Dualbatts

[jimbo]

I know this has been done before on the old forum so apologies.
What is the best set up for a dual batts. In the case where both batteries are plugged into the receiver, a diode set up was mentioned to stop the 2nd battery charging the first battery. I have a new model with a jeti magnetic switch with two inputs to the rx from both batteries. Does this switch ensure that the batteries discharge evenly?
My fox has the dual diode with a single feed into the rx. Is this switch which is 30 quid a nice solution. Be interested to hear your thoughts. Ta All..

[spike spencer]

Hi Jimbo
The old Forum is still there and the search engine still works (but not for much longer ?)
e.g.
http://scalesoaring.co.uk/cgi-bin/yabb2 ... 1379361785
There are many other links to find if you use the search term "Dual Battery"

"My fox has the dual diode with a single feed into the rx. Is this switch which is 30 quid a nice solution. Be interested to hear your thoughts."
Regardless of the price of the switch, redundancy stops with the singe feed into the Rx !
Your own previous comment in the link above:
"One of the major points of failure is the connector into the RX, it worries me to have an expensive model reliant on a simple plastic Futaba connector in my case. Adding a dual battery via a BEC is fine, but you're still reliant on that little flimsy plug."

"... ... ensure that the batteries discharge evenly?"
With or without diodes, as long as the two batteries are the same type, chemistry and number of cells, the load will take from whichever source is showing the higher Voltage. The batteries are therefore 'self-leveling' when under load.

I appreciate that "Wiggly Amps" is a mystery subject to many. Hope that helps to jog your memory from the extensive previous debate(s).

[jimbo]

Thanks 4 the link.
This is the switch in the model. Looks like it does what we need in this case (apart from regulate the voltage)
https://www.electricwingman.com/jeti-dp ... witch.aspx

[GordonT]

Jimbo - The Jeti switch will do what you require, as you've already established. However, best to disconnect the batteries from it for winter layup, as there's a very small amount of current being drawn when it's 'off'.

[jimbo]

Quick question, one of my 5 cells Nimhs has gone bad (wont take charge, i seem to of lost a few batts this year ), i have a spare 4 cell of suitable capacity, which i could use. The question can i use this battery, i believe the model in question (my fox) has one of those diode backers to swop between batteries, or will the 4 cells be too low a voltage for the other 5 cell.
Ta,

[geoff_crew]

I think it's too low as I believe the diode brings a 5 cell(6V) down to just over 5V but I'm sure others will give sound advice.

Geoff

[FrankS]

you can't mix different cell counts, these redundant switches work by selecting the battery with the highest voltage, so your 4 cell battery wouldn't take over until the 5 cell had discharged down to the 4 cell battery volts.

[Peter Balcombe]

As Geoff says, if the battery backer uses diodes to isolate the batteries from each other & select the highest voltage one, the diodes will drop around 0.5V or so if a Schottky diode or about twice that if a normal diode. The only way to tell unless you can see the diode part number is to measure the backer output voltage. However, the diode voltage drop increases as current draw increases, so measuring voltage after the backer without servos moving will not show the real story.
Thus with a 4 cell pack, you are likely to be at only 4.3v at best with the battery on nominal voltage (possibly 5.5v or so fresh from a full charge).

[jimbo]

Ta all,
I seem to have lost four 4 and 5 cell batts this winter in the garage. I have some sanyo eneloops AA and AAA but these seem to have survived the cold in the same garage, i wondered if these are less suspectible or perhaps just a better quality battery, the failed ones are ones i bought from component shop, all AA and AAA (non eneloop).

[cadavis]

I have had the same problem with 5 cell nimh 3000 7.2v bats and 3800 4 cell nimh Over lander "C". Not been fast charged or discharged looked after very well, but do not last as long as the old NiCad's.
So now only use Li-po's, not had a problem.

Colin.