Vehicle batteries

[Kittyhawk]

This is a picture of the two start batteries in my truck. The Ford one is the cranking battery and Delkor one powers all the stuff associated with the ignition switch.
They are situated in a lidded metal box under the driver's seat. Access is a pain in the bum as it necessitates the complete removal of the seat together with all the associated sliding and rotating seat mechanisms. Because the truck is idle for extended periods I would like to be able to use a battery charger on them once a week to keep them pressed up. The batteries share a common earth but are otherwise independent of each other. My plan is to install three wire tails through an existing hole in the battery box, one to the earth terminal and the other two to the positive terminals to which I can connect my charger without all the palaver of removing the seat. Connection points suitably insulated and isolated from each other of course.
The problem is that everything I read stresses the point that lead acid batteries may only be charged in open, well ventilated spaces which is not the case with their enclosed location under the seat. This doesn't make any sense to me as the truck has a big beast of an alternator which puts out loads of power. Why is it ok to charge batteries in an almost airtight metal box via an alternator when driving but not ok to charge in an enclosed box via a battery charger when stationary?

 

[niall Y]

Possibly because the vehicle is in motion when the alternator is charging the batteries and the air that is getting in is ventilating the compartment? As I understand it, it's the hydrogen and oxygen given off that is the problem. Perhaps allow for some additional ( forced) ventilation' just to be safe.

 

[Terry - Somerset]

A possibility - batteries being charged give off hydrogen. When mixed with oxygen it creates potential for explosion.

The steel box in which the batteries are currently housed (I assume) is full of battery, not air, and being almost airtight, there will be little oxygen so the risk of explosion is limited.

 

[John Brown]

I think you'll find that they give off oxygen as well..
However, I take the point made by the OP, the alternator will charge the batteries under normal circumstances, and while they're in that same, confined space.

 

[Agent_zed]

are you sure there isn't a connection somewhere for charging? I've seen it on some cars. I think from memory my bmw had this as the battery was in the boot but if it was flat you couldn't open the rear door, so there was a connection under the bonnet to attach charging cables etc.

 

[Spectric]

If running wires from the batteries to a charging point then fit fuses to protect the wiring in case they get shorted. You say two batteries that are independant, how are they charged on the vehicle ?

If they are going flat is this due to self discharge within the battery or because of some drain on the vehicle ? Rather than charging could you not fit an isolator switch in that common ground ?

If the batteries are charged and all you are doing is applying a top up then there should be minimal gas produced, hydrogen from one electrode and oxygen from the other electrode. When you replace these batteries, rather than use wet cells used absorbed glass mat (AGM) batteries and Hawker Odessey are very good.

 

[Kittyhawk]

If running wires from the batteries to a charging point then fit fuses to protect the wiring in case they get shorted. You say two batteries that are independant, how are they charged on the vehicle ?

If they are going flat is this due to self discharge within the battery or because of some drain on the vehicle ? Rather than charging could you not fit an isolator switch in that common ground ?

View attachment 183038


If the batteries are charged and all you are doing is applying a top up then there should be minimal gas produced, hydrogen from one electrode and oxygen from the other electrode. When you replace these batteries, rather than use wet cells used absorbed glass mat (AGM) batteries and Hawker Odessey are very good.

There is a charging point under the bonnet - battery charger positive to it, negative onto the engine block but this only charges the cranking battery. The other start battery provides power for all the associated auxiliary circuits, dashboard lights, indicators, keyless entry etc. As I understand it, the batteries are independent of each other but joined via a relay during engine start. Once the engine is running the cranking battery is isolated again and all electrical functions carried out by the auxiliary battery. If the auxiliary battery is down from leaving doors open, using the radio and so on then there is insufficient power in it to activate the starter solenoid even though the cranking battery is full. Seem excessively complicated to me. I don't know how the batteries are charged when the engine is running, either in tandem or sequentially. But with the vehicle not running, batteries have to be charged separately with a battery charger

 

[Kittyhawk]

Oops!
Its the middle of the night here, and I had a vague recollection that I'd seen something...
So I went back out to the truck with a torch and yes, hard to see but both batteries are ventilated by a small plastic tube that comes from the top of the case and down through the bottom of the battery box. I guess I'm safe from explosions after all.

 

[Jameshow]

How about a small solar panel which is plugged into a constantly live cigarette lighter socket or the customer electrical points on the side of the seat if it has one.
My transit van does - you truck might do what model is it?

 

[Spectric]

Seem excessively complicated to me. I don't know how the batteries are charged when the engine is running, either in tandem or sequentially.

It really makes no sense at all, if the starter motor is 12 volts then why not just both batteries in parallel so they work as one large capacity battery. The only reason I could think of is to ensure that the cranking battery is not discharged so you can always start it but that goes out the window because of the starter relay is powered from the non cranking battery. Have you looked for the wiring diagram for the vehicle as it might give you a clue as to why it is like this ?

Is it diesel or petrol and if diesel what type of injection ?

 

[Jameshow]

It really makes no sense at all, if the starter motor is 12 volts then why not just both batteries in parallel so they work as one large capacity battery. The only reason I could think of is to ensure that the cranking battery is not discharged so you can always start it but that goes out the window because of the starter relay is powered from the non cranking battery. Have you looked for the wiring diagram for the vehicle as it might give you a clue as to why it is like this ?

Is it diesel or petrol and if diesel what type of injection ?

They are separate and controlled by the ECU I expect that's what I think happens on my 16 plate transit.

 

[Kittyhawk]

They are separate and controlled by the ECU I expect that's what I think happens on my 16 plate transit.

Yes. The truck is a 2013 Ford Transit Mk.7, 2.4L turbo diesel, long wheel base, duals on the back.
The twin battery setup is an option but is not covered at all in the owners handbook.

How about a small solar panel which is plugged into a constantly live cigarette lighter socket or the customer electrical points on the side of the seat if it has one.
My transit van does - you truck might do what model is it?

I note that the lighter sockets around the dashboard are always live so your solar suggestion sounds excellent for trickle charging the auxiliary start battery. Going to look into that today. Thank you.

 

[Richard_C]

Battery chargers are very different from the ones I used back in the 70s - 12v, crocodile clips and a single charging rate. Now most have a trickle charge setting, I know someone who has a classic car which is kept more or less permanently on a maintenance charger which has fancy electronics beyond my understanding. So, if solar doesn't work have a look around at "modern" mains chargers.

 

[Kittyhawk]

Battery chargers are very different from the ones I used back in the 70s - 12v, crocodile clips and a single charging rate. Now most have a trickle charge setting, I know someone who has a classic car which is kept more or less permanently on a maintenance charger which has fancy electronics beyond my understanding. So, if solar doesn't work have a look around at "modern" mains chargers.

An auto electrician said to me once that batteries generally don't just die - they are usually murdered. so I try go look after them and I have a fairly good three stage charger that does the boost, absorption, float thing.

 

[Fergie 307]

How about a small solar panel which is plugged into a constantly live cigarette lighter socket or the customer electrical points on the side of the seat if it has one.
My transit van does - you truck might do what model is it?

Exactly what I do with my Cherokee, and caravan. Just make sure the panel is connected via a suitable regulator. I just have a roughly 18x6 inch panel which rests on the jeep dash, the caravan has a slightly bigger one permanently installed on the roof. I think go outdoors etc now sell ones with a built in regulator.

 

[imageel]

I think you'll find that car batteries are way more complex than they were years ago - even those fitted to ICE vehicles.
I know my Audi Avant has electronics within the battery itself that one of the in-car computers uses to communicate with it and presumably control it's charge rate, status etc

 

[stuart little]

are you sure there isn't a connection somewhere for charging? I've seen it on some cars. I think from memory my bmw had this as the battery was in the boot but if it was flat you couldn't open the rear door, so there was a connection under the bonnet to attach charging cables etc.

If your 'Beemer' was anything like my Saab was, then no doors could be opened when the battery was dead, neither could the bonnet be opened. The only way, (without causing damage) was to get underneath & attached auxiliary power via the starter motor/battery connection.

 

[stuart little]

I used a 'split charge' relay on my late motorhome, which kept both batteries charged when on 'hook-up.

 

[Agent_zed]

If your 'Beemer' was anything like my Saab was, then no doors could be opened when the battery was dead, neither could the bonnet be opened. The only way, (without causing damage) was to get underneath & attached auxiliary power via the starter motor/battery connection.

thankfully you could still open the main driver door with a key and then open the bonnet. The boot was an electrical switch so would not open with a flat battery. You could drop the seats but then really hard to lift the boot floor to get to the battery, hence the connection point under the bonnet. Some things are too clever for their own good, as it would seem with the setup on the OPs truck.

 

[stuart little]

thankfully you could still open the main driver door with a key and then open the bonnet. The boot was an electrical switch so would not open with a flat battery. You could drop the seats but then really hard to lift the boot floor to get to the battery, hence the connection point under the bonnet. Some things are too clever for their own good, as it would seem with the setup on the OPs truck.

The key wouldn't even work! A neighbour with a Beemer had to break a rear quarter-light to get his door open.