Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: rnli12 on May 02, 2015, 08:28:47 am

Title: LiPo Conversion
Post by: rnli12 on May 02, 2015, 08:28:47 am

Hi,
With many of my boats I am thinking of changing over to LiPos, most have Graupner ECO 600s in them running off NiMh 8.4v, with Action Electronics gear. What and would be the best option to convert to LiPo do I need to change motors and electronic gear?
What size and cell configuation?
Regards,
Rich

Title: Re: LiPo Conversion
Post by: inertia on May 02, 2015, 08:53:13 am

You don't have as much choice of voltage with LiPo packs, as each cell is 3.7v as opposed to 1.2v. That means that you can safely only fit a 2-cell LiPo pack (7.4v) because the next size up - 11.1v - will run the motors so fast that they will wear out/burn out far quicker.
You don't need any change to the electronics except maybe to fit a low-voltage alarm. These are available from many sources for around a fiver and simply plug into the pack balance lead.
DM

Title: Re: LiPo Conversion
Post by: rnli12 on May 02, 2015, 08:59:22 am

Thanks DM,
Any suggestions on the packs is it just 7.4v - 2 cell LiPo packs or capacity ?
Does 5000mah  2S1P 20C seem right?
Thanks,
Rich

Title: Re: LiPo Conversion
Post by: inertia on May 02, 2015, 09:23:02 am

Fit the highest capacity pack you can get it there. 5AH is currently the biggest, so go for that. You won't need any higher current-rating than 20C for Speed 600 ECO motors - I doubt they'll draw 100A! Component Shop are probably the best-known supplier of all things electrical for models.
DM

Title: Re: LiPo Conversion
Post by: essex2visuvesi on May 02, 2015, 10:40:37 am

Fully charged a 2 cell (7.4V) lipo kicks out about 8.4V

Title: Re: LiPo Conversion
Post by: slowcoach on May 02, 2015, 11:43:44 am

Hi
Hobbyk*** have 2s batts at 12,800mh/a which should last a long run time without needing to worry about low voltage to much but bring boat in now and again to check. The main drawback is price

Title: Re: LiPo Conversion
Post by: Subculture on May 02, 2015, 12:56:10 pm

Don't forget you can also get LiFE po4 batteries, they offer a lower cell voltage of 3.2-3.3 volts per cell. So a 3S pack would give you about 9.6-9.9 volts. I expect the 600 motor will handle that.

Title: Re: LiPo Conversion
Post by: McGherkin on May 02, 2015, 02:38:57 pm

Quote from: slowcoach on May 02, 2015, 11:43:44 am

Hi
Hobbyk*** have 2s batts at 12,800mh/a which should last a long run time without needing to worry about low voltage to much but bring boat in now and again to check. The main drawback is price

This. My 4S 14,000mah lipos are great! The Turnigy Multistar lipos are great for us as we tend to want loads of capacity at not huge amp draw, so we don't tend to worry about 'only' having 10C discharge - on my batteries that's 140amps each!

And as essex2visuvesi pointed out the fully charged voltage is 8.4 volts in a 2s Lipo.

Title: Re: LiPo Conversion
Post by: rnli12 on May 02, 2015, 03:03:18 pm

Thank you for your responses, I will give the 5000 2S 7.2v a go and see if my motors last, if not will swap out for brushless.
Thanks agian.
Rich