Swapping my leisure battery to LiFePO4

[wallport]

Thanks all. Decided to kick this off before the new battery arrives and have bought a couple of 2 way jointing boxes similar but slightly smaller than the one suggested and 2 pre made leads. I intend to mount the boxes close to the holes but outside the profile of the new battery and migrate the wiring over and connect with the new wires to the existing battery.

When the new battery arrives it will then be simpler to plug it in. I do intend to add a fuse and am still looking at the possibility of an isolation switch. I don't suppose anyone sells a combined switch and fuse in the same unit?

Boxing - well I'm still thinking, perhaps overthinking, on the options but I do appreciate all of the suggestions.

 

[TallPaul_S]

What are the 2 way boxes you've gone for?

Just be aware some look like 2 way bus bars, but are in fact just 2 bolts in a plastic housing - ie the 2 studs aren't connected so you can't use it like a busbar.

For example:

https://amzn.eu/d/0zKFhop

I speak from experience.

 

[wallport]

It was this:

2 Way M8 8mm Battery Cable Power Distribution / Connector Jointing Box 120 AMP | eBay

Power jointing boxes suitable for joining together several cables. M8 Bolts (13mm Locking Nuts included). Sturdy PVC box with clip off lid.

www.ebay.co.uk

I realise I could have trouble due to the number of cables splayed on top of each other but gotta try it and see or spend forever wondering and never make progress.

 

[ginkster]

It was this:

2 Way M8 8mm Battery Cable Power Distribution / Connector Jointing Box 120 AMP | eBay

Power jointing boxes suitable for joining together several cables. M8 Bolts (13mm Locking Nuts included). Sturdy PVC box with clip off lid.

www.ebay.co.uk

I realise I could have trouble due to the number of cables splayed on top of each other but gotta try it and see or spend forever wondering and never make progress.

You can cut extra slots out of the back or remove the post between the 2 holes on the front if you need more space. Don’t over think it!

 

[wallport]

I quite fancy the fuse solution which Meza suggested as this could just sit off the battery connector on top of the battery without other mounting:

A way to save some space with main battery fuse is a terminal mounted fuse holder:

https://www.amazon.co.uk/Battery-Terminal-Block-Voltage-Marine/dp/B0CCV6ZHQF

This one comes with a 250a fuse ie rated maybe too high. Does this matter and if so what size do I need? 150a?
(AFACIT these are MRBF Terminal fuses)

 

[TallPaul_S]

Plenty of choice on Amazon if you search for terminal fuse block.

https://amzn.eu/d/2zRf5Be

150a would be plenty for your needs, 100a even. You can always swap out the fuse.

You could probably just attach your existing positive terminals to this, so long as they reach.

 

[ginkster]

I quite fancy the fuse solution which Meza suggested as this could just sit off the battery connector on top of the battery without other mounting:


This one comes with a 250a fuse ie rated maybe too high. Does this matter and if so what size do I need? 150a?
(AFACIT these are MRBF Terminal fuses)

They are a good solution but personally I’d go for the Blue Sea one rather than a nameless one from eBay/Amazon. I’d fit a 100a fuse as the absolute highest. As you don’t have an inverter you will get nowhere near the BMS limit of 100a so go for the maximum protection of the cables.

 

[wallport]

They are a good solution but personally I’d go for the Blue Sea one rather than a nameless one from eBay/Amazon

I saw this and thought maybe wise to pay a few pennies more for quality. However, they seem to cost £34! Are you sure this cost is justified or can you suggest a cheaper source?

 

[meza]

I’m happy enough with the cheap one

 

[wallport]

Think I'm gonna go with this one on amazon:
X AUTOHAUX 1 Set 100A Battery Fuse Terminal Fuse Block Fuse 58V for Car Boat https://amzn.eu/d/fqVvnSu
Not sure if this make is good but at least it's not unbranded and has option to come with the 100a fuse.

 

[wallport]

Got a shipment notice today - battery originally expected end of month looks like it's arriving any day! I'm looking to speed things up now with that news.

Got the battery out and managed to get decent access behind the panel by getting the victron out of the way. Also found another screw low down at the back. This has allowed me to trace that battery select cable from the d250se. Guess what... it does go to the battery negative terminal despite the battery not being an AGM. Don't know what this will have done to my old battery but at least the good news is that I just need to reroute it to the positive terminal.

 

[roadtripper]

AGM needs a higher voltage under charge - so it will have been mildly overcharging a standard battery in the bulk and absorption phases both in terms of voltage but as a standard battery would likely not reach the voltage to trigger an end of phase it was probably also being charged too long and hitting the time out for those stages.

That might lead to a shorter lifetime.

 

[ginkster]

I saw this and thought maybe wise to pay a few pennies more for quality. However, they seem to cost £34! Are you sure this cost is justified or can you suggest a cheaper source?

I doubt there is a huge difference in the bracket but the fuse will be much better quality than a random Amazon/Ebay Chinium one. What testing or certification has the one you linked got or been through? Do you know that the fuse will actually work at 100a? Is a potential fire in your van worth a £20 saving? It is essential that fuses work as advertised (especially the one from a lithium battery!) so personally I stick to known, quality makes such as Blue Sea, Victron, Littelfuse. If you want to keep the cost down then go for a known midi fuse, from a reliable source instead. My Victron midi fuse cost about £3 plus the holder.

 

[wallport]

Is a potential fire in your van worth a £20 saving?

OK when you put it like that - I coughed!

BTW dumb question - the post is M8 on one of these but why is the hole 10mm?

 

[roadtripper]

If you watch this video (it's for a car but shows things very clearly) it's a wider to hole to ensure that the fuse stays centred on the insulated terminal bolt - the bolt is M8 but the shoulder at the bottom is much wider

 

[wallport]

This had me concerned

Did I snap it off while pulling the compartment open? Well the only things which are where I found this wire are the victron, the d250se and the mains box. I have identified all expected wires from the victron and the d250se, checked for any crimps they join to and think I can rule them out. I can't see any reason for a wire like this to go into the mains unit - all other wires going in there are 3 core mains cables with the exception of a yellow green earth cable and a 2 core cable.
I am hoping this is just a cable they ran in and never used. The other end disappears out of this panelling into an area which is inaccessible without dismantling the van.

 

[roadtripper]

It's not clear in the image but that looks more like a wirecutter cut end?

With the apparent gauge I doubt you'd have snapped off a crimp without knowing or feeling it.

For now I would just make it safe with some electrical tape or heat shrink.

 

[wallport]

Agreed - it looks flattened like it's been cut. Fingers crossed.

 

[ginkster]

BTW dumb question - the post is M8 on one of these but why is the hole 10mm?

I’d suggest it’s so they are also compatible with the larger capacity batteries that have M10 connections. The M8 bolts with the Fogstar 105 have washers that will work fine with an M10 connector.

 

[wallport]

So I have the Fogstar battery! However, the fuse and securing strap don't arrive till tomorrow so I haven't wired it in yet.

I'm wondering if some sort of lid/top cover just to insulate the top of the battery and terminals would be a neat solution rather than a box. Does such a thing exist pre-made or could I knock something up?