'Safe' parallel charging boards

I parallel charge my lipo batteries and from day one have used so called 'safe' parallel charge boards, the 'safe' aspect comes form the use of fuses on the main power rail, and resettable polyfuses on the balance circuit. They cost more, but my thinking is that should anything go wrong, i.e a short, the fuse will go hopefully saving batteries and charger.

Alas, quality control can undo all the good intentions of the design when one of the main power rail fuses has a solder bridge connecting both sides of the fuse together.



My guess is that with a 5000mAh 6S battery if I have a short the fuse and solder bridge will both go, but it's irritating to see that there has obviously been no testing or no visual inspection, and the product is being promoted as "safe"!

In future I think it would be prudent for me to test any charging boards as soon as I get them.

I assume you've removed the bridge now?

Not yet, it's the one I used when my batteries had 4mm bullet connectors, I'm using a different one at the moment for my batteries with 5.5mm connectors. The reason for digging it out was to make up some 4mm to 5.5mm leads so I can use it again. I was dusting it and out of curiously opened it up too have a look inside!

I've contacted the company I got it from just to let them know that their QC is a little iffy, but I have no intention of sending it back as it's an easy fix, I very much doubt I will hear from them, the hobby king version I got is actually a little neater looking, and no solder bridges!

Chris
Rather than make adapter leads (where an additional / inline connection could short) have you considered direct soldering a 4mm male bullet to a 4.5mm female then heat shrink

Also - have you got one of these to remove the excess

www.maplin.co.uk/p/white-box-de-solder-p...CK49ECFWcq0wodG10AXg

Hi Kevin,

I'd not thought to do that, I'll have a play.

I've got a de-soldering pump, not as nice as that though, as in mine's not clear. By the way, Mapins seems to do the exact same pump for £8.99 www.maplin.co.uk/p/maplin-de-solder-pump-n40ch so good find at 66p from the same place!

I never really understood the technology or safety of parallel balance boards. The first pair of packs I connected to one resulted in the tracks on the board vaporising. Surely if one battery is at a higher voltage level to the other when they are connected, it is going to dump every amp it can into the lower one to bring it to the same level - and if the track thickness allows, this could be hundreds of amps?

I have never charged packs in parallel.
Most battery chargers recommend you connect the balance lead first followed by the power leads. If i were to parallel charge, common sense would be to first connect the power sockets only and allow the overall cell voltages to stabilise before connecting the balance leads which would reduce the initial high current surges but certainly not eliminate them. I don't know what the polyfuse reaction time is but as they are a PTC device they obviously need current to heat before their resistance increases. - Hence your vaporising circuit tracks !

kevinross wrote: I have never charged packs in parallel.

Nor me! I have a 4 channel charger, that is 4 of same or different batteries and technology charging all at same time.

Nor me either , I have 2 chargers & always balance charge after each usage.
However what is "interesting" is the different cell voltages given on the charger compared to
readings on so called battery checkers. Different brands also giving different readings.
It would be interesting to know if anyone has carried out any comparisons using laboratory
grade equipment.

Colin.

I always balance charge, at the end of the day I charge the batteries back up to storage voltage independently, when I come to charge my batteries for a days flying they are all essentially at the same voltage, and so I parallel charge them. I connect the power leads first.

Colin, you'd have thought that voltage readings would be very similar from measuring device to measuring device, but like you I see variations. I guess it comes down to what you're prepared to pay for. If you look at electrical components they will state their accuracy, so a carbon composition resistor might have an accuracy of +/-5%, metal film resistors might be +/-0.1% one will be more expensive than the other. I only use the battery checker to check which is the full battery.