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-   -   125a Pull safe on lead acid? (http://www.cruisersforum.com/forums/f14/125a-pull-safe-on-lead-acid-172286.html)

deepthought 06-09-2016 14:28

125a Pull safe on lead acid?
 
I have 6 trogan t-105s in 12v setup. Occasionally would like to run a kettle for 3-4mins it pulls around 125a when running. Is that going to damage the batteries? Is there a caclulation or way to tell what is the max safe amps I can pull? I know the AH etc.. Just not sure what I can pull in one go for a few mins with out damage.

Also I have between 60-80a of solar / wind going to charge that batteries. Is that too much and is that going to damage them?

Any help would be appreciated.

Thanks

svlamorocha 06-09-2016 14:44

Re: 125a Pull safe on lead acid?
 
When you run the kettle there will be a huge voltage sag. Lithium is the way to go for that sort of use.

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svlamorocha 06-09-2016 14:47

Re: 125a Pull safe on lead acid?
 
Almost any charge controller will protect your batteries from overcharging. This means you will not be able to use the 80A charge capacity in full.

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svlamorocha 06-09-2016 14:49

Re: 125a Pull safe on lead acid?
 
If you use default settings most controllers will ensure your batteries are undercharged and die soon. Read MaineSail's musings for gory detail.

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StuM 06-09-2016 15:55

Re: 125a Pull safe on lead acid?
 
125A = 1.5kW
6 x T105s (@ 1.5kWh each) give you 9kWh or 750Ah capacity.
In theory, 125A would drain then in 6 hours.

So you are talking about drawing less power than the "5 hour rate". Which is well within battery specs.

And you are looking at taking about 8Ah in total out of that bank.

(According to Trojan, they actually have 185Ah @6V at the 5 hours rate, so effectively have a 555Ah bank when drawing that fast)

As for the 60-80Amps charging. As long as you have a good charge controller, properly configured, then the more you can feed in, the better.

Scott Berg 06-09-2016 16:03

Re: 125a Pull safe on lead acid?
 
I routinely pull 200 amps for short microwave oven runs and other high current items out of a similar bank
That's what the batteries are made for


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StuM 06-09-2016 16:06

Re: 125a Pull safe on lead acid?
 
1 Attachment(s)
Quote:

Originally Posted by svlamorocha (Post 2207315)
When you run the kettle there will be a huge voltage sag. Lithium is the way to go for that sort of use.

Sent from my SM-G800H using Cruisers Sailing Forum mobile app


With good batteries, pulling at C5, voltage should drop to about 12.1V at 100% SOC.
If you get down to about 50% SOC, the voltage is likely to be around 11.5V.

Nothing to be overly concerned about.

deepthought 06-09-2016 16:09

Re: 125a Pull safe on lead acid?
 
Thank you every one. @StuM answer was what I was looking for. Thanks

Frankly 06-09-2016 16:14

Re: 125a Pull safe on lead acid?
 
I have 6 6V Sams Golf Cart Specials. Bow thruser draws 330 Amps (typically less than 30 sec), Microwave 125 Amps (less than 10 minutes), Toaster Oven (125 Amps 2 minutes on/ and off), Coffee Pot 60 Amps 10 minutes, batteries typically last 6 years.

100 Amp Balmar (more like 85 Amps), 50 Amp Shore Power Charger (Freedom 10), I don't see any problem. :wink:

Panacea2183 06-09-2016 16:17

Re: 125a Pull safe on lead acid?
 
Not a problem

svlamorocha 06-09-2016 16:28

Re: 125a Pull safe on lead acid?
 
Quote:

Originally Posted by StuM (Post 2207399)
With good batteries, pulling at C5, voltage should drop to about 12.1V at 100% SOC.
If you get down to about 50% SOC, the voltage is likely to be around 11.5V.

Nothing to be overly concerned about.

I confess my thinking is based on L16GAC Trojans (2x2 configuration) which may or may not behave the same. In my experience when owners try to keep charge rate above 60A (which requires PSOC cycling, ie staying away from full charge and ensuring some sulfation) the voltage sag is much higher than the curve says.

Moreover, the curve shows votage at the battery terminals. If you substract the voltage drop at high current in the segment of 12V wire that is shared by inverter and other 12V loads, you end up with chartplotters that give alarms, etc, fridges that do not like it, etc, every time you pull 150Ax12V from the inverter.

Sorry if this sounds negative. Once you have experienced lithium (with the right wiring) you can use the inverter for anyting and there is no going back!

deepthought 06-09-2016 16:58

Re: 125a Pull safe on lead acid?
 
Thanks for giving me some more lithium envy but until I can afford them I have to use what I have :)

@Frankly thanks nice to hear there is some one working with similar setup. But how long have you had your batteries so far?

StuM 06-09-2016 16:59

Re: 125a Pull safe on lead acid?
 
Quote:

Originally Posted by svlamorocha (Post 2207423)
I confess my thinking is based on L16GAC Trojans (2x2 configuration) which may or may not behave the same. In my experience when owners try to keep charge rate above 60A (which requires PSOC cycling, ie staying away from full charge and ensuring some sulfation) the voltage sag is much higher than the curve says.

Sorry, you've lost me here.

I wasn't discussing charge rate, I was discussing (and the graph showed) discharge rate (a function of bank size/amperage draw) v voltage drop.

That said, Amps for charging is largely a function of the size of battery bank. Quoting a single number like 60A is pointless without knowing a lot more about the system being charged.

And why would anyone deliberately only partially charge LA batteries?

Frankly 06-09-2016 17:32

Re: 125a Pull safe on lead acid?
 
I have owned Cbreeze 11 years. First set of 6 Sams GC batteries lasted 6 years, Second set were changed after 4 years, because I needed them in a different boat, a year on the third set. 4 are installed midships and 2 more in the keel space in the bow. All from Sams Club (flavor of the month). They are always connected in parallel (series sets) and are used to start the Yanmar. None were completely shot, I just rotate them (kind of a hand me down operation). Earlier years we did some extended (2 month) cruises, now we are pretty much weekenders (old age has set in, rigor mortis is next).

Frankly

deepthought 06-09-2016 17:36

Re: 125a Pull safe on lead acid?
 
@Frankly thanks for the info sounds good.


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