Model Boat Mayhem

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: Covert on June 28, 2013, 09:45:09 AM

Title: silly question .... 6v battery voltage
Post by: Covert on June 28, 2013, 09:45:09 AM
so im used to using lipos and the like with other rc models and i have fitted a 6v 4ah battery to my raf vospers boat, how do people know how much use they can get out of the battery before it goes flat and your left stranded in the middle of the lake?
 
is there some kind of voltage detector that beeps when it gets low?
many thanks for your help.
 
(ps nice to have the forum back) :-))
Mark.
Title: Re: silly question .... 6v battery voltage
Post by: inertia on June 28, 2013, 10:25:40 AM
Mark
Why fit a big heavy battery like that to a planing boat? You'd be better off with a 2S LiPo if that's what you're used to using - much lighter. The pack may not last quite as long as the SLA but the model won't trundle round the pond like a narrow-boat. Realistically you'd only get to use about half the capacity of the SLA before it required recharging i.e. 2AH.
As far as I'm aware there are no low-voltage alarms available commercially for SLA batteries.
Dave M
Title: Re: silly question .... 6v battery voltage
Post by: Covert on June 28, 2013, 11:14:31 AM
thanks dave , i suppose i could use a lipo, ive got an nice 5000mah one that i could use , the boat is fitted with a 6v goldfire motor though so would the esc regulate that to 6v or would it give it the full 8.4v
thanks for the help.
 
Title: Re: silly question .... 6v battery voltage
Post by: inertia on June 28, 2013, 11:32:13 AM
Mark
ESCs always apply the full voltage; they just switch it on and off very quickly (See article here for further info http://www.action-electronics.co.uk/art.php (http://www.action-electronics.co.uk/art.php))
I'd be tempted to use a motor with a higher voltage rating as I have no experience of the one you mention. The Graupner Speed 600 8.4v (#3301) should do the job and will probably fit the same mount as the one you have. Gliders currently have stock at just over a tenner apiece.
Dave M

Title: Re: silly question .... 6v battery voltage
Post by: Covert on June 28, 2013, 05:12:15 PM
Shame there are no voltage alarms as that means i have to change my battery and motor just to get one  :((
Title: Re: silly question .... 6v battery voltage
Post by: malcolmfrary on June 28, 2013, 06:18:34 PM
Typing "battery volts alarm" into google reveals that the world is awash with ready made devices for lipos, and a plentiful supply of diy ones for any other type.  Most of us users of SLAs and NiCed/NiMH batteries note that after a time, either the boat won't go as fast, or it needs the stick pushing further forward to get the same speed.  That is a sign that its time to come back in and check for weed on the prop.  Since the boat is to hand at that point, the voltage can be checked quite easily.
Title: Re: silly question .... 6v battery voltage
Post by: Covert on June 30, 2013, 09:34:34 AM
Would this work?
It would save me taking my multi meter with me everytime i go out


[font=.HelveticaNeueUI]http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251297303170[/font]
Title: Re: silly question .... 6v battery voltage
Post by: essex2visuvesi on June 30, 2013, 10:00:32 AM
I have one of these wired into my huntsman
http://www.ebay.co.uk/itm/390567117059?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 (http://www.ebay.co.uk/itm/390567117059?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)


Not an alarm as such but at least you can monitor the voltage.
Tests with a very expensive multimeter shows that it reads 0.1v low (so if ity reads 10.2v the battery is actually 10.3v)
Title: Re: silly question .... 6v battery voltage
Post by: malcolmfrary on June 30, 2013, 10:11:31 AM
It has every chance of doing the job - just depends on how well the designers calibrated it and what they considered as good, indifferent and bad.
Title: Re: silly question .... 6v battery voltage
Post by: Netleyned on June 30, 2013, 10:16:59 AM
Would this work?
It would save me taking my multi meter with me everytime i go out


[font=.HelveticaNeueUI]http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251297303170 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=251297303170)[/font]


I use these in my yachts on 6V AA packs.
They give a fair indication of the voltage.
You need to connect it across your battery as plugging it in to a spare channel of your receiver
will only show the BEC voltage of your esc or rx battery.


Ned
Title: Re: silly question .... 6v battery voltage
Post by: Covert on June 30, 2013, 11:24:45 AM
I have one of these wired into my huntsman
http://www.ebay.co.uk/itm/390567117059?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 (http://www.ebay.co.uk/itm/390567117059?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649)


Not an alarm as such but at least you can monitor the voltage.
Tests with a very expensive multimeter shows that it reads 0.1v low (so if ity reads 10.2v the battery is actually 10.3v)


thanks think i will go for one of these! :-))
Title: Re: silly question .... 6v battery voltage
Post by: essex2visuvesi on June 30, 2013, 12:22:07 PM
Im going to install mine on the dashboard of the boat