2 Batteries

[ed209]

Hi

Running 2 batteries parallel, Good or bad?

Regards

[Bob Ajob]

IIRC Good if they are the same condition, same type, have got the same charge.
Bad if not.
You wouldn't want to do them in series, or this would be 24v...

Not quite sure how you wire them up though, not done that mod. Also not sure on how big an alternator you need to fill them both up at the same time.

[wheeler]

ide like to put a second battery on as well how to

[ed209]

Hi

What i have learned is that the standard alternator wouldn't handle the 2 batteries, True?
To keep it 12v the earth from one has to go to the earth from the other and the same with the live?

Regards

[Bob Ajob]

Hi,

Not sure on alternator and amps etc, what size alternator do you run currently? The standard is different depending upon the vehicle. It may be that you just need a larger one as the charge will only be half to each battery, though your current alternator is probably more than you need for one battery. It all depends on what your battery powers - starting, lights (sealed beam or halogen - what wattage?), additional spot lights, radio, cb, etc etc.

Earth to earth, live to live makes it parallel and hence remaining 12v.

I can't recommend how to add a second battery, as I never have done so, sounds good in theory, practice may be different. Connecting them should be simple, it's split charging and having separate batteries for starting and aux which gets complicated. I would recommend searching through the "modified" section on this forum for split charging to get additional info, it all depends upon your needs.

Regards,
Rob

[Rich_P]

IIRC Good if they are the same condition, same type, have got the same charge.
Bad if not.
You wouldn't want to do them in series, or this would be 24v...

Not quite sure how you wire them up though, not done that mod. Also not sure on how big an alternator you need to fill them both up at the same time.

Series diesels, or at least the earlier Series 2/2A genuine diesels had two batteries and were 12v...

[woody]

IIRC Good if they are the same condition, same type, have got the same charge.
Bad if not.
You wouldn't want to do them in series, or this would be 24v...

Not quite sure how you wire them up though, not done that mod. Also not sure on how big an alternator you need to fill them both up at the same time.

Series diesels, or at least the earlier Series 2/2A genuine diesels had two batteries and were 12v...

could this be 2 6volt batteries, asi remeber when i started in the garage some commercial vehicals had 2 6volts in series to make a very heavy duty 12volt

[Rich_P]

I don't think they were 6v, as some people still use them with a pair of batteries.

[woody]

I don't think they were 6v, as some people still use them with a pair of batteries.

when i started there were 6volt batteries in bedfords and stuff
still got a 2volt tester as you could test each of the three cells
now using the tester on 48 volt fork lift trucks each battery is 2 volt
need someone old and technicaly minded to confirm this (btm  :lol: )

[ross501]

if you connect them in series you get 24v if you have them in parrell they will stay at 12 v like when you use jump leads you only get 12 v

[ed209]

To Answer bobajobs question
Halogens 55/60w
1 pair of spots 55w (100w bulbs to fit them though)
CB to fit
4 spots for roof (will be 70/100w each)
Rear work lights 55w
the heater
int light
4 x 12v for tom tom etc

Regards

[mark.yellow.series.3]

stick two batteries on it, it will be fine.
i have two big batteries on mine with a RRC alternator on, and it works a treat.
only thing is, if your alternator isnt big enugh it will take a long time to charge the batteries up, and at this time the alternator will be its maximum output for longer then it normally would, and this could shorten the life of the alternator.

[S188]

From what I've herd you have to be slightly carefull of running batterys in parallel.  If one gets alot more discharged than the other they can try and charge eachother.

The way many splitcharges work is to disconect the 2 batterys when they are not being charged.  This is good as you can then flatten an acessory batt adn leave your starter batt in good condition.  Run the earth conections together with earth straps.  For the +ve conection you can build a simple system out of 30amp wire and a relay running off the charge light.  It won't chagre the battery really quickly though.  Bigger relays that handle more amps cost alot more money.

Another issue which more expencive systems get round is strain on the altinator.  If you start the engine with the main battery slightly depleted it'll load the altinator for a few minutes to recharge it.  If at the same time you add a second flat battery your altinator will be working very hard for a while, it might not like it!  Expencive splitcharge systems only conect the second battery after the first one has recovered to reduse the load on the altinator.

Regardless of what batterys you have you will need an altinator big enough to surply all the equipent your going to run.  It efectively runns off the altinator, the battery only cushons the system.  short term drains like starting or winching is fine but if you drive around with the heater and extra lights the altinator needs to be beefed up.  An extra battery will just make it go flat slower.

As for the early twin battery series diesels they all DEFINATELY used 2x6v batterys wired in series.  I think it was the only way they could get enough amps out of batterys of that era.  In the end they got a 12v truck battery instead which has now been fitted retrofitted in place of many of the twin 6's.

Your 2 spots and headlights plus the rest of your electrics will be right on the limit for a standard altinator, it wont charge very fast.  for the 4 roof lamps you'll need a bigger altinator or you'll findout the standard setup was brighter after they have all been running for a few minutes!

[ed209]

Hi S188

That has made it a little easier for me to decide I have just aquired a 65amp altenator from a 110 will this be enough?

Regards and thanks for taking the time.

[Lee_D]

Yes fine.

Split charge is a different bag of spanners.

Just wire + to +

- to - sorted.

1990 RRC TD is wired thus... not a split charge in sight.

[James.Harwood]

Just get 1 good battery (Optima) and a big alternator.

The only time to bother with 2 batteries is if you have an electric winch, then you need 2 (on a split charge system).