Use of leisure battery to start if 'engine' battery flat?

[Moyners]

Hello all,

For the second time since I got Vanny in June I have managed to flatten the 'engine' battery and needed a jumpstart.

Would it be feasable to use the leisure battery to get her going if I do it again? Could I just use a pair of leads from one to the other? The reason I feel unsure is that on both occasions of being jumped with leads the other vehicle had to be revving quite hard and don't fully understand the process.

I'd appreciate any advice.

Paul

[ghost123uk]

Would it be feasable to use the leisure battery to get her going if I do it again? Could I just use a pair of leads from one to the other?

If you use a proper leisure battery, designed solely as a leisure battery then it is not a good idea at all. Firstly a "leisure only" battery does not have the output capability of a proper cranking battery. Secondly it is bad to try and pull that many amps from a leisure battery, it warps the lead plates inside.

However, many folks (including me) use a "normal" battery as a leisure, just fit one of those cut outs that prevent it from going too flat (damages normal batteries going flat does)

Also, there are some "duel purpose" batteries but they are not common and are expensive.

The reason I feel unsure is that on both occasions of being jumped with leads the other vehicle had to be revving quite hard and don't fully understand the process.

Although often done it is not good practice to jump start from a vehicle that is running. Reason is the combination of a flat battery and the power required to crank the engine can easily exceed the amp draw that the alternator on the running car can supply. This can overheat / damage the alternator. Sub standard jump leads can cause excessive voltage drop which can seem to be less of an issue if the other engine is running (and by running, producing 14 volts, compensating for the losses in the cable).

Best practice when jump starting is not to ! What I mean is connect up the leads as normal, (ALWAYS check 3 times before connecting the last crok clip up !!!!!!) then start the engine of the car with the good battery. Then leave it alone for at least 15 minutes at a fast tick over (adjust, wedge cable, use a brick, or just sit there with foot on accelerator a bit.) This will put some charge into the flat battery. Then turn off the engine, keep leads attached, try firing it up.

Good quality leads are well worth the extra expense.




Now, the most important bit of your post is why the starter battery goes flat
Do you know why ? (Modern car radio's are often guilty, but can easily be re-wired to the leisure battery).
Let us know...

[KylieKamper87]

I'm not an expert was told never to do it again when I did it at a show as it damages leisure battery.

something to do with charging cycles, would only do it on emergency now

Am sure someone can explain better than me the reasons!

[1664]

As said, it depends on what type of battery you are using as a 'leisure' battery. My leisure battery is exactly the same as my starter battery; so it's a starter battery being used as a leisure battery and can be used to turn my engine over via jump leads without damage (and has done occasionally).

[California Dreamin]

Quote: If you use a proper leisure battery, designed solely as a leisure battery then it is not a good idea at all. Firstly a "leisure only" battery does not have the output capability of a proper cranking battery

Interesting statement....and to be honest, I always believed this to be the case but have a look at the CCA (Cold Cranking Amps) on this typical Leisure battery:
http://www.batteries4leisure.co.uk/batt ... tAodQEMAZA" onclick="window.open(this.href);return false;

750CCA is at least 25% higher than your average CODE 100 starter battery

That general statement of Leisure batteries not having a high enough capacity for starter cranking may have been true in the past but I think battery technology has moved on since then

Martin

[kevtherev]

Absolutely agree with martin 100%
old wives tales are hard to ignore sometimes.

[scottbott]

you have pm

[ghost123uk]

That general statement of Leisure batteries not having a high enough capacity for starter cranking may have been true in the past but I think battery technology has moved on since then

Good input Martin

Looks like I need to "keep up at the back" I do have a Leisure battery (on the "other van") that says it is OK to use as a cranking battery but I was under the impression they were uncommon and quite dear. That link Martin supplies certainly does, as Kev points out, indicate that my knowledge is out of date on this subject It seems our wiki is similarly in need of updating as here it states "So, if you are purchasing a battery and it has a cold cranking rating and the salesman says it is a deep cycle battery, but will also start your engine; then it is in fact a starter battery (end of story)"

You learn summat new everyday

[California Dreamin]

No worries....like I said, I was under that same impression myself until I looked at several current leisure battery spec sheets.
I would just say, look at your leisure battery label and if it does list a CCA (cold cranking amps) figure, then it's good to start an engine...if it doesn't have a CCA shown then err on the side of caution and don't use to start the engine....



Martin

[Moyners]

Thanks for your comments, everyone, I'm getting an education here . . . "cold cranking amps" indeed!

This time I think it was radio or lights - first time was an electric coolbox.

So a few things for me to look into and think about. I do like the idea of switching radio to use the leisure one.

I will certainly be getting my own set of leads and am grateful for the tips on how to jumpstart.

P.

[California Dreamin]

Adding to the correct way to use 'Jump Leads'

The connections made between two batteries using jump leads are rarely good enough to carry the 150 - 200amps needed by the starter motor.
Therefore, the objective is to connect the leads and allow some of the charge from the good battery to 'recharge' the other.
I would advise the leads are connected for at least 5 minute before the first attempt at cranking the 'dead motor'. Enough time for the flat battery to regain a minimal charge so that when cranking, not ALL of the supplying power is trying to come down the jump leads.

Martin

[kevtherev]

Yes, you can't jump a dead 'un.

[ghost123uk]

Yes, you can't jump a dead 'un.

Off now to the "out of context" thread