Lotus Elan

Overheating Battery

PostPost by: matt1954 » Mon Jun 17, 2024 7:50 pm

I’ve just completed the restoration of my Elan Sprint. I installed a new RB340 voltage regulator which is charging the battery but I noticed that the battery gets very hot after a reasonably long run. Any ideas what might be causing this? Could the voltage regulator be putting out too much current? Any tips on how to resolve this.
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PostPost by: nmauduit » Mon Jun 17, 2024 8:00 pm


I would consider that very seriously (an electrical fire is not something you want to experiment on a fiberglass car) to find out how the new regulator actually works I would monitor the charging voltage (which may depend on the battery condition, to be assessed when disconnected), and check if this voltage may be over the maximum tolerated by the battery (overcharging would make it generate heat). The charging voltage would depend on RPM so you may want to test it accordingly and not only at idle.
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PostPost by: Andy8421 » Mon Jun 17, 2024 8:21 pm

The battery shouldn't get hot. It is likely that the RB340 is incorrectly set or is faulty. Ideally, the battery should 'float' at around 13.6V to 14V when fully charged.

Lucas produced some excellent training pamphlets back in the day. This explains how to test and set a RB340 (section 4):

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PostPost by: Lotusian » Tue Jun 18, 2024 6:52 am

My Sprint battery got so hot that the acid overflowed and melted the boot carpet.
Clearly overcharging, so got a new alternator and solved the problem.
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