Team MedBots

[adz600]

From memory they are 5w check you coil wattage, prob be ok with the heatsink but do the math to check

[Max]

Well for 84p more I can get this one which goes up to 6a, 100w so should be fine:
http://www.banggood.com/6A-150W-DC-D...r-p-80723.html

Doesn't sound like I can really go wrong for a couple of quid.

[maddox10]

I use the Deal Extreem booster. Works fine, but is a tad on the big side.

[Max]

I've been trying to get my heavy running again now that exams are all over, having wired up the drive I've found that the motors keep cutting out. I'm using a Vantec RDFR47E Speed Controller, one bosch 400 on each side, 10:1 gear ratio, 10" go-cart wheels and a 12v SLA battery.
It happens on the bench if I push it quickly to full forwards or reverse and also when the robot is on the ground if I don't bring up the power very very slowly and even then it cuts out when I reach about half speed.

Anyone got any idea what's going on?
I thought it could be current limiting but I can't believe my setup is drawing 70A continuous, 220A start-up.
Is it possible that the battery voltage is dropping bellow 9v (the minimum voltage for tr esc)?

[plargen]

have you tried a separate battery to the rx

[Max]

have you tried a separate battery to the rx

Yeh I'm using a separate receiver battery.

[plargen]

is there a BEC built into the esc

[blazerbotics]

Will be battery voltage without a doubt, especially if its a cheap battery.

[daveimi]

Put a multimeter over the battery and post up what it says.

[Max]

Just tried it with my fw lipo and it worked really well, in the 30s I had it running the wires from the lipo and the deans connector itself got very hot but at least it worked!
So looks like I need to try and source some better quality cheap batteries. May try and get some second hand Nicads or Nimhs or else wil have to use lipos but would rather not.

[maddox10]

2 Bosch 400 @12V is 80A nominal and about 200A stall.

A 3 or 4S LiPo 8000mAh 30C will do nicely.
And for about £40 @ Hobbyking you can't go that wrong.

[Max]

2 Bosch 400 @12V is 80A nominal and about 200A stall.

That's overall right, not 80A nominal per side?
I also think if I go lipo I will get 2/3 lipos around 4000mah that way I can wire them in parallel so have 3 times the wires so hopefully they won't get too hot.

[Max]

Just tested it with a 12v car battery and it doesn't seem to do anything at all, the connector doesn't spark at all when connected unlike when the other SLA is used. I checked the battery and connector with a multi-meter and got a voltage so I'm stumped why it doesn't work. Anyone any ideas?

[maddox10]

If a SLA is "empty", it still can give V, but not A. Did you measure during and after linking up?

And of course, wires and connectors can come lose

[Max]

Have finally managed to get the heavy driving! See video bellow:
http://youtu.be/EWGIPxjdkDM

It still cuts out from time to time, I think this is still the battery voltage dropping too low, I have another SLA so will charge them both up and put them in parallel and hope they can provide enough current without the voltage dropping too much.