Lead Acid Battieries

Hi All Before my stroke i had a pretty extensive knowledge of electrics but now there is only a glimmer remains. The same as foreign languages, i could speak German, Italian, and a smattering of Spanish, and Swahili (No i'm serious).
Anyway to the point, Lead acid batteries 12 volt. Do they increase or decrease in power by lets say 2.3Ah or 7Ah?. I bought a 12 volt 3.Ah, and it's too powerful for my needs.
I am sorry i cant explain it better than this but i am sure you will get my drift (I hope so)
Cheers ahead of time

Tony - its not the amp hours (Ah) that matters - that really only gives you an idea of how long a battery might last. The higher the Ah, the longer it will last in any given boat. If you say your 12volt battery is too powerful, you need to try a 6 volt one. Its the voltage which equals power - put simply.

Hope this helps.

Barrie

Cheers Barrie. I'm a bit confused, I have a 12 volt battery from an old big radio controlled car, and that works fine but a new one i bought melted the bloody wires. The first photograph is one from the old car, the second one is the new.

Tony,

Its possible that the old one is no longer delivering 12 volts. That is the only explanation I can think of. Does your charger work for 6 volt batteries? If so I will send you a 6 volt to try and see if you get the speed you require without melting the wires. PM me you address if interested. You can have it for free - I don't need it anymore, and I have another in any case.

Barrie

amps = run time

volts = power

over voltage = dead motors,

over amps = dead esc & cables

Hence why most motors state max voltage range, eg. ''graphner 400 speed 6v'' needs 6v, same but 7.2v can run up to 7.2v with out burning out however you are able to up the voltage to get more speed from a motor but at the reduced life span of the motor so bare this in mind = hot motors normally = to much voltage or being over propped, but then again it could just be hot from a long run which in that case some type of cooling should be considered. (trial and error here, try reduced prop size first b4 modding the boat for cooling, providing that the voltage and esc are correct for your setup)

if your wires are burning out then your pushing the esc and motor to far, which means the wire may be the wrong gauge size to take the amps the esc and motor(s) are drawing

( i tend to use the 2 core strand mains cable ( just cut it from the white sleeve), it just never burns out
Don't use the solid core cable its just a pain in the butt to wire with along with becoming brittle very quickly which will be a re-wire job in no time.

be sure to check the motors max voltage limit, and use only the correct battery size (6v, 12v 7.2v etc)that its matched to the correct size AMP esc & your cables are able to take the amps!

the issue with older LA battery's that they do have a shelf life, and will not hold the full voltage for long or charge to the full voltage once they reach a certain age, this can be reduced with good battery maint, proper discharging and recharging as well as store charging for the winter.

New battery's can be over voltage, such as i have a few 12v LA that actually read out at 13.2V!! fortunately, most esc can handle that slight over voltage with np. (mtronic escs can take 14v np constantly)

Amps are what burn things out such as esc and cables.

Electrician's will say volts hurt, amps kill!

This is why USA cops use tazers with up to 50,000 volts, they hurt like hell but cos there only like 0.02-0.04 amps they wont kill you with a single stun! (google yourself for proof!)


simples

Now that is what I like, A good simple explanation of the black art!!

Well thank you RR for that . My ESC can handle up to 12 volts, i bought it for that capability. May be the Prop is over sized?, in fact i think it is, it a Dynamic prop 60 mm. Windy sent me a 755 motor it works perfectly. I think it's several problems all combined. It's an heavy boat, i haven't weighed it yet but it's a few Kgs. I will sort it out, i always do given time.

Hi Tony, drop the prop size down to a 45mm or 50mm which will let the motor rev higher with less current draw 60mm is a bit big. You probably won't notice a drop in speed either....

W..

Already Done Windy my old mate

Footski wrote:

Now that is what I like, A good simple explanation of the black art!!

Could the esc have anything to do with wires melting? I hear some are giving the peak amps in the sales spiel and not the continuous ratings. If I am way off the mark - it wouldn't surprise me at all
Dave

Hi Dave i don't know about that, it's a Viper 25 so it should handle 12 volt, but i think i got it cracked now. Cheers

Just a note on prop's

Tony your using a 755 motor with a 60mm prop which really in theory should work fine at low revs! but in this case i suspect that this will be the cause of over heating the motor which will lead to blowing the esc (and wires) remember to fuse the esc to prevent a pricey repair!!! ( recommend a 20amp fuse on the positive of the esc terminal)

The Esc your using a viper 25 amp is fine with the 755 motor types, both motor and esc can handle 12v np ( and the esc can actually handle 14v easy)

But just to give you some idea of a similar setup i will direct you to read my Dolphin rebuild, In that build i'm running a torpedo 850 motor with a 30amp esc running 12v 3.3amp LA on a X45 prop (with an option to go up to an x50) which will give me a an ideal plane speed.
The Boat is 36" long (give or take an inch) and weight so far is up to 6kg inc the LA battery! (the battery alone is nearly 2kg!) the boat is not yet finish but i expect the finish weight to hit the 7kg mark.

I would also like to point out another project that a club member is building, model slipways Maggie M, his setup is a 15 amp esc, running 12v on a MFA 2.5:1 geared motor (this is the 540 motor size) on a 3 blade 40mm prop, this model is over 15kg in weight ( most ballast) and yet the model can move about the water well and at a fair speed (way over scale!) so some times weight is not a big a problem as you think, weight issues really only effect boats which need to move at speed, as once they get moving they tend to get up to speed reasonably well.

This can be explained further on another boat i own which is the Graphner Weisel mtb the boat is 36.6" long 8" wide, the kit recomended running 3, 540 motors on 7.2v...

well i scrubbed that for a scale top speed, which i achived like this.

the boat is tripple propped,
the center prop is free running (no motor fitted)

the LH and Rh props are hooked up to graphner 400 6V motors on x35 props running 10amp esc each and on 6v 4.5amp LA.
the motors do run warm however so i know i am pushing it a bit hard but since there only 400 motors there cheap enough to replace as and when.

The boat is quite heavy just over 7kg with its ballast yet the boat can get up on the plane so easy with the slightest touch.
i could up the speed further by just hooking up the central prop with a further 400 motor and esc, but this setup gives me a great scale speed. i'll try to get a video uploaded of it running next time i get it out so you can see.

sometimes is just trial and error other times you just know what you need but if in doubt ask!

Thank you RR for that interesting, and illuminating read, amazing. As i said before when i was healthy, and didn't have this stroke to slow me down the problem i am now encountering i would "think what problem"?, and have it sorted in no short shrift (If you get my meaning). Now i have to think about things more but i get there in the end. I am much appreciative of you taking the time, and trouble of typing all that in. I am using a 15amp in line fuse on the + side, i will change that for a 20amp fuse. I will only use the boat on low revs when i'm using the more powerful battery, it is high power anyway, and new, the other battery is no problem. Cheers my friend

Tony

Bloody hell I have weighed the Boat, and i got a surprise, i always knew it was a heavy boat but Geez. It weighs 16.4 pounds or 1 Stone 2.4 pounds, 7.4 Kgs, and that's without the battery. The battery weighs (New battery) almost 3 pound, and the old battery nearly 2 pound, and it still floats .