Thread: Normal battery to run fridge

Thanks again for all the replies and extra info. Once more, AULRO has resolved my concerns and I have learned more about batteries and my vehicle along the way.
Cheers, Woolly.

Originally Posted by drivesafe

Whereas, All-Rounders, which are a pretty good battery, but being a calcium/calcium battery, they do need a periodical high voltage charge to keep them in a fully charged state.

This is something MOST alternators just can not do.

Hi Tim, what voltage output is "periodical high voltage"? My puma religiously sat on 14.2-14.4V output. The LS engine going into the Puma is a newer style PWM controlled alternator that is regulated by the BCM based on whatever parameters defined by factory. However in my situation, being an engine conversion, i am running a module that permits me to set the duty cycle of the alternator, with max potential of 15.5V. Adjusting the duty cycle is not something i can do on the fly, so looking to preset the duty cycle output that is a balanced compromise that suits most situations.

Hi MLD, if you have a Calcium/Calcium battery, it would need a 15.5v charge, once a month, otherwise 14.4v or thereabouts would be fine for the rest of the time.

If you have an AGM battery, NEVER run higher than 14.7v at anytime.

The early model D4s actually had a good Cal/Cal charging setup, but you had to have it changed if you swapped out the Cal/Cal cranking battery for an AGM cranking battery.

Today everything is much simpler because just about every vehicle comes with an AGM cranking battery.

I would at least have a lithium starter pack with me, (I do) in case you leave a light on as well or something.
Seeing it is most probably an auto, it is darned hard to start them with a flat battery. A D2 TD5 will not start under about 11.5 volts .
Regards PhilipA

It's hard when you haven't tried things out. The answer "it depends".

Early fridges like the engel were small and very efficient because they had to be. People these days don't seem to worry about that and run big power hungry fridges and have big electrical systems.

My 40l Engel uses 2-3 Amps an hour. If I run the starlink which I would like to do (I mean you could switch it on and off as required) it's 2a an hour. Say you pull up at 4pm and drive out at 9am. .. that's 17 hours at 5a an hour. If you take 85A from a standard cranking battery there is not going to be any starting from it in the morning without help.

Things you could do is pick a small efficient fridge, and keep charging to while the car is running. Pick led lights and maybe handheld. Be conscious that you're going to have to drive every day or charge somehow or the fridge is going to flame out. Maybe you know someone who has a solar panel you could borrow?

Also be aware that even if a battery says it has 110 amps (say) it's not really very good for it to use more than half of it. Up until recently I had a Drivesafe SC80 (??) that linked the two batteries together (cranking and agm) down to a point. I used this for 20 years with my engel fridge. If moving every day no problems. If doing two days was a bit grim.

I've just replaced with a lithium battery and DCDC charger. $$$$$$....

Originally Posted by Captain_Rightfoot

Also be aware that even if a battery says it has 110 amps (say) it's not really very good for it to use more than half of it.

Hi Captain and sorry mate but this is pure advertising fiction, put out by companies trying to convince you that you get more power out of a 100Ah lithium battery than you can get out of a 100Ah lead acid battery, ( AGM or Wet Cell )

There is no such limitation of only using 50% of a lead acid battery and most lead acid battery manufacturers specifically state that their lead acid batteries, when used as auxiliary batteries, can be SAFELY discharged down to 20% SoC and many of the newer AGMs, like the SSB HVT range of batteries, can be safely discharged down to 0%.

Yet most lithium batteries are internally limited to only be discharged down to 20% and some are limited to just 25%.

So you are actually more likely to get more usable energy from a lead acid battery than you are for a lithium battery of the same Ah.

Originally Posted by drivesafe

Hi Captain and sorry mate but this is pure advertising fiction, put out by companies trying to convince you that you get more power out of a 100Ah lithium battery than you can get out of a 100Ah lead acid battery, ( AGM or Wet Cell )

There is no such limitation of only using 50% of a lead acid battery and most lead acid battery manufacturers specifically state that their lead acid batteries, when used as auxiliary batteries, can be SAFELY discharged down to 20% SoC and many of the newer AGMs, like the SSB HVT range of batteries, can be safely discharged down to 0%.

Yet most lithium batteries are internally limited to only be discharged down to 20% and some are limited to just 25%.

So you are actually more likely to get more usable energy from a lead acid battery than you are for a lithium battery of the same Ah.

Thanks! That's really interesting.

Victron say this for AGM. It does suggest big discharges are hard on them - but 400 cycles is a lot. My batteries die from age I suspect rather than use. The lithium battery I bought state 6000+ cycles at 80% DOD. Time literally will tell if they are as good as they say.

Rated capacity: 20 hr. discharge at 25?CFloat design life: 7-10 years at 20?C
Cycle design life:
400 cycles at 80% discharge
600 cycles at 50% discharge
1500 cycles at 30% discharge

https://www.victronenergy.com/upload...tteries-EN.pdf

Hi again Captain and the use of cycle rates, in my opinion, is nothing more than a scare tactic.

BUT you made a VERY IMPORTANT observation when you state that "your batteries die from age rather than from use"

Most people do not realise this as being the usual cause of the demise of a battery.

Cycle rates are really irrelevant and I'll give you an example of why I state this.

If you have a battery with a 200 cycle to 0% SoC life expectancy, then if you went camping EVERY weekend and EVERY weekend you discharged the battery down to 0% SoC, you will only get 4 years of use from than battery.

If you only went camping once a month, then you should get 16 years of use. NOT GOING TO HAPPEN.

I no longer make any reference to cycle rates when discussing battery life expectancy, whether it be for lead acid batteries or lithium batteries, for the above reason.