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Surfer62 said..

Paddles B'mere said..
@surfer62, what's the max current draw of the fridge? (look in the book) For your usage, I would not bother with solar and just charge with the alternator whilst driving, take a decent battery charger with you and whenever you're somewhere with power and not moving charge it all up properly. Check the alternator size/output for your car. You also need to make sure your battery size is adequate for the load/charging cycle. An AGM can be safely cycled at 80% of capacity, lead/acid about 50% and not affect long term battery life.

Awesome advice, I think fridge draws about 1 amp/hr, the agm is 120 ah, mq triton so I think the alternator pumps out 75 amps and 14.2 v at idle, the meter reads just under 14 v when on the road. cheers

If you are relying on an alternator for charging additional loads, you need to understand when it charges at its rated output.

A lot of typical alternators do not output their rated output until they are spinning quite fast, and at idle they don't provide the same output. Unless its a special alternator meant for that sort of use, which tend to be added to cop cars or ambulances. Bosch provide details about the current output for their alternators.

I run the oem alternator on my 100 series cruiser. By my battery monitors I am only receiving between 7 to 10ah to my 4 agm batteries (100ah each, 3 in camper trailer and 1 in vehicle) when cruising at highway speeds. An alternator upgrade was an option to keep my batteries charged. At that rate I would need to be driving everyday for at least 5hrs to balance my camping style. I run an 80l Engel fridge at 5deg and a 60L Waeco in freezer mode at -8deg. That with camp lights, water pumps, charging iPad, phones, cameras, drones,etc was using about 30 amps per day, in 30 to 35deg days. I expect the 60L fridge would use at least 10amp per day. I try not to draw my Agm batteries below 40%. What needs to be considered is your camping style. Do you plan to drive frequently in which case your alternator may be sufficient to meet your needs. If you plan to stay at a location for several days, either a solar system or a generator is a must. I carry both as i've Been caught out in overcast conditions which severely reduces the solar panels. There is a very good YouTube video by Rony Dahl which goes into battery management requirements with solar panels.

Heisenberg, you've done the maths on your setup and obviously set up something that works well. I cooked the oem alternator on my 105 recently so put the oversized one in to replace it as it wasn't much more money. I'll have to check the output curves to see its performance. We're not too high tech, biggest load is the nasty old early 90's model Engel

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Paddles B'mere said..
Heisenberg, you've done the maths on your setup and obviously set up something that works well. I cooked the oem alternator on my 105 recently so put the oversized one in to replace it as it wasn't much more money. I'll have to check the output curves to see its performance. We're not too high tech, biggest load is the nasty old early 90's model Engel

I would definitely be looking at upgrading the alternator when my 15 year old oem alternator dies. Another alternative is to add a dcdc charger which cost about $350. I've been told that can deliver a lot more amh from the standard alternator.

theres a lot of wrong in this thread, but cycling your battery past 70 halves and the 50 quarters the life.
A conventional altenator will only get you to 80% SOC. A dc/dc will give u that extra 20%. or solar.
I wouldnt change your altenator from factory. they are getting quite funky now . CHeaper to go dc/dc route.. You're not talking large banks
An engel 40l anly draws 2.7amps when on. A WAECO OR LARGER ENGEL 4.5 .on is compresser on. so maybe 2/3 that duty cycle (constantly on if on freeze.) engel runs a bit more than waeco has less heat removing power.

I was always led to believe by my peers that a lead acid discharge cycle could be up to 50% and an AGM or Gel could be up to 80% without adversely affecting battery life. I don't understand the "70 halves and 50 quarters" terminology, is that the discharge cycle? Correct, a conventional alternator regulator won't charge a battery as completely as a DC/DC charger, whether it be sourcing from your car's charging bus or from a solar panel (solar regulator is just a smarter DC/DC charger). And true, some more modern alternators have some very good battery charging "smarts" built in to them so will be hideously expensive to replace so don't replace/upgrade if your car has this as it won't be economically viable. However, if your usage allows, you can have a very workable system by simply having an oversized battery and using the car alternator (if adequately sized), especially if you own a dinosaur like a 105 Cruiser. You just use your "smart" (CTEK or similar) charger to top off your batteries when you get access to a 240VAC source somewhere. If I was installing a remote telemetry unit in a location without a grid power source and I absolutely wanted everything to last the longest possible time for maintenance reasons, then I'd install the "smart" electronics, or if I needed my system to stay alive in the one location for long periods of time I'd use solar panels and a good regulator/charger. It's horses for courses when it comes to the engineering myusernam, there's no point spending a squillion bucks if you don't really need to, ie it's not a critical power supply.

Mark,

I use a 105 Ah deep cycle Trojan battery. My 50 litre Waeco fridge draws 4 amps on a 25% duty cycle, so that's an average of 1 amp, meaning 24 Ah per day. Pretty sure the Engel would use a similar amount of power. I can do a 3-day weekend pretty comfortably.

You'd get away with connecting the solar cell when the battery is in a state of discharge but you wouldn't want to let it reach full charge. The risk with connecting the 21 volt solar cell is that it will continue to push a lot of current into the battery even when it reaches 100% charge. Your fridge is not going to see 21 volts, as the battery and charging current will pull that down a lot lower, as long as you disconnect the solar cell well before the battery reaches 100% charge.

Guessing that your solar cell puts out around 5 amps, connecting it a couple of hours a day would be safe.

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Paddles B'mere said..
I was always led to believe by my peers that a lead acid discharge cycle could be up to 50% and an AGM or Gel could be up to 80% without adversely affecting battery life..Every battery manufacture puts out a cycle life per depth of discharge chart. Look up yours I don't understand the "70 halves and 50 quarters" terminology, written in haste but I am talking discharge cycles . If you only cycle to 50% instead of 80% you will double life. Only discharge to 70% double it again. refer to graph. is that the discharge cycle? Correct, conventional alternator regulator won't charge a battery as completely as a DC/DC charger, whether it be sourcing from your car's charging bus or from a solar panel (solar regulator is just a smarter DC/DC charger no). And true, some more modern alternators have some very good battery charging "smarts" built in to them so will be hideously expensive to replace so don't replace/upgrade if your car has this as it won't be economically viable. no, many modern altenators shut of or do all sorts of wierd and wonderfull things., including turning off to reduce load. they are so integrated into your cars system its hard to change. However, if your usage allows, you can have a very workable system by simply having an oversized battery and using the car alternator (if adequately sized), especially if you own a dinosaur like a 105 Cruiser. You just use your "smart" (CTEK or similar) charger to top off your batteries when you get access to a 240VAC source somewhere. If I was installing a remote telemetry unit in a location without a grid power source and I absolutely wanted everything to last the longest possible time for maintenance reasons, then I'd install the "smart" electronics, or if I needed my system to stay alive in the one location for long periods of time I'd use solar panels and a good regulator/charger. It's horses for courses when it comes to the engineering myusernam, there's no point spending a squillion bucks if you don't really need to, ie it's not a critical power supply.your old cruiser altenator will only charge your agm to 80%. So already you have an 80AH batt instead of 100AH (example). You shouldnt cycle below 50% if at all possible. 70% better. So if you run 100AH you only have 30A Usable AH. Say you have a bit of a run to a Waeco battery that has an auto cutout at 11.8 volts (to protect battery 80% DOD) and you are starting at 80% or 12.6 volts. then you have some voltage drop - quite a bit probably if you dont know what you are doing or if you had to pay for cable and the run is long. Say half a volt at 5 amps. so now after you have run your car for half a day you only have 12.1 volts or 20 amp hours or a single days running out of your 100 AH agm battery. And you are discharging to the max you should greatly shortenening the life of your battery. Leave it in the car for two years and you can halve that performance. Graph below is for USA made agm twice the price as chinese. Chinese will give less cycles. See data sheet

Aftermarket altenator only good if contiuous duty rated with external smart regulator, then you have to worry about belts. Big $. Far easier in vehicle to use solar or DC/DC to achieve 100% charge.


Danfoss compressors use 4.5 amps running. Engel 40L 2.7amps. Biger engel same as danfoss. Engel has more frequent duty cycle. Say on 40 mins of every hour (when not opening or loading with hot stuff) instead of 30 for waeco (more cooling power) on freeze both will be on the whole time so 2.7 amps or 4.5 amps per hour. times that by number of hours between charge.
Solar panel should give 5 amps per hour for 5.5 hours per day tapering off fairly quickly either side. No shade at all. (have to park car in sun) not have stuff on roof casting a shadow

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQyH8_aTHNg90o341LguUoVnfx4HF-i-VMpiX_SxA6hIHxV5BsFkA

Wow, MUN, you could not be further from the truth about my peers. But if being adversarial towards me rather than helpful and constructive towards the guy asking about his battery setup is more your style when someone asks a question then you keep talking yourself up champ!

It's true, depth of discharge, completeness of charging cycle and number of discharge cycles affect battery life, you'll get no argument from me on that.

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Paddles B'mere said..
Wow, MUN, you could not be further from the truth about my peers. But if being adversarial towards me rather than helpful and constructive towards the guy asking about his battery setup is more your style when someone asks a question then you keep talking yourself up champ!

It's true, depth of discharge, completeness of charging cycle and number of discharge cycles affect battery life, you'll get no argument from me on that.

fair call. i edited out the sarcasm. sorry

Cut and paste all of it for the in document link (d not click)
windsolarhybridaustralia.x10.mx/light-aircraft-ppl-vh.html#vics

Dc dc 100% mint !!!

I've been down this road & will pick a Dcdc and agm 2nd battery for the cruisers over and over the dcdc makes a hell of a difference. Camper trailer fit outs.... you are into a whole new Kettle of fish. All depends on usage : plasma tv tumble drier washing machine. Coffee machine. Kettle / jug as the kiwis call them. Scented oil defuser. Make the vehicle to suit your needs plus some at the time. Carry a spare alternator if Heading off somewhere miles away and under stand your wiring. I've seen some dodgy **** done by so called auto sparkies. Choose a reputable shop that has that help you out feel. Not some clueless douche just trying to get there sales up.

ALWAYS REMEMBER YOUR EARTHS...
round or or flat a bad earth can lead to a disaster of a time. Heat shrink all fittings 2 extra minutes make it better then some of the crap that's on the road !!!

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THE PIN PULLER said..
Dc dc 100% mint !!!

With a lift kit like that job, how you going to fit that under a standard garage?! The missus and kid will need a ladder to climb up into the seats.

Mind you I reckon that could tow a caravan up north.