Battery Brain

[julian64]

crypto said:

julian64 said:

But you are making future problems for yourself. The battery in the NVRAM isn't working while the main car battery is connected and neither is the ni cad battery in the alarm.

The Meta alarm is too old to be lithium, and nicads don't do any length of time flat very well.

If you are going to connect a small battery for the alarm and the ECU you might as well connect the main one with a battery conditioner attached, as apart from the alarm and the ECU I don't think there should be any other drain.

I'm surprised there is a NVRAM in the ECU, because this sounds like a ticking time bomb. After 10 years these batteries are usually dead, so are the nicads in the alarm. Whenever the main car battery is changed or disconnected one would have this problem ? How long does it take to calculate those values once the engine is started ? I guess a default data-set is loaded whenever a power-loss was detected ?

Yep, The NVRAM sits alongsie an eprom in a removable bucket, so easily replaced. It the fully working MBE it stores the maps for fueling etc. In the TVR MBE the software was changed a small amount to store a permanent set of maps in the eprom so no longer alterable. The adaptives though are stored in the NVRAM.

Adaptives would be lost if the NVRAM battery failed. But the software would reconstitute these after about half an hour of driving. The adaptives are a moving average so take a little time to settle.

I honestly don't know whether the NVRAM suffers from being disconnected, but because the chips have been superceded and are hard to get now I'm not sure I would take the chance. You could change them to flash, but the pinouts are different

[crypto]

julian64 said:

Yep, The NVRAM sits alongsie an eprom in a removable bucket, so easily replaced. It the fully working MBE it stores the maps for fueling etc. In the TVR MBE the software was changed a small amount to store a permanent set of maps in the eprom so no longer alterable. The adaptives though are stored in the NVRAM.

Adaptives would be lost if the NVRAM battery failed. But the software would reconstitute these after about half an hour of driving. The adaptives are a moving average so take a little time to settle.

I honestly don't know whether the NVRAM suffers from being disconnected, but because the chips have been superceded and are hard to get now I'm not sure I would take the chance. You could change them to flash, but the pinouts are different

I'm pretty sure the logic in the MBE is done in a way that the NVRAM would not suffer when main voltage is disconnected (this is actually done inside the NVRAM). The battery inside the NVRAM would then last maybe only 6 years (instead of perhaps 10 years).

Regarding the availability of the chips, there are types where the battery could be replaced separately, but usually these come in one part, like this one :
http://www.ebay.com/itm/Maxim-NVRAM-256k-Nonvolati...

Maybe somebody knows the chip type, or has got an inside picture of an MBE ?

What you definitely not can do is replacing it with a flash type (even if the pinout and supply voltage is the same). Flash technology uses a completely different method to store data. This would require modifications in the MBE software (apart from that I doubt that flash would be quick enough).

[aide]

maxim-ic make them and it looks like the DS1230AB-200IND+ is a replacement. There looks to be similar options, that have a faster response time, that would suit as well for around $13.

Edited by aide on Saturday 18th February 16:25

[mickk]

Slightly off topic but can you post the serial number of your battery you've just purchased, mine needs replacing and i can see you have a 072.

Is that all i need to ask for?

Thanks.

[aide]

mickk said:

Slightly off topic but can you post the serial number of your battery you've just purchased, mine needs replacing and i can see you have a 072.

Is that all i need to ask for?

Thanks.

It fits ok, but there is no lip on the side near the bottom to bolt it down properly.

www.thebatteryshop.co.uk
Product Code: Y072YP
Description: Yuasa Professional 072 Car Battery
Item Price: £ 81.99
Qty: 1
Total: £ 81.99

Sub Total: £ 68.33
Tax @ 20%: £ 16.66
Delivery: £ 17.97
Total: £ 99.96

HTH

[mickk]

Thanks very much although i've just realised i had left my interior lights on for 3 weeks so that maybe the problem.

What a cock!