Building a Battery Box

[Stemar]

To increase the domestic battery capacity for Jazzcat, I need to build a new box, to take two105AH batteries with a total weight of about 50kg The existing one is bolted to the bulkhead at the forward end of the engine compartment in the port hull, and I'm planning to make a similar one for the Starboard bulkhead. I'm going to use 200gsm glass cloth (it's what I've got), with some foam strips to stiffen the bottom and sides and timber reinforcing along the back, where the mounting bolts will go (6, 8mm bolts)

I've made a female mould, covered in parcel tape and cling film, and I'm thinking that 8 layers should be adequate - two inside, then the reinforcing, and a layer to fix it in place. I'll let that go off and remove the mould while it's till fairly flexible, then 5 more to finish. Does that sound about right, or am I being too optimistic?

Thanks in advance

 

[VicS]

To increase the domestic battery capacity for Jazzcat, I need to build a new box, to take two105AH batteries with a total weight of about 50kg The existing one is bolted to the bulkhead at the forward end of the engine compartment in the port hull, and I'm planning to make a similar one for the Starboard bulkhead. I'm going to use 200gsm glass cloth (it's what I've got), with some foam strips to stiffen the bottom and sides and timber reinforcing along the back, where the mounting bolts will go (6, 8mm bolts)

I've made a female mould, covered in parcel tape and cling film, and I'm thinking that 8 layers should be adequate - two inside, then the reinforcing, and a layer to fix it in place. I'll let that go off and remove the mould while it's till fairly flexible, then 5 more to finish. Does that sound about right, or am I being too optimistic?

Thanks in advance

I'd have made a stout plywood box and lined it with fibreglass,, and covered with fibreglass too perhaps

 

[PCUK]

I'd have made a stout plywood box and lined it with fibreglass,, and covered with fibreglass too perhaps

Me too! String and simple!

 

[rogerthebodger]

Why do you need a box to contain a battery you just need to strap/bolt it down to prevent movement and to allow ventilation to allow H2 to escape

 

[Stemar]

Why do you need a box to contain a battery you just need to strap/bolt it down to prevent movement and to allow ventilation to allow H2 to escape

The only sensible place is in the engine compartment, above the engine, which is where the existing one is in the port hull. The starboard hull needs a box to hold the additional batteries. There's no other spare flat space in a locker, plus it balances the weight.

 

[Refueler]

I'd have made a stout plywood box and lined it with fibreglass,, and covered with fibreglass too perhaps

Exactly as mine on the 25. But without external GRP.

Simple .... sealed by the GRP... I know it worked well as one winter - one battery case cracked and it emptied into the box .... Devils job lifting batterys out and not dripping onto anything - then emptying the box ... smell lingered for days !!

 

[Tranona]

Not sure it is necessary to make it out of GRP or cover ply with GRP. It just needs to be strong enough to hold the battery in place. Both my battery boxes are just ply painted with Danboline. The main one was originally a GRP trough but I needed to use all the space between the bearers so built a new one out of 9mm ply with stiffening battens. Old arrangement on the left, new on the right before wiring complete.

 

[Refueler]

I consider sealing the ply as important as the strength ... battery acid is not a fluid I want seeping out of the box....

 

[Tranona]

I consider sealing the ply as important as the strength ... battery acid is not a fluid I want seeping out of the box....

The batteries are AGMs and I have never had any leakage from that type in the 30 odd years I have used them. In the Bavarias they just sat on pads on the hull inside the under berth lockers clamped down. Danger from leaking battery acid is vastly overrated.

 

[Neeves]

I'm with Roger, why a box. The battery itself is a robust box. Why not a robust shelf, bit of hardwood, varnished, with retainers to secure the batteries to the shelf (and to the bulkhead).

The batteries you are considering are not light and if you make the box neatly you will have a devil of a job dropping the second battery into the box and even more difficulty taking the batteries out.

All you need is a simple robust shelf and clamps.

Jonathan

 

[Tranona]

That is quite possible, but the OP is mounting 50kgs of 2*105Ah AGMs and it is much easier to build a box strong enough to take that weight than a plain shelf.

 

[Neeves]

That is quite possible, but the OP is mounting 50kgs of 2*105Ah AGMs and it is much easier to build a box strong enough to take that weight than a plain shelf.

You are quite correct but there is no suggestion of a simple shelf.

I was persuaded to suggest the shelf as the OP says his exisiting battery(s) are bolted to a bulkhead, suggesting that the existing arrangement is supported (bit like a shelf but a box) and making a shelf with a couple of beefy brackets seemed in line with what had been done previously and is simpler than a box, 2 decent brackets and a couple of M12 bolts for each bracket

Having said that I note the OP has already invested time in making a mould and may be wedded to his course of action (though he will still need to bolt his bow to a bulkhead) 6x8mm bolts suggests a robust box and a. robust bulkhead.

One likes to offer options.

Jonathan

 

[rogerthebodger]

Ok I am an iron fighter so my og to material is steel

My engine start battery is made of a angle iron shelf the battery is located in with 2 side supports to tale the weight of the battery.

The battery is held in place in the same way as a car battery with hook bolts

Below is one section of my domestic batteries which sit in an angle frame and a top clamp held down with screw clamps

https://flic.kr/p/WYQ3F2

 

[Refueler]

Pal of mine blew his wedding ring asunder and left his fingers with burns after his spanner when tightening cable clamp on a car battery ... the spanner touched the metal holding frame ... ZAPPPPP !!

OK - I accept that a car is different to a boat as the car itself becomes the negative ... but still I am not so keen on metal boxes for batterys ...

My ex Soviet motor boat has a common plastic tool box - slots for cables made so that lid closes ..... holds a 70 A/hr standard car battery.

 

[VicS]

Pal of mine blew his wedding ring asunder and left his fingers with burns after his spanner when tightening cable clamp on a car battery ... the spanner touched the metal holding frame ... ZAPPPPP !!

OK - I accept that a car is different to a boat as the car itself becomes the negative ... but still I am not so keen on metal boxes for batterys ...

My ex Soviet motor boat has a common plastic tool box - slots for cables made so that lid closes ..... holds a 70 A/hr standard car battery.

That is why when disconnecting or reconnecting a car battery ( or Roger's boat batteries ) you should disconnect the negative first and reconnect it last.

.

 

[Refueler]

That is why when disconnecting or reconnecting a car battery ( or Roger's boat batteries ) you should disconnect the negative first and reconnect it last.

.

I agree ... but it illustrates the possibility of mishap .. one moment of lapsed thinking and ZAP.

I hate to admit it - but having had a moments not thinking - the shock was something else > >

I regularly solder plugs onto LiPo batterys - they may be small compared to a car battery etc. - but believe me - they pack one hell of a punch.

I had clamped the Deans plug in the small vice .... soldered one lead .... then went to solder the other lead to plug .. as soon as lead touched the plug pin - the 4th of July welding spark was WOW !!
I had not noticed that the vice was clamping the plug pins - not the insulated body ! As soon as second wire touched - it was a dead short of a 5000 m/Ahr 100C 3S LiPo ....

I was lucky that lead did not weld itself - but they showed signs of the heat generated along them.

 

[rogerthebodger]

That is why when disconnecting or reconnecting a car battery ( or Roger's boat batteries ) you should disconnect the negative first and reconnect it last.

.

Also unlike a car where he negatives is connected to the car body and my boat there should NOT be a negative connection to the hull With a GRP boat any battery metal support frame would be insulated electrically from the boat hull so where is the issue as its so unlikely in the real world to have a short.

Using a spanner that touches both positive and negative shous lack of care or worse

 

[Refueler]

Also unlike a car where he negatives is connected to the car body and my boat there should NOT be a negative connection to the hull With a GRP boat any battery metal support frame would be insulated electrically from the boat hull so where is the issue as its so unlikely in the real world to have a short.

Using a spanner that touches both positive and negative shous lack of care or worse

As they say - Sh** happens.

 

[rogerthebodger]

As they say - Sh** happens.

Not if the designer tales a proper risk assessment to prevent SH** happening

note the direction the clamp bolt is positioned so the swing of a spammer will not come into contact with the opersit terminal thus connt cause a short

 

[Refueler]

Not if the designer tales a proper risk assessment to prevent SH** happening

note the direction the clamp bolt is positioned so the swing of a spammer will not come into contact with the opersit terminal thus connt cause a short

Not everyone is 'perfect' .....