Conundrum

[lotusles]

Hi All
I have a 1956 Ford Special that was my first car in 1970 that i still own. For any enthusiasts it is a woven mat fiberglass 2 seater prototype made by Bonglass, that later became the Rochdale ST
It was originally 6v and the battery was circa 140A. I converted it to 12v about 20 years ago keeping the same starter motor and gauges as they are bullet proof. The current battery id mini type at about 40a, but since refitting the Aquaplane head it struggles to turn over.
In the modern world i can get a mini size battery that has 100a, if i fit this will it cause me any issues?

Thanks
Les

[Simon_P]

It sounds like you are quoting Ah which is capacity and CCA which is output. Theoretically Ah won't make any difference - you'll get more cranking before it is flat. It is the CCA that is of interest as this is how many amps it can put out. However, you haven't been able to buy a decent mini battery for years and they don't last long in an infrequently used classic.

How was it converted from 6v to 12v? If you just put in a 12v battery in place of the 6v battery I would be extremely cautious. A modern technology battery as well as having greater storage capacity is likely to have a much higher discharge rate. Having doubled the voltage you double the amps for a given resistance, but power is amps squared x resistance, and power =heat. If you remove the limitations of the battery you might cook the starter.

[Saltire]

Les, it’s unlikely to be of use immediately, but Yuasa UK are just down the road from you in Swindon and run (or at least used to) a good tech. support department. If it were me, I think I’d be speaking to them when all this is over and seeing what they suggest. It may be that a battery for a slightly different application would fit.

On another tack, I seem to recall reading about someone who’d adapted one of the capacitor-based jump-start boxes (in conjunction with a small battery) to provide extra ooomph for starting a special. I’ll send it over if I can find it.

The Rochdale brings back memories. As I remember, they only produced about 90 or 100 STs, so even more exclusive than our Elans. Is yours Ford 10 based?

[lotusles]

Les, it’s unlikely to be of use immediately, but Yuasa UK are just down the road from you in Swindon and run (or at least used to) a good tech. support department. If it were me, I think I’d be speaking to them when all this is over and seeing what they suggest. It may be that a battery for a slightly different application would fit.

On another tack, I seem to recall reading about someone who’d adapted one of the capacitor-based jump-start boxes (in conjunction with a small battery) to provide extra ooomph for starting a special. I’ll send it over if I can find it.

The Rochdale brings back memories. As I remember, they only produced about 90 or 100 STs, so even more exclusive than our Elans. Is yours Ford 10 based?

Yes 10hp, 1172 cc. It has a Buckler Diff and 16" wheels. Ill upload some piccies when I work out how....

[lotusles]

It sounds like you are quoting Ah which is capacity and CCA which is output. Theoretically Ah won't make any difference - you'll get more cranking before it is flat. It is the CCA that is of interest as this is how many amps it can put out. However, you haven't been able to buy a decent mini battery for years and they don't last long in an infrequently used classic.

How was it converted from 6v to 12v? If you just put in a 12v battery in place of the 6v battery I would be extremely cautious. A modern technology battery as well as having greater storage capacity is likely to have a much higher discharge rate. Having doubled the voltage you double the amps for a given resistance, but power is amps squared x resistance, and power =heat. If you remove the limitations of the battery you might cook the starter.

Ah, now that makes sense. I have found a mini type battery with 45AH and https://www.ebay.co.uk/itm/VAUXHALL-COR ... 2749.l2649.
Which fits the limited space under the bonnet, but it might prove prudent to get a bigger battery and fit it in the boot.
With regards 12v, its a recognised update from the FSOC and it seems to work, its the higher compression and probably the fact my current battery is about 10 years old and been on constant trickle thats the problem.

Les

[Saltire]

Les, it’s unlikely to be of use immediately, but Yuasa UK are just down the road from you in Swindon and run (or at least used to) a good tech. support department. If it were me, I think I’d be speaking to them when all this is over and seeing what they suggest. It may be that a battery for a slightly different application would fit.

On another tack, I seem to recall reading about someone who’d adapted one of the capacitor-based jump-start boxes (in conjunction with a small battery) to provide extra ooomph for starting a special. I’ll send it over if I can find it.

The Rochdale brings back memories. As I remember, they only produced about 90 or 100 STs, so even more exclusive than our Elans. Is yours Ford 10 based?

Yes 10hp, 1172 cc. It has a Buckler Diff and 16" wheels. Ill upload some piccies when I work out how....

Sounds delightful

Back to the batteries: if it’s 10 years old, that may well be the issue. When I bought my Porsche RS60, the mileage was low but the battery had been in since new (I bought at 6 years old). It soon became apparent that the battery was struggling to turn over a cold engine, even when freshly charged. I replaced it with a new - same spec - Bosch, and starting became a breeze - without changing anything else.