Following on from discussions that were happening in January, I thought that I should post some pictures of my new battery installation.
For comparisson the following shows the old 4off 721 battery installation. It was reading 24v across the batteries just prior to removal, but there wasn't sufficient charge in to get any form of movement out of the starter motor, in fact trying to start resulted in a relay within the cab starter panel clicking away. I'm not sure of the precise reason for the clicks, probably trying to engage something, but then the starter attempts to take all of the current which causes the relay to drop out, which now has enough charge to energise and connect again, but then the starter takes all of the current, relay drops out...
An empty battery crate. Except for the mounting points at the front where the cover clips on, the framework is structurally sound and the plastic coating looks good.
The clamps that hold the batteries down are suffering a bit from corrosion. I don't think the choice of steel for the threaded hook and copper (or a high copper alloy) for the bracket is a particularly good idea, the two are bound to react badly to each other. Once removed to the bench vice and with the application of leverage and penetrating oil, both clamps were moving freely.
After much research I opted for 2off 656 batteries. They have similar dimensions to the old 721's and they can provide easily provide enough current to turn a 3kW starter motor. The leads from the old 721 installation were reused, terminal clamps were purchased from a local motor factors since the 656's have post type terminals rather than both through terminals. Two off the old 721's are used, disconnected, as packing.
Engine started after about 10 seconds of cranking, which was to be expected after 3 months standing. The most important part is how the batteries hold their charge between periods of activity. I'll post again when I go back to the bus in a months time.
On-going work still to be done is to clean the isolator switch beneath the stairs and to grease the battery terminals with Vaseline.
