Battery Relocation

TVR Battery relocation is always a fiercely debated subject. The standard location is in the passenger footwell along with the ECU and fusebox. Although some will argue that this is the best place, in the Griffith passenger leg room can be described as woeful at best. My second motivation for looking into relocation is to tidy up the mess in the footwell and to allow easier access to the fusebox and ECU.

Existing battery location
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The OEM battery is a standard lead acid type 072.

072 Battery Specifications
AH Value 70
CCA 570
Reserve Capacity 125
Length 261mm
Depth 175mm
Height 220mm
Weight 18.4 KG

A popular battery relocation option and one that a number of TVR owners have opted for over the years is to fit a single Odyssey PC925 battery in the boot of the car. Speaking to owners who have fitted this battery, all have been very pleased with the result long term and have not had any notable issues.

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Odyssey PC925 Specifications
AH Value 28
CCA 330
Reserve Cap 27
Length 168mm
Depth 179mm
Height 148mm
Weight 11.8 KG

Odyssey batteries are widely regarded as one of the best batteries available and have various advantages over traditional types of battery:

Cranking power – capable of providing engine cranking pulses in excess of 2250 amps for 5 seconds, double to triple that of equally sized conventional batteries
Longer service life – up to 10 years of service life
Longer cycle life – 70% longer cycle life than conventional deep cycle batteries
Faster recharge – The highest recharge efficiency of any sealed lead battery on the market, capable of 100% recharge in 4-6 hours.
Mounting flexibility – Non-spillable design, can be mounted on any side in any position except inverted.
Vibration resistance – Design protects against high impact shock and mechanical vibration, a common cause of premature battery failure.
Extreme temperature tolerant – Operating temperatures from -40°C to 45°C
Small footprint – flat plates made of 99.99% pure lead, not lead alloy. Pure lead plates can be made thinner.
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Relocating the battery in the boot is great from an accessibility point of view but the issue for me is the fact the battery is located next to the fuel tank. While I accept that you do not buy a TVR for its safety credentials, personally I am not entirely comfortable with potentially introducing additional risk if it can be otherwise avioded. The chassis of the Griffith does not extend much past the rear wheels which leaves the boot area of the car protected only by fibreglass in the event of a rear end shunt as can be seen in the picture below:

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In search of other solutions I turned the PistonHeads TVR community to see what other owners had done with theirs. As always lots of assistance and ideas came flooding in. I did see a number of Chimaera owners who had created a custom compartment behind one of the seats out of fibreglass which looks like a great solution. Unfortunately in the Griff I needed to retain access under the whale tail to access the bolts which secures it in place.

There was one suggestion from fellow Griff owner Frank (eff eff) who had done something I had not seen before. Frank had two smaller Odyssey batteries wired in parallel, one fitted behind each seat. What a liked about the design was not only were the batteries safely stored within the passenger compartment, away from the fuel tank, but the weight was evenly distributed.  I decided this was the solution for me so I contacted Frank who very kindly shared the specification of his install with me so I could replicate this in my car.

My solution, heavily based on Frank’s design is as follows:

2 x Odyssey PC680 wired in parallel (same voltage but double the AH value). This results slightly higher AH and CCA values and almost double the reserve capacity figure of the tried and tested single PC925 solution.

screen-shot-2017-03-02-at-23-27-48
Odyssey PC680 – Single
AH Value 16Ah
CCA 17
Reserve Cap 24mins
Length 184mm
Depth 79mm
Height 191mm
Weight 7KG

Odyssey PC680 – Double
AH Value 32Ah
CCA 340
Reserve Cap 48mins
Weight 14KG

Regarding the hold down kit, the official kit from Odyssey would not fit in the area behind the seats so I needed to source an alternative with a smaller foot print.

Odyssey Hold Down 2.jpg

After some searching on the internet I found a lightweight billet hold down kit from an American company called JPUSA. The hold down kit had a footprint only slightly larger that the PC680 battery itself.

Billet Hold Down 1.jpgbillet-hold-down-2
https://www.jhpusa.com/store/pc/viewPrd.asp?idproduct=6661&idcategory=128

I understand from owners of TVRs equipped with the PC925 battery that the battery must not be allowed to run flat (under 10.5v) as the battery cannot be revived. Running the battery flat is not normally an issue for me as generally the car is attached to a trickle charger when not in use. I have run my existing battery flat a couple of times down to my own stupidity (leaving lights on etc). Due to the reduced reserve capacity of the Odyssey batteries vs the OE 072 battery I decided it would be a good idea to fit a battery monitor in the form of Battery Brain. A Battery Brain is a compact battery monitoring device that continually monitors the battery charge. If the charge to drops below the minimum required level (11.8v) to start the vehicle, it disconnects the battery. Not only does this stop you getting stranded it also protects the battery from becoming fully discharged. I decided to purchase the battery brain with the IR remote disconnect fob just in case I need to leave the car for a long period of time I can remotely disconnect the battery after I have locked the car.

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http://www.batterybrain.co.uk

I asked Jody at Python Racing to complete the conversion while the car was in having its annual MOT completed. As per usual Jody did an excellent job and I am very pleased with the end result. I will arrange for the trimmer to fit an extended piece of carpet in the passenger footwell and possibly carpet over the batteries in the near future.

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I also purchased a new trickle charger for the car as part of this upgrade. I was unsure as to whether my Accumate trickle charger was compatible with AGM Gell batteries. To be on the safe side I purchased a new CTEK charger with an AGM battery mode.

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