Deep Cycle Battery Choices.

jeffish
Jedi Seadog
Jedi Seadog
Posts: 3716
Joined: Sat Sep 03, 2011 8:25 am
Location: Darwin

Re: Deep Cycle Battery Choices.

Post by jeffish »

Good info Ronje :mrgreen: Thanks


NinjaFish
Jedi Seadog
Jedi Seadog
Posts: 888
Joined: Sun Aug 27, 2017 8:20 am
Location: Darwin

Re: Deep Cycle Battery Choices.

Post by NinjaFish »

Crikey. Just spent a few weeks learning all this in a training course(s) and here it is in 10 minutes!

You have a way with words Ron :cheers:
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

Hope its of use to you guys.

Last little bit about basic charging. The rule is get a smart charger and then you don't have to be smart.
Charging batteries.pdf
You do not have the required permissions to view the files attached to this post.
Regards
Ronje
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

Anybody been playing around with lithium - ion batteries?
Regards
Ronje
slug
Jedi Seadog
Jedi Seadog
Posts: 997
Joined: Mon Mar 19, 2007 8:01 am

Re: Deep Cycle Battery Choices.

Post by slug »

ronje wrote: Thu Aug 08, 2019 6:52 pm Anybody been playing around with lithium - ion batteries?
Not with marine, but recently delved into the world of battery powered garden implements with a Victa 82v Hedger.

I was that impressed with result (nearly 12 months and haven't had to recharge the battery yet - although only used probably mthly for 1/2 hour or so at a time) that i've just added the wipper snipper/line trimmer skin, and that's also been a revelation.

Old mate told me recently that I shouldn't leave the battery in the unit when not in use, although it doesn't appear to have impacted performance. I'm keen to hear advice on whether to completely discharge prior to recharging, whether to leave on charge constantly when not in use, etc, etc
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

Its OK to leave Li-ion batteries on a suitable charger like the ones that come with those tool batteries.

The bad name that these got was due to the use of cobalt in the anode. High power density characteristics led to thermal runaway and fires/explosions.

Manufacturers changed to phosphorus impregnated iron anodes with less power density and used polymer separators so they seem to be on top of things now.

Due to extra product development work and tighter tolerances they're more expensive to make and thus buy.

A Li-ion battery is actually a pack of smaller individual cells packed together (2 v cells) into a case so it looks pretty much like other batteries. Normal batteries also have 2 volt cells but they're much bigger.

They do have self discharge like other batteries if left on a shelf and not charged.

There is one problem and that is the name given to that type of construction.

Lithium ion batteries work off the passage of ions (positive charges) to the anode (lithium compound). First models were lithium/cobalt anodes.

Newer one are lithium iron-phosphate anodes.

So now we have a lithium ion battery made with a lithium iron anode.

Different words and meanings, different spelling but pronounced the same way.

Can be confusing.
Regards
Ronje
User avatar
theodosius
Jedi Seadog
Jedi Seadog
Posts: 3258
Joined: Mon May 18, 2009 10:46 pm

Re: Deep Cycle Battery Choices.

Post by theodosius »

Still too pricey at the moment but the weight is attractive
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

They can be used to much deeper discharge cycles and are quicker to charge.

Guide friend of mine John Haenke has a new guide boat and uses a pair of Li-ions. Will keep an eye on how he fares.

Yr right about the weight particularly if needing 2 batteries for 24v electric.

They also don't like cold weather but we're not likely to run into the low temps that they don't like.

Proper charging seems to be something that has to be looked at as we're talking o/b or vehicle alternators.
Regards
Ronje
User avatar
theodosius
Jedi Seadog
Jedi Seadog
Posts: 3258
Joined: Mon May 18, 2009 10:46 pm

Re: Deep Cycle Battery Choices.

Post by theodosius »

Would a dc dc charger like the Sterling charge LiFePO cells?
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

I reckon they'd be OK as they're basically a smart charger with the 240v input side replaced with some smoke and mirrors 12v circuitry.

That'd be better than a "dumb" alternator like that on a vehicle or o/b but comes at an extra cost.

I guess that the upside is that a Li-Ion will genuinely do all 3 battery applications rolled into 1 (Cranking, marine and deep-cycle). Straight from the Charlie Coyote hardware store ( the ACME Company).

Need to have a look at the BMS (battery management system) they talk about a lot.
Regards
Ronje
User avatar
theodosius
Jedi Seadog
Jedi Seadog
Posts: 3258
Joined: Mon May 18, 2009 10:46 pm

Re: Deep Cycle Battery Choices.

Post by theodosius »

Ronje how did your mate go with the 2 lithiums?
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

They're going OK.

John sold the business (Guided Fishing Down Under) and went grey nomad. Only guides intermittently now whilst supplementing income "on the road".

Kept the new boat with the lithiums to do that.

Had no trouble.

Fishing is in the blood as it is with wife Peta. They'd be back up in the NT by now if it hadn't been for Covid. They're still in Qld at moment.
Regards
Ronje
User avatar
theodosius
Jedi Seadog
Jedi Seadog
Posts: 3258
Joined: Mon May 18, 2009 10:46 pm

Re: Deep Cycle Battery Choices.

Post by theodosius »

Cheers. I'm sorely tempted but prices are still a bit too high for lithiums that you can run in 24v and that can output over 50A continuously (minn kota 80). With the sizes 100AH seems like overkill and 50 not enough. There's a 60AH 24v unit which looks good from solarking but it can only output 40A
ronje
Jedi Seadog
Jedi Seadog
Posts: 2439
Joined: Sat Feb 14, 2009 5:23 pm
Contact:

Re: Deep Cycle Battery Choices.

Post by ronje »

I wouldn't get too excited about max current figures.

Motorguide call their speed controller a Variable Digital Control and Minn Kota call their's a Maximiser Speed Control.

Neither of them feed 40- 50 or 60 amps continuous current..

They use a "pulse feed" system which sends pulses of current per second to the motor.

The more pulses per second, the faster the motor goes (and thus more power delivered to the prop).

The number of pulses per second is called the pulse repetition frequency (PRF) and the REAL current delivered is a lot less than the max quoted.

Its actually the effective or average current.

Like in a sounder the power is pulsed to the transducer (sounder's version of an electric outboard's speed controller feeding power to the prop motor).

Sounders with 4,000 watts (4KW) of power are common.

A genuine 4 KW sounder would have a current draw of 4,000 /12v peak current. However the average or effective power is actually 500 watts not 4,000 watts (Divide peak by 8 to get effective power).

So should your 4 kw sounder have a fuse of 4,000/12v = 333 amps? No that's as silly as it sounds.

Should it have a fuse of 500/12v = 42 amps. ? Sounds just as silly when you look at the fuse that comes with the sounder.

That fuse will be 1.5 to 3 amps or so.

How can that be? Its because the peak power is pulsed to the transducer.

The longer the pulse, the more the power. The shorter the pulse, the less the power and the less the required average/effective current draw.

Sounder pulse lengths are in the order of 1/1000 of a second long so the current is considerably less (like a max of 1-3 amps). Hence the small fuse.

Ditto with pulsing an electric motor. Short duration pulses are fed to the prop motor which keeps the average or effective current draw well below the peak figure.

In addition, because you've got double the voltage ( 24v instead of 12v), the current draw is halved.

So a 240 watt electric motor will draw 20 amps @ 12v. (240 /12v)

If that 240 watt electric motor is a 24v version, then it will draw 240/24v = 12 amps. Half the current (or so) with all things being equal.

Does that mean a lower capacity AH battery will suffice? Yep but you'll need two of them in series to get the 24v needed.

If 2 x100AH batteries are connected in series (+ve on one to -ve on the other and the outside +ve and - ve to the load) you have the equivalent of a 100 AH battery @ 24 volts. Remember that the necessary current draw will be halved at 24v thus allowing a reduction on battery capacity if you wish.

If you connect them in parallel (+ve to +ve and then to the load and -ve to -ve and to the other side of the load) you have the equivalent of a 200AH battery but @ only 12V. Never go flat and last forever if driving a 12v electric.

What determines a good battery capacity is knowing how much effective current the motor draws (not the peak). Only THEN look at battery capacity needed.

Trolling motor manufacturers are notoriously secretive about the current that their motors draw. They don't quote watts for their motors (so calculations would be very simple) but instead quote thrust and voltage. Another layer of secrecy added to convert thrust to watts to confuse customers.

I had a list of measured current draw for various motor rpms for a common 12v motor floating around somewhere. It wasn't as high as what I've heard commonly quoted.

Still, the current (no pun intended) cost of lithiums is still pretty high so it might be irrelevant for your purposes anyway.

My head hurts now so I'm off to rest it.
Regards
Ronje
User avatar
theodosius
Jedi Seadog
Jedi Seadog
Posts: 3258
Joined: Mon May 18, 2009 10:46 pm

Re: Deep Cycle Battery Choices.

Post by theodosius »

Wow, cheers mate. Good info! Minn kota quote 56A at 24v, would still need to guess if the bms would switch off detecting at any pulse above 50A. It's a pain to turn one back on I hear
Post Reply
  • Similar Topics
    Replies
    Views
    Last post

Return to “Electronics”