Modifying the battery box. Nov / Dec 2014
The truck still had the same battery from when I purchased the truck back in 2007 and the battery was not even new then. That
made it at least 7 years old but more likely 10+ years old. Considering it was still working reasonably well this is a good life span
for a battery. If the truck was in regular use it was fine but if the truck had been standing for a few weeks it probably would not
start unless I charged the battery first. The number of times the engine would need to turn over to pull the fuel through after
standing a few weeks just exceeded its capability The original battery is an American battery and I have not thrown it away.
I hope to use it in my caravan this summer. I have been regularly charging it every week or so to keep it on good condition. This
American battery exactly fitted the original battery box but I did not want to order another battery the same for several reasons.
1. American batteries are expensive and difficult to find in the UK. In the past I have used Rodley Motors but they don't seem
to stock them any more without it being a special order.
2. The physical size of a new American battery seems to vary even with the same model number (after checking specifications
online) and so the battery box may still have needed modification.
3. The Bosch S5 battery is a fantastic hi spec battery and comes with a 5 year warranty. In addition, if you buy the battery from
Costco (assuming you have a Costco card) it is much cheaper than buying from online retailers. A member of staff at Costco also
said even if you buy an S4 battery the Costco battery has a lifetime guarantee! Then he said "within reason". Interesting comment.
See the old battery and battery box before modifications below.
The problem is the that the S5 is 2 or 3 mm longer than the original U.S. battery (which was a fairly snug fit) and that means the
battery box needed modifying. The battery box hold down frame will not fit an S5 battery either and so it also needs to be modified
or re-made. I did not want to alter the original frame so a new one was manufactured. See the new hold down frame below.
The method to modify the battery box easily did not involve altering the hole centres for the bolts going through the chassis
rails (frame rails). The battery box consists of two end pieces and a base. These three components are riveted together. To
avoid drilling the chassis rails, the rivets were drilled out in the left hand end and the two holes in the left hand end of the
battery box were horizontally slotted by an addition 5mm so that the new bolts could still use the original holes through the
chassis but the left hand end could be moved left by a few millimetres within the new slots. Since the bottom of the ends
also wrap round the base (overlapping joint) and again are fixed here with two more rivets, these rivets were also drilled out.
These holes were slotted and again new stainless steel bolts, nuts and washers replaced the rivets. This enabled the two ends
to be 5mm further apart. (Without this mod the S5 battery would have dropped in but was very tight which made insertion
and removal difficult). A thick rubber insert (mat) was put into the bottom of the battery box for the battery to sit on.
The original hold down frame was put into storage. The truck now starts no matter how long it stands though the winter when it
is used less frequently. A final note about Costco. They told me it does not matter whether you buy an S4 battery from them or an
S5 battery from them, as if you buy a battery from Costco it had a lifetime warranty. Clearly this would need confirming but that
is what the sales staff said. It is, however, better to buy the S5 battery as it is a better higher spec. battery than an S4 anyway.
The S5 battery from Costco was only £43 + VAT = £51.60
Why is the position of the battery box a great idea?
1. It is where GM decided to put it so why not keep it here?
2. The last thing you want is an unsightly battery under the hood. The engine bay looks much better without a battery.
3. lifting the carpet provides easy access.
4. If storing the vehicle in a garage over the worst of the winter or for long periods, it is easy to unhook the
positive lead for safety.
5. Unhooking the positive cable while parked somewhere, the common thief is unlikely to have a tow truck and is
even more unlikely to know where the battery is or be able to start the truck.
6. We like our classic cars and trucks because they are different and our trucks are even more unusual
with the hidden battery.
7. Conclusion - GM made the correct decision to put the battery under the floor.
Update Dec. 2019. Battery rotary switch.
In 2019 a rotating knob / switch was fitted onto the negative battery cable where it pushes onto the battery terminal.
That makes it easy to disconnect the battery without having to remove the cable from the battery terminal.
About £4.00 ($5.00) from Amazon and many other places.
Ideal for disconnecting the battery while the truck is in the garage or as a security feature.
The picture above was taken after the Dec. 21 battery box and battery upgrade below but it shows the rotary switch.
Important Update Dec. 2021. Bigger battery and bigger battery box.
Check the notes above from 2014 about how the original battery box was modified.
Whilst the battery has been OK over the years, it has never been as good as it should be. The Bosch S5 size - 005
battery was changed under warranty in 2019 for a Bosch S4 005 battery. The S5 was failing. The new battery
was a bit better but in Nov. 2021 this was also returned under warranty. I was never really happy that the engine
was being turned over vigorously enough. Yes maybe the first attempt was OK but after that it sounded like the
battery was struggling. An Antel BM300 battery monitor was purchased. This is an excellent device and it connects
to your smart phone via Bluetooth. Below you can see the results of the new brand Nov. 21, s4 005 battery failing
the "Cold Cranking Test". Here the battery should not fall below about 9.5V while cranking.
After a bit of careful thought I came to the conclusion that maybe the battery was not "big enough" for a
350ci Chevy small block V8 engine. The s4 005 battery specification was 540 cranking amps and 60ah.
Would it be possible, with modifications, to fit a larger battery?
This would mean modifying the battery box again. Not a problem, the hard work of drilling out the Chevy rivits
had been done. They were replaced with bolts in 2014. It just meant I needed to build a new battery box left side
and space it to the left by about 50mm (2"). I had identified a possible replacement as a Bosch S4 007 battery.
Most importantly this new battery had 680 "Cold Cranking Amps" and was 72Ah. About £85 ($100). This battery was
the same height (175mm), the same width (175mm) but was longer. The length increased from 230mm to 278mm
(new length about 11"). This was an increase of 48mm (about 2"). The hole in the floor was "just" large enough
to lower this battery through, however, the box below was offset from the hole and so the battery would need
to be tilted and then straightened up once partly through the hole. This also meant that due to the insertion tilt,
if the left hand / top edge of the battery was not going to be blocked by the new left hand side of the battery
box, this new left hand side needed to be low to allow clearance. By making the new side only using
3mm x 50mm x 50mm steel angle, this was achieved. First it was important to test the theory and this was done
by making a cardboard mock up of the new battery (before buying it) then removing the left hand side of the
battery box, inserting the battery and checking clearances. It all looked good and so work commenced.
I purchased a 1m length of 3mm x 50mm x 50mm steel angle locally for about £10 from the "Metal Supermarket" ($14.00)
I also purchased a piece of 9mm ply wood (500mm x 500mm) from a local DIY store. I already had bolts, washer and
nuts in the garage. The wood was very important as it was used to measure and assemble the new box. In particular,
by removing the old box, offering it up to the ply wood, and drilling through the 4 mounting holes it meant I
had transferred the chassis rail (frame) mounting hole spacing to the ply wood. This made life a lot easier.
The angle was cut, shaped and bolted together mostly with 8mm bolts. 3mm x 50 x 50mm steel was strong
enough not to need any additional triangulated webbing support in the side which would foul the
tilted battery insertion. The pictures below show the process of making the new side.
The parts were then cleaned up and painted.
The new box was assembled, fitted to the chassis and the battery inserted.
Finally the battery was held in place using two Velcro straps. In this location the battery is not going to
go anywhere - left, right, forwards or backwards, but the straps were there to stop any bouncing.
The new battery was tested again using the Ancel BM300 battery monitor. Immediately you could hear
it was turning over the engine effortlessly. The tests were passed. See below.
The Ancel BM300 battery monitor is widely available but I found the cheapest source was from the
Ancel shop on "Aliexpress". It was about £22.00 ($28.00) including delivery.
It takes about 10 days to come but at that price, worth the wait.