »

they are connected in series if they are both for the engine so it shouldn't matter. We actually took the 2nd battery out of our van and replaced it with 1 decent battery. The 2nd battery usually is there for help with starting especially on cold mornings etc but its far more economical to buy one extremely good battery than 2 average ones.

That would only work if they're connected in parallel.

There are two alternatives:

In parallel, two 12v batteries will give 12v, but can supply it at a higher current than one battery on its own. My landcruiser does this.

In series, two 12v batteries will give 24v, but at the same current that one battery would give. There are landcruisers which do this too!

Many commercial vehicles have 24v circuits. I don't know whether an LDV is 12v or 24v.

espresso

pitkin2020 wrote: »

they are connected in series if they are both for the engine so it shouldn't matter. We actually took the 2nd battery out of our van and replaced it with 1 decent battery. The 2nd battery usually is there for help with starting especially on cold mornings etc but its far more economical to buy one extremely good battery than 2 average ones.

All LDV Convoys have 12V electrics see here so the two 12V batteries will not be connected in series as that would give 24V.

esmerobbo

Earth to engine block live to the live on the battery directly connected to the starter.

pitkin2020

marlot wrote: »

That would only work if they're connected in parallel.

There are two alternatives:

In parallel, two 12v batteries will give 12v, but can supply it at a higher current than one battery on its own. My landcruiser does this.

In series, two 12v batteries will give 24v, but at the same current that one battery would give. There are landcruisers which do this too!

Many commercial vehicles have 24v circuits. I don't know whether an LDV is 12v or 24v.

I know it was either series or parrallel lol

pitkin2020

espresso wrote: »

All LDV Convoys have 12V electrics see here so the two 12V batteries will not be connected in series as that would give 24V.

I did mean parallel as mentioned in last post, my error lol

colino

They will be in parallel (as above) but must either be on a split charger (relay controlled) or left for a very long time or had no alternator for some time to be flat. The whole point of having double capacity is to take account of high demand when on multi-drop duties etc.
While "best practice" is to connect the positive pole of the slave battery to the main starter feed and the negative to the block - to prevent trying to divert power to the dead original - reality is if the other vehicle has a good charge, battery to battery will be good enough.

gilbert_and_sullivan

You'll never get agreement about jump lead connections, in car strorage compounds where they jump start dozens of vehicles every day, the mini buses used by the ferry drivers have permanently connected jump leads with the crocodile clips attached to a rubber wrapped bar when not in use.

One of the ferry drivers will simply touch the contacts to any of the battery terminals if the flat vehicle is 12v and a mate will start the flat car, no finesse, no worries about sparks or shorts or spiking, simply get on with it no time for mucking about.

What i'm interested in knowing here was this LDV van completely flat, if so did the one set of leads start it?...in my experience it usually takes 2 or sometimes 3 sets of good quality leads to jump start vehicles of this type, 12v vans and 4x4's, if they are completely drained, where a 24V 14 litre truck will happily fire up with one set, most odd.