samjc
|
| posted on 23/2/12 at 01:35 AM |
|
|
battery type ??
Looking at options of a battery for my kit build (pinto engine) whats the smallest Amp hour rating battery i can go for ??
|
|
|
|
|
britishtrident
|
| posted on 23/2/12 at 08:45 AM |
|
|
Depends on:
What you want it for ? Occaisional blast/trackday or more
How big and state of tune of the engine ? --- 2litre requires more cold cranking amps from the battery than a 1600.
If you want dependable cold starting ?
How long you want the battery to last ? --- size, quality and type matter.
how big a priority is weight and space ?
Are you in a situation where you can keep the battery connected to a smart charger on a float charge ?
The performance of a battery is measured by two factors charge capacity in Amp Hours (AH) and cold starting ability measured in Cold Cranking
Amps (CCA)
Every time you do a cold start or let a battery discharge you do some damage to a battery that is not recovered by re-charging.
Tiny batteries will cold start big engines during the summer months but the smaller the battery the more the batteries life is reduced.
Fairly obviously bigger capacity batteries as well as storing more energy also pump out more amps in a cold start situation.
Also the type number or physical size of a battery does not always reflect the AH or CCA rating, it varies a lot between manufacturers. If you
buy a small battery be extra careful to buy good quality top range battery with a respected brand name.
I recently tested a couple of batteries when try out my new voltage drop tester. Using the volts drp tester and my induction ammeter to measure
current a big type 096 high quality (Exide Silver) battery (big tin top or small diesel 74ah 750cca ) produced 11v and 84+amps under load. A
less well known brand type 063 (1.4 litre tintop 44ah 360cca) produced 10v and 68 amps under load. The big battery delivered to the starter
roughly 924 watts compared with 680 watts. I haven't tested a motor cycle battery yet but reading the instruction supplied with
the tester only 9v would be a reasonable expectation.
Personally my choice for 2 litre Pinto wouldn't be smaller than type 063 but you will get away with a smaller battery for summer use but
it has to be given a bit extra care if you expect it to last.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
FuryRebuild
|
| posted on 23/2/12 at 09:21 AM |
|
|
I tend to use the varley red top 25 batteries.
British Trident has certainly highlighted the many necessary things to think about.
My experience is:
They have enough cold cranking amps to turn a high-compression pinto over and at the same time power an MSD ignition system to light it all up. They
can provide cranking current for about 20-30 seconds before they start to slow down and at that point, you definitely stop immediately.
They are pure lead, gel filled, sealed batteries, so you can mount them any old how, and being as compact as they are, I had mine mounted down on the
floor in the engine bay right next to the startermotor. This meant I only needed a 6" cable from battery straight to startermotor to save
precious watts due to wire resistance.
I generally have to replace the battery every two years (which according to Merlin is very good going) and you do need to keep an eye on battery
condition.
When I installed all this, I had the auto electrician also mount me a power plug on
the end of some jump leads and the opposing end straight to the battery, so at the slightest sign of it running out of power, I would connect an
external supply. I had the connector mounted in the wheel-well of my fury so I could get to it without having to open the bonnet.
I also had my car to bogg-brothers every year on the rollers for a check. This meant everything was in a good state of tune, so it would start from
cold (carbs primed) first turn of the crank - no need for choke. In fact, David took one look at the choke installation and took it all off (it was a
neat installation) but said "ay lad, when it's done properly, you don't need all that gubbins) and he was totally right.
You need to give your battery the best chance, so good ignition is important. I can't recommend MSD enough - easy to fit and on something that
runs a lot of advance (38 degrees on my pinto) you need every chance you can get to get it to spark up.
Cheers
Mark
[Edited on 23/2/12 by FuryRebuild]
|
|
|
britishtrident
|
| posted on 23/2/12 at 11:12 AM |
|
|
I did another test this time on my Maplin booster jump start battery pack which has a 14ah cheap as chips Chinese motor cycle battery in it.
It produced 9v under load but at a whacking great 80 amps ---- surprisingly good performance but the amps were dropping off, after a
couple seconds it had dropped to 78 amps, and these cheap Chinese batteries are very variable in quality.
These aren't in any way scientific tests but give a general indication of what to expect.
Generally if a battery produces 9v under load it will start the engine.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
