Battery retention methods

[Ron Gray]

OK, so here’s my situation. I have a largish warbird that I had hoped to power with IC but I’ve decided not to wait any longer for an engine and am going down the leccy route. I should add here that it’s a twin engined warbird and in order to get the cg in the right place, the engine batteries will be vertically mounted in the engine cowls behind the engine firewall. Each fibreglass cowl has a part former in such a position that I cannot form an access hatch in the top or sides of the cowl, it has to be underneath.

Bearing the above in mind, are there any suggestions as to how the batteries can be held in place yet can still be changed? The batteries are 6s 5000 so are a bit of a lump and I don’t think a simple Velcro strap will be sufficient.

[Dickw]

I use 6s 5000 packs in a Sebart Pitts. The battery is retained by two velcro straps - one round the middle of the battery and one round the length of the battery. No problems in several years of throwing it around in all directions.

Packs can be changed very quickly.

Dick

[Old Geezer]

Strip of self-adhesive Velcro (hook side) along one (smooth) side of LiPo - strip of self-adhesive Velcro (loop side) stuck to appropriate site in airframe and being a belt and braces bloke a Velcro tie around the battery, especially a brute the size you're contemplating to stop it sliding off/pulling away under flight loads. You will need to prepare the surface you're sticking the loopy Velcro to, I smooth a thin layer of epoxy on the surface of your battery mount just thick enough to seal the underlying ply(?) and produce a glossy surface as it cures.

As an afterthought - the very best "Velcro" is that supplied with Multiplex kits, almost too strong a grip twixt hook tape and loop tape.

[Brian Stevenson 1]

Posted by Ron Gray on 19/10/2019 22:39:07:

….....Bearing the above in mind, are there any suggestions as to how the batteries can be held in place yet can still be changed? The batteries are 6s 5000 so are a bit of a lump and I don’t think a simple Velcro strap will be sufficient.

Even if you 'prepare' the surface with a glossy finish I have found that the self-adhesive Velcro can become detached. - it starts to unpeel from the point it leaves that surface and goes through an approx. 90 degree angle around the battery. Also you can't use a one-piece loop of Velcro as you need hooks on one part and loops on the other..

So self-adhesive or not I use countersink screws through the Velcro, screwed down hard so none of the screw heads are protruding to damage the battery. Also note that Velcro eventually wears or 'clogs up' and needs replacing so make sure you have future screwdriver access to the screw heads Overlap the two sorts of Velcro and then put screws through both. This way there is no sideways pull on the screws.

Strength? It's FAR more than you will every need. You loosen Velcro by grabbing an exposed end and 'unpeeling' it. A battery (or any other object) cannot do this. Also make sure the overlap is as large as possible.

Always do this with loops of Velcro around the battery.. Don't waste your time with putting one sort on the battery and the other sort on the surface you want to attach it to. It's next to useless and may well damage, or at least weaken, the protecting heat shrink covering on the battery when you try and pull the battery off...

I've used batteries up to 10S 5000 mA and they have never become even slightly loose. Not even with cheap ASDA non-genuine velcro.

[Chris Walby]

Why not make a battery cage on the fire wall that the battery slides into (with ventilation holes) that is retained by a ply cover (Nylon screw). Just make the cover slide and lock or secure in such a way the battery cannot be removed/fall out by accident.

Batteries can be dropped out for charging, you don't have mess around trying to get your finders into the cowl get the Velcro secure. Nothing wrong with Velcro straps as long as you can get some reliable tension and ensure the battery can't slide.

+1 comments about Velcro stuck to lipos damaging the battery covering.

[Ron Gray]

Thanks for the replies guys. On all of my other leccy ‘planes, I use Velcro to both stop batteries sliding with Velcro stuck to both battery and tray plus Velcro straps around the batteries. This works fine including on my F3a. But, all of these have good access to the batteries and all of them have batteries that are horizontal on a battery tray. The new model is different in the the batteries will be mounted vertically plus there is no access to the side of the batteries only the end. Yes they will slide into a ply housing / box to locate them but I’m not too sure that a Velcro overlapping strap with a max of 30mm lap will be sufficient, plus it may well be difficult to get fingers into the cowl to undo the Velcro. By the way, the access hatch is roughly the size of the cross section of the batteries.

[Trevor Crook]

I've used a similar method to that described by Chris in my Typhoon, except the battery is retained by a glued-on velcro strap that is pulled tight across the battery's bottom end. This is then covered by a hatch, which is retained by a tab on one edge and a swinging latch on the other. Nothing has ever moved in scores of flights

[Trevor]

A ply retaining plate, with a pad of foam glued to it. press the plate onto the end of the battery, then rotate or slide it to engage in suitable slots cut into the sides of the battery box.

The downside of this method is that if your batteries vary in length at all you'll have to carry a few additional bits of foam to take up the variation.

Trevor

[Brian Stevenson 1]

Posted by Ron Gray on 20/10/2019 07:37:15:

Thanks for the replies guys. On all of my other leccy ‘planes, I use Velcro to both stop batteries sliding with Velcro stuck to both battery and tray plus Velcro straps around the batteries. This works fine including on my F3a. But, all of these have good access to the batteries and all of them have batteries that are horizontal on a battery tray. The new model is different in the the batteries will be mounted vertically plus there is no access to the side of the batteries only the end. Yes they will slide into a ply housing / box to locate them but I’m not too sure that a Velcro overlapping strap with a max of 30mm lap will be sufficient, plus it may well be difficult to get fingers into the cowl to undo the Velcro. By the way, the access hatch is roughly the size of the cross section of the batteries.

A simpler way is just to make a strong hatch with a strong surround. Maybe which is attached to the firewall/other structure rather than the cowl. Just cut out the matching part of the cowl and glue it to the hatch..

For a hatch catch just use a spring loaded sliding piano wire pin, equally strongly attached. (You can no longer get the Flair ones and they were a bit weak anyway, but they are simple enough to make.) Despite my long post about Velcro that is what I mainly do now and it has never failed. It really doesn't matter if the battery rattles up and down a little. If it bothers you put a bit of soft foam on the back of the hatch.

[Rich too]

Posted by Chris Walby on 20/10/2019 06:39:04:

Why not make a battery cage on the fire wall that the battery slides into (with ventilation holes) that is retained by a ply cover (Nylon screw). Just make the cover slide and lock or secure in such a way the battery cannot be removed/fall out by accident.

Batteries can be dropped out for charging, you don't have mess around trying to get your finders into the cowl get the Velcro secure. Nothing wrong with Velcro straps as long as you can get some reliable tension and ensure the battery can't slide.

+1 comments about Velcro stuck to lipos damaging the battery covering.

You can make a simple cage using Velcro, it’s a method I’ve used and I believe I came across on YouTube. You then glue, fix or screw the Velcro to the model.