Twin Batteries.

Hi, I am considering wiring two batteries together giving the same 12v but double ah. I am about to convert to veg oil and some of my pre heating is 12v so I dont want to kill the battery and not be able to start it.
I am not too bothered about split chargers rather link the two batteries together.
Can anyone see any issues with this?
Ta

cold comfort farm said:

Hi, I am considering wiring two batteries together giving the same 12v but double ah. I am about to convert to veg oil and some of my pre heating is 12v so I dont want to kill the battery and not be able to start it.
I am not too bothered about split chargers rather link the two batteries together.
Can anyone see any issues with this?
Ta

Click to expand...

you are basically making a large battery, so you can still drain it as normal.

also, you want the same batt, ideally from the same batch and if one bat is a bit dud it'll pull the other down.

however, lots of fords run this setup as standard afaik and it's fine.

You might have to upgrade your alternator because you have to charge two battery's I would just put a split charger in

I would put the same battery on so they match. My existing battery is very new so they should be basically the same.
I wont be discharging too much ah wise so the existing alternator would be good. Its more like you say a bigger battery. I would go for a split charger if I could find one cheap enough.

cold comfort farm said:

I would put the same battery on so they match. My existing battery is very new so they should be basically the same.
I wont be discharging too much ah wise so the existing alternator would be good. Its more like you say a bigger battery. I would go for a split charger if I could find one cheap enough.

Click to expand...

You are answering your own question then. Go for it!

cold comfort farm said:

Hi, I am considering wiring two batteries together giving the same 12v but double ah. I am about to convert to veg oil and some of my pre heating is 12v so I dont want to kill the battery and not be able to start it.
I am not too bothered about split chargers rather link the two batteries together.
Can anyone see any issues with this?
Ta

Click to expand...

Simpler to get the biggest single battery you can fit in. It'll be more reliable.
If you do go with 2 batteries, 2 of the the odessy / optima batteries can be fitted in the battery compartment of a P38. Its tight but manageable. Best to use a split charge circuit and run the aux loads off the non starter battery. The top of the range are T-max, (it allows for manual link up etc..) but a simpler and cheaper solution is available. I run a single dieseltherm as the last boost before injector pump. The rest of my heating is coolant circuit based.

Are you trying to avoid a twin tank setup?

cold comfort farm said:

I would put the same battery on so they match. My existing battery is very new so they should be basically the same.
I wont be discharging too much ah wise so the existing alternator would be good. Its more like you say a bigger battery. I would go for a split charger if I could find one cheap enough.

Click to expand...

you can do it on the cheap if you want. just need some fuses, wire and a decent relay linked to your alt. (15-20 quid for it all)

or a more expensive option with a voltage sensing relay. (add an extra 12 quid)

or you *could* just fit the voltage sensing relay by itself with a couple wires and a fuse. i'm not convinced the 30amp is good enough mind. if the second battery runs too low it could pull more than 30 amps and blow it. So it isn't for fully draining the second bat

Thanks Guys, looks like I will look for a cheap split charger then.
Mark I will be running a twin tank but using solid veg (palm oil) not veg oil. I have done it on a few other vans etc. All the fuel pipes will be run inside coolant pipes but I want to heat the coolant prior to driving so i get a faster warm up. As you know in the dead of winter a 300tdi takes some warming up. I looked at going down the diesel pre heater route but did not like it.

why not a kenlowe hot start and heat exchanger?

The hot start would be same cost as a new battery and heat exchangers are cheap enough and the plus is you are warm when you drive off.

dieseldog69 said:

why not a kenlowe hot start and heat exchanger?

The hot start would be same cost as a new battery and heat exchangers are cheap enough and the plus is you are warm when you drive off.

Click to expand...

good idea, only downside is it doesn't work to well if you park away from a socket. like at work, up in the hills, etc.

Well, I know next to nothing about these cars as I just bought mine last week or so, and only driven it once since. But the fact is, it came with two batteries. Now I guess I nee to find out how they are all wired, as I have not a clue. Judging from the fact that there are two battery compartments, THEY must have known people will use two batteries now and again....

yep mainly for winches etc.

trax said:

good idea, only downside is it doesn't work to well if you park away from a socket. like at work, up in the hills, etc.

Click to expand...

Generally speaking it is not such a problem if left only for a few hours and even over an 8hr shift as it is normally that first cold start in the morning that is the killer as the engine will hold residual heat for a reasonable amount of time after start up and say an 8hr shift, it may only be cool/cold internally after say 2/3 hours and as daytime ambient temps are higher it will not work itself so hard starting.

you could blag work that you have one of them new retro hybrid installs

With the twin tank setup, coolant circuit gets heated on ordinary diesel whilst driving.

R U plumbing the switchover solenoids so you can put the return dino into the veg tank to assist? Also important for shutdown to prevent Palm getting into your startup tank.

My P38 takes about 3 miles to heat for switchover. I have a temperature readout from fuel filter area,

Another idea possibly is to make a remotely adjustable blanking shutter for the main rad, but you'd need a secondary reminder to open it! It's possible that with all the extra cooling from the veg that it may be feasible to partially cover the Rad permanently. I know some will scream about overheating risks, but with enough temp read outs and secondary warning circuit - may be worth considering.

WVO solid palm, I'll be interested to hear how you get on with that. Frybrid do a "heatstick", or are you putting a coolant coil into the tank?

Hi Guys, Everything will be heated especially the veg tank which is what i want to pre warm along with the coolant hence the second battery. I am only putting a 20L tank un the engine bay as I found a larger tank takes ages to heat up. I dont mind getting out every now and then and dumping another few ltrs of solid veg into the second tank. If you keep them in the cabin with you they tend to go slightly runny. Yes I am using pollock valves to switch over and the purge will be on a timer and dump into the aux tank. I got the timer wrong once and flooded the aux tank lol. A simple high level switch and warning light / buzzer sorts it now.
I had thought of a rad cover and may go that way. last time i did it I had and internal temp gauge and an engine bay temp gauge which can be useful.

It works well on solid veg, just be prepared to change filters more often and lets face it Veg is free so changing it every 100 miles is only a couple of pound.

I may and only may go down the route of a plug in heater so i can run on veg from the off in a morning. At night I can use the electricity from work they are Ok with that. Its if I go anywhere else it becomes a bit more of a problem but then hay its only 10 miles and the car is upto full temp. 1/2 gal of derv??

Phew long post. and slightly off topic. sorry all